EPAS1 and polycythemia: Two Tibetan specific loci with the highest prevalence and strongest fixation index (FST)[5] are EGLN1 encoding prolyl hydroxylase 2 (PHD2) - a principal negative regulator of the HIFs levels, and a large genomic region including EPAS1 which encodes HIF-2α - an isoform of one of the three α-subunits of HIFs (encoded by EPAS1 gene); both these genomic loci were reported to protect from polycythemia [3, 6–8].