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Expression of actin mRNAs in denervated chicken skeletal muscle
N Shimizu1, S Kamel-Reid, R Zak
1Department of Medicine, University of Chicago, Illinois 60637.
Abstract:
The expression of actin genes in chicken pectoralis muscle denervated 1 week after hatching was examined 1-8 weeks after the operation by RNA blot hybridization using a generic actin cDNA probe and DNA probes specific for alpha-skeletal and alpha-cardiac actin genes. Total and alpha-skeletal actin mRNAs/microgram total RNA decreased to about half of the levels found in contralateral control muscle, while the expression of alpha-cardiac actin mRNA was up-regulated. Consequently, alpha-cardiac actin mRNA formed about 15% of the total actin mRNA as compared to less than 1% found in control muscle. The expression of actin genes in the denervated muscle was similar to that in the late embryonic muscle. These results suggest that innervation is required to show the expression pattern of striated muscle actin genes found in mature muscle.
Insights
Innervation is crucial for mature striated muscle actin gene expression. Denervation in chicken pectoralis muscle led to embryonic-like actin gene expression patterns, with reduced alpha-skeletal and increased alpha-cardiac actin mRNA.
Area of Science:
- Molecular Biology
- Developmental Biology
- Muscle Physiology
Background:
- Actin genes are essential for muscle structure and function.
- Striated muscle expresses specific actin isoforms, including alpha-skeletal and alpha-cardiac actin.
- The role of innervation in regulating these actin gene expression patterns is not fully understood.
Purpose of the Study:
- To investigate the impact of denervation on actin gene expression in chicken pectoralis muscle.
- To compare the actin gene expression profile in denervated muscle to that of control and embryonic muscle.
- To determine if innervation is necessary for maintaining mature striated muscle actin gene expression patterns.
Main Methods:
- RNA blot hybridization was employed to analyze actin gene expression.
- Specific DNA probes for alpha-skeletal and alpha-cardiac actin genes were used.
- Expression levels were quantified relative to total RNA and compared between denervated and control muscles.
Main Results:
- Denervation led to a significant decrease in total and alpha-skeletal actin mRNA levels.
- Alpha-cardiac actin mRNA expression was markedly upregulated, constituting about 15% of total actin mRNA.
- The observed actin gene expression pattern in denervated muscle resembled that of late embryonic muscle.
Conclusions:
- Innervation plays a critical role in establishing and maintaining the mature striated muscle actin gene expression profile.
- Denervation disrupts the normal expression pattern, reverting it towards an embryonic state.
- These findings highlight the dependence of differentiated muscle gene expression on neural input.