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Bibliography on: Topologically Associating Domains

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Robert J. Robbins is a biologist, an educator, a science administrator, a publisher, an information technologist, and an IT leader and manager who specializes in advancing biomedical knowledge and supporting education through the application of information technology. More About:  RJR | OUR TEAM | OUR SERVICES | THIS WEBSITE

RJR: Recommended Bibliography 04 Mar 2024 at 02:00 Created: 

Topologically Associating Domains

"Recent studies have shown that chromosomes in a range of organisms are compartmentalized in different types of chromatin domains. In mammals, chromosomes form compartments that are composed of smaller Topologically Associating Domains (TADs). TADs are thought to represent functional domains of gene regulation but much is still unknown about the mechanisms of their formation and how they exert their regulatory effect on embedded genes. Further, similar domains have been detected in other organisms, including flies, worms, fungi and bacteria. Although in all these cases these domains appear similar as detected by 3C-based methods, their biology appears to be quite distinct with differences in the protein complexes involved in their formation and differences in their internal organization." QUOTE FROM: Dekker Job and Heard Edith (2015), Structural and functional diversity of Topologically Associating Domains, FEBS Letters, 589, doi: 10.1016/j.febslet.2015.08.044

Created with PubMed® Query: ( "Topologically Associating Domains" OR "Topologically Associating Domain" ) NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)

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RevDate: 2024-03-03

Fraile A, Cebrián J, Thuissard-Vasallo I, et al (2024)

Coexistent HCN4 and GATA5 rare variants and Atrial Fibrillation in a large Spanish Family.

The Canadian journal of cardiology pii:S0828-282X(24)00189-2 [Epub ahead of print].

BACKGROUND: Familial association of atrial fibrillation (AF) can involve single gene variants related to known arrhythmogenic mechanisms; however, genome-wide association studies often disclose complex genetic variants in familial and non-familial AF, making it difficult to relate to known pathogenetic mechanisms.

METHODS: The finding of 4 siblings with AF led to studying 47 members of a family. Long-term Holter monitoring (298 hours average) ruled out silent AFWhole-exome sequencing was performed and variants shared by the index cases were filtered and prioritized according to current recommendations. HCN4 currents (IHCN4) were recorded in Chinese hamster ovary cells expressing human p.P1163H and/or native Hcn4 channels using the patch-clamp technique and topologically associated domain analysis of GATA5 variant carriers were performed.

RESULTS: The clinical study diagnosed 2 more AF cases. Five family members carried the heterozygous p.P1163H, HCN4 variant, 14 the intronic 20,61040536,G,A GATA5 rare variant, and 9 carried both variants (HCN4+GATA5). Five of the 6 AF cases (onset age ranging 33-70 years) carried both variants and one the GATA5 variant alone. Multivariate analysis showed that the presence of HCN4+GATA5 variants significantly and independently increased AF risk [OR=32.740 (1.812-591.408)] and not age, hypertension or overweight. Functional testing showed that IHcn4 generated by heterozygous p.P1163H were normal. Topologically associating domain analysis suggested that GATA5 could affect the expression of many genes, including those encoding microRNA-1.

CONCLUSION: The coincidence of two rare gene variants was independently associated with AF, but functional studies do not allow the postulation of the arrhythmogenic mechanism(s) involved.

RevDate: 2024-02-24

Torres DE, Kramer HM, Tracanna V, et al (2024)

Implications of the three-dimensional chromatin organization for genome evolution in a fungal plant pathogen.

Nature communications, 15(1):1701.

The spatial organization of eukaryotic genomes is linked to their biological functions, although it is not clear how this impacts the overall evolution of a genome. Here, we uncover the three-dimensional (3D) genome organization of the phytopathogen Verticillium dahliae, known to possess distinct genomic regions, designated adaptive genomic regions (AGRs), enriched in transposable elements and genes that mediate host infection. Short-range DNA interactions form clear topologically associating domains (TADs) with gene-rich boundaries that show reduced levels of gene expression and reduced genomic variation. Intriguingly, TADs are less clearly insulated in AGRs than in the core genome. At a global scale, the genome contains bipartite long-range interactions, particularly enriched for AGRs and more generally containing segmental duplications. Notably, the patterns observed for V. dahliae are also present in other Verticillium species. Thus, our analysis links 3D genome organization to evolutionary features conserved throughout the Verticillium genus.

RevDate: 2024-02-14

Patta I, Zand M, Lee L, et al (2024)

Nuclear morphology is shaped by loop-extrusion programs.

Nature [Epub ahead of print].

It is well established that neutrophils adopt malleable polymorphonuclear shapes to migrate through narrow interstitial tissue spaces[1-3]. However, how polymorphonuclear structures are assembled remains unknown[4]. Here we show that in neutrophil progenitors, halting loop extrusion-a motor-powered process that generates DNA loops by pulling in chromatin[5]-leads to the assembly of polymorphonuclear genomes. Specifically, we found that in mononuclear neutrophil progenitors, acute depletion of the loop-extrusion loading factor nipped-B-like protein (NIPBL) induced the assembly of horseshoe, banded, ringed and hypersegmented nuclear structures and led to a reduction in nuclear volume, mirroring what is observed during the differentiation of neutrophils. Depletion of NIPBL also induced cell-cycle arrest, activated a neutrophil-specific gene program and conditioned a loss of interactions across topologically associating domains to generate a chromatin architecture that resembled that of differentiated neutrophils. Removing NIPBL resulted in enrichment for mega-loops and interchromosomal hubs that contain genes associated with neutrophil-specific enhancer repertoires and an inflammatory gene program. On the basis of these observations, we propose that in neutrophil progenitors, loop-extrusion programs produce lineage-specific chromatin architectures that permit the packing of chromosomes into geometrically confined lobular structures. Our data also provide a blueprint for the assembly of polymorphonuclear structures, and point to the possibility of engineering de novo nuclear shapes to facilitate the migration of effector cells in densely populated tumorigenic environments.

RevDate: 2024-02-12

Liu S, Athreya A, Lao Z, et al (2024)

From Nucleosomes to Compartments: Physicochemical Interactions Underlying Chromatin Organization.

Annual review of biophysics [Epub ahead of print].

Chromatin organization plays a critical role in cellular function by regulating access to genetic information. However, understanding chromatin folding is challenging due to its complex, multiscale nature. Significant progress has been made in studying in vitro systems, uncovering the structure of individual nucleosomes and their arrays, and elucidating the role of physicochemical forces in stabilizing these structures. Additionally, remarkable advancements have been achieved in characterizing chromatin organization in vivo, particularly at the whole-chromosome level, revealing important features such as chromatin loops, topologically associating domains, and nuclear compartments. However, bridging the gap between in vitro and in vivo studies remains challenging. The resemblance between in vitro and in vivo chromatin conformations and the relevance of internucleosomal interactions for chromatin folding in vivo are subjects of debate. This article reviews experimental and computational studies conducted at various length scales, highlighting the significance of intrinsic interactions between nucleosomes and their roles in chromatin folding in vivo. Expected final online publication date for the Annual Review of Biophysics, Volume 53 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

RevDate: 2024-01-27

Nakamura T, Ueda J, Mizuno S, et al (2024)

Topologically associating domains define the impact of de novo promoter variants on autism spectrum disorder risk.

Cell genomics pii:S2666-979X(24)00001-6 [Epub ahead of print].

Whole-genome sequencing (WGS) studies of autism spectrum disorder (ASD) have demonstrated the roles of rare promoter de novo variants (DNVs). However, most promoter DNVs in ASD are not located immediately upstream of known ASD genes. In this study analyzing WGS data of 5,044 ASD probands, 4,095 unaffected siblings, and their parents, we show that promoter DNVs within topologically associating domains (TADs) containing ASD genes are significantly and specifically associated with ASD. An analysis considering TADs as functional units identified specific TADs enriched for promoter DNVs in ASD and indicated that common variants in these regions also confer ASD heritability. Experimental validation using human induced pluripotent stem cells (iPSCs) showed that likely deleterious promoter DNVs in ASD can influence multiple genes within the same TAD, resulting in overall dysregulation of ASD-associated genes. These results highlight the importance of TADs and gene-regulatory mechanisms in better understanding the genetic architecture of ASD.

RevDate: 2024-01-23

Murtaza G, Jain A, Hughes M, et al (2023)

A Comprehensive Evaluation of Generalizability of Deep Learning-Based Hi-C Resolution Improvement Methods.

Genes, 15(1): pii:genes15010054.

Hi-C is a widely used technique to study the 3D organization of the genome. Due to its high sequencing cost, most of the generated datasets are of a coarse resolution, which makes it impractical to study finer chromatin features such as Topologically Associating Domains (TADs) and chromatin loops. Multiple deep learning-based methods have recently been proposed to increase the resolution of these datasets by imputing Hi-C reads (typically called upscaling). However, the existing works evaluate these methods on either synthetically downsampled datasets, or a small subset of experimentally generated sparse Hi-C datasets, making it hard to establish their generalizability in the real-world use case. We present our framework-Hi-CY-that compares existing Hi-C resolution upscaling methods on seven experimentally generated low-resolution Hi-C datasets belonging to various levels of read sparsities originating from three cell lines on a comprehensive set of evaluation metrics. Hi-CY also includes four downstream analysis tasks, such as TAD and chromatin loops recall, to provide a thorough report on the generalizability of these methods. We observe that existing deep learning methods fail to generalize to experimentally generated sparse Hi-C datasets, showing a performance reduction of up to 57%. As a potential solution, we find that retraining deep learning-based methods with experimentally generated Hi-C datasets improves performance by up to 31%. More importantly, Hi-CY shows that even with retraining, the existing deep learning-based methods struggle to recover biological features such as chromatin loops and TADs when provided with sparse Hi-C datasets. Our study, through the Hi-CY framework, highlights the need for rigorous evaluation in the future. We identify specific avenues for improvements in the current deep learning-based Hi-C upscaling methods, including but not limited to using experimentally generated datasets for training.

RevDate: 2024-01-20

Wahl N, Espeso-Gil S, Chietera P, et al (2024)

SATB2 organizes the 3D genome architecture of cognition in cortical neurons.

Molecular cell pii:S1097-2765(23)01070-5 [Epub ahead of print].

The DNA-binding protein SATB2 is genetically linked to human intelligence. We studied its influence on the three-dimensional (3D) epigenome by mapping chromatin interactions and accessibility in control versus SATB2-deficient cortical neurons. We find that SATB2 affects the chromatin looping between enhancers and promoters of neuronal-activity-regulated genes, thus influencing their expression. It also alters A/B compartments, topologically associating domains, and frequently interacting regions. Genes linked to SATB2-dependent 3D genome changes are implicated in highly specialized neuronal functions and contribute to cognitive ability and risk for neuropsychiatric and neurodevelopmental disorders. Non-coding DNA regions with a SATB2-dependent structure are enriched for common variants associated with educational attainment, intelligence, and schizophrenia. Our data establish SATB2 as a cell-type-specific 3D genome modulator, which operates both independently and in cooperation with CCCTC-binding factor (CTCF) to set up the chromatin landscape of pyramidal neurons for cognitive processes.

RevDate: 2024-01-18

Hung TC, Kingsley DM, AN Boettiger (2024)

Boundary stacking interactions enable cross-TAD enhancer-promoter communication during limb development.

Nature genetics [Epub ahead of print].

Although promoters and their enhancers are frequently contained within a topologically associating domain (TAD), some developmentally important genes have their promoter and enhancers within different TADs. Hypotheses about molecular mechanisms enabling cross-TAD interactions remain to be assessed. To test these hypotheses, we used optical reconstruction of chromatin architecture to characterize the conformations of the Pitx1 locus on single chromosomes in developing mouse limbs. Our data support a model in which neighboring boundaries are stacked as a result of loop extrusion, bringing boundary-proximal cis-elements into contact. This stacking interaction also contributes to the appearance of architectural stripes in the population average maps. Through molecular dynamics simulations, we found that increasing boundary strengths facilitates the formation of the stacked boundary conformation, counter-intuitively facilitating border bypass. This work provides a revised view of the TAD borders' function, both facilitating and preventing cis-regulatory interactions, and introduces a framework to distinguish border-crossing from border-respecting enhancer-promoter pairs.

RevDate: 2024-01-13

Hua D, Gu M, Zhang X, et al (2024)

DiffDomain enables identification of structurally reorganized topologically associating domains.

Nature communications, 15(1):502.

Topologically associating domains (TADs) are critical structural units in three-dimensional genome organization of mammalian genome. Dynamic reorganizations of TADs between health and disease states are associated with essential genome functions. However, computational methods for identifying reorganized TADs are still in the early stages of development. Here, we present DiffDomain, an algorithm leveraging high-dimensional random matrix theory to identify structurally reorganized TADs using high-throughput chromosome conformation capture (Hi-C) contact maps. Method comparison using multiple real Hi-C datasets reveals that DiffDomain outperforms alternative methods for false positive rates, true positive rates, and identifying a new subtype of reorganized TADs. Applying DiffDomain to Hi-C data from different cell types and disease states demonstrates its biological relevance. Identified reorganized TADs are associated with structural variations and epigenomic changes such as changes in CTCF binding sites. By applying to a single-cell Hi-C data from mouse neuronal development, DiffDomain can identify reorganized TADs between cell types with reasonable reproducibility using pseudo-bulk Hi-C data from as few as 100 cells per condition. Moreover, DiffDomain reveals differential cell-to-population variability and heterogeneous cell-to-cell variability in TADs. Therefore, DiffDomain is a statistically sound method for better comparative analysis of TADs using both Hi-C and single-cell Hi-C data.

RevDate: 2024-01-12

Rosen J, Lee L, Abnousi A, et al (2023)

HPTAD: A computational method to identify topologically associating domains from HiChIP and PLAC-seq datasets.

Computational and structural biotechnology journal, 21:931-939.

High-throughput chromatin conformation capture technologies, such as Hi-C and Micro-C, have enabled genome-wide view of chromatin spatial organization. Most recently, Hi-C-derived enrichment-based technologies, including HiChIP and PLAC-seq, offer attractive alternatives due to their high signal-to-noise ratio and low cost. While a series of computational tools have been developed for Hi-C data, methods tailored for HiChIP and PLAC-seq data are still under development. Here we present HPTAD, a computational method to identify topologically associating domains (TADs) from HiChIP and PLAC-seq data. We performed comprehensive benchmark analysis to demonstrate its superior performance over existing TAD callers designed for Hi-C data. HPTAD is freely available at https://github.com/yunliUNC/HPTAD.

RevDate: 2024-01-11

Zhang M, Huang H, Li J, et al (2024)

ZNF143 deletion alters enhancer/promoter looping and CTCF/cohesin geometry.

Cell reports, 43(1):113663 pii:S2211-1247(23)01674-1 [Epub ahead of print].

The transcription factor ZNF143 contains a central domain of seven zinc fingers in a tandem array and is involved in 3D genome construction. However, the mechanism by which ZNF143 functions in chromatin looping remains unclear. Here, we show that ZNF143 directionally recognizes a diverse range of genomic sites directly within enhancers and promoters and is required for chromatin looping between these sites. In addition, ZNF143 is located between CTCF and cohesin at numerous CTCF sites, and ZNF143 removal narrows the space between CTCF and cohesin. Moreover, genetic deletion of ZNF143, in conjunction with acute CTCF degradation, reveals that ZNF143 and CTCF collaborate to regulate higher-order topological chromatin organization. Finally, CTCF depletion enlarges direct ZNF143 chromatin looping. Thus, ZNF143 is recruited by CTCF to the CTCF sites to regulate CTCF/cohesin configuration and TAD (topologically associating domain) formation, whereas directional recognition of genomic DNA motifs directly by ZNF143 itself regulates promoter activity via chromatin looping.

RevDate: 2024-01-11

Tang B, Wang X, He H, et al (2024)

Aging-disturbed FUS phase transition impairs hematopoietic stem cells by altering chromatin structure.

Blood, 143(2):124-138.

Aged hematopoietic stem cells (HSCs) exhibit compromised reconstitution capacity. The molecular mechanisms behind this phenomenon are not fully understood. Here, we observed that the expression of FUS is increased in aged HSCs, and enforced FUS recapitulates the phenotype of aged HSCs through arginine-glycine-glycine-mediated aberrant FUS phase transition. By using Fus-gfp mice, we observed that FUShigh HSCs exhibit compromised FUS mobility and resemble aged HSCs both functionally and transcriptionally. The percentage of FUShigh HSCs is increased upon physiological aging and replication stress, and FUSlow HSCs of aged mice exhibit youthful function. Mechanistically, FUShigh HSCs exhibit a different global chromatin organization compared with FUSlow HSCs, which is observed in aged HSCs. Many topologically associating domains (TADs) are merged in aged HSCs because of the compromised binding of CCCTC-binding factor with chromatin, which is invoked by aberrant FUS condensates. It is notable that the transcriptional alteration between FUShigh and FUSlow HSCs originates from the merged TADs and is enriched in HSC aging-related genes. Collectively, this study reveals for the first time that aberrant FUS mobility promotes HSC aging by altering chromatin structure.

RevDate: 2024-01-03

Li Y, Xiao P, Boadu F, et al (2023)

The counterpart congenital overgrowth syndromes Beckwith-Wiedemann Syndrome in human and large offspring syndrome in bovine involve alterations in DNA methylation, transcription, and chromatin configuration.

medRxiv : the preprint server for health sciences pii:2023.12.14.23299981.

