Overexpression of GDNF induces and maintains hyperinnervation of muscle fibers and multiple end-plate formation.
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.
Zwick
M
M
Department of Anatomy and Neurobiology, University of Kentucky School of Medicine, 800 Rose Street, Lexington, Kentucky 40536-0298, USA.
Teng
L
L
Mu
X
X
Springer
J E
JE
Davis
B M
BM
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000502:physiology; D004742:Enhancer Elements, Genetic; D005727:Ganglia, Spinal / Q000473:pathology / Q000502:physiology; D051100:Glial Cell Line-Derived Neurotrophic Factor; D006984:Hypertrophy; D007438:Introns; D051379:Mice; D008822:Mice, Transgenic; D009045:Motor Endplate / Q000502:physiology*; D009046:Motor Neurons / Q000166:cytology; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D018994:Myosin Light Chains / Q000235:genetics; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000473:pathology; D011401:Promoter Regions, Genetic
C495040:Gdnf protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D018994:Myosin Light Chains; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D015740:Calcitonin Gene-Related Peptide