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Z.–H. Pan, J. Cui, E. Olshevskaya, M. Pu, A.M. Dizhoor, A. Bi; Ectopic Expression of Channelrhodopsin–2 Restores Visual Response in Rd1 Mice . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1038.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported the ability of expressing a microbial–type opsin, channelopsin–2 (Chop2), and producing light responses in retinal neurons (Pan et al., ARVO 2005, #4631). In this study, we investigated the feasibility of using Chop2 to restore retinal light sensitivity in rd1/rd1 mice.
AAV–2 viral vectors, carrying Chop2–GFP under the control of a CAG promoter, were subvitreally injected into the eyes of new born (P1) and adult rd1/rd1 mice (at the ages of 2 to 12 months). The expression of Chop2–GFP was examined by GFP fluorescence. Light responses were assessed by patch–clamp recordings in retinal slices, multi–electrode recordings in retinal whole–mounts, and visual evoked potential recordings from visual cortex.
The expression of Chop2–GFP was observed in inner retinal neurons of rd1/rd1 mice up to 16 months of age (four months after viral vector injection). Light–evoked currents were observed in Chop2–GFP positive cells in retinal slices, indicating functional Chop2 channel, channelrhodopsin–2 (ChR2), was formed using only endogenous source for the chromophore in the photoreceptor deficient retina. The ChR2–mediated membrane depolarization and/or spiking rate, and response kinetics were related to light intensities. Assessed by multi–electrode recordings in retinal whole–mounts, the majority of the ChR2–mediated spiking responses were sustained. The spiking rates were remarkably stable. As tested in rd1/rd1 mice at the ages of >6 months, visual evoked potentials were elicited by light stimulation of the Chop2–GFP rescued eyes but not detected by light stimulation of the eyes mock–injected with viral vectors carrying GFP.
This study shows that many inner retinal neurons in rd1/rd1 mice can survive and retain the capability of expression of ChR2 long after the death of photoreceptors. This study also demonstrates that expression of ChR2 can restore the ability of the retina to encode light signals and transmit visual signals to visual cortex. Thus, our results suggest that expression of directly light–gated channels, such as ChR2, is a possible strategy for the restoration of light sensitivity in the retina after rod and cone degeneration.
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