In addition to N-myc, a common proto-oncogene [113], another transcription factor that participates in the canonical Shh signaling-driven promotion of neuronal precursor expansion is Atoh1 [114]; Shh prevents Atoh1 degradation by the E3 ubiquitin ligase Huwe1, which results in medulloblastoma when knocked out in mice [115]. Here, SHH is linked to medulloblastoma.