Cleavage in Xenopus Development

Danilchik 96-31765 受精卵通过一系列快速、同步的细胞分裂或分裂而变成多细胞的，这些细胞分裂或分裂用于用合子核填充卵的体积，克隆分离卵的发育潜力，并将子细胞的体积减少到体细胞的体积。在动物细胞中，通常认为卵裂成沟是一个微生物学依赖性过程。然而，最近Danilchik博士在非洲爪蟾卵的早期卵裂沟中发现了一种新的含有微管的阵列。这种结构由许多厚的，短束的放射状排列的，乙酰化的微管，从附近的收缩环的所有卵裂沟，直到中囊胚阶段发出。Danilchik博士推测，微管阵列的功能是将膜囊泡募集到沟的前缘新膜形成的位置，也许还可以沿着沿着每个卵裂沟向内吸引一层厚厚的外周细胞质，这一过程被称为ingresson。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的膜的组成，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，例如初级组织层的特化。该建议的具体目的是进行：1）结构分析，以进一步定义沟的细胞骨架组织，2）功能研究，以了解膜沉积和侵入是如何完成的，和3）发育基因表达研究，其中囊泡递送或侵入将被局部抑制，以了解卵裂的发育意义。该项目的结果将有助于我们了解动物细胞如何分裂，这是细胞和发育生物学中最基本的问题之一。

Danilchik 96-31765 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, and perhaps also to draw a thick layer of peripheral cytoplasm inward along each cleavage furrow, a process known as ingresson. Since all receptormediated, 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 to carry out: 1) a structural analysis, to define further the cytoskeletal organization of the furrow, 2) functional studies, to understand how membrane deposition and ingression are accomplished, and 3) developmental gene-expression studies, in which vesicle delivery or ingression will be locally inhibited to learn the developmental significance of cleavage. Results from this project will contribute to our understanding of how animal cells divide, one of the most fundamental problems in Cellular and Developmental Biology.