Characterization of an N-terminal Na1.5 channel variant - a potential risk factor for arrhythmias and sudden death?

Background: Alterations in the SCN5A gene encoding the cardiac sodium channel Na1.5 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 Na1.5 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 Na1.5 current over the entire voltage window.

Conclusion: The results support the assumption that the detected sequence aberration alters Na1.5 channel function and may predispose to cardiac arrhythmias and sudden cardiac death.