RNA Editing Approaches for the correction of nonsense mutation in a cell model for Cystic Fibrosis

Cystic Fibrosis (CF) is an autosomal recessive disease caused by mutations in the CFTR gene. In particular, CFTR nonsense (STOP) mutations generate a premature termination codon (PTC) in the mRNA, leading to the production of a shortened and non-functional protein1. Currently, there is no pharmacological therapy that specifically targets nonsense mutations in CF. In this regard, we are exploring the possibility to correct the PTC using different RNA-based editing tools. These systems exploit the Adenosine Deaminases Acting on RNA (ADAR) to convert the adenosine within the PTC into inosine and allow the full-length protein synthesis2. Among these, a compact REPAIRv2 system uses a modified and truncated dCAS13x.1 fused with ADAR2DD that is recruited to the adenosine of PTC by means of a specifically designed guide RNA1. A different system named RESTORE uses specific antisense RNA oligonucleotides (ASOs), complementary to the CFTR mRNA region with the PTC, except for a cytidine-adenosine mismatch that promotes ADAR recruitment3. In addition, we also evaluated phenotypical anomalies of CFTR mutated cells showing morphological differences in comparison to wild type cells4. Our results pave the way to new therapeutical strategies potentially able to correct the nonsense mutations in cystic fibrosis.