ヒトコンデンシンによる染色体構造の構築と制御メカニズムの解明

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 白髭 克彦, 東京大学教授 高橋 直樹, 東京大学教授 秋山 徹, 東京大学教授 渡邊 嘉典, 東京大学教授 小林 武彦University of Tokyo(東京大学

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

Abstract 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

Meiotic cohesins mediate initial loading of HORMAD1 to the chromosomes and coordinate SC formation during meiotic prophase.

During meiotic prophase, sister chromatids are organized into axial element (AE), which underlies the structural framework for the meiotic events such as meiotic recombination and homolog synapsis. HORMA domain-containing proteins (HORMADs) localize along AE and play critical roles in the regulation of those meiotic events. Organization of AE is attributed to two groups of proteins: meiotic cohesins REC8 and RAD21L; and AE components SYCP2 and SYCP3. It has been elusive how these chromosome structural proteins contribute to the chromatin loading of HORMADs prior to AE formation. Here we newly generated Sycp2 null mice and showed that initial chromatin loading of HORMAD1 was mediated by meiotic cohesins prior to AE formation. HORMAD1 interacted not only with the AE components SYCP2 and SYCP3 but also with meiotic cohesins. Notably, HORMAD1 interacted with meiotic cohesins even in Sycp2-KO, and localized along cohesin axial cores independently of the AE components SYCP2 and SYCP3. Hormad1/Rad21L-double knockout (dKO) showed more severe defects in the formation of synaptonemal complex (SC) compared to Hormad1-KO or Rad21L-KO. Intriguingly, Hormad1/Rec8-dKO but not Hormad1/Rad21L-dKO showed precocious separation of sister chromatid axis. These findings suggest that meiotic cohesins REC8 and RAD21L mediate chromatin loading and the mode of action of HORMAD1 for synapsis during early meiotic prophase