ADAR therapy: a breakthrough against genetic disorders

Adenosine Deaminases Acting on RNA (ADAR) catalyze the transformation of adenosine (A) into inosine (I) within double-stranded RNA (dsRNA) structures. This process, known as A-I RNA editing, plays a crucial role in regulating gene expression, maintaining RNA stability, and influencing protein function. Recently, innovative therapeutic strategies have emerged, focusing on site-directed RNA editing (SDRE). These approaches harness the recoding potential of ADAR enzymes to correct pathogenic G-to-A nucleotide mutations. SDRE offers a way to modify genetic information without causing damage to the genome itself. Notably, G-to-A point mutations account for nearly 30% of pathogenic single nucleotide variations identified in the human genome, making them promising candidates for correction via ADAR-mediated mechanisms. To evaluate the therapeutic potential of ADAR enzymes, we targeted G-to-A genetic mutations associated with various pathologies. First, we developed an in vitro model using HEK293 cells to address the LRRK2 G2019S mutation, which is implicated in Parkinson's disease. Transient co-transfection of a vector expressing a 100-nucleotide guide RNA along with a vector encoding ADAR1 enzymes resulted in site-directed RNA editing with approximately 60% efficiency, indicating that more than half of the mutated mRNA was corrected at the transcript level. Additionally, in HEK293 cells stably expressing the p.A382T mutated form of the TAR DNA-binding protein 43 (TDP-43) gene, which has been linked to Amyotrophic Lateral Sclerosis (ALS), a correction rate of 30% was achieved. Finally, we are investigating two mutations in the COL3A1 gene (p.G693A and p.G996A) associated with the onset of Ehlers–Danlos syndrome. This project aims to develop an innovative RNA-based therapeutic approach leveraging the activity of ADAR enzymes. By identifying effective guide RNAs to recruit endogenous ADAR enzymes to specific mutations, this therapy has the potential to correct these mutations, restore normal RNA function, and slow or halt disease progression.