C9orf72 and frontotemporal dementia: In the past few years, there has been increasing evidence for the formation and subsequent gel or aggregate transition of liquid droplets consisting of distinct ALS/FTD-related mutant proteins, including fused in sarcoma (FUS) (35, 36, 37), TAR-DNA-binding protein (TDP-43) (38), heterogeneous ribonucleoprotein A1 (hnRNPA1) (39), and Tau (40), as well as dipeptide repeat proteins derived from the C9orf72 gene (41, 42).