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

ABSTRACT 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, Sep 27, 2015
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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.
    Human immunology 04/2012; 73(7):720-5. DOI:10.1016/j.humimm.2012.04.010 · 2.14 Impact Factor
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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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    ABSTRACT: Two different sets of noncoding markers (microsatellites and Alu elements) from the human chromosome six were analysed in 106 individuals from Valencia (Spain), with the aim of exploring the effect of evolutionary forces on the genetic variability of the major histocompatibility complex (MHC) and assessing the potential usefulness of these genetic loci in phylogenetic studies. Linkage disequilibrium (LD) analyses revealed statistically significant associations among markers located in the MHC class I region, and also between the microsatellite D6S2792 and several genetic loci from MHC class I, II and III regions. Results of the Ewens-Watterson test indicated that only D6S2792 showed significant departure from selective neutrality. Despite the paucity of haplotype data in the literature, results of the phylogenetic analyses at world scale (Alu elements) showed that the genetic relationships of Valencia were mainly determined by the ethnic ancestry of the populations considered, whereas at European scale (microsatellites) population affinities were strongly influenced by geography. Our findings suggest that noncoding markers from the MHC such as Alu and microsatellite loci might have a potential value as lineage (ancestry) markers in investigations into evolutionary, medical and forensic perspectives.
    International Journal of Immunogenetics 09/2011; 38(6):483-91. DOI:10.1111/j.1744-313X.2011.01037.x · 1.25 Impact Factor
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    ABSTRACT: The islands of the West Mediterranean have played a central role in numerous archaeological, historical and anthropological studies due to their active participation in the history of main Mediterranean civilisations. However, genetic data failed to fit in both their degree of internal differentiation and relationships. A set of 18 Alu markers and three short tandem repeats (STRs) closely linked to the CD4, F13B and DM Alu have been analysed in seven samples from Majorca, Corsica, Sardinia and Sicily to explore some of these issues. Our samples show a high genetic heterogeneity inside and among islands for the Alu data. Global differentiation among islands (F(ST) 2.2%) is slightly higher than that described for Europeans and North Africans. Both the estimated divergence times among samples and the high population heterogeneity revealed by Alu data are compatible with population differences since the first islands' settlement in the Paleolithic period. However, the high within-population diversities and the remarkable homogeneity observed in both STR and Alu/STR haplotype variation indicated that, at least since Neolithic times, gene flow has been acting in west Mediterranean. Genetic drift in west-coast Sardinia and gene flow in west Sicily have contributed to their general differentiation, whereas Corsica, Majorca and east Sicily seem to reflect more recent historical relationships from continental south Europe.
    Journal of Human Genetics 02/2007; 52(12):999-1010. DOI:10.1007/s10038-007-0206-6 · 2.46 Impact Factor
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