Project Details
Projekt
Re-engineering melanopsin as a tool for optogenetic vision restoration
Applicant
Dr. Moritz Lindner
Subject Area
Ophthalmology
Anatomy and Physiology
Anatomy and Physiology
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 498238833
Background: Degenerative retinal disorders are a common cause of blindness and lead to irreversible photoreceptor death. In optogenetic gene therapy exogenous light sensitive proteins (opsins) are expressed in surviving cells of the retina (e.g. in bipolar cells) to allow them to substitute the function of the lost photoreceptors. While laboratory research is ongoing, functional data from a first patient treated in a clinical trial have recently been published. While data are promising, the level of vision restored is extremely low.Though the reasons for the limited functional outcome observed are unknown, one possible reason is that the opsin used is not ideally suited as tools for vision restoration. In this and all ongoing trials opsins of microbial origin have been used. However, these represent only one of the two main classes of optogenetic tools: the other being G-protein coupled receptor opsins of mammalian origin.Arguments against or in favour of microbial opsins are being pushed forward since the early days of optogenetic gene therapy and various mammalian opsins have been tested as tools for vision restoration. There is no consensus on which vertebrate opsin could serve best for that purpose. Probably each of the opsins has certain advantages and disadvantages and systematic re-engineering of an available mammalian opsin is needed to make a “perfect” tool for vision restoration. The human-native melanopsin is an ideal starting point as it has been extensively tested and is functional without external retinal supply. Moreover, it can function inside ON-bipolar cells, the preferred target for optogenetic vision restoration. Purpose: In this project we will systematically re-engineer melanopsin to make an optogenetic tool ideal for the purpose of vision restoration when expressed in ON-bipolar cells. Methods: We will establish cutting-edge fluorescent imaging techniques to specifically monitor melanopsin signalling in real time. Using these tools as a readout, we will optimize the compatibility of melanopsin to the ON-bipolar cell transduction cascade in terms of G-protein specificity and postsynaptic targeting using a murine model. Moreover, we will kinetically optimize melanopsin by systematically exchanging candidate residues of known relevance for G-protein receptor signalling and novel candidate residues identified by ortholog screening. The resulting “optimized” melanopsin will be tested as a tool for vision restoration side-by-side against microbial opsins in electrophysiological ex-vivo and in-vivo recordings from retina and visual cortex.Impact: This program will, for the first time, provide a systematically optimized mammalian opsin for use in vision restoration and will offer the potential to overcome the limitations observed in alternative tools. Tests in an established murine disease model will quantify its added value and pave the way towards translation into Phase I clinical research.
DFG Programme
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