Researchers have traced blonde hair in northern Europeans to a region of the genome that regulates the KITLG gene, which encodes the KIT ligand and is associated with blonde hair color in northern Europeans.
As Stanford University School of Medicine's David Kingsley and his team report in Nature Genetics, this region contains an enhancer that that drives KITLG expression in developing hair follicles. A SNP in the enhancer dubbed rs12821256 affects the lymphoid enhancer-binding factor 1 (LEF1) transcription factor binding site and that, they found, leads to reduced LEF1 responsiveness and enhancer activity in vitro.
Additionally, mice with the ancestral or derived version of the allele show differences in fur pigmentation.
"Sure enough, when you look at them, that one base pair is enough to lighten the hair color of the animals, even though it is only a 20 percent difference in gene expression," Kingsley says in a statement. "This is a good example of how fine-tuned regulatory differences may be to produce different traits. The genetic mechanism that controls blond hair doesn't alter the biology of any other part of the body. It's a good example of a trait that's skin deep — and only skin deep."