Project description:Understanding the topological configurations of chromatin can reveal valuable insights into how the genome and epigenome act in concert to control cell fate during development. Here we generate high-resolution architecture maps across seven genomic loci in embryonic stem cells and neural progenitor cells. We observe a hierarchy of 3-D interactions that undergo marked reorganization at the sub-Mb scale during differentiation. Distinct combinations of CTCF, Mediator, and cohesin show widespread enrichment in architecture at different length scales. CTCF/cohesin anchor long-range constitutive interactions that might form the topological basis for invariant sub-domains. Conversely, Mediator/cohesin together with pioneer factors bridge short-range enhancer-promoter interactions within and between larger sub-domains. Knockdown of Smc1 or Med12 in ES cells results in disruption of spatial architecture and down-regulation of genes found in cohesin-mediated interactions. We conclude that cell type-specific chromatin organization occurs at the sub-Mb scale and that architectural proteins shape the genome in hierarchical length scales. Analysis of higher-order chromatin chromatin architecture in mouse ES cells and ES-derived NPCs. Analysis of CTCF and Smc1 occupied sites in ES-derived NPCs.
Project description:Hox genes are essential regulators of embryonic development. They are activated in a temporal sequence following their topological order within their genomic clusters. Subsequently, states of activity are fine-tuned and maintained to translate into domains of progressively overlapping gene products. While the mechanisms underlying such temporal and spatial progressions begin to be understood, many of their aspects remain unclear. We have systematically analyzed the 3D chromatin organization of Hox clusters in vivo, during their activation using high-resolution circular chromosome conformation capture (4C-seq). Initially, Hox clusters are organized as single 3D chromatin compartments decorated with bivalent chromatin marks. Their progressive transcriptional activation is associated with a dynamic bi-modal 3D organization, whereby the genes switch one after the other, from an inactive to an active 3D compartment. These local 3D dynamics occur within a larger constitutive framework of interactions within the surrounding Topological Associated Domains, which confirms previous results that regulation of this process in primarily cluster intrinsic. The local step-wise progression in time can be stopped and memorized at various body levels and hence it may accounts for the various chromatin architectures previously described at different anterior to posterior body levels for the same embryo at a later stage. Circular Chromosome Conformation Capture (4C-seq) samples from mouse ES cells and mouse embryonic samples at different stages of development. Data based on 41 biological samples.
Project description:Recent studies of genome-wide chromatin interactions have revealed that the human genome is partitioned into many self-associating topological domains. The boundary sequences are enriched for binding sites of CTCF and the cohesin complex, implicating these two factors in the establishment or maintenance of topological domains. To determine the role of cohesin and CTCF in higher order chromatin architecture in human cells, we proteolytically cleaved the cohesin complex from interphase chromatin and examined changes in chromosomal organization as well as transcriptome. We observed a general loss of local chromosomal interactions upon disruption of cohesin complex, but the topological domains remain intact. However, we found that depletion of CTCF by RNA interference in these cells not only reduced intra-domain interactions but also increased inter-domain interactions. Further more, distinct groups of genes become mis-regulated upon depletion of cohesin and CTCF. Taken together, these observations suggest that CTCF and cohesin contribute in different ways to chromatin organization and gene regulation. Hi-C and mRNA-seq experiments in Cohesin and CTCF depleted HEK293 cells
Project description:Hox genes are essential regulators of embryonic development. They are activated in a temporal sequence following their topological order within their genomic clusters. Subsequently, states of activity are fine-tuned and maintained to translate into domains of progressively overlapping gene products. While the mechanisms underlying such temporal and spatial progressions begin to be understood, many of their aspects remain unclear. We have systematically analyzed the 3D chromatin organization of Hox clusters in vivo, during their activation using high-resolution circular chromosome conformation capture (4C-seq). Initially, Hox clusters are organized as single 3D chromatin compartments decorated with bivalent chromatin marks. Their progressive transcriptional activation is associated with a dynamic bi-modal 3D organization, whereby the genes switch one after the other, from an inactive to an active 3D compartment. These local 3D dynamics occur within a larger constitutive framework of interactions within the surrounding Topological Associated Domains, which confirms previous results that regulation of this process in primarily cluster intrinsic. The local step-wise progression in time can be stopped and memorized at various body levels and hence it may accounts for the various chromatin architectures previously described at different anterior to posterior body levels for the same embryo at a later stage. RNA-seq from mouse ES cells and mouse embryonic stage E10.5 forebrain. Data based on 2 biological samples.
Project description:Hox genes are essential regulators of embryonic development. They are activated in a temporal sequence following their topological order within their genomic clusters. Subsequently, states of activity are fine-tuned and maintained to translate into domains of progressively overlapping gene products. While the mechanisms underlying such temporal and spatial progressions begin to be understood, many of their aspects remain unclear. We have systematically analyzed the 3D chromatin organization of Hox clusters in vivo, during their activation using high-resolution circular chromosome conformation capture (4C-seq). Initially, Hox clusters are organized as single 3D chromatin compartments decorated with bivalent chromatin marks. Their progressive transcriptional activation is associated with a dynamic bi-modal 3D organization, whereby the genes switch one after the other, from an inactive to an active 3D compartment. These local 3D dynamics occur within a larger constitutive framework of interactions within the surrounding Topological Associated Domains, which confirms previous results that regulation of this process in primarily cluster intrinsic. The local step-wise progression in time can be stopped and memorized at various body levels and hence it may accounts for the various chromatin architectures previously described at different anterior to posterior body levels for the same embryo at a later stage. ChIP-seq samples (H3K4me3 and H3K27me3) from mouse ES cells and mouse embryonic stage E8.5 pre-somitic mesoderm. Data based on 4 biological samples.
Project description:To determine whether a TP63/KLF5-regulated super-enhancer region can impact SREBF1 transcription, circularized chromosome conformation capture (4C) assays were performed. 4C assays identified complex, extensive interactions between the SREBF1 promoter and the super-enhancer region Moreover, these DNA-DNA contacts were strictly confined within the super-enhancer region, highlighting the specificity of chromatin interactions
Project description:The Regulators of Complement Activation (RCA) gene cluster comprises several tandemly arranged genes which share functions in the innate immune system. We aimed to investigate the structural organisation of the RCA gene cluster to identify key regulatory elements that influence the expression of CR2 and other genes in this important immunomodulatory region. Using 4C-seq, we captured extensive CTCF-mediated chromatin looping across the RCA gene cluster in B cells and showed these were organised into two topological associated domains (TADs). Interestingly, the inter-TAD boundary was located within the CR1 gene at a well-characterised segmental duplication. Additionally, we mapped numerous gene-gene and gene-enhancer interactions across the region, revealing extensive co-regulation. Importantly, we uncovered an intergenic enhancer and functionally demonstrated this element upregulates two RCA members (CR2 and CD55) in B cells simultaneously. Here, we highlight novel, long-range mechanisms whereby SLE susceptibility may be influenced by genetic variants, and the important contribution of chromatin topology to gene regulation and complex genetic disease.