Immunolocalization of gap junction protein connexin43 (GJA1) in the human retina and optic nerve

PURPOSE Gap junctions are intercellular channels that have been implicated in the pathogenesis of neuronal death after central nervous system injury. This study determines the expression pattern of gap junction protein connexin43 in the human retina and optic nerve. METHODS An affinity-isolated polyclonal antibody to the C-terminal segment of the cytoplasmic domain of human connexin43 was used to determine connexin43 localization. Postmortem human eyes were examined by immunohistochemical staining of frozen sections using antibodies to connexin43. Antibody binding was detected using confocal microscopy and fluorochrome-conjugated secondary antibodies. Double-label immunohistochemistry identified the cell types expressing connexin43. RESULTS Connexin43 immunoreactivity was detected in the human retina on glial fibrillary acidic protein (GFAP)-positive astrocytes in the retinal ganglion cell layer and, to a lesser extent, on the processes of glutamine synthetase-labeled Muller cells. The retinal and choroidal circulations showed strong connexin43 immunolabeling. Dense connexin43 immunoreactivity was present between adjacent cells of the retinal pigment epithelium, and there was diffuse connexin43 immunoreactivity on GFAP-positive astrocytes in the optic nerve. CONCLUSIONS In the human retina and optic nerve, connexin43 is present on glia, blood vessels, and epithelial cells. An understanding of the distribution of connexin43 in the normal retina and optic nerve may be used to evaluate changes associated with retinal and optic nerve disease.