title: Ectopic photoreceptors and cone bipolar cells in the developing and mature retina.
abstract: An antibody against recoverin, the calcium-binding protein, labels photoreceptors, cone bipolar cells, and a subpopulation of cells in the ganglion cell layer. In the present study, we sought to establish the origin and identity of the cells expressing recoverin in the ganglion cell layer of the rat retina. By double labeling with rhodopsin, we demonstrate that early in development some of the recoverin-positive cells in the ganglion cell layer are photoreceptors. During the first postnatal week, these rhodopsin-positive cells are eliminated from the ganglion cell layer, but such neurons remain in the inner nuclear layer well into the first postnatal month. Another contingent of recoverin-positive cells, with morphological features equivalent to those of bipolar cells, is present in the postnatal retina, and approximately 50% of these neurons survive to maturity. The incidence of such cells in the ganglion cell layer was not affected by early transection of the optic nerve, a manipulation that causes rapid loss of retinal ganglion cells. These recoverin-positive cells were not double-labeled by cell-specific markers expressed by photoreceptors, rod bipolar cells, or horizontal and amacrine cells. Based on their staining with recoverin and salient morphological features, these ectopic profiles in the ganglion cell layer are most likely cone bipolar cells. Collectively, the results provide evidence for photoreceptors in the ganglion cell and inner nuclear layers of the developing retina, and a more permanent subpopulation of cone bipolar cells displaced to the ganglion cell layer.
authors.affiliation: Section of Neurobiology, Physiology, and Behavior, Division of Biological Sciences, School of Medicine, University of California, Davis, California 95616, USA.
authors.forename: Emine
authors.initials: E
authors.lastname: Günhan
authors.forename: Deborah
authors.initials: D
authors.lastname: van der List
authors.forename: Leo M
authors.initials: LM
authors.lastname: Chalupa
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000032:analysis; D005136:Eye Proteins; D051597:Hippocalcin; D007150:Immunohistochemistry; D008074:Lipoproteins; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins; D020419:Photoreceptor Cells, Vertebrate / Q000737:chemistry / Q000166:cytology*; D051381:Rats; D020318:Rats, Long-Evans; D051603:Recoverin; D012160:Retina / Q000196:embryology* / Q000254:growth & development*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D012165:Retinal Ganglion Cells / Q000737:chemistry / Q000166:cytology*; D012243:Rhodopsin / Q000032:analysis
chemical_list: D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; C496733:Rcvrn protein, rat; D051603:Recoverin; D051597:Hippocalcin; D012243:Rhodopsin