November 14, 2012

High altitude adaptation in Ethiopia

The anthropometric characteristics on pp. 49-50 may also be of interest. It seems Amhara highlanders are shorter, thinner, and  lighter than their co-ethnic lowlanders. Oromo highlanders, on the other hand, appear to be heavier and less thin. (for males).

arXiv:1211.3053 [q-bio.PE]

The genetic architecture of adaptations to high altitude in Ethiopia

Gorka Alkorta-Aranburu, Cynthia M. Beall, David B. Witonsky, Amha Gebremedhin, Jonathan K. Pritchard, Anna Di Rienzo

Although hypoxia is a major stress on physiological processes, several human populations have survived for millennia at high altitudes, suggesting that they have adapted to hypoxic conditions. This hypothesis was recently corroborated by studies of Tibetan highlanders, which showed that polymorphisms in candidate genes show signatures of natural selection as well as well-replicated association signals for variation in hemoglobin levels. We extended genomic analysis to two Ethiopian ethnic groups: Amhara and Oromo. For each ethnic group, we sampled low and high altitude residents, thus allowing genetic and phenotypic comparisons across altitudes and across ethnic groups. Genome-wide SNP genotype data were collected in these samples by using Illumina arrays. We find that variants associated with hemoglobin variation among Tibetans or other variants at the same loci do not influence the trait in Ethiopians. However, in the Amhara, SNP rs10803083 is associated with hemoglobin levels at genome-wide levels of significance. No significant genotype association was observed for oxygen saturation levels in either ethnic group. Approaches based on allele frequency divergence did not detect outliers in candidate hypoxia genes, but the most differentiated variants between high- and lowlanders have a clear role in pathogen defense. Interestingly, a significant excess of allele frequency divergence was consistently detected for genes involved in cell cycle control, DNA damage and repair, thus pointing to new pathways for high altitude adaptations. Finally, a comparison of CpG methylation levels between high- and lowlanders found several significant signals at individual genes in the Oromo.

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1 comment:

Ponto said...

What is your opinion of the "Frappe"? It seems to show Middle Eastern subjects without a specific Middle East component unless it is the components found highest in South Asians and NE Africans, the largest component is similar to that found in Europeans.

The Europeans show various Amerindian type admixture.

Anyway the presentation of the inferred 7 ancestral components differs slightly from other results.