The (UGGAA)n insertion binds in vitro to serine/arginine-rich splicing factors (SRSFs) 1 and 9, and in vivo to C9ORF72 FTD/ALS-related proteins such as Fused in sarcoma (FUS), heterogeneous nuclear ribonucleoproteins A2/B1 (hnRNP A2/B1) and TDP-43 [12,75,76] (Table 1). Here, FUS is linked to frontotemporal dementia.