Mutations in genes encoding RNA binding proteins such as the TAR DNA binding protein of 43 kDa (TDP-43; Sreedharan et al., 2008) and Fused-in-sarcoma (FUS; Kwiatkowski et al., 2009) causes familial ALS, and these mutant proteins are found both in neuronal cytoplasmic inclusions of ALS patients and those with the most common pathological phenotype of FTD, namely frontotemporal lobar degeneration (FTLD; Neumann et al., 2006; Mackenzie et al., 2010). Here, FUS is linked to frontotemporal dementia.