C9 and amyotrophic lateral sclerosis: We found an upregulation of microglia-specific genes in C9-ALS-FTSD, substantiating previous findings of microglial dysregulation in cases with this genetic background.17,24 Microglia have been shown to require C9orf72 for normal function in C9orf72−/− microglia and peripheral myeloid cell models, demonstrating a pro-inflammatory response as a result of C9orf72 knockout.22,23 Thus, haploinsufficiency resulting from C9orf72 HRE may lead to the microglial dysregulation observed both in this study and elsewhere.