Amel Ben Ammar El Gaaied

Female gene pools of Berber and Arab neighboring communities in central Tunisia: microstructure of mtDNA variation in North Africa.

North African populations are considered genetically closer to Eurasians than to sub-Saharans. However, they display a considerably high mtDNA heterogeneity among them, namely in the frequencies of the U6, East African, and sub-Saharan haplogroups. In this study, we describe and compare the female gene pools of two neighboring Tunisian populations, Kesra (Berber) and Zriba (non-Berber), which have contrasting historical backgrounds. Both populations presented lower diversity values than those observed for other North African populations, and they were the only populations not showing significant negative Fus Fs values. Kesra displayed a much higher proportion of typical sub-Saharan haplotypes (49%, including 4.2% of M1 haplogroup) than Zriba (8%). With respect to U6 sequences, frequencies were low (2% in Kesra and 8% in Zriba), and all belonged to the subhaplogroup U6a. An analysis of these data in the context of North Africa reveals that the emerging picture is complex, because Zriba would match the profile of a Berber Moroccan population, whereas Kesra, which shows twice the frequency of sub-Saharan lineages normally observed in northern coastal populations, would match a western Saharan population except for the low U6 frequency. The North African patchy mtDNA landscape has no parallel in other regions of the world and increasing the number of sampled populations has not been accompanied by any substantial increase in our understanding of its phylogeography. Available data up to now rely on sampling small, scattered populations, although they are carefully characterized in terms of their ethnic, linguistic, and historical backgrounds. It is therefore doubtful that this picture truly represents the complex historical demography of the region rather than being just the result of the type of samplings performed so far.

Internal Diversification of Mitochondrial Haplogroup R0a Reveals Post-Last Glacial Maximum Demographic Expansions in South Arabia

Widespread interest in the first successful Out of Africa dispersal of modern humans ∼60-80 thousand years ago via a southern migration route has overshadowed the study of later periods of South Arabian prehistory. In this work, we show that the post-Last Glacial Maximum period of the past 20,000 years, during which climatic conditions were becoming more hospitable, has been a significant time in the formation of the extant genetic composition and population structure of this region. This conclusion is supported by the internal diversification displayed in the highly resolved phylogenetic tree of 89 whole mitochondrial genomes (71 being newly presented here) for haplogroup R0a-the most frequent and widespread haplogroup in Arabia. Additionally, two geographically specific clades (R0a1a1a and R0a2f1) have been identified in non-Arabic speaking peoples such as the Soqotri and Mahri living in the southern part of the Arabian Peninsula where a past refugium was identified by independent archaeological studies. Estimates of time to the most recent common ancestor of these lineages match the earliest archaeological evidence for seafaring activity in the peninsula in the sixth millennium BC.

Combined effect of smoking and inherited polymorphisms in arylamine N-acetyltransferase 2, glutathione S-transferases M1 and T1 on bladder cancer in a Tunisian population

Cigarette smoking is the predominant risk factor for bladder cancer in males and females. The tobacco carcinogens are metabolized by various xenobiotic metabolizing enzymes, such as the super-families of N-acetyltransferases (NAT) and glutathione S-transferases (GST). Polymorphisms in NAT and GST genes alter the ability of these enzymes to metabolize carcinogens. We have conducted this case-control study to assess the role of smoking, slow NAT2 variants, and GSTM1 and GSTT1 null genotypes in bladder cancer development in North Tunisia. In all groups of patients, we have shown that GSTM1 and GSTT1 null genotypes did not appear to be a factor affecting bladder cancer susceptibility. For the NAT2 slow acetylator genotype, the NAT2*5/*7 diplotype was found to have a 7-fold increased risk of bladder (OR=7.14; 95% CI: 1.30-51.41). Furthermore, we found that NAT2 slow acetylator individuals temporarily carrying wild-type GSTT1 or GSTM1 null genotypes have a strong increased risk of bladder cancer (OR= 26 and 22.17, respectively). This cumulative effect was estimated at 12 for smokers harboring slow or an intermediate NAT2, GSTM1 null, and wild-type GSTT1 genotypes compared to non-smokers carrying rapid NAT2, wild-type GSTM,1 and GSTT1 null genotypes (p=0.02; OR=12; CI 95% 1-323.76).

Population history of the Red Sea—genetic exchanges between the Arabian Peninsula and East Africa signaled in the mitochondrial DNA HV1 haplogroup

Archaeological studies have revealed cultural connections between the two sides of the Red Sea dating to prehistory. The issue has still not been properly addressed, however, by archaeogenetics. We focus our attention here on the mitochondrial haplogroup HV1 that is present in both the Arabian Peninsula and East Africa. The internal variation of 38 complete mitochondrial DNA sequences (20 of them presented here for the first time) affiliated into this haplogroup testify to its emergence during the late glacial maximum, most probably in the Near East, with subsequent dispersion via population expansions when climatic conditions improved. Detailed phylogeography of HV1 sequences shows that more recent demographic upheavals likely contributed to their spread from West Arabia to East Africa, a finding concordant with archaeological records suggesting intensive maritime trade in the Red Sea from the sixth millennium BC onwards. Closer genetic exchanges are apparent between the Horn of Africa and Yemen, while Egyptian HV1 haplotypes seem to be more similar to the Near Eastern ones.

