Shades of Flesh Tone: Tests reveal gene for people’s skin color

It’s no secret that skin comes in a vast array of shades. However, the genetics that control this phenomenon have remained a mystery. Researchers have now tracked down a gene that they propose plays a major role in determining each person’s skin color.

DIFFERENT STRIPES. A normal zebra fish (top) has larger and denser pigment-containing cells than a golden zebra fish (bottom) has. Science

Keith C. Cheng of the Penn State College of Medicine in Hershey, Pa., and his colleagues originally found this novel gene in zebra fish, an animal popular among scientists studying genetics.

The researchers worked with unusual golden fish that have honey-colored stripes instead of the species’ typical black stripes. Their research had shown that the golden variety has smaller pigment-containing cells than normal zebra fish do and that the golden fish’s cells contain fewer and lighter pigment particles.

Cheng’s team wondered whether the same genetic mechanism regulates skin color in both fish and people. To investigate, his team used a variety of genetic techniques to find the genes responsible for the golden zebra fish’s atypical color. Eventually, the investigators identified a mutation in a gene called slc24a5.

Next, the scientists looked into data generated by the Human Genome Project to see whether a similar gene exists in people. Sure enough, Cheng’s group located a comparable gene, which they called SLC24A5, on human chromosome 15.

To see whether variations in the human gene play a role in determining skin color, Cheng’s team located the gene on the International Haplotype Map, a database of sites in the genome where DNA tends to differ among people (SN: 10/29/05, p. 277: SNPs Ahoy! Scientists complete map of genetic differences). The researchers found that SLC24A5 usually takes a slightly different form in people of African heritage than it does in people of European heritage.

Cheng’s team also examined the genomes and skin color of 308 people with mixed African and European ancestries. Individuals with less of the pigment melanin in their skin, and thus lighter skin, tended to have the European form of the gene, the researchers report in the Dec. 16 Science.

Although the results suggest that the gene’s form is an important factor in skin color, Cheng cautions that it’s not the sole player. He points out that Asian populations represented in the haplotype database typically carry the African form of the gene but usually have light skin, suggesting influences from genes other than SLC24A5.

“It’s likely that there are many ways to add up to a particular skin color,” Cheng says.

Francis Collins, director of the National Human Genome Research Institute in Bethesda, Md., warns that the discovered gene is only indirectly connected with race, a complex sociological concept based on factors such as ancestral geography and culture. Adds Collins, “To say that this is the gene for race is a fundamental misconception of … that complex term.”