Frequency of certain single-nucleotide polymorphisms and duplication of CYP2D6 in the Jordanian population.

The CYP2D6 isozymes are responsible for metabolism of 7-10% of clinically available drugs. Genetic polymorphism in CYP2D6 may have an impact on drug efficacy and toxicity. The aim of this study was to determine the allelic frequency of CYP2D64, 10, and 17 and CYP2D62×N duplication allele in 192 healthy unrelated male and female Jordanian volunteers. Polymerase chain reaction (PCR)-restriction fragment length polymorphism-based methods were used to identify the CYP2D64, 10, and 17 genotypes; and allele-specific long PCR was used to determine the CYP2D62×N allelic frequency. The CYP2D610 allele was the most frequent mutant allele in Jordanians (14.8%) followed by CYP2D64 and 17 at 12.8%, and 8.3%, respectively. The duplication allele was found in 13.5% of the studied sample. The CYP2D64 G-A heterozygote genotype frequency was 20.3%, and the homozygous mutant genotype was 2.6%. In case of CYP2D610 C-T and CYP2D617 G-C heterozygote genotypes, the frequencies were 21.4% and 12.5%, respectively, while the homozygous mutant genotype frequencies of T-T and C-C were 4.2% and 2.1%, respectively. In conclusion, the allelic distributions of the CYP2D6 gene among Jordanians are different from other Mediterranean groups, especially the *10 and 17 single-nucleotide polymorphisms, and more importantly the CYP2D62×N duplication allele, which seems to follow a gradient reduction in prevalence from Ethiopia to Northern Europe.