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  • Original Article
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CYP2A7 polymorphic alleles confound the genotyping of CYP2A6*4A allele

The Pharmacogenomics Journal volume 6, pages 401–412 (2006)Cite this article

Abstract

Human cytochrome P450 (CYP) 2A6 metabolizes nicotine to cotinine. Genetic polymorphisms of CYP2A6 contribute to the interindividual variability of nicotine metabolism. We encountered some subjects possessing two copies of the CYP2A6 gene, although they were genotyped as heterozygotes of the CYP2A6*4A allele (entire CYP2A6 gene deleted allele). From the subjects, we found CYP2A7 polymorphic alleles (CYP2A7*1B, CYP2A7*1C, and CYP2A7*1D) in which the sequences in the 3′-flanking region were converted to the corresponding CYP2A6 sequences, being confused with the CYP2A6*4A. These allele frequencies in European-Americans (n=187) were 1.3, 2.1, 0.3%, respectively, but these were very rare in African-Americans (n=176), Japanese (n=184), and Koreans (n=209). By an improved genotyping method, the allele frequency of CYP2A6*4A of 3.7% in European-Americans was corrected to 0%. The comprehensible and reliable genotyping method developed in this study would be useful to evaluate associations between the genotype and phenotype.

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Acknowledgements

This study was supported in part by a grant from the Japan Health Sciences Foundation with the Research on Health Science Focusing on Drug Innovation, by an SRF Grant for Biomedical Research in Japan and by Philip Morris Incorporated. The enthusiasm and research support of Tracy Jones, RN, Arnita Pitts, RN, Phyllis Klein, RN, and Ladonna Gaines, Washington University Center for Clinical Studies, and Margaret Ameyaw, MD are greatly appreciated. We acknowledge Mr Brent Bell for reviewing the manuscript.

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Authors and Affiliations

  1. Department of Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa, Japan

    T Fukami, M Nakajima, H Sakai & T Yokoi

  2. Department of Medicine, Washington University School of Medicine, St Louis, MO, USA

    H L McLeod

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  1. T Fukami
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  2. M Nakajima
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Correspondence to M Nakajima.

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Fukami, T., Nakajima, M., Sakai, H. et al. CYP2A7 polymorphic alleles confound the genotyping of CYP2A6*4A allele. Pharmacogenomics J 6, 401–412 (2006). https://doi.org/10.1038/sj.tpj.6500390

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