Cleavage in Xenopus Development

受精卵通过一系列快速、同步的细胞分裂或卵裂成为多细胞细胞，卵裂的作用是用合子核填充卵子的体积，克隆分离卵子的发育潜力，并将子细胞的体积缩小到体细胞的体积。在动物细胞中，一般认为卵裂形成是一个依赖微丝的过程。然而，最近，丹尼尔奇克博士在非洲爪蟾（Xenopus laevis）卵的早期卵裂沟中发现了一种新的含有微管的阵列。这种结构由许多粗而短的放射状排列的乙酰化微管束组成，这些微管从所有卵裂沟的收缩环附近散发出来，直到囊胚中期。Danilchik博士假设，微管阵列的功能是将膜泡招募到沟前缘新膜形成的位置。由于所有受体介导的细胞-细胞相互作用都依赖于细胞间沉积膜的组成，因此很明显，定向膜沉积和侵入在早期发育事件中具有潜在的重要作用，例如初级组织层的指定。本提案的具体目的是：1)通过共聚焦免疫细胞化学进一步详细检查FMA的组成，以确定FMA是否作为新生MT结构出现；2)了解FMA和中间区的mt极性；3)测试新劈裂膜附近的囊泡运动是否依赖于完整的FMA；4)检测已知MT运动蛋白在新膜传递中的作用。

Fertilized eggs become multicellular through a series of rapid, synchronous cell divisions, or cleavages, that serve to populate the egg's volume with zygotic nuclei, clonally segregate the egg' s developmental potential, and reduce daughter cells' volume to that of somatic cells. In animal cells, cleavage furrowing is generally recognized to be a microfilament-dependent process. Recently, however, Dr. Danilchik discovered a novel microtubule-containing array in the early cleavage furrows in eggs of the frog Xenopus laevis. This structure consists of numerous thick, short bundles of radially arranged, acetylated microtubules that emanate from the vicinity of the contractile ring of all cleavage furrows until the midblastula stage. Dr. Danilchik hypothesizes that the microtubule array functions to recruit membrane vesicles to the site of new membrane formation at the furrow's leading edge. Since all receptor-mediated, cell-cell interactions depend on the composition of the membranes deposited between cells, it is clear that the directed membrane deposition and ingression have potentially significant roles in events of early development, such as specification of the primary tissue layers. The specific aims of this proposal are: 1) to examine in further detail the composition of the FMA via confocal immunocytochemistry, to determine whether the FMA arises as a de novo MT structure; 2) to learn the polarity of MTs in the FMA and the midzone; 3) to test whether vesicle movements in the vicinity of the new' cleavage membrane depend on an intact FMA; and 4) to test the role of known MT motor proteins in new membrane delivery.