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X. Sun, B. S. Pawlyk, X. Y. Xu, M. Adamian, M. A. Sandberg, R. R. Ali, T. Li; Replacement Gene Therapy in Mouse Models of LCA Lacking AIPL1. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1738.
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© ARVO (1962-2015); The Authors (2016-present)
Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) is a photoreceptor-specific protein essential for the biosynthesis of rod and cone phosphodiesterases (PDE). Mutations in the gene encoding AIPL1 cause Leber congenital amaurosis (LCA), a severe form of photoreceptor degeneration. We evaluated whether replacement gene therapy with AIPL1 driven by a photoreceptor-specific promoter could restore photoreceptor structure and function in mouse models of LCA.
AIPL1 replacement gene constructs of mouse and human origins were placed under the transcriptional control of a human rhodopsin kinase (hRK) promoter and packaged into AAV2/5 and AAV2/8 vectors, respectively. Cohorts of AIPL1 hypomorphic and null mutant mice were studied. Mouse was given a single subretinal injection in one eye of an AAV vector containing an AIPL1 construct, with the fellow eye receiving a control AAV vector containing a GFP reporter construct. Mice were evaluated from 2 weeks to 6 months post-injection (up to 25 months of age) by electroretinography (ERG), immunofluorescence, light microscopy, and immunoblotting analysis for evidence of AIPL1 protein expression, restoration of PDE synthesis, and photoreceptor rescue.
In both hypomorphic and null AIPL1 mutant mice, treatment with the AIPL1 constructs resulted in AIPL1 protein expression, restoration of PDE synthesis in both rod and cone photoreceptors, and partial rescue of the disease phenotype. Levels of transgene expression were comparable to or slightly less than the endogenous expression. Notably, the null mutant mice, which exhibit a very fast course of degeneration, could be substantially rescued by using an AAV2/8 vector with the AIPL1 construct. However an AAV2/5 vector of similar design showed minimal therapeutic effect, presumably reflecting a slower onset of transgene expression of the latter vector.
The human RK promoter appears suitable for driving AIPL1 expression for gene replacement therapy. This study has validated the design of an AIPL1 replacement gene construct of human origin driven by a photoreceptor specific promoter. The same construct may be appropriate for a clinical trial.
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