Abstract 11710: A Gene Targeted Murine Model of the Human Cardiac Troponin T (TNNT2) R141W Mutation Develops Dilated Cardiomyopathy with Calcium Desensitization
BACKGROUND: Many prior studies of the mechanisms leading to hereditary dilated cardiomyopathy (DCM) have been performed in reconstituted in vitro systems. Genetically engineered murine models offer the opportunity to dissect these mechanisms in vivo. We generated a gene targeted knock-in murine model of the autosomal dominant Arg141Trp (R141W) mutation in Tnnt2, which was first described in a human family with DCM.
METHODS AND RESULTS: Mice heterozygous for the mutation (Tnnt2R141W/+) recapitulated the human phenotype, developing left ventricular dilation and reduced contractility. There was a gene dosage effect, so that mice homozygous for the mutation (Tnnt2R141W/R141W) developed a more severely abnormal phenotype. In contrast, the phenotype was attenuated in these mice by transgenic overexpression of wildtype cTnT. Furthermore, male mice exhibited poorer survival than female mice. Ventricular remodeling appeared to be mediated by NF-κB, cardiotrophin-1, and CAMKII signaling. Crossing Tnnt2R141W/R141W mice with phospholamban knockout (Pln-/-) mice, that exhibit increased Ca2+ sensitivity and contractility, attenuated the phenotype of ventricular dilation and reduced contractility. Biomechanical studies on skinned fibers from Tnnt2R141W/+ hearts showed a significantly increased pCa50 relative to wildtype hearts, indicating Ca2+ desensitization. Using a Ca2+ sensitive dye, optical mapping studies of isolated Tnnt2R141W/+ hearts showed increased diastolic intracellular Ca2+ ([Ca2+]i), a slower rate of systolic rise of [Ca2+]i, increased peak systolic [Ca2+]i, and a slower rate of diastolic fall in [Ca2+]i (Figure).
CONCLUSIONS: DCM secondary to the Tnnt2 R141W mutation is associated with Ca2+ desensitization. These studies suggest a broad impairment in intracellular Ca2+ homeostasis and Ca2+-mediated contractility. .
- © 2012 by American Heart Association, Inc.