North African Berber and Arab Influences in the Western Mediterranean Revealed by Y-Chromosome DNA Haplotypes

Human Biology, Jun 2006 by G�rard, Nathalie, Berriche, Sala, Aouiz�rate, Annie, Di�terlen, Florent, Lucotte, G�rard

Materials and Methods

DNA Samples. This study concerns 2,196 unrelated male DNA samples (Table 1). We collected 904 new unrelated males subjects, from three different countries (Portugal, France, and Italy): 79 from North Portugal and 59 from South Portugal; 243 from the Marseilles region of France; 192 from Genoa, 64 from Rome, and 128 from Naples in continental Italy; 39 from Sicily; and 100 from Sardinia. All these new samples correspond to adult males, whose origin is based on the local birthplace of their fathers and (at least) grandfathers. We have obtained informed consent from each of the French subjects studied.

We add for comparison the following subjects, already tested as bearing haplotype V in previous studies: 11 subjects from Mauritania, 51 Berbers from Morocco, 59 Arabs from Rabat, 80 subjects from Algeria, 39 subjects from Tunisia, and 17 subjects from Libya (Lucotte et al. 2000); 29 Spaniards from Sevilla (Lucotte et al. 2001); 4 Spaniards from Barcelona and 9 French Catalans from Perpignan (Lucotte and Loirat 1999); 11 French Basques, 1 subject from Montpellier, and 7 subjects from Grasse in France and 6 subjects from Milan in Italy (Lucotte and Hazout 1996); and 44 subjects from Corsica (Lucotte et al. 2002).

Figure 1 indicates the representative geographic points in the western Mediterranean area for each of the 22 populations studied.

Genetic Analysis. Blood samples were collected by venipuncture using EDTA as an anticoagulant. Genomic DNA was extracted as described by Gautreau et al. (1983), using proteinase K and phenol-chloroform extractions.

Y-chromosome haplotypes were obtained using Southern blot analysis by hybridizing TaqI-restricted DNA successively with the p49f,a-specific probes, oligolabeled by random priming, according to the method described by Lucotte et al. (1994). Subdivision of haplotype V detected by Southern blot analysis into subhaplotypes Va and Vb was realized by polymerase chain reaction (PCR), using the assay published by Gon�alves and Lavinha (1994); the presence of the "low" XY275 allele (275G) defines subhaplotype Vb, and the other allele defines subhaplotype Va.

To compare subhaplotypes Va and Vb with the E3b1 and E3b2 subhaplo-groups [according to the Y Chromosome Consortium (2002) nomenclature], we further analyzed our Berber and Arabic DNA samples from Morocco for biallelic markers M78 and M81 using PCR (Underbill et al. 2000).

Realization of the Isofrequency Haplotype Maps. The maps of subhaplotype Vb and Va isofrequencies have been drawn with the Spatial Analyst program (Arcview software) using the Kringing procedure. We have used the inverse distance weighting method (with a power of 2), which is well adapted to scarce data in coastal areas and on islands in the western Mediterranean area. Five neighbors are calculated for each quadrant.

Results

Table 1 summarizes the frequencies we obtained for haplotype V and sub-haplotypes Vb and Va in the 22 study populations. For the 2,196 males typed, 491 (22.3%) bear haplotype V. The frequency of haplotype V is 35.5% in Portugal, with a more elevated proportion in the south (49.2%) than in the north (25.3%). The frequency of haplotype V in the Marseilles region (11.1%) has a value similar to the mean value in continental France (9%). In Italy the highest frequency is attained in Sicily (28.2%), followed by Naples at 17.2%. As previously shown (Lucotte et al. 2000), haplotype V is found at the highest frequency (68.9%) in Berbers from Marrakech in Morocco; an apparently increasing east-west cline in haplotype V frequencies is shown in North Africa from Libya (44.7%) to Rabat (57.7%), with intermediate values for Tunisia (53.4%) and Algeria (56.7%). In Spain haplotype V is much more frequent (40.9%) in the south of the country [in Andalusia (Sevilla)] than in the north (12.9%) [in Catalonia (Barcelona)].