Abstract
High-altitude Tajiks (HA-Tajiks), Tibetans and Sherpas are three groups of high-altitude native people in China. The differences in the mtDNA genome between the three populations and the role of the mtDNA genome in the high-altitude adaptation of HA-Tajiks were seldom investigated. In this study, 80 HA-Tajiks were enrolled, and their whole mtDNA genomes were sequenced. The haplogroup of each subject was determined by comparison to the revised Cambridge Reference Sequence (rCRS). Ten additional populations from East Asia and Central Asia, including Tibetans and Sherpas, were selected as references. The top haplogroup was U, followed by H, T and J. Principle component analysis and genetic distance analysis indicated that HA-Tajiks showed a close relationship with Wakhi Tajiks, Pamiri Tajiks and Sarikoli Tajiks, indicating that they should be considered one nation scattered around the Pamirs. The difference in the mtDNA genome between HA-Tajiks and Sherpas was significantly greater than that between HA-Tajiks and Tibetans. Among the 13 genes related to the OXPHOS pathway encoded by the mtDNA genome, HA-Tajiks showed more significant differences in ND3 and CYTB compared to Tibetans. Compared to Sherpas, HA-Tajiks showed more significant differences in ND1, ND2, COX1, ATP8, ATP6, ND3, ND4L, ND4, ND5 and CYTB. The associated functional changes and underlying molecular mechanisms should be explored by molecular and biochemical investigations in further studies.
Highlights
When humans spread throughout the Earth, high-altitude environments presented a significant challenge to the people living within them
Previous studies have found that eNOS, PPARA15, HIF, ACE16 and EPAS1 in the nuclear genome and CYTB, ATP6, ND1, ND4 and ND5 in the mitochondrial DNA (mtDNA) genome play a great role in the high-altitude adaptation of Sherpas[17]
The main frequencies of the haplogroups in the 80 HA-Tajiks analyzed in this study are shown in Fig. 1, and the major haplogroups were U, followed by H, T and J, indicating that the HA-Tajik population settled in Taxkorgan, China, may have originated from Europe[18,19]
Summary
When humans spread throughout the Earth, high-altitude environments presented a significant challenge to the people living within them. Hypoxia, strong solar radiation and low temperature exert great pressure on the survival of local people Genetic factors in both the nuclear genome and mitochondrial DNA (mtDNA) genome play great roles in the adaptation to high-altitude environments, which was considered as natural impacts on human evolution and adaptation[1]. Their characteristics at high altitudes are considered as markers of high-altitude adaptation. We examined the mtDNA genomes of Tibetans and Sherpas as well as other reported Tajik p opulations[18] to compare the genetic differences between them and to analyze different patterns of high-altitude adaptation between three high-altitude native populations at the Qinghai-Tibetan Plateau and in the Pamirs from perspectives of mtDNA variations
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