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

许多学生被诊断为长QT间期使用筛选程序的心脏疾病。如果确定他们的离子通道基因异常，这将有助于他们的药物治疗。裂解酶片段长度多态性分析（CFLP）具有稳定的再现性，可以分析比单链构象多态性（SSCP）更长的DNA片段，后者通常用于基因分析。我们检验了使用CFLP分析进行离子通道基因质量筛选的可能性。首先，对一个长QT综合征家庭进行了CFLP分析。CFLP分析显示，正常基因与患者基因在KVLQT1基因S4和S5之间的部分存在差异，患者带的密度增加，其大小约为50个碱基。采用直接测序法鉴定出一个杂合突变（CCGTGG->CCATGG），并利用Nco i酶进行限制性片段长度多态性分析，证实该突变在835碱基对聚合酶链反应产物中检测到1点杂合突变。提示CFLP分析是一种筛选大基因未知突变的有效方法。另外2例长QT综合征家族或3例散发性长QT间期患者应用CFLP分析。然而，没有发现异常。有必要对其他患者进行进一步检查。全离子通道基因的CFLP和直接测序联合分析已经开始。

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.