The Basques according to polymorphic Alu insertions

Abstract

Polymorphic Alu insertions provide a set of DNA markers of interest in human population genetics. Approximately 1000-2000 of these insertions have not reached fixation within the human genome. Each one of these polymorphic loci most probably resulted from a unique insertional event, and therefore all individuals possessing the insertion are related by descent not just state. In addition, the direction of mutational change is toward the gain of the Alu element at a particular locus. Therefore, the improved knowledge of both the ancestral state and the direction of mutational change greatly facilitates the analysis of population relationships. As a result, Alu insertion polymorphisms represent a significant tool for population genetic studies. In this study, polymorphic Alu insertions have been employed to ascertain phylogenetic relationships among Basque groups and worldwide populations. The Basques are considered to be a geographic isolate with a unique language and customs. They may be direct descendants of Cro-Magnon enclaves from the upper Paleolithic (38,000 to 10,000 years). The Basques are distributed among narrow valleys in northeastern Spain with little migration between them until recently. This characteristic may have had an effect on allelic frequency distributions. With the aim of studying this possible effect, we have analyzed six autosomal polymorphic Alu loci from four different sites within the Spanish Basque region in order to ascertain any genetic heterogeneity among the Basques. The results are consistent with a lack of homogeneity among these four autochthonous Basque groups.

Microsatellite data support subpopulation structuring among Basques

“…This assumption seems to be confirmed by the AMOVA data. Evidence of the genetic heterogeneity among the Basques has been previously observed in studies on the variability of the immunoglobulin (GM and KM) genes (Caldero´n et al 1998), on the genetic polymorphism of HLA-DQA1 loci in different Basque samples (Pe´rez-Miranda et al 2003), and on PAIs (Pancorbo et al 2001). These studies suggest that the more probable cause of the genetic diversity among the Basque groups may be the existence of different levels of admixture of ancient Basques with other non-Basque neighboring populations.…”

“…Yet, the causative agents of such marked isolation remain unclear. Some authors have suggested that the isolation of Basques is a consequence of their singular language (Cavalli-Sforza et al 1994;Caldero´n et al 1998;Pancorbo et al 2001). Indeed, linguistic differences can be effective barriers to gene flow (Barbujani and Sokal 1990;Barbujani 1997).…”

“…Recent studies designed to assess the geographic patterning of the Basques indicate that their genetic diversity is spatially structured (Aguirre et al 1991;Manzano et al 2002). This contention is starting to be confirmed as well by DNA molecular markers (Brown et al 2000;Pancorbo et al 2001;Iriondo et al 2003;Pe´rez-Miranda et al 2003). Some results point to Guipu´zcoa as being the Basque province with the most genetic distinctiveness whereas the highest levels of genetic affinity with non-Basque surrounding populations have been reported for the province of Alava (Caldero´n et al 1998;Pe´rez-Miranda et al 2003).…”

Human Alu Insertion Polymorphisms in North African Populations

“…Among these young Alu elements, approximately 25% have inserted so recently that they are polymorphic among different human population groups, families, or even individuals with respect to their presence or absence in the genome (Batzer and Deininger, 2002). Because Alu insertions are unique events that are identical bydescent, they have been useful in genetic mapping and population genetics studies (Batzer et al, 1994;Batzer and Deininger, 1991;Perna et al, 1992;Roy-Engel et al, 2001;Salem et al, 2003;Stoneking et al, 1997;Tishkoff et al, 2000) Alu markers have been used extensively for population structure and evolution, both at global (Bazter et al 1996;Romualdi et al 2002;Bamshad et al 2003) and regional levels (Majumder et al 1999;Comas et al 2000Comas et al , 2004de Pancorbo et al 2001;Nasidze et al 2001;Ennafaa et al 2006;Bahri et al 2008;Frigi et al 2010a). The objective of this study is to compare the genetic structure of some North African populations with respect to the other populations of North Africa, Western, Eastern and Central Europe, by using MDS and AMOVA methods.…”

Factor XI deficiency in French Basques is caused predominantly by an ancestral Cys38Arg mutation in the factor XI gene

“…43 The present study identified a new characteristic genetic feature: the Cys38Arg mutation in the factor XI gene among French Basques. However, since a recent study demonstrated significant differences in genetic markers among autochthonous Basque subgroups, 44 it remains to be established whether the Cys38Arg mutation is evenly distributed among all Basque subgroups.…”