Figure 3. Immunofluorescence staining of cryosections from 6 day control explants. As seen in confocal images of cryostat sections, antibodies against glial fibrillary acidic protein (GFAP; red) identified glial intermediate filaments (IF), and antibodies against cellular retinaldehyde-binding protein (CRALBP; green) identified a retinoid-binding protein present in Müller cells. CRALBP labeling was more concentrated at the neuroretinal outer layers. Colocalization of both antibodies (yellow) marked Müller cells GFAP+. In control explants, only some Müller cells showed GFAP expression in the cytoplasm that reached the outer limiting membrane (OLM; arrows). Astrocyte cell bodies and GFAP+ extensions were located along the nerve fiber layer (NFL; arrowheads). Scale bar equals 20 µm. Abbreviations: ganglion cell layer (GCL); inner limiting membrane (ILM); inner nuclear layer (INL); outer nuclear layer (ONL).