MT-ATP6 and mitochondrial DNA depletion syndrome: BNGE analysis of mitochondria from patients' fibroblasts confirmed the presence of the F1 subcomplexes (x, y, and z) that were previously reported in Rho0 cells, patient-derived mutant MT-ATP6 cell lines, and mtDNA depletion syndrome (figure 2A).4,14 The presence of fully assembled complex V, with detectable ATP6, in the patients' fibroblasts and skeletal muscle, is consistent with the heteroplasmic state of the MT-ATP6 mutations (P1 27%, P3 45% mutant loads in fibroblasts; P2 71% and P3 65% in the muscle; figure 2, C and D).