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，这些分裂用合子核填充卵子的体积，克隆地分离卵子的S发育潜力，并将子细胞的体积减少到体细胞的体积。在动物细胞中，卵裂沟通常被认为是一个微丝依赖的过程。然而，最近，达尼尔奇克博士在非洲爪蛙卵的早期分裂沟中发现了一种新的含有微管的阵列。这种结构由许多粗的、短束的放射状排列的乙酰化微管组成，这些微管从所有分裂沟的收缩环附近发出，直到中期囊胚期。达尼尔奇克博士假设，微管阵列的功能是将膜小泡聚集到沟槽前沿的新膜形成部位。由于所有受体介导的细胞-细胞相互作用依赖于细胞之间沉积的膜的组成，很明显，定向的膜沉积和内陷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。这一建议的具体目的是：1)通过共聚焦免疫细胞化学进一步详细地研究FMA的组成，以确定FMA是否作为一种新的MT结构出现；2)了解FMA和中间区中MTS的极性；3)测试新的分裂膜附近的囊泡运动是否依赖于完整的FMA；以及4)测试已知的MT马达蛋白在新膜递送中的作用。

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.