DDX3X and frontotemporal dementia: On the other hand, surprisingly, expression of DDX3X reduces endogenous DPR level and mitigates toxicity in C9ALS/FTD patient cells, and silencing of DDX3X enhances GGGGCC repeat-mediated toxicity in Drosophila of C9ALS/FTD (Figure 3; Cheng et al., 2019).