ГЕНЕТИКА, 2013, том 49, № 10, с. 1221-1228
ГЕНЕТИКА ЧЕЛОВЕКА
УДК 575.17:599.9
ASSESSMENT OF PATRILINEAL GENE POOL OF THE IRANIAN AZERIS
© 2013 A. Margaryan1, Z. Khachatryan1, A. Khudoyan2, L. Andonian3, L. Yepiskoposyan1
1Institute of Molecular Biology, National Academy of Sciences, Yerevan 0014, Armenia e-mail: imb@sci.am, e-mail: lepiskop@yahoo.com 2Institute of Man, Yerevan 0014, Armenia 3Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, 14155-6446, Tehran, Iran Received January 29, 2013
The Iranian Azeris are the largest ethno-linguistic minority in Iran who live mainly in the north-west part of the country. Located in the crossroad of ancient human migrations the Iranian Azeris bear the complicated historical influence of the region in their gene pool. Despite the importance of Iranian Azeris in reconstructing the historical event of the Middle-East, their (genetic) origin still remains heavily disputed. In this study we tried to evaluate the rates of genetic contribution of possible source populations (namely, indigenous Iranian, Caucasian, and Central Asian) in the gene pool of modern Iranian Azeris through paternally inherited Y-chromosomal 6 STR markers. The assessment of genetic distances reveals that the Iranian Azeris are mixed population with substantial North Caucasian genetic contribution being genetically much closer to their immediate neighboring ethnic groups. Based on the results of admixture analysis we can conclude that there are significant Caucasian and no visible Central Asian contribution to the gene pool of modern Iranian Azeris.
DOI: 10.7868/S0016675813100056
The Iranian Azeri population constitutes the largest ethno-linguistic minority of Iran [1], accounting for 16 percent of the country's population [2]. The historical background of this Turkic-speaking population has been the subject of numerous studies producing different, sometimes conflicting, opinions concerning their ethnic origin. Some scholars claim that Azeris are the direct descendants of the Central Asian Turkic nomads, based on the linguistic similarities [3, 4], whereas others point to their Iranian roots, linking the Azeris to the indigenous Iranian tribes such as the Medes, who dominated the territory of modern Iranian Azerbaijan between 900-700 BCE [5]. Considerable information is available also about the pre-Islamic Caucasian Albanians as having role in the ethnogenesis of modern-day Azerbaijanis [6, 7]. Still, the majority of sources view the Azeris as having a mixed ethnic origin tracing back to the autochthonous Caucasian and Iranian populations, who were certainly influenced by Turkic languages throughout several centuries of Turkish occupation of and domination in the region [8, 9].
To better understand the ethnic origin of this people, a short account of the historical, linguistic and cultural aspects is needed.
The historical name of Azerbaijan is believed to be originated from Atropates, the governor of Media in the Achaemenid Empire, who ruled over the region called after him as Atropatene. This later evolved into Azerbaijan (Atrpatakan, Adarbadagan, Adarbaygan) through Persian and Arabic linguistic influences [10]. Interestingly, archaeological evidences indicate that the Zoroastrian (the original Persian religion before
Christianity and Islam) holy places were mostly located in Atropatene [11].
The expanding waves ofArab-Muslims invasions in the seventh century resulted in Islamization of most of the region, including Iranian Azerbaijan [12]. According to Minorsky, the original sedentary population of Azerbaijan at that time mostly spoke Old Azari language [13], which is believed to belong to the northwestern group of Iranian languages [14].
However, Old Azari gradually lost its importance as the prevalent language, due to the Turkification of the region [13]. The Turkic language entered the region as a result of the great migration waves of Central Asian Altaic-speaking groups into Asia Minor in the eleventh century and the continued influx of Turkic-speaking populations in ensuing centuries. The Turkification process of the region was so successful that by the beginning of the sixteenth century, when the Safa-vid dynasty was established over the region, there was scarcely any trace of the Old Azari [15].
Interesting data were also obtained on anthropometric study of the modern Iranian Azeris [16], which are shown to be autochthonous population of the area based on their cephalometric features. Particularly, the study demonstrates that similar to other indigenous populations of the region, such as Persians and Kurds, Azeris belong to the gracile variant ofAssyroid anthropological type of the Caucasian branch.
Few studies have been done on the genetic history of Iranian Azeris [17—19] which prove the Turkification of the region rather than Azeri being of Turkic origin, nevertheless, the historically motivated contentious opinions
concerning the group's origin remain obscure. Thus, the aim of this work is essentially to assess the rates of genetic contribution of possible source populations (namely, indigenous Iranian, Caucasian, and Central Asian) in the gene pool of modern Iranian Azeris.
MATERIALS AND METHODS
Subjects and collection of DNA. The study subjects were selected to represent the Iranian Azeris (Ir_Azeri, n = 99) and neighbouring populations of the Middle East and the Caucasus. Buccal swab specimens were collected from ethnic Azeri men currently living in Tabriz, Iran. All donors were selected only if their paternal grandfathers were from the same region and they were unrelated to other donors at the grandfather level. Samples were collected anonymously and informed consent was obtained from all individuals before the specimens were taken. Detailed information concerning the genotyping of Y-chromosomal markers is presented in our previous publication [17], the results of genotyping are presented in the Supplemental Table.
Comparative data sets. Our samples were compared with ethnic and geographic groups representing the indigenous peoples of neighboring countries: Eastern Turkey (ET, n = 82) [20]; Azerbaijan (Az'jan, n = 40), Mongols (n = 422), Georgians (n = 106) [21]; Armenians from historical western Armenia (currently in Turkey) (W_Arm, n = 400) and Syunik region (Syunik, n = 296) [21, unpublished data]; Turkmens (n = 51) [22]; Sephardic Jews (S_Jews, n = 78), Palestinian Arabs (Palestinians, n = 143), Bedouins (n = 32), Iraqi Kurds (Kurds, n = 95) [23]; Indians (n = 250), Yemenis (n = 93) and Adyghes (n = 242) kindly provided by our colleagues at the Centre for Genetic Anthropology, UCL, UK (unpublished data); Uzbeks (n = 39) [24]; Pakistanis (n = 718) [25]; Ossetians (n = 125), Lezghins (n = 79) and Dargins (n = 100) [26]; Fars (n = 96) and Iranian Armenians (Ir_Arm, n = 89) [27]; Iranians (n = 309) [28]; Yezidis (n = 202) [29]; Tajiks (n = 22), Kyrgyz (n = 37) and Uyghurs (n = 33) [30]. All samples were typed for the same set of 6 Y chromosomal STR markers (DYS19, DYS388, DYS390, DYS391, DYS392, and DYS393).
Statistical analysis. Pairwise RST genetic distances were estimated from analysis of molecular variance (AMOVA) Ost values with the aid of Arlequin program v. 3.5 [31]. Tests for significant population differentiation were carried out using the exact test for population differentiation [32]. Principal Coordinates Analysis was conducted on similarity matrices based on RST genetic distances with the use of the GenStat program.
Signature haplotype analysis (high frequency modal haplotypes and modal clusters) was performed with Microsoft Excel [33-35]. PHYLIP software [36] was used to obtain an unrooted phylogenetic tree diagram based on the RST genetic distances by using the Neighbour-Joining (NJ) method.
The admixture proportions of the three hypothesized populations (4 groups) in the Iranian Azeris gene pool were assessed using the ADMIX 2.0 program [37]. Estimates of the admixture coefficients and their SEs were calculated based on microsatellite data using 10000 bootstrap replicates with the mutation rate of 2.7 x 10-5 per year as described by Zhivotovsky et al. [38].
RESULTS NRY haplotypes
The six microsatellites define a total of 838 haplotypes in 27 populations. The most frequent haplotype of the Iranian Azeris (5.05%) is also the modal one in Azerbaijanis (7.5%), Fars (9.38%) and Kurds (11.58%). This haplotype is also highly encountered in Yezidis (11.88%), population of eastern Turkey (6.1%), Iranians (3.24%), Yemenis (4.3%), Armenians from Syunik region (5.41%) and historical western Armenia (4.5%), and Adyghes (5.79%). In contrast, the Azeri modal haplotype is totally absent in some Central Asians (Tajiks, Kyrgyz, Uyghurs, Uzbeks, and Mongols), North Caucasians (Lezghin, Dargin) and Arab Bedouins. Weak traces of this haplo-type are detected in the rest of populations considered as comparative data sets. A similar pattern of haplo-type distribution is observed while comparing the modal clusters defined as a modal haplotype plus its one-step neighbors.
Genetic distances
We have calculated the RST genetic distances to evaluate the level of genetic affinity between Iranian Azeris and comparative datasets. Based on the exact test of population differentiation no significant genetic difference (p > 0.05) is detected between the Azeris from one side and the Azerbaijanis, population of eastern Turkey and Sephardic Jews, from the other side. Statistically significant differences (p < 0.05) were observed between the Azeris and the other comparative data sets. To visualize the pattern of genetic proximity among the Azeris and neighbouring ethnic groups, we have conducted a PCO analysis based on the RST values (Fig. 1).
The figure shows that there are three distinct groups of the populations studied. The first one includes the three Arabic ethnic groups (Bedouins, Yemenis, and Palestinians) and is
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