协同性迁移是细胞迁移的一种形式，是由多个细胞粘附在一起成为细胞簇或细胞层进行迁移。它的一个重要特征是细胞簇在迁移过程中既要保持前后端的极性，又要维持类似上皮细胞的顶基端极性。这个上皮极性在协同迁移中扮演了什么角色？目前所知不多。我们这一申请课题将在果蝇卵子发生过程中集中研究关键上皮极性复合物具体是通过什么分子机制来促进边界细胞簇进行协同迁移的。是通过它们在细胞-细胞间的信号传递功能？还是通过直接调控细胞的actin细胞骨架组装和片伪足延伸？这些问题将在本课题试图回答。另外，我们将首次在边界细胞内系统地把四个上皮极性复合物的十二个成员有针对性的在顶基端与前后端进行详细定位分析。我们预计这一工作的结果将会给上皮极性复合物在发育过程中协同迁移的功能提供一个较明确的定论。最后，因为边界细胞簇具有类似肿瘤簇转移的迁移特性，我们的研究结果也将间接地增加对肿瘤细胞协同迁移的分子机制的了解。

Collective migration is a form of cell migration, in which multiple cells adhere to each other and migrate collectively as a cluster or sheet. An outstanding characteristic of collective migration is that a cell cluster needs to establish front-back polarity while maintaining an epithelial-like apical-basal polarity during the course of migration. The mechanistic role of epithelial polarity during collective migration is currently not well understood. In this proposed study, we focus on understanding the underlying mechanism of how key epithelial polarity complexes promote collective migration of border cell cluster during Drosophila oogenesis. We attempt to test whether epithelial polarity complexes promote collective migration through their cell-cell signaling functions at the junctions or by directly regulating actin assembly and lamellipodial protrusion at the leading edge of the cluster. In addition, we will analyze the distribution patterns of individual molecules (a total of 12 components from 4 epithelial polarity complexes) in details along both apical-basal axis and front-back axis. We anticipate that results from this proposed study will elucidate the mechanistic roles of epithelial polarity during collective migration in a developmental context. Lastly, because of the similar migratory and invasive nature between border cell cluster and some tumor cell clusters, results from our proposed study will also indirectly help contribute to the understanding of molecular mechanism underlying collective migration of tumor cells.