Résumé
Purpose: Inherited retinal dystrophies (IRDs) are caused by mutations in several genes including CRX. CRX encodes the cone-rod homeobox protein CRX, a transcription factor crucial for mammalian photoreceptor differentiation. Mutations in the human CRX gene are associated with autosomal dominant IRD forms: Retinitis Pigmentosa (RP), Cone-Rod Dystrophy (CoRD) and Leber Congenital Amauris (LCA). To further study these diseases we generated retinal organoid models from the induced pluripotent stem cells (iPSCs) of CRX patients affected with two different IRD forms, CRX-CRD and CRX-LCA. Furthermore we generated iPSC-derived retinal organoids from an asymptomatic individual (CRX-CRD-AS) carrying the same CRX-CRD mutation. Methods: Four iPSC clones (WT, CRX-CRD-AS, CRX-CRD and CRX-LA) were differentiated into retinal organoids, and the gene and protein expression of retinal markers were analysed at different time points over the differentiation period (at 56, 100, 150 and 225 days).Results: We observed an altered expression profile for all the clones in comparison to WT that varied depending on the the level of severity of the associated IRD form (CRX-CRD-AS < CRX-CRD < CRX-LCA ). In general, qPCR and immunofluorescence analyses identified anomalies in the expression of photoreceptor-specific genes. Early in the differentiation period, we observed a down-regulation of genes/proteins known to interact with CRX, such as NR2E3 and NRL. At later stages, the expression of mature photoreceptor markers, such as the opsins, was impacted. Interestingly, although clinically unaffected, the CRX-CRD-AS did show mild deregulation of gene and protein expression.Conclusion: The generation of retinal organoids from patients with IRDs allow a better understanding of the pathophysiology of different disease forms, regardless of their clinical severity. Furthermore, the comparison of retinal organoids from a patient carrying a CRX-CRD mutation and an asymptomatic sibling carrying the same mutation will allow us to finely elucidate the mechanisms underlying the appearance of the clinical signs.