Expanding the RNA-editing toolbox

Abstract

volume 18 | SePTemBeR 2019 | 667 these studies demonstrate the potential for precise, efficient and programmable RNA editing lines, its efficiency reflecting ADAR1 and ADAR2 enzyme expression. Plasmid-mediated arRNA delivery also enabled editing endogenous transcripts in HEK293 cells. The authors next applied LEAPER to correct pathogenic G>A mutations in HEK293 cells co-expressing arRNAs targeting six pathogenic genes and their complementary DNA pairs. Further supporting the potential clinical use of LEAPER, arRNAs were shown to be effective in several primary human cell lines and could be efficiently delivered by a viral vector or as a synthetic oligonucleotide. Importantly, LEAPER was safe and specific, exerting little impact on the normal A-to-I editing function of endogenous ADAR, did not affect global gene expression and did not induce immunogenicity in target cells. Finally, the authors explored the potential therapeutic application of arRNAs. LEAPER was first applied to repair the cancer relevant c.158G>A nonsense mutation in TP53 (which results in a non-functional truncated protein) and restore its function in HEK293T cells. In addition, LEAPER restored α-l-iduronidase (IDUA) catalytic activity in primary fibroblasts derived from patients with Hurler syndrome, the most severe subtype of mucopolysaccharidosis type I. Importantly, there were minimal unwanted edits within the arRNA-covered regions of IDUA transcripts and no induction of innate immune responses. Together, these studies demonstrate the potential for precise, efficient and programmable RNA editing and expand the range of potential clinical applications of such technologies.