Examining the Function of β-catenin at Adherens Junctions during Dorsal Closure and the Formation of the Ventral Epidermis in Drosophila

Adherens junctions (AJs) consist of Cadherin-Catenin Complexes (CCCs); each CCC contains DE-cadherin, p120catenin, β-catenin (Armadillo in Drosophila) and α-Catenin. The question addressed here was whether β-catenin functions primarily to physically link DE-cadherin to α-Catenin or it has additional regulatory function in AJ stability. Dorsal closure (DC) defects in cadherin-deficient embryos are partially rescued by fusion proteins that directly link DE-cadherin to α-Catenin without recruiting Armadillo/β-catenin to AJs. This suggests that Armadillo at AJs is important for DC apart from being a linker. However, ventral defects were completely rescued by the same chimeras, indicating that Armadillo/β-catenin has no essential regulatory function at AJs in the ventral epidermis. Lastly, DC defects in Armadillo/β-catenin-deficient embryos were only partially rescued by the expression of DE-cadherin α-Catenin chimeras perhaps due to compromised Wnt signalling. Therefore, Armadillo/β-catenin has a general essential function in linking DE-cadherin to α-Catenin but a tissue-specific role in controlling AJ dynamics.M.Sc