Cellular and molecular aspects of familial hypertrophic cardiomyopathy caused by mutations in the cardiac troponin I gene.

Mutations in the cardiac troponin I (CTnI) gene occur in approximately 5% of families with familial hypertrophic cardiomyopathy (FHC) and 20 mutations in this gene that cause FHC have now been described. The clinical manifestations of CTnI mutations that cause FHC are diverse, ranging from asymptomatic with high life expectancy to severe heart failure and sudden cardiac death. Most of these FHC mutations in CTnI result in cardiac hypertrophy unlike cardiac troponin T FHC mutations. All CTnI FHC mutations investigated in vitro affect the physiological function of CTnI, but other factors such as environmental or genetic factors (other genes that may affect the CTnI gene) are likely to be involved in influencing the severity of the phenotype produced by these mutations, since the distribution of hypertrophy among affected individuals varies within and between families. CTnI mutations mainly alter myocardial performance via changes in the Ca2+ -sensitivity of force development and in some cases alter the muscle relaxation kinetics due to haemodynamic or physical obstructions of blood flow from the left ventricle.