Dnd1 and repression of transcription in primordial germ cells

 描述(申请人提供)：生殖系是唯一能够产生配子的细胞系。生殖系发育缺陷会导致生殖细胞减少或消除，并最终导致人类不育，这会影响10%-15%的夫妇。生殖细胞发育在胚胎发育的早期就开始了。原始生殖细胞(PGCs)分化后，转录在PGCs中被瞬时抑制。这与体细胞谱系的发展形成了鲜明的对比，体细胞谱系的发展往往依赖于复杂转录程序的激活。这种短暂的全基因组转录抑制状态的建立对于生殖系发育的早期阶段至关重要，因为它阻止了PGCs对指定体细胞命运的周围信号的反应。在PGC发育的早期阶段，如果不能抑制转录，会导致PGCs的体细胞分化和凋亡，最终导致生殖细胞从胚胎中消失。因此，了解这种全球转录抑制状态是如何在PGCs中建立的，与人类生殖健康高度相关。我们的初步研究表明，DND1，一种脊椎动物生殖细胞发育所需的RNA结合蛋白，在建立PGC全基因组转录抑制状态中发挥着重要作用。我们发现，DND1蛋白被自噬迅速降解，使其本质上不稳定。在发育过程中，Dnd1在正确的时间和正确的位置表达，并且是抑制PGCs转录的Nanos1表达所必需的。我们假设PGCs的全基因组转录抑制状态是通过精确调控Dnd1蛋白的表达而建立的。具体目标是：目标1：确定DND1是否是PGCs转录抑制的中心上游调节因子。目的2：探讨DND1调控Nanos1翻译的机制。目的3：确定依赖自噬的DND1翻转对生殖系发育是否重要。

 DESCRIPTION (provided by applicant): The germline is the only cell lineage capable of giving rise to the gametes. Defective germline development results in reduction or elimination of germ cells and ultimately causes infertility in humans, which affects 10- 15% of couples. Germ cell development begins early during embryonic development. After specification of primordial germ cells (PGCs), transcription is transiently repressed in PGCs. This is in stark contrast to the development of somatic lineages, which often relies on the activation of complex transcriptional programs. The establishment of such a transient genome-wide transcriptionally repressive state is critically important for early stages of the germline development, because it prevents PGCs from responding to surrounding signals that specify somatic cell fates. Failure to repress transcription during early stages of PGC development causes somatic differentiation and apoptosis of PGCs, which eventually leads to elimination of germ cells from the embryo. Understanding how this global transcriptionally repressive state is established in PGCs thus is highly relevant to human reproductive health. Our preliminary studies suggest that Dnd1, a RNA-binding protein required for vertebrate germ cell development, plays an essential role in establishing the genome- wide transcriptionally repressive state in PGCs. We found that Dnd1 protein is rapidly degraded by autophagy, making it intrinsically unstable. During development, Dnd1 is expressed at the right time and in the right place, and is required for the expression of Nanos1, which represses transcription in PGCs. We hypothesize that the genome-wide transcriptionally repressive state in PGCs is established through precisely regulated expression of Dnd1 protein. Specific aims are: Aim 1: To determine if Dnd1 is a central upstream regulator of the transcriptional repression in PGCs. Aim 2: To investigate the mechanisms through which Dnd1 regulates nanos1 translation. Aim 3: To determine whether autophagy- dependent Dnd1 turnover is important for the germline development.