Key result
Transgenic mice expressing the D166V mutation exhibited a large increase in Ca(2+) sensitivity of force and ATPase (Delta pCa(50)>0.25) and decreased maximal force compared with control mice.
Why the study?
Does the D166V mutation in the ventricular myosin regulatory light chain alter cardiac muscle contraction in transgenic mice?
Does the D166V mutation in the ventricular myosin regulatory light chain alter cardiac muscle contraction in transgenic mice?
Effect estimate: Delta pCa(50)>0.25
The D166V mutation in the ventricular myosin regulatory light chain causes profound alterations in cross-bridge kinetics and calcium sensitivity, providing a molecular mechanism for the malignant familial hypertrophic cardiomyopathy phenotype.
Hypothesis-generating for malignant FHC mechanisms; leaves open translation to human disease and therapy.
Transgenic (Tg) mice expressing approximately 95% of the D166V (aspartic acid to valine) mutation in the ventricular myosin regulatory light chain (RLC) shown to cause a malignant familial hypertrophic cardiomyopathy (FHC) phenotype were generated, and the skinned and intact papillary muscle fibers from the Tg-D166V mice were examined using a Guth muscle research system. A large increase in the Ca(2+) sensitivity of force and ATPase (Delta pCa(50)>0.25) and a significant decrease in maximal force and ATPase were observed in skinned muscle fibers from Tg-D166V mice compared with control mice. The cross-bridge dissociation rate g was dramatically decreased, whereas the energy cost (ATPase/force) was slightly increased in Tg-D166V fibers compared with controls. The calculated average force per D166V cross-bridge was also reduced. Intact papillary muscle data demonstrated prolonged force transients with no change in calcium transients in Tg-D166V fibers compared with control fibers. Histopathological examination revealed fibrotic lesions in the hearts of the older D166V mice. Our results suggest that a charge effect of the D166V mutation and/or a mutation-dependent decrease in RLC phosphorylation could initiate the slower kinetics of the D166V cross-bridges and ultimately affect the regulation of cardiac muscle contraction. Profound cellular changes observed in Tg-D166V myocardium when placed in vivo could trigger a series of pathological responses and result in poor prognosis for D166V-positive patients.
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Kerrick et al. (2008) studied Familial hypertrophic cardiomyopathy. D166V mutation in the ventricular myosin regulatory light chain vs. Control mice was evaluated on Ca(2+) sensitivity of force and ATPase (Delta pCa(50)>0.25). Transgenic mice expressing the D166V mutation exhibited a large increase in Ca(2+) sensitivity of force and ATPase (Delta pCa(50)>0.25) and decreased maximal force compared with control mice.
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