Myofibrillogenesis Visualized in Living Embryonic Cardiomyocytes

Myofibril formation was visualized in cultured live cardiomyocytes that were transfected with plasmids expressing green fluorescent protein (GFP) linked to the Z-band protein, α -actinin. The expression of this fluorescent protein provided an in vivo label for structures containing α -actinin. The G...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1997-08, Vol.94 (17), p.9493-9498
Main Authors: Dabiri, Guissou A., Turnacioglu, Kenan K., Sanger, Jean M., Sanger, Joseph W.
Format: Article
Language:English
Subjects:
Actinin - analysis
Actins
Animals
Antibodies
Biological Sciences
Cell aggregates
Cells
Cellular biology
Chick Embryo
Cultured cells
Embryos
Green Fluorescent Proteins
Heart
Heart - embryology
Luminescent Proteins
Microscopy, Video
Muscle development
Myocardium
Myocardium - cytology
Myofibrils
Myofibrils - ultrastructure
Physiology
Plasmids
Proteins
Solar fibrils
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Summary:Myofibril formation was visualized in cultured live cardiomyocytes that were transfected with plasmids expressing green fluorescent protein (GFP) linked to the Z-band protein, α -actinin. The expression of this fluorescent protein provided an in vivo label for structures containing α -actinin. The GFP-α -actinin fusion protein was incorporated into Z-bands, intercalated discs, and attachment plaques, as well as into the punctate aggregates, or Z-bodies, that are thought to be the precursors of Z-bands. Observations of live cells over several days in culture permitted us to test aspects of several theories of myofibril assembly that had been proposed previously based on the study of fixed cells. Fine fibrils, called premyofibrils, that formed de novo at the spreading edges of cardiomyocytes, contained punctate concentrations of α -actinin, termed Z-bodies. The punctate Z-bodies grew and aligned with Z-bodies in adjacent fibrils. With increasing time, adjacent fibrils and Z-bodies appeared to fuse and form mature myofibrils and Z-bands in cytoplasmic regions where the linear arrays of Z-bodies had been. These new myofibrils became aligned with existing myofibrils at their Z-bands to form myofibrils that spanned the length of the spread cell. These results are consistent with a model that postulates that the fibrils that form de novo near the cell membrane are premyofibrils--i.e., the precursors of mature myofibrils.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.94.17.9493