New hair colour genes identified

The research analysed the genomes of 300,000 people of European descent who self-reported their natural hair colour in adulthood. By comparing their genomes, they pinpointed 124 genes significantly associated with hair colour; one of which was on the X chromosome. 

Only 13 of these had been previously identified. 

Variations in single nucleotides, the building blocks of DNA, were found to be responsible for about 35% of red hair, 25% of blond hair, and 26% of black hair heritability in the group of people studied. The study findings also provide insights into disease and sex-specific pigmentation.

“These extra 100 or so genes allow us to understand the role of pigment in many diseases, such as cancer and autoimmune diseases,” says genetic epidemiologist, Timothy Spector, of King’s College London, who co-led the study. 

The genes identified in the study include some involved in melanin metabolism––melanin is a pigment that determines skin and hair colour. The study rooted out others in which mutations are known to cause pigmentation impairments, such as in Waardenburg syndrome, a condition that can cause hearing loss and colour irregularities in hair, eyes and skin.

The international team of researchers, including Dragana Vuckovic of Sidra Medical and Research Centre in Qatar, also found that the women in the group self-reported lighter hair colours than men. 

This is in line with previous similar findings that are based on objective measurement of hair colour, suggesting, the researchers write, that sex is associated with hair colour, independent of socially-driven, personal biases. 

Molecular epidemiologist, Jonas Mengel-From of the University of Southern Denmark, who was not involved in the research, says that self-reporting of hair colour can be subject to a degree of misclassification. Some people, for example, might report their light brown hair as blond. Animal studies have found evidence that pigmentation genetics is sex specific. For example, tortoiseshell-coloured cats are always female, while ginger cats are often male. 

However, it’s possible that the sex difference in hair colour, in the present study, reflects an environmental contribution, he suggests, such as bleaching by the sun, since women tend to grow their hair longer than men.

The team was able to use their results to predict black and red hair colours with a high degree of accuracy using a separate set of genetic data in which hair colour was known. Although predictions for brown and blond hair colour were less accurate, this can potentially help in predicting hair colour based on DNA evidence in forensic investigations.

“The study adds an impressive 100-plus new hits, demonstrating a genetic complexity far beyond what we know today,” says Mengel-From. 

He adds that the genes identified in the study include some already known for their involvement in pigmentation biology, and others involved in more fundamental cellular biology, drawing new, interesting links between genes and hair colour biology. 

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