Here, we modelled pre-tumor/stromal crosstalk during Ptch+/− MB evolution by manipulating the Norrin/Frizzled4 (Fzd4) pathway, an endogenous signalling axis that regulates vascular development in the cerebellum via neural/endothelial interactions (Wang et al., 2012; Xu et al., 2004; Zhou et al., 2014). The gene discussed is NDP; the disease is neoplasm.