Genetic Silencing in Germline Maintenance and Function

描述(申请人提供)：成年生殖系有许多不同的功能，包括增殖，减数分裂联会和重组，母本和父本的mRNA和蛋白质合成，以及配子发生。它还具有多重义务，包括防止可移动的遗传元件(转座子)造成可遗传的遗传损害，防止生殖细胞分化为体细胞，以及建立可遗传的转录活动状态。在某种程度上，所有这些义务都是由压制机制履行的，这些机制采取行动压制或防止与这些义务背道而驰的不适当活动。生殖细胞抑制利用转录后抑制(例如，基于RNAi)和转录(例如，基于染色质)机制的组合来实现其目标。这些机制的一个主要靶点是X染色体，在线虫和哺乳动物中，X染色体在减数分裂过程中受到转录抑制，但在雄性减数分裂过程中完全失活。性染色体失活是由一个高度保守的过程介导的，在减数分裂过程中以未突触的染色质为目标，这可能是一种古老的基因组防御机制。我们了解了该机制的一些组成部分，并计划以线虫为模型系统进一步剖析其机制及其调控。在哺乳动物和蠕虫中，雄性X在胚胎中优先失活，这可能是它减数分裂沉默的结果。印记X失活是遗传印记的一个戏剧性的例子，人们对印记的建立知之甚少。我们还将使用在线虫中可用的遗传学、分子、生化和细胞学工具来剖析雄性X印记的机制。我们已经使用了这种生物可用的广泛工具来将它构建成一个研究生殖系抑制或沉默的优秀模式生物，并准备在这个遗传模型系统中剖析染色质在生殖细胞沉默、印记建立和基因组防御机制中的作用。在胚系中运作的表观遗传机制对于印记的建立和防止可遗传的基因突变是必不可少的，这两者对正常的人类健康和正常的人类发育都是至关重要的。

DESCRIPTION (provided by applicant): The adult germ line has many disparate functions, including proliferation, meiotic synapsis and recombination, maternal and paternal mRNA and protein synthesis, and gametogenesis. It also has multiple obligations, including preventing mobile genetic elements (transposons) from inflicting heritable genetic damage, preventing differentiation of the germ cells into somatic cells, and establishing heritable states of transcriptional activity. All of these obligations are met, to some extent, by repressive mechanisms that act to silence or prevent inappropriate activities that are counter to these obligations. Germ cell repression utilizes a combination of post-transcriptional repression (e.g., RNAi-based) and transcriptional (e.g., chromatin based) mechanisms to achieve its goals. A major target of these mechanisms is the X chromosome, which is transcriptionally repressed during meiosis in both sexes in C. elegans, but is fully inactivated during male meiosis in both worms and mammals. Sex chromosome inactivation is mediated by a highly conserved process that targets unsynapsed chromatin during meiosis, and is likely an ancient genome defense mechanism. We understand some of the components of the mechanism, and plan to further dissect the mechanism and its regulation using C. elegans as a model system. In both mammals and worms, the male X is "imprinted" for preferentially inactivation in embryos, and this is likely a consequence of its meiotic silencing. Imprinted X inactivation is a dramatic example of genetic imprinting, and little is understood about imprint establishment. We will also use the genetic, molecular, biochemical, and cytological tools available in C. elegans to dissect the mechanism of male X imprinting. We have used the extensive tools available for this organism to build it into an excellent model organism for studying germ line repression, or silencing, and are now poised to dissect the role of chromatin in germ cell silencing, imprint establishment and genome defense mechanisms in this genetic model system. Epigenetic mechanisms operating in the germ line are essential for the establishment of imprinting and the prevention of heritable genetic mutations, both of which are crucial for normal human health and normal human development.