Epigenetic Changes Governing Scn5a Expression in Denervated Skeletal Muscle

Abstract

The <i>SCN5A</i> gene encodes the α-subunit of the voltage-gated cardiac sodium channel (Na_V1.5), a key player in cardiac action potential depolarization. Genetic variants in protein-coding regions of the human <i>SCN5A</i> have been largely associated with inherited cardiac arrhythmias. Increasing evidence also suggests that aberrant expression of the <i>SCN5A</i> gene could increase susceptibility to arrhythmogenic diseases, but the mechanisms governing <i>SCN5A</i> expression are not yet well understood. To gain insights into the molecular basis of <i>SCN5A</i> gene regulation, we used rat gastrocnemius muscle four days following denervation, a process well known to stimulate <i>Scn5a</i> expression. Our results show that denervation of rat skeletal muscle induces the expression of the adult cardiac <i>Scn5a</i> isoform. RNA-seq experiments reveal that denervation leads to significant changes in the transcriptome, with <i>Scn5a</i> amongst the fifty top upregulated genes. Consistent with this increase in expression, ChIP-qPCR assays show enrichment of H3K27ac and H3K4me3 and binding of the transcription factor Gata4 near the <i>Scn5a</i> promoter region. Also, Gata4 mRNA levels are significantly induced upon denervation. Genome-wide analysis of H3K27ac by ChIP-seq suggest that a super enhancer recently described to regulate <i>Scn5a</i> in cardiac tissue is activated in response to denervation. Altogether, our experiments reveal that similar mechanisms regulate the expression of <i>Scn5a</i> in denervated muscle and cardiac tissue, suggesting a conserved pathway for <i>SCN5A</i> expression among striated muscles.