SOD1 and amyotrophic lateral sclerosis: Our detection of SOD1 seeding activity in spinal cords and motor cortices of patients with sALS, SOD1 fALS, and C9ORF72 fALS provides evidence that in each ALS type, misfolded SOD1 has prion-like seeding, or self-propagating activity, which might underpin the commonly observed spreading of pathology from localized anatomical sites to other sites within a patient over time.