Frequency of Alu insertions within the ACE and PR loci in Northwestern Mexicans

Presently, non-LTR retrotransposons are the most active mobile elements in the human genome. Among these, Alu elements are highly represented in the modern population. Worldwide, distribution of Alu polymorphisms (insertion/deletion; I/D) shows variability between different populations. Two Alu insertion loci, ACE and PR, are significant biomarkers that have served in several genotype-phenotype association studies. In Mexico, studies concerning the frequency of these biomarkers have been conducted mainly in subpopulations from central and southern regions. Here, we screened a population sample of the northwestern region to gain further knowledge regarding the prevalence of Alu polymorphisms within ACE and PR loci.

For ACE locus, the observed genotype frequencies were 26.5, 51.0 and 22.5% for II, ID, and DD, respectively; and allelic frequencies for I and D were 52 and 48%. Whereas respective genotype frequencies for PR locus were 2.7, 26.5 and 70.8%, and the corresponding allele frequencies were 16 and 84%. Furthermore, the insertion frequency within ACE locus was similar between central, western and northwestern subpopulations, and rather higher in southeastern subpopulation (p < 0.05). Although the occurrence of Alu polymorphisms within PR locus has not been widely examined, the insertion frequency was higher in northwestern subpopulation, as compared with western and southeastern subpopulations (p < 0.05). Based on the frequency of Alu insertions found in ACE and PR loci, subpopulations from the northwestern, western and central regions share a common genetic origin, but apparently not with the subpopulation from the southeastern region, in accordance with the notion that assumes the existence of a broad genomic diversity in the Mexican population. In addition, the high prevalence of Alu insertions reveals their potential application as biomarkers with prognostic value for the associated diseases; e.g., as part of the standard protocols for clinical diagnosis.