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Seok-Hong Min, Qing Ruan, Sanford L Boye, Shannon Boye, William W Hauswirth, Christine Nichols Kay; Expression of CNGB3 provides long-term rescue in the cone-only CNGB3 x NRL double knock-out (DKO) mouse. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3309.
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© ARVO (1962-2015); The Authors (2016-present)
Achromatopsia (ACHM) is a congenital cone photoreceptor disorder with an incidence of 1:30,000. Cyclic nucleotide gated channel beta 3 (CNGB3) has been reported to account for approximately 50% of this autosomal recessive disease. CNGB3 KO mice have been used successfully as an animal model for gene therapy, but the translation from a rod-dominant murine model to human cone dystrophies is limited. Here, our goal was to test the effects of CNGB3 gene replacement in a CNGB3 x NRL double knock-out (DKO) mouse which more closely resembles the cone dominant macula of ACHM patients.
We generated photoreceptor-specific AAV vectors to express CNGB3 in CNGB3 x NRL DKO mice. One microliter (1 x 1012 vector genomes/ml) of AAV8(Y733F) vectors containing the photoreceptor-specific IRBP/GNAT2 promoter driving a human CNGB3 cDNA was delivered subretinally to one eye of CNGB3 x NRL DKO mice at 2 weeks of age. Contralateral eyes were untreated and served as controls. Retinal function was assessed by cone electroretinography (ERG) under photopic conditions out to 8 months post-injection. Responses from both M- and S- cones were isolated individually. Histological analysis is underway.
At eight months post-injection, AAV8(Y733F)-CNGB3 treated eyes exhibited significantly increased ERG amplitudes (nearly double) compared to contralateral untreated controls. Further analyses showed that treatment increased isolated responses mediated by either M- or S-cone opsin, with larger improvements in the S-cone opsin mediated response.
Expression of CNGB3 driven by the IRBP/GNAT2 promoter in an AAV vector led to stable (at least 8 months) and significant increases in cone ERG amplitudes. Given its cone only makeup, the CNGB3 x NRL DKO mouse may provide a useful model for relevant proof of concept testing of gene replacement strategies for human achromatopsia.
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