Center for Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Strasse 21, 50931 Cologne, Germany.
Department of Cell Biology, Erasmus Medical Center, 3015 CN Rotterdam, the Netherlands.
Cell Stem Cell. 2017 May 4;20(5):689-705.e9. doi: 10.1016/j.stem.2017.02.004. Epub 2017 Mar 9.
Poised enhancers marked by H3K27me3 in pluripotent stem cells have been implicated in the establishment of somatic expression programs during embryonic stem cell (ESC) differentiation. However, the functional relevance and mechanism of action of poised enhancers remain unknown. Using CRISPR/Cas9 technology to engineer precise genetic deletions, we demonstrate that poised enhancers are necessary for the induction of major anterior neural regulators. Interestingly, circularized chromosome conformation capture sequencing (4C-seq) shows that poised enhancers already establish physical interactions with their target genes in ESCs in a polycomb repressive complex 2 (PRC2)-dependent manner. Loss of PRC2 does not activate poised enhancers or induce their putative target genes in undifferentiated ESCs; however, loss of PRC2 in differentiating ESCs severely and specifically compromises the induction of major anterior neural genes representing poised enhancer targets. Overall, our work illuminates an unexpected function for polycomb proteins in facilitating neural induction by endowing major anterior neural loci with a permissive regulatory topology.
在多能干细胞中，由 H3K27me3 标记的 poised 增强子被认为在胚胎干细胞 (ESC) 分化过程中建立体细胞表达程序中发挥作用。然而， poised 增强子的功能相关性和作用机制尚不清楚。使用 CRISPR/Cas9 技术进行精确的基因缺失工程，我们证明 poised 增强子对于诱导主要的前脑神经调节因子是必需的。有趣的是，环状染色体构象捕获测序 (4C-seq) 显示， poised 增强子已经以多梳抑制复合物 2 (PRC2) 依赖性的方式与它们的靶基因在 ESC 中建立物理相互作用。PRC2 的缺失不会激活 poised 增强子或诱导其潜在的靶基因在未分化的 ESC 中；然而，PRC2 在分化的 ESC 中的缺失严重且特异性地损害了代表 poised 增强子靶标的主要前脑神经基因的诱导。总的来说，我们的工作揭示了多梳蛋白在通过赋予主要的前脑神经基因具有允许的调控拓扑结构来促进神经诱导方面的一个意外功能。
