Developing Cone-Dominant Retinal Disease Models as a Resource for Translational Vision Research

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PROJECT SUMMARY/ABSTRACT . The NEI’s Audacious Goal Initiative (launched in 2012) put forward the challenge of “restoring usable vision in humans by regenerating neurons and neural connections in the eye and visual system.” While there is an obvious affinity towards novel therapies, current resource and technology gaps preclude translation of many therapeutic approaches. One such gap pertains to the availability of animal models that share key features of human retinal anatomy, as well as disease models that faithfully emulate the mechanisms and processes seen in patients with retinal degenerations (blinding diseases that might be amenable to regenerative therapies). The absence of readily available cone-dominant mammalian models represents a major technology gap impeding efforts to develop and evaluate regenerative treatment strategies in the retina. We propose to advance two promising model systems that are closer to human visual anatomy and function than the more widely used mouse and rat models. The first is the 13-lined ground squirrel (13-LGS): a diurnal, cone-dominant rodent (~85% cones) with large brain regions dedicated to processing visual information. The second is the tree shrew: a non- rodent, primate-like mammal that is also cone dominant (~95% cones). These models have been used to study visual transduction (13-LGS), outer segment morphogenesis, shedding, and remodeling during hibernation (13- LGS), cone-bipolar cell circuitry (13-LGS), myopia (tree shrew) and central visual processing (tree shrew). However, their use as translation-enabling models for evaluating both survival and integration of regenerated cone photoreceptors has been limited; mainly due to a lack of tools that allow for genetic manipulation of these animals (and thus a dearth of disease models). We propose to advance these species as disease-relevant models through the following Specific Aims: (1) Develop, optimize, and validate imaging methods and functional assays for the 13-LGS and tree shrew; (2) Generate 13-LGS and tree shrew cone photoreceptors from iPSCs in vitro; (3) Create rAAV-mediated retinal degeneration models for the 13-LGS and tree shrew in vivo; (4) Enable germline transgenic 13-LGS models of human disease; (5) Test and optimize integration of transplanted 13- LGS, tree shrew, and human iPSC-derived cones in normal and degenerated 13-LGS and tree shrew retinas. A key feature of this proposal is the validation of these models by comparing their cellular-resolution phenotype with that seen in patients with similar conditions/mutations. Throughout the project, we will share and disseminate our protocols, methods, and data to provide resources for use by the broader vision research community; this will be done using existing and newly-created online tools. A major strength of this application is the multidisciplinary team that has been assembled to take on this challenging project. The team brings the necessary complementary expertise required for model development, stem cell treatment, and evaluation of cell survival, integration, & function. This work will have a significant positive impact by providing not only validated disease models but also generalizable tools with which to create additional models in these and other species.