A cell-penetrant peptide blocking <i>C9ORF72</i>-repeat RNA nuclear export reduces the neurotoxic effects of dipeptide repeat proteins.

Abstract

Hexanucleotide repeat expansions in <i>C9ORF72</i> are the most common genetic cause of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Studies have shown that the hexanucleotide expansions cause the noncanonical translation of <i>C9ORF72</i> transcripts into neurotoxic dipeptide repeat proteins (DPRs) that contribute to neurodegeneration. We show that a cell-penetrant peptide blocked the nuclear export of <i>C9ORF72</i>-repeat transcripts in HEK293T cells by competing with the interaction between SR-rich splicing factor 1 (SRSF1) and nuclear export factor 1 (NXF1). The cell-penetrant peptide also blocked the translation of toxic DPRs in neurons differentiated from induced neural progenitor cells (iNPCs), which were derived from individuals carrying <i>C9ORF72</i>-linked ALS mutations. This peptide also increased survival of iNPC-differentiated C9ORF72-ALS motor neurons cocultured with astrocytes. Oral administration of the cell-penetrant peptide reduced DPR translation and rescued locomotor deficits in a <i>Drosophila</i> model of mutant C9ORF72-mediated ALS/FTD. Intrathecal injection of this peptide into the brains of ALS/FTD mice carrying a <i>C9ORF72</i> mutation resulted in reduced expression of DPRs in mouse brains. These findings demonstrate that disrupting the production of DPRs in cellular and animal models of ALS/FTD might be a strategy to ameliorate neurodegeneration in these diseases.