Apoptosis-dependent labeling of phagocytosing glial cells within the retina. A, Typical Müller cells associated with uptake of the fluorescent product at early stages of ganglion cell death (E14). B, Müller cells (arrowhead) and microglial cells (arrow) in the same section at E16. C, D, Ameboid microglial cells appearing within the nerve fiber layer at E16 and viewed in the whole-mounted retina. E, F, Ramified microglial cells in the ganglion cell layer at E16.G, Photograph taken from a nasal retinal whole mount after injection at E10 (before cell death) and examination at E18 (after cell death). Note the regular, typical distribution of microglial cells, which have been labeled after phagocytosis of GCs contributing to the retino-retinal projection. H, Section through the retina at E18 shows microglial cells (arrows) within the GCL and IPL. In all photographed sections OFL is toward the bottom. Scale bars: A–F, 25 μm; G, 50 μm.