Objective: CYP2C9 is a polymorphic gene with at least six known allelic variants (CYP2C9*1 to *6). CYP2C9*5 has been recently described in African-Americans. The lower activity of CYP2C9*5 encoded enzyme than *1 has been reported for the S-warfarin 7-hydroxylation in vitro. The aim of the present study was to develop an assay for the analysis of this variant and to determine the frequency of this polymorphism in different ethnic populations.
Materials and methods: A PCR-based endonuclease digestion method, using a mismatched forward primer that introduced a recognition site for AvaII in all the CYP2C9 genotypes except CYP2C9*5, is described. DNA samples from 150 Ethiopians, 183 Tanzanians, 200 Caucasians from Sweden and 150 Orientals from Korea were screened for this variant allele.
Results and conclusion: The CYP2C9*5 allele was analysed using a polymerase chain reaction-based endonuclease method, and it was found in three Tanzanians (allele frequency, 0.0082) but not in Ethiopians, Caucasians or Orientals.