FIGURE 1

FIGURE 1

Structure of the zebrafish eye and retina. (A) Anatomy of the zebrafish eye: DIC image of a cryosection from a 6 days post-fertilization (6 dpf) larval eye highlighting the main structures of the vertebrate eye including cornea, lens, retina, and retinal pigment epithelium (RPE). (B) The larval retina is organized into highly structured layers: Overlay of a DIC image and the fluorescent nuclear marker DAPI of a cryosection from a 6 dpf larva showing the different retinal layers, including the outer nuclear layer (ONL) which contains the cell bodies of photoreceptors (rods and cones). Photoreceptors make synapses in the outer plexiform layer (OPL) with bipolar and horizontal cells. The inner nuclear layer (INL) contains the cell bodies of horizontal, bipolar and amacrine cells, while the ganglion cell layer (GCL) contains the cell bodies of retinal ganglion cells (RGC). Bipolar cells provide excitatory synaptic input to RGC in the inner plexiform layer (IPL), while amacrine cells modulate this input both pre- and post-synaptically. (C) The adult retina retains the same layered structure: Overlay of a DIC image and DAPI of a cryosection from an adult zebrafish. (D) The zebrafish retina contains 4 subtypes of cones: DIC image of a cryosection from an adult zebrafish showing the short-single or ultraviolet-wavelength sensitive cones (UV-cones), the long-single or short-wavelength sensitive cones (S-cones), and the double cones which correspond to the middle- and long-wavelength sensitive cones (M- and L-cones). (E) Mosaic arrangement of zebrafish cone photoreceptors: Confocal image of a whole-mounted retina of a double-reporter transgenic lines to identify UV-cones [Tg(sws1:GFP)^kj9, magenta] and S-cones [tg(sws2:mCherry)^ua3011, blue] overlayed with DAPI (gray), allowing the identification of the nuclei of M- and L-cones between the rows of UV- and S-cones. (F) Diagram of the vertebrate retina and the retinal cells. Inset highlights the synapse between cones and horizontal and bipolar cells, where the cone synaptic terminal contains synaptic vesicles (white) attached to the synaptic ribbon (black). In close apposition to the ribbon, the dendrites on On-bipolar cells (On-BCs) invaginate into the synaptic terminal and are flanked by two horizontal cell (HC) processes. Off-bipolar cells make more basal contacts in close proximity but not apposed to the synaptic ribbon.