Beckwith-Wiedemann Syndrome (BWS, OMIM #130650) is a congenital epigenetic disorder in humans which affects approximately 1 in 10,340 children. The incidence is likely an underestimation as the condition is usually recognized based on observable phenotypes at birth. BWS children have up to a 28% risk of developing tumors and currently, only 80% of patients can be corroborated molecularly (epimutations/variants). It is unknown how the subtypes of this condition are molecularly similar/dissimilar globally, therefore there is a need to deeply characterize the syndrome at the molecular level. Here we characterize the methylome, transcriptome and chromatin configuration of 18 BWS individuals together with the animal model of the condition, the bovine large offspring syndrome (LOS). Sex specific comparisons are performed for a subset of the BWS patients and LOS. Given that this epigenetic overgrowth syndrome has been characterized as a loss-of-imprinting condition, parental allele-specific comparisons were performed using the bovine animal model. In general, the differentially methylated regions (DMRs) detected in BWS and LOS showed significant enrichment for CTCF binding sites. Altered chromosome compartments in BWS and LOS were positively correlated with gene expression changes, and the promoters of differentially expressed genes showed significant enrichment for DMRs, differential topologically associating domains, and differential A/B compartments in some comparisons of BWS subtypes and LOS. We show shared regions of dysregulation between BWS and LOS, including several HOX gene clusters, and also demonstrate that altered DNA methylation differs between the clinically epigenetically identified BWS patients and those identified as having DNA variants (i.e. CDKN1C microdeletion). Lastly, we highlight additional genes and genomic regions that have the potential to serve as targets for biomarker development to improve current molecular methodologies. In summary, our results suggest that genome-wide alternation of chromosome architecture, which is partially caused by DNA methylation changes, also contribute to the development of BWS and LOS.

RevDate: 2024-01-03

Sun L, Zhou J, Xu X, et al (2024)

Mapping nucleosome-resolution chromatin organization and enhancer-promoter loops in plants using Micro-C-XL.

Nature communications, 15(1):35.

Although chromatin organizations in plants have been dissected at the scales of compartments and topologically associating domain (TAD)-like domains, there remains a gap in resolving fine-scale structures. Here, we use Micro-C-XL, a high-throughput chromosome conformation capture (Hi-C)-based technology that involves micrococcal nuclease (instead of restriction enzymes) and long cross-linkers, to dissect single nucleosome-resolution chromatin organization in Arabidopsis. Insulation analysis reveals more than 14,000 boundaries, which mostly include chromatin accessibility, epigenetic modifications, and transcription factors. Micro-C-XL reveals associations between RNA Pols and local chromatin organizations, suggesting that gene transcription substantially contributes to the establishment of local chromatin domains. By perturbing Pol II both genetically and chemically at the gene level, we confirm its function in regulating chromatin organization. Visible loops and stripes are assigned to super-enhancers and their targeted genes, thus providing direct insights for the identification and mechanistic analysis of distal CREs and their working modes in plants. We further investigate possible factors regulating these chromatin loops. Subsequently, we expand Micro-C-XL to soybean and rice. In summary, we use Micro-C-XL for analyses of plants, which reveal fine-scale chromatin organization and enhancer-promoter loops and provide insights regarding three-dimensional genomes in plants.

RevDate: 2023-12-22

Malachowski T, Chandradoss KR, Boya R, et al (2023)

Spatially coordinated heterochromatinization of long synaptic genes in fragile X syndrome.

Cell, 186(26):5840-5858.e36.

Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X chromosome in FXS patient-derived iPSCs, iPSC-derived neural progenitors, EBV-transformed lymphoblasts, and brain tissue with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication-stress-induced double-strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the mutation-length CGG to premutation length reverses H3K9me3 on the X chromosome and multiple autosomes, refolds TADs, and restores gene expression. H3K9me3 domains can also arise in normal-length iPSCs created with perturbations linked to genome instability, suggesting their relevance beyond FXS. Our results reveal Mb-scale heterochromatinization and trans interactions among loci susceptible to instability.

RevDate: 2023-12-21

Jessberger G, Várnai C, Stocsits RR, et al (2023)

Cohesin and CTCF do not assemble TADs in Xenopus sperm and male pronuclei.

Genome research pii:gr.277865.123 [Epub ahead of print].

Paternal genomes are compacted during spermiogenesis and decompacted following fertilization. These processes are fundamental for inheritance but incompletely understood. We analyzed these processes in the frog Xenopus laevis, whose sperm can be assembled into functional pronuclei in egg extracts in vitro. In such extracts, cohesin extrudes DNA into loops, but in vivo cohesin only assembles topologically associating domains (TADs) at the mid-blastula transition (MBT). Why cohesin assembles TADs only at this stage is unknown. We first analyzed genome architecture in frog sperm and compared it to human and mouse. Our results indicate that sperm genome organization is conserved between frogs and humans and occurs without formation of TADs. TADs can be detected in mouse sperm samples, as reported, but these structures might originate from somatic chromatin contaminations. We therefore discuss the possibility that the absence of TADs might be a general feature of vertebrate sperm. To analyze sperm genome remodeling upon fertilization, we reconstituted male pronuclei in Xenopus egg extracts. In pronuclei, chromatin compartmentalization increases, but cohesin does not accumulate at CTCF sites and assemble TADs. However, if pronuclei are formed in the presence of exogenous CTCF, CTCF binds to its consensus sites, and cohesin accumulates at these and forms short-range chromatin loops, which are preferentially anchored at CTCF's N terminus. These results indicate that TADs are only assembled at MBT because before this stage CTCF sites are not occupied and cohesin only forms short-range chromatin loops.

RevDate: 2023-12-15

Xiao M, Kondo S, Nomura M, et al (2023)

BRD9 determines the cell fate of hematopoietic stem cells by regulating chromatin state.

Nature communications, 14(1):8372.

ATP-dependent chromatin remodeling SWI/SNF complexes exist in three subcomplexes: canonical BAF (cBAF), polybromo BAF (PBAF), and a newly described non-canonical BAF (ncBAF). While cBAF and PBAF regulate fates of multiple cell types, roles for ncBAF in hematopoietic stem cells (HSCs) have not been investigated. Motivated by recent discovery of disrupted expression of BRD9, an essential component of ncBAF, in multiple cancers, including clonal hematopoietic disorders, we evaluate here the role of BRD9 in normal and malignant HSCs. BRD9 loss enhances chromatin accessibility, promoting myeloid lineage skewing while impairing B cell development. BRD9 significantly colocalizes with CTCF, whose chromatin recruitment is augmented by BRD9 loss, leading to altered chromatin state and expression of myeloid-related genes within intact topologically associating domains. These data uncover ncBAF as critical for cell fate specification in HSCs via three-dimensional regulation of gene expression and illuminate roles for ncBAF in normal and malignant hematopoiesis.

RevDate: 2023-12-13

Fok ET, Moorlag SJCFM, Negishi Y, et al (2023)

A chromatin-regulated biphasic circuit coordinates IL-1β-mediated inflammation.

Nature genetics [Epub ahead of print].

Inflammation is characterized by a biphasic cycle consisting initially of a proinflammatory phase that is subsequently resolved by anti-inflammatory processes. Interleukin-1β (IL-1β) is a master regulator of proinflammation and is encoded within the same topologically associating domain (TAD) as IL-37, which is an anti-inflammatory cytokine that opposes the function of IL-1β. Within this TAD, we identified a long noncoding RNA called AMANZI, which negatively regulates IL-1β expression and trained immunity through the induction of IL37 transcription. We found that the activation of IL37 occurs through the formation of a dynamic long-range chromatin contact that leads to the temporal delay of anti-inflammatory responses. The common variant rs16944 present in AMANZI augments this regulatory circuit, predisposing individuals to enhanced proinflammation or immunosuppression. Our work illuminates a chromatin-mediated biphasic circuit coordinating expression of IL-1β and IL-37, thereby regulating two functionally opposed states of inflammation from within a single TAD.

RevDate: 2023-12-12

Balasubramanian D, Borges Pinto P, Grasso A, et al (2023)

Enhancer-promoter interactions can form independently of genomic distance and be functional across TAD boundaries.

Nucleic acids research pii:7469969 [Epub ahead of print].

Topologically Associating Domains (TADs) have been suggested to facilitate and constrain enhancer-promoter interactions. However, the role of TAD boundaries in effectively restricting these interactions remains unclear. Here, we show that a significant proportion of enhancer-promoter interactions are established across TAD boundaries in Drosophila embryos, but that developmental genes are strikingly enriched in intra- but not inter-TAD interactions. We pursued this observation using the twist locus, a master regulator of mesoderm development, and systematically relocated one of its enhancers to various genomic locations. While this developmental gene can establish inter-TAD interactions with its enhancer, the functionality of these interactions remains limited, highlighting the existence of topological constraints. Furthermore, contrary to intra-TAD interactions, the formation of inter-TAD enhancer-promoter interactions is not solely driven by genomic distance, with distal interactions sometimes favored over proximal ones. These observations suggest that other general mechanisms must exist to establish and maintain specific enhancer-promoter interactions across large distances.

RevDate: 2023-12-11

Rossini R, Oshaghi M, Nekrasov M, et al (2023)

Multi-level 3D genome organization deteriorates during breast cancer progression.

bioRxiv : the preprint server for biology pii:2023.11.26.568711.

Breast cancer entails intricate alterations in genome organization and expression. However, how three-dimensional (3D) chromatin structure changes in the progression from a normal to a breast cancer malignant state remains unknown. To address this, we conducted an analysis combining Hi-C data with lamina-associated domains (LADs), epigenomic marks, and gene expression in an in vitro model of breast cancer progression. Our results reveal that while the fundamental properties of topologically associating domains (TADs) remain largely stable, significant changes occur in the organization of compartments and subcompartments. These changes are closely correlated with alterations in the expression of oncogenic genes. We also observe a restructuring of TAD-TAD interactions, coinciding with a loss of spatial compartmentalization and radial positioning of the 3D genome. Notably, we identify a previously unrecognized interchromosomal insertion event, wherein a locus on chromosome 8 housing the MYC oncogene is inserted into a highly active subcompartment on chromosome 10. This insertion leads to the formation of de novo enhancer contacts and activation of the oncogene, illustrating how structural variants can interact with the 3D genome to drive oncogenic states. In summary, our findings provide evidence for the degradation of genome organization at multiple scales during breast cancer progression revealing novel relationships between genome 3D structure and oncogenic processes.

RevDate: 2023-12-07

Long Y, Wendel JF, Zhang X, et al (2023)

Evolutionary insights into the organization of chromatin structure and landscape of transcriptional regulation in plants.

Trends in plant science pii:S1360-1385(23)00368-0 [Epub ahead of print].

Development of complex traits necessitates the functioning and coordination of intricate regulatory networks involving multiple genes. Understanding 3D chromatin structure can facilitate insight into the regulation of gene expression by regulatory elements. This potential, of visualizing the role of chromatin organization in the evolution and function of regulatory elements, remains largely unexplored. Here, we describe new perspectives that arise from the dual considerations of sequence variation of regulatory elements and chromatin structure, with a special focus on whole-genome doubling or polyploidy. We underscore the significance of hierarchical chromatin organization in gene regulation during evolution. In addition, we describe strategies for exploring chromatin organization in future investigations of regulatory evolution in plants, enabling insights into the evolutionary influence of regulatory elements on gene expression and, hence, phenotypes.

RevDate: 2023-12-04

Leeman-Neill RJ, Song D, Bizarro J, et al (2023)

Noncoding mutations cause super-enhancer retargeting resulting in protein synthesis dysregulation during B cell lymphoma progression.

Nature genetics [Epub ahead of print].

Whole-genome sequencing of longitudinal tumor pairs representing transformation of follicular lymphoma to high-grade B cell lymphoma with MYC and BCL2 rearrangements (double-hit lymphoma) identified coding and noncoding genomic alterations acquired during lymphoma progression. Many of these transformation-associated alterations recurrently and focally occur at topologically associating domain resident regulatory DNA elements, including H3K4me3 promoter marks located within H3K27ac super-enhancer clusters in B cell non-Hodgkin lymphoma. One region found to undergo recurrent alteration upon transformation overlaps a super-enhancer affecting the expression of the PAX5/ZCCHC7 gene pair. ZCCHC7 encodes a subunit of the Trf4/5-Air1/2-Mtr4 polyadenylation-like complex and demonstrated copy number gain, chromosomal translocation and enhancer retargeting-mediated transcriptional upregulation upon lymphoma transformation. Consequently, lymphoma cells demonstrate nucleolar dysregulation via altered noncoding 5.8S ribosomal RNA processing. We find that a noncoding mutation acquired during lymphoma progression affects noncoding rRNA processing, thereby rewiring protein synthesis leading to oncogenic changes in the lymphoma proteome.

RevDate: 2023-11-29

Llinàs-Arias P, Ensenyat-Mendez M, Íñiguez-Muñoz S, et al (2023)

Chromatin insulation orchestrates matrix metalloproteinase gene cluster expression reprogramming in aggressive breast cancer tumors.

Molecular cancer, 22(1):190.

BACKGROUND: Triple-negative breast cancer (TNBC) is an aggressive subtype that exhibits a high incidence of distant metastases and lacks targeted therapeutic options. Here we explored how the epigenome contributes to matrix metalloprotease (MMP) dysregulation impacting tumor invasion, which is the first step of the metastatic process.

METHODS: We combined RNA expression and chromatin interaction data to identify insulator elements potentially associated with MMP gene expression and invasion. We employed CRISPR/Cas9 to disrupt the CCCTC-Binding Factor (CTCF) binding site on an insulator element downstream of the MMP8 gene (IE8) in two TNBC cellular models. We characterized these models by combining Hi-C, ATAC-seq, and RNA-seq with functional experiments to determine invasive ability. The potential of our findings to predict the progression of ductal carcinoma in situ (DCIS), was tested in data from clinical specimens.

RESULTS: We explored the clinical relevance of an insulator element located within the Chr11q22.2 locus, downstream of the MMP8 gene (IE8). This regulatory element resulted in a topologically associating domain (TAD) boundary that isolated nine MMP genes into two anti-correlated expression clusters. This expression pattern was associated with worse relapse-free (HR = 1.57 [1.06 - 2.33]; p = 0.023) and overall (HR = 2.65 [1.31 - 5.37], p = 0.005) survival of TNBC patients. After CRISPR/Cas9-mediated disruption of IE8, cancer cells showed a switch in the MMP expression signature, specifically downregulating the pro-invasive MMP1 gene and upregulating the antitumorigenic MMP8 gene, resulting in reduced invasive ability and collagen degradation. We observed that the MMP expression pattern predicts DCIS that eventually progresses into invasive ductal carcinomas (AUC = 0.77, p < 0.01).

CONCLUSION: Our study demonstrates how the activation of an IE near the MMP8 gene determines the regional transcriptional regulation of MMP genes with opposing functional activity, ultimately influencing the invasive properties of aggressive forms of breast cancer.

RevDate: 2023-11-28

Jehangir M, Ahmad SF, Singchat W, et al (2023)

Hi-C sequencing unravels dynamic three-dimensional chromatin interactions in muntjac lineage: insights from chromosome fusions in Fea's muntjac genome.

Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology, 31(4):34.

Eukaryotes have varying numbers and structures of characteristic chromosomes across lineages or species. The evolutionary trajectory of species may have been affected by spontaneous genome rearrangements. Chromosome fusion drastically alters karyotypes. However, the mechanisms and consequences of chromosome fusions, particularly in muntjac species, are poorly understood. Recent research-based advancements in three-dimensional (3D) genomics, particularly high-throughput chromatin conformation capture (Hi-C) sequencing, have allowed for the identification of chromosome fusions and provided mechanistic insights into three muntjac species: Muntiacus muntjak, M. reevesi, and M. crinifrons. This study aimed to uncover potential genome rearrangement patterns in the threatened species Fea's muntjac (Muntiacus feae), which have not been previously examined for such characteristics. Deep Hi-C sequencing (31.42 × coverage) was performed to reveal the 3D chromatin architecture of the Fea's muntjac genome. Patterns of repeated chromosome fusions that were potentially mediated by high-abundance transposable elements were identified. Comparative Hi-C maps demonstrated linkage homology between the sex chromosomes in Fea's muntjac and autosomes in M. reevesi, indicating that fusions may have played a crucial role in the evolution of the sex chromosomes of the lineage. The species-level dynamics of topologically associated domains (TADs) suggest that TAD organization could be altered by differential chromosome interactions owing to repeated chromosome fusions. However, research on the effect of TADs on muntjac genome evolution is insufficient. This study generated Hi-C data for the Fea's muntjac, providing a genomic resource for future investigations of the evolutionary patterns of chromatin conformation at the chromosomal level.

RevDate: 2023-11-28

Zhao H, Lin Y, Lin E, et al (2023)

Genome folding principles revealed in condensin-depleted mitotic chromosomes.

bioRxiv : the preprint server for biology pii:2023.11.09.566494.

During mitosis, condensin activity interferes with interphase chromatin structures. Here, we generated condensin-free mitotic chromosomes to investigate genome folding principles. Co- depletion of condensin I and II, but neither alone, triggered mitotic chromosome compartmentalization in ways that differ from interphase. Two distinct euchromatic compartments, indistinguishable in interphase, rapidly emerged upon condensin loss with different interaction preferences and dependence on H3K27ac. Constitutive heterochromatin gradually self-aggregated and co-compartmentalized with the facultative heterochromatin, contrasting with their separation during interphase. While topologically associating domains (TADs) and CTCF/cohesin mediated structural loops remained undetectable, cis-regulatory element contacts became apparent, providing an explanation for their quick re-establishment during mitotic exit. HP1 proteins, which are thought to partition constitutive heterochromatin, were absent from mitotic chromosomes, suggesting, surprisingly, that constitutive heterochromatin can self-aggregate without HP1. Indeed, in cells traversing from M- to G1-phase in the combined absence of HP1α, HP1Π and HP1γ, re-established constitutive heterochromatin compartments normally. In sum, "clean-slate" condensin-deficient mitotic chromosomes illuminate mechanisms of genome compartmentalization not revealed in interphase cells.

RevDate: 2023-11-28

Singh AK, Walavalkar K, Tavernari D, et al (2023)

Cis-regulatory effect of HPV integration is constrained by host chromatin architecture in cervical cancers.

Molecular oncology [Epub ahead of print].

