Characterization of TPMT minisatellite locus in five ethnic groups of India.

A total of 206 random, healthy individuals belonging to five distinct ethnic groups (Ezhavas, Arayas, Nairs, Vishwakarmas and Muslims) were analyzed for 18 bp VNTR repeat polymorphism present in the 5'flanking region of theThiopurine Methyl Transferase gene (TPMT). In the present study, the population data of TPMT minisatellite was compared with the population data of other loci and the utility of minisatellite was evaluated in population studies. Human tandem repeat alleles of the TPMT minisatellite locus were characterized for the length polymorphism. The expected and observed heterozygosity did not show any significant difference. All five populations were in Hardy-Weinberg equilibrium. High Polymorphism Information Content (PIC) (> or =0.658) and Power of Discrimination (PD) (ranging from 0.775-0.860) value of this VNTR showed that this marker is informative. The combined Power of Discrimination of TPMT minisatellite along with other two loci studied earlier in our lab was > or = 0.9964. The Paternity Exclusion Power (PE) of TPMTVNTR ranged from 0.203 to 0.533 and the combined Power of Paternity Exclusion (with two other loci D8S315 and D2S1328) was > or = 0.8285. All these parameters (Heterozygosity, PD, PIC, PE) of TPMT minisatellite locus showed that this marker is informative and can be used for DNA typing and population studies besides being used in clinical investigation in checking thiopurine drug sensitivity of individuals.