COQ2 and coenzyme Q10 deficiency: In previous studies, we investigated the consequences of varying degrees of CoQ10 deficiency on ROS production, mitochondrial functions, and cell viability in skin fibroblasts with CoQ10 deficiency due to different molecular defects including mutations in COQ2[20], PDSS2[21]–[23], ADCK3 (CABC1) [12], and COQ9[24].