Fig 2: Ophthalmic investigations and genetic findings. Patient II-1: (a) wide-field pseudocolor fundus images showing discrete RPE mottling in the midperiphery illustrating outer retinal atrophy and small white intraretinal spots or flecks in the perimacular region. (b) Wide-field fundus autofluorescence (WF-FAF) showing significantly reduced retinal autofluorescence signal. (c) Optical coherence tomography (OCT) showing photoreceptor complex relatively intact. Patient II-2: (d) wide-field pseudocolor fundus images showing widespread distribution of discrete RPE mottling and white/yellow flecks in the midperipheral fundus. (e) WF-FAF illustrating almost absent fundus autofluorescence. (f) OCT showing preservation of the ellipsoid zone across the macula with slight macular thinning. (g) Normal wide-field pseudocolor fundus image. Note the homogenous retinal background with no white/yellow flecks or blotches (Optos Dunfermline UK). (h) Normal wide-field fundus autofluorescence. Note that the retinal blood vessels and optic disc appear black because they do not fluoresce. Compare this to images (b) and (e) where there is little or no retinal autofluoresence in the whole of the retina so the blood vessels and optic disc merge into the image. (i) Normal OCT scan showing well defined outer retinal structures compared to both patients. (j) Full-field electroretinogram (ffERG) with patient II-1 top row, patient II-2 middle row and age matched normal bottom row. Both patients II-1 and II-2 show undetectable scotopic responses and residual attenuated photopic function. (k) Pedigree showing biparental inheritance of the two RPE65 alleles and Sanger sequencing traces.

Fig 3: Differentiation of hiPSCs to hiPSC-RPE cells. (a) Representative brightfield image of a parental carrier hiPSC colony, scale bar = 100 µm. (b) Formation of pigmented RPE islands in day 30-40 retinal differentiation cultures, scale bar = 100 µm. (c) Cell culture expansion of RPE islands formed a purified monolayer of hiPSC-RPE cells after 90 days of differentiation, scale bar = 100 µm. (d) hiPSC-RPE cells cultured on coverslips were fixed in 4% paraformaldehyde/PBS and stained with ZO-1 (green) tight junction expression highlighting the hexagonal shape of hiPSC-RPE cells. Nuclei stained with DAPI (blue). (e, f) Immunofluorescence detection of RPE markers CRX and MITF (red) in hiPSC-RPE cells. (g, h) Verification of differentiation of control and carrier (c.93A>G) hiPSCs to RPE cells by RT-qPCR detection of increased relative gene expression of RPE markers (BEST1, MERTK, MITF, PAX6, PMEL17, and RPE65) (unpaired t-test, n = 3 replicates, *P < 0.05; **P < 0.005).