P-Rex2 is present in rod and cone photoreceptor terminals. A-C: P-Rex2 labeling in the OPL. A: P-Rex2 is expressed in numerous terminals in the distal portion of the OPL. B: VGluT1 is a specific marker for photoreceptor terminals. C: P-Rex2 colocalizes extensively with VGLUT1 in photoreceptor terminals (Overlay). Arrowheads indicate the large terminals of cones; arrows indicate smaller terminals of rods. D-F: Confocal imaging of P-Rex2 and peanut agglutinin (PNA) labeling in the OPL. P-Rex2 is expressed in the terminals of both rod and cone photoreceptors. D: P-Rex2 immunolabeling in photoreceptor terminals in the distal OPL. E: PNA specifically labels flat contacts made by OFF-cone bipolar cells at the base of cone terminals. F: Overlay of panels D and E demonstrates that P-Rex2 labeling is present in the large terminals of cones and smaller rod terminals. Maximum intensity projection of approximately 1.5 μm total thickness shown (5 optical planes at 0.3 μm step size). Nuclei are counterstained with DAPI (blue) in panels A and D to show the position of the ONL and INL. Confocal data are shown as maximum intensity projections of 1–5 optical planes acquired at 0.3 μm step size. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer. Scale bars = 20 μm for A-C; 10 μm for D-F.