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XB-ART-40153
Can J Cardiol 2009 Aug 01;258:455-62. doi: 10.1016/s0828-282x(09)70117-5.
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Characterization of novel KCNH2 mutations in type 2 long QT syndrome manifesting as seizures.

Keller DI , Grenier J , Christé G , Dubouloz F , Osswald S , Brink M , Ficker E , Chahine M .


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BACKGROUND: Long QT syndrome (LQTS) is characterized by corrected QT interval prolongation leading to torsades de pointes and sudden cardiac death. LQTS type 2 (LQTS2) is caused by mutations in the KCNH2 gene, leading to a reduction of the rapidly activating delayed rectifier K+ current and loss of human ether-à-go-go-related gene (hERG) channel function by different mechanisms. Triggers for life-threatening arrhythmias in LQTS2 are often auditory stimuli. OBJECTIVES: To screen KCNH2 for mutations in patients with LQTS2 on an electrocardiogram and auditory-induced syncope interpreted as seizures and sudden cardiac death, and to analyze their impact on the channel function in vitro. METHODS: The KCNH2 gene was screened for mutations in the index patients of three families. The novel mutations were reproduced in vitro using site-directed mutagenesis and characterized using the Xenopus oocyte expression system in voltage clamp mode. RESULTS: Novel KCNH2 mutations (Y493F, A429P and del234-241) were identified in the index patients with mostly typical LQTS2 features on their electrocardiograms. The biochemical data revealed a trafficking defect. The biophysical data revealed a loss of function when mutated hERG channels were coexpressed with the wild type. CONCLUSIONS: In all families, at least one patient carrying the mutation had a history of seizures after auditory stimuli, which is a major trigger for arrhythmic events in LQTS2. Seizures are likely due to cardiac syncope as a consequence of mutation-induced loss of function of the rapidly activating delayed rectifier K+ current.

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Species referenced: Xenopus
Genes referenced: kcnh2

References [+] :
Chahine, Lidocaine block of human heart sodium channels expressed in Xenopus oocytes. 1992, Pubmed, Xenbase