Multiscale investigation of cardiomyopathy-associated mutations in metavinculin

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Project Summary/Abstract Familial cardiomyopathies are genetic heart diseases that involve ventricular remodeling and altered cardiac contractility. These diseases are often caused by mutations in proteins within the sarcomere, the fundamental contractile unit of cardiomyocytes. Mutations in non-sarcomeric proteins involved in mechanotransduction, the process by which cells sense and respond to mechanical force, have also been implicated in cardiomyopathy but have received considerably less attention. For instance, studies of human patients have identified cardiomyopathy-associated mutations in metavinculin, the muscle-specific isoform of the ubiquitous mechanotransducer vinculin, but how these mutations lead to the disease phenotype is not well-understood. Structural studies have shown that the 68-amino acid insert that differentiates metavinculin from vinculin replaces the first alpha-helix in the actin-binding vinculin tail domain. Although this alpha-helix does not directly bind actin, the metavinculin insert results in drastic changes of the organization of actin filaments by metavinculin compared to vinculin, suggesting an allosteric effect on actin binding. The proposed research will test the hypothesis that the pathogenic mechanism of cardiomyopathy caused by mutations in metavinculin involves disruption of cardiac mechanotransduction through impairment of the force-dependent binding of metavinculin to actin. Single- molecule force measurements of metavinculin binding to actin will directly address whether force stabilizes binding of metavinculin to actin, as has been previously demonstrated for vinculin, as well as the effect of pathogenic mutations on this force-dependent binding. The cellular consequences of altered force dependence of metavinculin-actin binding will be investigated in stem cell-derived cardiomyocytes that carry the disease- causing mutations using live-cell imaging of sarcomerogenesis (the establishment of new sarcomeres) and traction force microscopy. These experiments will also be carried out on metavinculin-null cardiomyocytes to elucidate the role of metavinculin in sarcomerogenesis and cellular contractility. The training provided under this fellowship will take place at the Washington University School of Medicine, a world leader in biomedical education and research. The proposed research aligns with the strategic objectives of the NIH by addressing the normal biological function of metavinculin and the pathobiological mechanism underlying the onset and progression of cardiomyopathy caused by mutations in metavinculin. In addition, the proposed training plan will contribute to the strategic objective of developing a scientific workforce capable of accomplishing the NIH’s mission by supporting the development of research, teaching, and professional skills required for the PI to establish a successful independent research program in the field of cardiac mechanobiology.