Stem Cell Rep. 10, 1267–1281 (2018).

Retinitis pigmentosa is an inherited retinopathy caused by mutations in the RPGR gene, which leads to blindness. To study disease mechanisms, Jin and colleagues reprogrammed urinary cells from three patients into inducible pluripotent stem cells (iPSCs) and generated 3D self-forming retinal organoids.

After long-term differentiation, the authors obtained rod photoreceptor cells with outer segments and electro-physiological properties. Patient organoids showed abnormal photoreceptor layer morphology, dislocation of opsins, shorter outer segments and impaired rhodopsin transport. Gene expression associated with photoreceptor maturation and phototransduction was reduced, indicating defects in photoreceptor function. RPGR mutations were then prepared in one iPSC line using CRISPR–Cas9 gene editing, which restored cell morphology, rod and cone numbers, expression patterns of photoreceptor-related genes and GFAP proteins, electro-physiological properties, and decreased apoptosis markers in the inner organoid layer. As RPGR contributes to ciliogenesis, cilia lengths in patient urinary cells, iPSCs, iPSC-derived retinal pigment epithelium and 3D retinae were also assessed and were shorter compared to controls. RPGR-corrected patient iPSCs and retinal pigment epithelium, however, exhibited normal cilia lengths. Overall, the patient-derived organoids accurately recapitulated disease phenotypes, which could be rescued using gene correction.