HPV infections are the primary drivers of cervical cancers, and often HPV DNA gets integrated into the host genome. Although the oncogenic impact of HPV encoded genes is relatively well known, the cis-regulatory effect of integrated HPV DNA on host chromatin structure and gene regulation remains less understood. We investigated genome-wide patterns of HPV integrations and associated host gene expression changes in the context of host chromatin states and TADs. HPV integrations were significantly enriched in active chromatin regions and depleted in inactive ones. Interestingly, regardless of chromatin state, genomic regions flanking HPV integrations showed transcriptional upregulation. Nevertheless, upregulation (both local and long-range) was mostly confined to TADs with integration, but not affecting adjacent TADs. Few TADs showed recurrent integrations associated with overexpression of oncogenes within them (e.g. MYC, PVT1, TP63 and ERBB2) regardless of proximity. Hi-C and 4C-seq analyses in cervical cancer cell line (HeLa) demonstrated chromatin looping interactions between integrated HPV and MYC/PVT1 regions (~500kb apart), leading to allele-specific overexpression. Based on these, we propose HPV integrations can trigger multimodal oncogenic activation to promote cancer progression.

RevDate: 2023-11-17

Siqueira E, Kim BH, Reser L, et al (2023)

Analysis of the interplay between MeCP2 and histone H1 during in vitro differentiation of human ReNCell neural progenitor cells.

Epigenetics, 18(1):2276425.

An immortalized neural cell line derived from the human ventral mesencephalon, called ReNCell, and its MeCP2 knock out were used. With it, we characterized the chromatin compositional transitions undergone during differentiation, with special emphasis on linker histones. While the WT cells displayed the development of dendrites and axons the KO cells did not, despite undergoing differentiation as monitored by NeuN. ReNCell expressed minimal amounts of histone H1.0 and their linker histone complement consisted mainly of histone H1.2, H1.4 and H1.5. The overall level of histone H1 exhibited a trend to increase during the differentiation of MeCP2 KO cells. The phosphorylation levels of histone H1 proteins decreased dramatically during ReNCell's cell differentiation independently of the presence of MeCP2. Immunofluorescence analysis showed that MeCP2 exhibits an extensive co-localization with linker histones. Interestingly, the average size of the nucleus decreased during differentiation but in the MeCP2 KO cells, the smaller size of the nuclei at the start of differentiation increased by almost 40% after differentiation by 8 days (8 DIV). In summary, our data provide a compelling perspective on the dynamic changes of H1 histones during neural differentiation, coupled with the intricate interplay between H1 variants and MeCP2.Abbreviations: ACN, acetonitrile; A230, absorbance at 230 nm; bFGF, basic fibroblast growth factor; CM, chicken erythrocyte histone marker; CNS, central nervous system; CRISPR, clustered regulated interspaced short palindromic repeatsDAPI, 4,'6-diaminidino-2-phenylindole; DIV, days in vitro (days after differentiation is induced); DMEM, Dulbecco's modified Eagle medium; EGF, epidermal growth factor; ESC, embryonic stem cell; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFAP, glial fibrillary acidic proteinHPLC, high-performance liquid chromatography; IF, immunofluorescence; iPSCs, induced pluripotent stem cells; MAP2, microtubule-associated protein 2; MBD, methyl-binding domain; MeCP2, methyl-CpG binding protein 2; MS, mass spectrometry; NCP, nucleosome core particle; NeuN, neuron nuclear antigen; NPC, neural progenitor cellPAGE, polyacrylamide gel electrophoresis; PBS, phosphate buffered saline; PFA, paraformaldehyde; PTM, posttranslational modification; RP-HPLC, reversed phase HPLC; ReNCells, ReNCells VM; RPLP0, ribosomal protein lateral stalk subunit P0; RT-qPCR, reverse transcription quantitative polymerase-chain reaction; RTT, Rett Syndrome; SDS, sodium dodecyl sulphate; TAD, topologically associating domain; Triple KO, triple knockout.

RevDate: 2023-11-14

He J, Yan A, Chen B, et al (2023)

3D genome remodeling and homologous pairing during meiotic prophase of mouse oogenesis and spermatogenesis.

Developmental cell pii:S1534-5807(23)00553-1 [Epub ahead of print].

During meiosis, the chromatin and transcriptome undergo prominent switches. Although recent studies have explored the genome reorganization during spermatogenesis, the chromatin remodeling in oogenesis and characteristics of homologous pairing remain largely elusive. We comprehensively compared chromatin structures and transcriptomes at successive substages of meiotic prophase in both female and male mice using low-input high-through chromosome conformation capture (Hi-C) and RNA sequencing (RNA-seq). Compartments and topologically associating domains (TADs) gradually disappeared and slowly recovered in both sexes. We found that homologs adopted different sex-conserved pairing strategies prior to and after the leptotene-to-zygotene transition, changing from long interspersed nuclear element (LINE)-enriched compartments B to short interspersed nuclear element (SINE)-enriched compartments A. We complemented marker genes and predicted the sex-specific meiotic sterile genes for each substage. This study provides valuable insights into the similarities and distinctions between sexes in chromosome architecture, homologous pairing, and transcriptome during meiotic prophase of both oogenesis and spermatogenesis.

RevDate: 2023-11-03

Zhu Y, Rosenfeld MG, Y Suh (2023)

Ultrafine mapping of chromosome conformation at hundred basepair resolution reveals regulatory genome architecture.

Proceedings of the National Academy of Sciences of the United States of America, 120(45):e2313285120.

The resolution limit of chromatin conformation capture methodologies (3Cs) has restrained their application in detection of fine-level chromatin structure mediated by cis-regulatory elements (CREs). Here, we report two 3C-derived methods, Tri-4C and Tri-HiC, which utilize multirestriction enzyme digestions for ultrafine mapping of targeted and genome-wide chromatin interaction, respectively, at up to one hundred basepair resolution. Tri-4C identified CRE loop interaction networks and quantitatively revealed their alterations underlying dynamic gene control. Tri-HiC uncovered global fine-gauge regulatory interaction networks, identifying >20-fold more enhancer:promoter (E:P) loops than in situ Hi-C. In addition to vastly improved identification of subkilobase-sized E:P loops, Tri-HiC also uncovered interaction stripes and contact domain insulation from promoters and enhancers, revealing their loop extrusion behaviors resembling the topologically associating domain boundaries. Tri-4C and Tri-HiC provide robust approaches to achieve the high-resolution interactome maps required for characterizing fine-gauge regulatory chromatin interactions in analysis of development, homeostasis, and disease.

RevDate: 2023-10-31

Chu X, J Wang (2023)

Quantifying the large-scale chromosome structural dynamics during the mitosis-to-G1 phase transition of cell cycle.

Open biology, 13(11):230175.

Cell cycle is known to be regulated by the underlying gene network. Chromosomes, which serve as the scaffold for gene expressions, undergo significant structural reorganizations during mitosis. Understanding the mechanism of the cell cycle from the chromosome structural perspective remains a grand challenge. In this study, we applied an integrated theoretical approach to investigate large-scale chromosome structural dynamics during the mitosis-to-G1 phase transition. We observed that the chromosome structural expansion and adaptation of the structural asphericity do not occur synchronously and attributed this behaviour to the unique unloading sequence of the two types of condensins. Furthermore, we observed that the coherent motions between the chromosomal loci are primarily enhanced within the topologically associating domains (TADs) as cells progress to the G1 phase, suggesting that TADs can be considered as both structural and dynamical units for organizing the three-dimensional chromosome. Our analysis also reveals that the quantified pathways of chromosome structural reorganization during the mitosis-to-G1 phase transition exhibit high stochasticity at the single-cell level and show nonlinear behaviours in changing TADs and contacts formed at the long-range regions. Our findings offer valuable insights into large-scale chromosome structural dynamics after mitosis.

RevDate: 2023-10-29

Gao GF, Li P, WJ Leonard (2023)

Co-localization of clusters of TCR-regulated genes with TAD rearrangements.

BMC genomics, 24(1):650.

BACKGROUND: Gene expression has long been known to be influenced by the relative proximity of DNA regulatory elements. Topologically associating domains (TADs) are self-interacting genomic regions involved in regulating gene expression by controlling the proximity of these elements. Prior studies of TADs and their biological roles have revealed correlations between TAD changes and cellular differentiation. Here, we used Hi-C and RNA-seq data to correlate TCR-induced changes in TAD structure and gene expression in human CD4[+] T cells.

RESULTS: We developed a pipeline, Differentially Expressed Gene Enrichment Finder (DEGEF), that identifies regions of differentially expressed gene enrichment. Using DEGEF, we found that TCR-regulated genes cluster non-uniformly across the genome and that these clusters preferentially localized in regions of TAD rearrangement. Interestingly, clusters of upregulated genes preferentially formed new Hi-C contacts compared to downregulated clusters, suggesting that TCR-activated CD4[+] T cells may regulate genes by changing stimulatory contacts rather than inhibitory contacts.

CONCLUSIONS: Our observations support a significant relationship between TAD rearrangements and changes in local gene expression. These findings indicate potentially important roles for TAD rearrangements in shaping their local regulatory environments and thus driving differential expression of nearby genes during CD4[+] T cell activation. Moreover, they provide new insights into global mechanisms that regulate gene expression.

RevDate: 2023-10-27

Song C, Zhang G, Mu X, et al (2023)

eRNAbase: a comprehensive database for decoding the regulatory eRNAs in human and mouse.

Nucleic acids research pii:7331015 [Epub ahead of print].

Enhancer RNAs (eRNAs) transcribed from distal active enhancers serve as key regulators in gene transcriptional regulation. The accumulation of eRNAs from multiple sequencing assays has led to an urgent need to comprehensively collect and process these data to illustrate the regulatory landscape of eRNAs. To address this need, we developed the eRNAbase (http://bio.liclab.net/eRNAbase/index.php) to store the massive available resources of human and mouse eRNAs and provide comprehensive annotation and analyses for eRNAs. The current version of eRNAbase cataloged 10 399 928 eRNAs from 1012 samples, including 858 human samples and 154 mouse samples. These eRNAs were first identified and uniformly processed from 14 eRNA-related experiment types manually collected from GEO/SRA and ENCODE. Importantly, the eRNAbase provides detailed and abundant (epi)genetic annotations in eRNA regions, such as super enhancers, enhancers, common single nucleotide polymorphisms, expression quantitative trait loci, transcription factor binding sites, CRISPR/Cas9 target sites, DNase I hypersensitivity sites, chromatin accessibility regions, methylation sites, chromatin interactions regions, topologically associating domains and RNA spatial interactions. Furthermore, the eRNAbase provides users with three novel analyses including eRNA-mediated pathway regulatory analysis, eRNA-based variation interpretation analysis and eRNA-mediated TF-target gene analysis. Hence, eRNAbase is a powerful platform to query, browse and visualize regulatory cues associated with eRNAs.

RevDate: 2023-10-27

Fischer EF, Pilarczyk G, M Hausmann (2023)

Microscopic Analysis of Heterochromatin, Euchromatin and Cohesin in Cancer Cell Models and under Anti-Cancer Treatment.

Current issues in molecular biology, 45(10):8152-8172 pii:cimb45100515.

The spatial organization of euchromatin (EC) and heterochromatin (HC) appears as a cell-type specific network, which seems to have an impact on gene regulation and cell fate. The spatial organization of cohesin should thus also be characteristic for a cell type since it is involved in a TAD (topologically associating domain) formation, and thus in gene regulation or DNA repair processes. Based on the previous hypotheses and results on the general importance of heterochromatin organization on genome functions in particular, the configurations of these organizational units (EC represented by H3K4me3-positive regions, HC represented by H3K9me3-positive regions, cohesins) are investigated in the cell nuclei of different cancer and non-cancerous cell types and under different anti-cancer treatments. Confocal microscopic images of the model cell systems were used and analyzed using analytical processes of quantification created in Fiji, an imaging tool box well established in different fields of science. Human fibroblasts, breast cancer and glioblastoma cells as well as murine embryonal terato-carcinoma cells were used as these cell models and compared according to the different parameters of spatial arrangements. In addition, proliferating, quiescent and from the quiescent state reactivated fibroblasts were analyzed. In some selected cases, the cells were treated with X-rays or azacitidine. Heterogeneous results were obtained by the analyses of the configurations of the three different organizational units: granulation and a loss of H3K4me3-positive regions (EC) occurred after irradiation with 4 Gy or azacitidine treatment. While fibroblasts responded to irradiation with an increase in cohesin and granulation, in breast cancer cells, it resulted in decreases in cohesin and changes in granulation. H3K9me3-positive regions (HC) in fibroblasts experienced increased granulation, whereas in breast cancer cells, the amount of such regions increased. After azacitidine treatment, murine stem cells showed losses of cohesin and granulation and an increase in the granulation of H3K9me3-positive regions. Fibroblasts that were irradiated with 2 Gy only showed irregularities in structural amounts and granulation. Quiescent fibroblasts contained less euchromatin-related H3K4me3-positive signals and cohesin levels as well as higher heterochromatin-related H3K9me3-positive signals than non-quiescent ones. In general, fibroblasts responded more intensely to X-ray irradiation than breast cancer cells. The results indicate the usefulness of model cell systems and show that, in general, characteristic differences initially existing in chromatin and cohesin organizations result in specific responses to anti-cancer treatment.

RevDate: 2023-10-26

Lee H, PJ Seo (2023)

Accessible gene borders establish a core structural unit for chromatin architecture in Arabidopsis.

Nucleic acids research, 51(19):10261-10277.

Three-dimensional (3D) chromatin structure is linked to transcriptional regulation in multicellular eukaryotes including plants. Taking advantage of high-resolution Hi-C (high-throughput chromatin conformation capture), we detected a small structural unit with 3D chromatin architecture in the Arabidopsis genome, which lacks topologically associating domains, and also in the genomes of tomato, maize, and Marchantia polymorpha. The 3D folding domain unit was usually established around an individual gene and was dependent on chromatin accessibility at the transcription start site (TSS) and transcription end site (TES). We also observed larger contact domains containing two or more neighboring genes, which were dependent on accessible border regions. Binding of transcription factors to accessible TSS/TES regions formed these gene domains. We successfully simulated these Hi-C contact maps via computational modeling using chromatin accessibility as input. Our results demonstrate that gene domains establish basic 3D chromatin architecture units that likely contribute to higher-order 3D genome folding in plants.

RevDate: 2023-10-26

Sreenivas P, Wang L, Wang M, et al (2023)

A SNAI2/CTCF Interaction is Required for NOTCH1 Expression in Rhabdomyosarcoma.

Molecular and cellular biology [Epub ahead of print].

Rhabdomyosarcoma (RMS) is a pediatric malignancy of the muscle with characteristics of cells blocked in differentiation. NOTCH1 is an oncogene that promotes self-renewal and blocks differentiation in the fusion negative-RMS sub-type. However, how NOTCH1 expression is transcriptionally maintained in tumors is unknown. Analyses of SNAI2 and CTCF chromatin binding and HiC analyses revealed a conserved SNAI2/CTCF overlapping peak downstream of the NOTCH1 locus marking a sub-topologically associating domain (TAD) boundary. Deletion of the SNAI2-CTCF peak showed that it is essential for NOTCH1 expression and viability of FN-RMS cells. Reintroducing constitutively activated NOTCH1-ΔE in cells with the SNAI2-CTCF peak deleted restored cell-viability. Ablation of SNAI2 using CRISPR/Cas9 reagents resulted in the loss of majority of RD and SMS-CTR FN-RMS cells. However, the few surviving clones that repopulate cultures have recovered NOTCH1. Cells that re-establish NOTCH1 expression after SNAI2 ablation are unable to differentiate robustly as SNAI2 shRNA knockdown cells; yet, SNAI2-ablated cells continued to be exquisitely sensitive to ionizing radiation. Thus, we have uncovered a novel mechanism by which SNAI2 and CTCF maintenance of a sub-TAD boundary promotes rather than represses NOTCH1 expression. Further, we demonstrate that SNAI2 suppression of apoptosis post-radiation is independent of SNAI2/NOTCH1 effects on self-renewal and differentiation.

RevDate: 2023-10-21

Messina O, Raynal F, Gurgo J, et al (2023)

3D chromatin interactions involving Drosophila insulators are infrequent but preferential and arise before TADs and transcription.

Nature communications, 14(1):6678.

In mammals, insulators contribute to the regulation of loop extrusion to organize chromatin into topologically associating domains. In Drosophila the role of insulators in 3D genome organization is, however, under current debate. Here, we addressed this question by combining bioinformatics analysis and multiplexed chromatin imaging. We describe a class of Drosophila insulators enriched at regions forming preferential chromatin interactions genome-wide. Notably, most of these 3D interactions do not involve TAD borders. Multiplexed imaging shows that these interactions occur infrequently, and only rarely involve multiple genomic regions coalescing together in space in single cells. Finally, we show that non-border preferential 3D interactions enriched in this class of insulators are present before TADs and transcription during Drosophila development. Our results are inconsistent with insulators forming stable hubs in single cells, and instead suggest that they fine-tune existing 3D chromatin interactions, providing an additional regulatory layer for transcriptional regulation.

RevDate: 2023-10-18

Arnould C, Rocher V, Saur F, et al (2023)

Chromatin compartmentalization regulates the response to DNA damage.

Nature [Epub ahead of print].

The DNA damage response is essential to safeguard genome integrity. Although the contribution of chromatin in DNA repair has been investigated[1,2], the contribution of chromosome folding to these processes remains unclear[3]. Here we report that, after the production of double-stranded breaks (DSBs) in mammalian cells, ATM drives the formation of a new chromatin compartment (D compartment) through the clustering of damaged topologically associating domains, decorated with γH2AX and 53BP1. This compartment forms by a mechanism that is consistent with polymer-polymer phase separation rather than liquid-liquid phase separation. The D compartment arises mostly in G1 phase, is independent of cohesin and is enhanced after pharmacological inhibition of DNA-dependent protein kinase (DNA-PK) or R-loop accumulation. Importantly, R-loop-enriched DNA-damage-responsive genes physically localize to the D compartment, and this contributes to their optimal activation, providing a function for DSB clustering in the DNA damage response. However, DSB-induced chromosome reorganization comes at the expense of an increased rate of translocations, also observed in cancer genomes. Overall, we characterize how DSB-induced compartmentalization orchestrates the DNA damage response and highlight the critical impact of chromosome architecture in genomic instability.

