Antisense oligonucleotides targeting exon 11 are able to partially rescue the Neurofibromatosis Type 2 phenotype in vitro

Neurofibromatosis type 2 (NF2) is an autosomal dominant condition caused by loss of function variants in the NF2 gene, which codes for the protein Merlin, and characterized by the development of multiple tumours of the nervous system. The clinical presentation of the disease is variable and related to the type of the inherited germline variant. Here, we tested if PMOs could be used to correct the splice signalling caused by variants at +/-13 within the intron-exon boundary region. Here we show that the PMOs designed for these variants do not constitute a therapeutic approach. Furthermore, we evaluated the use of phosphorodiamidate morpholino oligomers (PMOs) to reduce the severity of the effects of NF2 truncating variants with the aim of generating milder hypomorphic isoforms in vitro through the induction of the in-frame deletion of the exon-carrying variant. We were able to specifically induce the skipping of exons 4, 8 and 11 maintaining the NF2 gene reading frame at cDNA level. Only the skipping of exon 11 produced a hypomorphic Merlin (Merlin-e11), able to partially rescue the observed phenotype in primary fibroblast cultures from NF2 patients, being encouraging for the treatment of patients harbouring truncating variants located in exon 11.