NDUFS4 and Leigh syndrome: Loss-of-function mutations in NDUFS4 leads to complex-I deficiency causing a neuromuscular disease, Leigh syndrome (Leshinsky-Silver et al., 2009) and is also involved in cardiomyopathies (Chouchani et al., 2014; Karamanlidis et al., 2013; Zhang et al., 2018).