C9orf72 and amyotrophic lateral sclerosis: Importantly, p53 appears to play a key role in C9ORF72-ALS and DPR-induced toxicity as p53 knockout or knockdown has been shown to extend the lifespan of a mouse model expressing poly(PR), and protect against neurodegeneration in Drosophila models expressing the C9ORF72 repeat expansion [74].