Sense and antisense RNA are not toxic in Drosophila models of C9orf72 -associated ALS/FTD

AbstractA GGGGCC hexanucleotide repeat expansion in theC9orf72 gene is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. Neurodegeneration may occur via transcription of the repeats into inherently toxic repetitive sense and antisense RNA species, or via repeat-associated non-ATG initiated translation (RANT) of sense and antisense RNA into toxic dipeptide repeat proteins. We have previously demonstrated that regular interspersion of repeat RNA with stop codons prevents RANT (RNA-only models), allowing us to study the role of repeat RNA in isolation. Here we have created novel RNA-onlyDrosophila models, including the first models of antisense repeat toxicity, and flies expressing extremely large repeats, within the range observed in patients. We generated flies expressing ~  100 repeat sense or antisense RNA either as part of a processed polyadenylated transcript or intronic sequence. We additionally createdDrosophila expressing>  1000 RNA-only repeats in the sense direction. When expressed in adultDrosophila neurons polyadenylated repeat RNA is largely cytoplasmic in localisation, whilst intronic repeat RNA forms intranuclear RNA foci, as does>  1000 repeat RNA, thus allowing us to investigate both nuclear and cytoplasmic RNA toxicity. We confirmed that these RNA foci are capable of sequestering endogenousDrosophila RNA-binding proteins, and that the production of dipeptide proteins (poly-glycine –proline, and poly-glycineâ...

Source: Acta Neuropathologica - January 29, 2018 Category: Neurology Source Type: research