Nav-igating through a complex landscape: SCN10A and cardiac conduction.

Genome-wide association studies (GWAS) have implicated SCN10A, which encodes a nociceptor-associated voltage-gated sodium channel subunit, as a modulator of cardiac conduction; however, this role has traditionally been ascribed to SCN5A, which is highly expressed in cardiac muscle. SCN10A is believed to affect cardiac conduction either directly through cardiomyocytes or indirectly via intracardiac neurons. In this issue of the JCI, van den Boogaard and colleagues introduce a third possibility: that the SCN10A locus acts as an enhancer of SCN5A gene expression. The authors demonstrate that SCN10A expression is negligible within human and murine hearts, and that a T-box enhancer within the SCN10A locus drives SCN5A expression within cardiomyocytes. This work reasserts SCN5A as the key determinant of cardiac conduction and highlights the importance of deciphering the functionality of coding versus noncoding regions when interpreting GWAS data.