TNNI3 and cardiomyopathy: Cardiac-type troponin I3 and sodium channel protein type 5 subunit alpha are severally encoded by TNNI3 and SCN5A. Seven of 42 patients with acute myocarditis carry infrequent biallelic nonsynonymous or splice-site variations in cardiomyopathy-related TNNI3 or SCN5A [93].