MFN1 and amyotrophic lateral sclerosis: In ALS caused by SOD1, increased DRP1 and reduced Mfn1/Opa1 lead to higher level of mitochondrial fission and a fragmented mitochondrial network; while in ALS related to C9ORF72 mutation, higher Mfn1 levels triggered increased mitochondrial fusion and an elongated morphology [119].