Mass screening for ion channel gene abnormality in the patients with long QT syndrome diagnosed by Screening Program for Heart Disease

许多学生使用心脏病筛查计划被诊断为QT间期延长。如果确定他们的离子通道基因异常(S)，将有助于他们的药物治疗。裂解酶片段长度多态性分析(CFLP)分析具有稳定的重复性，并且可以分析比通常用于基因分析的单链构象多态性(SSCP)更长的DNA片段。我们研究了使用CFLP分析进行离子通道基因大规模筛选的可能性。首先，对一个长QT综合征家系进行CFLP分析。CFLP分析表明，在KVLQT1基因S4和S5之间的部分，正常基因和患者基因的差异在于患者条带的密度增加，其大小约为50个碱基。用直接测序的方法发现了一个杂合性突变(CCGTGG-&GT；CCATGG)，并用NCO I酶的限制性内切酶片段长度多态性分析证实了该突变。CFLP分析证实，835碱基聚合酶链式反应产物中存在一个点杂合性突变。本研究对另外两个QT间期延长综合征家系和3例散发性QT间期延长患者进行了CFLP分析，结果表明，CFLP分析是一种在大基因中筛查未知突变的有效方法。但未发现异常，需对其他患者作进一步检查。利用CFLP和直接测序对全离子通道基因进行联合分析已经开始。

Many students are diagnosed as having long QT interval using Screening Program for Heart Disease. If their ion channel gene abnormality(s) are determined, it will be helpful on their medication. Cleavase fragment length polymorphism analysis (CFLP) analysis expresses stable reproducibility and has the possibility of analyzing much longer DNA fragments than those possible by single-strand conformation polymorphism (SSCP), which is usually applied in gene analysis. We examined the possibility of ion channel gene mass screening using the CFLP analysis.At first, CFLP analysis was performed in the study of a family with long QT syndrome. CFLP analysis showed a difference between normal genes and the patients' genes in the part be tween S4 and S5 of the KVLQT1 gene in terms of an increased density of a patient's band whose size was around 50 base. A heterozygous mutation (CCGTGG->CCATGG) was indicated using direct sequencing, and the mutation was confirmed by restriction fragment length polymorphism using the enzyme of Nco I. It was confirmed that one point heterozygous mutation in 835 base pair polymerase chain reaction product was detectable using CFLP analysis. It is suggested that CFLP analysis is a useful method for the screening of unknown mutation(s) in large genes.CFLP analysis was applied in other two families with long QT syndrome or three patients with sporadic long QT interval. However, no abnormalities have been found.Further examinations on other patients are necessary. Combination analysis using CFLP and direct sequencing for whole ion channel gene is starting.