| Abstract No.: | A-C1113 |
| Country: | Canada |
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| Title: | THE ROLE OF CRMP4 IN NERVE REGENERATION |
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| Authors/Affiliations: | 1 Stephan Ong Tone*; 1 Yazan Alabed; 2 Adriana Di Polo; 1 Alyson Fournier;
1 Montreal Neurological Institute, QC, Canada; 2 University of Montreal, QC, Canada
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| Content: | Background: The failure of CNS neurons to spontaneously regenerate following injury can be partially attributed to the expression of neurite outgrowth inhibitory myelin associated inhibitors (MAIs). MAIs signal through a tripartite receptor complex to activate the cytosolic protein RhoA and influence cytoskeletal dynamics. RhoA antagonists promote neuronal survival and regeneration in animal models of nerve injury. However, RhoA's potential as a therapeutic target may be limited by its widespread roles in multiple cellular processes and cell types. In an attempt to discover more specific therapeutic targets to promote nerve regeneration, our lab identified the cytosolic phosphoprotein CRMP4b (Collapsin Response Mediator Protein 4b) as a protein that functionally interacts with RhoA to mediate neurite outgrowth inhibition. Blockade of the RhoA-CRMP4b interaction with a competitive peptide (C4RIP) attenuates myelin-dependent neurite outgrowth inhibition.
Objective: To determine the in vivo roles of CRMP4 in nerve regeneration in a rat optic nerve injury model by developing a readily deliverable version of C4RIP.
Materials and Methods: Retinal ganglion cells (RGCs) are retrogradely labeled by the application of FluoroGold to the superior colliculus. RGCs are infected with an adeno-associated virus (AAV) encoding C4RIP. RGC axons are transected by a microcrush lesion (MCL) of the optic nerve. Regenerating axons are anterogradely labeled through an intraocular injection of cholera toxin beta (CTb). Regeneration is quantified 2 weeks post-MCL by the number of CTb positive axons distal to the lesion site. Immunohistochemistry is performed using antibodies raised to CRMP4 and CRMP4b.
Results: We demonstrate that RGCs express endogenous CRMP4b. RGCs are infected with AAV-C4RIP and express C4RIP 2-8 weeks following intraocular injection. AAV-mediated C4RIP expression is observed in the RGC cell bodies and axons. Immunohistochemical staining of the optic nerve reveal CRMP4 positive cells that have yet to be identified.
Conclusion:
Preliminary data show CRMP4 expression in RGCs and other cells located in the optic nerve. Elucidating the role of CRMP4 in nerve regeneration may provide insight into the molecular mechanisms following nervous system injury and lead to the development of more specific therapeutic interventions.
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