AAV-mediated Delivery of Rod-derived Cone Viability Factor in a Mouse Model of Retinal Degeneration

Abstract

Purpose: : The bifunctional gene Nxnl1 encodes two products through alternative splicing. Rod-derived cone viability factor (RdCVF), a truncated thioredoxin-like protein, is secreted and has been shown to have a protective effect on the survival of cones in rodent models of retinitis pigmentosa (RP), while the full length protein, RdCVFL, contains a thioredoxin fold and may be involved in oxidative signaling. The aim of these experiments is to further investigate the bifunctional nature of the Nxnl1 gene products, and to evaluate the effects of AAV-mediated delivery of RdCVF and RdCVFL in the rd10 mouse model of retinal degeneration and the S334ter rat, a model of dominant RP.

Methods: : AAV vectors were used to deliver cDNA encoding RdCVF or RdCVFL one day after birth via tail vein injections in mice or via intravitreal injections at p14 in rd10 mice or S334ter-3 rats. The viral vectors were self-complementary ShH10Y445F, a variant of AAV6 that selectively infects Müller glia from the vitreous, or AAV92Yf (carrying 2 tyrosine mutations) injected at P1 into the tail vein of mice. A CAG promoter drove transgene expression. Electroretinograms were recorded to evaluate rescue of rod and cone-mediated responses. The density of cones was evaluated to determine the effect of expression on cone survival, and cone morphology was studied. ONL measurements were taken as a measure of rod survival.

Results: : Injection of ShH10Y445F and AAV92YF leads to efficient expression of GFP, RdCVF and RdCVFL. Delivery of RdCVF via tail vein injections or intravitreal injections leads to functional rescue of the cone-mediated photopic ERG.

Conclusions: : These results support the role of RdCVF as a secreted factor capable of promoting cone survival, as well as the bifunctional nature of the nxnl1 gene. The AAV variant ShH10 efficiently infects Müller glia via intravitreal injection. Targeted Müller cells are capable of delivering RdCVF to its targets in the retina. Additionally, AAV9 infects retinal cells after tail vein injection, and leads to high levels of transgene expression.

Keywords: gene transfer/gene therapy • Muller cells • retinal degenerations: hereditary