Rabbit skeletal muscle troponin, C subunit (>95%)

Stem cell-based therapy in cardiac tissue engineering is an emerging field that shows great potential for treating heart diseases. However, even preliminary issues, such as the ideal niche for cardiomyocytes, have not been clarified yet. In the present study, the effects of extracellular matrix (ECM) components on the beating duration of neonatal rat cardiomyocytes (RCMs) and on the cardiac differentiation of P19.CL6 carcinoma stem cells were studied. RCMs were cultured on gelatin-, fibronectin-, and collagen type I-coated dishes and on noncoated polystyrene dishes, and their beating rate, beating duration, and cardiac gene expression were evaluated. The beating period and the expression of troponin T type-2 (TNNT2) and troponin C type-1 (TNNC1) of cardiomyocytes cultured on gelatin-coated dishes were longer and higher than for those on dishes with other coatings. For the cardiac differentiation of P19.CL6 cells, troponin T type-2 expression on gelatin- and fibronectin-coated dishes was five times that on collagen type I-coated dishes or polystyrene dishes 11days after induction. These results indicate that a gelatin-coated surface has a high ability not only to maintain the cardiac phenotype but also to enhance cardiac differentiation.

Defined as clinically unexplained hypertrophy of the left ventricle, hypertrophic cardiomyopathy (HCM) is traditionally understood as a disease of the cardiac sarcomere. Mutations in TNNC1-encoded cardiac troponin C (cTnC) are a relatively rare cause of HCM. Here, we report clinical and functional characterization of a novel TNNC1 mutation, A31S, identified in a pediatric HCM proband with multiple episodes of ventricular fibrillation and aborted sudden cardiac death. Diagnosed at age 5, the proband is family history-negative for HCM or sudden cardiac death, suggesting a de novo mutation. TnC-extracted cardiac skinned fibers were reconstituted with the cTnC-A31S mutant, which increased Ca2+ sensitivity with no effect on the maximal contractile force generation. Reconstituted actomyosin ATPase assays with 50% cTnC-A31S:50% cTnC-WT-demonstrated Ca2+ sensitivity that was intermediate between 100% cTnC-A31S and 100% cTnC-WT, whereas the mutant increased the activation of the actomyosin ATPase without affecting the inhibitory qualities of the ATPase. The secondary structure of the cTnC mutant was evaluated by circular dichroism, which did not indicate global changes in structure. Fluorescence studies demonstrated increased Ca2+ affinity in isolated cTnC, the troponin complex, thin filament, and to a lesser degree, thin filament with myosin subfragment 1. These results suggest that this mutation has a direct effect on the Ca2+ sensitivity of the myofilament, which may alter Ca2+ handling and contribute to the arrhythmogenesis observed in the proband. In summary, we report a novel mutation in the TNNC1 gene that is associated with HCM pathogenesis and may predispose to the pathogenesis of a fatal arrhythmogenic subtype of HCM.