Regulatory mechanisms required for DE-cadherin function in cell migration and other types of adhesion

Cadherin-mediated adhesion can be regulated at many levels, as demonstrated by detailed analysis in cell lines. We have investigated the requirements for Drosophila melanogaster epithelial ( DE) cadherin regulation in vivo. Investigating D. melanogaster oogenesis as a model system allowed the dissection of DE-cadherin function in several types of adhesion: cell sorting, cell positioning, epithelial integrity, and the cadherin-dependent process of border cell migration. We generated multiple fusions between DE-cadherin and alpha-catenin as well as point-mutated beta-catenin and analyzed their ability to support these types of adhesion. We found that ( 1) although linking DE- cadherin to alpha-catenin is essential, regulation of the link is not required in any of these types of adhesion; ( 2) alpha-catenin is required only to link DE- cadherin to alpha-catenin; and ( 3) the cytoplasmic domain of DE- cadherin has an additional specific function for the invasive migration of border cells, which is conserved to other cadherins. The nature of this additional function is discussed.