Research has identified a genetic variant involved in causing grey hair during the ageing process.
Researchers analysed data from over 6000 men and women from Brazil, Colombia, Chile, Mexico and Peru. They recorded hair traits, including texture, colour, balding and greying, for each volunteer, and took a sample of DNA.
They then compared hundreds of thousands of variations in the genetic code of each individual to identify which genes had the strongest links with hair features – an approach known as a genome-wide association study.
This led the team to identify 18 genetic variants, ten of which had never been linked to hair traits before.
One of these SNPs was found in a gene called IRF4. Recent research has shown this gene plays a role in regulating production and storage of melanin – the pigment that determines skin, eye and hair colour. Grey hair is caused by the loss of this pigment.
'We already know several genes involved in balding and hair colour, but this is the first time a gene for greying has been identified in humans,' said Dr Kaustubh Adhikari of University College London, lead author of the study published in Nature Communications.
The researchers therefore say that understanding how IRF4 affects melanin content could further our knowledge of the ageing process and could also have cosmetic applications to prevent greying hair.
The study also identified a number of other genes that influence different aspects of hair appearance – including FOXL2, associated with eyebrow thickness, and PRSS53, which was linked to hair curliness.
While previous research into hair loss, colour and texture had largely focused on narrower European and East Asian populations, this study included a diverse mix of European, African and Native American descendants, providing a wide variation of hair traits.
The researchers say the results may contribute to our understanding of human evolution, as some hair traits may have conferred survival advantages in certain environments.
'It has long been speculated that hair features could have been influenced by some form of selection, such as natural or sexual selection, and we found statistical evidence in the genome supporting that view,' said Dr Adhikari.
'The genes we have identified are unlikely to work in isolation to cause greying or straight hair, or thick eyebrows, but have a role to play along with many other factors yet to be identified.'
The findings could also help to form the basis of future forensic investigations, with the prospect of creating visual mugshots of suspects based on DNA evidence. However, much more research will be needed first to identify more of the genes involved.
'With the exception of hair colour, we don't yet understand nearly enough of the genetic basis of these traits for them to be useful,' Dr Manfred Kayser of the Erasmus University Medical Center in Rotterdam, who was not involved in the study, told Scientific American.
However, he added: 'For many of the hair traits studied in this paper, they deliver the first genetic knowledge.'