AAV Induced Expression of Human Rod and Cone Opsin in Bipolar Cells of a Mouse Model of Retinal Degeneration

Michelle E Mcclements,Federica Staurenghi,Meike Visel,John G Flannery,Robert E Maclaren,Jasmina Cehajic-Kapetanovic,Monica M Jablonski

doi:10.1155/2021/4014797

Abstract

Vision loss caused by inherited retinal degeneration affects millions of people worldwide, and clinical trials involving gene supplementation strategies are ongoing for select forms of the disease. When early therapeutic intervention is not possible and patients suffer complete loss of their photoreceptor cells, there is an opportunity for vision restoration techniques, including optogenetic therapy. This therapy provides expression of light-sensitive molecules to surviving cell types of the retina, enabling light perception through residual neuronal pathways. To this end, the bipolar cells make an obvious optogenetic target to enable upstream processing of visual signal in the retina. However, while AAV transduction of the bipolar cells has been described, the expression of human opsins in these cell types within a model of retinal degeneration (rd1) has been less successful. In this study, we have expanded the optogenetic toolkit and shown successful expression of human rhodopsin driven by an ON-bipolar cell promoter (Grm6) in the rd1 mouse model using modified AAV capsids (AAV2.4YF, AAV8.BP2, and AAV2.7m8) delivered via intraocular injection. We also show the first presentation of ectopic expression of human cone opsin in the bipolar cells of rd1 mice. These data provide evidence of an expansion of the optogenetic toolkit with the potential to restore useful visual function, setting the stage for future trials in human patients.

Highlights

Inherited retinal degenerations are the leading cause of blindness in the working age population, affecting approximately 1 in 4,000 people worldwide [1]
Numerous clinical trials have been initiated in recent years, providing adeno-associated viral (AAV) vector gene supplementation strategies for particular forms of inherited retinal disease [2,3,4], leading to the first FDA-approved gene therapy product, Luxturna
In addition to confirming that human rhodopsin can be effectively targeted to bipolar cells using all three capsids and either intravitreal or subretinal delivery routes, we provide the first presentation of medium-wave opsin (MWC) expression in bipolar cells of rd1 mice

Summary

Introduction

Inherited retinal degenerations are the leading cause of blindness in the working age population, affecting approximately 1 in 4,000 people worldwide [1]. Numerous clinical trials have been initiated in recent years, providing adeno-associated viral (AAV) vector gene supplementation strategies for particular forms of inherited retinal disease [2,3,4], leading to the first FDA-approved gene therapy product, Luxturna. Inherited retinal degeneration can result from different mutations in more than 250 genes (RetNet https:// sph.uth.edu/retnet/), and many identified forms have very low prevalence. This makes it unfeasible to develop genespecific treatments for all forms of inherited retinal degeneration. Despite the loss of the lightsensitive photoreceptor cells, inner retinal cells survive and remain largely functional, making them a potential target for optogenetic strategies, a universal approach that can be applied regardless of the genetic origin of the disease [5]

Methods

Results

Conclusion