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Synaptic Deficits at Neuromuscular Junctions in Two Mouse Models of Charcot-Marie-Tooth Type 2d.
- Source :
-
The Journal of neuroscience : the official journal of the Society for Neuroscience [J Neurosci] 2016 Mar 16; Vol. 36 (11), pp. 3254-67. - Publication Year :
- 2016
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Abstract
- Patients with Charcot-Marie-Tooth Type 2D (CMT2D), caused by dominant mutations in Glycl tRNA synthetase (GARS), present with progressive weakness, consistently in the hands, but often in the feet also. Electromyography shows denervation, and patients often report that early symptoms include cramps brought on by cold or exertion. Based on reported clinical observations, and studies of mouse models of CMT2D, we sought to determine whether weakened synaptic transmission at the neuromuscular junction (NMJ) is an aspect of CMT2D. Quantal analysis of NMJs in two different mouse models of CMT2D (Gars(P278KY), Gars(C201R)), found synaptic deficits that correlated with disease severity and progressed with age. Results of voltage-clamp studies revealed presynaptic defects characterized by: (1) decreased frequency of spontaneous release without any change in quantal amplitude (miniature endplate current), (2) reduced amplitude of evoked release (endplate current) and quantal content, (3) age-dependent changes in the extent of depression in response to repetitive stimulation, and (4) release failures at some NMJs with high-frequency, long-duration stimulation. Drugs that modify synaptic efficacy were tested to see whether neuromuscular performance improved. The presynaptic action of 3,4 diaminopyridine was not beneficial, whereas postsynaptic-acting physostigmine did improve performance. Smaller mutant NMJs with correspondingly fewer vesicles and partial denervation that eliminates some release sites also contribute to the reduction of release at a proportion of mutant NMJs. Together, these voltage-clamp data suggest that a number of release processes, while essentially intact, likely operate suboptimally at most NMJs of CMT2D mice.<br />Significance Statement: We have uncovered a previously unrecognized aspect of axonal Charcot-Marie-Tooth disease in mouse models of CMT2D. Synaptic dysfunction contributes to impaired neuromuscular performance and disease progression. This suggests that drugs which improve synaptic efficacy at the NMJ could be considered in treating the pathophysiology of CMT2D patients.<br /> (Copyright © 2016 the authors 0270-6474/16/363254-14$15.00/0.)
- Subjects :
- Age Factors
Aminopyridines pharmacology
Animals
Charcot-Marie-Tooth Disease genetics
Charcot-Marie-Tooth Disease physiopathology
Electric Stimulation
Imaging, Three-Dimensional
Mice
Mice, Transgenic
Motor Endplate genetics
Motor Endplate physiopathology
Muscle Strength genetics
Muscle, Skeletal pathology
Muscle, Skeletal ultrastructure
Nerve Tissue Proteins metabolism
Neuromuscular Junction drug effects
Neuromuscular Junction genetics
Neuromuscular Junction metabolism
Patch-Clamp Techniques
Receptors, Cholinergic metabolism
Synaptic Potentials drug effects
Synaptic Potentials genetics
Synaptic Vesicles pathology
Synaptic Vesicles ultrastructure
Charcot-Marie-Tooth Disease pathology
Disease Models, Animal
Glycine-tRNA Ligase genetics
Mutation genetics
Neuromuscular Junction pathology
Synaptic Transmission genetics
Subjects
Details
- Language :
- English
- ISSN :
- 1529-2401
- Volume :
- 36
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- The Journal of neuroscience : the official journal of the Society for Neuroscience
- Publication Type :
- Academic Journal
- Accession number :
- 26985035
- Full Text :
- https://doi.org/10.1523/JNEUROSCI.1762-15.2016