C. elegans Gastrulation: a Model for Understanding Apical Constriction Mechanisms

描述(申请人提供)：心尖狭窄是一种细胞形状的改变，在不同的动物系统中驱动形态发生事件，包括脊椎动物的神经管形成。了解细胞收缩顶端区域的机制可以解决动物胚胎是如何形成的基本问题，并为未来诊断和预防人类神经管闭合缺陷奠定基础，神经管闭合缺陷是人类最常见和最严重的出生缺陷之一。这个项目的长期目标是了解力量如何在空间和时间上精确传递，以塑造发育中的生物体中的细胞和组织。将使用秀丽线虫作为示范系统来实现这一目标。线虫的原肠发育始于26-28细胞期，两个内胚层前体细胞(EPC)经历顶端收缩，从胚胎表面向内部移动。实验已经确定，肌动球蛋白收缩早在顶端区域开始收缩之前就开始了，直到后来顶端表面的边缘才开始变窄，与肌动球蛋白收缩相一致-这意味着两者之间的关键联系不是结构性的。这项提议的目的是了解细胞如何在体内发育环境中改变形状的核心机制。我们提出的实验充分利用了模型系统的优势，在模型系统中，可以识别相关的分子，并且可以通过组合各种实验工具来解开机制。该项目的目的是(1)剖析细胞顶端表面的边缘与先前存在的肌球蛋白收缩联系在一起的机制，从而触发细胞顶端结构域的收缩，(2)确定随着顶端收缩开始出现在顶端收缩细胞表面的蛋白质的作用，以及(3)通过识别和研究通过上述机制参与顶端收缩的新蛋白质，将遗传学研究与上述机制研究相结合。这些目标的成功完成将揭示根尖收缩的关键机制，这是一个重要的发育过程。这项工作有可能为细胞骨架机制的发育控制建立一个范例，建立一个启动发育细胞形状变化的新机制，并识别可能与不同动物系统的形态发生相关的新分子，包括人类发育中的神经管关闭。

DESCRIPTION (provided by applicant): Apical constriction is a cell shape change that drives morphogenetic events in diverse animal systems, including neural tube formation in vertebrates. An understanding of the mechanisms by which cells shrink their apical domains can address fundamental questions about how animal embryos are shaped, and it can lay a foundation for future diagnosis and prevention of human neural tube closure defects, which are among the most common and serious human birth defects. The long-term goal toward which this project contributes is to understand how forces are transmitted with spatial and temporal precision to shape cells and tissues in developing organisms. This goal will be approached using Caenorhabditis elegans as a model system. Gastrulation in C. elegans begins with two endodermal precursor cells (EPCs) undergoing apical constriction, moving from the embryo's surface to the interior, at the 26-28 cell stage. Experiments have determined that actomyosin contractions begin well before apical domains begin to shrink, and that only later do the edges of the apical surfaces begin to narrow in concert with actomyosin contractions-implying that the key connection between the two is not constitutive. The objective of this proposal is to understand the mechanisms that lie at the heart of how cells change shape in an in vivo, developmental context. Our proposed experiments capitalize on strengths of the model system, in which relevant molecules can be identified, and in which mechanisms can be unraveled by a combination of diverse experimental tools. The aims of the project are to (1) dissect the mechanisms by which the edges of the cells' apical surfaces become linked to pre-existing actomyosin contractions, triggering the shrinking of cells' apical domains, (2) determine the role of a protein that appears on the surfaces of apically constricting cells as apical constriction begins, and (3) integrate genetic studies with the mechanistic studies above, by identifying and studying new proteins involved in apical constriction by the mechanisms above. Successful completion of these aims will reveal key mechanisms underlying apical constriction, an important developmental process. The work has the potential to establish a paradigm for developmental control of cytoskeletal mechanisms, to establish a new mechanism for initiation of a developmental cell shape change, and to identify new molecules that could be relevant to morphogenesis in diverse animal systems including neural tube closure in human development.