MFN1 and Atrophy: Mitochondria have double membranes, and their fusion needs fusion of both outer and inner membranes; while optic atrophy mediates inner membrane fusion, mitofusins 1 and 2 (Mfn1 and Mfn2) help in outer membrane fusion, and among the two mitofusins, Mfn2 is considered essential for fusion [8].