C9orf72 and amyotrophic lateral sclerosis: The most common of these mutations are inthe C9orf72, SOD1, TARDBP(TDP) and FUS genes, which have multisystem effects.11 These risk genes are preferentially expressed by motor neurons, which aretargeted in ALS, but they are also expressed by non-neuronal cells at the BCNSB,including astrocytes and microglia.12,13 As sALS and fALS arephenotypically and pathologically indistinguishable, generalisable conclusions canbe drawn from studies of fALS.