Defects in NDUFS4 are a major cause of CI deficiency-associated mitochondrial disease in humans (Ortigoza-Escobar et al., 2016) and the mouse and D. melanogaster animal models display CI deficiency and pathological phenotypes (Kruse et al., 2008; Foriel et al., 2018). The gene discussed is NDUFS4; the disease is inborn mitochondrial metabolism disorder.