Roles of Chromatin Regulation in Embryonic Stem Cell Self-Renewal

描述(由申请人提供)： 摘要胚胎干细胞(ESCs)表现出两个独特的特征，使其成为开发退行性疾病治疗方法的潜在工具。首先，胚胎干细胞具有分化为任何细胞类型的能力，这一特性被称为多能性。其次，胚胎干细胞有能力在培养中以未分化的状态无限增殖，而不积累遗传或 表观遗传变化，这是一个称为自我更新的过程。胚胎干细胞的自我更新或分化的决定最终由几个被称为ESC“主调节因子”的转录因子以及染色质结构的调节因子控制。近年来，ESC主要调控因子的基因靶点和功能得到了更好的理解。相比之下，ESC自我更新或多能性所需的大多数染色质调节剂的靶点和基因调控功能尚不清楚。本项目旨在了解三个在胚胎干细胞自我更新和多能性中起关键作用的染色质调节复合体的功能和作用机制。Tip60-P400复合体具有赖氨酸乙酰转移酶(KAT)和核小体重塑活性，在自我更新的ESCs中具有沉默分化诱导基因的功能。考虑到大多数KAT的主要功能是激活转录，以及Tip60-P400复合体在体细胞基因激活中的已知作用，这一发现是意想不到的。我们将研究Tip60-P400复合体沉默小鼠ESCs分化基因的机制，并确定这种活性在分化过程中是如何调节的。此外，我们最近发现，另外两个染色质调节复合体NuRD和BAF相反地调节一组重叠的靶基因，由于这种对立，这些基因的表达水平适中。我们将研究这种对立的机制，它在维持多能性状态中的重要性，以及它在胚胎干细胞分化中的作用。

DESCRIPTION (provided by applicant): Abstract Embryonic stem cells (ESCs) exhibit two unique features that make them potential tools for the development of therapies for degenerative diseases. First, ESCs have the capacity to differentiate into any cell type, a property termed pluripotency. Second, ESCs have the ability to proliferate indefinitely in culture in an undifferentiated state without accumulating genetic or epigenetic alterations, a process called self- renewal. The decision of ESCs to self-renew or differentiate is ultimately controlled by several transcription factors called ESC "master regulators", along with regulators of chromatin structure. In recent years, the gene targets and functions of the ESC master regulators have become better understood. In contrast, the targets and gene regulatory functions of most chromatin regulators required for ESC self-renewal or pluripotency are unknown. This project aims to understand the functions and mechanisms of action of three chromatin regulatory complexes with crucial functions in ESC self-renewal and pluripotency. The Tip60- p400 complex has lysine acetyltransferase (KAT) and nucleosome remodeling activities, and functions to silence differentiation-induced genes in self-renewing ESCs. This finding was unexpected, given the fact that most KATs function primarily in activation of transcription, and the documented roles of Tip60-p400 complex in gene-activation in somatic cells. We will examine the mechanism by which the Tip60-p400 complex silences differentiation genes in murine ESCs, and determine how this activity is regulated during differentiation. In addition, we recently found that two additional chromatin regulatory complexes, NURD and BAF, oppositely regulate an overlapping set of target genes, which are expressed at moderate levels as a result of this opposition. We will examine the mechanisms underlying this opposition, its importance in the maintenance of the pluripotent state, and its function in ESC differentiation.