Cohesin-dependent regulation of dynamic gene expression during differentiation is lost in Cohesin-mutated myeloid malignancies

The Cohesin complex critically controls interactions between proximal and distal cis-regulatory elements, while Cohesin disruption causes improper gene activation. This process associates with biased hematopoiesis, and Cohesin mutations are common in myeloid neoplasia. In this study, we initially explore Cohesin-associated dynamics and regulation of hematopoietic stem cell renewal and erythropoiesis. Cohesin binding to chromatin increases during erythroid differentiation at active promoters and enhancers only, with pre-binding of Etv6 predicting the subsequent dynamics of Cohesin binding at these elements. Etv6 also binds with the Cohesin complex at chromatin during haematopoiesis. Perturbation of Cohesin members does not alter hematopoietic self-renewal, but severely impairs erythroid differentiation. As in normal erythroid differentiation, the strongest impairment of gene activation in Cohesin-perturbed erythropoiesis occurs at Etv6-pre-bound loci. Taken together these findings propose a mechanism for how the Cohesin complex regulates the induction of gene expression during differentiation and how this may be perturbed in myeloid malignancies. Integrative analysis of Cohesin-associated cis-regulatory units (ChIP Seq, RNA Seq, promoter Capture HiC in HSPC and Erythroid cells

黏连蛋白复合物（Cohesin complex）可关键性调控近端与远端顺式调控元件（cis-regulatory elements）之间的相互作用，而黏连蛋白功能失调会引发异常基因激活。该过程与偏倚性造血相关，且黏连蛋白突变在髓系肿瘤（myeloid neoplasia）中较为常见。本研究首先探究了黏连蛋白相关的动态调控机制，及其对造血干细胞自我更新与红细胞生成的调控作用。在仅活跃的启动子和增强子区域，红细胞分化过程中黏连蛋白与染色质（chromatin）的结合水平显著升高，且Etv6的预结合可预测黏连蛋白在这些调控元件上的后续结合动态。此外，在造血过程中，Etv6亦可与黏连蛋白复合物结合于染色质区域。对黏连蛋白亚基的扰动并不会改变造血干细胞的自我更新能力，但会严重损害红细胞分化进程。与正常红细胞分化过程一致，在黏连蛋白扰动的红细胞生成过程中，基因激活受到的最显著抑制发生在Etv6预结合基因座处。综上，本研究结果揭示了黏连蛋白复合物如何调控分化过程中的基因表达诱导，以及该机制在髓系恶性肿瘤中发生失调的潜在路径。本研究针对黏连蛋白相关顺式调控单元开展整合分析，涵盖造血干祖细胞（HSPC）与红细胞系细胞中的染色质免疫沉淀测序（ChIP-seq）、RNA测序（RNA-seq）及启动子捕获高通量染色体构象捕获（promoter Capture HiC）实验。