The role of CYP2D6*4 variant in bladder cancer susceptibility in Tunisian patients

CYP2D6 enzyme is implicated in the metabolism of drugs and nicotine. Genetic variability within CYP2D6, results in different CYP2D6 phenotypes. Inheritance of polymorphic CYP2D6 metabolizing enzyme is likely to be an important determinant of inter-individual variations in susceptibility to cancer. In this work, we have conducted a case control study in order to assess the role of CYP2D6*4 variant in bladder cancer development in a Tunisian cohort. A total of 80 patients with TCC of bladder cancer and 109 healthy controls were included in the present study. The frequency of CYP2D6*4 allele, characterized by loss of BstNI site, was observed in 8.25% of healthy volunteers and in 10.62% of patients. The CYP2D6*4/CYP2D6*4 genotype was observed in only 2.75% of controls and was absent in cases. In all group of patients, the CYP2D6*4 allele did not appear to influence bladder cancer susceptibility (p > 0.05). A similar result was obtained when we stratified cases group according to tobacco status. Conversely, patients carrying the BstNI site at the homozygous state, mostly combined as homozygous wild genotype, could be at more risk of bladder cancer invasiveness than those having the heterozygous genotype.

Identification of the CCR5-Δ32 HIV resistance allele and new mutations of the CCR5 gene in different Tunisian populations

Polymorphisms in some chemokine receptor genes are associated with susceptibility to and progression of human immunodeficiency virus-1 (HIV-1) infection. Most mutations detected in the CC-chemokine receptor 5 (CCR5) gene are specific to different populations. In this study, we focused on polymorphisms of the CCR5 coding region in three healthy populations from Tunisia, corresponding to a cosmopolitan population from Tunis, and two isolated Berber populations. In addition to the CCR5-Delta32 deletion, eleven single nucleotide polymorphisms were detected. Some of these point mutations were associated with the same genotype and even the same haplotype. The (L55Q-C101X), I124, V131F, T143N, A159V, I237, T239A and G301R alleles have not been described previously, whereas the CCR5-Delta32, L55Q, A335V and Y339F variants have already been reported in the literature. The distribution and frequency of these variants were different among the three groups studied, a result in agreement with the mosaic genetic structure of the Tunisian population. To determine whether these alleles affect HIV-1 transmission, we compared allele frequencies between healthy and HIV-1 infected individuals from Tunis. The frequency of the CCR5-Delta32 variant was significantly different between the two groups, leading us to conclude that this mutation might confer protection against HIV infection in Tunisian populations.

An investigation of the genetic diversity of the Kerkennah islands and Mahdia (Tunisia) using biparental markers

Abstract Background: Kerkennah is one of the main inhabited islands of Tunisia. The origin of the population of Kerkennah has not been established and no well-defined ethnic groups have been identified nor are genetic studies available. Mahdia, a Tunisian coastal city, has a long history dating back to ancient times. Aim: To discover the genetic diversity of the two studied populations and analyse their relationships with other Mediterranean populations. Subject and methods: Seven human-specific Alu insertion polymorphisms were typed in 99 individuals born in Kerkennah and Mahdia. Results: A neighbour-joining tree and MDS multidimensional scaling analysis showed that these Tunisian populations are scattered amongst North African and Europeans populations, indicating their high genetic diversity and mosaic aspect. The important finding of this study was the proximity of Kerkennah to Moroccans. Hence, the actual gene pool of this insular population may descend from the ancestral population known to be of Moroccan origin. Concerning Mahdia, its closeness to Eurasian populations and some Tunisian groups reflected a high Eurasian genetic component for North African populations and confirmed their heterogeneity. Conclusion: The strategic location of the two studied populations and their fortifications have allowed them to play a leading role in the Mediterranean basin.

The impact of smoking and polymorphic enzymes of xenobiotic metabolism on the stage of bladder tumors: a generalized ordered logistic regression analysis.

Cigarette smoking is the predominant risk factor for bladder cancer in males and females. The tobacco carcinogens are metabolized by various xenobiotic metabolizing enzymes such as N-acetyltransferases (NAT) and glutathione S-transferases (GST). Polymorphisms in NAT and GST genes alter the ability of these enzymes to metabolize carcinogens. In this paper, we conduct a statistical analysis based on logistic regressions to assess the impact of smoking and metabolizing enzyme genotypes on the risk to develop bladder cancer using a case–control study from Tunisia. We also use the generalized ordered logistic model to investigate whether these factors do have an impact on the progression of bladder tumors.

Akt activation correlates with the tumor aggressiveness in Tunisian patients with bladder cancer

Various studies in western countries found Akt amplification to be a frequent event in human cancers, including bladder, but the correlation with clinicopathological features is controversial. Such studies have not been reported in African populations, including Tunisians. The purpose of this study was to assess expression of the phosphorylated/activated forms of Akt in tumors from Tunisian patients with bladder cancer and to correlate its expression with pathological and clinical parameters of the disease. The study included 72 patients of whom 34 were diagnosed as low- to medium-grade and 35 as high-grade; 30 were muscle stage and 39 non-muscle stage. Primary tumors from these patients, normal adjacent tissues, or bladder cancer cell-lines were analyzed for Ser473 phosphorylated Akt expression by Western blot. Seventy-two percent of primary tumors from patients with bladder cancer had increased levels of p-Akt. The p-Akt levels in patients with high-grade bladder cancer were significantly elevated compared to patients with low- or medium-grade bladder cancer. In invasive carcinoma, the p-Akt level was significantly higher than in superficial non-invasive bladder tumors. Concerning the influence of tobacco on Akt activation, no significant differences of p-Akt expression were found between non-smoker and smoker patients. Altogether, our results suggest that Akt activation can provide useful prognostic information and that tobacco represents a serious risk factor for recurrence in a cohort of Tunisian patients.