RevDate: 2023-10-16

Calandrelli R, Wen X, Charles Richard JL, et al (2023)

Genome-wide analysis of the interplay between chromatin-associated RNA and 3D genome organization in human cells.

Nature communications, 14(1):6519.

The interphase genome is dynamically organized in the nucleus and decorated with chromatin-associated RNA (caRNA). It remains unclear whether the genome architecture modulates the spatial distribution of caRNA and vice versa. Here, we generate a resource of genome-wide RNA-DNA and DNA-DNA contact maps in human cells. These maps reveal the chromosomal domains demarcated by locally transcribed RNA, hereafter termed RNA-defined chromosomal domains. Further, the spreading of caRNA is constrained by the boundaries of topologically associating domains (TADs), demonstrating the role of the 3D genome structure in modulating the spatial distribution of RNA. Conversely, stopping transcription or acute depletion of RNA induces thousands of chromatin loops genome-wide. Activation or suppression of the transcription of specific genes suppresses or creates chromatin loops straddling these genes. Deletion of a specific caRNA-producing genomic sequence promotes chromatin loops that straddle the interchromosomal target sequences of this caRNA. These data suggest a feedback loop where the 3D genome modulates the spatial distribution of RNA, which in turn affects the dynamic 3D genome organization.

RevDate: 2023-10-09

Bonaglia MC, Salvo E, Sironi M, et al (2023)

Case Report: Decrypting an interchromosomal insertion associated with Marfan's syndrome: how optical genome mapping emphasizes the morbid burden of copy-neutral variants.

Frontiers in genetics, 14:1244983.

Optical genome mapping (OGM), which allows analysis of ultra-high molecular weight (UHMW) DNA molecules, represents a response to the restriction created by short-read next-generation-sequencing, even in cases where the causative variant is a neutral copy-number-variant insensitive to quantitative investigations. This study aimed to provide a molecular diagnosis to a boy with Marfan syndrome (MFS) and intellectual disability (ID) carrying a de novo translocation involving chromosomes 3, 4, and 13 and a 1.7 Mb deletion at the breakpoint of chromosome 3. No FBN1 alteration explaining his Marfan phenotype was highlighted. UHMW gDNA was isolated from both the patient and his parents and processed using OGM. Genome assembly was followed by variant calling and annotation. Multiple strategies confirmed the results. The 3p deletion, which disrupted ROBO2, (MIM*602431) included three copy-neutral insertions. Two came from chromosome 13; the third contained 15q21.1, including the FBN1 from intron-45 onwards, thus explaining the MFS phenotype. We could not attribute the ID to a specific gene variant nor to the reshuffling of topologically associating domains (TADs). Our patient did not have vesicular reflux-2, as reported by missense alterations of ROBO2 (VUR2, MIM#610878), implying that reduced expression of all or some isoforms has a different effect than some of the point mutations. Indeed, the ROBO2 expression pattern and its role as an axon-guide suggests that its partial deletion is responsible for the patient's neurological phenotype. Conclusion: OGM testing 1) highlights copy-neutral variants that could remain invisible if no loss of heterozygosity is observed and 2) is mandatory before other molecular studies in the presence of any chromosomal rearrangement for an accurate genotype-phenotype relationship.

RevDate: 2023-10-04

Hristov BH, Noble WS, A Bertero (2023)

Systematic identification of inter-chromosomal interaction networks supports the existence of RNA factories.

bioRxiv : the preprint server for biology pii:2023.09.21.558852.

Most studies of genome organization have focused on intra-chromosomal (cis) contacts because they harbor key features such as DNA loops and topologically associating domains. Inter-chromosomal (trans) contacts have received much less attention, and tools for interrogating potential biologically relevant trans structures are lacking. Here, we develop a computational framework to identify sets of loci that jointly interact in trans from Hi-C data. This method, trans-C, initiates probabilistic random walks with restarts from a set of seed loci to traverse an input Hi-C contact network, thereby identifying sets of trans -contacting loci. We validate trans-C in three increasingly complex models of established trans contacts: the Plasmodium falciparum var genes, the mouse olfactory receptor "Greek islands", and the human RBM20 cardiac splicing factory. We then apply trans-C to systematically test the hypothesis that genes co-regulated by the same trans -acting element (i.e., a transcription or splicing factor) co-localize in three dimensions to form "RNA factories" that maximize the efficiency and accuracy of RNA biogenesis. We find that many loci with multiple binding sites of the same transcription factor interact with one another in trans , especially those bound by transcription factors with intrinsically disordered domains. Similarly, clustered binding of a subset of RNA binding proteins correlates with trans interaction of the encoding loci. These findings support the existence of trans interacting chromatin domains (TIDs) driven by RNA biogenesis. Trans-C provides an efficient computational framework for studying these and other types of trans interactions, empowering studies of a poorly understood aspect of genome architecture.

RevDate: 2023-10-03

Parodi L, Comeau ME, Georgakis MK, et al (2023)

Deep resequencing of the 1q22 locus in non-lobar intracerebral hemorrhage.

Annals of neurology [Epub ahead of print].

OBJECTIVE: Genome-wide association studies have identified 1q22 as a susceptibility locus for cerebral small vessel diseases (CSVDs), including non-lobar intracerebral hemorrhage (ICH) and lacunar stroke. In the present study we performed targeted high-depth sequencing of 1q22 in ICH cases and controls to further characterize this locus and prioritize potential causal mechanisms, which remain unknown.

METHODS: 95,000 base pairs spanning 1q22, including SEMA4A, SLC25A44 and PMF1/PMF1-BGLAP were sequenced in 1,055 spontaneous ICH cases (534 lobar and 521 non-lobar) and 1,078 controls. Firth regression and RIFT analysis were used to analyze common and rare variants, respectively. Chromatin interaction analyses were performed using Hi-C, ChIP-Seq and ChIA-PET databases. Multivariable Mendelian randomization (MVMR) assessed whether alterations in gene-specific expression relative to regionally co-expressed genes at 1q22 could be causally related to ICH risk.

RESULTS: Common and rare variant analyses prioritized variants in SEMA4A 5'-UTR and PMF1 intronic regions, overlapping with active promoter and enhancer regions based on ENCODE annotation. Hi-C data analysis determined that 1q22 is spatially organized in a single chromatin loop and that the genes therein belong to the same Topologically Associating Domain. ChIP-Seq and ChIA-PET data analysis highlighted the presence of long-range interactions between the SEMA4A-promoter and PMF1-enhancer regions prioritized by association testing. MVMR analyses demonstrated that PMF1 overexpression could be causally related to non-lobar ICH risk.

INTERPRETATION: Altered promoter-enhancer interactions leading to PMF1 overexpression, potentially dysregulating polyamine catabolism, could explain demonstrated associations with non-lobar ICH risk at 1q22, offering a potential new target for prevention of ICH and CSVD. This article is protected by copyright. All rights reserved.

RevDate: 2023-09-29

Kaur P, Lu X, Xu Q, et al (2023)

High-speed AFM imaging reveals DNA capture and loop extrusion dynamics by cohesin-NIPBL.

The Journal of biological chemistry pii:S0021-9258(23)02324-4 [Epub ahead of print].

3D chromatin organization plays a critical role in regulating gene expression, DNA replication, recombination, and repair. While initially discovered for its role in sister chromatid cohesion, emerging evidence suggests that the cohesin complex (SMC1, SMC3, RAD21, and SA1/SA2), facilitated by NIPBL, mediates topologically associating domains (TADs) and chromatin loops through DNA loop extrusion. However, information on how conformational changes of cohesin-NIPBL drive its loading onto DNA, initiation, and growth of DNA loops is still lacking. In this study, high-speed atomic force microscopy (HS-AFM) imaging reveals that cohesin-NIPBL captures DNA through arm extension, assisted by feet (shorter protrusions), and followed by transfer of DNA to its lower compartment (SMC heads, RAD21, SA1 and NIPBL). While binding at the lower compartment, arm extension leads to the capture of a second DNA segment and the initiation of a DNA loop that is independent of ATP hydrolysis. The feet are likely contributed by the C-terminal domains of SA1 and NIPBL and can transiently bind to DNA to facilitate the loading of the cohesin complex onto DNA. Furthermore, HS-AFM imaging reveals distinct forward and reverse DNA loop extrusion steps by cohesin-NIPBL. These results advance our understanding of cohesin by establishing direct experimental evidence for a multi-step DNA binding mechanism mediated by dynamic protein conformational changes.

RevDate: 2023-09-28

Yang J, Zhu X, Wang R, et al (2023)

Revisiting Assessment of Computational Methods for Hi-C Data Analysis.

International journal of molecular sciences, 24(18): pii:ijms241813814.

The performances of algorithms for Hi-C data preprocessing, the identification of topologically associating domains, and the detection of chromatin interactions and promoter-enhancer interactions have been mostly evaluated using semi-quantitative or synthetic data approaches, without utilizing the most recent methods, since 2017. In this study, we comprehensively evaluated 24 popular state-of-the-art methods for the complete end-to-end pipeline of Hi-C data analysis, using manually curated or experimentally validated benchmark datasets, including a CRISPR dataset for promoter-enhancer interaction validation. Our results indicate that, although no single method exhibited superior performance in all situations, HiC-Pro, DomainCaller, and Fit-Hi-C2 showed relatively balanced performances of most evaluation metrics for preprocessing, topologically associating domain identification, and chromatin interaction/promoter-enhancer interaction detection, respectively. The comprehensive comparison presented in this manuscript provides a reference for researchers to choose Hi-C analysis tools that best suit their needs.

RevDate: 2023-09-19

Nakato R, Sakata T, Wang J, et al (2023)

Context-dependent perturbations in chromatin folding and the transcriptome by cohesin and related factors.

Nature communications, 14(1):5647.

Cohesin regulates gene expression through context-specific chromatin folding mechanisms such as enhancer-promoter looping and topologically associating domain (TAD) formation by cooperating with factors such as cohesin loaders and the insulation factor CTCF. We developed a computational workflow to explore how three-dimensional (3D) structure and gene expression are regulated collectively or individually by cohesin and related factors. The main component is CustardPy, by which multi-omics datasets are compared systematically. To validate our methodology, we generated 3D genome, transcriptome, and epigenome data before and after depletion of cohesin and related factors and compared the effects of depletion. We observed diverse effects on the 3D genome and transcriptome, and gene expression changes were correlated with the splitting of TADs caused by cohesin loss. We also observed variations in long-range interactions across TADs, which correlated with their epigenomic states. These computational tools and datasets will be valuable for 3D genome and epigenome studies.

RevDate: 2023-09-19

He X, Huang X, Long Y, et al (2023)

Tcbf: A novel user-friendly tool for pan-3D genome analysis of topologically associating domain in eukaryotic organisms.

Bioinformatics (Oxford, England) pii:7277199 [Epub ahead of print].

SUMMARY: TAD boundaries are essential for organizing the chromatin spatial structure and regulating gene expression in eukaryotes. However, for large-scale pan-3D genome research, identifying conserved and specific TAD boundaries across different species or individuals is computationally challenging. Here, we present Tcbf, a rapid and powerful Python/R tool that integrates gene synteny blocks and homologous sequences to automatically detect conserved and specific TAD boundaries among multiple species, which can efficiently analyze huge genome datasets, greatly reduce the computational burden and enable pan-3D genome research.

Tcbf is implemented by Python/R and is available at https://github.com/TcbfGroup/Tcbf under the MIT license.

SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

RevDate: 2023-09-13

Oprescu SN, Baumann N, Chen X, et al (2023)

Sox11 is enriched in myogenic progenitors but dispensable for development and regeneration of the skeletal muscle.

Skeletal muscle, 13(1):15.

Transcription factors (TFs) play key roles in regulating differentiation and function of stem cells, including muscle satellite cells (MuSCs), a resident stem cell population responsible for postnatal regeneration of the skeletal muscle. Sox11 belongs to the Sry-related HMG-box (SOX) family of TFs that play diverse roles in stem cell behavior and tissue specification. Analysis of single-cell RNA-sequencing (scRNA-seq) datasets identify a specific enrichment of Sox11 mRNA in differentiating but not quiescent MuSCs. Consistent with the scRNA-seq data, Sox11 levels increase during differentiation of murine primary myoblasts in vitro. scRNA-seq data comparing muscle regeneration in young and old mice further demonstrate that Sox11 expression is reduced in aged MuSCs. Age-related decline of Sox11 expression is associated with reduced chromatin contacts within the topologically associating domains. Unexpectedly, Myod1[Cre]-driven deletion of Sox11 in embryonic myoblasts has no effects on muscle development and growth, resulting in apparently healthy muscles that regenerate normally. Pax7[CreER]- or Rosa26[CreER]- driven (MuSC-specific or global) deletion of Sox11 in adult mice similarly has no effects on MuSC differentiation or muscle regeneration. These results identify Sox11 as a novel myogenic differentiation marker with reduced expression in quiescent and aged MuSCs, but the specific function of Sox11 in myogenesis remains to be elucidated.

RevDate: 2023-09-12

Chang LH, Ghosh S, Papale A, et al (2023)

Multi-feature clustering of CTCF binding creates robustness for loop extrusion blocking and Topologically Associating Domain boundaries.

Nature communications, 14(1):5615.

Topologically Associating Domains (TADs) separate vertebrate genomes into insulated regulatory neighborhoods that focus genome-associated processes. TADs are formed by Cohesin-mediated loop extrusion, with many TAD boundaries consisting of clustered binding sites of the CTCF insulator protein. Here we determine how this clustering of CTCF binding contributes to the blocking of loop extrusion and the insulation between TADs. We identify enrichment of three features of CTCF binding at strong TAD boundaries, consisting of strongly bound and closely spaced CTCF binding peaks, with a further enrichment of DNA-binding motifs within these peaks. Using multi-contact Nano-C analysis in cells with normal and perturbed CTCF binding, we establish that individual CTCF binding sites contribute to the blocking of loop extrusion, but in an incomplete manner. When clustered, individual CTCF binding sites thus create a stepwise insulation between neighboring TADs. Based on these results, we propose a model whereby multiple instances of temporal loop extrusion blocking create strong insulation between TADs.

RevDate: 2023-08-22

Chen Y, Zhou T, Liao Z, et al (2023)

Hnrnpk is essential for embryonic limb bud development as a transcription activator and a collaborator of insulator protein Ctcf.

Cell death and differentiation [Epub ahead of print].

Proper development of the limb bud relies on the concordance of various signals, but its molecular mechanisms have not yet been fully illustrated. Here we report that heterogeneous nuclear ribonucleoprotein K (hnRNPK) is essential for limb bud development. Its ablation in the limb bud results in limbless forelimbs and severe deformities of the hindlimbs. In terms of mechanism, hnRNPK functions as a transcription activator for the vital genes involved in the three regulatory axes of limb bud development. Simultaneously, for the first time we elucidate that hnRNPK binds to and coordinates with the insulator protein CCCTC binding factor (CTCF) to maintain a three-dimensional chromatin architecture. Ablation of hnRNPK weakens the binding strength of CTCF to topologically associating domain (TAD) boundaries, then leading to the loose TADs, and decreased interactions between promoters and enhancers, and further decreased transcription of developmental genes. Our study establishes a fundamental and novel role of hnRNPK in regulating limb bud development.

RevDate: 2023-08-21

Agarwal A, Korsak S, Choudhury A, et al (2023)

The dynamic role of cohesin in maintaining human genome architecture.

BioEssays : news and reviews in molecular, cellular and developmental biology [Epub ahead of print].

Recent advances in genomic and imaging techniques have revealed the complex manner of organizing billions of base pairs of DNA necessary for maintaining their functionality and ensuring the proper expression of genetic information. The SMC proteins and cohesin complex primarily contribute to forming higher-order chromatin structures, such as chromosomal territories, compartments, topologically associating domains (TADs) and chromatin loops anchored by CCCTC-binding factor (CTCF) protein or other genome organizers. Cohesin plays a fundamental role in chromatin organization, gene expression and regulation. This review aims to describe the current understanding of the dynamic nature of the cohesin-DNA complex and its dependence on cohesin for genome maintenance. We discuss the current 3C technique and numerous bioinformatics pipelines used to comprehend structural genomics and epigenetics focusing on the analysis of Cohesin-centred interactions. We also incorporate our present comprehension of Loop Extrusion (LE) and insights from stochastic modelling.

RevDate: 2023-08-17

Yan T, Wang K, Feng K, et al (2023)

Remodeling of the 3D chromatin architecture in the marine microalga Nannochloropsis oceanica during lipid accumulation.

Biotechnology for biofuels and bioproducts, 16(1):129.

BACKGROUND: Genomic three-dimensional (3D) spatial organization plays a key role in shaping gene expression and associated chromatin modification, and it is highly sensitive to environmental stress conditions. In microalgae, exposure to nitrogen stress can drive lipid accumulation, yet the associated functional alterations in the spatial organization of the microalgal genome have yet to be effectively characterized.

RESULTS: Accordingly, the present study employed RNA-seq, Hi-C, and ChIP-seq approaches to explore the relationship between 3D chromosomal architecture and gene expression during lipid accumulation in the marine microalga Nannochloropsis oceanica in response to nitrogen deprivation (ND). These analyses revealed that ND resulted in various changes in chromosomal organization, including A/B compartment transitions, topologically associating domain (TAD) shifts, and the disruption of short-range interactions. Significantly higher levels of gene expression were evident in A compartments and TAD boundary regions relative to B compartments and TAD interior regions, consistent with observed histone modification enrichment in these areas. ND-induced differentially expressed genes (DEGs) were notably enriched in altered TAD-associated regions and regions exhibiting differential genomic contact. These DEGs were subjected to Gene Ontology (GO) term analyses that indicated they were enriched in the 'fatty acid metabolism', 'response to stress', 'carbon fixation' and 'photosynthesis' functional categories, in line with the ND treatment conditions used to conduct this study. These data indicate that Nannochloropsis cells exhibit a clear association between chromatin organization and transcriptional activity under nitrogen stress conditions. Pronounced and extensive histone modifications were evident in response to ND. Observed changes in chromatin architecture were linked to shifts in histone modifications and gene expression.

