Comparative Analysis of Mitochondrial Genome Mutation Spectra in Human Populations

Nucleotide sequence variability of whole mitochondrial genomes (mtDNA) was analyzed and mutation spectra were reconstructed (by L-chain of mtDNA) in four regional groups of indigenous populations representing Northeastern and Southern Siberia, Western Asia, and the Americas. The pyrimidine transitions were found to be predominant in all groups, and of these, the substitutions T→C were most frequent. The second most common in all regional groups (except Northeastern Siberia) are substitutions A→G. Of the transversions, in all the populations studied the substitutions C→A prevail. Between-regional differences in the distribution of nucleotide substitutions in mtDNA mutation spectra were not detected. However, a significant (4-fold) decrease in the number of mutations in mitochondrial gene pools was detected in the indigenous population of Northeastern Siberia compared to other regions. This may be due to the increased effect of negative selection on mtDNA in the Far North environment, which prevents the accumulation of new mutations, and gene drift, which is most pronounced in isolated and small populations of Northeastern Siberia. Because of the lack of between-regional differences in mtDNA mutation spectra, the results obtained do not allow us to confirm the hypothesis that the T→C substitution frequency appears to be a molecular marker of the level of oxidative stress in mitochondria (at least for generative mutations).