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Juliette McGregor, Sarah Walters, Keith Parkins, Kamal Dhakal, Jennifer Strazzeri, Brittany Bateman, David Williams, William Merigan; Optogenetic vision restoration in the living macaque. Journal of Vision 2019;19(8):15. doi: https://doi.org/10.1167/19.8.15.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Optogenetics offers the prospect of restoring light sensitivity to ganglion cells when photoreceptor input has been lost due to disease or injury. Channelrhodopsin-mediated activity in primate retinal ganglion cells (RGCs) has previously been demonstrated ex-vivo, but not in the living primate. We assess channelrhodopsin mediated RGC activity in an in-vivo macaque model of retinal degeneration by optically recording from RGCs expressing both a channelrhodopsin (ChrimsonR) and a calcium indicator (GCaMP6s).
Approach: AAV2-CAG-G-CaMP6s and AAV2-CAG-ChrimsonR-tdTomato were co-injected into the vitreous of a normal male macaque (M. fascicularis). A scotoma was created in the superior foveola by a 74 microsecond exposure to 520 Wcm-2, 55 fs pulsed 730 nm light. Adaptive optics scanning light ophthalmoscopy (AOSLO) of GCaMP fluorescence (ex. 488 nm, em. 520/35 nm) was performed while periodic visual stimuli were presented. The amplitude and phase response of individual cells was quantified by Fourier analysis of fluorescence timecourses.
Results: GCaMP6s and ChrimsonR were co-expressed in a para-foveal ring of RGCs. In the region of the RGC ring unaffected by the scotoma, cells showed a clear response to low power periodic pan retinal stimulation, whereas in the superior fovea impacted by the scotoma, RGCs did not respond to the same stimulus indicating that these cells had been deprived of photoreceptor input. When a high power, spatially localized drifting grating stimulus was delivered directly to RGCs lacking functional connections to photoreceptors, light sensitive responses were restored, consistent with the hypothesis that this activity is mediated by ChrimsonR expressed in the RGCs themselves.
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