CONCLUSIONS: Overall, the reprogramming of many lipid metabolism-associated genes was evident under nitrogen stress conditions with respect to both histone modifications and chromosomal organization. Together these results revealed that higher-order chromatin architecture represents a new layer that can guide efforts to understand the transcriptional regulation of lipid metabolism in nitrogen-deprived microalgae.

RevDate: 2023-08-14

Tav C, Fournier É, Fournier M, et al (2023)

Glucocorticoid stimulation induces regionalized gene responses within topologically associating domains.

Frontiers in genetics, 14:1237092.

Transcription-factor binding to cis-regulatory regions regulates the gene expression program of a cell, but occupancy is often a poor predictor of the gene response. Here, we show that glucocorticoid stimulation led to the reorganization of transcriptional coregulators MED1 and BRD4 within topologically associating domains (TADs), resulting in active or repressive gene environments. Indeed, we observed a bias toward the activation or repression of a TAD when their activities were defined by the number of regions gaining and losing MED1 and BRD4 following dexamethasone (Dex) stimulation. Variations in Dex-responsive genes at the RNA levels were consistent with the redistribution of MED1 and BRD4 at the associated cis-regulatory regions. Interestingly, Dex-responsive genes without the differential recruitment of MED1 and BRD4 or binding by the glucocorticoid receptor were found within TADs, which gained or lost MED1 and BRD4, suggesting a role of the surrounding environment in gene regulation. However, the amplitude of the response of Dex-regulated genes was higher when the differential recruitment of the glucocorticoid receptor and transcriptional coregulators was observed, reaffirming the role of transcription factor-driven gene regulation and attributing a lesser role to the TAD environment. These results support a model where a signal-induced transcription factor induces a regionalized effect throughout the TAD, redefining the notion of direct and indirect effects of transcription factors on target genes.

RevDate: 2023-08-10
CmpDate: 2023-08-07

Wang Y, Guo Z, J Cheng (2023)

Single-cell Hi-C data enhancement with deep residual and generative adversarial networks.

Bioinformatics (Oxford, England), 39(8):.

MOTIVATION: The spatial genome organization of a eukaryotic cell is important for its function. The development of single-cell technologies for probing the 3D genome conformation, especially single-cell chromosome conformation capture techniques, has enabled us to understand genome function better than before. However, due to extreme sparsity and high noise associated with single-cell Hi-C data, it is still difficult to study genome structure and function using the HiC-data of one single cell.

RESULTS: In this work, we developed a deep learning method ScHiCEDRN based on deep residual networks and generative adversarial networks for the imputation and enhancement of Hi-C data of a single cell. In terms of both image evaluation and Hi-C reproducibility metrics, ScHiCEDRN outperforms the four deep learning methods (DeepHiC, HiCPlus, HiCSR, and Loopenhance) on enhancing the raw single-cell Hi-C data of human and Drosophila. The experiments also show that it can generate single-cell Hi-C data more suitable for identifying topologically associating domain boundaries and reconstructing 3D chromosome structures than the existing methods. Moreover, ScHiCEDRN's performance generalizes well across different single cells and cell types, and it can be applied to improving population Hi-C data.

The source code of ScHiCEDRN is available at the GitHub repository: https://github.com/BioinfoMachineLearning/ScHiCEDRN.

RevDate: 2023-06-13

Xiong K, Zhang R, J Ma (2023)

scGHOST: Identifying single-cell 3D genome subcompartments.

bioRxiv : the preprint server for biology.

New single-cell Hi-C (scHi-C) technologies enable probing of the genome-wide cell-to-cell variability in 3D genome organization from individual cells. Several computational methods have been developed to reveal single-cell 3D genome features based on scHi-C data, including A/B compartments, topologically-associating domains, and chromatin loops. However, no scHi-C analysis method currently exists for annotating single-cell subcompartments, which are crucial for providing a more refined view of large-scale chromosome spatial localization in single cells. Here, we present SCGHOST, a single-cell subcompartment annotation method based on graph embedding with constrained random walk sampling. Applications of SCGHOST to scHi-C data and single-cell 3D genome imaging data demonstrate the reliable identification of single-cell subcompartments and offer new insights into cell-to-cell variability of nuclear subcompartments. Using scHi-C data from the human prefrontal cortex, SCGHOST identifies cell type-specific subcompartments that are strongly connected to cell type-specific gene expression, suggesting the functional implications of single-cell subcompartments. Overall, SCGHOST is an effective new method for single-cell 3D genome subcompartment annotation based on scHi-C data for a broad range of biological contexts.

RevDate: 2023-07-01
CmpDate: 2023-04-25

Okonechnikov K, Camgöz A, Chapman O, et al (2023)

3D genome mapping identifies subgroup-specific chromosome conformations and tumor-dependency genes in ependymoma.

Nature communications, 14(1):2300.

Ependymoma is a tumor of the brain or spinal cord. The two most common and aggressive molecular groups of ependymoma are the supratentorial ZFTA-fusion associated and the posterior fossa ependymoma group A. In both groups, tumors occur mainly in young children and frequently recur after treatment. Although molecular mechanisms underlying these diseases have recently been uncovered, they remain difficult to target and innovative therapeutic approaches are urgently needed. Here, we use genome-wide chromosome conformation capture (Hi-C), complemented with CTCF and H3K27ac ChIP-seq, as well as gene expression and DNA methylation analysis in primary and relapsed ependymoma tumors, to identify chromosomal conformations and regulatory mechanisms associated with aberrant gene expression. In particular, we observe the formation of new topologically associating domains ('neo-TADs') caused by structural variants, group-specific 3D chromatin loops, and the replacement of CTCF insulators by DNA hyper-methylation. Through inhibition experiments, we validate that genes implicated by these 3D genome conformations are essential for the survival of patient-derived ependymoma models in a group-specific manner. Thus, this study extends our ability to reveal tumor-dependency genes by 3D genome conformations even in tumors that lack targetable genetic alterations.

RevDate: 2023-04-12
CmpDate: 2023-04-12

Sabaté T, Lelandais B, Bertrand E, et al (2023)

Polymer simulations guide the detection and quantification of chromatin loop extrusion by imaging.

Nucleic acids research, 51(6):2614-2632.

Genome-wide chromosome conformation capture (Hi-C) has revealed the organization of chromatin into topologically associating domains (TADs) and loops, which are thought to help regulate genome functions. TADs and loops are understood as the result of DNA extrusion mediated by the cohesin complex. However, despite recent efforts, direct visualization and quantification of this process in single cells remains an open challenge. Here, we use polymer simulations and dedicated analysis methods to explore if, and under which conditions, DNA loop extrusion can be detected and quantitatively characterized by imaging pairs of fluorescently labeled loci located near loop or TAD anchors in fixed or living cells. We find that under realistic conditions, extrusion can be detected and the frequency of loop formation can be quantified from fixed cell images alone, while the lifetime of loops and the speed of extrusion can be estimated from dynamic live-cell data. Our delineation of appropriate imaging conditions and the proposed analytical methods lay the groundwork for a systematic quantitative characterization of loop extrusion in fixed or living cells.

RevDate: 2023-08-09

Lyu J, C Chen (2023)

LAST-seq: single-cell RNA sequencing by direct amplification of single-stranded RNA without prior reverse transcription and second-strand synthesis.

Genome biology, 24(1):184.

Existing single-cell RNA sequencing (scRNA-seq) methods rely on reverse transcription (RT) and second-strand synthesis (SSS) to convert single-stranded RNA into double-stranded DNA prior to amplification, with the limited RT/SSS efficiency compromising RNA detectability. Here, we develop a new scRNA-seq method, Linearly Amplified Single-stranded-RNA-derived Transcriptome sequencing (LAST-seq), which directly amplifies the original single-stranded RNA molecules without prior RT/SSS. LAST-seq offers a high single-molecule capture efficiency and a low level of technical noise for single-cell transcriptome analyses. Using LAST-seq, we characterize transcriptional bursting kinetics in human cells, revealing a role of topologically associating domains in transcription regulation.

RevDate: 2023-08-07

Deng L, Zhou Q, Zhou J, et al (2023)

3D organization of regulatory elements for transcriptional regulation in Arabidopsis.

Genome biology, 24(1):181.

BACKGROUND: Although spatial organization of compartments and topologically associating domains at large scale is relatively well studied, the spatial organization of regulatory elements at fine scale is poorly understood in plants.

RESULTS: Here we perform high-resolution chromatin interaction analysis using paired-end tag sequencing approach. We map chromatin interactions tethered with RNA polymerase II and associated with heterochromatic, transcriptionally active, and Polycomb-repressive histone modifications in Arabidopsis. Analysis of the regulatory repertoire shows that distal active cis-regulatory elements are linked to their target genes through long-range chromatin interactions with increased expression of the target genes, while poised cis-regulatory elements are linked to their target genes through long-range chromatin interactions with depressed expression of the target genes. Furthermore, we demonstrate that transcription factor MYC2 is critical for chromatin spatial organization, and propose that MYC2 occupancy and MYC2-mediated chromatin interactions coordinately facilitate transcription within the framework of 3D chromatin architecture. Analysis of functionally related gene-defined chromatin connectivity networks reveals that genes implicated in flowering-time control are functionally compartmentalized into separate subdomains via their spatial activity in the leaf or shoot apical meristem, linking active mark- or Polycomb-repressive mark-associated chromatin conformation to coordinated gene expression.

CONCLUSION: The results reveal that the regulation of gene transcription in Arabidopsis is not only by linear juxtaposition, but also by long-range chromatin interactions. Our study uncovers the fine scale genome organization of Arabidopsis and the potential roles of such organization in orchestrating transcription and development.

RevDate: 2023-08-03

Tettey TT, Rinaldi L, GL Hager (2023)

Long-range gene regulation in hormone-dependent cancer.

Nature reviews. Cancer [Epub ahead of print].

The human genome is organized into multiple structural layers, ranging from chromosome territories to progressively smaller substructures, such as topologically associating domains (TADs) and chromatin loops. These substructures, collectively referred to as long-range chromatin interactions (LRIs), have a significant role in regulating gene expression. TADs are regions of the genome that harbour groups of genes and regulatory elements that frequently interact with each other and are insulated from other regions, thereby preventing widespread uncontrolled DNA contacts. Chromatin loops formed within TADs through enhancer and promoter interactions are elastic, allowing transcriptional heterogeneity and stochasticity. Over the past decade, it has become evident that the 3D genome structure, also referred to as the chromatin architecture, is central to many transcriptional cellular decisions. In this Review, we delve into the intricate relationship between steroid receptors and LRIs, discussing how steroid receptors interact with and modulate these chromatin interactions. Genetic alterations in the many processes involved in organizing the nuclear architecture are often associated with the development of hormone-dependent cancers. A better understanding of the interplay between architectural proteins and hormone regulatory networks can ultimately be exploited to develop improved approaches for cancer treatment.

RevDate: 2023-08-03

Mohana G, Dorier J, Li X, et al (2023)

Chromosome-level organization of the regulatory genome in the Drosophila nervous system.

Cell pii:S0092-8674(23)00741-9 [Epub ahead of print].

Previous studies have identified topologically associating domains (TADs) as basic units of genome organization. We present evidence of a previously unreported level of genome folding, where distant TAD pairs, megabases apart, interact to form meta-domains. Within meta-domains, gene promoters and structural intergenic elements present in distant TADs are specifically paired. The associated genes encode neuronal determinants, including those engaged in axonal guidance and adhesion. These long-range associations occur in a large fraction of neurons but support transcription in only a subset of neurons. Meta-domains are formed by diverse transcription factors that are able to pair over long and flexible distances. We present evidence that two such factors, GAF and CTCF, play direct roles in this process. The relative simplicity of higher-order meta-domain interactions in Drosophila, compared with those previously described in mammals, allowed the demonstration that genomes can fold into highly specialized cell-type-specific scaffolds that enable megabase-scale regulatory associations.

RevDate: 2023-07-30

Oka M, Otani M, Miyamoto Y, et al (2023)

Phase-separated nuclear bodies of nucleoporin fusions promote condensation of MLL1/CRM1 and rearrangement of 3D genome structure.

Cell reports, 42(8):112884 pii:S2211-1247(23)00895-1 [Epub ahead of print].

NUP98 and NUP214 form chimeric fusion proteins that assemble into phase-separated nuclear bodies containing CRM1, a nuclear export receptor. However, these nuclear bodies' function in controlling gene expression remains elusive. Here, we demonstrate that the nuclear bodies of NUP98::HOXA9 and SET::NUP214 promote the condensation of mixed lineage leukemia 1 (MLL1), a histone methyltransferase essential for the maintenance of HOX gene expression. These nuclear bodies are robustly associated with MLL1/CRM1 and co-localized on chromatin. Furthermore, whole-genome chromatin-conformation capture analysis reveals that NUP98::HOXA9 induces a drastic alteration in high-order genome structure at target regions concomitant with the generation of chromatin loops and/or rearrangement of topologically associating domains in a phase-separation-dependent manner. Collectively, these results show that the phase-separated nuclear bodies of nucleoporin fusion proteins can enhance the activation of target genes by promoting the condensation of MLL1/CRM1 and rearrangement of the 3D genome structure.

RevDate: 2023-07-21

Liu T, Z Wang (2023)

HiC4D: forecasting spatiotemporal Hi-C data with residual ConvLSTM.

Briefings in bioinformatics pii:7227144 [Epub ahead of print].

The Hi-C experiments have been extensively used for the studies of genomic structures. In the last few years, spatiotemporal Hi-C has largely contributed to the investigation of genome dynamic reorganization. However, computationally modeling and forecasting spatiotemporal Hi-C data still have not been seen in the literature. We present HiC4D for dealing with the problem of forecasting spatiotemporal Hi-C data. We designed and benchmarked a novel network and named it residual ConvLSTM (ResConvLSTM), which is a combination of residual network and convolutional long short-term memory (ConvLSTM). We evaluated our new ResConvLSTM networks and compared them with the other five methods, including a naïve network (NaiveNet) that we designed as a baseline method and four outstanding video-prediction methods from the literature: ConvLSTM, spatiotemporal LSTM (ST-LSTM), self-attention LSTM (SA-LSTM) and simple video prediction (SimVP). We used eight different spatiotemporal Hi-C datasets for the blind test, including two from mouse embryogenesis, one from somatic cell nuclear transfer (SCNT) embryos, three embryogenesis datasets from different species and two non-embryogenesis datasets. Our evaluation results indicate that our ResConvLSTM networks almost always outperform the other methods on the eight blind-test datasets in terms of accurately predicting the Hi-C contact matrices at future time-steps. Our benchmarks also indicate that all of the methods that we benchmarked can successfully recover the boundaries of topologically associating domains called on the experimental Hi-C contact matrices. Taken together, our benchmarks suggest that HiC4D is an effective tool for predicting spatiotemporal Hi-C data. HiC4D is publicly available at both http://dna.cs.miami.edu/HiC4D/ and https://github.com/zwang-bioinformatics/HiC4D/.

RevDate: 2023-07-19

Senapati S, Irshad IU, Sharma AK, et al (2023)

Fundamental insights into the correlation between chromosome configuration and transcription.

Physical biology [Epub ahead of print].

Eukaryotic chromosomes exhibit a hierarchical organization that spans a spectrum of length scales, ranging from sub-regions known as loops, which typically comprise hundreds of base pairs, to much larger chromosome territories that can encompass a few mega base pairs. Chromosome conformation capture experiments that involve high-throughput sequencing methods combined with microscopy techniques have enabled a new understanding of inter- and intra-chromosomal interactions with unprecedented details. This information also provides mechanistic insights on the relationship between genome architecture and gene expression. In this article, we review the recent findings on three-dimensional interactions among chromosomes at the compartment, topologically associating domain (TAD), and loop levels and the impact of these interactions on the transcription process. We also discuss current understanding of various biophysical processes involved in multi-layer structural organization of chromosomes. Then, we discuss the relationships between gene expression and genome structure from perturbative genome-wide association studies. Furthermore, for a better understanding of how chromosome architecture and function are linked, we emphasize the role of epigenetic modifications in the regulation of gene expression. Such an understanding of the relationship between genome architecture and gene expression can provide a new perspective on the range of potential future discoveries and therapeutic research. .

RevDate: 2023-07-18

Goudarzi S, Pagadala M, Klie A, et al (2023)

Epigenetic Germline Variants Predict Cancer Prognosis and Risk and Distribute Uniquely in Topologically Associating Domains.

bioRxiv : the preprint server for biology pii:2023.07.04.547722.

Cancer is a highly heterogeneous disease caused by genetic and epigenetic alterations in normal cells. A recent study uncovered methylation quantitative trait loci (meQTLs) associated with different levels of local DNA methylation in cancers. Here, we investigated whether the distribution of cancer meQTLs reflected functional organization of the genome in the form of chromatin topologically associated domains (TADs), and evaluated whether cancer meQTLs near known driver genes have the potential to influence cancer risk or progression. At TAD boundaries, we observed differences in the distribution of meQTLs when one or both of the adjacent TADs was transcriptionally active, with higher densities near inactive TADs. Furthermore, we found differences in cancer meQTL distributions in active versus inactive TADs and observed an enrichment of meQTLs in active TADs near tumor suppressors, whereas there was a depletion of such meQTLs near oncogenes. Several meQTLs were associated with cancer risk in the UKBioBank, and we were able to reproduce breast cancer risk associations in the DRIVE cohort. Survival analysis in TCGA implicated a number of meQTLs in 13 tumor types. In 10 of these, polygenic meQTL scores were associated with increased hazard in a CoxPH analysis. Risk and survival-associated meQTLs tended to affect cancer genes involved in DNA damage repair and cellular adhesion and reproduced cancer-specific associations reported in prior literature. In summary, this study provides evidence that genetic variants that influence local DNA methylation are affected by chromatin structure and can impact tumor evolution.

RevDate: 2023-07-15

Kim K, Kim M, Lee AJ, et al (2023)

Spatial and clonality-resolved 3D cancer genome alterations reveal enhancer-hijacking as a potential prognostic marker for colorectal cancer.

