Schematic representation of mitochondrial dynamics. Drp1 in mitochondrial outer membrane forms chains promoting fission. The chain is stabilized by MiD49-Mff/Fis1 and MiD51-Mff/Fis1 complexes. Fusion is mediated by OPA-1 in the mitochondrial inner membrane and by Mfn1 and Mfn2 in the mitochondrial outer membrane. Drp1: dynamin-related protein-1; Fis1: mitochondrial fission protein 1; Mff: mitochondrial fission factor; MiD49: mitochondrial dynamics proteins of 49 kDa; MiD51: mitochondrial dynamic proteins of 51 kDa; OPA-1: optic atrophy 1; Mfn1: mitofusins 1; Mfn2: mitofusins 2.