Muscle Research Seminar Series
Alison Schroer, Ph.D.
Post-doctoral Fellow, Microsystems, Spudich and Bernstein Labs, Stanford University
“Modeling Altered Biomechanics of Myosin with Disease Causing Mutations Across Molecular and Cellular Scales”
Monday, March 2, 2020, 4:00 – 5:00 PM
Room E130A/B, UW Medicine at South Lake Union
850 Republican Street, Seattle WA
Hypertrophic cardiomyopathy (HCM) is the most prevalent form of heritable cardiovascular disease, most commonly caused by mutations in sarcomeric proteins including beta cardiac myosin heavy chain (bMHC). The dominant clinical phenotype is marked by cardiomyocyte hypertrophy and hypercontractility. We have measured the kinetics of isolated myosin proteins with different HCM mutations in bMHC and found intriguing heterogeneity in molecular function, some leading to an increase in force and velocity and others to a decrease. How divergent molecular alterations converge to the final HCM phenotype is still unknown. Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) provide a powerful tool for studying human cardiomyocyte biology including contractility, hypertrophic growth, and intracellular organization. Using CRISPR/Cas-9 gene editing in an isogenic hiPSC line, we created hiPSCs with two different bMHC mutations (P710R and D239N) that result in opposite effects on velocity and ATPase activity at the molecular level. Despite having opposite effects at the single molecule level, both HCM lines showed increased contractile force and cellular hypertrophy compared to isogenic controls when cultured on micropatterned platforms. For P710R, with reduced molecular contractility, this appears to be due to increased availability of myosin heads due to a decrease in the SRX (super relaxed) state. We are also using intramolecular FRET probes to measure intracellular forces experienced due to HCM mutations, and computational models to predict and understand how changes in force and kinetics contribute to cellular and tissue remodeling. Cellular level experiments provide an important complement to molecular studies of HCM mutations, demonstrating that divergent molecular-level biomechanical alterations lead to a common cellular-level biomechanical phenotype.
Sponsors: The Senator Paul D. Wellstone Muscular Dystrophy Specialized Research Center at UW is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) of the National Institutes of Health under Award Number P50AR065139. The UW Center for Translational Muscle Research is supported by NIAMS Award Number P30AR074990.
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