Single-AAV Base-Editing in Noonan Syndrome-associated hypertrophic cardiomyopathy

Noonan Syndrome is a multisystem disorder characterized by a variable clinical presentation. Moreover, it is one of the most common monogenetic diseases associated with congenital heart defects, such as hypertrophic cardiomyopathy. Noonan Syndrome is caused by mutations leading to a hyperactivation of the RAS/MAPK signaling pathway. Pathogenic variants in LZTR1 have been linked to Noonan Syndrome with a severe and early-onset hypertrophic cardiomyopathy. Despite its epidemiological relevance, therapeutic interventions remain limited as no curative treatment exists. Hence, a personalized CRISPR-based gene editing approach might offer a potential therapeutic strategy for a curative treatment of these patients. In this study, we evaluated different clinically translatable Base-Editing approaches to correct a deep-intronic variant in LZTR1 leading to a cryptic exon and subsequent truncation of the protein, to rescue the disease-associated pathology. As a proof-of-principle, we applied Adenine Base Editing to correct the cryptic splice site in LZTR1 intron 16 in patient-specific iPSC. Allele specific Base editing of the mutated allele normalized transcript splicing and rescued LZTR1 function. Further, single-AAV transduction of all-in-one base editors in patient-specific iPSC-derived cardiomyocytes from Noonan Syndrome patients confirmed rescue of the molecular pathology, offering a clinically translatable CRISPR approach for Noonan Syndrome patients with hypertrophic cardiomyopathy.