Abstract
Abstract: :
Purpose: Determine if developmental mechanisms of cytogenesis are recapitulated during growth and regeneration of an adult vertebrate retina. Methods: Mechanical lesions of dorsal retina in the right eyes of post–metamorphic winter flounder (Pleuronectes americanus) were performed; left eyes were controls. Animals were euthanized 26, 27, or 60 days following lesion, and the retinas processed for in situ hybridization or indirect immunohistochemical analysis. The rod opsin from post–metamorphic retina was cloned and fully sequenced, and digoxigenin–labeled cRNA probes were prepared. Rods and cones were also labeled selectively with antibodies (zpr3 and zpr1, respectively; U. Oregon Monoclonal Antibody Facility). In all retinas the spatial location of rods and cones was measured relative to the circumferential germinal zone (CGZ), and in lesioned retinas relative to, or across, the lesion site. Results: A statistically significant, differential spatial distribution of rods and cones was observed at the retinal margin, with zpr1–positive cones always located closer to the CGZ than zpr3–positive rods (n = 19 measurements; paired t–test p < 0.001). A similar, differential spatial distribution was observed proximal to retinal lesion sites, with zpr1–positive cones always located closer to the lesion site than zpr3–positive rods (n = 19; p < 0.04). Relative to zpr1–positive cones, the spatial distribution of zpr3–positive rods was not significantly different than rods labeled with a cRNA probe against rhodopsin (n = 7; p = 0.40). Conclusion: During post–metamorphic retinal growth and regeneration there is a temporal progression of photoreceptor production (cones, then rods). This trajectory of photoreceptor production, which is similar to that observed during development of the flounder retina, supports the hypothesis that the mechanisms that control temporal aspects of cytogenesis in the developing flounder retina are recapitulated during growth and regeneration of the adult retina.
Keywords: regeneration • retinal development • photoreceptors