Dual CRALBP isoforms unveiled: iPSC-derived retinal modelling and AAV2/5-RLBP1 gene transfer raise considerations for effective therapy

Abstract

AbstractInherited retinal diseases (IRDs) are clinically and genetically heterogeneous disorders characterised by progressive vision loss. Over 270 causative genes have been identified and variants within the same gene can give rise to clinically distinct disorders. Human induced pluripotent stem cells (iPSCs) have revolutionised disease modelling, by allowing pathophysiological and therapeutic studies in the patient and tissue context. The IRD geneRLBP1encodes CRALBP, an actor of the rod and cone visual cycles in the retinal pigment epithelium (RPE) and Müller cells, respectively. Variants inRLBP1lead to three clinical subtypes: Bothnia dystrophy, Retinitis punctata albescens and Newfoundland rod-cone dystrophy. We modelledRLBP1-IRD subtypes by patient-specific iPSC-derived RPE and identified pertinent therapeutic read-outs. We developed an AAV2/5-mediated gene replacement strategy and provided a proof-of-concept in theex vivohuman models that was validated in anin vivo Rlbp1−/−murine model. Most importantly, we identified a previously unsuspected smaller CRALBP isoform that is naturally and differentially expressed in both human and murine retina. The new isoform arises from an alternative methionine initiation site and plays a role in the visual cycle. This work provides novel insights into CRALBP expression andRLBP1-associated pathophysiology and raises important considerations for successful gene supplementation therapy.