Abstract
Abstract: :
Purpose: To determine whether the P23H mutation in rhodopsin is capable of inducing photoreceptor degeneration in the Xenopus laevis retina. Methods: Xenopus laevis rod opsin cDNA was mutated using site–directed mutagenesis, cloned downstream of Xenopus laevis rod opsin promoter, and confirmed by sequencing. Egg–microinjection technique was used to generate transgenic Xenopus laevis, the tadpoles and frogs were genotyped. The retinas of transgenic tadpoles and frogs were subject to histological and immunohistochemical examination. TUNEL assay was performed to identify apoptosis. Results: In transgenic Xenopus expressing P23H mutant rhodopsin, the transgenic rhodopsin forms aggregates. Retina degeneration was identified by 6 days post–fertilization tadpoles with shortened rod outer segments. By the age of four weeks, some transgenic animals have lost almost all rod photoreceptors, but still have many cone photoreceptors. TUNEL staining suggests that the rod photoreceptors may die by apoptosis. Conclusions: P23H rhodopsin mutation, the most frequent mutation in human retinitis pigmentosa, induced retina degneration in the Xenopus retina. The results suggests that the pathological process of retina degeneration is conserved from Xenopus laevis to human. With respect to highly efficient, time– and cost–saving transgenic approaches, Xenopus may be a powerful model of retina degeneration. Because there are nearly equal numbers of cone and rod photoreceptors in retina, Xenopus may be used to study not only rod but also cone photoreceptors degeneration and the interaction of the two pathological processes.
Keywords: retinal degenerations: hereditary • transgenics/knock–outs • cell death/apoptosis