Indeed, MTFP1 ablation significantly impacts mitochondrial respiration in the adult heart but not in highly glycolytic epithelial cells such as MEFs (Fig. S2k–n) and human osteosarcoma cells (U2OS) (Fig. S2o–r) or even immortalized HL-1 cardiomyocytes (Fig. S5g–j), highlighting the unique bioenergetic profile and demands of primary adult cardiomyocytes. The gene discussed is MTFP1; the disease is osteosarcoma.