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Published on: November 3, 2020
Structure of the Thin Filament in Human iPSC-derived Cardiomyocytes and its Response to Heart Disease
Rahel A Woldeyes1, Masataka Nishiga2,3, Alison S Vander Roest4,5
1Department of Bioengineering, Stanford University, Stanford, CA, USA.
Insights
This study uses advanced cryo-electron tomography to reveal the structure of human cardiac thin filaments and troponin complexes within heart cells. Findings show disease-related changes in troponin structure, offering insights into cardiovascular disease mechanisms.
Area of Science:
- Structural biology
- Cardiovascular research
- Cellular imaging
Background:
- Cardiovascular diseases are a major global health concern with complex underlying mechanisms.
- Understanding heart muscle contraction requires detailed knowledge of cellular machinery.
- Cryo-electron tomography (cryo-ET) offers high-resolution cellular visualization but is underutilized in cardiomyocyte studies.
Purpose of the Study:
- To establish an optimized cryo-ET platform for studying human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).
- To visualize and reconstruct the structure of the human cardiac muscle thin filament and troponin complex in situ.
- To investigate how cardiovascular disease-associated perturbations affect troponin structure.
Main Methods:
- Development and application of an optimized cryo-electron tomography (cryo-ET) platform.
- High-resolution structural reconstruction of cardiac thin filaments and the troponin complex within hiPSC-CMs.
- Analysis of structural changes in troponin following chemical and genetic perturbations relevant to cardiovascular disease.
Main Results:
- Achieved sub-nanometer resolution structures of the human cardiac muscle thin filament.
- Reconstructed the troponin complex in its cellular context, revealing novel conformations and structural flexibility.
- Observed troponin structural alterations consistent with disease phenotypes upon perturbation.
Conclusions:
- The developed cryo-ET platform enables cellular structural biology in hiPSC-CMs.
- Novel troponin conformations provide insights into cardiac muscle regulation.
- This approach is valuable for dissecting cardiovascular disease mechanisms at a molecular and cellular level.
Abstract:
Cardiovascular diseases are a leading cause of death worldwide, but our understanding of the underlying mechanisms is limited, in part because of the complexity of the cellular machinery that controls the heart muscle contraction cycle. Cryogenic electron tomography (cryo-ET) provides a way to visualize diverse cellular machinery while preserving contextual information like subcellular localization and transient complex formation, but this approach has not been widely applied to the study of heart muscle cells (cardiomyocytes). Here, we deploy an optimized cryo-ET platform that enables cellular-structural biology in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Using this platform, we reconstructed sub-nanometer resolution structures of the human cardiac muscle thin filament, a central component of the contractile machinery. Reconstructing the troponin complex, a regulatory component of the thin filament, from within cells, we identified previously unobserved conformations that highlight the structural flexibility of this regulatory complex. We next measured the impact of chemical and genetic perturbations associated with cardiovascular disease on the structure of troponin. In both cases, we found changes in troponin structure that are consistent with known disease phenotypes-highlighting the value of our approach for dissecting complex disease mechanisms in the cellular context.
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