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

描述（由申请人提供）：顶端缩窄是一种细胞形状变化，可驱动不同动物系统中的形态发生事件，包括脊椎动物中的神经管形成。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，这是最常见和最严重的人类出生缺陷。该项目的长期目标是了解力是如何以空间和时间精度传递的，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。C.在26-28细胞阶段，两个内胚层前体细胞（EPCs）经历顶端收缩，从胚胎的表面移动到内部。实验已经确定，肌动球蛋白收缩开始之前，顶端域开始收缩，只有后来做的顶端表面的边缘开始缩小与肌动球蛋白收缩的音乐会，这意味着两者之间的关键连接不是组成。该提案的目的是了解细胞在体内发育环境中如何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，在模型系统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）剖析细胞顶端表面的边缘与预先存在的肌动球蛋白收缩相关联的机制，从而触发细胞顶端结构域的收缩，（2）确定当顶端收缩开始时出现在顶端收缩细胞表面上的蛋白质的作用，以及（3）将遗传研究与上述机制研究相结合，通过鉴定和研究上述机制参与顶端收缩的新蛋白质。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。这项工作有可能建立细胞骨架机制的发育控制范式，建立一个新的机制，启动一个发育细胞形状的变化，并确定新的分子，可能是相关的形态发生在不同的动物系统，包括在人类发育的神经管关闭。

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.