CYP2C9 polymorphism in five autochthonous population of the same geographic area (Spanish Pyrenees).

Objective: To evaluate the frequency of CYP2C9 polymorphisms in a cohort of Caucasians (Spanish Pyrenees), previously classified in autochthonous populations.

Methods: Blood samples from 154 anonymous volunteer donors were collected. All the individuals were autochthonous to their respective populations (four grandparents born in the region): 23 from Valle de Arán (Lérida), 29 from Alto Urgel (Lérida), 32 from La Cerdaña (Gerona), 30 from Jacetania (Huesca) and 40 from Cinco Villas (Navarra). The analyses for allelic mutation, CYP2C9*2 and CYP2C9*3, were identified with Taqman Allelic Discrimination kits.

Results: No statistical differences were found when allelic frequencies in the five autochthonous populations were compared. Frequency distribution of genotypic classes (wt/wt, wt/mut and mut/mut) in Alto Urgel was different from that in La Cerdaña, Cinco Villas and Jacetania samples. Comparison of Pyrenean and other European populations through exact test revealed significant differences in the distribution of genotypic classes: Alto Urgel, Barcelona, and Croatia yielded the highest significant differences. According to the exact test these populations were pooled in four groups. This classification produced a statistically significant percentage of variation explained by differences among groups (1.94%, P= 0.036), but not by differences among populations within groups (P=0.914), although most of the percentage of variance is explained by differences within populations (97.46%, P<0.001).

Conclusion: This study increases the evidence of intra-population genotypic variability and highlights the significant genotypic heterogeneity when different autochthonous populations are considered, despite no clear differences in allelic frequencies do exist.