To better understand the contribution of microglial cells to C9orf72 ALS/FTD, we used an endogenous human in vitro cell culture model by differentiating mutant C9orf72 ALS/FTD patient-derived induced pluripotent stem cells into microglia (iPSC-MG). The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.