β-Catenin Activation Regulates Tissue Growth Non-Cell Autonomously in the Hair Stem Cell Niche

Wnt/beta-catenin signaling is critical for tissue regeneration. However, it is unclear how beta-catenin controls stem cell behaviors to coordinate organized growth. Using live imaging, we show that activation of beta-catenin specifically within mouse hair follicle stem cells generates new hair growth through oriented cell divisions and cellular displacement. beta-Catenin activation is sufficient to induce hair growth independently of mesenchymal dermal papilla niche signals normally required for hair regeneration. Wild-type cells are co-opted into new hair growths by beta-catenin mutant cells, which non-cell autonomously activate Wnt signaling within the neighboring wild-type cells via Wnt ligands. This study demonstrates a mechanism by which Wnt/beta-catenin signaling controls stem cell-dependent tissue growth non-cell autonomously and advances our understanding of the mechanisms that drive coordinated regeneration.