Abstract 17132: E258K HCM-Causing Mutation in Myosin Binding Protein-C Accelerates Contractile Kinetics in Non-Hypertrophied Engineered Cardiac Tissue
Mutations in the cardiac myosin binding protein C gene (MYBPC3) are common causes of hypertrophic cardiomyopathy (HCM) in humans. Even though the MYBPC3 E258K missense mutation is among the most prevalent HCM-causing mutations, the mechanism through which it causes disease remains unclear. We developed a novel neonatal murine 3D engineered cardiac tissue (ECT) model and previously presented data showing that Mybpc3 ablation (Mybpc3−/−) accelerates the kinetics of contraction and relaxation in the absence of hypertrophic remodeling in ECT. Furthermore, we showed that expression of wild type human MYBPC3 in Mybpc3−/− ECT (MYBPC3WT) restores contractile function. We hypothesized that adenoviral mediated expression of human E258K MYBPC3 in Mybpc3−/− ECT (MYBPC3E258K) would accelerate contractile kinetics and blunt the effect of dobutamine by abolishing phosphorylation-regulated inhibitory interactions between the C2-M-domain region of cMyBPC and myosin S2. The contractile characteristics of MYBPC3E258K and MYBPC3WT ECT were assessed by measuring force production with electrical stimulation at 6Hz in the presence and absence of dobutamine. The rate of contraction of MYBPC3E258K ECT was significantly faster than in MYBPC3WT ECT both in the absence (42.7±1.2 ms vs. 51.5±5.0 ms time to Fmax; p<0.001) and presence (42.2±1.6 ms vs. 48.0±3.6 ms time to Fmax; p=0.002) of dobutamine pretreatment. Additionally, the rate of relaxation was also significantly faster in MYBPC3E258K than in MYBPC3WT ECT, both in the absence (26.0±1.6 ms vs. 40.4±6.0 ms time to 50% force decay; p<0.001) and presence (22.8±1.0 ms vs. 31.8±4.6 ms time to 50% force decay; p<0.001) of dobutamine pretreatment. This data indicates that E258K primarily affects heart function by accelerating the kinetics of contraction and relaxation, thereby diminishing systolic ejection time. This phenotype is similar to that previously observed in Mybpc3−/− ECT. However, unlike in Mybpc3−/− ECT, dobutamine pretreatment further accelerates the rate of relaxation in MYBPC3E258K ECT. This finding indicates that the E258K mutation does not fully abolish phosphorylation regulated inhibitory interactions between the C2-M-domain region of cMyBPC and myosin S2, as previously postulated.
- © 2010 by American Heart Association, Inc.