β-catenin is a multifunctional protein that acts both as a downstream mediator of the Wnt signalling pathway and as a core component of adherens junctions. It is also widely expressed during development. Consequently, dissecting out the specific functions of β-catenin in particular contexts can be challenging. Shigetomo Fukuhara, Naoki Mochizuki and colleagues now report a transgenic zebrafish line that allows the visualisation of β-catenin activity in living tissues (p. ). They use this line to investigate the role of β-catenin in vascular development, finding that it plays a key role in formation of the caudal vein (CV). Surprisingly, β-catenin activity in this context appears to be independent of Wnt signalling, and instead is regulated by the BMP pathway. They further identify Aggf1 as a putative BMP target that cooperates with β-catenin to activate downstream gene expression in the CV. Finally, the authors show that expression of the orphan nuclear receptor Nr2f2, which is known to be involved in vein specification, is dependent on β-catenin and Aggf1, thus providing insights into the mechanisms by which BMP-dependent β-catenin activity regulates CV development.
