Investigating ectopic opsin-based gene therapies to restore pattern forming vision in blind mice

• Applicant: Dr. Moritz Lindner
• Subject Area: Ophthalmology ; Anatomy and Physiology
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 315649894

Late-stage age related Macular Degeneration (AMD) and inherited retinal diseases (IRD) commonly lead to irreversible photoreceptor loss. AMD is the leading cause of legal blindness in the elderly and even if each particular IRD is rare, all together they affect 1 in 3000 humans worldwide. Current therapeutic approaches for degenerative retinal diseases only aim to slow down or halt disease progression, not to reverse it. In addition they all depend on the biology underlying the degenerative process and are therefore mostly disease specific.A common hallmark of most of these degenerative retinal disorders is that the inner retina remains unaffected. Experimental approaches have been taken to restore visual function by inducing light sensitivity to cells of the inner retina through ectopic expression of opsin proteins. This approach is attractive as it could function independently of the underlying disease cause and it may achieve much higher spatial resolution and a greater visual field than the alternative retinal implant technology. However, it remains unclear to what extend encoding of complex light stimuli can be obtained by ectopic expression of opsins. The lack of knowledge in this field is mainly caused by the fact that methods monitoring responses to complex light stimuli with sufficient resolution are missing. This program aims to investigate if opsin based gene therapy is capable of restoring complex image forming vision in photoreceptor deficient mice by applying novel electrophysiological, live-cell imaging and behavioral approaches.We will establish multi-electrode arrays and genetically encoded calcium sensors as tools to record electrical responses elicited by a range of pattern stimulus paradigms from explanted retinae. In addition we will optimize existing behavioral tests to assess pattern recognition in mice. The main challenge will be to reach maximal spatiotemporal resolution that enables analyzing the response also of the most complex light stimuli. We will first apply these methodological approaches to identify the optimal target cell population for opsin based gene therapy by selectively delivering a fast, light sensitive cation channel to either cell population. Due to non-physiologic stimuli responses and high immunogenicity such a cation channel would not be suitable for gene therapeutic use. Therefore we will test the light-sensitive protein melanopsin and currently developed fast-switching melanopsin variants and analyze their capacity to restore pattern forming vision in blind mice. Melanopsin is a retina-resident protein activating pathways physiologically involved in the transduction of light responses. Thereby a close-to-native response to light on cellular level should be obtained and the risk of immunoreactions can be minimized.This study will determine the future potential of opsin based gene therapy to restore visual function and will provide essential knowledge necessary to port this approach into clinics.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Mark Hankins, Ph.D.