Stem cell niches in zebrafish retina. The germinal zone at the boundary between neural retina and ciliary epithelium (CE) is a circumferential wedge of neuroepithelial cells (in red) called the ciliary marginal zone (CMZ). Multipotent retinal stem cells span the width of the retinal epithelium adjacent to the CE and more restricted retina progenitors give rise sequentially to 1) retinal ganglion cells (GC), 2) amacrine cells (AC), 3) bipolar (BP) and horizontal cells (HC), and 4) cone photoreceptors. The CMZ is separated from the retinal pigmented epithelium (RPE) by a narrow subretinal space. The ora collection blood vessel (BV) encircles the retina at the CMZ; other blood vessels of the hyaloid circulation lie along the vitreal surface. Müller glia (blue) span the width of the retina and create a niche that supports retinal progenitors of the last-born retinal neuron in the 5) rod photoreceptor lineage (green). Expression of specific markers is shown for retinal progenitors/stem cells and associated cell types. Retinal injury induces a reorganization of the Müller cell/rod lineage niche to produce a regeneration niche (purple) that mirrors the CMZ niche in patterns of cellular organization and gene expression.