Whole mitochondrial genome analysis of highland Tibetan ethnicity using massively parallel sequencing

Mitochondrial DNA (mtDNA) is a key player in numerous multifaceted and intricate biological processes and plays a pivotal role in dissecting the peopling of different populations, due to its maternally inherited property and comparatively high mutation rate. In this study, 119 Tibetan individuals from the Muli Tibetan Autonomous County of China (average altitude above 3,000 m) were employed in mitochondrial genome (mitogenome) sequencing by massively parallel sequencing (MPS) techniques using the Precision ID mtDNA Whole Genome Panel on an Ion S5XL system. The dataset presented 88 distinct haplotypes, resulting in the haplotype diversity of 0.9909. The majority of haplotypes were assigned to East Asian lineages and the distribution of haplogroups of Muli Tibetan significantly differed from reference Tibetan populations. The maximum parsimony phylogeny reconstructed by 119 newly generated mitogenomes revealed 12 major Muli Tibetan lineages. Intriguingly, a Sherpa-specific sub-haplogroup A15c1 with the lack of mutations at 4216 and 15,924 was discerned in our dataset, which suggested that the maternal gene pool of Sherpas may derive from Tibetan populations. The shared haplogroups between Muli Tibetan and lowland Han Chinese hinted that these lineages may derive from non-Tibetans and have already differentiated before their arrival on the Tibetan Plateau. Furthermore, extensive pairwise population comparisons displayed that Muli Tibetan had a closer genetic relationship with ethnically or linguistically close Nyingtri Tibetan, Nyingtri Lhoba and Chamdo Tibetan populations. Genetic affinity was also observed between the Muli Tibetan and North Han Chinese. Collectively, the results generated in this study enriched the existing forensic mtDNA database and raised additional interest in the application of whole mitogenome sequencing in forensic investigations.