The protein encoded by this gene is an integral membrane protein and tetrodotoxin-resistant voltage-gated sodium channel subunit. The encoded protein is found primarily in cardiac muscle and is responsible for the initial upstroke of the action potential in an electrocardiogram. Defects in this gene are a cause of long QT syndrome type 3 (LQT3), an autosomal dominant cardiac disease.
^Gee, S H; Madhavan R; Levinson S R; Caldwell J H; Sealock R; Froehner S C (Jan 1998). "Interaction of muscle and brain sodium channels with multiple members of the syntrophin family of dystrophin-associated proteins". J. Neurosci.18 (1): 128–37. PMID9412493.