Effects of Purifying and Adaptive Selection on Regional Variation in Human mtDNA

Science Magazine | 2004-01-09

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Eduardo Ruiz-Pesini,1 Dan Mishmar,1 Martin Brandon,1,2 Vincent Procaccio,1 Douglas C. Wallace1*

Abstract

A phylogenetic analysis of 1125 global human mitochondrial DNA (mtDNA) sequences permitted positioning of all nucleotide substitutions according to their order of occurrence. The relative frequency and amino acid conservation of internal branch replacement mutations was found to increase from tropical Africa to temperate Europe and arctic northeastern Siberia. Particularly highly conserved amino acid substitutions were found at the roots of multiple mtDNA lineages from higher latitudes. These same lineages correlate with increased propensity for energy deficiency diseases as well as longevity. Thus, specific mtDNA replacement mutations permitted our ancestors to adapt to more northern climates, and these same variants are influencing our health today.

1 Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697-3940, USA.
2 Information & Computer Science, Institute for Genomics & Bioinformatics, University of California, Irvine, CA 92697-3425, USA.

Excerpted from text ...

To further clarify the role of arctic selection, we examined only those haplogroups found primarily in the arctic. Haplogroups A, C, D, and G are highly enriched in northeastern Siberia, comprising 75% of arctic versus 14% of temperate Asian mtDNAs. Haplogroups A, C, and D arrived first in northern Siberia and thus were in a position to colonize the Americas when the Bering land bridge appeared. Haplogroup G arrived in Siberia after the bridge submerged. Haplogroup B joined A, C, and D in the Americas via an independent migration. Because B is absent in northern Siberia and rare in northwestern North America, it appears to have arrived by a more southerly route. Haplogroup X is found in the Great Lakes region of Central Canada, and is more prevalent in Europe than Asia. Hence, X has also persisted in the northern latitudes for prolonged periods (1).

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