October 02, 2004

Phylogeny of mtDNA haplogroup N in India

Many new mtDNA studies including the previously posted one on mtDNA haplogroup H are based on complete sequencing of mtDNA, allowing for a very detailed phylogenetic study of the populations examined. This is much easier for mtDNA compared to chromosomal DNA, since the former is much shorter. Studies based on complete sequencing typically have to use small samples, but the resulting phylogenetic knowledge can then be applied to larger population samples, by testing only the informative polymorphic loci discovered.

A new study examines Indian mtDNA in this manner, and especially the macrohaplogroup N, which reaches its highest frequencies in Caucasoid populations, although its specific subclades are found in non-Caucasoids, e.g., Australoids. Most Indian matrilineages belong to a different maclohaprogroup, M, which is shared with the Mongoloids, although Indians harbor clades different from those of Mongoloids, indicating that they are both descended from ancient "Proto-Asian" populations. Both M and N predate the emergence of the modern racial divisions of mankind.

Macrohaplogroup N is shared between Indians and West Eurasians but as this new paper indicates, in India it contains clades likely to be the result of admixture with West Eurasians, but also more ancient clades lacking in West Eurasia; these latter ones are indigenous to India, representing its earliest colonization.

Am. J. Hum. Genet., 75:000, 2004

Phylogeny of Mitochondrial DNA Macrohaplogroup N in India, Based on Complete Sequencing: Implications for the Peopling of South Asia

Malliya gounder Palanichamy et al.

To resolve the phylogeny of the autochthonous mitochondrial DNA (mtDNA) haplogroups of India and determine the relationship between the Indian and western Eurasian mtDNA pools more precisely, a diverse subset of 75 macrohaplogroup N lineages was chosen for complete sequencing from a collection of >800 control-region sequences sampled across India. We identified five new autochthonous haplogroups (R7, R8, R30, R31, and N5) and fully characterized the autochthonous haplogroups (R5, R6, N1d, U2a, U2b, and U2c) that were previously described only by first hypervariable segment (HVS-I) sequencing and coding-region restriction-fragment–length polymorphism analysis. Our findings demonstrate that the Indian mtDNA pool, even when restricted to macrohaplogroup N, harbors at least as many deepest-branching lineages as the western Eurasian mtDNA pool. Moreover, the distribution of the earliest branches within haplogroups M, N, and R across Eurasia and Oceania provides additional evidence for a three-founder-mtDNA scenario and a single migration route out of Africa.


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