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Denervation in murine fast-twitch muscle: short-term physiological changes and temporal expression profiling
Anna Raffaello1, Paolo Laveder, Chiara Romualdi
1Centro di Ricerca Interdipartimentale per le Biotecnologie Innovative Biotechnology Center, University of Padova, Padua, Italy.
Physiological Genomics
|December 29, 2005
Summary
Denervation impacts fast muscles differently than slow muscles. Gene expression studies reveal fast muscle genes decrease while slow muscle genes increase after denervation, challenging previous assumptions.
Area of Science:
- Muscle physiology
- Molecular biology
- Neuroscience
Background:
- Denervation significantly alters muscle structure and function, with distinct effects on slow-twitch versus fast-twitch muscle fibers.
- Previous research on denervation's impact on fast muscles remains controversial, and high-throughput gene expression data is limited.
- Understanding these molecular changes is crucial for developing targeted therapies for muscle atrophy.
Purpose of the Study:
- To investigate gene expression changes during muscle atrophy progression in mouse tibialis anterior (TA) muscle following denervation.
- To compare the responsiveness of fast muscles to neural stimulation interruption at the mRNA level.
- To elucidate the molecular mechanisms underlying denervation-induced muscle atrophy.
Main Methods:
- Sciatic nerve transection in adult CD1 mice, followed by TA muscle dissection at 1, 3, 7, and 14 days post-denervation.
- Gene expression profiling using a dedicated cDNA microarray for muscle genes.
- Validation of microarray results and monitoring of additional gene expression via real-time quantitative PCR (RQ-PCR).
- Physiological assessments including electrophoresis, Western blot, isometric tension of skinned fibers, and functional studies on extensor digitorum longus muscle.
Main Results:
- Seventy-one differentially expressed genes were identified in denervated TA muscles.
- Nuclear- and mitochondrial-encoded genes involved in energy metabolism were consistently downregulated.
- Genes associated with fast-fiber contraction were downregulated, while slow-fiber genes were upregulated.
- Protein expression changes were less pronounced than mRNA level changes, and muscle calcium sensitivity decreased.
Conclusions:
- Fast muscles exhibit significant molecular responses to denervation at the mRNA level, comparable to slow muscles.
- Denervation leads to a downregulation of energy metabolism genes and a shift in muscle fiber-specific gene expression.
- Functional studies indicate altered muscle contractility and calcium sensitivity following denervation.