C9orf72 and amyotrophic lateral sclerosis: The discovery of a common pathological signature characterized by cytoplasmic accumulation of TDP-43 in sporadic forms of fronto-temporal dementia and ALS, along with the discovery of mutations in TARDBP and C9ORF72 in familial and sporadic forms of these diseases, has become increasingly influential in shaping our understanding of ALS and related disorders3, 4, 5, 6.