Allelic frequencies of single nucleotide polymorphisms (SNPs) in the N-acetyltransferase 2 (NAT2) gene of Filipinos

ABSTRACT

OBJECTIVES:The present study aims to determine the frequency of occurrence of NAT2*4, NAT2*5A, NAT2*6B, NAT2*7A and NAT2*14A alleles by PCR-RFLP among Filipino volunteers. These alleles correspond to substitutions in the following sites C341T, G590A, G857A and G191A, respectively, of the NAT2 gene. The presence of specific SNP combination was also used to deduce acetylation status and estimate genotype frequency and describe them in comparison with other populations based on literature. METHODS: Genomic DNA from peripheral blood lymphocytes from 129 healthy Filipino volunteers was used to amplify the NAT2 gene segment. The RFLP analysis was done by restricting the expected PCR product with Kpn1, Taq1, BamH1 and Msp1/Al1, respectively, to detect the 4 alleles NAT2*4, NAT2*5A, NAT2*6B, NAT2*7A and NAT2*14A. RESULTS:The calculated allelic frequencies in Hardy-Weinberg equilibrium of NAT2*5A (C481T), NAT2*6B (G590A), NAT2*7A (G857A) and NAT2*14A (G191A) were 0.058, 0.097, 0.182 and 0.046, respectively. NAT2*4 had an allele frequency of 0.617. Nine genotypes were determined NAT2*4/*4, NAT2*4/*5A, NAT2*4/*6B, NAT2*4/*7A, NAT2*4/*14A, NAT2*5A/*7A, NAT2*6B/*7A, NAT2*6B/*14A and NAT2*7A/*14A. From these genotypes, acetylator phenotypes were deduced. A trimodal pattern of distribution was established rapid, intermediate and slow acetylators with the following percentages, 47.3%, 41.1 % and 11.6%. Among the slow acetylator SNPs determined, NAT2*7A was found as the most frequent allele and NAT2*14A was found as the least frequent allele. CONCLUSION:The study showed the mutation profile and observed genotypic similarities and differences of Filipinos with other Asian populations and Americans and other Caucasians based on literature. The results also suggest a trimodal pattern of distribution of acetylators and lesser number of slow acetylators among Filipino populations, a characteristic similar to other Asian populations but significantly different from Americans and other Caucasians. The occurrence of NAT2*7A and NAT2*14A can be further sequenced to verify the observed genotype.