Abstract
Purpose::
Axons of adult mammalian central nervous system usually do not regenerate after injury. However, there is an abortive regeneration when axons of retinal ganglion cells (RGC) are damaged. It suggests RGC may have limited ability to regenerate axons but fail eventually. To find out the factors that may augment neuronal regeneration, we had previously adopted subtractive hybridization method to search for genes whose expression is up-regulated after optic nerve injury. One DNA fragment, temporarily named as 9a8, was identified in this analysis and verified by semi-quantitative RT-PCR to be a gene whose expression increases after optic nerve injury.
Methods::
We cloned the full-length cDNA of 9a8 gene, and generated a polyclonal antiserum against 9a8 fusion protein. Northern blot analysis and immunohistochemistry were performed to examine the expression of this gene. With 9a8 plasmid transfection into Neuro-2a and IMR32 cell lines, we try to explore the function of this novel protein.
Results::
9a8 gene encodes 570 amino acids and contains a FERM domain at its N-terminus. Northern blot showed that it is expressed in retina, brain, and heart of adult mice. In the retina, 9a8 proteins were detected in RGC layer, outer plexiform layer, inner segment of photoreceptor, and retinal pigment epithelium. With immunohistochemistry, its expression is up-regulated after optic nerve injury. Upon induction of neurite outgrowth in Neuro-2a and IMR32 cell lines by retinoid acid, over-expression of 9a8 proteins inhibits neurite outgrowth in these neuronal cells.
Conclusions::
We found a novel FERM-domain containing gene which inhibits neurite outgrowth in the Neuro-2a and IMR32 cell lines.
Keywords: regeneration • optic nerve • ganglion cells