Monday, September 21, 2015

More On mtDNA C

My children and many of my other relatives through marriage have mtDNA C5. So an ASHG 2015 abstract on mtDNA C naturally enough, attracted my attention:

A. Askapuli, et al., "Haplogroup C Phylogeny for Altaian Populations and its Implications for the Peopling of Siberia and the Americas."
Characterization of mitochondrial DNA at a genomic level is very important since it provides opportunities for more accurately estimating the timing and directionality of prehistoric human migrations from a maternal perspective. The Altai Mountains are located at the geographic center of the Eurasian landmass, and have been a hotspot of human activities since ancient times due to its geographic location and rich natural resources. 
Aiming to contribute to a better understanding of the prehistoric human expansions in Siberia and subsequent colonization of the Americas, we sequenced and characterized eighteen whole mtDNA genomes belonging to haplogroup C from Altaian populations. The sequenced Altaian mtDNAs represent all four subgroups of haplogroup C (C1, C4, C5, and C7), and two of them belong to C1a, the Asian sister branch of Native American C1. 
The Altaian whole mitochondrial sequences were analyzed together with 313 previously published haplogroup C sequences from different parts of the world. The analyses of whole mitochondrial genomes reveal that haplogroup C lineages in Siberia are distributed without any specific association with geography or language, and suggest northeastern Siberia as a place of origin for haplogroup C and its subbranches C1, C4, C5, and C7. 
The analyses also indicate that Native American haplogroup C types are distantly related with their Siberian sister branches. 
Given the distribution pattern of haplogroup C in Eurasia, the timing of expansions could be inferred from the age estimates of the lineages within haplogroup C. Age estimation of haplogroup C sequences in our data set via ρ statistics shows that haplogorup C has a TMRCA of 31.25 kyr (24.13-38.56), and its subbranches C1, C4, C5, and C7 have TMRCAs of 21.64 kyr (16.83-26.55), 24.88 kyr (16.65-33.41), 19.76 kyr (13.63-26.08), and 27.2 kyr (16.69-38.17), respectively. 
Still, it is almost impossible to pinpoint geographic origin of Native Americans and directionality of prehistoric migrations in Siberia with certainty. Based on the results of the current study, the Amur region in northeastern Siberia could be the geographic origin for ancestral Native Americans. In order to obtain clearer picture of human population movements in Siberia and the Americas from a maternal perspective, more mitochondrial genomes need to be sequenced, especially mitochondrial genomes belonging to the relatively diverse haplogroups C and D.

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