Project description:In multicellular organisms, transcription regulation is one of the central mechanisms modelling lineage differentiation and cell-fate determination. Transcription requires dynamic chromatin configurations between promoters and their corresponding distal regulatory elements. It is believed that their communication occurs within large discrete foci of aggregated RNA polymerases termed transcription factories in three-dimensional nuclear space. However, the dynamic nature of chromatin connectivity has not been characterized at the genome-wide level. Here, through a chromatin interaction analysis with paired-end tagging approach using an antibody that primarily recognizes the pre-initiation complexes of RNA polymerase II, we explore the transcriptional interactomes of three mouse cells of progressive lineage commitment, including pluripotent embryonic stem cells, neural stem cells and neurosphere stem/progenitor cells. Our global chromatin connectivity maps reveal approximately 40,000 long-range interactions, suggest precise enhancer?promoter associations and delineate cell-type-specific chromatin structures. Analysis of the complex regulatory repertoire shows that there are extensive colocalizations among promoters and distal-acting enhancers. Most of the enhancers associate with promoters located beyond their nearest active genes, indicating that the linear juxtaposition is not the only guiding principle driving enhancer target selection. Although promoter?enhancer interactions exhibit high cell-type specificity, promoters involved in interactions are found to be generally common and mostly active among different cells. Chromatin connectivity networks reveal that the pivotal genes of reprogramming functions are transcribed within physical proximity to each other in embryonic stem cells, linking chromatin architecture to coordinated gene expression. Our study sets the stage for the full-scale dissection of spatial and temporal genome structures and their roles in orchestrating development.
Project description:Enhancers determine spatiotemporal gene expression programs by engaging with long-range promoters. However, it remains unknown how enhancers find their cognate promoters. We recently developed a RIC-seq technology to identify enhancer-promoter connectivity using pairwise interacting enhancer RNAs and promoter-derived noncoding RNAs in HeLa cells. Here, we apply this technology to generate high-confidence enhancer-promoter RNA interaction (EPRI) maps in six additional cell lines. Using these maps, we discover that 37.9% of the enhancer-promoter RNA interaction sites are overlapped with Alu sequences. These pairwise interacting Alu and non-Alu RNA sequences tend to be complementary and potentially form duplexes. Knockout of Alu elements compromises enhancer-promoter looping, whereas Alu insertion or CRISPR-dCasRx-mediated Alu tethering to unregulated promoter RNAs can create new loops to homologous enhancers. Importantly, mapping 535,404 noncoding risk variants back to the EPRI maps enabled us to construct variant-to-function maps for interpreting their molecular functions, including 15,318 deletions or insertions in 11,677 Alu elements that affect 6,497 protein-coding genes. We further demonstrate that polymorphic Alu insertion at PTK2 enhancer can promote tumorigenesis. Our study uncovers a principle for determining enhancer-promoter pairing specificity and provides a framework to link noncoding risk variants to their molecular functions.
Project description:Although the locations of promoters and enhancers have been identified in several cell types, we have yet limited information on their connectivity. We developed HiCap, which combines Hi-C with promoter sequence capture, to enable genome-wide identification of regulatory interactions with single-enhancer resolution. HiCap analyses of mouse embryonic stem cells (mESC) identified promoter-enhancer interactions predictive of gene expression change upon perturbation, opening up for genomic analyses of long-range gene regulation. HiCap was designed by combining Hi-C with with sequence capture (for all promoters) and carried out in mouse embryonic stem cells (mESC)
Project description:Although the locations of promoters and enhancers have been identified in several cell types, we have yet limited information on their connectivity. We developed HiCap, which combines Hi-C with promoter sequence capture, to enable genome-wide identification of regulatory interactions with single-enhancer resolution. HiCap analyses of mouse embryonic stem cells (mESC) identified promoter-enhancer interactions predictive of gene expression change upon perturbation, opening up for genomic analyses of long-range gene regulation. HiCap was designed by combining Hi-C with with sequence capture (for all promoters) and carried out in mouse embryonic stem cells (mESC)
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:Using genome-wide Chromatin Interaction Analysis with Paired-End-Tag sequencing, we mapped long-range chromatin interactions associated with RNA polymerase II in three different mouse cell lines and uncovered widespread promoter-centered interactions. These interactions further aggregated into higher-order clusters, in which proximal and distant genes are engaged through enhancer-promoter interactions. Comparative analyses of different cell lines imply that cell specific enhancer interactions are dynamic among different cell specific transcription, and suggest significant enrichment of enhancer-promoter interactions for cell specific manner. Overall, our study provides novel insights into the three-dimensional basis of transcription activity in mouse cells. RNA polymerase II (RNAPII) guided chromatin interactions were discovered by Chromatin Interaction Analysis with Paired-End Tag (ChIA-PET) sequencing, in order to study genome-wise the enhancer-promoter interactions. Three cell lines, namely mouse embryonic stem cell E14, Neural stem cell NS5 and neuroshpere cells were grown under standard culture conditions and harvested at log phase. Harvested cells were cross-linked using 1% formaldehyde followed by neutralization with 0.2M glycine. Chromatin was isolated and subjected to ChIA-PET protocol as described in Fullwood et al, 2009. The ChIA-PET sequence reads were processed and analyzed using ChIA-PET Tool (Li et al, 2010)
Project description:Although the locations of promoters and enhancers have been identified in several cell types, we have yet limited information on their connectivity. We developed HiCap, which combines Hi-C with promoter sequence capture, to enable genome-wide identification of regulatory interactions with single-enhancer resolution. HiCap analyses of mouse embryonic stem cells (mESC) identified promoter-enhancer interactions predictive of gene expression change upon perturbation, opening up for genomic analyses of long-range gene regulation.
Project description:Although the locations of promoters and enhancers have been identified in several cell types, we have yet limited information on their connectivity. We developed HiCap, which combines Hi-C with promoter sequence capture, to enable genome-wide identification of regulatory interactions with single-enhancer resolution. HiCap analyses of mouse embryonic stem cells (mESC) identified promoter-enhancer interactions predictive of gene expression change upon perturbation, opening up for genomic analyses of long-range gene regulation.
Project description:Chromosome conformation capture technologies have revealed important insights into genome folding. Yet, how spatial genome architecture is related to gene expression and cell fate remains unclear. We mapped comprehensively 3D chromatin organization during mouse neural differentiation in vitro and in vivo, generating the highest resolution Hi-C maps available to date. We found that transcription is correlated with chromatin insulation and long-range interactions, but dCas9-mediated activation is insufficient for creating topological domain (TAD) boundaries de novo. Additionally, we discovered long-range contacts between gene bodies of exon-rich, active genes in all cell types. During neural differentiation, contacts between active TADs become less pronounced while inactive TADs interact stronger. An extensive Polycomb network in stem cells is disrupted, while dynamic interactions between proneural transcription factors appear in vivo. Finally, cell-type specific enhancer-promoter contacts are established concomitant to gene expression. This work shows that multiple factors influence the dynamics of chromatin interactions in development.
Project description:The most prominent model for long-range enhancer regulation involves direct enhancer-promoter interaction by looping out the intervening chromatin. Using a synthetic biology approach, we have determined that a chromatin unfolding bteween Shh and its enhancers is regulated specifically by the Shh-Brain-Enhancers and is mediated by the recruitment of Poly (ADP-Ribose) Polymerase 1. This ‘chromatin unfolding’ model represents a new mechanism of long-range enhancer-promoter communication in addition to the looping and tracking models. Using 5C study the enhancer-driven activation of the Sonic hedgehog gene (Shh)