HLA class I and class II polymorphism in a population from south-eastern Tunisia (Gabes Area).

The gene frequencies of HLA class I and class II alleles were investigated in 95 healthy Tunisian individuals from Gabes. Our aim was to compare the genetic relationship between Gabesians and Mediterraneans and sub-Sahara Africans using genetic distances, Neighbour-Joining dendrograms, correspondence and haplotypes analysis, thereby providing additional information about evolutionary history of modern-day Tunisians. Subjects were unrelated and of both genders, and HLA class I and class II genes were genotyped using the polymerase chain reaction-sequence specific primer (PCR-SSO) technique. Our data show that south-eastern Tunisians (Gabes area) are related to present-day North Africans (Algerians, Moroccans, Tunisians) and Iberians (Spaniards, Basques), and along with other North Africans, appear to be genetically related to Berbers, an indication that the Arab invasion (7th-11th centuries) of North Africa had minimal contribution on the HLA makeup of North Africans. On the other hand, Iberians including Spaniards and Basques show relatedness to (native Tunisian) Berbers, suggesting that the gene flow of 7th century AD invaders was also low in Iberians. In conclusion, the successive invasions of North Africa in general, and Tunisia in particular, did not modify markedly the genetic makeup of present-day Tunisians. With the exception of Greeks who have a sub-Saharan genetic profile, all Mediterranean populations depict a typical mediterranean substratum.

HLA class I and class II polymorphisms in Tunisian Berbers.

BACKGROUND: The HLA polymorphism is a powerful genetic tool to study population origins. By analysing allele frequencies and haplotypes in different populations, it is possible to identify ethnic groups and establish the genetic relationships among them. AIM: The Berber (endogenous Tunisians) HLA class I and class II genotypes were analysed and compared with those of Mediterranean and Sub-Saharan African communities using genetic distances, Neighbour-Joining dendrograms, correspondence and haplotype analysis. SUBJECTS AND METHODS: One hundred and five unrelated Berbers were typed for HLA class I (A, B) and class II (DRB1, DQB1) gene alleles using reverse dot-blot hybridization. RESULTS: High frequencies of A*0201 (24.76%), A*3402 (22.38%) and B*44 (32.85%) alleles were recorded for Berbers, the highest recorded for Mediterranean and North African populations. This study shows a close relatedness of Tunisian Berbers to other Tunisians, North Africans and Iberians. CONCLUSION: The apparent relatedness of Tunisian Berbers to present-day (North African) Tunisians, Algerians and Moroccans suggests that the Arab invasion of North Africa (7(th)-11(th) centuries AD) did not significantly impact the genetic makeup of North Africans. Furthermore, Tunisian Berbers appear to be closely related to Iberians (Spaniards and Basques), indicating that the 7(th) century AD gene flow of invaders was low in Iberians and that the main part of their genetic pool came after the Northward Saharan migration, when hyper-arid conditions were established in Sahara (before 6000 BC). Other studied populations belong to the old Mediterranean substratum, which has been present in the area since pre-Neolithic times. This study indicates a higher proportion of Iberian than Arab ancestry in Tunisian Berbers, which is of value in evaluating the evolutionary history of present-day Tunisians. Greeks seem to share genetic HLA features (Chr 6) with Sub-Saharans. The relatedness of Greeks to Sub-Saharans has been confirmed by other studies based on chromosome 7 genetic markers.

The contribution of HLA class I and II alleles and haplotypes to the investigation of the evolutionary history of Tunisians.

The frequencies of HLA class I and class II alleles and haplotypes of 104 healthy unrelated Tunisians were analyzed by high-resolution PCR-reverse dot blot hybridization, and was compared with other Mediterranean and Sub-Saharan Africans using genetic distances measurements, Neighbor-joining dendrograms, correspondence, and extended haplotypes analysis. The most frequent HLA class I A alleles were A*02, A*24, and A*30, while the most frequent B alleles were B*44, followed by B*50, B*51, and B*07. Among HLA class II DRB alleles analyzed, the most frequent were DRB1*0301, DRB1*0701, DRB1*1501, followed by DRB1*1303 and DRB1*0102; for DQB1, they were DQB1*0301 and DQB1*0201. Three-locus haplotype analysis revealed that A*03-B*07-DRB1*1503 and A*02-B*44-DRB1*0402 were the most common HLA class I and II haplotypes in this population. Compared with other communities, our result indicate that Tunisians are very related to North Africans and Western Europeans, particularly Iberians, and that Tunisians, Algerians, and Moroccans are close to Berbers suggesting little genetic contribution of Arabs who populated the area in 7th to 8th century AD. The similarities and differences between Tunisians and neighboring and related communities in HLA genotype distribution provide basic information for further studies of the MHC heterogeneity among Mediterranean and North African countries, and as reference for further anthropological studies.

HLA genes in Southern Tunisians (Ghannouch area) and their relationship with other Mediterraneans.

South Tunisian HLA gene profile has studied for the first time. HLA-A, -B, -DRB1 and -DQB1 allele frequencies of Ghannouch have been compared with those of neighboring populations, other Mediterraneans and Sub-Saharans. Their relatedness has been tested by genetic distances, Neighbor-Joining dendrograms and correspondence analyses. Our HLA data show that both southern from Ghannouch and northern Tunisians are of a Berber substratum in spite of the successive incursions (particularly, the 7th-8th century A.D. Arab invasion) occurred in Tunisia. It is also the case of other North Africans and Iberians. This present study confirms the relatedness of Greeks to Sub-Saharan populations. This suggests that there was an admixture between the Greeks and Sub-Saharans probably during Pharaonic period or after natural catastrophes (dryness) occurred in Sahara.

Prevalence of C282Y and H63D mutations in the haemochromatosis (HFE) gene in Tunisian population.

The studies of the HFE mutations: H63D and C282Y in North African populations have revealed the extreme rarity or even the absence of the C282Y mutation. We have examined 1140 chromosomes (570 Tunisian people) for the presence of the two HFE mutations by PCR-RFLP analysis. We have found that the allele frequencies are, respectively, 15.17% (+/-2.1%) for the H63D and 0.09% (+/-0.17%) for the C282Y. These results are consistent with the worldwide spread of the H63D mutation and the north European restriction of the C282Y. This study will be completed by determining whether homozygote trait for H63D and associated risk factors (beta thalassémia) can lead to iron overload in Tunisia.