STAG2 promotes the myelination transcriptional program in oligodendrocytes [ChIP-seq]

Cohesin folds chromosomes via DNA loop extrusion. Cohesin-mediated chromosome loops regulate transcription by shaping long-range enhancer-promoter interactions, among other mechanisms. Mutations of cohesin subunits and regulators cause human developmental diseases termed cohesinopathy. Vertebrate cohesin consists of SMC1, SMC3, RAD21, and either STAG1 or STAG2. To probe the physiological functions of cohesin, we created conditional knockout (cKO) mice with Stag2 deleted in the nervous system. Stag2 cKO mice exhibit growth retardation, neurological defects, and premature death, in part due to insufficient myelination of nerve fibers. Stag2 cKO oligodendrocytes exhibit delayed maturation and downregulation of myelinationrelated genes. Stag2 loss reduces promoter-anchored loops at downregulated genes in oligodendrocytes. Thus, STAG2-cohesin generates promoter-anchored loops at myelinationpromoting genes to facilitate their transcription. Our study implicates defective myelination as a contributing factor to cohesinopathy and establishes oligodendrocytes as a relevant cell type to explore the mechanisms by which cohesin regulates transcription. Overall design: ChIP-Seq was performed on primary oligodendrocytes for the following experiments: one replicate with anti-STAG2 antibody of Stag2f/y cells and one replicate with anti-H3K27ac antibody of Stag2f/y and Stag2f/y; Cre cells

黏连蛋白（cohesin）通过DNA环挤出（DNA loop extrusion）折叠染色体。黏连蛋白介导的染色体环可通过塑造远距离增强子-启动子相互作用等多种机制调控基因转录。黏连蛋白亚基及其调控因子的突变会引发人类发育疾病，这类疾病被称为黏连蛋白病（cohesinopathy）。脊椎动物中的黏连蛋白由SMC1、SMC3、RAD21以及STAG1或STAG2组成。为探究黏连蛋白的生理功能，我们构建了神经系统中特异性敲除Stag2的条件性基因敲除（conditional knockout, cKO）小鼠模型。Stag2 cKO小鼠表现出生长迟缓、神经功能缺陷以及过早死亡，其部分诱因是神经纤维髓鞘形成不足。Stag2 cKO的少突胶质细胞表现出成熟延迟以及髓鞘形成相关基因的表达下调。Stag2缺失会减少少突胶质细胞中下调基因的启动子锚定环（promoter-anchored loops）的数量。综上，STAG2-黏连蛋白可在促髓鞘形成相关基因处形成启动子锚定环，以促进这些基因的转录。本研究表明髓鞘形成缺陷是黏连蛋白病的致病因素之一，并确立了少突胶质细胞作为研究黏连蛋白调控转录机制的相关细胞类型。整体实验设计：针对原代少突胶质细胞开展染色质免疫共沉淀测序（ChIP-Seq, Chromatin Immunoprecipitation Sequencing）实验，具体包括：1份以抗STAG2抗体处理Stag2f/y细胞的重复样本，以及1份分别以抗H3K27ac抗体处理Stag2f/y与Stag2f/y;Cre细胞的重复样本。