BEIJING, Dec. 19 (Xinhuanet) -- U.S. researchers have discovered what could be the most important skin color gene identified to date.
(Photo source: physorg.com)
With help from a common aquarium pet and a recently released online database of human genetic variation, scientists at Pennsylvania State University found that a change in just one amino acid in one gene plays a major role in determining why people of European descent have lighter skin than people of African descent.
The gene comes in two versions, one of which is found in 99 percent of Europeans and the other in 93 to 100 percent of Africans, according to the new findings, which appear as the cover story in the December 16 edition of Science magazine.
The new gene was first identified not in humans but in a mutant zebra fish, a small striped fish common in aquariums. The zebra fish reproduces rapidly, and many of its genes are similar to humans. The similarities between fish and humans extend to the pigment cells, which contain pigment granules called melanosomes.
The mutant fish are known as golden, because their stripes, usually black, are much paler and their bodies more yellow. The golden version of the fish gene altered production of melanosomes, the tiny black particles of pigments that give skin its color.
The researchers found that the lighter pigmentation of golden zebra fish is caused by a mutation that cuts short a certain protein ¨C referred to as SLC24A5. Adding the normal zebra fish protein to the golden version resulted in fish with darker coloring, researchers found.
The team then studied the recently released HapMap ¨C a free and publicly accessible database of DNA sequence variation in the human genome. When researchers looked at variations within the human SLC24A5 gene, they found that the protein specified by the gene was identical in all populations studied, except for the amino acid at one position. At that position, West Africans and East Asians shared the same ancestral sequence with other vertebrates, including zebra fish and chimpanzees. In contrast, all individuals in the European population tested showed a change in one amino acid.
Further study showed that individuals with the European form of SLC24A5 tended to have lighter skin than those with the ancestral form of the gene.
Asians presumably acquired their light skin through the action of some other gene that affects skin color as they have the same version of the gene as Africans, researchers say. Enditem
(Agencies)
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