Scientists have finally figured out how people of European descent have such varied hair colors.
In a paper published today (paywall), April 16, in the journal Nature Genetics, researchers identified 124 areas of DNA that control for hair color, using a dataset of nearly 300,000 individuals. They believe their work may one day play a role in treatment for various pigment disorders.
The team worked with 23andMe, an at-home genetic testing company, and UK Biobank, a non-profit that conducts long-term epidemiological research on over 500,000 individuals who have donated their genetic information. For simplicity’s sake, the researchers looked only at the DNA from people of European ancestry with black, blonde, dark-brown, light-brown, or red hair.
Previously, scientists had found 13 genes that appeared to play a role in making melanin, the chemical that gives color to our skin, eyes, and hair. With this more robust dataset, researchers were able to identify over 100 genes that seem to play a role in hair pigmentation. Using these genes, they were able to predict in most cases whether people had black or red hair. It was harder to tell which genes corresponded with brown or blonde hair. (Though because one of the genes associated with fair hair appears on the X chromosome, women may be more likely to be blonde than men.)
There still isn’t anything like a true “blonde gene” or “brunette gene.” That’s because in the case of hair color (and many other traits) there are a number of genes responsible that interact in complex ways. Genes work by coding for different proteins, which help carry out all our biologic functions and dictate whether we have certain traits. Most often, in addition to coding for proteins, they’re busy acting like a dial for other genes nearby, telling them how much protein to make. It can be difficult to tell why they are set at either high or low settings, since it could have to do with interactions with other genes, or environmental settings, or some combination. This complexity is the reason that some traits, like hair color, can be so varied even within genetically similar populations.
What does hair color have to do with disease? Any given protein we produce can be used in hundreds of different biological processes. In this case, the researchers think that some of the genes they found to be associated with hair pigmentation may also be connected with certain conditions, like Crohn’s disease and certain types of skin cancer.
Because this work was focused specifically on European dependents, it only covers a fraction of the genetic variety of hair. Future work broadening the genetic lens to include Asian, Middle Eastern, African, and Native American descendants may lead to more discoveries about connections between genes involved in pigmentation and health conditions. That could be years away, however, as there are still major gaps in the genetic data used for scientific research, with far too little DNA samples from people of color compared to those from white people of European descent.