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Belarusian uniparental ancestry

A new study on Belarusian haploid genetics provides some interesting insights for the wider European and West Eurasian picture.
Alena Kushniarevich et al., Uniparental Genetic Heritage of Belarusians: Encounter of Rare Middle Eastern Matrilineages with a Central European Mitochondrial DNA Pool. PLoS ONE 2013. Open accessLINK [doi:10.1371/journal.pone.0066499]

Abstract

Ethnic Belarusians make up more than 80% of the nine and half million people inhabiting the Republic of Belarus. Belarusians together with Ukrainians and Russians represent the East Slavic linguistic group, largest both in numbers and territory, inhabiting East Europe alongside Baltic-, Finno-Permic- and Turkic-speaking people. Till date, only a limited number of low resolution genetic studies have been performed on this population. Therefore, with the phylogeographic analysis of 565 Y-chromosomes and 267 mitochondrial DNAs from six well covered geographic sub-regions of Belarus we strove to complement the existing genetic profile of eastern Europeans. Our results reveal that around 80% of the paternal Belarusian gene pool is composed of R1a, I2a and N1c Y-chromosome haplogroups – a profile which is very similar to the two other eastern European populations – Ukrainians and Russians. The maternal Belarusian gene pool encompasses a full range of West Eurasian haplogroups and agrees well with the genetic structure of central-east European populations. Our data attest that latitudinal gradients characterize the variation of the uniparentally transmitted gene pools of modern Belarusians. In particular, the Y-chromosome reflects movements of people in central-east Europe, starting probably as early as the beginning of the Holocene. Furthermore, the matrilineal legacy of Belarusians retains two rare mitochondrial DNA haplogroups, N1a3 and N3, whose phylogeographies were explored in detail after de novo sequencing of 20 and 13 complete mitogenomes, respectively, from all over Eurasia. Our phylogeographic analyses reveal that two mitochondrial DNA lineages, N3 and N1a3, both of Middle Eastern origin, might mark distinct events of matrilineal gene flow to Europe: during the mid-Holocene period and around the Pleistocene-Holocene transition, respectively.

Mitochondrial DNA
Belarusians have typical Central-Eastern European mtDNA pools, with some 37% H (of which: c. 11% H1 and 15% unclassified H*), c. 12% U5 (roughly half for each major subclade: U5a and U5b) and a diversity of other lineages:

Figure 2. Phylogeny of mtDNA haplogroups and their relative frequencies in Belarusians.
The tree is rooted relative to the RSRS according to [51]. Belarusian sub-populations are designated as BeE – East, BeWP – West Polesie, BeEP – East Polesie, BeN – North, BeC – Centre, BeW – West. Sample sizes and absolute frequencies are also given.

From the paper:

Frequencies of Belarusian mtDNA haplogroups do not differ considerably from other eastern European and Balkan populations, at least when major clades such as H1, H2, V, U5a and U5b, K, T and J are considered (Table S3). However, populations from the easternmost fringe of the eastern European region, the Volga-Uralic, have a decreased share of overall H mtDNAs and a noticeably increased frequency of haplogroup U4 as well as M-lineages compared to Belarusians (Table S3).

Of interest is the rare lineage N3, also found in around the Eastern Mediterranean (from Albania to Egypt) and in Iran, where it probably originated (highest diversity), spreading to Europe possibly in the Neolithic.
Another rare lineage, N1a3, is most frequent among Peninsular Arabs (but with low HVS-I diversity), being also found in the Eastern Mediterranean (from Sicily to Palestine) and the Caucasus. It is very rare in Central and Eastern Europe, excepted Mordvins (but again low diversity). It’s precise origins remain unclear (either West Asia or the European SE, included Italy, where it seems quite diverse). Based on their own age estimates, the authors suggest a rather old diversification of this lineage still in Paleolithic times.
Y chromosome DNA
Belarusian paternal ancestry is dominated by R1a (51%), I2a1 (“I2a”: 17%) and N1c (10%). Other notable lineages are R1b (6%) and I1 (5%). All them are within expectations.

Figure 6. Phylogeny of NRY haplogroups and their relative frequencies in Belarusians.
Haplogroup-defining biallelic markers are in parentheses. Belarusian sub-populations are designated as BeN – North, BeC – Centre, BeE – East, BeW – West, BeWP – West Polesie, BeEP – East Polesie. Sample sizes and absolute frequencies are also given.

I2a1 (“I2a” in the paper) is more common towards the South or SE. Instead N1c shows the opposite distribution, being more common in the North and West. This distribution is concordant with the wider East European picture.
Both lineages show star-like STR structures. Based on them, the authors suggest that, only for Belarusian lineages, N1c (fig. 7)may have spread from the Baltic area (Lithuania, Latvia NW Belarus), while I2a1 (fig. 8) would have spread from the Balcans and maybe Belarus itself. We should not read beyond Belarus here because of the sampling bias of the study (notably regarding N1c, with very few Uralic samples).
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