Mutations in SCN3A cause early infantile epileptic encephalopathy

Objective Voltage-gated sodium (Na+) channels underlie action potential generation and propagation and hence are central to the regulation of excitability in the nervous system. Mutations in the genes SCN1A, SCN2A, and SCN8A, encoding the Na+ channel pore-forming (α) subunits Nav1.1, 1.2, and 1.6, respectively, and SCN1B, encoding the accessory subunit β1, are established causes of genetic epilepsies. SCN3A, encoding Nav1.3, is known to be highly expressed in brain, but has not previously been linked to early infantile epileptic encephalopathy. Here, we describe a cohort of four patients with epileptic encephalopathy and heterozygous de novo missense variants in SCN3A (p.Ile875Thr in two cases, p.Pro1333Leu, and p.Val1769Ala).