Regarding Tibetan genes EPAS1 and HIF-2a.

[davidmich]

Hi,

Which genes (EPAS1 and HIF-2a.) are of greater consequence for the success of the Tibetans in surviving such high altitudes.

EPAS1 (The gene codes for a protein involved in sensing oxygen levels and perhaps balancing aerobic and anaerobic metabolism.) or hypoxia-inducible factor 2-alpha/also called HIF-2a (gives Tibetans fewer red blood cells and hence less hemoglobin in their blood). Perhaps someone has a better description of HIF-2a gene.

I look forward to your feedback.
davidmich

[davidmich]

I just discovered they are the same thing.

EPAS1

Endothelial PAS domain-containing protein 1 (also known as Hypoxia-inducible factor-2alpha (HIF-2alpha)) is a protein that in humans is encoded by the EPAS1 gene.[1][2][3][4]

[njtt]

@davidmich

(gives Tibetans fewer red blood cells and hence less hemoglobin in their blood)
davidmich

Are you sure you haven’t got that backwards? Surely people living at high altitudes will be better off with more hemoglobin in their blood.

[davidmich]

http://blogs.discovermagazine.com/gnxp/2010/07/very-recent-altitude-adaptation-in-tibet/#.UEjBVLSD46U
“The gene in question is known as hypoxia-inducible factor 2-alpha, or HIF-2a, and the Tibetans with the favored version have fewer red blood cells and hence less hemoglobin in their blood.”

“The widespread mutation in Tibetans is near a gene called EPAS1, a so-called “super athlete gene” identified several years ago and named because some variants of the gene are associated with improved athletic performance, Nielsen said. The gene codes for a protein involved in sensing oxygen levels and perhaps balancing aerobic and anaerobic metabolism.”

[Smeghead]

A couple of comments:

The most striking instance was a version of a gene possessed by 9 percent of Han but 87 percent of Tibetans.

Such an enormous difference indicates that the version typical among Tibetans is being strongly favored by natural selection.

No. That difference, by itself, does not necessarily need to be a result of natural selection. It could be due to a founder effect, for instance. The article is unclear on exactly what evidence is in this paper, but they do mention selective sweeps. If they have evidence of a selective sweep, that would be a much stronger argument.

Also, this is their (somewhat hand-wavey) explanation for the lower hemoglobin:

For some reason, individuals with two copies of the mutation function well in high altitude with relatively low hemoglobin concentration in their blood. The mutation seems to provide an alternative inborn mechanism for dealing with the low oxygen levels, Nielsen said.