Population relationships in the Mediterranean revealed by autosomal genetic data (Alu and Alu/STR compound systems)

Abstract

The variation of 18 Alu polymorphisms and 3 linked STRs was determined in 1,831 individuals from 15 Mediterranean populations to analyze the relationships between human groups in this geographical region and provide a complementary perspective to information from studies based on uniparental markers. Patterns of population diversity revealed by the two kinds of markers examined were different from one another, likely in relation to their different mutation rates. Therefore, while the Alu biallelic variation underlies general heterogeneity throughout the whole Mediterranean region, the combined use of Alu and STR points to a considerable genetic differentiation between the two Mediterranean shores, presumably strengthened by a considerable sub-Saharan African genetic contribution in North Africa (around 13% calculated from Alu markers). Gene flow analysis confirms the permeability of the Sahara to human passage along with the existence of trans-Mediterranean interchanges. Two specific Alu/STR combinations-CD4 110(-) and DM 107(-)-detected in all North African samples, the Iberian Peninsula, Greece, Turkey, and some Mediterranean islands suggest an ancient genetic background of current Mediterranean peoples.

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

“…To illustrate this, the CD4 100(+), a common Sub-Saharan African haplotype, has been found in the Libyan sample with a frequency of 0.0327. This genetic richness of the Libyan population, also stated in previous work (Ben Cherni et al, 2011;Fadhlaoui-Zid et al, 2011), could be due Present study Flores et al, 2000;González-Pérez et al, 2010 partly to the fact that Libya is located more in the south (in continuity with the south of Tunisia) nearer to central Sub-Saharan countries and at the same time it has a long Mediterranean coastline to the north. Regarding the genetic relationships among Middle East and North African samples, if we exclude the Libyan sample, we do not observe any particular genetic closeness among these groups.…”

“…This combination is absent in Sub-Saharan African and European samples except in some Mediterranean groups from Spain, Sardinia and Sicily. It was proposed in previous works (Flores et al, 2000;González-Pérez et al, 2010) to be representative of an ancient Berber background because it was observed throughout North Africa. However, its presence in Bahrain and southern Iran makes a new interpretation necessary: this haplotype could be a common haplotype of those human groups from the Middle East that colonized the southern shore of the Mediterranean in the Upper Paleolithic, if we take into account that its estimated age is around 36000 BP (95% CI: 3200-186000; González-Pérez et al, 2010).…”

“…It was proposed in previous works (Flores et al, 2000;González-Pérez et al, 2010) to be representative of an ancient Berber background because it was observed throughout North Africa. However, its presence in Bahrain and southern Iran makes a new interpretation necessary: this haplotype could be a common haplotype of those human groups from the Middle East that colonized the southern shore of the Mediterranean in the Upper Paleolithic, if we take into account that its estimated age is around 36000 BP (95% CI: 3200-186000; González-Pérez et al, 2010). However, we cannot exclude the possibility that population movements from the Middle East (particularly from Arabia) to the South Mediterranean, agreeing with the Neolithic spread or, in more recent times, with the substantial expansion of Arabs in the seventh century AD, could be also responsible for the presence of this haplotype.…”

“…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).…”

Polymorphism of the Microsatellite DXS8377 in a Population of Northern Thai Males

“…When considering a dendrogram constructed based on the allele frequencies, two clusters were clearly formed, in which five Asian populations (Japanese, Northern Han, Hui, Uygur, and Kazakh) were presented in one cluster, while two Europeans and one West Asian (Italian, Greek, and Saudi Arabian) were presented in another. Gonzalez-Perez et al [11] analyzed the population relationships in the Mediterranean populations by using the combination of genetic markers; 18 Alu insertion polymorphisms (polymorphisms based on the presence and absence of an Alu element at a specific location of chromosome) and 3 STR loci. The results showed that, when considering the Alu/STR haplotype frequencies, the differentiation between Northern and Southern Mediterraneans was significantly noticeable.…”