Aim: A (CA)n repeat located in the 3' UTR region of exon 29 of the NOS1 gene (encoding for neuronal nitric oxide synthase) has been shown to affect the size of mRNA. NOS1 mRNA is highly diverse, contributing to changes in transcript generation, degradation, processing, or subcellular targeting. In the present work, we analyzed allele frequencies of this (CA)n repeat in nine populations of the Mediterranean area and Middle Europe. We aimed at testing the presence of a north-south positive gradient of frequencies of ≤17 allele repeats, compatible with the hypothesis of positive selection suggested in two of our previous works, related to the past prevalence of malaria infection in Europe.
Results: Results show significant negative correlations of latitude with frequencies of alleles S and genotypes S/S and S/L (p < 0.01).
Conclusions: In conclusion, the north-south gradient of S alleles found in the present work would confirm our previous observation about the NOS1 gene, reinforcing the hypothesis of a selective action of malaria infection. This hypothesis is strengthened by the role of nitric oxide in the immunity system.