Treatment of mutant FUS iPSC-derived sMNs with PP2A or GSK3 inhibitors rescued hallmark ALS phenotypes, such as cytoplasmic mislocalization of FUS, reduced NMJ formation and mitochondrial transport defects, further supporting our finding that PP2A and GSK3 are modifiers of FUS toxicity. The gene discussed is PTPA; the disease is amyotrophic lateral sclerosis.