TNNI3 and cardiomyopathy: Mutations in TNNC1, TNNI3, and TNNT2 have been identified as relatively uncommon causes of cardiomyopathy, such as DCM, HCM, and RCM, when compared with the frequency of mutations in other sarcomere genes,36,37,88,89 probably because most of them are not compatible with life.