Résumé
Mutations in the RLBP1 gene cause inherited retinal diseases (IRDs) such as retinitis punctata albescens (RPA). RPA is characterized by night vision alterations and the presence of irregular white dots in the retina. The encoded protein, CRALBP, is involved in the visual cycle as a carrier of 11-cis retinoids. To better understand the impact of different mutations in RLBP1, skin fibroblast from control and RPA patients were reprogrammed into iPSC, and then differentiated into RPE or retinal organoïds. Furthermore, patient-specific iPSC-derived RPE were transduced with an AAV vector carrying hRLBP1 as a potential therapeutic approach.The expression of CRALBP in the control and patient-specific iPSC-derived RPE and retinal organoïds, as well as in the transduced RPE, was analyzed by western blots. Unexpectedly, patient iPSC-derived RPE cells transduced with the AAV-hRLBP1 vector expressed two CRALBP isoforms. High resolution gel analysis also confirmed the endogenous presence of these two isoforms in control RPE, whereas retinal organoïds only expressed a single isoform of CRALBP. In parallel, we tested CRALBP expression in the murine neuroretina and RPE, which also expressed one or two isoforms, respectively. Finally, in vitro site-directed mutagenesis assays determined that the shorter isoform was generated by a second ATG initiation site.Taken together, iPSC-derived RPE and retinal organoids were able to mimic mammalian CRALBP expression and identify a previously unreported CRALBP isoform. This work shows the potential of such retinal models as useful tools to better understand physiology as well as physiopathology in IRDs.