Collaboration of chromatin remodeling and signaling pathways in pluripotency

 描述（由申请人提供）：多能干细胞（PSC）具有自我更新的显著特性，并且在暴露于正确的刺激后能够产生分化的细胞类型。PSC可以来源于胚胎（胚胎干细胞-ESC）或通过来自体细胞的转录因子的过表达（诱导多能干细胞-iPSC）。重新编程到iPSC状态的过程是缓慢的-需要大约2-3周才能完成并且效率低下-只有大约5%的起始群体完成该过程。PSC的特性是通过控制阻止其分化的信号通路来维持的。核心转录因子的自身调节作用与表观基因组相互作用以维持多能性状态。虽然通常已知修饰表观基因组影响重编程，但具体的染色质修饰剂和信号传导途径如何机械地与多能性调控网络接合在一起在很大程度上是未知的。我们已经发现，在重编程中间体中，染色质调节剂和信号传导调节剂的联合作用协同地允许以非常高的效率获得iPSC状态。使用该系统，我们已经确定，关键表观遗传标记的时间擦除与多能性基因的转录激活和关键生长因子信号传导基因的下调同时发生。在这个提议中，我们将研究多能性获得过程中表观基因组和信号传导之间的相互作用机制，其目的如下：1）阐明组蛋白去甲基化酶对多能性的差异贡献机制2）确定多能性获得过程中表观遗传标记的相互依赖性和3）定义重编程过程中基因阻遏的机制贡献。在这个提案中，我们将获得对重编程机制的重要理解，以及达到iPSC状态必须克服的障碍。这些信息对于加快这一过程和提高效率至关重要，因此对于将iPSC用于治疗目的具有很大影响力。

 DESCRIPTION (provided by applicant): Pluripotent stem cells (PSCs) have the remarkable properties of self-renewal and the capacity to generate differentiated cell types upon exposure to the correct stimulus. PSCs can be derived from the embryo (embryonic stem cells - ESCs) or by overexpression of transcription factors from somatic cells (induced pluripotent stem cells- iPSCs). The process of reprogramming to the iPSC state is slow- taking about 2-3 weeks to complete and inefficient - with only about a maximum of 5% of the starting population completing the process. The properties of PSCs are maintained extrinsically by controlling signaling pathways that prevent their differentiation. Intrinsically there is an auto regulatory lop of core transcription factors, which interacts with the epigenome to maintain the pluripotent state. While in general it is known that modifying the epigenome impacts reprogramming, how specific chromatin modifiers and signaling pathways mechanistically engage with the pluripotency regulatory network is largely unknown. We have found that in reprogramming intermediates, the combined action of a chromatin regulator and signaling modulator synergistically allowed the acquisition of an iPSC state at a very high efficiency. Using this system we have determined that, temporal erasure of key epigenetic marks occurs concomitant with both the transcriptional activation of pluripotency genes and down regulation of key growth factor signaling genes. In this proposal we will investigate the mechanism of interplay between the epigenome and signaling during the acquisition of pluripotency with the following aims: 1) To elucidate the mechanism of differential contribution of histone demethylases to pluripotency 2) To determine the interdependence of epigenetic marks during the acquisition of pluripotency and 3) To define the mechanistic contribution of gene repression during reprogramming. In this proposal we will gain a significant understanding of the mechanism of reprogramming and the barriers that have to be overcome to reach the iPSC state. This information is essential for expediting the process and increasing the efficiency and will therefore be highly impactful in translating the use of iPSCs for therapeutic purposes.