ATF3 and Intermediate Filament Expression After Optic Nerve Injury (ONI) in Zebrafish

Abstract

The role of astrocytes during optic nerve regeneration after ONI in zebrafish is not well characterized. Activating transcription factor 3 (ATF3) is a member of the transcription factor family ATF/CREB, and has been shown upregulated during optic nerve regeneration by Saul et al., 2009 (in press). Previous work by García et al., (2005, Cell Tissue Res., 322(2), 245–56) has shown that astrocytes of zebrafish express cytokeratins rather than the expected GFAP. We examined ATF3 and cytokeratin‐18 expression in the retina and optic nerve by immunofluorescence (IMF) in AB and gfap::GFP zebrafish after ONI. ATF3 expression was elevated in the ONI retina compared to the contralateral retina (CR) after 24 hours. ATF3 expression was significantly elevated in retinal ganglion cell cytoplasm and nuclei and in the cytoplasm and nuclei of cells resembling astrocytes in the optic nerve after 24 and 72 hours. GFP expression was only observed in the Müller glial cells in the retina in both ONI and CR. No GFP expression was observed in any of the optic nerves. Immunolabeling with anti cytokeratin‐18 revealed numerous cells staining positive for cytokeratins in the optic nerve and retina of ONI and uninjured nerves and retinas. This study was supported by NSF grants IOB‐0615762 to DMG and DBI‐0821252 to JRK and DMG.