Collapsin response mediator protein-2 accelerates axon regeneration of nerve-injured motor neurons of rat

The rat collapsin response mediator protein-2 (CRMP-2) is a member of CRMP family (CRMP-1-5). The functional consequence of CRMP-2 during embryonic development, particularly in neurite elongation, is relatively understood; however, the role in nerve regeneration is unclear. Here we examined the role of CRMP-2 during nerve regeneration using rat hypoglossal nerve injury model. Among the members, CRMP-1, CRMP-2, CRMP-5 mRNA expressions increased after nerve injury, whereas CRMP-3 and CRMP-4 mRNA did not show any significant change. In the N1E-115 cells, CRMP-2 has the most potent neurite elongation activity among the CRMP family members. In dorsal root ganglion (DRG) organ culture, CRMP-2 overexpression by adenoviral vector demonstrated substantial neurite elongation. On the other hand, CRMP-2 (DeltaC381), which acts as a dominant negative form of CRMP-2, inhibited neurite formation. Collectively, it would be plausible that CRMP-2 has potent nerve regeneration activity after nerve injury. We therefore examined whether CRMP-2 overexpression in the injured hypoglossal motor neurons accelerates nerve regeneration. A retrograde-tracer, Fluoro-Gold (FG), was used to evaluate the number of reprojecting motor neurons after nerve injury. CRMP-2-overexpressing motor neurons demonstrated the accelerated reprojection. The present study suggests that CRMP-2 has potent neurite elongation activity in nerve regeneration in vivo.