P.H.C. and C.K.F. contributed equally to this work.
Neural cell adhesion molecule is required for stability of reinnervated neuromuscular junctions
Article first published online: 13 JAN 2010
© The Authors (2010). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 31, Issue 2, pages 238–249, January 2010
How to Cite
Chipman, P. H., Franz, C. K., Nelson, A., Schachner, M. and Rafuse, V. F. (2010), Neural cell adhesion molecule is required for stability of reinnervated neuromuscular junctions. European Journal of Neuroscience, 31: 238–249. doi: 10.1111/j.1460-9568.2009.07049.x
- Issue published online: 18 JAN 2010
- Article first published online: 13 JAN 2010
- Received 1 September 2009, revised 28 October 2009, accepted 10 November 2009
- neural cell adhesion molecule;
- neuromuscular junction;
Studies examining the etiology of motoneuron diseases usually focus on motoneuron death as the defining pathophysiology of the disease. However, impaired neuromuscular transmission and synapse withdrawal often precede cell death, raising the possibility that abnormalities in synaptic function contribute to disease onset. Although little is known about the mechanisms maintaining the synaptic integrity of neuromuscular junctions (NMJs), Drosophila studies suggest that Fasciclin II plays an important role. Inspired by these studies we used a reinnervation model of synaptogenesis to analyze neuromuscular function in mice lacking neural cell adhesion molecule (NCAM), the Fasciclin II vertebrate homolog. Our results showed that the recovery of contractile force was the same in wild-type and NCAM−/− mice at 1 month after nerve injury, indicating that endplates were appropriately reformed. This normality was only transient because the contractile force and myofiber number decreased at 3 months after injury in NCAM−/− mice. Both declined further 3 months later. Myofibers degenerated, not because motoneurons died but because synapses were withdrawn. Although neurotransmission was initially normal at reinnervated NCAM−/− NMJs, it was significantly compromised 3 months later. Interestingly, the selective ablation of NCAM from motoneurons, or muscle fibers, did not mimic the deficits observed in reinnervated NCAM−/− mice. Taken together, these results indicate that NCAM is required to maintain normal synaptic function at reinnervated NMJs, although its loss pre-synaptically or post-synaptically is not sufficient to induce synaptic destabilization. Consideration is given to the role of NCAM in terminal Schwann cells for maintaining synaptic integrity and how NCAM dysfunction may contribute to motoneuron disorders.