SCN4A and developmental and epileptic encephalopathy: For example, analogous to the Nav1.4 R1469 residue, the R1642C mutation (in Nav1.3) leads to developmental epileptic encephalopathy (Zaman et al., 2018), and R1644C/H mutations in Nav1.5 (analogous to R1469 in Nav1.4) cause cardiac arrythmias, characterized by accelerated rates of channel recovery from inactivation (Frustaci et al., 2005).