Similarly, in adult neuronal axons, tight regulation of mitochondrial fission by Drp1 is essential: loss of Drp1 is found to compromise mitochondrial bioenergetics and synaptic function [7], while a role for Drp1 has been suggested in several neurodegenerative diseases including Alzheimer’s disease [8,9], Parkinson’s disease [10] and amyotrophic lateral sclerosis (ALS) [11]. This evidence concerns the gene DNM1L and amyotrophic lateral sclerosis.