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UBC Theses and Dissertations

Controlled ablation of rod photoreceptors in transgenic Xenopus laevis Hamm, Lisa


Retinal degeneration is the progressive loss of neurons lining the posterior surface of the eye. Loss of a certain group of neurons called rod photoreceptors can occur as the result of genetic mutation. In humans, and in mammalian models of retinal degeneration, the death of these cells is permanent, and often followed by cone photoreceptor death, which leads to blindness. As a step towards understanding the implications of rod cell death in the retina, we generated transgenic X. laevis that expressed a novel form of caspase-9, with binding domains specific to the compound AP20187. We treated these transgenic animals with AP20187 and caused rod cell death by apoptosis in tadpoles and post metamorphic animals. Peak rod apoptosis occurred two days after drug exposure. We adapted an electroretinography apparatus, and protocols designed for mammals to measure functional changes in X. laevis rod and cone derived responses. We observed delayed secondary cone cell dysfunction after induced rod cell apoptosis, which was subsequently restored. These animals provide a simple and clinically relevant model of diseases like Retinitis pigmentosa, in which we will be able to probe in detail the mechanisms that govern cone cell dysfunction as a consequence of rod apoptosis. The unique ability of this species to recover from this insult will provide clues towards initiating similar recovery in humans.

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