The identification of TDP-43 as an important protein in ALS pathogenesis directly triggered the discovery of ALS and FTD causing mutations in another RNA-/DNA-binding protein called Fused in Sarcoma (FUS) (Kwiatkowski et al., 2009; Vance et al., 2009; Blair et al., 2010; Damme et al., 2010). The gene discussed is FUS; the disease is frontotemporal dementia.