Molecular diagnosis of thiopurine S-methyltransferase deficiency: Genetic basis for azathioprine and mercaptopurine intolerance
Molecular diagnosis of thiopurine S-methyltransferase deficiency: Genetic basis for azathioprine and mercaptopurine intolerance
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DOI：
10.7326/0003-4819-126-8-199704150-00003
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发表时间：
1997-04-15
影响因子：
39.2
通讯作者：
Evans, WE
中科院分区：
文献类型：
--
作者：
Yates, CR;Krynetski, EY;Evans, WE
背景：硫嘌呤5-甲基转移酶（TPMT）催化巯基嘌呤、硫嘌呤和硫鸟嘌呤的s -甲基化（即失活），并表现出遗传多态性。由于杂合性，大约10%的患者TPMT具有中等活性，大约每300人中就有1人遗传TPMT缺乏常染色体隐性性状。如果他们接受标准剂量的硫嘌呤药物治疗（例如，每天75 mg/m(2)体表面积），tpmt缺乏的患者会在造血组织中积累过多的硫鸟嘌呤核苷酸，从而导致严重的甚至可能致命的骨髓抑制。目的：阐明TPMT缺乏症和杂合性的遗传基础，建立诊断TPMT缺乏症和杂合性的分子方法。设计：诊断试验评估。单位：研究医院。患者：测定282名无亲缘关系的白人的TPMT表型，测定所有具有中等TPMT活性（杂合子）的人的TPMT基因型，以及随机选择同等数量的具有高活性的人。此外，对6例tpmt缺乏患者进行了基因型测定。检测方法：采用聚合酶链反应（PCR）检测TPMT*Z基因中G238C的转位，TPMT*3基因中G460A和A719G的转位；放射化学法测定TPMT活性。在基因组DNA中发现了TPMT突变，并确定了TPMT基因型和表型的一致性。结果：21例患者为杂合子表型（占样本的7.4% [95% Cl， 4.7%至11.2%]）。TPMT*3A是最常见的突变等位基因（杂合子中21个突变等位基因中有18个；85%）；TPMT*2和TPMT*3C较为少见（各约占5%）。所有6例TPMT缺乏症患者均有2个突变等位基因，中度TPMT活性的21例患者中有20例（95% [CI， 76%至99.9%]）有1个突变等位基因，高活性的21例患者中有21例（100% [CI， 83%至100%]）没有已知的TPMT突变。PCR检测基因组DNA中TPMT突变与互补DNA测序检测的基因型完全吻合。结论：人类TPMT基因座的主要失活突变已被确定，并可通过基于pcr的方法可靠地检测到，基因型和表型之间具有良好的一致性。检测TPMT突变为前瞻性识别TPMT缺陷和杂合患者提供了一种分子诊断方法。
Background: Thiopurine 5-methyltransferase (TPMT) catalyzes the S-methylation (that is, inactivation) of mercaptopurine, azathioprine, and thioguanine and exhibits genetic polymorphism. About 10% of patients have intermediate TPMT activity because of heterozygosity, and about 1 in 300 inherit TPMT deficiency as an autosomal recessive trait. if they receive standard doses of thiopurine medications (for example, 75 mg/m(2) body surface area per day), TPMT-deficient patients accumulate excessive thioguanine nucleotides in hematopoietic tissues, which leads to severe and possibly fatal myelosuppression.Objective: To elucidate the genetic basis and develop molecular methods for the diagnosis of TPMT deficiency and heterozygosity.Design: Diagnostic test evaluation.Setting: Research hospital.Patients: The TPMT phenotype was determined in 282 unrelated white persons, and TPMT genotype was determined in all persons who had intermediate TPMT activity (heterozygotes) and a randomly selected, equal number of persons who had high activity. In addition, genotype was determined in 6 TPMT-deficient patients.Measurements: Polymerase chain reaction (PCR) assays were developed to detect the G238C transversion in TPMT*Z and the G460A and A719G transitions in TPMT*3 alleles; Radiochemical assay was used to measure TPMT activity. Mutations of TPMT were identified in genomic DNA, and the concordance of TPMT genotype and phenotype was determined.Results: 21 patients who had a heterozygous phenotype were identified (7.4% of sample [95% Cl, 4.7% to 11.2%]). TPMT*3A was the most prevalent mutant allele (18 of 21 mutant alleles in heterozygotes; 85%); TPMT*2 and TPMT*3C were more rare(about: 5% each). All 6 patients who had TPMT deficiency had two mutant alleles, 20 of 21 patients (95% [CI, 76% to 99.9%]) who had intermediate TPMT activity had one mutant allele, and 21 of 21 patients (100% [CI, 83% to 100%]) who had high activity had no known TPMT mutation. Detection of TPMT mutations in genomic DNA by PCR coincided perfectly with genotypes detected by complementary DNA sequencing.Conclusions: The major inactivating mutations at the human TPMT locus have been identified and can be reliably detected by PCR-based methods, which show an excellent concordance between genotype and phenotype. The detection of TPMT mutations provides a molecular diagnostic method for prospectively identifying TPMT-deficient and heterozygous patients.