Abstract
Fish CNS neurons can repair their axons following nerve injury, while mammalian CNS neurons lose this capacity. After fish optic nerve transection, the regenerating optic axons can reinnervate the tectum by 3-5 weeks. We have investigated these regeneration mechanisms using goldfish and zebrafish visual system. Galectin is a family of carbohydrate-binding protein with an affinity for β-galactoside. It's noted that galectins mediate various biological functions such as cell-cell interactions, inflammation and cell adhesion by cross-linking of carbohydrate residues. In the present study, we examined expression of two members of galectins, galectin-1 and galectin-3 in adult fish retina during optic nerve regeneration. The level of galectins protein rapidly decreased within a few days, but thereafter increased by 10-20 days and returned to the control level by 30 days after optic nerve lesion. Analysis by RT-PCR and in situ hybridization revealed that level of galectin mRNAs started to increase within a few days, peaked at day 5-10, and then gradually decreased by day 30 after optic nerve transection. To elucidate molecular involvement of galectins, we estimated the effect of recombinant galectin protein on neurite outgrowth in retinal explant culture system. Recombinant galectin protein clearly induced neurite outgrowth from adult fish retinal explants. These data suggest that upregulation of galectins (galectin-1 and galectin-3) is an important event for regeneration of the optic axons. [J Physiol Sci. 2008;58 Suppl:S112]
