Volume 15, Issue 3 pp. 246-253
Research Article
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Screening of thiopurine S-methyltransferase mutations by horizontal conformation-sensitive gel electrophoresis

Sandra Alves

Corresponding Author

Sandra Alves

IPATIMUP, Porto, Portugal

Faculdade de Ciências da Universidade do Porto, Porto, Portugal

IPATIMUP, Rua Dr. Roberto Frias s/n, 4200 Porto, PortugalSearch for more papers by this author
Maria João Prata

Maria João Prata

IPATIMUP, Porto, Portugal

Faculdade de Ciências da Universidade do Porto, Porto, Portugal

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Fátima Ferreira

Fátima Ferreira

Serviço de Hematologia Clínica, Hospital Geral S. João, Porto, Portugal

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António Amorim

António Amorim

IPATIMUP, Porto, Portugal

Faculdade de Ciências da Universidade do Porto, Porto, Portugal

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Abstract

The genetic polymorphism of thiopurine S-methyltransferase (TPMT) has had a highly significant clinical impact due to its association with individual variation in the toxicity and therapeutic efficiency of thiopurine drugs, which are pharmaceutical agents widely used in the treatment of several kinds of diseases. Until now, ten mutant alleles responsible for TPMT deficiency and several silent and intronic mutations have been described.

In this work we present an alternative molecular method for the detection of TPMT alleles. It is an adaptation for horizontal conditions of a conformation-sensitive gel electrophoresis technique. The method has proven to be very efficient as a rapid screening approach for the study of TPMT genetic variability.

The method was applied to analyse eight TPMT exons and the corresponding flanking intronic regions in a sample of unrelated healthy individuals from North Portugal. Here we report the allelic frequencies concerning TPMT-deficient alleles and several silent and intronic mutations, including two newly detected intronic polymorphisms: an A (–101) T substitution in intron 3 and a variation involving the number of T nucleotides in a DNA stretch in intron 5. Additionally, we also present data from a sample of 43 children undergoing therapy for acute lymphoblastic leukemia. In this clinical sample we have registered a statistically significant higher frequency for the TPMT*3C allele. This finding raises the question whether the TPMT genotype can contribute to any genetic predisposition for development of the malignancy. Hum Mutat 15:246–253, 2000. © 2000 Wiley-Liss, Inc.

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