C9orf72 and frontotemporal dementia: These data, as well as early-onset DPR inclusions in animal models and their inherent toxicity, illustrate the importance of studying the accumulation of brain DPRs in a time- and cell-dependent fashion and may explain why some poly-DPR pathologies are rare in post-mortem brain tissues from C9orf72-ALS/FTD patients, which reflect the end stage of disease and may likely have neuronal death obscuring the mechanisms through which DPRs are causing toxicity.