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Reduction of postjunctional fold density and depth in dystrophic mice
J P Tremblay1, L Grégoire, R Sasseville
1Department of Anatomy, Laval University, Quebec, Canada.
Synapse (New York, N.Y.)
|January 1, 1988
Summary
Duchenne muscular dystrophy (DMD) in mice significantly alters neuromuscular junctions (NMJs), reducing postjunctional membrane length and fold depth. These changes occur even in seemingly normal muscle fibers, highlighting early NMJ pathology in muscular dystrophy.
Area of Science:
- Neuroscience
- Muscle Biology
- Genetics
Background:
- Duchenne muscular dystrophy (DMD) is a severe genetic disorder characterized by progressive muscle degeneration.
- Neuromuscular junctions (NMJs) are critical for muscle function, and their integrity is often compromised in muscular dystrophies.
Purpose of the Study:
- To investigate the morphometric changes at the neuromuscular junction in dystrophic mice (C57BL/6J dy2J/dy2J) compared to normal controls.
- To assess the impact of the dystrophic mutation on the structure of postjunctional folds and membrane at the NMJ.
Main Methods:
- Electron microscopy was used to examine neuromuscular junction profiles in gastrocnemius muscles of normal, heterozygous, and homozygous dystrophic mice.
- Morphometric analysis quantified the number of secondary postjunctional folds, the length of the postsynaptic membrane, and the depth of secondary folds.
Main Results:
- Dystrophic animals showed a reduced number of secondary postjunctional folds per unit length of synaptic cleft compared to normal animals.
- The normalized length of the postsynaptic membrane was significantly reduced by 45% in dystrophic mice relative to normal mice.
- The depth of secondary folds was also significantly reduced in dystrophic mice, affecting both fast and slow twitch fibers.
Conclusions:
- Duchenne muscular dystrophy leads to significant morphometric alterations of the postsynaptic membrane at the neuromuscular junction.
- These structural deficits at the NMJ can be present even in muscle fibers that appear morphologically normal, suggesting early pathological changes.