Genome wide study of hair color

[Angela]

This is based on UK biobank data.

See:
https://www.nature.com/articles/s414...bvuWZqyA%3D%3D

"Natural hair colour within European populations is a complex genetic trait. Previous work hasestablished that MC1R variants are the principal genetic cause of red hair colour, but withvariable penetrance. Here, we have extensively mapped the genes responsible for hair colourin the white, British ancestry, participants in UK Biobank. MC1R only explains 73% of the SNPheritability for red hair in UK Biobank, and in fact most individuals with two MC1R variantshave blonde or light brown hair. We identify other genes contributing to red hair, thecombined effect of which accounts for ~90% of the SNP heritability. Blonde hair is associatedwith over 200 genetic variants and we find a continuum from black through dark and lightbrown to blonde and account for 73% of the SNP heritability of blonde hair. Many of theassociated genes are involved in hair growth or texture, emphasising the cellular connectionsbetween keratinocytes and melanocytes in the determination of hair colour."

Well, so much for deciding some ancient sample had red hair because we find one MCIR variant.

This will all be of great help in forensics once they update the calculators.

[ThirdTerm]

Having two MC1R alleles is not a necessary condition for causing red hair, even though 92% of red-haired individuals are known to carry two MC1R alleles. 15% of people with two MC1R variants have blonde hair, while a variant in HERC2 is associated with a decreased probability of red hair. Probably one's hair color is determined by the interaction between these various pigmentation genes. For instance, Prince Harry's famous ginger hair is almost blonde. He is likely to have both MC1R and HERC2, which is associated with blue eyes and blonde hair, and the effect of MC1R is suppressed by HERC2.

Genes associated with red hair colour, in particular MC1R, are also identified in our blonde hair analysis. Although 93% of individuals with red hair carry two MC1R variants, these make up only 15% of people who carry two MC1R variants. The majority of people with two variants have blonde (15%) or light brown hair (41%). The proportion of individuals with blonde hair decreases with one or no variants whilst the proportion with dark brown and black increases (Supplementary Table 5). We show the incidence of different hair colours on each combination of MC1R variants in Supplementary Figures 3−6.

We find a variant in HERC2 associated with a decreased probability of red hair. It is well established that variants in HERC2 alter transcription of the neighbouring pigmentation gene OCA2 which is additionally associated with blue eyes and blonde hair colour12,21,22,23,24. Recessive mutations in OCA2 result in albinism. It is possible that varied expression of OCA2 modifies the effect of reduced signalling though variant MC1R, such that red hair colour is not expressed.