MAPK3 and neoplasm: SASH1, a member of the SLy family of signal adapter proteins, acts as a candidate tumour suppressor and plays a regulatory role in the tumorigenesis of breast and colon cancers.17,18 In pigmentation disorders such as DUH, SASH1 promotes melanocyte transepithelial migration through a Gαs–SASH1–IQGAP1–E-cadherin-dependent pathway14 or via a p53-POMC-MC1R signalling cascade, thereby enhancing the phosphorylation of ERK1/2 and CREB and resulting in a hyperpigmented phenotype.19