单个细胞在趋化迁移时，引导受体如何将胞外趋化因子的浓度差异转换或放大为细胞内的前-后端极性，这是细胞和发育生物学的一个关键但未解决的问题。当一群细胞进行集体迁移时，细胞群不仅要建立整体的前-后端极性，各个细胞内还需建立或维持内在的顶-基端和外-内侧极性。我们将利用一个体内集体细胞迁移系统-果蝇卵巢的边界细胞簇来研究以下几个方面: 引导受体是如何通过调控囊泡运输分子的极性分布来建立和维持前-后端极性的。顶端极性分子是否通过激活下游的Rac来调控前端actin聚合与片伪足的产生。磷脂PIP2和PIP3在外、内侧细胞膜的定位是否决定了外-内侧极性，并是否分别由上游的PI3K和PTEN来调控的。这三种不同的细胞极性是否相互作用。预计研究结果将为胞内极性信号放大机制和不同细胞极性在趋化性集体迁移中的功能提出新颖的思路。

During single cell’s chemotactic migration, how guidance receptor on the cell the membrane converts and amplifies the extracellular concentration gradient into intracellular front-back polarity is a key yet unsolved cell and developmental question. As a group of cells undergo collective migration, the group not only has to establish front-back polarity but also needs to establish and maintain inherent apical-basal and outside-inside polarities in each cell. We will use an established in vivo collective migration model system, the border cell cluster, in the context of Drosophila oogenesis. We plan to address the following questions in our proposal. First, how guidance receptor establish front-back polarity through its regulation of asymmetric trafficking. Second, does apical molecules regulate actin polymerization and lamellipodial protrusion by signaling through Rac. Third, does the outside and inside localization of the phospholipid PIP2 and PIP3 determines the outside-inside polarity, which is regulated by PI3K and PTEN respectively. Fourth, how do the three distinct polarities interact with each other. We expect the results from this proposed study will shed new light and provide evidence to the cell polarity amplifying mechanism and the functional roles for these distinct polarities during chemotactic collective migration.