Isolated complex I (CI) deficiencies are a major cause of primary mitochondrial disease. A substantial proportion of CI deficiencies are believed to arise from defects in CI assembly factors (CIAFs) that are not part of the CI holoenzyme. The biochemistry of these CIAFs is poorly defined, making their role in CI assembly unclear, and confounding interpretation of potential disease-causing genetic variants. To address these challenges, we devised a deep mutational scanning approach to systematically assess the function of thousands of NDUFAF6 genetic variants. Guided by these data, biochemical analyses and cross-linking mass spectrometry, we discovered that the CIAF NDUFAF6 facilitates incorporation of NDUFS8 into CI and reveal that NDUFS8 overexpression rectifies NDUFAF6 deficiency. Our data further provide experimental support of pathogenicity for seven novel NDUFAF6 variants associated with human pathology and introduce functional evidence for over 5,000 additional variants. Overall, our work defines the molecular function of NDUFAF6 and provides a clinical resource for aiding diagnosis of NDUFAF6-related diseases.
FörderungenNIH Roadmap for Medical Research NIH BJC Investigator Program NIHR Wellcome Centre for Mitochondrial Research Mitochondrial Disease Patient Cohort grant Medical Research Council International Centre for Genomic Medicine in Neuromuscular Disease Practical Research Project for Rare/Intractable Diseases from the Japan Agency for Medical Research and Development Italian Ministry of Health German Federal Ministry of Education and Research European Joint Programme on Rare Diseases project GENOMIT NCI Cancer Center Support Grant Siteman Cancer Center from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH) U.S. Department of Health & Human Services | NIH | National Institute of General Medical Sciences (NIGMS)