Researchers have discovered a gene that plays an important role in human skin color. The scientists say a variation in the gene is probably the reason people of European origin have light skin.
People come in a spectrum of skin colors from light to dark, but the genetic causes for this variation remain a biological puzzle. Now, a study on the pigmentation of a common aquarium pet, the zebrafish, has provided some insight for researchers at Penn State College of Medicine in Hershey, Pennsylvania.
As they report in the journal Science, they have discovered that a minor structural variation in a certain gene causes some zebrafish to have an overall golden color and lighter stripes than the average zebrafish.
Genes are segments of DNA in the nucleus of cells that control the production of proteins, the chemicals that determine physical characteristics.
Humans have a gene similar to the one that influences zebrafish pigmentation. When the Penn State scientists inserted the human version into zebrafish embryos with the light skin genetic mutation, the fish hatched having the normal, darker zebrafish color.
The researchers then searched an online database of human genetic variation to determine if people have similar differences in this gene. Penn State geneticist Keith Cheng says they learned that people of European descent carry a slightly different version than Africans and East Asians.
"A very tiny variation in that gene appears to have played a major role in the evolution of lighter skin color in people of European ancestry," he said. "There are many genes that affect pigmentation, and this just happens to be one of the major players and also happens to be perhaps one of the defining characteristics of the European subgroup of humans."
The researchers say the genetic mutation may influence other genes to cause people to have blue eyes and lighter hair.
The new work does not explain why Europeans are fair skinned. But it is consistent with the long-standing belief that after early humans migrated from Africa, light skin evolved to allow absorption of more sunshine at higher latitudes for the production of vitamin D, a compound necessary for bones to form correctly.
"To form vitamin D, you need ultraviolet light, and there is not much sunlight as you go further north," added Dr. Cheng. "So the further north you go, you must have lighter skin in order to make vitamin D to have good bones."
Asians are also lighter skinned than Africans, but Dr. Cheng says Asians do not have the same genetic variation in this pigmentation gene that Europeans do. Instead, they share the same gene with Africans, so his team is seeking the genetic difference that controls Asian skin pigmentation.
In the end, he notes that the major defining characteristic of race is determined by only a minor change in a single human protein.