Researchers have identified two genes that appear to explain why Tibetans are able to live comfortably in rarefied air at very high altitudes.
Dubbed the roof of the world, Tibet is the highest region on earth, with an average elevation of 4,900m.
To find out if Tibetans may have special genetic features that allow them to breathe easy in high places, scientists analyzed the genes of 31 Tibetans who were unrelated to each other, and compared them with the DNA of 90 Chinese and Japanese individuals living in low-lying areas.
In a paper published in the journal Science yesterday, the scientists from China and the US said they hunted for genetic variations in locations that previous studies associated with adaptation to high altitudes.
Two genes — EGLN1 and PPARA on human chromosomes 1 and 22 — turned up consistently, said co-author Xing Jinchuan from the Eccles Institute of Human Genetics at the University of Utah School of Medicine in the US.
“Their exact roles in high-altitude adaptation is unclear. Both EGLN1 and PPARA ... may cause a decrease of the hemoglobin concentration,” Xing wrote in reply to questions from reporters.
Tibetans have unusually low blood hemoglobin levels, which allows them to thrive at high altitudes, but it is only now that experts have managed to trace this feature back to genes.
When people who normally live in lowlands visit Tibet, the lack of oxygen in their bodies may cause altitude sickness, which can develop into fatal heart or brain inflammation.
“Presumably Tibetans have developed a regulation mechanism to control the hemoglobin concentration to prevent these negative effects,” Xing wrote.
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