A cis -acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse

Gray horses are born colored but gradually lose hair pigmentation and become white, a trait that is transmitted in an autosomal dominant manner. Leif Andersson and colleagues report that the the mutation causing the Gray phenotype is a 4.6-kb duplication in intron 6 of STX17 , which promotes overexpression of both STX17 and the neighboring gene NR4A3 in melanomas from Gray horses.