White crow: 18-nucleotide deletion leading to the absence of six amino acids

Abstract

Two Carrion Crow Corvus corone kept at a bird conservation facility in Niigata, Japan, had entirely white plumage, pink feet and beaks, and red eyes, indicative of a lack of melanin pigments. Tyrosinase, an enzyme essential for melanin biosynthesis, is encoded by the TYR gene. Sequencing analysis of TYR of the white individuals revealed a deletion of 18 consecutive nucleotides, leading to the loss of six amino acids from the tyrosinase protein. The body color mutation is likely to have been caused by this 18-nucleotide deletion. White crows have been found frequently in the Niigata region for over 30 years. The deletion mutant gene is considered to persist in the natural Carrion Crow population of this region, mainly in heterozygous carriers and primarily owing to random genetic drift.