To test if human wild-type FUS can be seeded to aggregate (as is seen in examples of sporadic ALS and FTLD [45]), FUSR495X fibrils were focally injected at single sites within the cortex or hippocampus of 16-month-old humanized mFUSKO/FUSWT mice in which both endogenous mouse FUS alleles had been inactivated (Fig. 2F). Here, FUS is linked to amyotrophic lateral sclerosis.