Rapid and reliable genotyping procedure for detection of alleles with mutations, deletion, or/and duplication of the CYP2D6 gene.

BACKGROUND

Polymorphisms of cytochrome P450 2D6 (CYP2D6) have a significant effect on the pharmacokinetics of most tricyclic antidepressants. More than 150 alleles lead to four distinct phenotypes of drug metabolism. The phenotypes are described as ultrarapid, extensive, intermediate, and poor metabolizers. Therapeutic plasma levels of CYP2D6 substrates may be difficult to achieve. Here we describe a rapid and reliable procedure for CYP2D6*4, *3, *6, and *9 genotyping.

DESIGN AND METHODS

Serum concentrations of venlafaxine and its pharmacologically active metabolite, O-desmethylvenlafaxine, were measured in patients treated with the antidepressant venlafaxine, a substrate of CYP2D6. The ODV/V ratio was used as an indicator of the CYP2D6 phenotype, with a higher ratio reflecting more rapid metabolism. Real-time PCR with fluorometric melting point analysis of the PCR products (LightCycler) is used to identify SNPs. Using quantitative PCR, gene deletion and gene duplication or multiplication are investigated by measurement of the fluorescence intensity quotient (q, N) of the CYP2D6 gene relative to that of the albumin gene as an internal standard.

RESULTS

Melting curves are verified using DNA samples of known genotypes and by sequencing the PCR products. The genotypes and phenotypes that were detected correspond to each other.

CONCLUSION

A PCR procedure for the detection of CYP2D6 SNPs, deletions, and duplications is described and is rapid and reliable.