Specific blockage of the p300/β-catenin interaction in wild-type mouse embryos significantly depletes the neural stem cell pool. Treatment with small-molecule p300/β-catenin antagonists, YH249, decreased proliferating cells in embryos (E17.5), as assessed by PCNA immunostaining, and this effect was reversed by ICG-001 treatment (Rescue YH) (A). No difference in the proliferative capacity of precursors was observed, as assessed by pHH3 immunostaining (B). One-way ANOVA followed by a Newman–Keuls multiple comparison test showing a significant difference (*** p < 0.001) of YH249 treatment from the other three treatments. vz, ventricular zone. n ≥ 6.