Mutations in Mfn2 cause Charcot-Marie-Tooth type 2A (CMT2A), a peripheral neuropathy affecting sensory and motor neurons (Zuchner et al., 2004), while mutations in OPA1 are the primary cause of autosomal dominant optic atrophy (DOA), a degeneration of retinal ganglia cells that results in atrophy of the optic nerve (Alexander et al., 2000; Delettre et al., 2000). Here, OPA1 is linked to autosomal dominant optic atrophy.