In AD, mitochondrial fission is promoted by increased levels of pro-fission proteins dynamin-related protein 1 (Drp1) and mitochondrial fission 1 protein (Fis1) and decreased levels of the pro-fusion proteins optic atrophy type 1 (Opa1), mitofusin 1 and 2 (Mfn1, Mfn2) [80]. The gene discussed is MFN1; the disease is Alzheimer disease.