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目的:研究长QT综合征患者基因突变、致病机制及其与临床表型之间的关系。方法:分析长QT综合征患者的临床表现、心电图特点,应用聚合酶链式反应(PCR)扩增长QT综合征的常见突变基因KCNQ1,HERG,SCN5A的全部外显子及外显子与内含子连接部位,DNA直接测序检测基因突变位点。应用实时定量PCR方法测定一个家系的成员基因表达量,以探讨其可能的致病机制。结果:在5个长QT综合征家系中,发现2个HERG基因突变位点及1个SCN5A基因突变位点,分别为HERG基因C1848A、G1120T和SCN5A基因G638T。其中HERG基因C1848A突变引起616位酪氨酸转变为终止密码子(Y616X),G1120T突变引起374位缬氨酸转变为苯丙氨酸(V374F);SCN5A基因G638T突变引起213位甘氨酸转变为缬氨酸(G213V)。HERG基因Y616X突变患者家族成员外周血mRNA表达量分析,发现其HERG基因mRNA表达量明显低于无突变者。结论:发现3个长QT综合征相关的基因新突变位点,两个突变位于HERG基因,另一个位于SCN5A基因。其中HERG基因无义突变Y616X引起mRNA表达量减少,可能受无义突变介导的RNA降解(Nonsense Mediated Decay,NMD)机制有关,从而引起较轻微的临床症状。
Objective: To study the relationship between gene mutation, pathogenesis and clinical phenotype in patients with long QT syndrome. Methods: The clinical features and electrocardiogram features of patients with long QT syndrome were analyzed. All the exons and exons of KCNQ1, HERG and SCN5A common mutations in long QT syndrome were amplified by polymerase chain reaction (PCR) Conjugate junction, DNA direct sequencing detection of gene mutation sites. Real-time quantitative PCR method was used to determine the gene expression of a member of a family to explore its possible pathogenesis. RESULTS: In five long QT syndrome pedigrees, two HERG gene mutation sites and one SCN5A gene mutation site were found, namely HERG gene C1848A, G1120T and SCN5A gene G638T respectively. In which the C1848A mutation of the HERG gene resulted in the conversion of the 616th tyrosine to the stop codon (Y616X), the G1120T mutation resulted in the conversion of 374th valine to phenylalanine (V374F), and the G638T mutation of the SCN5A gene resulted in the conversion of 213th glycine to valine Acid (G213V). HERG gene Y616X mutations in patients with family members of peripheral blood mRNA expression analysis found HERG gene mRNA expression was significantly lower than those without mutation. CONCLUSION: Three new QT syndrome-related gene mutations were found. Two mutations were found in the HERG gene and one in the SCN5A gene. Among them, HER6 gene nonsense mutation Y616X causes a decrease in mRNA expression, which may be related to the nonsense mutation-mediated mechanism of Nonsense Mediated Decay (NMD), resulting in less minor clinical symptoms.