This is the first genetic anthropology study on Arabs in MENA (Middle East and North Africa) region. The present meta-analysis included 100 populations from 36 Arab and non-Arab communities, comprising 16,006 individuals, and evaluates the genetic profile of Arabs using HLA class I (A, B) and class II (DRB1, DQB1) genes. A total of 56 Arab populations comprising 10,283 individuals were selected from several databases, and were compared with 44 Mediterranean, Asian, and sub-Saharan populations. The most frequent alleles in Arabs are A*01, A*02, B*35, B*51, DRB1*03:01, DRB1*07:01, DQB1*02:01, and DQB1*03:01, while DRB1*03:01-DQB1*02:01 and DRB1*07:01-DQB1*02:02 are the most frequent class II haplotypes. Dendrograms, correspondence analyses, genetic distances, and haplotype analysis indicate that Arabs could be stratified into four groups. The first consists of North Africans (Algerians, Tunisians, Moroccans, and Libyans), and the first Arabian Peninsula cluster (Saudis, Kuwaitis, and Yemenis), who appear to be related to Western Mediterraneans, including Iberians; this might be explained for a massive migration into these areas when Sahara underwent a relatively rapid desiccation, starting about 10,000 years BC. The second includes Levantine Arabs (Palestinians, Jordanians, Lebanese, and Syrians), along with Iraqi and Egyptians, who are related to Eastern Mediterraneans. The third comprises Sudanese and Comorians, who tend to cluster with Sub-Saharans. The fourth comprises the second Arabian Peninsula cluster, made up of Omanis, Emiratis, and Bahrainis. It is noteworthy that the two large minorities (Berbers and Kurds) are indigenous (autochthonous), and are not genetically different from “host” and neighboring populations. In conclusion, this study confirmed high genetic heterogeneity among present-day Arabs, and especially those of the Arabian Peninsula.

The south of Tunisia is characterized by marked ethnic diversity, highlighted by the coexistence of native Berbers with Blacks, Jews and Arab-speaking populations. Despite this heterogeneity, genetic anthropology studies investigating the origin of current Southern Tunisians were rarely reported. We examined human leukocyte antigen (HLA) class I (A, B) and class II (DRB1, DQB1) gene profiles of 250 unrelated Southern Tunisians, and compared them with those of Arab-speaking communities, along with Mediterranean and sub-Sahara African populations using genetic distances, neighbor-joining dendrograms, correspondence and haplotype analysis. In total, 137 HLA alleles were detected, which comprised 32 HLA-A, 52 HLA-B, 32 DRB1 and 21 DQB1 alleles. The most frequent alleles were HLA-A*02:01(18.02%), HLA-B*50:01 (9.11%), HLA-DRB1*07:01 (22.06%) and HLA-DQB1*02:01 (17.21%). All pairs of HLA loci show significant linkage disequilibrium. The four loci depict negative F (the normalized deviate of the homozygosity) values indicating an overall trend to balancing selection. Southern Tunisians appear to be closely related to others Tunisian populations including Berbers, North Africans and Iberians. On the contrary, Southern Tunisians were distinct from Palestinian, Lebanese and Jordanian Middle Eastern Arab-speaking population, despite the deep Arab incursions and Arabization that affected Southern Tunisia. In addition, Southern Tunisians were distant from many sub-Saharan communities, evidenced by genetic distance analysis. Collectively, this indicates a limited genetic contribution of Arab invasion and Black caravans on the makeup of Southern Tunisian gene pool.

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In view of its distinct geographical location and relatively small area, Tunisia witnessed the presence of many civilizations and ethnic groups throughout history, thereby questioning the origin of present-day Tunisian population. We investigated HLA class I and class II gene profiles in Tunisians, and compared this profile with those of Mediterranean and Sub-Sahara African populations. A total of 376 unrelated Tunisian individuals of both genders were genotyped for HLA class I (A, B) and class II (DRB1, DQB1), using reverse dot-blot hybridization (PCR-SSO) method. Statistical analysis was performed using Arlequin software. Phylogenetic trees were constructed by DISPAN software, and correspondence analysis was carried out by VISTA software. One hundred fifty-three HLA alleles were identified in the studied sample, which comprised 41, 50, 40 and 22 alleles at HLA-A,-B,-DRB1 and -DQB1 loci, respectively. The most frequent alleles were HLA-A*02:01 (16.76%), HLA-B*44:02/03 (17.82%), HLA-DRB1*07:01 (19.02%), and HLA-DQB1*03:01 (17.95%). Four-locus haplotype analysis identified HLA-A*02:01-B*50:01-DRB1*07:01-DQB1*02:02 (2.2%) as the common haplotype in Tunisians. Compared to other nearby populations, Tunisians appear to be genetically related to Western Mediterranean population, in particular North Africans and Berbers. In conclusion, HLA genotype results indicate that Tunisians are related to present-day North Africans, Berbers and to Iberians, but not to Eastern Arabs (Palestinians, Jordanians and Lebanese). This suggests that the genetic contribution of Arab invasion of 7th-11th century A.D. had little impact of the North African gene pool.

The molecular association of HLA class II with type 1 diabetes (T1DM) was investigated in Tunisian Arabs using 3 kinds of analyses. The first was a case-control association study, using Relative Predispositional Effects method, involved 137 T1DM cases and 258 control subjects. The second was family-based association-linkage study, using Transmission Disequilibrium Test, and covering 50 Tunisian families comprising 73 T1DM patients and 100 parents. The third was a wide correlation study between 4 DRB1 alleles (DRB1*03, *04, *11, *15) and T1DM in 52 countries, using Spearman’s Rho. Results from Case-control and family-based association studies showed that DRB1*03 and DRB1*04 alleles predispose to T1DM in Tunisian Arabs. Conversely, only DRB1*11 was protective for T1DM. DRB1*04-DQB1*03 haplotype was consistently associated positively with T1DM; DRB1*03/DRB1*04 genotype had the highest risk of T1DM development. Compared to DRB1*03, HLA-DRB1*04 was associated with higher T1DM incidence. Thus, the contribution of HLA class II to T1DM genetic susceptibility must be evaluated with regards to specific HLA alleles, genotypes, and haplotypes, and also ethnic and racial background.