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H. Mao, M. S. Gorbatyuk, W. W. Hauswirth, A. S. Lewin; Adeno-Associated Virus-Vectored Gene Therapy With Wild-Type Rhodopsin Gene in a Mouse Model of Autosomal Dominant Retinitis Pigmentosa (ADRP). Invest. Ophthalmol. Vis. Sci. 2010;51(13):1362.
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Autosomal dominant retinitis pigmentosa (ADRP) is frequently caused by mutations in the RHO gene, which codes for the opsin of rod photoreceptor cells. The purpose of this study is to treat ADRP with the expression of normal rhodopsin gene in a transgenic animal model.
We are testing gene therapy in a mouse model of ADRP that expresses a human transgene with a prevalent ADRP mutation: proline 23 substituted by histidine (P23H). We designed and constructed a "hardened" form of the rhodopsin (RHO) gene that is specifically resistant to degradation by the siRNA 301. We had previously demonstrated that siRNA301 degrades both mutant and wild-type mouse and human RHO mRNA. The "hardened" RHO gene (RHO301) was generated by introducing silent mutations to eliminate the siRNA cleavage site. RHO301 in AAV5 was delivered by subretinal injection in the right eyes, control virus was injected by the same method in the left eyes. Following delivery of RHO301 in AAV5 to P23H transgenic mice in a background of mouse RHO+/-, we measured the scotopic electroretinography (ERG) response of injected mice at intervals of 1, 2 and 3 months post injection
The maximum amplitudes of the ERG a-wave and b-wave were elevated in the eyes treated with AAV-RHO301 compared to uninjected eyes or to control-injected eyes. In contrast, delivery of RHO301 to the eyes of wild-type mice, led to a decrease in the ERG response. Microscopic analysis indicated that injection of RHO301 preserved the normal morphology of photoreceptors relative to untreated eyes bearing the P23H mutation.
The finding that a gene encoding wild-type rhodopsin could moderate the retinal degeneration in this model suggests that P23H rhodopsin causes a dominant negative effect, but not by gain of a toxic function, since increased production of normal rhodopsin could suppress the effect of the mutation. Our finding implies that some RHO mutations leading to ADRP can be treated by gene transfer of normal RHO.
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