Understanding the molecular mechanisms of Polycomb recruitment in ES cells and during cellular differentiation

PcG蛋白是一种染色质修饰物，能与DNA结合并诱导基因沉默。PCG蛋白控制着几个基本的生物学过程，包括干细胞的多能性和胚胎发育。这项建议的首要目标是确定在胚胎干细胞和细胞分化过程中，多梳抑制复合体2(PRC2)募集到染色质的分子机制。 同一个体中的分化细胞和未分化的多能干细胞具有相同的基因组序列，但PRC2结合位点不同。这表明，驱动PRC2与不同位点结合的机制必须超出DNA序列本身。 我们将首先利用体外分化技术，建立人类ES细胞、肝细胞(内胚层)和心肌细胞(中胚层)中正常PRC2结合部位的图谱。然后，我们将使用新定义的发育PRC2结合图谱来研究驱动PRC2招募的分子机制。总体而言，这项工作将使我们能够探索新的假设，关于驱动多能细胞中PRC2招募的基本过程的分子机制，以及这种机制在发育过程中如何变化。 我们研究计划的长期愿景是通过添加其他分化细胞和其他染色质修饰物和组蛋白标记来扩展我们的表观基因组图谱。这份图谱的制作将使我们有机会解决以前我们无法研究的关于调控表观基因组的想法，显著提高我们对细胞分化和哺乳动物发育过程的了解。本文提出的工作将对染色质生物学、干细胞生物学和细胞分化等多个生物学领域产生重大影响。

Polycomb group (PcG) proteins are chromatin modifiers that bind to DNA and induce gene silencing. PcG proteins control several essential biological processes including pluripotency in stem cells and embryonic development. The overarching goal of this proposal is to identify the molecular mechanism responsible for the recruitment of Polycomb Repressive Complex 2 (PRC2) to the chromatin in embryonic stem cells and during cellular differentiation. Differentiated cells and undifferentiated pluripotent stem cells in the same individual have the same genomic sequence, however, PRC2 binding sites varies. This suggests that the mechanisms driving PRC2 binding to different sites must be beyond the DNA sequence itself. We will first create an atlas of normal PRC2 binding sites in human ES cells, and in Hepatocyte (Endoderm) and Cardiomyocytes (Mesoderm) using in vitro differentiation. We will then use the newly defined atlas of developmental PRC2 binding to study the molecular mechanisms driving PRC2 recruitment. Overall, this work will allow us to explore novel hypotheses regarding the molecular mechanisms driving the fundamental process of PRC2 recruitment in pluripotent cells and how this changes during development. The long-term vision for our research program is to expand our epigenomic atlas through adding other differentiated cells and other chromatin modifiers and histone marks. The generation of this atlas will give us the opportunity to address ideas regarding the regulatory epigenome that previously we were not able to investigate, significantly improving our knowledge of the cellular differentiation and mammalian development processes. The work proposed here will have significant impacts on a number of biological fields including chromatin biology, stem cell biology and cellular differentiation.