September 11, 2010

Natural selection for high altitude living

The frappe results for Andean and Tibetan populations are shown below (Figures S2 and S3):

PLoS Genet 6(9): e1001116. doi:10.1371/journal.pgen.1001116

Identifying Signatures of Natural Selection in Tibetan and Andean Populations Using Dense Genome Scan Data

Abigail Bigham et al.

High-altitude hypoxia (reduced inspired oxygen tension due to decreased barometric pressure) exerts severe physiological stress on the human body. Two high-altitude regions where humans have lived for millennia are the Andean Altiplano and the Tibetan Plateau. Populations living in these regions exhibit unique circulatory, respiratory, and hematological adaptations to life at high altitude. Although these responses have been well characterized physiologically, their underlying genetic basis remains unknown. We performed a genome scan to identify genes showing evidence of adaptation to hypoxia. We looked across each chromosome to identify genomic regions with previously unknown function with respect to altitude phenotypes. In addition, groups of genes functioning in oxygen metabolism and sensing were examined to test the hypothesis that particular pathways have been involved in genetic adaptation to altitude. Applying four population genetic statistics commonly used for detecting signatures of natural selection, we identified selection-nominated candidate genes and gene regions in these two populations (Andeans and Tibetans) separately. The Tibetan and Andean patterns of genetic adaptation are largely distinct from one another, with both populations showing evidence of positive natural selection in different genes or gene regions. Interestingly, one gene previously known to be important in cellular oxygen sensing, EGLN1 (also known as PHD2), shows evidence of positive selection in both Tibetans and Andeans. However, the pattern of variation for this gene differs between the two populations. Our results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection. These data suggest a genetic role in high-altitude adaption and provide a basis for future genotype/phenotype association studies necessary to confirm the role of selection-nominated candidate genes and gene regions in adaptation to altitude.



Katharós said...

@ Dienekes
I sent you a paper a few days a ago about a Neolithic graveyard in the United Arab Emirates “Jebel al-Buhais.”. Just in case your mail program regarded it as Spam.

Onur Dincer said...
This comment has been removed by the author.
Onur Dincer said...

It is noteworthy that Berbers are completely inseparable from the European populations and have no Negroid admixture according to the results. I wonder from which region and Berber ethnic group of North Africa they are (I guess none of them are Tuareg).

Unknown said...

I am fascinated by the diversity that is apparent in the Native American tribes. I am still reading through the paper, but if the colour coding is comparable there appear to be different affiliations between NA tribes and Asian ethnic groups.

From Figure 2 it looks like:

(1) Karitiana of Brazil = Yakut (North Asia, hunter gatherer superhighway?)

(2) Quechua/Aymar of Peru = The South East Asian coastal migration.

(3) Pima = Tibet (original NE Asians)

Probably also in that temperal order.

Unknown said...

I am guessing that the Maya and Arawaks may be from an earlier NE Asia migration wave than the Pima.

Unknown said...

The Surui of Brazil appear to be the most divrgent, possibly from an even earlier migration wave.

From S2 and S3

The Maya and Arawaks (COL) appear to be cousins. Distinct but possibly from the same parent ethnic group, probably the original NE Asians.

princenuadha said...

I don't know about standardized tests for high altitude populations but there is a correlation between the top completing nations in long distance running and high altitude living. It would make sense that having genetic adaptations to high altitude confers an advantage to some individuals for long distance running. In both cases the body needs to be efficient at delivering oxygen, which is why there is night altitude training.

The populations that compete very well are near the Atlas mountains and in Kenya and Ethiopia (all high altitude). But I have never noticed Mexicans, Peruvians, or Tibetans to be especially good. Even after considering economics and culture high altitude populations living outside Africa don't compare to high altitude populations living in Africa.

I think the reason for this is because those African populations have been living at high altitude for a linger period and have adapted genetically to a greater extent.

Its easy to see that Kenyans and Ethiopians have been living in high altitude longer (OOA and greater diversification from neighbors). But the Moroccans are harder to explain. Most their heritage came from the middle east. But I suppose They have still been living there linger than the Tibetans and Peruvians. Peruvians are Americans so... and probably had a bunch of Lowlanders come in after the ice age.

princenuadha said...

Correction, last line is supposed to read:

Tibet probably had a bunch of Lowlanders coming in after the latest ice age (comparatively more than Morocco).

I would like to see another study confirm my hypothesis; that Moroccans, Ethiopians, and Kenyans are more adapted to high altitude than Tibetans and Peruvians.

However testing high altitude adaptations will depend on what you define as such. Could be kinda murky.

Onur Dincer said...

I would like to see another study confirm my hypothesis; that Moroccans, Ethiopians, and Kenyans are more adapted to high altitude than Tibetans and Peruvians.

None of them lives at high altitude compared to Tibetans and Andeans.

princenuadha said...

I still stand by what I said. I suspect that Kenyans, Ethiopians, and Moroccans would be more adapted specifically to high altitude in the genetic sense. I think it has to do with the difference in time each peoples have been at high altitude.