For ALS, evidence from cell culture has suggested spread from cell-to-cell from the dipeptide repeat (DPR) proteins encoded by hexanucleotide expansion in C9orf72 [19, 20] and seeding and spread of SOD1 have also been reported with mutant SOD1 transgenic mice [21–24]. Here, SOD1 is linked to amyotrophic lateral sclerosis.