MYH7 mutations induce changes in single cell mechanobiology
Abstract:
Hypertrophic Cardiomyopathy (HCM) is characterized by thickening of the left ventricular wall and hypercontractility and has been linked to mutations in the sarcomere motor protein β-myosin (MYH7). Using single cell mechanobiology studies, we examined how the effects of single point mutations propagate to change the contractile dynamics and cellular morphology (sarcomere spacing, spread area, myofibril alignment) of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs). We micropattern islands of adhesive protein to constraining the spreading and alignment of hiPSC-CM on hydrogel substrates containing fluorescent microbeads as fiducial markers for traction force microscopy (TFM). We deployed substrate stiffnesses ranging from physiological (10 kPa) to heavily diseased/fibrotic (100 kPa) to test the role of increased “afterload” in functional phenotypes. We use image and video analysis to assess the contractile dynamics of the hiPSC-CM in terms of force, power, and velocities of relaxation and contraction. For example, we assessed multiple MYH7 mutations edited into the WTC line along with isogenic controls. Some lines carried an endogenously labeled alpha-actinin GFP reporter of sarcomere structure to enable visualization of sarcomere structure and dynamics. We assessed the magnitude and dynamics of contractile force output from TFM video analysis and observed increased the contractile force when compared to the control hiPSC-CMs. We also measured significantly different dynamics in the relaxation or contraction velocities compared to control hiPSC-CMs. Interestingly, not all HCM mutant lines presented a significant increase in cell spread area, a proxy for hypertrophy, and this correlated with culture conditions, such as the size of the protein pattern constraining the cells or stiffness of the substrate. Taken together, these results suggest a role for MYH7 mutations driving remodeling of structure and function at a cell-intrinsic level via changes in mechanosignaling.
Bio:
Dr. Beth Pruitt graduated from the Massachusetts Institute of Technology (MIT) with an S.B. in mechanical engineering. She was supported by a Navy ROTC fellowship at MIT where she learned sailing, leadership, and perseverance. She earned an M.S. in Manufacturing Systems Engineering from Stanford University before serving as an officer in the U.S. Navy. Her first tour was at the engineering headquarters of the Navy nuclear program providing engineering review and oversight to refueling operations. Her second tour was as at the U.S. Naval Academy as an instructor teaching Systems Engineering during the academic year and offshore sailing in the summer. She earned her Ph.D. in Mechanical Engineering at Stanford University where she specialized in MEMS and small-scale metrologies for electrical contacts and was supported by a Hertz Foundation Fellowship. She was a postdoctoral researcher at the Swiss Federal Institute of Technology Lausanne (EPFL) where she worked on polymer MEMS. Dr. Pruitt founded and led the Microsystems Lab at Stanford for 15 years, with research focused on small-scale metrologies for interdisciplinary micromechanics problems in mechanobiology, biomechanics and sensing. She was a visiting professor in Prof. Viola Vogel's Lab for Applied Mechanobiology in the Department of Health Sciences and Technology at ETH, Zurich in 2012. Dr. Pruitt moved to UC Santa Barbara in 2018 to help launch a biological engineering degree program and department. She has been Director of the Center for Bioengineering since 2019. She is an elected Fellow of BMES, AIMBE, and ASME and Senior Member of IEEE. She has been recognized by the NSF CAREER Award, DARPA Young Faculty Award, Denice Denton Leadership Award.
Hypertrophic Cardiomyopathy (HCM) is characterized by thickening of the left ventricular wall and hypercontractility and has been linked to mutations in the sarcomere motor protein β-myosin (MYH7). Using single cell mechanobiology studies, we examined how the effects of single point mutations propagate to change the contractile dynamics and cellular morphology (sarcomere spacing, spread area, myofibril alignment) of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs). We micropattern islands of adhesive protein to constraining the spreading and alignment of hiPSC-CM on hydrogel substrates containing fluorescent microbeads as fiducial markers for traction force microscopy (TFM). We deployed substrate stiffnesses ranging from physiological (10 kPa) to heavily diseased/fibrotic (100 kPa) to test the role of increased “afterload” in functional phenotypes. We use image and video analysis to assess the contractile dynamics of the hiPSC-CM in terms of force, power, and velocities of relaxation and contraction. For example, we assessed multiple MYH7 mutations edited into the WTC line along with isogenic controls. Some lines carried an endogenously labeled alpha-actinin GFP reporter of sarcomere structure to enable visualization of sarcomere structure and dynamics. We assessed the magnitude and dynamics of contractile force output from TFM video analysis and observed increased the contractile force when compared to the control hiPSC-CMs. We also measured significantly different dynamics in the relaxation or contraction velocities compared to control hiPSC-CMs. Interestingly, not all HCM mutant lines presented a significant increase in cell spread area, a proxy for hypertrophy, and this correlated with culture conditions, such as the size of the protein pattern constraining the cells or stiffness of the substrate. Taken together, these results suggest a role for MYH7 mutations driving remodeling of structure and function at a cell-intrinsic level via changes in mechanosignaling.
Bio:
Dr. Beth Pruitt graduated from the Massachusetts Institute of Technology (MIT) with an S.B. in mechanical engineering. She was supported by a Navy ROTC fellowship at MIT where she learned sailing, leadership, and perseverance. She earned an M.S. in Manufacturing Systems Engineering from Stanford University before serving as an officer in the U.S. Navy. Her first tour was at the engineering headquarters of the Navy nuclear program providing engineering review and oversight to refueling operations. Her second tour was as at the U.S. Naval Academy as an instructor teaching Systems Engineering during the academic year and offshore sailing in the summer. She earned her Ph.D. in Mechanical Engineering at Stanford University where she specialized in MEMS and small-scale metrologies for electrical contacts and was supported by a Hertz Foundation Fellowship. She was a postdoctoral researcher at the Swiss Federal Institute of Technology Lausanne (EPFL) where she worked on polymer MEMS. Dr. Pruitt founded and led the Microsystems Lab at Stanford for 15 years, with research focused on small-scale metrologies for interdisciplinary micromechanics problems in mechanobiology, biomechanics and sensing. She was a visiting professor in Prof. Viola Vogel's Lab for Applied Mechanobiology in the Department of Health Sciences and Technology at ETH, Zurich in 2012. Dr. Pruitt moved to UC Santa Barbara in 2018 to help launch a biological engineering degree program and department. She has been Director of the Center for Bioengineering since 2019. She is an elected Fellow of BMES, AIMBE, and ASME and Senior Member of IEEE. She has been recognized by the NSF CAREER Award, DARPA Young Faculty Award, Denice Denton Leadership Award.
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Organizer
- Philippe Renaud
Contact
- Clémentine Lipp