Project description:Genetic variation and 3D chromatin structure have major roles in gene regulation. Structural differences between genotypically different chromosomes and their effects on gene expression remain ill understood, due to challenges in mapping 3D genome structure with allele-specific resolution. Here, we applied Genome Architecture Mapping (GAM) to a hybrid mouse embryonic stem cell (ESC) line with high SNP density. Given its high efficiency of haplotype phasing, GAM resolves allele-specific 3D genome structures with high sensitivity. We discovered extensive genotype-specific folding of chromosomes in compartments, topologically associating domains (TADs), long-range enhancer-promoter contacts and CTCF loops, often coinciding with allele-specific gene expression in association with Polycomb repression. We show that histone genes are expressed with allelic imbalance and involved in allele-specific chromatin contacts marked by H3K27me3. Functional analysis through conditional Ezh2- or Ring1b-knockdown shows a role for Polycomb repression in tuning histone protein levels. Our work reveals that the homologous chromosomes have highly distinct 3D folding structures, and their intricate relationships with gene-specific mechanisms of allelic expression imbalance.
Project description:Genetic variation and 3D chromatin structure have major roles in gene regulation. Structural differences between genotypically different chromosomes and their effects on gene expression remain ill understood, due to challenges in mapping 3D genome structure with allele-specific resolution. Here, we applied Genome Architecture Mapping (GAM) to a hybrid mouse embryonic stem cell (ESC) line with high SNP density. Given the high efficiency of GAM in haplotype phasing, we could resolve allele-specific 3D genome structures with high sensitivity. We discovered extensive genotype-specific folding of chromosomes in compartments, topologically associating domains (TADs), long-range enhancer-promoter contacts and CTCF loops, often coinciding with allele-specific gene expression in association with Polycomb repression. We show that histone genes are expressed with allelic imbalance in ESCs, and involved in allele-specific chromatin contacts marked by H3K27me3. Functional analysis through conditional Ezh2- or Ring1b-knockdown shows a role for Polycomb repression in tuning histone protein levels. Our work reveals that the homologous chromosomes have highly distinct 3D folding structures, and their intricate relationships with gene-specific mechanisms of allelic expression imbalance.
Project description:Genetic variation and 3D chromatin structure have major roles in gene regulation. Structural differences between genotypically different chromosomes and their effects on gene expression remain ill understood, due to challenges in mapping 3D genome structure with allele-specific resolution. Here, we applied Genome Architecture Mapping (GAM) to a hybrid mouse embryonic stem cell (ESC) line with high SNP density. Given its high efficiency of haplotype phasing, GAM resolves allele-specific 3D genome structures with high sensitivity. We discovered extensive genotype-specific folding of chromosomes in compartments, topologically associating domains (TADs), long-range enhancer-promoter contacts and CTCF loops, often coinciding with allele-specific gene expression in association with Polycomb repression. We show that histone genes are expressed with allelic imbalance and involved in allele-specific chromatin contacts marked by H3K27me3. Functional analysis through conditional Ezh2- or Ring1b-knockdown shows a role for Polycomb repression in tuning histone protein levels. Our work reveals that the homologous chromosomes have highly distinct 3D folding structures, and their intricate relationships with gene-specific mechanisms of allelic expression imbalance.
Project description:Genetic variation and 3D chromatin structure have major roles in gene regulation. Structural differences between genotypically different chromosomes and their effects on gene expression remain ill understood, due to challenges in mapping 3D genome structure with allele-specific resolution. Here, we applied Genome Architecture Mapping (GAM) to a hybrid mouse embryonic stem cell (ESC) line with high SNP density. Given its high efficiency of haplotype phasing, GAM resolves allele-specific 3D genome structures with high sensitivity. We discovered extensive genotype-specific folding of chromosomes in compartments, topologically associating domains (TADs), long-range enhancer-promoter contacts and CTCF loops, often coinciding with allele-specific gene expression in association with Polycomb repression. We show that histone genes are expressed with allelic imbalance and involved in allele-specific chromatin contacts marked by H3K27me3. Functional analysis through conditional Ezh2- or Ring1b-knockdown shows a role for Polycomb repression in tuning histone protein levels. Our work reveals that the homologous chromosomes have highly distinct 3D folding structures, and their intricate relationships with gene-specific mechanisms of allelic expression imbalance.
Project description:Mammalian chromosomes fold into arrays of megabase‐sized topologically associating domains (TADs), which are arranged into compartments spanning multiple megabases of genomic DNA. TADs have internal substructures that are often cell type specific, but their higher‐order organization remains elusive. Here, we investigate TAD higher‐order interactions with Hi‐C through neuronal differentiation and show that they form a hierarchy of domains‐within‐domains (metaTADs) extending across genomic scales up to the range of entire chromosomes. We find that TAD interactions are well captured by tree‐like, hierarchical structures irrespective of cell type. metaTAD tree structures correlate with genetic, epigenomic and expression features, and structural tree rearrangements during differentiation are linked to transcriptional state changes. Using polymer modelling, we demonstrate that hierarchical folding promotes efficient chromatin packaging without the loss of contact specificity, highlighting a role far beyond the simple need for packing efficiency.