Polarization of the Drosophila Oocyte

[00:91254]实际上，所有的细胞都是极化的，为了执行它们的程序功能，需要极化。细胞获得、维持和精心设计极性的机制在进化过程中得到了很好的保存。一般来说，当不对称提示诱导肌动蛋白纤维局部重塑时，细胞极化开始于细胞外围，产生“肌动蛋白斑块”。gtpase的Rho家族成员被招募到这些斑块并激活二级信号分子，这些信号分子通过重组肌动蛋白和微管细胞骨架以及极化质膜和细胞膜内运输途径来传播细胞反应。越来越多的证据表明，反馈回路是建立在这一基本途径中，以加强和扩大反应。例如，上皮细胞中Rho活性的破坏导致细胞间接触的丧失，这意味着这些gtpase在维持最初招募和激活它们的相同粘附复合物方面发挥了作用。最近发现，膜循环途径的保守成员Rab11是果蝇卵母细胞微管组织和RNA定位所必需的，这似乎揭示了另一个这样的反馈回路。具体来说，Rab11响应不对称提示和Rho CTPase激活，使质膜极化，从而增强对不对称提示的接受，Rho GTPase激活和“下游”极化事件，如微管组织和RNA定位。本文描述了一种“候选基因”方法，旨在鉴定果蝇卵母细胞膜极性的标记物。特别是，一些粘附分子和其他蛋白质定义其他质膜系统的极性，将被免疫细胞化学检查不对称分布沿卵母细胞的质膜

0091254CohenVirtually all cells are polarized and need to be in order to carry out their programmed functions. The mechanisms by which cells acquire, maintain and elaborate polarity have been well conserved through evolution. In general, cell polarization begins at the cell periphery when an asymmetric cue induces local remodeling of the actin fibers, generating an "actin patch." Members of the Rho family of GTPases are recruited to these patches and activate secondary signaling molecules that propagate the cellular response by reorganizing the actin and microtubule cytoskeletons, and polarizing the plasma membrane and intracellular membrane trafficking pathways. There is a growing body of evidence that feedback loops are built into this basic pathway to reinforce and amplify the response. For example, disruption of Rho activity in epithelial cells causes a loss of cell-cell contacts, implicating these GTPases in the maintenance of the same adhesion complexes that recruit and activate them in the first place. The recent discovery that Rab11, a conserved member of the membrane recycling pathway, is required for microtubule organization and RNA localization in Drosophila oocytes would appear to reveal another such feedback loop. Specifically, it is proposed that Rab11, in response to an asymmetric cue and Rho CTPase activation, polarizes the plasma membrane, thereby enhancing reception of the asymmetric cue, Rho GTPase activation and "downstream" polarization events, such as microtubule organization and RNA localization. Here, a "candidate gene" approach is described that seeks to identify markers of Drosophila oocyte membrane polarity. In particular, a number of adhesion molecules and other proteins that define polarity of other plasma membrance systems will be examined immunocytochemically for asymmetric distribution along the oocyte's plasma me