Allele frequency of inosine triphosphate pyrophosphatase (ITPA) and thiopurine-S-methyl transferase (TPMT) genes in the Tunisian population

Abstract

The aim of this study was to determine the frequencies of TPMT and ITPA polymorphisms in Crohn's disease patients of Tunisian origin and to compare them with allele frequencies previously reported in other populations of various ethnic origins. ITPA (c.94C>A and IVS2+21A>C) and TPMT (c.238G>C, c.460G>A and c.719A>G) mutations and genotypes were assessed in 208 Tunisian subjects (78 males/130 females) by polymerase chain reaction-restriction fragment length polymorphism and allele-specific-PCR methods. Genotyping of ITPA revealed frequencies of 6% and 7.9% for c.94C>A and IVS2+21A>C, respectively. Accordingly, deficient or diminished ITPA phenotype can be predicted to concern 2.4% of Tunisians. The observed frequencies of the c. 238G>C, c.460G>A and c.719A>G TPMT polymorphisms were 0, 0.24 and 1.44%, respectively. This study provides the first analysis of TPMT and ITPA mutant allele frequency in individuals of Tunisian origin. Unlike in Caucasians, TPMT*3C which harbours the c.719A>G polymorphism appears to be the most common mutant allele in Tunisians. In contrast, ITPA mutant allele frequency distribution appears to be similar to that observed in Caucasians.