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Updated: Jun 13, 2026
08:29
Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Expression and functional activity of four myocardin isoforms
Masaaki Imamura1, Xiaochun Long, Vivek Nanda
1Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, New York 14642, USA.
Gene
|April 14, 2010
Summary
Myocardin (MYOCD) isoforms show distinct tissue-specific expression in smooth and cardiac muscle across species. Different MYOCD variants exhibit varying activities on cardiac promoters, suggesting functional specialization.
Area of Science:
- Molecular Biology
- Genetics
- Cardiovascular Research
Background:
- Myocardin (MYOCD) is a key regulator of contractile gene expression in muscle cells.
- The Myocd gene undergoes alternative splicing, producing multiple isoforms.
- Understanding MYOCD isoform expression and function is crucial for muscle biology.
Purpose of the Study:
- To investigate the tissue-specific expression of Myocd splice variants in mouse, rat, and human.
- To determine the conservation of Myocd splice variant expression across species.
- To ascertain functional differences among MYOCD isoforms in regulating cardiac and smooth muscle gene expression.
Main Methods:
- Conventional and quantitative RT-PCR were used to analyze Myocd expression.
- Analysis was performed on various tissue types, including aorta, bladder, and heart.
- Functional assays were conducted to assess the impact of MYOCD isoforms on promoter activity.
Main Results:
- Myocd exon 2a (Myocd_v3) is predominantly expressed in smooth muscle-rich tissues, while hearts primarily express a longer Myocd version (Myocd_v1) lacking exon 2a.
- Exclusion of exon 2a is common in cardiac muscle, and exon 10a skipping is rare in both cardiac and smooth muscle.
- Myocd_v1 and Myocd_v2 showed greater activity on cardiac promoters than Myocd_v3 and Myocd_v4, with Myocd_v1 activity enhanced by MEF2C.
Conclusions:
- The study reveals distinct expression patterns and functional activities of major myocardin isoforms across species.
- A new nomenclature is proposed for myocardin isoforms based on their dominant expression in cardiac versus smooth muscle tissues.
- These findings provide insights into the specialized roles of MYOCD isoforms in cardiac and smooth muscle differentiation and function.
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