β-Catenin: A Key Player in Both Cell Adhesion and Wnt Signaling

β-catenin was discovered independently by researchers investigating the molecular basis of cadherin cell adhesion in vertebrate epithelial cells and through genetic screens in Drosophila for mutants with defective embryonic segmentation , which was subsequently discovered to be a Wnt dependent signaling event. A major role for β-catenin is at the cell-cell adhesion junctions between epithelial cells. These junctions are required to allow individual cells to stick to one another to form an epithelial sheet, and regulate and coordinate the behavior of individual epithelial cells during tissue development and morphogenesis. Several lines of evidence place β-catenin in the Wnt signaling pathway. Screens for embryonic lethal mutations led to the identification of Armadillo (Arm), the Drosophila homolog of β-catenin. The key to the ability of β-catenin to mediate more than one function lies in the regulation of its subcellular localization. Subfunctionalization of β-catenins has been reported for the planarian Schmidtea mediterranea.