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。该提案的主要目标是确定细胞相互作用如何决定胚胎发生过程中细胞，组织和器官的形状和组织。利用线虫C.作为一种可以结合遗传分析和活体成像的体内模型，我们已经开发了几种简单的实验系统来研究细胞相互作用如何调节组织和器官发育过程中的保守形态发生事件。在一个项目中，我们研究细胞接触如何诱导早期胚胎细胞的顶基极性。我们最近发现，粘附蛋白E-cadherin通过将破坏细胞粘附的RhoGAP PAC-1募集到细胞接触位点来诱导极性，并且还发现一种未识别的冗余途径有助于极化。我们将通过确定E-cadherin如何在细胞接触处积累，研究E-cadherin相互作用蛋白α-catenin如何招募PAC-1，并确定独立于E-cadherin极化细胞的冗余途径的组分来扩展这些发现。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。我们以前表明PAR-6是粘附连接成熟所必需的。为了确定它是如何做到这一点的，我们将克隆和表征突变，我们在遗传相互作用筛选中发现了这些突变，这些突变会影响连接的完整性。另外，我们将确定PAR蛋白和外囊复合物如何识别管腔结构域和直接囊泡运输到这些网站，以延长胞内管。在第三个项目中，我们研究了我们发现的一种新形式的细胞形态发生的机制-当内胚层细胞主动咬掉并消化由原始生殖细胞（PGCs）延伸的大裂片时发生的同类相食事件。这种形式的形态发生很可能在其他系统中被忽视，我们假设它对生殖细胞发育至关重要。我们发现Rho GT3 Rac诱导肌动蛋白在PGC叶的基部积累，并且是内胚层细胞切断这些结构所必需的。我们将确定Rac和肌动蛋白如何在叶切断中起作用，我们将描述几个额外的基因，我们在遗传筛选中确定，这是叶切断所必需的。总之，我们的研究结果将揭示细胞，组织和器官在发育过程中如何改变形状并组织成功能单位的新的基本见解，并将为理解以缺陷细胞-细胞相互作用为特征的疾病（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.