Genetic polymorphism of CYP2D6 in Chinese subjects in Malaysia

BACKGROUND: Although Malaysian Chinese share an origin with the mainland Chinese, their evolution has been influenced by intermarriages. With a gene such as CYP2D6, which is highly polymorphic, it is expected that the Malaysian Chinese would exhibit a polymorphism profile different from those of the Chinese populations in other geographical locations. OBJECTIVE: To study the genotype distribution of CYP2D6 among the Chinese people in Malaysia. METHOD: We obtained DNA from 236 Chinese individuals in Malaysia and used PCR-based methods to identify any common CYP2D6 alleles. RESULTS: A total of 236 subjects were enrolled and were successfully genotyped. Malaysian Chinese were relatively heterogeneous in terms of their CYP2D6 genotypes with nine genotypes recorded. CYP2D6*4, *5, *9, *10 and *17 were detected with the most common genotype being *1/*10. No subject had genotypes that predicted poor metabolic activity. However, 40% showed genotypes (e.g. CYP2D6*10/*10, *17, *4 and *9 and *9/*9) that predicted an intermediate metabolizer phenotype. Another subject carried the defective CYP2D6*17 allele and six carried the defective CYP2D6*9 allele. Both these alleles have not been reported in other earlier Chinese studies. CONCLUSION: This study revealed that, in terms of CYP2D6 polymorphism, Malaysian Chinese were a heterogeneous group of people. Although sharing some similarities with other Orientals, they also seemed to have some notable differences. The alleles CYP2D6*4, *5, *9, *10 and *17 were all detected. CYP2D6*3 was however absent.