Mixed origin of the current Tunisian population from the analysis of Alu and Alu/STR compound systems

Abstract

During successive historical periods, Tunisia has been a crossroads of multiple civilizations and their corresponding key population movements. The aim of this study was to provide genetic information relating to the mixed origin of the Tunisian population, and to analyze its genetic relationship with other North African and Mediterranean populations. A set of 16 Alu and 3 Alu/STR compound systems has been analyzed in 268 autochthonous Tunisians from the north-center and the south of the country. Our two sampled populations showed no significant differentiation from one another in any of the three Alu/STR compound systems, whereas the analysis of the 16 Alu markers revealed a significant genetic differentiation between them. A sub-Saharan component shown by the three Alu/STR combinations is more noticeable in our north-center sample than in that of the south. The presence of two Alu/STR combinations specific to North African ancestral populations also suggests that the ancient Berber component is relatively more substantial in the north and center regions than in the south. Our Tunisian samples cluster together with other Berber samples from Morocco and Algeria, underpinning the genetic similarity among North Africans regardless of their current linguistic status (Berber or Arabic).

Distinctive genetic signatures of <i>Alu</i>/STR compound systems revealed by analyses of Mediterranean and Middle East populations

“…From our analysis of the genetic variance value for each compound system, we noted that the values of genetic variance among groups and among populations within groups determined for the FXIIIB locus (F CT = 0.029, P < 0.001 and F SC = 0.008, P < 0.001) were higher than those determined for the CD4 locus (F CT = 0.014, P < 0.001 and F SC = 0.006, P < 0.001) The high number of different haplotypes found in our samples (13 for the CD4 locus and 10 for the FXIIIB locus, see Table 1) and previous studied samples (e.g. González-Pérez et al, 2007El Moncer et al, 2010) represents the source of the great ability of the two systems to discriminate microdifferentiation processes. In Table 2 we list the frequency distribution of four haplotypes selected because of their specificity to one of the three population groups for which we have available data.…”

“…In Table 2 we list the frequency distribution of four haplotypes selected because of their specificity to one of the three population groups for which we have available data. Two haplotypes have been found in higher frequencies in our two Middle Eastern samples, CD4 90(+) and FXIIIB 180(-), whereas the two other haplotypes cited in Table 2 were already described (González-Pérez et al, 2007El Moncer et al, 2010, Flores et al, 2000 as relatively more frequent in Berbers (CD4 110(-)) or only frequent in Sub-Saharan Africans (CD4 100(+)).…”

“…We have expanded previous studies conducted in Mediterranean populations (González-Pérez et al, 2007El Moncer et al, 2010) by describing a new North African sample from Libya. In addition, we present for the first time new data on Bahrain and southern Iran, providing a larger global view on the genetic differentiation of populations ranging from the Mediterranean region to the Middle East.…”

“…In order to compare the CD4 and FXIIIB Alu/STR haplotype frequencies, 20 Mediterranean samples previously tested for the same genetic markers are considered (González-Pérez et al, 2007El Moncer et al, 2010). The geographical location of the Mediterranean populations used in this study is indicated in Figure 2.…”

“…However, the combined use of haplotypic variation consisting of both a fast-evolving STR and a slow-evolving Alu marker (Alu/ STR compound system) has provided more anthropological details. The first Alu/STR compound system was determined at the CD4 locus on chromosome 12 and was used by Tishkoff et al (1996), then two others, FXIIIB Alu/STR on chromosome 1 and DM Alu/STR on chromosome 19, were determined and studied particularly in Mediterranean human populations (González-Pérez et al, 2010;El Moncer et al, 2010).…”