Mutations in NDUFS2 and NDUFS7, orthologs of nduf-2.2/gas-1 and nduf-7, respectively, are associated with mitochondrial Complex I deficiency, which can cause hereditary optic neuropathy (Triepels et al., 1999; Bugiani et al., 2004; Tuppen et al., 2010). Here, NDUFS2 is linked to hereditary optic neuropathy.