Metabolic profiling of the coenzyme Q10 biosynthesis pathway

• Applicant: Professor Dr. Felix Distelmaier
• Subject Area: Pediatric and Adolescent Medicine
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 350198170

During the second funding period of the project, we combined, clinical, genetic and biochemical research to characterize several inherited defects of coenzyme Q10 (CoQ10) biosynthesis. One subproject focused on human COQ4-deficiency. We analyzed a large cohort of 44 pediatric patients regarding clinical phenotype, abnormalities on brain imaging, and response to CoQ10 treatment. Using patient-derived COQ4 fibroblast lines we performed detailed biochemical analyses including measurements of CoQ10 levels and metabolic CoQ-intermediates as well as quantification of CoQ10-biosynthesis enzymes on the protein level. We demonstrated distinct clinical subtypes in COQ4 deficiency and established 6-demethoxy-ubiquinon10 (6-DMQ) as a reliable biochemical marker substance in fibroblasts. Another subproject focused on human COQ8A deficiency. We participated in a large cohort study of 59 individuals to delineate the genetic spectrum, the clinical phenotypes and the metabolic abnormalities of this disorder. COQ8A-deficiency presented as an early-onset cerebellar ataxia with cerebellar atrophy as a key feature on brain imaging. Investigations of skin fibroblasts didn’t show significant alterations in biochemical and mitochondrial function parameters indicating the need for other cellular model systems. In continuation of the abovementioned projects, we applied iPSC (induced pluripotent stem cell) technology and CRISPR/Cas9 engineering to develop a neuronal model system of COQ4-deficiency. A similar approach will be undertaken for human COQ8A-deficiency. In the following, we will investigate the influence of COQ4 and COQ8A-deficiency on mitochondrial function parameters and neuronal morphogenesis in neural cultures and brain organoids. In addition, a new subproject was developed, which is dedicated to the impact of CoQ10 biosynthesis defects on the assembly and stability of respiratory chain supercomplexes. Preliminary results indicate that supercomplexes in COQ4-deficient cells have markedly reduced amounts of complex IV (cytochrome c oxidase). This was not the case for other CoQ10 biosynthesis defect and further research is ongoing to elucidate this phenomenon. Furthermore, another subproject was developed to investigate human HPDL (4-hydroxyphenylpyruvate dioxygenase like) deficiency. HPDL-deficiency causes a childhood-onset disorder with progressive neurodegeneration and variable clinical course. Only recently, HPDL was identified as a CoQ10 biosynthesis enzyme. During the current project we will perform metabolic analyzes in patient-derived cell lines using UPLC-MS/MS technology as well as several other experimental approaches.Taken together, we were able to show that the DFG-funded CoQ10-biosynthesis project is productive and successful. Therefore, we hope to obtain an extension of the funding period to further advance this project.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Diran Herebian