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Biochemical changes in progressive muscular dystrophy. XIV. Skeletal muscle myosin mRNA translatability in dystrophic
U S Srivastava1, E A Sugden, P K Majumdar
1Department of Nutrition, University of Montreal, Que., Canada.
Abstract:
Variations in the content and translatability of the poly(A)+ RNA and mRNA molecules coding for myosin (M) were studied in the hind leg muscles of genetically dystrophic mice. The poly(A)+ RNA content of total skeletal muscle failed to increase normally during progression of the disease. M mRNA, isolated from dystrophic normally during progression of the disease. M mRNA, isolated from dystrophic murine muscle poly(A)+ RNA, was mostly found to be associated with the 26S RNA species. The translation of M mRNA in an in vitro heterologous wheat germ system was lower at 8 and 16 weeks in the dystrophic group as compared with the controls. Analysis of the translation products via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, autoradiography, and densitometric autoradiographic tracing demonstrated the gradual disappearance of a protein band corresponding to M, the major component of skeletal muscle. cDNA was synthesized, using M mRNA that was isolated and purified from normal and dystrophic mouse muscle as a template. Total radioactivity was measured in some cDNA fractions produced from normal and dystrophic mouse muscle, while other fractions were utilized for separation and sizing of cDNA by disc gel electrophoresis. The cDNA from normal muscle was hybridized with M mRNA from normal and 16-week-old dystrophic mouse muscles. The cDNA probe, hybridization experiments, and studies involving the content and synthesis of M mRNA suggest that murine muscular dystrophy elicited a shorter species of mRNA or shorter sequences of the same species of mRNA coding for M. Not all poly(A)+ mRNA sequences coding for M, found in control mice, were present in their dystrophic counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Duchenne muscular dystrophy in mice alters myosin mRNA, leading to shorter or missing sequences. This impacts myosin protein production, contributing to muscle degeneration in the disease.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Skeletal muscle myosin (M) is crucial for muscle function.
- Genetic muscular dystrophies involve progressive muscle degeneration.
- Understanding molecular changes in dystrophic muscle is key to disease mechanisms.
Purpose of the Study:
- To investigate variations in myosin (M) mRNA content and translatability in dystrophic mouse hind leg muscles.
- To determine if dystrophic changes affect M mRNA processing or stability.
- To identify molecular alterations underlying myosin deficiency in muscular dystrophy.
Main Methods:
- Quantification of poly(A)+ RNA and M mRNA in normal and dystrophic mouse muscle.
- In vitro translation of M mRNA using a wheat germ system.
- Analysis of translation products by SDS-PAGE and autoradiography.
- cDNA synthesis from M mRNA and hybridization studies.
Main Results:
- Poly(A)+ RNA content in dystrophic muscle failed to increase normally.
- In vitro translation of M mRNA was reduced in dystrophic mice.
- Analysis revealed a gradual decrease in myosin protein.
- Dystrophic M mRNA may be shorter or have truncated sequences compared to normal.
Conclusions:
- Murine muscular dystrophy is associated with altered M mRNA, potentially shorter species or sequences.
- Reduced M mRNA translatability and myosin protein levels contribute to muscle pathology.
- Not all myosin-coding mRNA sequences found in control mice are present in dystrophic counterparts.