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. 2015 Jun 17;24(3):450–454. doi: 10.1038/ejhg.2015.133

Figure 2.

Figure 2

(a) Biochemical measurement of activities of complex II/III, complex IV of the respiratory chain and citrate synthase. Patient fibroblasts show a significant decrease of complex II/III activity. After re-expression of wild-type cDNA in patient fibroblasts, a significant increase in complex II/III activity relative to protein, to citrate synthase as well as to complex IV activity is observed. The activity of complex II/III remained unchanged in control cells. In addition, lentiviral expression of wild-type COQ9 cDNA in fibroblasts of a patient with a disease-causing homozygous variant in COQ2 showed no effect on the activity of complex II/III, demonstrating the specificity of our complementation strategy in the COQ9 patient. (b) Total amount of CoQ10 was measured before and after lentiviral transduction as well as after treatment with CoQ10. Both patient cell lines showed significantly reduced amounts of CoQ10. After transduction patient fibroblasts with a variant in COQ9 showed a significant (about threefold) increase of CoQ10, whereas in control cells and in patient cells suffering from COQ2 deficiency no significant difference could be observed. Treatment with CoQ10 leads to an increase of the total amount of CoQ10 in both patient cell lines. (c) MS/MS chromatograms of fibroblast lysate samples: (1) detected CoQ10 in a control; (2) 6-DMQ10 in a control is not present; (3) low detection of CoQ10 in a COQ9 patient; (4) detection of 6-DMQ10 metabolite in a COQ9 patient. (d) Quantification of the 6-DMQ10 levels in COQ9-mutant fibroblasts before and after viral complementation with wild-type COQ9. The amount of 6-DMQ10 is significantly reduced in COQ9-mutant fibroblasts after transduction. (e) Treatment with CoQ10 in control and patient fibroblasts. Supplementation rescues complex II/III activity in fibroblasts derived from COQ9 and COQ2 patients whereas no differences were measured in control fibroblasts. Statistics: ***P<0.001, **P<0.01 and *P<0.05 relative to control or the indicated condition. All experimental data were obtained in at least three independent experiments.