Although, DPRs are toxic in both cell culture and animal models, with the arginine containing poly-GR and poly-PR peptides as the most toxic ones (reviewed by Freibaum and Taylor, 20178), the exact pathological mechanisms by which these DPRs contribute to neurodegeneration in C9orf72-ALS/FTD patients remains disputed. The gene discussed is C9orf72; the disease is frontotemporal dementia.