Variation of DAT1 VNTR Alleles and Genotypes Among Old Ethnic Groups in Mesopotamia to the Oxus Region

Abstract

Variation of a VNTR in the DAT1 gene in seven ethnic groups of the Middle East was used to infer the history and affinities of these groups. The populations consisted of Assyrian, Jewish, Zoroastrian, Armenian, Turkmen, and Arab peoples of Iran, Iraq, and Kuwait. Three hundred forty subjects from these seven ethnic groups were screened for DAT1. DAT1 VNTR genotyping showed 3, 6, 7, 8, 9, 10, 11, and 12 alleles in the samples. Analysis of these data revealed differentiation and relationship among the populations. In this region, which covers an area of 2-2.5 million km^sup 2^, the influence of geography and especially of linguistic characteristics has had potentially major effects on differentiation. Religion also has played a major role in imposing restrictions on some ethnic groups, who as a consequence have maintained their community. Overall, these ethnic groups showed greater heterogeneity compared to other populations.

KEY WORDS: DAT1, VNTR, ASSYRIANS, JEWS, ZOROASTRIANS, ARMENIANS, TURKMEN,ARABS, IRAN, IRAQ, KUWAIT, MESOPOTAMIA, DIVERSITY, ETHNIC GROUPS.

The modern Mesopotamia (entire Tigris-Euphrates valley in southwest Asia) to Oxus (Amu Dar'ya) area includes many lands that are inhabited by miscellaneous ethnic groups with civilizations dating back 5,000-6,000 years. This region provides a unique opportunity to investigate the influence of geography, language, and possibly religion on the genetic structure of a human population. The studied area includes Iran, Iraq, and Kuwait, which can also act as representatives of other neighboring countries, such as Armenia, Turkmenistan, and Israel.

The DAT1 VNTR is a minisatellite used to calculate differentiation and affinity from a population genetic aspect. This marker, which has a 40-bp variable number of tandem repeats (VNTR), exists in the noncoding region of exon 15 of the DAT1 gene. Reported variability in the number of alleles at this locus ranges from 3 to 13 in white and black populations (Mitchell et al. 2000; Vandenbergh et al. 1992).

As to the role of DATl, assessment of the DAT1 VNTR polymorphism is a convenient way to clarify population relationships, and rare alleles at this locus may be particularly valuable in understanding the extent of genetic similarity among neighboring groups and in situations where admixture is suspected (Di-Maio et al. 2003; Georgieva et al. 2002). The observed pattern of genetic variation could be a tool to assess linguistic-geographic barriers that increased genetic changes. On the other hand, probably genetic and linguistic diversity have often been shaped by demographic changes. Hence the DATl VNTR was analyzed in the populations of this study because of the populations' high variation, different origins, languages, and demographic characters, and history going as far back as 6,000 years. Restrictions on some populations because of limitations imposed by their religions were also of special interest to this study.

Materials and Methods

Samples. Three hundred forty subjects were randomly selected from seven ethnic groups residing in Iran, Iraq, and Kuwait. These populations included Assyrians, Jews, Zoroastrians, Armenians, and Turkmen (representing ethnic groups from Iran, restricted by rules of their religion), and the Iraqi and Kuwaiti populations from Iraq and Kuwait. The first five ethnic groups are considered minority ethnic groups in Iran. These five ethnic groups make up less than 1 % of the Iranian population. Table 1 shows more detailed information on each ethnic group.

The Assyrians are the main residents of present-day Mesopotamia. They speak Aramaic. Their religion, cultural, and linguistic characteristics are completely different from the Arabs, Kurdish, Persian, and Turkish ethnic groups. Currently, they are dispersed in Iraq, Iran, and North America. In Iran they are concentrated in the two cities of Tehran and Uremia, where sampling from this ethnic group was performed.

Jews who live in Iran are referred to as Persian Jews or Parsim; their presence in Iran dates back to approximately 600 B.C. As the second main community of Jews in the Middle East, this group speaks Persian as their maternal language, and their dispersion is limited to the main cities of Iran, such as Tehran in the north and Yazd and Isfahan in the center. Samples representative of this community were mostly taken from Tehran.

The Zoroastrians are believed to be one of the first residents of Iran whose religion and philosophy are based on the teachings ascribed to the prophet Zoroaster. They have kept their beliefs to this day, even after the Arab invasion of the Iran plateau. However, many Zoroastrians migrated to the Indian subcontinent as a result of pressure imposed on them by Islamic rulers. Sample collection from this community was limited to the city of Yazd, where the majority of Zoroastrians are concentrated.

The Armenians are a nation and an ethnic group originating from the Caucasus and eastern Anatolia, where a large concentration of this community has remained, especially in Armenia. However, many of them are also scattered elsewhere throughout the world, such as Iran, where the term Parskahay is used to refer to the Armenians who live in this country. Today the Armenians are Iran's largest religious minority. Tehran was the main area where samples for this ethnic group were collected.