Cell reports, 42(7):112778 pii:S2211-1247(23)00789-1 [Epub ahead of print].

The regulatory effect of non-coding large-scale structural variations (SVs) on proto-oncogene activation remains unclear. This study investigated SV-mediated gene dysregulation by profiling 3D cancer genome maps from 40 patients with colorectal cancer (CRC). We developed a machine learning-based method for spatial characterization of the altered 3D cancer genome. This revealed a frequent establishment of "de novo chromatin contacts" that can span multiple topologically associating domains (TADs) in addition to the canonical TAD fusion/shuffle model. Using this information, we precisely identified super-enhancer (SE)-hijacking and its clonal characteristics. Clonal SE-hijacking genes, such as TOP2B, are recurrently associated with cell-cycle/DNA-processing functions, which can potentially be used as CRC prognostic markers. Oncogene activation and increased drug resistance due to SE-hijacking were validated by reconstructing the patient's SV using CRISPR-Cas9. Collectively, the spatial and clonality-resolved analysis of the 3D cancer genome reveals regulatory principles of large-scale SVs in oncogene activation and their clinical implications.

RevDate: 2023-07-14

Lee EG, Leong L, Chen S, et al (2023)

APOE Locus-Associated Mitochondrial Function and Its Implication in Alzheimer's Disease and Aging.

International journal of molecular sciences, 24(13): pii:ijms241310440.

The Apolipoprotein E (APOE) locus has garnered significant clinical interest because of its association with Alzheimer's disease (AD) and longevity. This genetic association appears across multiple genes in the APOE locus. Despite the apparent differences between AD and longevity, both conditions share a commonality of aging-related changes in mitochondrial function. This commonality is likely due to accumulative biological effects partly exerted by the APOE locus. In this study, we investigated changes in mitochondrial structure/function-related markers using oxidative stress-induced human cellular models and postmortem brains (PMBs) from individuals with AD and normal controls. Our results reveal a range of expressional alterations, either upregulated or downregulated, in these genes in response to oxidative stress. In contrast, we consistently observed an upregulation of multiple APOE locus genes in all cellular models and AD PMBs. Additionally, the effects of AD status on mitochondrial DNA copy number (mtDNA CN) varied depending on APOE genotype. Our findings imply a potential coregulation of APOE locus genes possibly occurring within the same topologically associating domain (TAD) of the 3D chromosome conformation. The coordinated expression of APOE locus genes could impact mitochondrial function, contributing to the development of AD or longevity. Our study underscores the significant role of the APOE locus in modulating mitochondrial function and provides valuable insights into the underlying mechanisms of AD and aging, emphasizing the importance of this locus in clinical research.

RevDate: 2023-07-12

Park DS, Nguyen SC, Isenhart R, et al (2023)

High-throughput Oligopaint screen identifies druggable 3D genome regulators.

Nature [Epub ahead of print].

The human genome functions as a three-dimensional chromatin polymer, driven by a complex collection of chromosome interactions[1-3]. Although the molecular rules governing these interactions are being quickly elucidated, relatively few proteins regulating this process have been identified. Here, to address this gap, we developed high-throughput DNA or RNA labelling with optimized Oligopaints (HiDRO)-an automated imaging pipeline that enables the quantitative measurement of chromatin interactions in single cells across thousands of samples. By screening the human druggable genome, we identified more than 300 factors that influence genome folding during interphase. Among these, 43 genes were validated as either increasing or decreasing interactions between topologically associating domains. Our findings show that genetic or chemical inhibition of the ubiquitous kinase GSK3A leads to increased long-range chromatin looping interactions in a genome-wide and cohesin-dependent manner. These results demonstrate the importance of GSK3A signalling in nuclear architecture and the use of HiDRO for identifying mechanisms of spatial genome organization.

RevDate: 2023-07-11

Kadam S, Kumari K, Manivannan V, et al (2023)

Predicting scale-dependent chromatin polymer properties from systematic coarse-graining.

Nature communications, 14(1):4108.

Simulating chromatin is crucial for predicting genome organization and dynamics. Although coarse-grained bead-spring polymer models are commonly used to describe chromatin, the relevant bead dimensions, elastic properties, and the nature of inter-bead potentials are unknown. Using nucleosome-resolution contact probability (Micro-C) data, we systematically coarse-grain chromatin and predict quantities essential for polymer representation of chromatin. We compute size distributions of chromatin beads for different coarse-graining scales, quantify fluctuations and distributions of bond lengths between neighboring regions, and derive effective spring constant values. Unlike the prevalent notion, our findings argue that coarse-grained chromatin beads must be considered as soft particles that can overlap, and we derive an effective inter-bead soft potential and quantify an overlap parameter. We also compute angle distributions giving insights into intrinsic folding and local bendability of chromatin. While the nucleosome-linker DNA bond angle naturally emerges from our work, we show two populations of local structural states. The bead sizes, bond lengths, and bond angles show different mean behavior at Topologically Associating Domain (TAD) boundaries and TAD interiors. We integrate our findings into a coarse-grained polymer model and provide quantitative estimates of all model parameters, which can serve as a foundational basis for all future coarse-grained chromatin simulations.

RevDate: 2023-07-10

Liu H, Tsai H, Yang M, et al (2023)

Three-dimensional genome structure and function.

MedComm, 4(4):e326.

Linear DNA undergoes a series of compression and folding events, forming various three-dimensional (3D) structural units in mammalian cells, including chromosomal territory, compartment, topologically associating domain, and chromatin loop. These structures play crucial roles in regulating gene expression, cell differentiation, and disease progression. Deciphering the principles underlying 3D genome folding and the molecular mechanisms governing cell fate determination remains a challenge. With advancements in high-throughput sequencing and imaging techniques, the hierarchical organization and functional roles of higher-order chromatin structures have been gradually illuminated. This review systematically discussed the structural hierarchy of the 3D genome, the effects and mechanisms of cis-regulatory elements interaction in the 3D genome for regulating spatiotemporally specific gene expression, the roles and mechanisms of dynamic changes in 3D chromatin conformation during embryonic development, and the pathological mechanisms of diseases such as congenital developmental abnormalities and cancer, which are attributed to alterations in 3D genome organization and aberrations in key structural proteins. Finally, prospects were made for the research about 3D genome structure, function, and genetic intervention, and the roles in disease development, prevention, and treatment, which may offer some clues for precise diagnosis and treatment of related diseases.

RevDate: 2023-07-07

Onrust-van Schoonhoven A, de Bruijn MJW, Stikker B, et al (2023)

3D chromatin reprogramming primes human memory TH2 cells for rapid recall and pathogenic dysfunction.

Science immunology, 8(85):eadg3917.

Memory T cells provide long-lasting defense responses through their ability to rapidly reactivate, but how they efficiently "recall" an inflammatory transcriptional program remains unclear. Here, we show that human CD4[+] memory T helper 2 (TH2) cells carry a chromatin landscape synergistically reprogrammed at both one-dimensional (1D) and 3D levels to accommodate recall responses, which is absent in naive T cells. In memory TH2 cells, recall genes were epigenetically primed through the maintenance of transcription-permissive chromatin at distal (super)enhancers organized in long-range 3D chromatin hubs. Precise transcriptional control of key recall genes occurred inside dedicated topologically associating domains ("memory TADs"), in which activation-associated promoter-enhancer interactions were preformed and exploited by AP-1 transcription factors to promote rapid transcriptional induction. Resting memory TH2 cells from patients with asthma showed premature activation of primed recall circuits, linking aberrant transcriptional control of recall responses to chronic inflammation. Together, our results implicate stable multiscale reprogramming of chromatin organization as a key mechanism underlying immunological memory and dysfunction in T cells.

RevDate: 2023-07-03

Syed SA, Shqillo K, Nand A, et al (2023)

Protein arginine methyltransferase 5 (Prmt5) localizes to chromatin loop anchors and modulates expression of genes at TAD boundaries during early adipogenesis.

bioRxiv : the preprint server for biology pii:2023.06.13.544859.

Protein arginine methyltransferase 5 (Prmt5) is an essential regulator of embryonic development and adult progenitor cell functions. Prmt5 expression is mis-regulated in many cancers, and the development of Prmt5 inhibitors as cancer therapeutics is an active area of research. Prmt5 functions via effects on gene expression, splicing, DNA repair, and other critical cellular processes. We examined whether Prmt5 functions broadly as a genome-wide regulator of gene transcription and higher-order chromatin interactions during the initial stages of adipogenesis using ChIP-Seq, RNA-seq, and Hi-C using 3T3-L1 cells, a frequently utilized model for adipogenesis. We observed robust genome-wide Prmt5 chromatin-binding at the onset of differentiation. Prmt5 localized to transcriptionally active genomic regions, acting as both a positive and a negative regulator. A subset of Prmt5 binding sites co-localized with mediators of chromatin organization at chromatin loop anchors. Prmt5 knockdown decreased insulation strength at the boundaries of topologically associating domains (TADs) adjacent to sites with Prmt5 and CTCF co-localization. Genes overlapping such weakened TAD boundaries showed transcriptional dysregulation. This study identifies Prmt5 as a broad regulator of gene expression, including regulation of early adipogenic factors, and reveals an unappreciated requirement for Prmt5 in maintaining strong insulation at TAD boundaries and overall chromatin organization.

RevDate: 2023-06-30

Zhang Y, M Blanchette (2023)

Reference panel-guided super-resolution inference of Hi-C data.

Bioinformatics (Oxford, England), 39(Supplement_1):i386-i393.

MOTIVATION: Accurately assessing contacts between DNA fragments inside the nucleus with Hi-C experiment is crucial for understanding the role of 3D genome organization in gene regulation. This challenging task is due in part to the high sequencing depth of Hi-C libraries required to support high-resolution analyses. Most existing Hi-C data are collected with limited sequencing coverage, leading to poor chromatin interaction frequency estimation. Current computational approaches to enhance Hi-C signals focus on the analysis of individual Hi-C datasets of interest, without taking advantage of the facts that (i) several hundred Hi-C contact maps are publicly available and (ii) the vast majority of local spatial organizations are conserved across multiple cell types.

RESULTS: Here, we present RefHiC-SR, an attention-based deep learning framework that uses a reference panel of Hi-C datasets to facilitate the enhancement of Hi-C data resolution of a given study sample. We compare RefHiC-SR against tools that do not use reference samples and find that RefHiC-SR outperforms other programs across different cell types, and sequencing depths. It also enables high-accuracy mapping of structures such as loops and topologically associating domains.

https://github.com/BlanchetteLab/RefHiC.

RevDate: 2023-06-29

Pandupuspitasari NS, Khan FA, Huang C, et al (2023)

Recent advances in chromosome capture techniques unraveling 3D genome architecture in germ cells, health, and disease.

Functional & integrative genomics, 23(3):214.

In eukaryotes, the genome does not emerge in a specific shape but rather as a hierarchial bundle within the nucleus. This multifaceted genome organization consists of multiresolution cellular structures, such as chromosome territories, compartments, and topologically associating domains, which are frequently defined by architecture, design proteins including CTCF and cohesin, and chromatin loops. This review briefly discusses the advances in understanding the basic rules of control, chromatin folding, and functional areas in early embryogenesis. With the use of chromosome capture techniques, the latest advancements in technologies for visualizing chromatin interactions come close to revealing 3D genome formation frameworks with incredible detail throughout all genomic levels, including at single-cell resolution. The possibility of detecting variations in chromatin architecture might open up new opportunities for disease diagnosis and prevention, infertility treatments, therapeutic approaches, desired exploration, and many other application scenarios.

RevDate: 2023-06-29

Zhang Y, Cao X, Gao Z, et al (2023)

MATR3-antisense LINE1 RNA meshwork scaffolds higher-order chromatin organization.

EMBO reports [Epub ahead of print].

Long interspersed nuclear elements (LINEs) play essential roles in shaping chromatin states, while the factors that cooperate with LINEs and their roles in higher-order chromatin organization remain poorly understood. Here, we show that MATR3, a nuclear matrix protein, interplays with antisense LINE1 (AS L1) RNAs to form a meshwork via phase separation, providing a dynamic platform for chromatin spatial organization. MATR3 and AS L1 RNAs affect the nuclear localization of each other. After MATR3 depletion, the chromatin, particularly H3K27me3-modified chromatin, redistributes in the cell nuclei. Topologically associating domains (TADs) that highly transcribe MATR3-associated AS L1 RNAs show decreased intra-TAD interactions in both AML12 and ES cells. MATR3 depletion increases the accessibility of H3K27me3 domains adjacent to MATR3-associated AS L1, without affecting H3K27me3 modifications. Furthermore, amyotrophic lateral sclerosis (ALS)-associated MATR3 mutants alter biophysical features of the MATR3-AS L1 RNA meshwork and cause an abnormal H3K27me3 staining. Collectively, we reveal a role of the meshwork formed by MATR3 and AS L1 RNAs in gathering chromatin in the nucleus.

RevDate: 2023-06-28

Sun Y, Xu X, Zhao W, et al (2023)

RAD21 is the core subunit of the cohesin complex involved in directing genome organization.

Genome biology, 24(1):155.

BACKGROUND: The ring-shaped cohesin complex is an important factor for the formation of chromatin loops and topologically associating domains (TADs) by loop extrusion. However, the regulation of association between cohesin and chromatin is poorly understood. In this study, we use super-resolution imaging to reveal the unique role of cohesin subunit RAD21 in cohesin loading and chromatin structure regulation.

RESULTS: We directly visualize that up-regulation of RAD21 leads to excessive chromatin loop extrusion into a vermicelli-like morphology with RAD21 clustered into foci and excessively loaded cohesin bow-tying a TAD to form a beads-on-a-string-type pattern. In contrast, up-regulation of the other four cohesin subunits results in even distributions. Mechanistically, we identify that the essential role of RAD21 is attributed to the RAD21-loader interaction, which facilitates the cohesin loading process rather than increasing the abundance of cohesin complex upon up-regulation of RAD21. Furthermore, Hi-C and genomic analysis reveal how RAD21 up-regulation affects genome-wide higher-order chromatin structure. Accumulated contacts are shown at TAD corners while inter-TAD interactions increase after vermicelli formation. Importantly, we find that in breast cancer cells, the expression of RAD21 is aberrantly high with poor patient survival and RAD21 forms beads in the nucleus. Up-regulated RAD21 in HeLa cells leads to compartment switching and up-regulation of cancer-related genes.

CONCLUSIONS: Our results provide key insights into the molecular mechanism by which RAD21 facilitates the cohesin loading process and provide an explanation to how cohesin and loader work cooperatively to promote chromatin extrusion, which has important implications in construction of three-dimensional genome organization.

RevDate: 2023-06-16

Wang M, Sreenivas P, Sunkel BD, et al (2023)

The 3D chromatin landscape of rhabdomyosarcoma.

NAR cancer, 5(3):zcad028.

Rhabdomyosarcoma (RMS) is a pediatric soft tissue cancer with a lack of precision therapy options for patients. We hypothesized that with a general paucity of known mutations in RMS, chromatin structural driving mechanisms are essential for tumor proliferation. Thus, we carried out high-depth in situ Hi-C in representative cell lines and patient-derived xenografts (PDXs) to define chromatin architecture in each major RMS subtype. We report a comprehensive 3D chromatin structural analysis and characterization of fusion-positive (FP-RMS) and fusion-negative RMS (FN-RMS). We have generated spike-in in situ Hi-C chromatin interaction maps for the most common FP-RMS and FN-RMS cell lines and compared our data with PDX models. In our studies, we uncover common and distinct structural elements in large Mb-scale chromatin compartments, tumor-essential genes within variable topologically associating domains and unique patterns of structural variation. Our high-depth chromatin interactivity maps and comprehensive analyses provide context for gene regulatory events and reveal functional chromatin domains in RMS.

RevDate: 2023-06-15

Rekaik H, Lopez-Delisle L, Hintermann A, et al (2023)

Sequential and directional insulation by conserved CTCF sites underlies the Hox timer in stembryos.

Nature genetics [Epub ahead of print].

During development, Hox genes are temporally activated according to their relative positions on their clusters, contributing to the proper identities of structures along the rostrocaudal axis. To understand the mechanism underlying this Hox timer, we used mouse embryonic stem cell-derived stembryos. Following Wnt signaling, the process involves transcriptional initiation at the anterior part of the cluster and a concomitant loading of cohesin complexes enriched on the transcribed DNA segments, that is, with an asymmetric distribution favoring the anterior part of the cluster. Chromatin extrusion then occurs with successively more posterior CTCF sites acting as transient insulators, thus generating a progressive time delay in the activation of more posterior-located genes due to long-range contacts with a flanking topologically associating domain. Mutant stembryos support this model and reveal that the presence of evolutionary conserved and regularly spaced intergenic CTCF sites controls the precision and the pace of this temporal mechanism.

RevDate: 2023-06-11

da Costa-Nunes JA, D Noordermeer (2023)

TADs: Dynamic structures to create stable regulatory functions.

Current opinion in structural biology, 81:102622 pii:S0959-440X(23)00096-9 [Epub ahead of print].

Mammalian chromosomes are organized at different length scales within the cell nucleus. Topologically Associating Domains (TADs) are structural units of 3D genome organization with functions in gene regulation, DNA replication, recombination and repair. Whereas TADs were initially interpreted as insulated domains, recent studies are revealing that these domains should be interpreted as dynamic collections of actively extruding loops. This process of loop extrusion is subsequently blocked at dedicated TAD boundaries, thereby promoting intra-domain interactions over their surroundings. In this review, we discuss how mammalian TAD structure can emerge from this dynamic process and we discuss recent evidence that TAD boundaries can have regulatory functions.

RevDate: 2023-06-06

Peng X, Li Y, Zou M, et al (2023)

CATAD: exploring topologically associating domains from an insight of core-attachment structure.

Briefings in bioinformatics pii:7188844 [Epub ahead of print].

