Clinical and Functional Characterization of TNNT2 Mutations Identified in Patients with Dilated Cardiomyopathy

BACKGROUND: A key issue for cardiovascular genetic medicine is ascertaining if a putative mutation indeed causes dilated cardiomyopathy (DCM). This is critically important as genetic DCM, usually presenting with advanced, life-threatening disease, may be preventable with early intervention in relatives known to carry the mutation. METHODS AND RESULTS: We recently undertook bidirectional resequencing of TNNT2, the cardiac troponin T gene, in 313 probands with DCM. We identified 6 TNNT2 protein-altering variants in 9 probands, all who had early onset, aggressive disease. Additional family members of mutation carriers were then studied when available. Four of the 9 probands had DCM without a family history, and 5 probands had familial DCM. Only 1 mutation (Lys210del) could be attributed as definitively causative from previous reports. Four of the 5 missense mutations were novel (Arg134Gly, Arg151Cys, Arg159Gln, and Arg205Trp), and one was previously reported with hypertrophic cardiomyopathy (Glu244Asp). Based on the clinical, pedigree, and molecular genetic data, these 5 mutations were considered possibly or likely disease causing. To further clarify their potential pathophysiologic impact, we undertook functional studies of these mutations in cardiac myocytes reconstituted with mutant troponin T proteins. We observed decreased Ca(2+) sensitivity of force development, a hallmark of DCM, in support of the conclusion that these mutations are disease causing. CONCLUSIONS: We conclude that the combination of clinical, pedigree, molecular genetic, and functional data strengthen the interpretation of TNNT2 mutations in DCM.