Insights into matrilineal genetic structure, differentiation and ancestry of Armenians based on complete mitogenome data

Heterogeneity of the Southeast Belarusian mitochondrial gene pool

The study of mitochondrial DNA (mtDNA) variability at the level of whole mitogenomes has significant implications for the fields of human evolution and population genetics. In this paper, we present the results of a study of the complete mtDNA variability in Belarusians from the southeastern part of the Republic of Belarus. It was found that Southeast Belarusians are characterized by a high diversity of mitochondrial genomes. The analysis of genetic distances between European populations showed significant differences between the studied Belarusian sample from the bulk of East European populations, including Slavic ethnic groups. The results of the phylogeographic analysis indicated the presence of the West Asian component (12.6%) in the Belarusian mitochondrial gene pool, which can account for the observed genetic differences between Belarusians and other Eastern Slavs (Russians and Ukrainians). The East Asian component of the mitochondrial gene pool of the studied group of Belarusians is represented by haplogroup C5c1a (2.3%). The results of the phylogeographic analysis indicated that this mtDNA subclade is predominantly present in the gene pools of Slavic peoples, including Poles, Belarusians, Ukrainians, and Russians. The evolutionary age of haplogroup C5c1a is ~4000 years and, consequently, the appearance of C5c1-haplotypes in the eastern regions of Europe may be linked to the migrations of the Caspian steppe populations to the west during the Bronze Age.

Demographic history and genetic variation of the Armenian population

We introduce a sizable (n = 34) whole-genome dataset on Armenians, a population inhabiting the region in West Asia known as the Armenian highlands. Equipped with this genetic data, we conducted a whole-genome study of Armenians and deciphered their fine-scale population structure and complex demographic history. We demonstrated that the Armenian populations from western, central, and eastern parts of the highlands are relatively homogeneous. The Sasun, a population in the south that had been argued to have received a major genetic contribution from Assyrians, was instead shown to have derived its slightly divergent genetic profile from a bottleneck that occurred in the recent past. We also investigated the debated question on the genetic origin of Armenians and failed to find any significant support for historical suggestions by Herodotus of their Balkan-related ancestry. We checked the degree of continuity of modern Armenians with ancient inhabitants of the eastern Armenian highlands and detected a genetic input into the region from a source linked to Neolithic Levantine Farmers at some point after the Early Bronze Age. Additionally, we cataloged an abundance of new mutations unique to the population, including a missense mutation predicted to cause familial Mediterranean fever, an autoinflammatory disorder highly prevalent in Armenians. Thus, we highlight the importance of further genetic and medical studies of this population.

Genetic Analysis of Mingrelians Reveals Long-Term Continuity of Populations in Western Georgia (Caucasus)

To elucidate the population history of the Caucasus, we conducted a survey of genetic diversity in Samegrelo (Mingrelia), western Georgia. We collected DNA samples and genealogical information from 485 individuals residing in 30 different locations, the vast majority of whom being Mingrelian speaking. From these DNA samples, we generated mitochondrial DNA (mtDNA) control region sequences for all 485 participants (female and male), Y-short tandem repeat haplotypes for the 372 male participants, and analyzed all samples at nearly 590,000 autosomal single nucleotide polymorphisms (SNPs) plus around 33,000 on the sex chromosomes, with 27,000 SNP removed for missingness, using the GenoChip 2.0+ microarray. The resulting data were compared with those from populations from Anatolia, the Caucasus, the Near East, and Europe. Overall, Mingrelians exhibited considerable mtDNA haplogroup diversity, having high frequencies of common West Eurasian haplogroups (H, HV, I, J, K, N1, R1, R2, T, U, and W. X2) and low frequencies of East Eurasian haplogroups (A, C, D, F, and G). From a Y-chromosome standpoint, Mingrelians possessed a variety of haplogroups, including E1b1b, G2a, I2, J1, J2, L, Q, R1a, and R1b. Analysis of autosomal SNP data further revealed that Mingrelians are genetically homogeneous and cluster with other modern-day South Caucasus populations. When compared with ancient DNA samples from Bronze Age archaeological contexts in the broader region, these data indicate that the Mingrelian gene pool began taking its current form at least by this period, probably in conjunction with the formation of a distinct linguistic community.

