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). This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.