Cleavage in Xenopus Development

A.项目总结新生物生命中最关键的阶段之一是胚胎分裂，这是一系列快速、同步的细胞分裂，用合子核填充受精卵的体积，克隆分离其发育潜力，并将细胞体积缩小到体细胞的体积。卵裂与体细胞有丝分裂在几个方面不同，特别是它的同步性、快速性和对母体合成成分的依赖。拟议的研究的长期目标是了解胚胎卵裂在非洲爪蛙发育过程中的形态发生作用。在卵裂过程中，由于局部胞吐作用，大量新的基侧膜沿早期的卵裂面沉积。随着它的扩张，这种新的膜进行了许多对胚胎发育非常重要的综合活动，包括沿着顶端-基底外侧边界建立紧密的连接，维持细胞与细胞的黏附，以及囊胚腔的形成。最近的研究揭示了沿着不断扩大的卵裂沟突起的活动，包括丝状足突的延伸，形成了跨越沟隙的附着地点。这项研究的目的是验证突起活动对钙粘附素依赖的卵裂球黏附的重要性，以及新建立的顶端和基底外侧膜域是通过膜和下层皮质从沟底向外向尖底外侧边界流动来维持的。拟议的实验将促进我们对特定细胞生物学功能的各自发育作用的理解，包括细胞-细胞黏附、突起活动和皮质流动在关键的早期形态形成过程中的作用。在更广泛的背景下，研究活动将为对两栖动物早期发育的基础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础。

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.