Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disease originating from mutations in genes that encode for the major contractile proteins of the heart, including the ventricular myosin regulatory (RLC) and essential (ELC) light chains. FHC results in ventricular and septal hypertrophy, myofibrillar disarray and is the leading cause of sudden cardiac death in young individuals. This research is aimed at elucidating the molecular mechanisms involved in triggering of FHC at the level of a single myosin cross-bridge. We propose to test the hypothesis that FHC is caused by inefficient utilization of ATP by cardiac muscle due to alteration of myosin cross-bridge kinetics in transgenic mouse hearts expressing disease-causing mutations in myosin RLC and ELC. We will examine this hypothesis at the single molecule level in papillary muscle fibers from transgenic mouse hearts which carry disease-causing mutations in the regulatory and/or essential light chains of myosin. We strongly believe that the unambiguous determination of myosin cross-bridge kinetics must be carried out at the level of a single cross-bridge and the results compared to cross-bridge mechanics derived from measurements on skinned and intact muscle fibers. The advantage of the single molecule approach is its ability to avoid averaging over ensembles of molecules with different kinetics such as a mixture of WT and FHC molecules, and the ability to unambiguously determine the kinetics of """"""""healthy"""""""" and """"""""diseased"""""""" muscle. Since human patients are heterozygous for FHC mutations and their thick filaments contain interspersed WT and HCM mutant heads it is extremely important to correlate the single molecule information with the phenotype of FHC assessed at the muscle fiber level. Specifically we ask whether the durations (Aim 1A) and lifetimes (Aim 1B) of detached and strongly-bound states are the same in a single cross-bridge from FHC hearts and in healthy transgenic controls. The information derived using this single molecule technology will be paralleled with functional studies of force development, ATPase on skinned papillary muscle fibers as well as force and calcium transients on intact muscle fibers from transgenic mice (Aim 2A). The ultimate objective is to link the single molecule derived data with the cellular findings to fully understand the mechanism of action of the individual RLC and ELC mutations causing FHC (Aim 2B). The fundamental question that is being addressed is why and how these individual mutations in RLC and/or ELC cause variable disease phenotypes in humans ranging from relatively mild to malignant clinical FHC phenotypes. We believe that integration of molecular biology approaches with high resolution optics and nano-fluorescence spectroscopy will enable us to successfully answer important questions regarding the molecular basis of FHC-mediated pathology in the heart and the role of RLC and ELC in cardiac muscle contraction.

Public Health Relevance

This research is directed toward unraveling the mechanisms of familial hypertrophic cardiomyopathy, a major public health problem. The goal of this proposal is to understand the molecular bases by which mutations in the sarcomeric myosin light chains lead to cardiac hypertrophy in humans. Successful completion of this goal may lead to new modalities of treatment of a serious heart disease. The strength of this application is formed by its combination of molecular biological and nano-fluorescence microscopic approaches in the study disease-causing mutations at the level of a single molecule. Furthermore, the integration of single molecule approaches with the physiological assessment of the diseased muscle will enable us to successfully answer important questions regarding the molecular basis of FHC-mediated pathology in the heart.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-CVS-D (02))
Program Officer
Adhikari, Bishow B
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of North Texas
Other Domestic Higher Education
Fort Worth
United States
Zip Code
Wang, Li; Kazmierczak, Katarzyna; Yuan, Chen-Ching et al. (2017) Cardiac contractility, motor function, and cross-bridge kinetics in N47K-RLC mutant mice. FEBS J 284:1897-1913
Duggal, Divya; Requena, S; Nagwekar, Janhavi et al. (2017) No Difference in Myosin Kinetics and Spatial Distribution of the Lever Arm in the Left and Right Ventricles of Human Hearts. Front Physiol 8:732
Nagwekar, Janhavi; Duggal, Divya; Midde, Krishna et al. (2015) A Novel Method of Determining the Functional Effects of a Minor Genetic Modification of a Protein. Front Cardiovasc Med 2:35
Duggal, D; Nagwekar, J; Rich, R et al. (2015) Effect of a myosin regulatory light chain mutation K104E on actin-myosin interactions. Am J Physiol Heart Circ Physiol 308:H1248-57
Shumilov, Dmytro; Popov, Alexander; Fudala, Rafal et al. (2014) Real-time imaging of exocytotic mucin release and swelling in Calu-3 cells using acridine orange. Methods 66:312-24
Huang, Wenrui; Liang, Jingsheng; Kazmierczak, Katarzyna et al. (2014) Hypertrophic cardiomyopathy associated Lys104Glu mutation in the myosin regulatory light chain causes diastolic disturbance in mice. J Mol Cell Cardiol 74:318-29
Duggal, Divya; Nagwekar, Janhavi; Rich, Ryan et al. (2014) Phosphorylation of myosin regulatory light chain has minimal effect on kinetics and distribution of orientations of cross bridges of rabbit skeletal muscle. Am J Physiol Regul Integr Comp Physiol 306:R222-33
Nagwekar, J; Duggal, D; Rich, R et al. (2014) The spatial distribution of actin and mechanical cycle of myosin are different in right and left ventricles of healthy mouse hearts. Biochemistry 53:7641-9
Midde, Krishna; Rich, Ryan; Saxena, Ashwini et al. (2014) Membrane topology of human presenilin-1 in SK-N-SH cells determined by fluorescence correlation spectroscopy and fluorescent energy transfer. Cell Biochem Biophys 70:923-32
Midde, Krishna; Rich, Ryan; Marandos, Peter et al. (2013) Comparison of orientation and rotational motion of skeletal muscle cross-bridges containing phosphorylated and dephosphorylated myosin regulatory light chain. J Biol Chem 288:7012-23

Showing the most recent 10 out of 33 publications