Evaluating the role of selection in the evolution of mitochondrial genomes of aboriginal peoples of Siberia

Studies of the nature of mitochondrial DNA (mtDNA) variability in human populations have shown that protein-coding genes are under negative (purifying) selection, since their mutation spectra are characterized by a pronounced predominance of synonymous substitutions over non-synonymous ones (Ka/Ks < 1). Meanwhile, a number of studies have shown that the adaptation of populations to various environmental conditions may be accompanied by a relaxation of negative selection in some mtDNA genes. For example, it was previously found that in Arctic populations, negative selection is relaxed in the mitochondrial ATP6 gene, which encodes one of the subunits of ATP synthase. In this work, we performed a Ka/Ks analysis of mitochondrial genes in large samples of three regional population groups in Eurasia: Siberia (N = 803), Western Asia/Transcaucasia (N = 753), and Eastern Europe (N = 707). The main goal of this work is to search for traces of adaptive evolution in the mtDNA genes of aboriginal peoples of Siberia represented by populations of the north (Koryaks, Evens) and the south of Siberia and the adjacent territory of Northeast China (Buryats, Barghuts, Khamnigans). Using standard Ka/Ks analysis, it was found that all mtDNA genes in all studied regional population groups are subject to negative selection. The highest Ka/Ks values in different regional samples were found in almost the same set of genes encoding subunits of ATP synthase (ATP6, ATP8), NADH dehydrogenase complex (ND1, ND2, ND3), and cytochrome bc1 complex (CYB). The highest Ka/Ks value, indicating a relaxation of negative selection, was found in the ATP6 gene in the Siberian group. The results of the analysis performed using the FUBAR method (HyPhy software package) and aimed at searching for mtDNA codons under the influence of selection also showed the predominance of negative selection over positive selection in all population groups. In Siberian populations, nucleotide sites that are under positive selection and associated with mtDNA haplogroups were registered not in the north (which is expected under the assumption of adaptive evolution of mtDNA), but in the south of Siberia.

Mitogenomics of modern Mongolic-speaking populations

Here, we present a comprehensive data set of 489 complete mitogenomes (211 of which are new) from four Mongolic-speaking populations (Mongols, Barghuts, Khamnigans, and Buryats) to investigate their matrilineal genetic structure, ancestry and relationship with other ethnic groups. We show that along with very high levels of genetic diversity and lack of genetic differentiation, Mongolic-speaking populations exhibit strong genetic resemblance to East Asian populations of Chinese, Japanese, and Uyghurs. Phylogeographic analysis of complete mitogenomes reveals the presence of different components in the gene pools of modern Mongolic-speaking populations-the main East Eurasian component is represented by mtDNA lineages of East Asian, Siberian and autochthonous (the Baikal region/Mongolian) ancestry, whereas the less pronounced West Eurasian component can be ascribed to Europe and West Asia/Caucasus. We also observed that up to one third of the mtDNA subhaplogroups identified in Mongolic-speaking populations can be considered as Mongolic-specific with the coalescence age of most of them not exceeding 1.7 kya. This coincides well with the population size growth which started around 1.1 kya and is detectable only in the Bayesian Skyline Plot constructed based on Mongolic-specific mitogenomes. Our data suggest that the genetic structure established during the Mongol empire is still retained in present-day Mongolic-speaking populations.

The Bronze and Iron Age populations of the Armenian Highland in the genetic history of Armenians

OBJECTIVES

To investigate the biological diversity of the late Bronze and Iron Age populations in the Armenian Highland by nonmetric cranial traits, evaluate the genetic continuity in the development of the modern Armenian gene pool, and compare the results obtained with genetic data.

MATERIALS AND METHODS

Twenty-eight nonmetric cranial traits were scored on 498 adult crania from different late Bronze and Iron Age cemeteries, as well as from modern Armenians and other European populations. We carried out a biodistance analysis between populations using the mean measure of divergence (MMD) statistics, tested the spatial-temporal model of population structure, and assessed the diversity within the late Bronze and early Iron Ages by using the values of variability index (Fst).

RESULTS

The biodistance analysis revealed a close relationship among different ancient Armenian populations and between the average frequencies of the three sequential periods (late Bronze Age, early Iron Age I and II) and modern Armenians. A gradual increase of variability (Fst) within the three successive periods was observed.

DISCUSSION

The analysis of nonmetric trait data reflects deep roots and continuity in the formation of the Armenian population. Since at least the Late Bronze Age, owing to permanent isolation, no significant changes have occurred in the Armenian gene pool. An increase in variability over the successive periods reflects the process of population differentiation from a single gene pool while maintaining average trait frequencies. The congruence of the results obtained with the genetic data confirms, once more, the possibility of using nonmetric cranial traits as a proxy for genetic markers.