Pigmentation and regeneration of the zebrafish retinal pigment epithelium
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The Retinal Pigment Epithelium (RPE) is a specialized monolayer of pigmented cells in the back of the eye that forms a functional unit with photoreceptor cells in the retina and is critical for photoreceptor function and eye development. As a flat sheet of progenitor cells develops, a series of complex morphogenetic changes occur which require coordinated changes in cellular morphology, cell cycle and motility. To aid the study of these processes, I have generated ten novel GAL4-inducible zebrafish transgenics that enable the tissue-specific modulation of Rho GTPase activity and demonstrated the utility of these lines in studying eye development. Diseases disrupting the normal pigmentation of the RPE, known as albinism, cause defects in retinal development and vision. Although many different alleles of albinism have been identified, it is likely that undiscovered loci responsible for causing albinism exist. To learn more about the genetic underpinnings of albinism, I have characterized two novel zebrafish albino mutants and found they result from mutations in the gene encoding N ethyl maleimide-sensitive factor B (nsfb) and have established a role for nsfb in the maturation of pigment in zebrafish RPE. Finally, diseases affecting the adult RPE have dire consequences for vision. Geographic Age-related Macular Degeneration (AMD) is the third leading cause of blindness worldwide, and occurs when atrophy of the RPE causes irreversible death of underlying photoreceptors. Despite advances in stem-cell based RPE replacement therapies, very little is known about the process by which RPE cells can successfully regenerate and integrate into damaged retinal tissue. To study this process, I established a novel zebrafish model of AMD whereby specific ablation of the RPE leads to rapid degeneration of underlying photoreceptors. Using this model, I demonstrated for the first time that the zebrafish RPE is capable of regenerating after widespread damage and provide evidence that RPE ablation provokes a robust proliferative response during which cells from the periphery move into the injury site and contribute to regeneration, and that these cells likely derive from unablated RPE. This model provides a platform for supporting the development of AMD therapies.