Abstract
Purpose :
Inherited retinal degenerations (IRDs) result in blindness due to apoptotic cell death of rods and cones, but spare other retinal neurons, providing a potential that delivery of a light-activated signaling protein to surviving neurons may restore vision. Aspects of vision are restored when mGluR2 is engineered to respond to light by tethering of a photoswitchable agonist. However, as with channelrhodopsins, the system has such low sensitivity that it would require intensifying goggles to work in roomlight. We increasd sensitivity to obtain high acuity vision in dim light.
Methods :
Using AAV, we delivered to retinal ganglion cells (RGCs) the gene encoding the GCPR, mGluR2, engineered to contain an N-terminal SNAP domain, to which we could tether a photoswitchable agonist. We increased the sensitivity with a branched photoswitch containing four light-activatable glutamates for each glutamate binding site. Light sensitivity was tested in a Light/Dark box; object recognition in open field under dim light; acuity and abilility to recognize line patterns in motion using standard 500 nit LCD computer screens displaying pairs of lines at different spacings.
Results :
4-branched BGAG SNAP-mGluR2 in all RGCs restores the ability to perform visual tasks in dim room light and using standard LCD computer screens. The system restores line pattern differentiation to approximately the acuity of normal mouse vision and supports pattern recognition at 48o/s of motion.
Conclusions :
We achieve high-sensitivity and high-acuity vision that works at high speed of motion and which supports object exploration in dim incidental light. While photopharmacology adds an additional layer of treatment to gene therapy, it provides the dual advantage of upgrade as new photoswitches are developed and the ability to be discontinued at will.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.