Heterozygous disruption of the mouse cardiac sodium channel gene Scn5a caused a ~50% reduction in sodium conductance, leading to impaired atrioventricular conduction and ventricular tachycardia.
Does targeted disruption of the Scn5a gene alter cardiac conduction and arrhythmogenesis in mice?
Heterozygous disruption of the cardiac sodium channel gene Scn5a in mice reduces sodium conductance by ~50%, leading to impaired conduction, increased refractoriness, and ventricular tachycardia, providing a model for human SCN5A-related arrhythmias.
Absolute Event Rate: 21% vs 37%
p-value: p=<0.01
Voltage-gated sodium channels drive the initial depolarization phase of the cardiac action potential and therefore critically determine conduction of excitation through the heart. In patients, deletions or loss-of-function mutations of the cardiac sodium channel gene, SCN5A, have been associated with a wide range of arrhythmias including bradycardia (heart rate slowing), atrioventricular conduction delay, and ventricular fibrillation. The pathophysiological basis of these clinical conditions is unresolved. Here we show that disruption of the mouse cardiac sodium channel gene, Scn5a, causes intrauterine lethality in homozygotes with severe defects in ventricular morphogenesis whereas heterozygotes show normal survival. Whole-cell patch clamp analyses of isolated ventricular myocytes from adult Scn5a(+/-) mice demonstrate a approximately 50% reduction in sodium conductance. Scn5a(+/-) hearts have several defects including impaired atrioventricular conduction, delayed intramyocardial conduction, increased ventricular refractoriness, and ventricular tachycardia with characteristics of reentrant excitation. These findings reconcile reduced activity of the cardiac sodium channel leading to slowed conduction with several apparently diverse clinical phenotypes, providing a model for the detailed analysis of the pathophysiology of arrhythmias.
Papadatos et al. (Tue,) conducted a other in Cardiac arrhythmias (Scn5a mutation model). Heterozygous disruption of Scn5a gene (Scn5a+/-) vs. Wild-type mice was evaluated on Peak sodium current density (pA/pF) (p=<0.01). Heterozygous disruption of the mouse cardiac sodium channel gene Scn5a caused a ~50% reduction in sodium conductance, leading to impaired atrioventricular conduction and ventricular tachycardia.