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Natural selection shaped regional mtDNA variation in humans
Dan Mishmar1, Eduardo Ruiz-Pesini, Pawel Golik
1Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, 92697-3940, USA.
Summary
Natural selection, not just genetic drift, may explain human mitochondrial DNA (mtDNA) regional variations. Climate influenced the evolution of specific mtDNA genes as populations migrated to colder regions.
Area of Science:
- Human evolutionary genetics
- Mitochondrial genomics
Background:
- Human mitochondrial DNA (mtDNA) exhibits significant regional diversity.
- Traditional explanations focus on genetic drift, but this doesn't fully account for observed lineage distributions and enrichments in Eurasia.
Purpose of the Study:
- To investigate the role of natural selection, particularly climate-driven adaptation, in shaping human mtDNA variation.
- To test the hypothesis that colder climates favored specific mtDNA lineages.
Main Methods:
- Analysis of 104 complete human mtDNA sequences from diverse global populations.
- Comparison of nonsynonymous (Ka) and synonymous (Ks) mutation rates (Ka/Ks ratios) across 13 mtDNA protein-coding genes.
- Stratification of analyses by climatic zones (tropical, temperate, arctic).
Main Results:
- mtDNA variation in African populations aligned with neutral evolution, while European, Asian, and Siberian/Native American variations deviated.
- The ATP6 gene showed unexpectedly high amino acid variation, especially in arctic populations.
- Cytochrome b and cytochrome oxidase I genes displayed distinct variability patterns in temperate and tropical zones, respectively.
- Identified functionally significant amino acid changes in key mtDNA genes.
Conclusions:
- Natural selection likely played a significant role in shaping regional human mtDNA variation.
- Climate appears to be a key selective pressure influencing mtDNA evolution during human migrations.