MtDNA haplogroups in human populations and disease studies

Molecular analyses have shown that most of human mitochondrial DNA (mtDNA) sequence variation has accumulated sequentially along radiating maternal lineages from sets of mtDNA founders during and after the process of human colonization of different geographical regions of the world. This is the reason why mtDNA haplogroups (groups of related mtDNAs sharing ancient mutations by descent) are often found to be geographically or ethnically specific. Analysis of mtDNA haplogroups is, however, not only limited to human origin and evolution. It is also important for studies of human pathologies. Indeed, recent studies have shown that mtDNA haplogroups can play an important role in modulating disease expression. For instance, it has been observed that the ancient set of mutations which characterize all mtDNAs belonging to the common European-specific haplogroup J substantially enhances the penetrance of the mutations 11778A and 14484C and the risk of expression of Leber Hereditary Optic Neuropathy.