Cadherin-based Actin Assembly in the Xenopus Embryo

描述(申请人提供)：这项建议测试了一种假设，即经典钙粘附素除了在细胞-细胞黏附中的已知作用外，还通过控制皮质肌动蛋白的组装来控制脊椎动物胚胎中的形态发生组织运动。钙粘附素是一个蛋白质大家族，在胚胎形成的不同组织中以不同的组合表达。我们认为，不同钙粘附素的结合，以及它们表达的不同细胞环境，共同产生具有不同运动性和粘附性的皮质肌动蛋白网络。这导致了胚胎中出现的组织形状的特征差异。这一假说得到了广泛的初步数据和已发表的工作的支持，将在非洲爪哇早期胚胎外胚层中进行测试，该外胚层起源于囊胚的动物区域。我们以前已经证明，囊胚中的皮质肌动蛋白细丝网络对于整个胚胎的整体形状和硬度是必不可少的，它需要细胞表面C-钙粘蛋白的表达。随着外胚层的分化，神经性和非神经性外胚层表达不同的钙粘附素组合，这些表达的变化伴随着组织运动的剧烈变化。我们将通过操纵单个钙粘附素或组成结构域在错误组织中的表达来检验中心假设，比较与它们结合的肌动蛋白组装蛋白，并测试那些与不同钙粘附素有差异结合的蛋白的功能。在以前的工作中，我们证明了磷脂信号对于胚泡中皮质肌动蛋白的组装是必不可少的。我们将检验这一假说，即在来自胚泡的外胚层组织中，肌动蛋白的组装仍然需要它。 公共卫生相关性：该项目旨在确定协调细胞黏附和细胞运动的分子机制，作为人体器官的第一形式。许多出生缺陷是由细胞黏附和组织运动失败引起的，因此对它们发生方式的分子理解是重要的和及时的。

DESCRIPTION (provided by applicant): This proposal tests the hypothesis that the classical cadherins, in addition to their known role in cell-cell adhesion, also control morphogenetic tissue movements in the vertebrate embryo, by controlling the assembly of cortical actin. Cadherins are a large family of proteins, which are expressed in different combinations in different tissues of the embryo as they form. We propose that the combination of different cadherins, and the different cellular contexts in which they are expressed, together generate cortical actin networks with different motile and adhesive properties. This results in the characteristic differences in tissue shapes that arise in the embryo. This hypothesis, which is supported by extensive preliminary data and published work, will be tested in the early Xenopus embryonic ectoderm, which arises from the animal region of the blastula. We have shown previously that the cortical actin filament network in the blastula, which is essential for overall shape and rigidity of the whole embryo, requires the expression of C-cadherin on the cell surface. As the ectoderm differentiates, the neural and non-neural ectoderm express different combinations of cadherins, and dramatic changes in tissue movement accompany these changes in expression. We will test the central hypothesis by manipulating the expression of individual cadherins, or component domains, in the wrong tissues, compare the actin assembly proteins that bind to them, and test the functions of those that bind differentially to different cadherins. In previous work, we showed that signaling by phospholipids is essential for cortical actin assembly in the blastula. We will test the hypothesis that it continues to be required for actin assembly in the ectodermal tissues derived from the blastula. PUBLIC HEALTH RELEVANCE: This project aims to identify the molecular mechanisms that coordinate cell adhesion and cell motility as the organs of the body first form. Many birth defects are caused by failure of cell adhesion and tissue movement, and so a molecular understanding of the way they occur is important and timely.