Collaboration of chromatin remodeling and signaling pathways in pluripotency

 描述(由申请人提供)：多能干细胞(PSCs)具有自我更新的显著特性，并能够在正确的刺激下产生分化的细胞类型。PSCs可以来自胚胎(胚胎干细胞-ESCs)或来自体细胞的转录因子的过度表达(诱导多能干细胞-IPSCs)。重新编程到IPSC状态的过程很慢--大约需要2-3周的时间才能完成，而且效率低下--最多只有5%的初始人口完成了这一过程。PSCs的特性是通过控制阻止其分化的信号通路来维持的。从本质上讲，核心转录因子有一个自动调节的LOP，它与表观基因组相互作用，维持多能性状态。虽然通常情况下，修改表观基因组会影响重新编程，但特定的染色质修饰物和信号通路如何机械地与多能性调控网络结合在一起在很大程度上是未知的。我们发现，在重新编程中间体中，染色质调节器和信号调制器的联合作用协同允许以非常高的效率获得IPSC状态。利用这个系统，我们已经确定，关键表观遗传标记的时间擦除伴随着多能性基因的转录激活和关键生长因子信号基因的下调。在这个方案中，我们将研究多能性获得过程中表观基因组和信号的相互作用机制，目的如下：1)阐明组蛋白去甲基酶对多能性的不同贡献机制；2)确定多能性获得过程中表观遗传标记的相互依赖；3)确定基因抑制在重编程过程中的作用机制。在这项提案中，我们将对重新编程的机制以及达到IPSC状态所必须克服的障碍有一个重要的了解。这些信息对于加快这一进程和提高效率至关重要，因此将在将IPSCs用于治疗目的方面产生很大影响。

 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.