Zebra Fish DNA Reveals Human Skin Tone Gene
Although more than 100 genes had been linked to pigment production, including genes linked to disorders such as albinism, very little had been known about the underlying basis of normal skin tones. In the new Penn State University-led collaboration, researchers found that two slightly different versions of the same gene could account for 25 to 38 percent of skin pigment differences between people of European and African descent.
The gene was unable to account for variations between West Africans and East Asians, however, demonstrating what scientists stress are the underlying complexities of even seemingly simple genetic traits such as eye and skin color.
“As an Asian, I must say I can’t wait to get this stuff demystified,” said co-author Keith Cheng, an associate professor of pathology at the Penn State College of Medicine in Hershey, Pa. Genetics, he hopes, may one day remove the derogatory connotations sometimes implied by the term “race.”
In zebra fish, scientists had long noticed a color difference in “golden” variants, which lack the darker stripes of their counterparts. Cheng and his colleagues found that within these “golden” fish, an alteration in a gene called slc24a5 results in a significantly cropped protein, leading to fewer, smaller and less colored pigment particles known as melanosomes.
Rapidly expanding genetic databases showed the same gene in dogs, mice, humans and other species with a backbone. The recently released HapMap database, a freely accessible compilation of variations in DNA sequence throughout the human genome, offered the researchers another major clue.
One database-fueled study had already singled out the human version of the slc24a5 gene as the second- best indicator of ancestry from among a list of more than 3,000 genes: 99 to 100 percent of European-American groups studied possessed one variant of the resulting protein, while 93 to 100 percent of African, American Indian and East Asian populations had another.
This holds the promise of a cure for freckles!