High altitude represents an extreme environment characterised by low concentrations of atmospheric oxygen (hypoxia), arid climate, high solar radiation and other environmental stressors. Andeans have resided at high elevations for several millennia and have developed an unique array of physiological adaptations. However, the genetic changes that led to these adaptations remain largely elusive
The aim of this study is to identify genetic variants that harbour signatures of recent positive selection and may facilitate physiological adaptations to hypobaric hypoxia.
Methods: We conducted whole genome sequencing and lung function tests in 19 Argentinean highlanders (>3500 m) comparing them to 16 Native American lowlanders. We developed a new statistical procedure using a combination of population branch statistics (PBS) and number of segregating sites by length (nSL) to detect beneficial alleles that arose since the settlement of the Andes and are currently present in 15-50% of the population.
We identified two missense variants as significant targets of selection. One of these variants, located within the GPR126 gene, has been previously associated with the forced expiratory volume/forced vital capacity ratio. The derived allele of GPR126 is associated with lung function in our sample of highlanders (p<0.05). The other novel missense variant mapped to the EPAS1 gene encoding the hypoxia inducible factor 2α. EPAS1 is known to be the major selection candidate gene in Tibetans and mutations within this gene lead to erythrocytosis and pulmonary hypertension.
These variants may contribute to the physiological adaptations to hypobaric hypoxia, possibly by altering lung function and preventing excessive erythrocytosis and hypoxia induced pulmonary hypertension in Andean populations.