To address whether intrinsic changes in the developing medulloblastoma cell-of-origin could contribute to the age-dependent mutations in SHH pathway components found in SHH medulloblastoma, a transgenic mouse model was employed that allows lineage tracing and prospective isolation of the developing murine CGNP cell lineage from their specification in the cerebellar primordium onwards (Fig. 1A) (Feil et al., 1997; Machold et al., 2011; Machold and Fishell, 2005). Here, SHH is linked to medulloblastoma.