Abstract Body: Duchenne muscular dystrophy (DMD) is a progressive disease caused by the complete loss of the protein dystrophin. This loss leads to the development of cardiomyopathy which is fatal. It has been shown that without dystrophin, the muscle membrane becomes de-stabilized, leading to damage resulting in muscle weakening and cardiac failure. This makes understanding the mechanisms driving cardiomyopathy in DMD at the cellular level critical for the design of effective treatments.

The bulk of the work to address DMD progression and treatment has focused on the loss of dystrophin in skeletal muscles. Presently, there is limited understanding of the development of cardiomyopathy, although it is the leading cause of death, and the pathology is unknown. This severely limits the ability to develop novel therapeutics to ameliorate cardiac failure. This project implements a novel biosensor to monitor, in live cardiac muscle, thin filament activation in real-time. The biosensor fuses fluorescent donor and acceptor proteins to the calcium-sensing cardiac troponin C (TnC). Using the biosensor, cardiac muscle activation will be monitored based on the detection of Förster Resonance Energy Transfer (FRET). In this system, all essential features of the muscle remain intact, including excitation-contraction coupling and muscle load.

By utilizing the biosensor, this work will examine changes in myofilament states in DMD models in a loaded system, which closely represents in vivo cardiac muscle function. We have already seen a significant decrease in force in mdx papillary muscles as compared to controls. Additionally, the use of sarcomere specific small molecules targeting both the thin and thick filament will be used to examine the role of these sarcomeric components in the development of DMD-driven cardiomyopathy. The results of this project will provide new knowledge of the mechanisms of sarcomere activation in DMD-driven heart disease and provide a platform to test novel small molecules for the treatment of the lethal cardiomyopathy.