Animals were deeply anesthetized with CO2 and decapitated. Enucleated eyes were fixed in 4% paraformaldehyde at room temperature for 20 minutes. The expression of GFP in the retina was examined in retinal whole mounts and vertical sections. For the whole mounts, the retina was dissected free in PB solution and flat mounted on slides; GFP fluorescence images were obtained without antibody enhancement. For the vertical sections, the retinas were cryoprotected in a sucrose gradient (10%, 20%, and 30% wt/vol in PB, respectively). Cryostat sections were cut at 16 μm. GFP fluorescence was enhanced by antibody. For immunostaining, retinal vertical sections were blocked for 1 hour in 5% membrane-blocking agent (Chemiblocker; Chemicon, Brica, MA, USA), 0.5% Triton X-100, and 0.05% sodium azide (Sigma Aldrich Corp., St. Louis, MO, USA). The primary antibody, mouse anti-GFP (1:1000; Neuromab, Davis, CA, USA) or rabbit anti-GFP (1:1000; Neuromab), was diluted in the same blocking solution and applied overnight, followed by incubation (1 hour) in the secondary antibody, which was conjugated to Alexa Fluor 488 (1:600, green fluorescence; Thermo Fisher Scientific, Walthem, MA, USA). All images were acquired using a microscope with an attachment (Zeiss Axioplan 2 with ApoTome; Carl Zeiss, Oberkochen, Germany) and software (AxioVision; Carl Zeiss). Image projections were constructed by collapsing individual Z-stacks of optical sections onto a single plane using software (ZEN; Carl Zeiss).