Polymorphic Alu insertions and the genetic structure of Iberian Basques

Departamento de Genética, Antropología Física y Fisiología Animal, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Bilbao, Spain.
Journal of Human Genetics (Impact Factor: 2.46). 02/2007; 52(4):317-27. DOI: 10.1007/s10038-007-0114-9
Source: PubMed


Eight Alu sequences (ACE, TPA25, PV92, APO, FXIIIB, D1, A25 and B65) were analyzed in two samples from Navarre and Guipúzcoa provinces (Basque Country, Spain). Alu data for other European, Caucasus and North African populations were compiled from the literature for comparison purposes to assess the genetic relationships of the Basques in a broader geographic context. Results of both MDS plot and AMOVA revealed spatial heterogeneity among these three population clusters clearly defined by geography. On the contrary, no substantial genetic heterogeneity was found between the Basque samples, or between Basques and other Europeans (excluding Caucasus populations). Moreover, the genetic information obtained from Alu data conflicts with hypotheses linking the origin of Basques with populations from North Africa (Berbers) or from the Caucasus region (Georgia). In order to explain the reduced genetic heterogeneity detected by Alu insertions among Basque subpopulations, values of the Wright's F(ST )statistic were estimated for both Alu markers and a set of short tandem repeats (STRs) in terms of two geographical scales: (1) the Basque Country, (2) Europe (including Basques). In the Basque area, estimates of Wahlund's effect for both genetic markers showed no statistical difference between Basque subpopulations. However, when this analysis was performed on a European scale, F(ST) values were significantly higher for Alu insertions than for STR alleles. From these results, we suggest that the spatial heterogeneity of the Basque gene pool identified in previous polymorphism studies is relatively recent and probably caused by a differential process of genetic admixture with non-Basque neighboring populations modulated by the effect of a linguistic barrier to random mating.

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Available from: Ana Maria Pérez-Miranda
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    • "Both these zones were selected mainly because North Navarre and Guipuzcoa are the two Basque regions possessing the highest density of Basque speakers (Euskaldunes) of any Iberian or French Basque territory, and therefore the Basque language (Euskera) still shows great vitality there [13]. More specific details concerning geography, demography and linguistic characteristics of these two Basque regions can be consulted in previous works [13] [14] [15] [16]. "
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    ABSTRACT: Polymorphic Alu insertions from the MHC class I region were analyzed in 215 autochthonous Basques from Guipuzcoa and Navarre provinces, with the aim of contributing new MHC Alu data in European ancestry populations. We also seek to assess both the genetic position of native Basques among worldwide samples and the efficiency of the MHC Alu elements as ancestry informative markers (AIMs). According to the MDS and AMOVA results, worldwide populations included in the comparative analyses were grouped in three major clusters defined by genetic ancestry (Africans, Asians and Europeans). The δ values (differences in weighted allele frequencies) among ancestry groups indicated that Alu elements within the alpha-block (AluHF, AluHJ and AluHG) showed an adequate resolving power to discriminate appropriately between some of the major ancestry groups. Alpha block Alu were also revealing of the exceptionality of Basques, as they allowed for the detection of genetic heterogeneity even between Basques and the other Iberian collection considered in the analysis (Valencia). Thus, analysis of the Alu loci within the alpha-block may represent a reliable, informative and cost-effective method to explore the ancestry, geographic origins and demographic history of human populations, which can be very helpful for studies into epidemiological, forensic or evolutionary perspectives.
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    • "A recent study on the polymorphism of microsatellites from the MHC showed that the genetic information obtained from microsatellites was very similar to that obtained from HLA genes (García-Obregó n et al., 2010), so that analysis of the genetic variability of MHC microsatellites could be an appropriate strategy for complementing HLA data in studies on the factors modelling the MHC polymorphism. Regarding Alu markers, numerous preceding investigations have demonstrated the usefulness of specific Alu repeats as ancestry informative markers, AIMs (Ray et al., 2005; García-Obregó n et al., 2007; Terreros et al., 2009; Gó mez-Pérez et al., 2010). Human genetic variation tends to be geographically structured, in accordance with historical patterns of gene flow and genetic drift. "
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