C9 and frontotemporal dementia: Supporting the disease relevance of this finding, the insolubility of FUS and other interacting proteins that we observe in the FUS mice is also evident in the brain and spinal cord of a FUSP525L ALS patient, in which we find biochemical insolubility similar to that which we reported in the CNS of patients with ALS/FTD with the C9orf72 expansion as well as sporadic cases that we found to be like C9.