The importance of mitochondrial fusion to human health is underscored by the findings that mutations in the mitochondrial fusion machinery components Mfn2 and OPA1 cause Charcot-Marie-Tooth disease type 2A and autosomal dominant optic atrophy, respectively (Zuchner et al., 2004; Alexander et al., 2000; Delettre et al., 2000). The gene discussed is OPA1; the disease is Charcot-Marie-Tooth disease type 2A1.