Unique Regulation of RNA Pol II During Primordial Germ Cell Specification

描述(由申请人提供)：生殖细胞谱系是基因组的守护者，是世代之间传递的遗传和表观遗传信息的守门人。生殖细胞的一个基本特征是其潜在的全能性：生成所有组织的固有能力。全能性是一种表观遗传特征--影响种系基因组表观遗传内容的过程不仅可能影响个体内的种系和体细胞发育，而且还可能影响后代的发育过程。我们的长期目标是了解在世代内和世代之间的生殖细胞周期中运行的表观遗传过程：即可遗传的表观遗传内容是如何建立的，它是如何被识别和解释的，以及随着生殖系在每个阶段的进展，它是如何重新编程的？我的实验室一直处于建立线虫作为研究这些过程的特殊模型的前沿，因为它拥有大量的遗传和分子力量，使得对生殖系周期的代内和跨代研究都是可行的。此外，线虫生殖细胞规范的过程与哺乳动物的规范非常相似。这些包括混合胞体/生殖系/胚胎干细胞(ESC)样期，延长的G2期细胞周期停滞，全基因组的表观遗传重编程，以及RNA Pol II的瞬时专门调节。事实上，在线虫中的观察刺激了对哺乳动物的研究，巩固了这些相似性。其中一个相似之处是拟议的研究重点：RNA Pol II在原始生殖细胞(PGC)指定过程中的独特调节。在许多动物中，包括蠕虫、苍蝇、青蛙和小鼠，有一段时间的RNA Pol II不活跃伴随着PGC规范。在所有物种中，这都被观察到是缺乏“伸长的RNA POLII磷酸表位”，即Ser2P。我们最近发现，在线虫中，有一种奇怪的出现在PGC规格的Ser2P上，它是瞬时的，并以一种与周围体细胞不同的方式受到激酶的调节。这种调节可能有助于生殖系全能性，或者是生殖系全能性的特殊特征，因为有报道表明，Ser2P在多能性干细胞中显示出独特的调节。我们准备确定在PGC指定过程中调节Pol II的机制，确定其在新生PGC中的基因组分布，并确定可能有助于早期和胚胎后生殖细胞发育功能的转录组。这将对生殖细胞发育的保守方面产生重要的见解，并为哺乳动物的类似研究提供进一步的范例。鉴于生殖系对于跨代基因组保护和表观遗传模式的绝对重要性，这些研究具有非常重要的意义，因为它们将揭示这些过程如何正常进行，以及为什么当它们被破坏时会导致人类先天性和生育缺陷。

DESCRIPTION (provided by applicant): The germ lineage is the guardian of the genome and gatekeeper of the genetic, and epigenetic, information that is passed between generations. An essential characteristic of germ cells is their underlying totipotency: the inherent capacity to generate all tissues. Totipotency is an epigenetic characteristic-- processes that affect the epigenetic content of the germ line genome not only have the potential to affect germ line and somatic development within an individual, but can also affect developmental processes in subsequent generations. Our long-term goal is to understand the epigenetic processes that operate during the germ cell cycle within and between generations: i.e., how is heritable epigenetic content is established, how is it recognized and interpreted, and how is it reprogrammed as the germ line progresses through each stage? My lab has been at the forefront of establishing the nematode C. elegans as an exceptional model for studying these processes, as it possesses numerous genetic and molecular strengths that make both intra- and trans-generational studies of the germ line cycle feasible. Furthermore, the process of germ cell specification in C. elegans is remarkably similar to specification in mammals. These include a mixed soma/germline/embryonic stem cell (ESC)-like phase, a prolonged G2-stage cell cycle arrest, genome-wide epigenetic reprogramming, and transient specialized regulation of RNA Pol II. Indeed, observations made in C. elegans have stimulated the investigations in mammals that have cemented these similarities. One of these similarities is the focus of the proposed research: the unique regulation of RNA Pol II during primordial germ cell (PGC) specification. In many animals, including worms, flies, frogs, and mice, there is a period of RNA Pol II inactivity that accompanies PGC specification. In all species this is observed as the absence of the "elongating RNA Pol II phospho-epitope", Ser2P. We have recently shown that in C. elegans, there is a curious appearance of Ser2P at PGC specification that is transient and regulated by kinases in a manner distinct from the surrounding somatic cells. Such regulation may contribute to, or be a special characteristic of, germ line totipotency as reports suggest Ser2P shows unique regulation in pluripotent stem cells. We are poised to identify the mechanisms that regulate Pol II during PGC specification, identify its genomic distribution in the nascent PGCs, and identify the transcriptome that may contribute to the functions of early and post-embryonic germ cell development. This will yield important insights into conserved aspects of germ cell development, and provide further paradigms for similar investigations in mammals. Given the absolute importance of the germ line for both trans-generational genome protection and epigenetic modes of inheritance, these studies are highly significant as they will inform how these processes proceed normally, and why when disrupted they lead to human congenital and fertility defects.