Combining nonsense mutation suppression therapy with nonsense-mediated decay inhibition in neurofibromatosis type 1

Abstract

Neurofibromatosis type 1 (NF1) results from germline mutations in the tumor-suppressor gene NF1 and predisposes patients to developing nervous system tumors. Twenty percent of NF1 patients harbor nonsense mutations resulting in premature termination codons (PTCs). Nonsense suppression therapies can facilitate ribosomal readthrough of PTCs to restore full-length protein, but their potential in NF1 is underexplored. We developed a minipig model of NF1 carrying a PTC to test whether nonsense suppression could restore expression of the NF1-encoded protein neurofibromin invitro and invivo. Nonsense suppression did not reliably increaseneurofibromin in primary NF1-/- Schwann cells isolated from minipig neurofibromas but could reduce phosphorylated ERK. Gentamicin invivo produced a similar plasma pharmacokinetic profile to humans and was detectable in clinicallyrelevant tissues, including cerebral cortex, sciatic nerve,optic nerve, and skin. In gentamicin-treated animals, increased neurofibromin expression was seen in the optic nerve. Nonsense-mediated decay (NMD) causes degradation of transcripts with PTCs, which could impede nonsense suppressiontherapies. Nonsense suppression in combination with NMD inhibition restored neurofibromin protein expression in primary NF1-/- Schwann cells isolated from minipig neurofibromas. Thus, the effectiveness of nonsense suppression therapies can be improved in NF1 by the concurrent use of NMD inhibitors.