p.D1690N sodium voltage-gated channel subunit 5 mutation reduced sodium current density and is associated with Brugada syndrome

Brugada syndrome (BrS) is an inherited primary arrhythmia disorder, leading to sudden cardiac death due to ventricular tachyarrhythmia, but does not exhibit clinical cardiac abnormalities. The sodium voltage-gated channel subunit 5 (SCN5A) gene, which encodes the subunit of the cardiac sodium channel, Nav1.5, is the most common pathogenic gene, although 22 BrS-susceptibility genes have previously been identified. In the present study, a novel genetic variant (p.D1690N) localized in the S5-S6 linker of domain IV of the Nav1.5 channels was identified in a Chinese Han family. Wild-type (WT) and p.D1690N Nav1.5 channels were transiently over-expressed in HEK293 cells and analyzed via the whole-cell patch clamp technique. The p.D1690N mutation significantly reduced the peak sodium current density to 23% of WT (at -20 mV; P<0.01), shifted steady-state activation by 7 mV to increasingly positive potentials (P<0.01). Furthermore, prolonging of the recovery from inactivation was observed in the p.D1690N mutant. No significant change was identified in steady-state inactivation. Thus, the mutant-induced changes contributed to the loss of function of Nav1.5 channels, which indicates that the p.D1690N variant may have a pathogenic role in BrS.