SHH and microphthalmia: This may in part explain the chemotaxis displayed by some cranial NCC in the presence of Shh (Tolosa et al. 2016) as well as the very heterogeneous phenotypes in the presence of mosaic, constitutively activating mutations in SMO. Depending on the lineages targeted, these can cause Curry–Jones syndrome, which includes iris colobomas and microphthalmia (Twigg et al. 2016), while within the epidermis in postnatal somatic mutation, the same hotspot mutations are found in basal cell carcinomas (Xie et al. 1998).