Dominant dystrophic epidermolysis bullosa (DDEB) is an inherited blistering skin disease resulting from heterozygous mutations in COL7A1, encoding the anchoring fibril protein, type VII collagen (C7). The prototypic mutation is a single nucleotide substitution affecting a glycine residue within the C7 triple helix, resulting in dominant-negative interference between the mutant and wild-type allele-generated C7 proteins. Current treatment options for DDEB are limited although recent advances in genome editing technologies, specifically in base editing, offer new opportunities for clinical development. Adenine base editing (ABE) mediates A-T to G-C base pair changes and so is particularly suited for correcting mutations which are caused by G>A mutations, which account for ~60% of all pathogenic COL7A1 mutations in DDEB. Genome editing can feasibly restore normal gene function by directly correcting the mutated allele, thereby reducing dominant-negative interference, and recapitulating normal C7 homotrimer assembly. For this study, skin was obtained from a DDEB patient with a recurrent glycine substitution in exon 73: c.6082G>A (p.Gly2028Arg). ABE was used to precisely reverse the mutation without double-stranded DNA breaks. We electroporated skin fibroblasts isolated using the Invitrogen Neon Transfection System, with ABE 7.10 mRNA and a single guide RNA targeting the mutation site. High transfection efficiency was demonstrated by GFP-positive cells and Sanger sequencing of the ABE-edited fibroblasts revealed 5% correction at the genomic DNA level. Although greater editing efficiency will be needed for clinical translation, this study provides preliminary data that ABE is a potentially useful approach in developing new treatments for DDEB.

ESDR165 - Allelic specific COL7A1 correction in dominant dystrophic epidermolysis bullosa fibroblasts

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING