Distribution of an allele associated with blond hair color across Northern Island Melanesia.

Abstract

Pigmentation of the skin, hair, and eyes is a complex trait controlled by multiple genetic loci. Recently a non-synonymous mutation in the pigmentation candidate gene TYRP1 was shown to be significantly associated with a blond-hair phenotype in populations from the Solomon Islands. The distribution of this mutation in the islands of Northern Island Melanesia, where the blondism phenotype is also prevalent, was unknown. Here, we present data describing the distribution of this allele in 550 individuals sampled from across this region, and test for associations between genotype at this locus and quantitatively measured skin and hair pigmentation phenotype. We report that the frequency of the 93C allele is notably lower than observed in the Solomons (0.12 vs. 0.26). The allele exhibits significant geographic heterogeneity across the islands sampled (χ(2)  = 108.4, P < 0.0001). It is observed at its highest frequencies on the islands of New Ireland and New Hanover, while being almost completely absent from the large island of New Britain. Using linear regression with age, sex, and island as covariates we report that, as in the Solomons, the 93C allele is significantly associated with a decrease in hair pigmentation but not skin pigmentation. We discuss the distribution of the 93C allele across the Southwest Pacific in light of its possible place of origin and dispersal.