In order to recover CI function, we took advantage of the previously characterized osteosarcoma cell models (OS-93) bearing the quasi-homoplasmic disruptive m.3571insC mutation in the MT-ND1 gene, which encodes the NADH dehydrogenase subunit 1 (ND1) of CI [14,15] (Additional file 5: Figure S3A). The gene discussed is MT-ND1; the disease is osteosarcoma.