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[Genetic polymorphism of the thiopurine S-methyltransferase of healthy Han Chinese].

BACKGROUND & OBJECTIVE
Several mutations in the thiopurine S-methyltransferase(TPMT) gene have been identified to correlate with a low activity or deficiency phenotype. The distribution of TPMT activity in Chinese and Caucasian populations is different, and the molecular basis has not yet to be determined. This study was designed to investigate the type and frequency of four kinds of mutant TPMT alleles of healthy Han Chinese.


METHODS
TPMT genotypes were determined in 225 healthy Han Chinese. Allele-specific PCR (ASPCR) and PCR-restriction fragment length polymorphism (RFLP) were used for analysis of G238C (TPMT*2), G460A and A719G (TPMT*3A,*3B,*3C).


RESULTS
TPMT*2, TPMT*3B, and TPMT*3A were not detected in 225 healthy Han Chinese, and only six TPMT*3C heterozygotes were identified. The average TPMT activity of those TPMT*3C heterozygotes was (9.62+/-3.58) U/ml RBC. The frequency of TPMT mutant alleles was 1.33%(6/450) in healthy Han Chinese.


CONCLUSION
The frequency of the known mutant TPMT alleles in Han Chinese population is low, and TPMT*3C appears to be the most prevalent among the known mutant TPMT allele in this population.