Mediterranean population structure using X-chromosome Alu insertions

Here's a new paper from a group of French, Greek, Spanish and Tunisian scientists (see abstract below).

From the discussion:

"In fact, the Tunisian genetic distances to European samples are smaller than those to North African groups. "
"This could be explained by the history of the Tunisian population, reflecting the influence of the ancient Phoenician settlers of Carthage followed, among others, by Roman, Byzantine, Arab and French occupations, according to historical records. Notwithstanding, other explanations cannot be discarded, such as the relative heterogeneity within current Tunisian populations, and/or the limited sub-Saharan genetic influence in this region as compared with other North African areas, without excluding the possibility of the genetic drift, whose effect might be particularly amplified on the X chromosome."

on the Basque and Crete population:

"An interesting aspect comes from the evidenced relationships between the Basque Country and Crete Island. These two populations have distinct historical, anthropological and cultural backgrounds, and yet no significant differences were found between them when a locus-by-locus 2 comparison was carried out. As for the remaining analyzed populations, Siwa Oasis seems to be the most differentiated (see Table 2 and Figure 1). The differentiation shown by Siwa Oasis, and also by High Atlas, could be related to higher foreign genetic contributions, from West Sahara into High Atlas and Nile groups into the Siwa Oasis. Esteban et al described a similar pattern of GGC allele frequencies of the androgen receptor (located in chromosome X) for the Ivory Coast and Siwa Oasis samples, giving evidence of sub-Saharan genetic influence in this Berber group."

The X chromosome Alu insertions as a tool for human population genetics: data from European and African human groups

Georgios Athanasiadis, Esther Esteban, Marc Via, Jean-Michel Dugoujon, Nicholas Moschonas, Hassen Chaabani and Pedro Moral

European Journal of Human Genetics (2007) 15, 578–583.

Abstract: Alu elements are the most abundant mobile elements in the human genome (1 100 000 copies). Polymorphic Alu elements have been proved to be useful in studies of human origins and relationships owing to two important advantages: identity by descent and absence of the Alu element known to be the ancestral state. Alu variation in the X chromosome has been described previously in human populations but, as far as we know, these elements have not been used in population relationship studies. Here, we describe the allele frequencies of 13 'young' Alu elements of the X chromosome (Ya5DP62, Ya5DP57, Yb8DP49, Ya5a2DP1, Yb8DP2, Ya5DP3, Ya5NBC37, Yd3JX437, Ya5DP77, Ya5NBC491, Yb8NBC578, Ya5DP4 and Ya5DP13) in six human populations from sub-Saharan Africa (the Ivory Coast), North Africa (Moroccan High Atlas, Siwa oasis in Egypt, Tunisia), Greece (Crete Island) and Spain (Basque Country). Eight out of 13 Alu elements have shown remarkably high gene diversity values in all groups (average heterozygosities: 0.342 in the Ivory Coast, 0.250 in North Africa, 0.209 in Europe). Genetic relationships agree with a geographical pattern of differentiation among populations, with some peculiar features observed in North Africans. Crete Island and the Basque Country show the lowest genetic distance (0.0163) meanwhile Tunisia, in spite of its geographical location, lies far from the other two North African samples. The results of our work demonstrate that X chromosome Alu elements comprise a reliable set of genetic markers useful to describe human population relationships for fine-scale geographical studies.