Likewise, de novo heterozygous mutations can affect DNM1L, encoding a protein with a major role in mitochondrial fission, usually associated with severe, infantile encephalopathy, whereas transmissible, recessive DNM1L mutations cause a form of optic atrophy (OA5) (OMIM *603850) [176]. Here, DNM1L is linked to Leber hereditary optic neuropathy.