Human mtDNA site-specific variability values can act as haplogroup markers

Sequencing of entire human mtDNA genomes has become rapid and efficient, leading to the production of a great number of complete mtDNA sequences from a wide range of human populations. We introduce here a new statistical approach for classifying mtDNA nucleotide sites, simply by comparing the mean simple deviation (MSD) of their specific variability values estimated on continent-specific dataset sequences, without the need for any reference sequence. Excellent correspondence was observed between sites with the highest MSD values and those marking known mtDNA haplogroups. This in turn supports the classification of 81 sites (23 in Africa, eight in Asia, eight in Europe, 34 in Oceania, and eight in America) as novel markers of 47 mtDNA haplogroups not yet identified by phylogeographic studies. Not only does this approach allow refinement of mtDNA phylogeny, an essential requirement also for mitochondrial disease studies, but may greatly facilitate the discrimination of candidate disease-causing mutations from haplogroup-specific polymorphisms in mtDNA sequences of patients affected by mitochondrial disorders.