Abl Regulates Planar Polarized Junctional Dynamics through β-Catenin Tyrosine Phosphorylation

Interactions between epithelial cells are mediated by adherens junctions that are dynamically regulated during development. Here we show that the turnover of beta-catenin is increased at cell interfaces that are targeted for disassembly during Drosophila axis elongation. The Abl tyrosine kinase is concentrated at specific planar junctions and is necessary for polarized beta-catenin localization and dynamics. abl mutant embryos have decreased beta-catenin turnover at shrinking edges, and these defects are accompanied by a reduction in multicellular rosette formation and axis elongation. Abl promotes beta-catenin phosphorylation on the conserved tyrosine 667 and expression of an unphosphorylatable beta-catenin mutant recapitulates the defects of abl mutants. Notably, a phosphomimetic beta-catenin(Y667E) mutation is sufficient to increase beta-catenin turnover and rescue axis elongation in abl deficient embryos. These results demonstrate that the asymmetrically localized Abl tyrosine kinase directs planar polarized junctional remodeling during Drosophila axis elongation through the tyrosine phosphorylation of beta-catenin.