Morphological and Molecular Defects in Human Three-Dimensional Retinal Organoid Model of X-Linked Juvenile Retinoschisis

Summary: X-linked juvenile retinoschisis (XLRS), linked to mutations in the RS1 gene, is a degenerative retinopathy with a retinal splitting phenotype. We generated human induced pluripotent stem cells (hiPSCs) from patients to study XLRS in a 3D retinal organoid in vitro differentiation system. This model recapitulates key features of XLRS including retinal splitting, defective retinoschisin production, outer-segment defects, abnormal paxillin turnover, and impaired ER-Golgi transportation. RS1 mutation also affects the development of photoreceptor sensory cilia and results in altered expression of other retinopathy-associated genes. CRISPR/Cas9 correction of the disease-associated C625T mutation normalizes the splitting phenotype, outer-segment defects, paxillin dynamics, ciliary marker expression, and transcriptome profiles. Likewise, mutating RS1 in control hiPSCs produces the disease-associated phenotypes. Finally, we show that the C625T mutation can be repaired precisely and efficiently using a base-editing approach. Taken together, our data establish 3D organoids as a valid disease model. : Chiou, Schlaeger, and colleagues use hiPSC-derived retinal organoids to model X-linked juvenile retinoschisis. They show that patient hiPSC-derived retinal organoids replicate key pathologies observed in patients, including retinal splitting and photoreceptor deficit. The observed abnormalities were normalized in organoids derived from isogenic CRISPR/Cas9 gene-corrected hiPSCs. This validated XLRS in vitro model could be used to test and optimize therapeutic approaches. Keywords: retinal degeneration, X-linked juvenile retinoschisis, retinal organoid, induced pluripotent stem cells, retinogenesis, CRISPR/Cas9 gene editing, RS1, retinoschisin