MtDNA analysis reveals enriched pathogenic mutations in Tibetan highlanders.

Area of Science:

• Genetics and Evolutionary Biology
• Human Adaptation to Extreme Environments
• Mitochondrial Genomics

Background:

• Tibetan highlanders exhibit exceptional adaptation to severe hypoxic conditions.
• Mitochondrial DNA (mtDNA), crucial for cellular respiration, is implicated in hypoxia adaptation.
• Understanding highlander mtDNA variation is key to elucidating their adaptive mechanisms.

Purpose of the Study:

• To comprehensively analyze the mitochondrial DNA (mtDNA) profile of Tibetan highlanders.
• To investigate the genetic history and founding events of highlander populations.
• To explore the association between mtDNA mutations and high-altitude adaptation.

Main Methods:

• Analysis of 549 complete highlander mtDNA sequences, including 432 random samples.
• Phylogenetic analysis of 36,914 mtDNA sequences to identify major haplogroups.
• Founder analysis to reconstruct population colonization history and identify specific lineages.

Main Results:

• Identified 21 major highlander haplogroups coalescing around 10,000 years ago, suggesting distinct founding events.
• Proposed a three-phase colonization model for the Tibetan plateau (pre-LGM, post-LGM Paleolithic, Neolithic).
• Observed a significantly higher frequency of pathogenic mutations in highlander-specific mtDNA lineages compared to controls.

Conclusions:

• Tibetan highlander mtDNA harbors a unique profile with enriched pathogenic and function-altering mutations.
• These genetic variations may have been positively selected, contributing to hypoxia adaptation.
• Mitochondrial genomics offers critical insights into human adaptation to extreme environments.