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Wen-Tao Deng, Ping Zhu, Tiffanie Dahl, Wolfgang Baehr, William W Hauswirth; Rescue of cone structure and function in Opn1mw/sw double knockout mice. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2456.
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© ARVO (1962-2015); The Authors (2016-present)
Knockout of both Opn1mw and Opn1sw in mouse results in complete deletion of cone opsin expression in the entire retina. We have shown previously that Opn1mw/sw double knockout (DKO) mice lack photopic ERG responses, and cone outer segments are absent. However, cones remain viable based on cone arrestin staining. We seek to determine whether cone structure and function can still be rescued by gene therapy and if so, the rescue time frame.
AAV5 vector expressing human L-opsin driven by the cone-specific PR2.1 promoter was injected subretinally into one eye of 1- and 3-month old Opn1mw/sw DKO mice, while the contralateral eyes remained untreated. Cone mediated retinal function was analyzed 5 weeks post-injection by electroretinography (ERG). L-opsin transgene expression and cone outer segments were examined by immunohistochemistry using antibodies against M/L-opsin, S-opsin, and cone PDE6γ’ subunit.
AAV5-mediated expression of human L-opsin rescued cone structure and function in DKO mice. The ERG responses in treated eyes were significantly higher than the untreated controls. ERG responses were 40 ± 16 µV and 37 ± 16 µV (average ± SEM) in DKO treated at 1- and 3-month of age, respectively, unrecordable in untreated controls (n=7, P < 0.005), and was 115 ± 12 µV in wild type controls. Transgene expression was detected in cone outer segments. Cone PDE6γ’ was detected primarily in cone inner segments in untreated eyes, while partially translocated into outer segments after treatment. Notably, only some cones showed detectable levels of correctly localized PDE6γ’ staining, and it was more prominent in mice treated at 1 month of age than those treated at 3 months of age.
Our results show that the cone photoreceptors of Opn1mw/sw DKO mice can be rescued. However, although cone inner segments are still preserved in some cones, treatment might be limited after a certain age.
This is a 2020 ARVO Annual Meeting abstract.
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