基因变异功能学研究在不典型长QT综合征诊断中的作用

目的探讨基因变异功能学研究在临床不典型长QT综合征（LQTS）诊断中的作用。方法先证者有晕厥事件,心电图无QTc延长,临床疑诊LQTS;基因检测显示KCNH2基因M756V变异;家系中变异携带者QT正常,无心脏事件。分别使用含有野生型（WT）和突变M756V HERG基因的pcDNA3.1重组质粒进行转染,设WT＋M756V共转染组。转染后进行膜片钳和免疫组化研究明确临床诊断。结果 HERG M756V组电流较WT组明显减低,提示M756V变异为具有病理意义的LQTS突变;HERG M756V与WT共转染并无明显负显性机制。免疫组化研究表明HERG M756V蛋白存在转运障碍。结论体外功能学研究证实KCNH2基因M756V变异为LQTS突变,为临床疑诊患者提供确诊依据。

Functional study of a gene variant as an aid in diagnosis for patients with suspected long QT syndrome

Objective To evaluate the value of functional study of a gene variant in diagnosis for patients with suspected long QT syndrome （LQTS）. Methods The KCNI-I2 mutation M756V was engineered into wild-type （WT） eDNA cloned in pcDNA3.1 plasmid. Patch clamp and immunostaining were performed 48 hours later after transient transfeetion. Results Patch clamp study showed that KCNI-I2 M756V was loss of function compared with WT channel and confirmed that KCNH2 M756V was a mutation of LQTS. KCNH2 M756V did not produce a dominant negative effect on WT channel. Immunostaining showed that KCNH2 M756V protein had a trafficking defect. Conclusions In vitro functional study demonstrates that KCNH2 M756V variant identified in patients with suspected LQTS is a LQTS mutation, suggesting that in vitro functional study will provide more information for the diagnosis of the patients with suspected LQTS.