Cleavage in Xenopus Development

A.项目概述在一个新的生物体的生命中最关键的阶段之一是胚胎分裂，一系列快速，同步的细胞分裂，填充受精卵的体积与合子核，克隆分离其发育潜力，并减少细胞体积的体细胞。卵裂在几个方面不同于体细胞有丝分裂，特别是它的同步性，快速性，并依赖于母体合成的components.The长期目标的拟议研究是了解胚胎卵裂在青蛙非洲爪蟾的发展中的形态发生作用。在卵裂过程中，大量的新的基底外侧膜通过局部胞吐作用沿着早期卵裂面沉积。随着它的扩张，这种新膜进行了许多对胚胎发育很重要的综合活动，包括沿顶侧-基底侧边界沿着建立紧密连接、维持细胞间粘附和囊胚腔的形成。最近的工作揭示了一个爆发的扩张活动沿着扩展的卵裂沟，包括延伸的丝状伪足，形成附着点跨越沟隙。本研究的目的是验证细胞的增殖活性对于依赖钙粘蛋白的卵裂球粘附是重要的，以及新建立的顶侧和基底侧膜结构域是由膜和底层皮层从沟底向外流动到顶侧-基底侧边界来维持的这一观点。本实验将促进我们对特定细胞生物学功能各自发育作用的理解，包括细胞-细胞粘附、扩散活动和关键早期形态发生过程中的皮质流动。在更广泛的背景下，研究活动将为对早期两栖动物发育的基本细胞生物学感兴趣的研究生，本科生和高中生提供有用的培训基地。

A. PROJECT SUMMARYOne of the most critical phases in the life of a new organism is embryonic cleavage, a series of rapid, synchronous cell divisions that populates the fertilized egg's volume with zygotic nuclei, clonally segregates its developmental potential, and reduces cell volume to that of somatic cells. Cleavage differs in several ways from somatic-cell mitosis, particularly by its synchrony, rapidity, and reliance on maternally synthesized components.The long-term objective of the proposed research is to understand the morphogenetic role of embryonic cleavage in the development of the frog Xenopus laevis. During cleavage, a large amount of new basolateral membrane is laid down along the early cleavage planes by localized exocytosis. As it expands, this new membrane carries out a number of integrated activities that are important for embryonic development, including establishment of tight junctions along the apical-basolateral boundaries, maintenance of cell-cell adhesion, and formation of the blastocoel. Recent work reveals a burst of protrusive activity along the expanding cleavage furrow, including the extension of filopodia that form attachment sites across the furrow gap. The aims of the proposed research are to test the idea that the protrusive activity is important for cadherin-dependent blastomere adhesion, and that the newly established apical and basolateral membrane domains are maintained by flow of membrane and underlying cortex from the furrow base outward to the apical-basolateral boundary.The proposed experiments will advance our understanding of the respective developmental roles of specific cell-biological functions, including cell-cell adhesion, protrusive activity, and cortical flow in a key early morphogenetic process. In a broader context, the research activities will provide a useful training ground for graduate students, undergraduates and high school students interested in the basic cell biology of early amphibian development.