Stop mutations cause a Premature Termination Codon (PTC) in the CFTR gene, causing a truncated non-functional CFTR protein. Researchers used RNA editing techniques to rescue the CFTR stop mutation (UGA) thus increasing the therapeutic opportunities for CF patients with stop mutations that currently have no treatment.
To recode the PTC (UGA) in a sense codon (UGG) in the CFTR mRNA they exploited two base editors to convert the PTC’s adenosine to inosine (A-to-I) thus allowing the completion of CFTR translation: the minixABE (A to I Base Editor) and RESTORE (Recruiting Endogenous ADARs to Specific Transcripts for Oligonucleotide-mediated RNA Editing).
Using the minixABE and the RESTORE tools, they used immunofluorescence to observe the recovery of the CFTR protein on the plasma membrane in CFF-16HBEge CFTR W1282X and CFTR G542X human cells. The rescue of the CFTR full transcript was also confirmed. In addition, they successfully tested the recombinant Adeno-Associated Viruses (rAAVs) in which the RNA editing tools were inserted, as a strategy to enhance the delivery in human airway cells.
Altogether the results obtained suggest that UGA stop mutations in the CFTR mRNA might be corrected by RNA editing. These findings pave the way for new and promising scenarios for the treatment of stop mutations of the CFTR gene. Also, combining RNA editing with drugs that inhibit the degradation of mRNA with PTC might be useful. However, several challenges remain, like the delivery and refinement of RNA editing techniques.