Related Experiment Videos
Myomesin and M protein: differential expression in embryonic fibers during pectoral muscle development
Abstract:
By applying immunocytochemistry using monoclonal antibodies, we found that the myofibrillar M band of both presumptive type-I and -II fibers in the pectoralis major muscle of chickens contains two high-molecular-weight proteins, i.e., myomesin (Mr, 185,000) and M protein (Mr, 165,000), early in embryonic development (7 days in ovo), even though adult type-I fibers lack M protein. The developmental expression of M protein is unusual in that, from 10 to 14 days in ovo, it is gradually suppressed not only in presumptive type-I fibers but also in presumptive type-II fibers formed from primary-generation myotubes. This latter suppression is transient, as M protein is expressed in all adult type-II fibers derived from both the primary- and second-generation myotubes. Myomesin, on the other hand, is continuously expressed in all myotubes throughout development. This finding shows that myomesin and M protein expression is regulated independently in different myotube populations, and that the suppression of M protein in primary-generation myotubes accounts for the delayed accumulation of M protein during development, as previously revealed by biochemical analysis. Presumptive type-I fibers, which form in the deep portion of the muscle, become concentrated in a narrow band known as the red strip.
Insights
Myomesin and M protein are found in chicken muscle fibers early in development. M protein expression is transiently suppressed in some fibers, indicating independent regulation of these muscle proteins during development.
Area of Science:
- Muscle biology
- Developmental biology
- Protein biochemistry
Background:
- The myofibrillar M band is crucial for muscle structure and function.
- Understanding the developmental expression of M band proteins is key to understanding muscle differentiation.
- Myomesin and M protein are high-molecular-weight components of the M band.
Purpose of the Study:
- To investigate the developmental expression patterns of myomesin and M protein in chicken pectoralis major muscle.
- To determine if the expression of myomesin and M protein is regulated independently.
- To correlate protein expression with fiber type development.
Main Methods:
- Immunocytochemistry using monoclonal antibodies was employed.
- Analysis focused on the pectoralis major muscle of chickens at various embryonic stages (from 7 days in ovo).
- Distinction was made between presumptive type-I and type-II muscle fibers.
Main Results:
- Both myomesin and M protein were detected in presumptive type-I and -II fibers at 7 days in ovo.
- M protein expression was transiently suppressed in both fiber types between 10-14 days in ovo.
- Myomesin showed continuous expression throughout embryonic development, while M protein reappeared in adult type-II fibers.
Conclusions:
- Myomesin and M protein expression are independently regulated in different myotube populations.
- The transient suppression of M protein explains its delayed accumulation observed in previous biochemical studies.
- These findings provide insights into the molecular mechanisms governing muscle fiber type differentiation.