Truncated cardiac myosin binding protein-C markedly abbreviated the systolic elastance time course, peaking earlier (27.6 vs 47.8 ms) and reducing peak elastance compared to wild-type controls.
Does homozygous truncated cMyBP-C mutation alter the time course and magnitude of left ventricular systolic elastance in male mice?
Deficient incorporation of cMyBP-C leads to abnormal sarcomere shortening velocity and abbreviated muscle stiffening, providing mechanistic insights into the development of associated cardiac dysfunction.
Absolute Event Rate: 0% vs 0%
Despite advances in the molecular biology of cardiac myosin binding protein-C (cMyBP-C), little is understood about its precise role in muscle contraction, particularly in the intact heart. We tested the hypothesis that cMyBP-C is central to the time course and magnitude of left ventricular systolic elastance (chamber stiffening), and assessed mechanisms for this influence in intact hearts, trabeculae, and skinned fibers from wild-type (+/+) and homozygous truncated cMyBP-C (t/t) male mice. cMyBP-C protein was not detected by gel electrophoresis or Western blot in t/t myocardium. cMyBP-C t/t ventricles displayed reduced peak elastance, but more strikingly a marked abbreviation of the systolic elastance time course, which peaked earlier (27.6+/-2.1 ms) than in +/+ controls (47.8+/-1.6 ms). Control hearts reached only 42+/-4% of maximum elastance at the onset of ejection, with substantial further stiffening during ejection. This contrasted to t/t mutants, which reached 77+/-3% of peak elastance before ejection of peak. These unusual findings were not observed in alternative models involving severe cardiomyopathy, but were recapitulated in a cMyBP-C null mouse. The abbreviated elastance time course and lower peak were consistent with earlier time-to-peak trabecular tension, increased unloaded shortening velocity in t/t skinned muscle strips, and dramatically reduced myofilament stiffness at diastolic calcium concentrations. These results provide novel insights into the role of cMyBP-C in myocardial systolic mechanics. Abnormal sarcomere shortening velocity and abbreviated muscle stiffening may underlie development of cardiac dysfunction associated with deficient incorporation of cMyBP-C.
Palmer et al. (Tue,) reported a other. Truncated cardiac myosin binding protein-C markedly abbreviated the systolic elastance time course, peaking earlier (27.6 vs 47.8 ms) and reducing peak elastance compared to wild-type controls.