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

描述（由申请人提供）：顶端收缩是一种细胞形状变化，在多种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。了解细胞收缩其顶端结构域的机制可以解决有关动物胚胎如何形成的基本问题，并且可以为未来诊断和预防人类神经管闭合缺陷奠定基础，这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是如何在空间和时间上精确地传递，以塑造发育中的生物体中的细胞和组织。这一目标将采用秀丽隐杆线虫作为模型系统。秀丽隐杆线虫的原肠胚形成开始于两个内胚层前体细胞（EPCs）在26-28细胞期进行顶端收缩，从胚胎表面向内部移动。实验已经确定，肌动球蛋白的收缩早在根尖结构域开始收缩之前就开始了，只是在后来，根尖表面的边缘才开始随着肌动球蛋白的收缩而缩小——这意味着两者之间的关键联系并不是构成性的。这一建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。我们提出的实验利用了模型系统的优势，其中可以识别相关分子，并且可以通过多种实验工具的组合来解开机制。该项目的目的是：(1)剖析细胞顶端表面边缘与先前存在的肌动球蛋白收缩联系起来的机制，从而触发细胞顶端结构域的收缩；(2)确定顶端收缩细胞开始收缩时出现在顶端收缩细胞表面的蛋白质的作用；(3)将遗传学研究与上述机制研究结合起来。通过以上机制鉴定和研究参与根尖收缩的新蛋白。成功完成这些目标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，建立一个发育细胞形状变化启动的新机制，并确定可能与多种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闭合。

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.