CRISPR Base Editing Correction of TGFBI Mutations in Autosomal Dominant Corneal Dystrophies.

Purpose: Lattice and granular corneal dystrophy comprise two common TGFBI-associated autosomal dominant corneal disorders. Existing therapies are only temporizing and carry significant morbidity. Here, we develop a novel therapeutic approach using an adenine base editor (ABE) to correct common TGFBI mutations. Method: We generated two human corneal epithelial (HCE) cell models harboring a copy of the most common disease-causing TGBFI mutations, R124C or R555W. These lines were electroporated with an ABE8e-NG-encoding mRNA and guide RNAs targeting the mutations. The resulting A•T-to-G•C editing efficiencies and off-target (OT) effects were assessed by amplicon sequencing. GFP-expressing adeno-associated viruses (AAVs) with different capsid types were transduced into HCE cells and healthy human corneal donor tissues, and GFP fluorescence was evaluated. Results: Using all-RNA delivery for ABE8e-NG, we achieved 91% and 62% correction of the pathogenic adenines in HCE TGFBIR124C/WT and TGFBIR555W/WT cells, without editing the wild-type allele. Indel formation was negligible (<0.2%), bystander adenine editing was minimal (<0.7%), and editing at top computationally predicted OT sites was modest (<1.2% at all but 1 of the 20 OT sites analyzed), suggesting minimal safety concerns. Correction of TGFBIR124C/WT in HCEs rescued the aberrant lysosomal localization of TGFBI. We further identified AAV1 as the most effective serotype for gene delivery into both human corneal donor tissue and HCE cells. Conclusions: Our study demonstrates the feasibility and safety of CRISPR adenine base editing as a new therapeutic strategy for correcting common TGFBI mutations in corneal dystrophies, paving the way for further preclinical testing.