We also confirmed the interaction of FUS with the G4C2 repeat RNA in our C9-ALS/FTD flies by showing the colocalization of FUS with the RNA foci (Figure 5—figure supplement 1), consistent with a recent study using C9-ALS/FTD patient fibroblasts (Bajc Česnik et al., 2019). Here, C9 is linked to amyotrophic lateral sclerosis.