C9 and amyotrophic lateral sclerosis: As a comparison, we obtained iPSCs from ALS patients with repeat expansions in C9orf72 (C9-ALS), who are also known to develop TDP-43 pathology (DeJesus-Hernandez et al., 2011), and with mutations in SOD1 (SOD1-ALS), which results in mitochondrial damage without any evidence of TDP-43 pathology (Mackenzie et al., 2007; Tan et al., 2007).