In mammalian cells, Opa-1 (optic atrophy), Mitofusin-1, and Mitofusin-2 are the main profusion proteins, while a large GTPase Drp1 (dynamin-related protein) and its different receptors, including Mff (mitochondrial fission factor), Fis1(fission), and mitochondrial dynamic proteins MiD49 and MiD51, regulate mitochondrial fission [105]. The gene discussed is FIS1; the disease is hereditary optic atrophy.