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Hundreds of Loci Linked to Hair Color in GWAS Meta-Analysis

NEW YORK (GenomeWeb) – Researchers have uncovered more than a hundred loci associated with hair color in people through a new genome-wide association meta-analysis.

Twin studies have suggested heritable factors could explain 97 percent of the variation in hair color seen in people, but previous work had only uncovered about a dozen loci associated with hair color. In a new meta-analysis, a King's College London-led team pulled together genotyping and hair color data from a cohort of nearly 300,000 people. As they reported today in Nature Genetics, they identified 124 loci associated with hair color that, together, explain about 21 percent of the variation in hair color.

"Our work helps us to understand what causes human diversity in appearance by showing how genes involved in pigmentation subtly adapted to external environments and even social interactions during our evolution," said joint senior author Timothy Spector from King's College in a statement. "We found that women have significantly fairer hair than men, which reflects how important cultural practices and sexual preferences are in shaping our genes and biology."

Spector and his colleagues conducted a meta-analysis of two genome-wide association studies, one that included 157,653 research participants from 23andMe and one that included 133,238 individuals from the UK Biobank, all of European ancestry. Each participant self-reported his or her natural hair color as an adult as either black, dark brown, light brown, blond, or red.

Women, the researchers noted, were more likely to report having blond or red hair, and were much less likely to report having black hair, as compared to men.

Overall, they uncovered 123 autosomal SNPs and one X-chromosomal locus that were associated with hair color. All but 13 of these loci were novel, the researchers said.

Known pigmentation loci, like HERC2, IRF4, and MC1R, were strongly associated with hair color in the analysis, the researchers reported. Other loci associated with genes in which variants lead to pigmentation impairments — like Waardenburg syndrome, trichomegaly, or Ablepharon macrostomia — also had strong associations.

Some of the strongest associations with hair color were among members of the solute carrier 45 A family as well as among the forkhead box family, the researchers reported.

They also found that, despite the association of hair color with sex, there was no difference in effect sizes for these loci between men and women in either cohort. The researchers found only one SNP associated with hair color that showed an interaction with sex, and then only in the 23andMe cohort.

Spector and his colleagues validated their findings in a meta-analysis of GWAS summary statistics from a further 10 cohorts from the International Visible Trait Genetics (VisiGen) Consortium. For 114 of the 123 autosomal loci, the direction of association was the same in this analysis as in the discovery one.

The genes with the strongest associations in these analyses were enriched for involvement in pigmentation and melanin biosynthetic and metabolic processes.

The researchers further estimated that these new loci account for about 21 percent of the overall hair color heritability and in particular account for 35 percent of red hair, 25 percent of blond hair, and 26 percent of black hair heritability.

Spector and his colleagues added that their findings could also have medical applications.

"While the genetics of hair color is an interesting problem in itself, we hope that better understanding of the biology of melanin pigmentation will be applicable to studies of diseases that interact with pigmentation, such as skin cancer or vitiligo," author David Hinds from 23andMe said.

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