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.

Quantifying variation in human scalp hair fiber shape and pigmentation

“…). Though hair color is often described categorically, there have been many attempts to quantify this continuous trait, including recently the increasing use of reflectance spectrometers and tristimulus colorimetry methods (e.g., Norton et al, ). The advantages of such methods over the chemical method used in this study is lower relative cost and time.…”

“…However, neutral genetic processes may also have had an important part to play in the evolution of human hair variation. For example, the high frequency of blond hair among Melanesians has been attributed to founder effect in the TYRP1 mutation (Kenny et al, ; Norton et al, ), thus illustrating the importance of exploring mechanisms other than selection when considering the evolution of human hair diversity.…”

Adaptation of human skin color in various populations

“…A notable example is a non-synonymous variant, rs387907171, in TYRP1 [85]. It is restricted to the Solomons and parts of the Bismarck Archipelago, and might contribute to the ‘blond hair’ in this region [85, 86]. These results emphasize the complex genetic architecture of pigmentation phenotypes, and also highlight the role that population history (e.g., the complex population history of the Southwest Pacific [87–89]) can play a role in influencing phenotypic diversity.…”

The rs387907171 SNP in TYRP1 is not associated with blond hair color on the Island of Bougainville

“…A subsequent study examined the distribution of this derived allele in populations from Northern Island Melanesia. The allele occurs at a lower frequency in this region (0.10 vs. 0.26), and although still significantly associated with lighter hair color, this association is far weaker than that observed in the Solomon Islands (Norton et al, ).…”

“…Taken together, allele frequency data from both studies indicate that the derived allele at rs387907171 has a sharply limited geographic distribution, occurring at its highest frequencies in the southeastern Solomon Islands and in the islands of the New Ireland and New Hanover in the Bismarck Archipelago. Two models for the origin and dispersal of the derived allele were proposed based on this distribution (Norton et al, ), one involving a relatively late, Lapita‐mediated dispersal from the Bismarcks into the Solomons and another proposing early, Pleistocene origin.…”