A trinucleotide deletion together with a base duplication event at codon 439 in the human tyrosinase gene identifies a mutational hotspot.

Abstract Molecular analysis of the human tyrosinage gene in two patients suffering from a temperature-sensitive form of albinism has identified a thymine triplet deletion at codon 439 which is accompanied by a duplication of the immediately preceding cytosine residue. This results in a two base pair frame shift leading to premature termination at codon 448, giving a truncated protein. Its relationship to other mutations in tyrosinase and the possible cause are discussed. The temperature-sensitive phenotype is due to the guanine to adenine mutation at codon 422, known to generate a temperature-sensitive enzyme. The CTTT at F 439 in tyrosinase is also present at F 508 in CFTR, the main mutation causing cystic fibrosis.