This study examined the role of glial cell line-derived neurotrophic factor (GDNF) in synaptic plasticity at the developing neuromuscular junction. Transgenic mice overexpressing GDNF in skeletal muscle under the myosin light chain-1 promoter were isolated. Northern blot and ELISA at 6 weeks of age indicated that GDNF mRNA and protein levels were elevated threefold in the lateral gastrocnemius muscle (LGM) of the GDNF-transgenic animals. Histochemical examination of LGM tissue sections at 6 weeks of age revealed a 70% increase in the number of cholinesterase-positive end plates without changes in end-plate area. Multiple end plates on a single muscle fiber were also observed, in addition to multiple axonal processes terminating on individual end plates. No change in the number of spinal motoneurons, overall LGM size, or muscle type composition was observed. Finally, overexpression of GDNF in muscle caused hypertrophy of neuronal somata in dorsal root ganglia without affecting their number. These findings demonstrate that overexpression of a single neurotrophic factor in skeletal muscle induces multiple end-plate formation and maintains hyperinnervation well beyond the normal developmental period. We suggest that GDNF, a muscle-derived motoneuron neurotrophic factor, serves an important role in the regulation of synaptic plasticity in the developing and adult neuromuscular junction.
|Number of pages
|Published - 2001
Bibliographical noteFunding Information:
This work was supported by Grant NS-30248 from the National Institutes of Health and The University of Kentucky Research Foundation to Joe E. Springer and by Grant NS-31826 from the National Institutes of Health to Brian M. Davis. The authors thank S. Kennedy and M. Green for their excellent technical assistance and Dr. K. Albers for input and assistance in establishing the transgenic lines. We also thank Dr. D. Wright, Dr. M. Werle, Dr. J. Brueckner, and P. Crumrine for helpful comments.
- Glial cell line-derived neurotrophic factor
- Multiple end plates
- Neuromuscular junctions
ASJC Scopus subject areas
- Developmental Neuroscience