Identifying topologically associating domains (TADs), which are considered as the basic units of chromosome structure and function, can facilitate the exploration of the 3D-structure of chromosomes. Methods have been proposed to identify TADs by detecting the boundaries of TADs or identifying the closely interacted regions as TADs, while the possible inner structure of TADs is seldom investigated. In this study, we assume that a TAD is composed of a core and its surrounding attachments, and propose a method, named CATAD, to identify TADs based on the core-attachment structure model. In CATAD, the cores of TADs are identified based on the local density and cosine similarity, and the surrounding attachments are determined based on boundary insulation. CATAD was applied to the Hi-C data of two human cell lines and two mouse cell lines, and the results show that the boundaries of TADs identified by CATAD are significantly enriched by structural proteins, histone modifications, transcription start sites and enzymes. Furthermore, CATAD outperforms other methods in many cases, in terms of the average peak, boundary tagged ratio and fold change. In addition, CATAD is robust and rarely affected by the different resolutions of Hi-C matrices. Conclusively, identifying TADs based on the core-attachment structure is useful, which may inspire researchers to explore TADs from the angles of possible spatial structures and formation process.

RevDate: 2023-06-05

Kessler S, Minoux M, Joshi O, et al (2023)

A multiple super-enhancer region establishes inter-TAD interactions and controls Hoxa function in cranial neural crest.

Nature communications, 14(1):3242.

Enhancer-promoter interactions preferentially occur within boundary-insulated topologically associating domains (TADs), limiting inter-TAD interactions. Enhancer clusters in linear proximity, termed super-enhancers (SEs), ensure high target gene expression levels. Little is known about SE topological regulatory impact during craniofacial development. Here, we identify 2232 genome-wide putative SEs in mouse cranial neural crest cells (CNCCs), 147 of which target genes establishing CNCC positional identity during face formation. In second pharyngeal arch (PA2) CNCCs, a multiple SE-containing region, partitioned into Hoxa Inter-TAD Regulatory Element 1 and 2 (HIRE1 and HIRE2), establishes long-range inter-TAD interactions selectively with Hoxa2, that is required for external and middle ear structures. HIRE2 deletion in a Hoxa2 haploinsufficient background results in microtia. HIRE1 deletion phenocopies the full homeotic Hoxa2 knockout phenotype and induces PA3 and PA4 CNCC abnormalities correlating with Hoxa2 and Hoxa3 transcriptional downregulation. Thus, SEs can overcome TAD insulation and regulate anterior Hoxa gene collinear expression in a CNCC subpopulation-specific manner during craniofacial development.

RevDate: 2023-06-01

Gu J, Li S, Zhu B, et al (2023)

Genetic variation and domestication of horses revealed by 10 chromosome-level genomes and whole-genome resequencing.

Molecular ecology resources [Epub ahead of print].

Understanding the genetic variations of the horse (Equus caballus) genome will improve breeding conservation and welfare. However, genetic variations in long segments, such as structural variants (SVs), remain understudied. We de novo assembled 10 chromosome-level three-dimensional horse genomes, each representing a distinct breed, and analysed horse SVs using a multi-assembly approach. Our findings suggest that SVs with the accumulation of mammalian-wide interspersed repeats related to long interspersed nuclear elements might be a horse-specific mechanism to modulate genome-wide gene regulatory networks. We found that olfactory receptors were commonly loss and accumulated deleterious mutations, but no purge of deleterious mutations occurred during horse domestication. We examined the potential effects of SVs on the spatial structure of chromatin via topologically associating domains (TADs). Breed-specific TADs were significantly enriched by breed-specific SVs. We identified 4199 unique breakpoint-resolved novel insertions across all chromosomes that account for 2.84 Mb sequences missing from the reference genome. Several novel insertions might have potential functional consequences, as 519 appeared to reside within 449 gene bodies. These genes are primarily involved in pathogen recognition, innate immune responses and drug metabolism. Moreover, 37 diverse horses were resequenced. Combining this with public data, we analysed 97 horses through a comparative population genomics approach to identify the genetic basis underlying breed characteristics using Thoroughbreds as a case study. We provide new scientific evidence for horse domestication, an understanding of the genetic mechanism underlying the phenotypic evolution of horses, and a comprehensive genetic variation resource for further genetic studies of horses.

RevDate: 2023-05-31

Li D, Zhao XY, Zhou S, et al (2023)

Multidimensional profiling reveals GATA1-modulated stage-specific chromatin states and functional associations during human erythropoiesis.

Nucleic acids research pii:7186996 [Epub ahead of print].

Mammalian erythroid development can be divided into three stages: hematopoietic stem and progenitor cell (HSPC), erythroid progenitor (Ery-Pro), and erythroid precursor (Ery-Pre). However, the mechanisms by which the 3D genome changes to establish the stage-specific transcription programs that are critical for erythropoiesis remain unclear. Here, we analyze the chromatin landscape at multiple levels in defined populations from primary human erythroid culture. While compartments and topologically associating domains remain largely unchanged, ∼50% of H3K27Ac-marked enhancers are dynamic in HSPC versus Ery-Pre. The enhancer anchors of enhancer-promoter loops are enriched for occupancy of respective stage-specific transcription factors (TFs), indicating these TFs orchestrate the enhancer connectome rewiring. The master TF of erythropoiesis, GATA1, is found to occupy most erythroid gene promoters at the Ery-Pro stage, and mediate conspicuous local rewiring through acquiring binding at the distal regions in Ery-Pre, promoting productive erythroid transcription output. Knocking out GATA1 binding sites precisely abrogates local rewiring and corresponding gene expression. Interestingly, knocking down GATA1 can transiently revert the cell state to an earlier stage and prolong the window of progenitor state. This study reveals mechanistic insights underlying chromatin rearrangements during development by integrating multidimensional chromatin landscape analyses to associate with transcription output and cellular states.

RevDate: 2023-05-30

Tolokh IS, Kinney NA, Sharakhov IV, et al (2023)

Strong interactions between highly dynamic lamina-associated domains and the nuclear envelope stabilize the 3D architecture of Drosophila interphase chromatin.

Epigenetics & chromatin, 16(1):21.

BACKGROUND: Interactions among topologically associating domains (TADs), and between the nuclear envelope (NE) and lamina-associated domains (LADs) are expected to shape various aspects of three-dimensional (3D) chromatin structure and dynamics; however, relevant genome-wide experiments that may provide statistically significant conclusions remain difficult.

RESULTS: We have developed a coarse-grained dynamical model of D. melanogaster nuclei at TAD resolution that explicitly accounts for four distinct epigenetic classes of TADs and LAD-NE interactions. The model is parameterized to reproduce the experimental Hi-C map of the wild type (WT) nuclei; it describes time evolution of the chromatin over the G1 phase of the interphase. The simulations include an ensemble of nuclei, corresponding to the experimentally observed set of several possible mutual arrangements of chromosomal arms. The model is validated against multiple structural features of chromatin from several different experiments not used in model development. Predicted positioning of all LADs at the NE is highly dynamic-the same LAD can attach, detach and move far away from the NE multiple times during interphase. The probabilities of LADs to be in contact with the NE vary by an order of magnitude, despite all having the same affinity to the NE in the model. These probabilities are mostly determined by a highly variable local linear density of LADs along the genome, which also has the same strong effect on the predicted positioning of individual TADs -- higher probability of a TAD to be near NE is largely determined by a higher linear density of LADs surrounding this TAD. The distribution of LADs along the chromosome chains plays a notable role in maintaining a non-random average global structure of chromatin. Relatively high affinity of LADs to the NE in the WT nuclei substantially reduces sensitivity of the global radial chromatin distribution to variations in the strength of TAD-TAD interactions compared to the lamin depleted nuclei, where a small (0.5 kT) increase of cross-type TAD-TAD interactions doubles the chromatin density in the central nucleus region.

CONCLUSIONS: A dynamical model of the entire fruit fly genome makes multiple genome-wide predictions of biological interest. The distribution of LADs along the chromatin chains affects their probabilities to be in contact with the NE and radial positioning of highly mobile TADs, playing a notable role in creating a non-random average global structure of the chromatin. We conjecture that an important role of attractive LAD-NE interactions is to stabilize global chromatin structure against inevitable cell-to-cell variations in TAD-TAD interactions.

RevDate: 2023-05-30

Hamba Y, Kamatani T, Miya F, et al (2023)

Topologically associating domain underlies tissue specific expression of long intergenic non-coding RNAs.

iScience, 26(5):106640.

Accumulating evidence indicates that long intergenic non-coding RNAs (lincRNAs) show more tissue-specific expression patterns than protein-coding genes (PCGs). However, although lincRNAs are subject to canonical transcriptional regulation like PCGs, the molecular basis for the specificity of their expression patterns remains unclear. Here, using expression data and coordinates of topologically associating domains (TADs) in human tissues, we show that lincRNA loci are significantly enriched in the more internal region of TADs compared to PCGs and that lincRNAs within TADs have higher tissue specificity than those outside TADs. Based on these, we propose an analytical framework to interpret transcriptional status using lincRNA as an indicator. We applied it to hypertrophic cardiomyopathy data and found disease-specific transcriptional regulation: ectopic expression of keratin at the TAD level and derepression of myocyte differentiation-related genes by E2F1 with down-regulation of LINC00881. Our results provide understanding of the function and regulation of lincRNAs according to genomic structure.

RevDate: 2023-05-16

Zhang X, Yu G, Dai Y, et al (2023)

High-resolution Hi-C maps highlight multiscale chromatin architecture reorganization during cold stress in Brachypodium distachyon.

BMC plant biology, 23(1):260.

BACKGROUND: The adaptation of plants to cold stress involves changes in gene expression profiles that are associated with epigenetic regulation. Although the three-dimensional (3D) genome architecture is considered an important epigenetic regulator, the role of 3D genome organization in the cold stress response remains unclear.

RESULTS: In this study, we developed high-resolution 3D genomic maps using control and cold-treated leaf tissue of the model plant Brachypodium distachyon using Hi-C to determine how cold stress affects the 3D genome architecture. We generated ~ 1.5 kb resolution chromatin interaction maps and showed that cold stress disrupts different levels of chromosome organization, including A/B compartment transition, a reduction in chromatin compartmentalization and the size of topologically associating domains (TADs), and loss of long-range chromatin loops. Integrating RNA-seq information, we identified cold-response genes and revealed that transcription was largely unaffected by the A/B compartment transition. The cold-response genes were predominantly localized in compartment A. In contrast, transcriptional changes are required for TAD reorganization. We demonstrated that dynamic TAD events were associated with H3K27me3 and H3K27ac state alterations. Moreover, a loss of chromatin looping, rather than a gain of looping, coincides with alterations in gene expression, indicating that chromatin loop disruption may play a more important role than loop formation in the cold-stress response.

CONCLUSIONS: Our study highlights the multiscale 3D genome reprogramming that occurs during cold stress and expands our knowledge of the mechanisms underlying transcriptional regulation in response to cold stress in plants.

RevDate: 2023-05-10

Parodi L, Comeau ME, Georgakis MK, et al (2023)

Deep resequencing of the 1q22 locus in non-lobar intracerebral hemorrhage.

medRxiv : the preprint server for health sciences pii:2023.04.18.23288754.

OBJECTIVE: Genome-wide association studies have identified 1q22 as a susceptibility locus for cerebral small vessel diseases (CSVDs), including non-lobar intracerebral hemorrhage (ICH) and lacunar stroke. In the present study we performed targeted high-depth sequencing of 1q22 in ICH cases and controls to further characterize this locus and prioritize potential causal mechanisms, which remain unknown.

METHODS: 95,000 base pairs spanning 1q22 , including SEMA4A, SLC25A44 and PMF1 / PMF1-BGLAP were sequenced in 1,055 spontaneous ICH cases (534 lobar and 521 non-lobar) and 1,078 controls. Firth regression and RIFT analysis were used to analyze common and rare variants, respectively. Chromatin interaction analyses were performed using Hi-C, ChIP-Seq and ChIA-PET databases. Multivariable Mendelian randomization (MVMR) assessed whether alterations in gene-specific expression relative to regionally co-expressed genes at 1q22 could be causally related to ICH risk.

RESULTS: Common and rare variant analyses prioritized variants in SEMA4A 5'-UTR and PMF1 intronic regions, overlapping with active promoter and enhancer regions based on ENCODE annotation. Hi-C data analysis determined that 1q22 is spatially organized in a single chromatin loop and that the genes therein belong to the same Topologically Associating Domain. ChIP-Seq and ChIA-PET data analysis highlighted the presence of long-range interactions between the SEMA4A -promoter and PMF1 -enhancer regions prioritized by association testing. MVMR analyses demonstrated that PMF1 overexpression could be causally related to non-lobar ICH risk.

INTERPRETATION: Altered promoter-enhancer interactions leading to PMF1 overexpression, potentially dysregulating polyamine catabolism, could explain demonstrated associations with non-lobar ICH risk at 1q22 , offering a potential new target for prevention of ICH and CSVD.

RevDate: 2023-05-10

Li A, Zeng G, Wang H, et al (2023)

DeDoc2 Identifies and Characterizes the Hierarchy and Dynamics of Chromatin TAD-Like Domains in the Single Cells.

Advanced science (Weinheim, Baden-Wurttemberg, Germany) [Epub ahead of print].

Topologically associating domains (TADs) are functional chromatin units with hierarchical structure. However, the existence, prevalence, and dynamics of such hierarchy in single cells remain unexplored. Here, a new generation TAD-like domain (TLD) detection algorithm, named deDoc2, to decode the hierarchy of TLDs in single cells, is reported. With dynamic programming, deDoc2 seeks genome partitions with global minimal structure entropy for both whole and local contact matrix. Notably, deDoc2 outperforms state-of-the-art tools and is one of only two tools able to identify the hierarchy of TLDs in single cells. By applying deDoc2, it is showed that the hierarchy of TLDs in single cells is highly dynamic during cell cycle, as well as among human brain cortex cells, and that it is associated with cellular identity and functions. Thus, the results demonstrate the abundance of information potentially encoded by TLD hierarchy for functional regulation. The deDoc2 can be freely accessed at https://github.com/zengguangjie/deDoc2.

RevDate: 2023-05-04

Liu J, Li P, Sun J, et al (2023)

LPAD: using network construction and label propagation to detect topologically associating domains from Hi-C data.

Briefings in bioinformatics pii:7150739 [Epub ahead of print].

With the development of chromosome conformation capture technique, the study of spatial conformation of a genome based on Hi-C technique has made a quantum leap. Previous studies reveal that genomes are folded into hierarchy of three-dimensional (3D) structures associated with topologically associating domains (TADs), and detecting TAD boundaries is of great significance in the chromosome-level analysis of 3D genome architecture. In this paper, we propose a novel TAD identification method, LPAD, which first extracts node correlations from global interactions of chromosomes based on the random walk with restart and then builds an undirected graph from Hi-C contact matrix. Next, LPAD designs a label propagation-based approach to discover communities and generates TADs. Experimental results verify the effectiveness and quality of TAD detections compared with existing methods. Furthermore, experimental evaluation of chromatin immunoprecipitation sequencing data shows that LPAD performs high enrichment of histone modifications remarkably nearby the TAD boundaries, and these results demonstrate LPAD's advantages on TAD identification accuracy.

RevDate: 2023-04-28

Liu P, Li D, Zhang J, et al (2023)

Comparative three-dimensional genome architectures of adipose tissues provide insight into human-specific regulation of metabolic homeostasis.

The Journal of biological chemistry pii:S0021-9258(23)01785-4 [Epub ahead of print].

Elucidating the regulatory mechanisms of human adipose tissues (ATs) evolution is essential for understanding human-specific metabolic regulation, but the functional importance and evolutionary dynamics of three-dimensional (3D) genome organizations of ATs are not well defined. Here, we compared the 3D genome architectures of anatomically distinct ATs from humans and six representative mammalian models. We recognized evolutionarily conserved and human-specific chromatin conformation in ATs at multiple scales, including compartmentalization, topologically associating domain (TAD), and promoter-enhancer interactions (PEI), which have not been described previously. We found promoter-enhancer interaction (PEI) are much more evolutionarily dynamic with respect to compartmentalization and topologically associating domain (TAD). Compared to conserved PEIs, human-specific PEIs are enriched for human-specific sequence and the binding motifs of their potential mediators (transcription factors) are less conserved. Our data also demonstrated that genes involved in the evolutionarily dynamics of chromatin organization have weaker transcriptional conservation than those associated with conserved chromatin organization. Furthermore, the genes involved in energy metabolism and the maintenance of metabolic homeostasis are enriched in human-specific chromatin organization, while housekeeping genes, health-related genes and genetic variations are enriched in evolutionarily conserved compared to human-specific chromatin organization. Finally, we showed extensively divergent human-specific 3D genome organizations among one subcutaneous and three visceral ATs. Together, these findings provide a global overview of 3D genome architecture dynamics between ATs from human and mammalian models, and new insights into understanding the regulatory evolution of human ATs.

RevDate: 2023-04-27

Keough KC, Whalen S, Inoue F, et al (2023)

Three-dimensional genome rewiring in loci with human accelerated regions.

Science (New York, N.Y.), 380(6643):eabm1696.

Human accelerated regions (HARs) are conserved genomic loci that evolved at an accelerated rate in the human lineage and may underlie human-specific traits. We generated HARs and chimpanzee accelerated regions with an automated pipeline and an alignment of 241 mammalian genomes. Combining deep learning with chromatin capture experiments in human and chimpanzee neural progenitor cells, we discovered a significant enrichment of HARs in topologically associating domains containing human-specific genomic variants that change three-dimensional (3D) genome organization. Differential gene expression between humans and chimpanzees at these loci suggests rewiring of regulatory interactions between HARs and neurodevelopmental genes. Thus, comparative genomics together with models of 3D genome folding revealed enhancer hijacking as an explanation for the rapid evolution of HARs.

RevDate: 2023-04-26

Zhang H, GA Blobel (2023)

Genome folding dynamics during the M-to-G1-phase transition.

Current opinion in genetics & development, 80:102036 pii:S0959-437X(23)00016-3 [Epub ahead of print].

