C9orf72 and amyotrophic lateral sclerosis: Mitochondrial dysfunction occurs in ALS and contributes to disease progression (Amorim et al, 2022; Delic et al, 2018; Wilson et al, 2023), and cells with ALS pathogenic variants SOD1, C9orf72, and TARDBP (encoding TDP-43 protein) show mitochondrial defects (Van Daele et al, 2023).