A final group of ALS-FTD-related genes have no known relation to RNA metabolism: SOD1 (Rosen et al. 1993), GRN, which encodes progranulin (Baker et al. 2006; Cruts et al. 2006), and TBK1 (Freischmidt et al. 2015). Here, SOD1 is linked to frontotemporal dementia.