Regulation of Germ Cell Fate During Embryogenesis

描述(由申请人提供)：这个项目的长期目标是描述生殖细胞和体细胞的区别机制，这是发育生物学中的一个基本问题。在线虫中，在第一次分裂之前，通过细胞质中蛋白质和蛋白质/RNA复合体的不对称分配，在受精卵中建立了体细胞-种系不对称。细胞质的分裂是由保守的极性调节蛋白(PAR蛋白)调控的，PAR蛋白不对称地定位在受精卵皮质中。这项提议的目标是揭示大脑皮层的PAR活动如何调节细胞质中的极性。特殊目的I(SA1)将集中于将RNA结合蛋白MEX-5分离到前部细胞质的机制。初步数据表明，MEX-5的不对称性依赖于PAR-1的磷酸化，PAR-1是一种位于后部皮质的激酶，它增加了MEX-5在后部细胞质的局部扩散。SA2将专注于生殖系决定基因PIE-1，它分离到后部，与MEX-5相对，并以更陡峭的梯度分离。我们将研究PIE-1如何整合皮质和细胞质线索以形成明显的梯度。最后，SA3将重点介绍将P颗粒定位到后方的机制。P颗粒是生殖系特有的进化保守的RNA-蛋白质复合体。我们发现了一种新的P颗粒成分PPTR-1，用于P颗粒在有丝分裂过程中的完整性；我们的初步发现表明，P颗粒的种系特异性取决于调节的组装，不需要细胞质分裂。我们将使用生化、遗传和活显微镜方法的组合来检验这些假设，并确定涉及的基因和生化相互作用。与其他研究良好的胚胎极性模型不同，我们的系统不依赖于预先定位的RNA来产生不对称，从而为我们提供了独特的机会来探索直接分离细胞质中蛋白质的机制。

DESCRIPTION (provided by applicant): The long-term goal of this project is to characterize the mechanisms that distinguish germ cells from somatic cells, a fundamental problem in developmental biology. In C. elegans, soma- germline asymmetries are established in the zygote before the first division, through the asymmetric partitioning of proteins and protein/RNA complexes in the cytoplasm. Cytoplasmic partitioning is regulated by conserved polarity regulators (PAR proteins), which localize asymmetrically in the zygote cortex. The goal of this proposal is to uncover how PAR activity at the cortex regulates polarity in the cytoplasm. Specific Aim I (SA1) will focus on the mechanisms that segregate the RNA-binding protein MEX-5 to the anterior cytoplasm. Preliminary data suggest that MEX-5 asymmetry depends on phosphorylation by PAR-1, a kinase on the posterior cortex, which increases MEX-5 diffusion locally in the posterior cytoplasm. SA2 will focus on the germline determinant PIE-1, which segregate to the posterior, opposite MEX-5 and in a steeper gradient. We will investigate how PIE-1 integrates both cortical and cytoplasmic cues to form a distinct gradient. Finally, SA3 will focus on the mechanisms that localize P granules to the posterior. P granules are evolutionarily conserved RNA-protein complexes specific to the germline. We have discovered a new P granule component PPTR-1 for P granule integrity during mitosis; our initial findings suggest that the germline specificity of P granules depends on regulated assembly and does not require cytoplasmic partitioning. We will use a combination of biochemical, genetic, and live microscopy approaches to test each of these hypotheses, and identify the genes and biochemical interactions involved. Unlike other well-studied embryonic polarity models, our system does not rely on pre-localized RNAs to generate asymmetry, and thus gives us the unique opportunity to explore the mechanisms that directly segregate proteins in the cytoplasm.