The role of cell interactions in shaping development

 描述(由申请人提供)：细胞之间的相互作用影响胚胎发育的许多关键方面。这项建议的主要目标是确定在胚胎发育过程中细胞相互作用如何决定细胞、组织和器官的形状和组织。利用线虫作为遗传分析和活体成像相结合的体内模型，我们开发了几个简单的实验系统，以研究细胞相互作用如何随着组织和器官的发育而调节保守的形态发生事件。在一个项目中，我们研究了细胞接触如何在早期胚胎细胞中诱导根尖基极。我们最近发现，黏附蛋白E-cadherin通过将打破对称性的RhoGAP PAC-1招募到细胞接触位点来诱导极化，并发现一条未知的冗余途径有助于极化。我们将通过确定E-钙粘附素如何在细胞接触处积累，研究E-钙粘附素相互作用蛋白α-catenin如何招募pac-1，以及确定独立于E-钙粘附素极化细胞的冗余路径的组件来扩展这些发现。在第二个项目中，我们研究了PAR极性蛋白如何调节上皮细胞连接和管的形成。我们以前已经证明，PAR-6是黏附连接成熟所必需的。为了确定它是如何做到这一点的，我们将克隆并鉴定影响连接完整性的突变，这些突变是我们在基因相互作用屏幕上发现的。另外，我们将确定PAR蛋白和外囊复合体如何识别管腔结构域，并将囊泡运输到这些位置以延伸细胞内管。在第三个项目中，我们研究了我们发现的一种新的细胞形态发生的机制-当内皮细胞主动咬掉并消化由原始生殖细胞(PGC)延伸的大叶时发生的一种同类事件。这种形式的形态发生很可能在其他系统中被忽视了，我们假设它对生殖细胞的发育至关重要。我们发现Rho GTPase Rac诱导肌动蛋白在PGC小叶的底部积聚，并且是内皮细胞破坏这些结构所必需的。我们将确定Rac和肌动蛋白如何在叶切除中发挥作用，我们还将鉴定其他几个基因，这些基因是我们在基因筛查中确定的，它们对叶切除是必不可少的。总之，我们的发现将揭示细胞、组织和器官在发育过程中如何改变形状和组织成功能单位的新的基本见解，并将为理解以细胞-细胞相互作用缺陷为特征的疾病(如癌症)的分子基础提供基础。

 DESCRIPTION (provided by applicant): Interactions between cells influence many critical aspects of embryonic development. The broad goal of this proposal is to determine how cell interactions determine the shape and organization of cells, tissues, and organs during embryogenesis. Using the nematode C. elegans as an in vivo model where genetic analysis and live imaging can be combined, we have developed several simple experimental systems to investigate how cell interactions regulate conserved morphogenetic events as tissues and organs develop. In one project, we investigate how cell contacts induce apicobasal polarity in early embryonic cells. We recently showed that the adhesion protein E-cadherin induces polarity by recruiting the symmetry-breaking RhoGAP PAC-1 to cell contact sites, and also discovered that an unidentified redundant pathway contributes to polarization. We will extend these findings by determining how E-cadherin accumulates at cell contacts, investigating how the E-cadherin interacting protein α-catenin recruits PAC-1, and identifying components of the redundant pathway that polarizes cells independently of E-cadherin. In a second project, we investigate how PAR polarity proteins regulate the formation of epithelial cell junctions and tubes. We showed previously that PAR-6 is required for the maturation of adherens junctions. To determine how it does so, we will clone and characterize mutations, which we identified in a genetic interaction screen, that affect junction integrity. Separately, we will determine how PAR proteins and the exocyst complex recognize lumenal domains and direct vesicle trafficking to these sites to extend intracellular tubes. In a third project, we investigate the mechanisms of a novel form of cellular morphogenesis we discovered - a cannibalistic event that occurs when endodermal cells actively bite off and digest large lobes extended by primordial germ cells (PGCs). Such a form of morphogenesis is likely to have been overlooked in other systems, and we hypothesize that it is critical for germ cell development. We found that the Rho GTPase Rac induces actin to accumulate at the base of PGC lobes and is required for the scission of these structures by endodermal cells. We will determine how Rac and actin function in lobe scission, and we will characterize several additional genes, which we identified in a genetic screen, that are essential for lobe scission. Together, our findings will reveal new, basic insights into how cells, tissues, and organs change shape and organize into functional units during development, and will provide a foundation for understanding the molecular basis of diseases characterized by defective cell-cell interactions, such as cancer.