Mutant Mid51(Y240N) was recently linked to dominant optic atrophy (Charif et al., 2021) and is located in Mid51’s Drp1-binding region, which led to defective mitochondrial fission/fusion dynamics (Charif et al., 2021) that are dependent on Drp1 GTP hydrolysis, but normal Mid51/Fis1 oligomerization and lysosomal networks. Here, FIS1 is linked to autosomal dominant optic atrophy.