MCJ is a mitochondrial inner membrane protein and a natural inhibitor of respiratory chain Complex I. Colitis-induced MCJ-deficient mice showed higher expression of Myd88 and Tlr9proinflammatory genes, and disease severity was associated with distinct microbiota metabolism and composition (including R. gnavus) and elevated IgA levels (Pascual-Itoiz et al. 2020). The gene discussed is DNAJC15; the disease is colitis.