Mitochondrial DNA analysis of Tunisians reveals a mosaic genetic structure with recent population expansion.

Tunisia is a country of great interest for human population genetics due to its strategic geographic position and rich human settlement history. These factors significantly contributed to the genetic makeup of present-day Tunisians harbouring components of diverse geographic origins. Here, we investigated the genetic structure of Tunisians by performing a mitochondrial DNA (mtDNA) comparison of 15 Tunisian population groups, in order to explore their complex genetic landscape. All Tunisian data were also analysed against 40 worldwide populations. Statistical results (Tajima's D and Fu's FS tests) suggested recent population expansion for the majority of studied populations, as well as showed (AMOVA test) that all populations were significantly different from each other, which is evidence of population structure even if it is not guided by geographic and ethnic effects. Gene flow analysis revealed the assignment of Tunisians to multiple ancestries, which agrees with their genetic heterogeneity. The resulting picture for the mtDNA pool confirms the evidence of a recent expansion of the Tunisian population and is in accordance with a mosaic structure, composed by North African, Middle Easterner, European and Sub-Saharan lineages, resulting from a complex settlement history.

Assessing human genetic diversity in Tunisian Berber populations by Alu insertion polymorphisms.

BACKGROUND: The most recent Alu insertions reveal different series of characteristics such as stability that make them particularly suitable genetic markers for human biological studies. AIM: Six human-specific Alu insertion polymorphisms were typed in two Tunisian Berber populations with the aim of analysing the genetic diversity of these two communities and the genetic relationships between this region of North Africa and other populations. SUBJECTS AND METHODS: Forty-seven Berbers from Sejnane and 33 from Takrouna were sampled. Alu insertion polymorphism was analysed using PCR with loci specific primers. RESULTS: A similar level of gene diversity was detected in Sejnane and Takrouna populations. PC results revealed genetic affinities between these two populations and some Eurasian populations (Germany, Genova and Syria). In contrast, there is a differentiation between these two Berber communities and North African and Iberian populations. CONCLUSION: The results of this study confirm the heterogeneity of Berbers in North Africa, which suggests their diverse origins. In the case of Sejnane and Takrouna populations, these results are in line with an ancient Euro Mediterranean background that has already been studied by archaeologists, particularly for the population of Sejnane.

Genetic analysis of the SNPforID 34-plex ancestry informative SNP panel in Tunisian and Libyan populations.

A total of 149 unrelated and healthy individuals comprising: Tunisian Berbers, Tunisians with Andalusian origin and Libyans were typed with the SNPforID 34-plex ancestry informative marker (AIM) SNP panel. Results of 31 of the 34 SNPs are presented and no deviations from Hardy-Weinberg equilibrium were observed after Bonferroni correction (p=0.00161) except rs722098 (p=0.0000). Comparisons of allele frequencies showed high divergence values between North Africans and Europeans (δ>30%) in markers: rs4540055 (allele A) and rs16891982. Our study adds data that can be used as training set genotypes for future ancestry investigations in forensic cases and suggests these AIM-SNPs can successfully differentiate North Africans and Mediterranean Europeans.

Germline HVR-II mitochondrial polymorphisms associated with breast cancer in Tunisian women.

A high incidence of somatic mtDNA polymorphisms has been reported in a wide variety of human cancers; some of them have been proposed as markers for the early detection of breast cancer. However, little attention has been paid to the potential of germline mitochondrial sequence variations as genetic risk factors for cancer. We performed a case-control study of 70 unrelated Tunisian women with breast cancer and 80 healthy age- and gender-matched blood donors, taking into account clinicopathological data, to evaluate germline polymorphism of mitochondrial HVR-II region as a genetic risk factor for breast cancer. Through direct sequencing, we detected 351 polymorphisms in controls and 248 variants in patients, with 47 and 39 segregating sites, respectively. In both groups, more than 50% of the polymorphisms were due to four variants: 315 ins C, 309 ins C, 263 A>G, and 73 A>G. The HVR-II sequences were also classified into haplotypes on the basis of the polymorphisms. Fifty-nine different haplotypes were found, 20 of them shared between patients and controls. Both groups had specific haplotypes, 18 in breast cancer patients and 21 in controls. Statistical analysis revealed a weak protective effect against breast cancer risk for two mitochondrial polymorphisms - 152 T>C (odds ratio (OR) = 0.33, 95% confidence interval (CI) = 0.12-0.91) and 263 A>G (OR = 0.17, 95%CI = 0.06-0.47). In contrast, an increased risk of breast cancer was detected for the 315+C haplotype (OR = 11.66, 95%CI = 1.44-252.23). We conclude that mitochondrial variants can affect breast cancer risk. More extensive studies, involving different types of cancer and patients with different genetic makeup, will be required to improve our understanding of the effects of germline mtDNA polymorphisms on carcinogenesis.

Data for 15 autosomal STR markers (Powerplex 16 System) from two Tunisian populations: Kesra (Berber) and Zriba (Arab).

Allele frequencies, together with some parameters of forensic interest, for 15 STRs included in the Powerplex 16 System (CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, Penta D, Penta E, TH01, TPO and VWA) were estimated from two samples of unrelated individuals from Tunisia, of different ethnicity: Kesra (Berber) and Zriba (Arab). No deviations from Hardy-Weinberg equilibrium were observed after Bonferroni's correction for the number of loci analysed. Comparative analyses between our population data and other North African databases showed that significant differences were concentrated on loci with lowest values of diversity (mainly CSF1PO and D13S317), irrespective of ethnicity and geographic location.