All measurable features of higher-order chromosomal architecture undergo drastic reorganization as cells enter and exit mitosis. During mitosis, gene transcription is temporarily halted, the nuclear envelope is dismantled, and chromosomes undergo condensation. At this time, chromatin compartments, topologically associating domains (TADs), and loops that connect enhancers with promoters as well as CTCF/cohesin loops are dissolved. Upon G1 entry, genome organization is rebuilt in the daughter nuclei to resemble that of the mother nucleus. We survey recent studies that traced these features in relation to gene expression during the mitosis-to-G1-phase transition at high temporal resolution. Dissection of fluctuating architectural features informed the hierarchical relationships of chromosomal organization, the mechanisms by which they are formed, and their mutual (in-) dependence. These studies highlight the importance of considering the cell cycle dynamics for studies of chromosomal organization.

RevDate: 2023-04-21

Wang B, Liu K, Li Y, et al (2023)

DFHiC: A dilated full convolution model to enhance the resolution of Hi-C data.

Bioinformatics (Oxford, England) pii:7135829 [Epub ahead of print].

MOTIVATION: Hi-C technology has been the most widely used chromosome conformation capture(3C) experiment that measures the frequency of all paired interactions in the entire genome, which is a powerful tool for studying the 3D structure of the genome. The fineness of the constructed genome structure depends on the resolution of Hi-C data. However, due to the fact that high-resolution Hi-C data require deep sequencing and thus high experimental cost, most available Hi-C data are in low-resolution. Hence, it is essential to enhance the quality of Hi-C data by developing the effective computational methods.

RESULTS: In this work, we propose a novel method, so-called DFHiC, which generates the high-resolution Hi-C matrix from the low-resolution Hi-C matrix in the framework of the dilated convolutional neural network. The dilated convolution is able to effectively explore the global patterns in the overall Hi-C matrix by taking advantage of the information of the Hi-C matrix in a way of the longer genomic distance. Consequently, DFHiC can improve the resolution of the Hi-C matrix reliably and accurately. More importantly, the super-resolution Hi-C data enhanced by DFHiC is more in line with the real high-resolution Hi-C data than those done by the other existing methods, in terms of both chromatin significant interactions and identifying topologically associating domains (TADs).

AVAILABILITY: https://github.com/BinWangCSU/DFHiC.

SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

RevDate: 2023-04-20

Rajderkar S, Barozzi I, Zhu Y, et al (2023)

Topologically associating domain boundaries are required for normal genome function.

Communications biology, 6(1):435.

Topologically associating domain (TAD) boundaries partition the genome into distinct regulatory territories. Anecdotal evidence suggests that their disruption may interfere with normal gene expression and cause disease phenotypes[1-3], but the overall extent to which this occurs remains unknown. Here we demonstrate that targeted deletions of TAD boundaries cause a range of disruptions to normal in vivo genome function and organismal development. We used CRISPR genome editing in mice to individually delete eight TAD boundaries (11-80 kb in size) from the genome. All deletions examined resulted in detectable molecular or organismal phenotypes, which included altered chromatin interactions or gene expression, reduced viability, and anatomical phenotypes. We observed changes in local 3D chromatin architecture in 7 of 8 (88%) cases, including the merging of TADs and altered contact frequencies within TADs adjacent to the deleted boundary. For 5 of 8 (63%) loci examined, boundary deletions were associated with increased embryonic lethality or other developmental phenotypes. For example, a TAD boundary deletion near Smad3/Smad6 caused complete embryonic lethality, while a deletion near Tbx5/Lhx5 resulted in a severe lung malformation. Our findings demonstrate the importance of TAD boundary sequences for in vivo genome function and reinforce the critical need to carefully consider the potential pathogenicity of noncoding deletions affecting TAD boundaries in clinical genetics screening.

RevDate: 2023-04-19

Davidson IF, Barth R, Zaczek M, et al (2023)

CTCF is a DNA-tension-dependent barrier to cohesin-mediated loop extrusion.

Nature [Epub ahead of print].

In eukaryotes, genomic DNA is extruded into loops by cohesin[1]. By restraining this process, the DNA-binding protein CCCTC-binding factor (CTCF) generates topologically associating domains (TADs)[2,3] that have important roles in gene regulation and recombination during development and disease[1,4-7]. How CTCF establishes TAD boundaries and to what extent these are permeable to cohesin is unclear[8]. Here, to address these questions, we visualize interactions of single CTCF and cohesin molecules on DNA in vitro. We show that CTCF is sufficient to block diffusing cohesin, possibly reflecting how cohesive cohesin accumulates at TAD boundaries, and is also sufficient to block loop-extruding cohesin, reflecting how CTCF establishes TAD boundaries. CTCF functions asymmetrically, as predicted; however, CTCF is dependent on DNA tension. Moreover, CTCF regulates cohesin's loop-extrusion activity by changing its direction and by inducing loop shrinkage. Our data indicate that CTCF is not, as previously assumed, simply a barrier to cohesin-mediated loop extrusion but is an active regulator of this process, whereby the permeability of TAD boundaries can be modulated by DNA tension. These results reveal mechanistic principles of how CTCF controls loop extrusion and genome architecture.

RevDate: 2023-04-18

Yin X, Romero-Campero FJ, Yang M, et al (2023)

Binding by the Polycomb complex component BMI1 and H2A monoubiquitination shape local and long-range interactions in the Arabidopsis genome.

The Plant cell pii:7127682 [Epub ahead of print].

Three-dimensional (3D) chromatin organization is highly dynamic during development and seems to play a crucial role in regulating gene expression. Self-interacting domains, commonly called topologically associating domains (TADs) or compartment domains (CDs), have been proposed as the basic structural units of chromatin organization. Surprisingly, although these units have been found in several plant species, they escaped detection in Arabidopsis (Arabidopsis thaliana). Here, we show that the Arabidopsis genome is partitioned into contiguous CDs with different epigenetic features, which are required to maintain appropriate intra-CD and long-range interactions. Consistent with this notion, the histone-modifying Polycomb group machinery is involved in 3D chromatin organization. Yet, while it is clear that Polycomb Repressive Complex 2 (PRC2)-mediated trimethylation of histone H3 on lysine 27 (H3K27me3) helps establish local and long-range chromatin interactions in plants, the implications of PRC1-mediated histone H2A monoubiquitination on lysine 121 (H2AK121ub) are unclear. We found that PRC1, together with PRC2, maintains intra-CD interactions, but it also hinders the formation of H3K4me3-enriched local chromatin loops when acting independently of PRC2. Moreover, the loss of PRC1 or PRC2 activity differentially affects long-range chromatin interactions, and these 3D changes differentially affect gene expression. Our results suggest that H2AK121ub helps prevent the formation of transposable element/H3K27me1-rich long loops and serves as a docking point for H3K27me3 incorporation.

RevDate: 2023-04-17

Guo M, Yao Z, Jiang C, et al (2023)

Three-dimensional and single-cell sequencing of liver cancer reveals comprehensive host-virus interactions in HBV infection.

Frontiers in immunology, 14:1161522.

BACKGROUNDS: Hepatitis B virus (HBV) infection is a major risk factor for chronic liver diseases and liver cancer (mainly hepatocellular carcinoma, HCC), while the underlying mechanisms and host-virus interactions are still largely elusive.

METHODS: We applied HiC sequencing to HepG2 (HBV-) and HepG2-2.2.15 (HBV+) cell lines and combined them with public HCC single-cell RNA-seq data, HCC bulk RNA-seq data, and both genomic and epigenomic ChIP-seq data to reveal potential disease mechanisms of HBV infection and host-virus interactions reflected by 3D genome organization.

RESULTS: We found that HBV enhanced overall proximal chromatin interactions (CIs) of liver cells and primarily affected regional CIs on chromosomes 13, 14, 17, and 22. Interestingly, HBV altered the boundaries of many topologically associating domains (TADs), and genes nearby these boundaries showed functional enrichment in cell adhesion which may promote cancer metastasis. Moreover, A/B compartment analysis revealed dramatic changes on chromosomes 9, 13 and 21, with more B compartments (inactive or closed) shifting to A compartments (active or open). The A-to-B regions (closing) harbored enhancers enriched in the regulation of inflammatory responses, whereas B-to-A regions (opening) were enriched for transposable elements (TE). Furthermore, we identified large HBV-induced structural variations (SVs) that disrupted tumor suppressors, NLGN4Y and PROS1. Finally, we examined differentially expressed genes and TEs in single hepatocytes with or without HBV infection, by using single-cell RNA-seq data. Consistent with our HiC sequencing findings, two upregulated genes that promote HBV replication, HNF4A and NR5A2, were located in regions with HBV-enhanced CIs, and five TEs were located in HBV-activated regions. Therefore, HBV may promote liver diseases by affecting the human 3D genome structure.

CONCLUSION: Our work promotes mechanistic understanding of HBV infection and host-virus interactions related to liver diseases that affect billions of people worldwide. Our findings may also have implications for novel immunotherapeutic strategies targeting HBV infection.

RevDate: 2023-04-13

Cheng J, Cao X, Wang X, et al (2023)

Dynamic chromatin architectures provide insights into the genetics of cattle myogenesis.

Journal of animal science and biotechnology, 14(1):59.

BACKGROUND: Sharply increased beef consumption is propelling the genetic improvement projects of beef cattle in China. Three-dimensional genome structure is confirmed to be an important layer of transcription regulation. Although genome-wide interaction data of several livestock species have already been produced, the genome structure states and its regulatory rules in cattle muscle are still limited.

RESULTS: Here we present the first 3D genome data in Longissimus dorsi muscle of fetal and adult cattle (Bos taurus). We showed that compartments, topologically associating domains (TADs), and loop undergo re-organization and the structure dynamics were consistent with transcriptomic divergence during muscle development. Furthermore, we annotated cis-regulatory elements in cattle genome during myogenesis and demonstrated the enrichments of promoter and enhancer in selection sweeps. We further validated the regulatory function of one HMGA2 intronic enhancer near a strong sweep region on primary bovine myoblast proliferation.

CONCLUSIONS: Our data provide key insights of the regulatory function of high order chromatin structure and cattle myogenic biology, which will benefit the progress of genetic improvement of beef cattle.

RevDate: 2023-04-13

Mao A, Chen C, Portillo-Ledesma S, et al (2023)

Effect of Single-Residue Mutations on CTCF Binding to DNA: Insights from Molecular Dynamics Simulations.

International journal of molecular sciences, 24(7): pii:ijms24076395.

In humans and other eukaryotes, DNA is condensed into chromatin fibers that are further wound into chromosomes. This organization allows regulatory elements in the genome, often distant from each other in the linear DNA, to interact and facilitate gene expression through regions known as topologically associating domains (TADs). CCCTC-binding factor (CTCF) is one of the major components of TAD formation and is responsible for recruiting a partner protein, cohesin, to perform loop extrusion and facilitate proper gene expression within TADs. Because single-residue CTCF mutations have been linked to the development of a variety of cancers in humans, we aim to better understand how these mutations affect the CTCF structure and its interaction with DNA. To this end, we compare all-atom molecular dynamics simulations of a wildtype CTCF-DNA complex to those of eight different cancer-linked CTCF mutant sequences. We find that most mutants have lower binding energies compared to the wildtype protein, leading to the formation of less stable complexes. Depending on the type and position of the mutation, this loss of stability can be attributed to major changes in the electrostatic potential, loss of hydrogen bonds between the CTCF and DNA, and/or destabilization of specific zinc fingers. Interestingly, certain mutations in specific fingers can affect the interaction with the DNA of other fingers, explaining why mere single mutations can impair CTCF function. Overall, these results shed mechanistic insights into experimental observations and further underscore CTCF's importance in the regulation of chromatin architecture and gene expression.

RevDate: 2023-04-11

Tan ZW, Toong PJ, Guarnera E, et al (2023)

Disrupted chromatin architecture in olfactory sensory neurons: looking for the link from COVID-19 infection to anosmia.

Scientific reports, 13(1):5906.

We tackle here genomic mechanisms of a rapid onset and recovery from anosmia-a potential diagnostic indicator for early-stage COVID-19 infection. Based on previous observations on how olfactory receptor (OR) gene expression is regulated via chromatin structure in mice, we hypothesized that the disruption of the OR gene expression and, respectively, deficiency of the OR function can be caused by chromatin reorganization taking place upon SARS-CoV-2 infection. We obtained chromatin ensemble reconstructions from COVID-19 patients and control samples using our original computational framework for the whole-genome 3D chromatin ensemble reconstruction. Specifically, we used megabase-scale structural units and effective interactions between them obtained in the Markov State modelling of the Hi-C contact network as an unput in the stochastic embedding procedure of the whole-genome 3D chromatin ensemble reconstruction. We have also developed here a new procedure for analyzing fine structural hierarchy with (sub)TAD-size units in local chromatin regions, which we apply here to parts of chromosomes containing OR genes and corresponding regulatory elements. We observed structural modifications in COVID-19 patients on different levels of chromatin organization, from the alteration of whole genome structure and chromosomal intermingling to reorganization of contacts between chromatin loops at the level of topologically associating domains. While complementary data on known regulatory elements point to potential pathology-associated changes within the overall picture of chromatin alterations, further investigation using additional epigenetic factors mapped on 3D reconstructions with improved resolution will be required for better understanding of anosmia caused by SARS-CoV-2 infection.

RevDate: 2023-04-11

Melo US, Jatzlau J, Prada-Medina CA, et al (2023)

Enhancer hijacking at the ARHGAP36 locus is associated with connective tissue to bone transformation.

Nature communications, 14(1):2034.

Heterotopic ossification is a disorder caused by abnormal mineralization of soft tissues in which signaling pathways such as BMP, TGFβ and WNT are known key players in driving ectopic bone formation. Identifying novel genes and pathways related to the mineralization process are important steps for future gene therapy in bone disorders. In this study, we detect an inter-chromosomal insertional duplication in a female proband disrupting a topologically associating domain and causing an ultra-rare progressive form of heterotopic ossification. This structural variant lead to enhancer hijacking and misexpression of ARHGAP36 in fibroblasts, validated here by orthogonal in vitro studies. In addition, ARHGAP36 overexpression inhibits TGFβ, and activates hedgehog signaling and genes/proteins related to extracellular matrix production. Our work on the genetic cause of this heterotopic ossification case has revealed that ARHGAP36 plays a role in bone formation and metabolism, outlining first details of this gene contributing to bone-formation and -disease.

RevDate: 2023-04-05

Fritz AJ, Ghule PN, Toor R, et al (2023)

Spatiotemporal Epigenetic Control of the Histone Gene Chromatin Landscape during the Cell Cycle.

Critical reviews in eukaryotic gene expression, 33(3):85-97.

Higher-order genomic organization supports the activation of histone genes in response to cell cycle regulatory cues that epigenetically mediates stringent control of transcription at the G1/S-phase transition. Histone locus bodies (HLBs) are dynamic, non-membranous, phase-separated nuclear domains where the regulatory machinery for histone gene expression is organized and assembled to support spatiotemporal epigenetic control of histone genes. HLBs provide molecular hubs that support synthesis and processing of DNA replication-dependent histone mRNAs. These regulatory microenvironments support long-range genomic interactions among non-contiguous histone genes within a single topologically associating domain (TAD). HLBs respond to activation of the cyclin E/CDK2/NPAT/HINFP pathway at the G1/S transition. HINFP and its coactivator NPAT form a complex within HLBs that controls histone mRNA transcription to support histone protein synthesis and packaging of newly replicated DNA. Loss of HINFP compromises H4 gene expression and chromatin formation, which may result in DNA damage and impede cell cycle progression. HLBs provide a paradigm for higher-order genomic organization of a subnuclear domain that executes an obligatory cell cycle-controlled function in response to cyclin E/CDK2 signaling. Understanding the coordinately and spatiotemporally organized regulatory programs in focally defined nuclear domains provides insight into molecular infrastructure for responsiveness to cell signaling pathways that mediate biological control of growth, differentiation phenotype, and are compromised in cancer.

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RJR Experience and Expertise

Researcher

Robbins holds BS, MS, and PhD degrees in the life sciences. He served as a tenured faculty member in the Zoology and Biological Science departments at Michigan State University. He is currently exploring the intersection between genomics, microbial ecology, and biodiversity — an area that promises to transform our understanding of the biosphere.

Educator

Robbins has extensive experience in college-level education: At MSU he taught introductory biology, genetics, and population genetics. At JHU, he was an instructor for a special course on biological database design. At FHCRC, he team-taught a graduate-level course on the history of genetics. At Bellevue College he taught medical informatics.

Administrator

Robbins has been involved in science administration at both the federal and the institutional levels. At NSF he was a program officer for database activities in the life sciences, at DOE he was a program officer for information infrastructure in the human genome project. At the Fred Hutchinson Cancer Research Center, he served as a vice president for fifteen years.

Technologist

Robbins has been involved with information technology since writing his first Fortran program as a college student. At NSF he was the first program officer for database activities in the life sciences. At JHU he held an appointment in the CS department and served as director of the informatics core for the Genome Data Base. At the FHCRC he was VP for Information Technology.

Publisher

While still at Michigan State, Robbins started his first publishing venture, founding a small company that addressed the short-run publishing needs of instructors in very large undergraduate classes. For more than 20 years, Robbins has been operating The Electronic Scholarly Publishing Project, a web site dedicated to the digital publishing of critical works in science, especially classical genetics.

Speaker

Robbins is well-known for his speaking abilities and is often called upon to provide keynote or plenary addresses at international meetings. For example, in July, 2012, he gave a well-received keynote address at the Global Biodiversity Informatics Congress, sponsored by GBIF and held in Copenhagen. The slides from that talk can be seen HERE.

Facilitator

Robbins is a skilled meeting facilitator. He prefers a participatory approach, with part of the meeting involving dynamic breakout groups, created by the participants in real time: (1) individuals propose breakout groups; (2) everyone signs up for one (or more) groups; (3) the groups with the most interested parties then meet, with reports from each group presented and discussed in a subsequent plenary session.

Designer

Robbins has been engaged with photography and design since the 1960s, when he worked for a professional photography laboratory. He now prefers digital photography and tools for their precision and reproducibility. He designed his first web site more than 20 years ago and he personally designed and implemented this web site. He engages in graphic design as a hobby.

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