Studies of a skin color gene across global populations reveal shared origins

All instances of a gene mutation that contributes to light skin color in Europeans came from the same chromosome of one person who most likely lived at least 10,000 years ago, according to Penn State College of Medicine researchers.

While the genetics of skin color is largely unclear, past research using zebrafish by the College of Medicine's Keith Cheng identified a key gene that contributes to lighter skin color in Europeans and differs from West Africans. In 2005, Cheng reported that one amino acid difference in the gene SLC24A5 is a key contributor to the skin color difference between Europeans and West Africans.

"The mutation in SLC24A5 changes just one building block in the protein, and contributes about a third of the visually striking differences in skin tone between peoples of African and European ancestry," said Cheng, distinguished professor of pathology. Lighter skin color may have provided an advantage due to for the better creation of vitamin D in the lesser sunlight characteristic of northern latitudes.

In this current part of the project, Victor Canfield, assistant professor of pharmacology, together with Cheng, studied DNA sequence differences across the globe. They studied segments of genetic code that have a mutation and are located closely on the same chromosome and are often inherited together. This specific mutation in SLC24A5, called A111T, is found in virtually everyone of European ancestry.

A111T is also found in populations in the Middle East and Indian subcontinent, but not in high numbers in Africans. Researchers found that all individuals from the Middle East, North Africa, East Africa and South India who carry the A111T mutation share a common "fingerprint"—traces of the ancestral genetic code—in the corresponding chromosomal region, indicating that all existing instances of this mutation originate from the same person.

These findings were reported in the journal G3.

The pattern of proportions of people with this lighter skin color mutation indicates that the A111T mutation occurred somewhere between the Middle East and the Indian subcontinent.

"This means that Middle Easterners and South Indians, which includes most inhabitants of India, Pakistan and Bangladesh, share significant ancestry," Cheng said.

This mutated segment of DNA was itself created from a combination of two other mutated segments commonly found in Eastern Asians—traditionally defined as Chinese, Japanese and Korean.

"The coincidence of this interesting form of evidence of shared ancestry of East Asians with Europeans, within this tiny chromosomal region, is exciting," Cheng said. "The combining of segments occurred after the ancestors of East Asians and Europeans split geographically more than 50,000 years ago; the A111T mutation occurred afterward."

Cheng plans to next look at more genetic samples to better understand what genes play the most important role in East Asian skin color. He will then use zebrafish to test those suspected genes.

The differences in affect skin cancer rates. Europeans have 10 to 20 times more instances of melanoma than Africans. However, despite also having lighter skin, East Asians have the same melanoma rates as Africans. The reason for this difference can only be explained after the gene for both groups are found. This understanding could lead to better treatments for melanoma.

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Osiris1
1 / 5 (1) Jan 03, 2014
But no humans at all did any more than eat, sleep, make babies, fart, and throw rocks and sticks until about 13,000 years ago, although some of the Indian Vedas suggest civilization around the Indian subcontinent up to 35,000 years ago..... Maybe two separate bioengineering attempts, the first and oldest failed or was incomplete, and the second one 'took'. Finding an original Bible in or close to the original alien language would be a real boon to science. Probably at the bottom of the Persian Gulf if it exists, of in some dusty cave on the Iranian shore of it.
Shakescene21
1 / 5 (1) Jan 04, 2014
This abstract is not very straightforward but if I understand it right: The mutation in gene SLC24A5 which helps cause the very light skin of Europeans, is designated A111T. This mutation apparently originated in the region between the Middle East and India where it was modestly successful. This mutation was carried to Europe through migration and/or interbreeding with Europeans, where it was so successful that it became nearly universal in Europe.
This is plausible but seems overly complicated. Given the weak sunshine in Northern Europe, where the A111T mutation would be most successful, it would be expected that the mutation would occur there first.
Also, does this mean that 15,000 years ago the population of Europe was darker than today?
Scroofinator
not rated yet Jan 08, 2014
I wonder if Inuits share the same mutation. One would assume that they would be light skinned too, but they display the same skin tones as the rest of the Native Americans.