Excitotoxicity, a key pathomechanism in ALS, has been reported to elicit microglial activation (12); however, it was not known whether the enhanced vulnerability of C9orf72-ALS MNs to excitotoxicity would result from microglial activation in C9orf72-ALS and whether such activation would play a causal role in MN death. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.