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Yuxin Zhang, Wei Du, Ping Zhu, Jie Li, Wen-Tao Deng, Sanford L Boye, Xi-Qin Ding, Shannon Elizabeth Boye, William W Hauswirth; AAV-mediated Long Term Rescue of Cone Function in the CNGA3-/-Nrl-/- Mice Following Intravitreal Injection. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5468.
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© ARVO (1962-2015); The Authors (2016-present)
Deletion of neural retina leucine zipper in mice (Nrl−/−) results in the complete absence of rods and an all-cone retina. Nrl-/- mice lack a scotopic response and have enhanced photopic ERG amplitudes. Mutations in the gene encoding the alpha-subunit of the cone cyclic nucleotide-gated channel (CNGA3) cause loss of cone function in mammals and are associated with achromatopsia in humans. CNGA3-/-Nrl-/- mice have been bred in part to mimic the cone-rich central retina in human achromatopsia 2 with CNGA3 mutations. Here we tested whether mutant AAV8 (Y447, 733F) vector can persistently restore cone system function/structure following intravitreal injection in this model.
At postnatal day 14, one μl of AAV8 (Y447, 733)-IRBP/GNAT2-mCnga3 vector (1013 particles/ml) was injected intravitreally into one eye of each CNGA3-/-Nrl-/- mouse. The other eye was uninjected to serve as a control. Dark- and light-adapted ERGs were recorded at six months after either injection. Then treated and control eyes were harvested for immunohistochemical studies.
At six months following intravitreal injection, rod-related scotopic ERG waveforms were recorded in either treated or untreated Cnga3/Nrl DKO eyes. At a flash intensity of 1.4 log cd.s/m2, the average b-wave amplitudes of cone-related photopic ERGs were 63.76±24.05 μV in treated CNGA3-/-Nrl-/- eyes, 12.35±5.733 μV in untreated CNGA3-/-Nrl-/- eyes, and 137.2 ± 25.94 μV in age-matched Nrl-/- control eyes. There were significant differences between them. Eyes with the best light-adapted ERG restoration showed similar cone opsin levels as Nrl-/- control eyes with abundant M- and S-opsins observed in the cone outer segments. In untreated eyes, both M- and S-cone opsins were absent. Optomotor testing showed improved cone-driven visual acuity and contrast sensitivity in the treated CNGA3-/-Nrl-/- eyes, compared with those in the untreated eyes.
Intravitreal delivery of mutant AAV can restore cone function and halt cone degeneration for at least six months in the CNGA3-/-Nrl-/- mice. These results serve as a baseline for studying the intravitreal injection-mediated gene replacement therapy for human achromatopsia.
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