C9orf72 and neurodegenerative disease: Many neurodegenerative disease-associated aggregation-prone proteins, such as α-synuclein (13), FUSP525L (14,56), TDP-43 (15), amyloid beta (57), and C9ORF72-associated poly(GR) dipeptide (58), are detected in mitochondria of human patients or disease models and impair mitochondrial functions.