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Myofibrillogenesis visualized in living embryonic cardiomyocytes
G A Dabiri1, K K Turnacioglu, J M Sanger
1Department of Cell and Developmental Biology and Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
Summary
Live cardiomyocyte imaging reveals that premyofibrils, containing alpha-actinin Z-bodies, assemble into mature myofibrils. This study visualizes myofibril formation in real-time, supporting a model of de novo assembly at the cell periphery.
Area of Science:
- Cell Biology
- Muscle Physiology
- Biochemistry
Background:
- Myofibril assembly is crucial for cardiomyocyte function.
- Previous models of myofibril formation were based on fixed cell studies.
- The role of Z-bodies as myofibril precursors requires in vivo validation.
Purpose of the Study:
- To visualize and characterize myofibril formation in live cardiomyocytes.
- To investigate the role of alpha-actinin and Z-bodies in myofibril assembly.
- To test existing theories of myofibril formation using live-cell imaging.
Main Methods:
- Transfection of cultured cardiomyocytes with green fluorescent protein (GFP)-alpha-actinin fusion protein.
- Live-cell imaging over several days to observe dynamic processes.
- In vivo labeling of Z-band structures and their assembly.
Main Results:
- GFP-alpha-actinin localized to Z-bands, intercalated discs, attachment plaques, and Z-bodies.
- Premyofibrils, containing punctate Z-bodies, formed de novo at cardiomyocyte edges.
- Z-bodies grew, aligned, and fused to form mature myofibrils and Z-bands.
- Newly formed myofibrils aligned with existing ones, spanning the cell length.
Conclusions:
- The study supports a model where premyofibrils are precursors to mature myofibrils.
- Live imaging provides dynamic insights into myofibril assembly distinct from fixed-cell studies.
- Alpha-actinin incorporation into Z-bodies is a key early event in myofibrillogenesis.