Characterization of an N-terminal Na_v1.5 channel variant - a potential risk factor for arrhythmias and sudden death?

BACKGROUND:Alterations in the SCN5A gene encoding the cardiac sodium channel Na_v1.5 have been linked to a number of arrhythmia syndromes and diseases including long-QT syndrome (LQTS), Brugada syndrome (BrS) and dilative cardiomyopathy (DCM), which may predispose to fatal arrhythmias and sudden death. We identified the heterozygous variant c.316A > G, p.(Ser106Gly) in a 35-year-old patient with survived cardiac arrest. In the present study, we aimed to investigate the functional impact of the variant to clarify the medical relevance. METHODS:Mutant as well as wild type GFP tagged Na_v1.5 channels were expressed in HEK293 cells. We performed functional characterization experiments using patch-clamp technique. RESULTS:Electrophysiological measurements indicated, that the detected missense variant alters Nav1.5 channel functionality leading to a gain-of-function effect. Cells expressing S106G channels show an increase in Na_v1.5 current over the entire voltage window. CONCLUSION:The results support the assumption that the detected sequence aberration alters Na_v1.5 channel function and may predispose to cardiac arrhythmias and sudden cardiac death.

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