Neural stem cells (NSCs) in the adult mouse brain are largely quiescent but they can be stimulated to produce neurons that integrate into existing networks. It is known that Wnt/β-catenin signalling can influence various stages of neural differentiation but whether it plays a direct role in adult neurogenesis is unclear. Now, Noelia Urbán and colleagues reveal that Wnt/β-catenin signalling is dispensable for adult NSC homeostasis and activation. By analysing adult mouse hippocampal NSCs, they first show that both quiescent and active NSCs express Wnt/β-catenin signalling components, ligands and targets, suggesting that they are able to respond to Wnt activity. However, the NSC-specific deletion of Wnt/β-catenin signalling in vivo does not impair NSC behaviour or maintenance, nor does it affect the generation and survival of new neurons. Following on from this, the authors report that directly stimulating Wnt/β-catenin signalling in quiescent NSCs in vitro promotes their activation. Furthermore, they show that the stimulation of Wnt/β-catenin signalling in active NSCs reduces their proliferative capacity and promotes neuronal differentiation. Overall, these findings highlight that Wnt/β-catenin signalling is dispensable for NSC homeostasis but that it can exert dose- and state-dependent effects on NSCs that could allow them to respond to external stimuli.
