Abstract 395: A Synonymous Coding SNP Alters SCN5A Regulation by miR-24 and Associates With Non-Arrhythmic Death in Heart Failure

Abstract

Mutations disrupting SCN5A coding sequence cause inherited arrhythmias and cardiomyopathy, and SNPs linked to SCN5A splicing, localization and function associate with heart failure-related sudden cardiac death. However, the clinical relevance of SNPs that modulate SCN5A expression levels remains understudied. Recently, we generated a transcriptome-wide map of microRNA (miR) binding sites in human heart and evaluated their interface with polymorphisms. Among >500 common SNPs residing within miR target regions, we identified a synonymous SNP (rs1805126) adjacent to a miR-24 site within SCN5A coding sequence. This SNP is known to reproducibly associate with heart rhythm measurements, but is not considered to be “causal”. Here, we show that miR-24 potently suppresses SCN5A and that rs1805126 modulates this regulation. In further exploring the clinical significance of this, we found that rs1805126 minor allele homozygosity associates with decreased cardiac SCN5A expression and increased mortality in heart failure patients. Unexpectedly, this risk was not linked with arrhythmic sudden cardiac death, but rather, with clinical signs of worsening heart failure (e.g. reduced ejection fraction) and myocardial gene expression changes related to bioenergetics, inflammation and extracellular remodeling. Together, these data attribute a molecular mechanism to this firmly-established GWAS SNP and highlight a novel and surprising link between common variations in SCN5A expression and non-arrhythmic death in heart failure.