Fig. 1: Adenine base editing corrects the most common Stargardt disease-associated mutation in vitro.

a, Images of a retina of an individual with Stargardt disease with biallelic ABCA4 mutations (c.5882G>A, p.Gly1961Glu); (c.66G>A, p.K = ) and of a healthy individual. The magnified grayscale images show the corresponding autofluorescence images. Decreased foveal autofluorescence (dark region) detected in the individual indicates atrophy of RPE cells. OCT images (bottom) show a cross-sectional view of the retina. The photoreceptor and RPE layers are highlighted to indicate foveal thinning. b, Dual AAV split-intein adenine base-editing strategy. Two adenines fall in the base-editing window: the c.5882A target base and the c.5883A wobble base of codon 1961. Conversion of the wobble base results in a silent base change. WtTadA and eTadA denote wild-type and evolved tRNA adenosine deaminase, respectively. c, Model systems used in the evaluation of ABCA4 base-editing efficiency in photoreceptors and RPE cells. Genotype of the model systems, target adenines, delivery modalities and the targeted sites are indicated. The colors in the fourth column highlight the model-specific gRNA. STGD-gRNA, Stargardt disease gRNA; wt-gRNA, wild-type gRNA; ms-gRNA, mouse gRNA. Illustrations in c–e and illustrations of the AAV inverted terminal repeats (ITRs) created with BioRender.com. d, Base-editing efficiencies at the A7 and A8 sites with ABE7.10 split at five different positions in lenti-ABCA4^1961E HEK293T cells. Results were obtained from four biological replicates and presented as the mean ± s.d. ***P < 0.001, by three-way mixed-effects analysis of variance (ANOVA) with Dunnett’s correction, compared to the unsplit ABE7.10 construct. NS, not significant. e, Base-editing efficiencies at the A7 and A8 sites with different ABE versions in lenti-ABCA4^1961E HEK293T cells (top). Results were obtained from three replicates and are presented as means. Dual AAV-mediated base-editing efficiencies at the A8 site in gDNA of human iPS cell-RPE cells (bottom). Results were obtained from two replicates and are presented as means. f, AAV-mediated base-editing in gDNA and in ABCA4 mRNA of different in vitro models using an ABE8.5m base editor split at amino acid residue 310 of SpCas9 (total dose: 2.3 × 10¹¹ vector genomes (v.g.) per organoid and 3.3 × 10¹¹ v.g. per human tissue, 1:1 ratio of ABE(N) and ABE(C)). Results were obtained from two to three replicates and are presented as means.