C9orf72 and amyotrophic lateral sclerosis: To address critical gaps in understanding of C9orf72-associated DPR structures and their toxicity, we sought to determine whether DPRs, particularly GR, PR, and GA (reported to be the most toxic in the literature), form distinct cytotoxic soluble oligomers in ALS and FTD as they are found similarly in other neurodegenerative diseases.