Abstract
Unlike the mammalian CNS, the fish optic nerve can regenerate their axons after optic nerve transection. TGR, one type of transglutaminase that derived from regenerating goldfish retina, was upregulated after optic nerve injury. We have isolated a cDNA clone for TGR that comprised of 678 amino acids. In situ hybridization and immunohistochemical study showed that the increase of TGR expression was limited to be only in the ganglion cells. The TGR enzyme activity and mRNA content were peaked at 20 days after optic nerve transection. In contrast to goldfish, the expression of TG of rat disappeared for 1 week from ganglion cells after optic nerve crush. To investigate the molecular mechanism of TGR in the optic nerve regeneration, we made recombinant TGR protein with the expression vector pFLAG-CMV-1 transfected in HEK 293 cellsUsing an in vitro culture system, addition of the recombinant TGR protein lead to promotion of neurite outgrowth from early stage of culture. Furthermore, an in vivo assay system of retinotectal connection traced with WGA-HRP was clearly blocked by daily treatment of TG inhibitors into goldfish orbit for 30 days. These results indicate that upregulation of TGR is an indispensable event for regrowing the optic nerve fibres in vitro and in vivo. We are now in progress to investigate the effect of blocking TGR expression with RNAi on neurite outgrowth. [Jpn J Physiol 54 Suppl:S214 (2004)]
