SOD1 and amyotrophic lateral sclerosis: Patients with C9ORF72 hexanucleotide expansion appear to exhibit a unique functional mitochondrial phenotype: TDP-43, SOD1, and OPTN based ALS models all have depolarized MMP whereas MMP is hyperpolarized in C9ORF72 models (Hong et al., 2012; Wang et al., 2013; Xie et al., 2015; Onesto et al., 2016; Wang P. et al., 2019; Evans and Holzbaur, 2020a; Jun et al., 2020).