Although both loss-of-function and gain-of-function hypotheses for FUS dysfunction in ALS have been proposed, a loss of function in RNA regulation and a toxic gain of function at synapses are suggested (Sephton and Yu, 2015; Ishigaki and Sobue, 2018; López-Erauskin et al., 2018). The gene discussed is FUS; the disease is amyotrophic lateral sclerosis.