We previously found that motor neurons derived from mutant C9orf72 and SOD1 expressing induced pluripotent stem cells (iPSCs) exhibit insoluble protein burden and do not robustly activate the heat shock response to exogenous cellular stressors [13, 14] suggesting that ALS iPSC-derived motor neurons may lack sufficient processes to deal with insoluble protein. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.