Mitochondrial oxidative phosphorylation dysfunction is one of the most common inborn errors of metabolism. However, it is difficult to diagnose and its genetic etiology is often unclear. This proposal's immediate goal is to exploit the nematode C. elegans as a translational model system to enhance the genetic study of mitochondrial disease. The long-term objective is to improve diagnostic capabilities for the heterogeneous subset of human patients with genetic-based mitochondrial disease. Complex I is the largest and most commonly implicated mitochondrial respiratory chain (MRC) complex in human mitochondrial disease. This project will clarify contributions of structural subunits of complex I to integrated mitochondrial function in C. elegans. The proposed approach is based on two hypotheses: 1)Protein components of MRC complexes conserved between C. elegans and humans are critical to proper MRC function;and 2)Consistent patterns of compensatory responses in gene expression occur in the nuclear genome when MRC function is impaired. Specific aims for this proposal are to: 1) Determine which of the evolutionary conserved, nuclear-encoded subunits of complex I are integral to mitochondrial function in C. elegans, and 2) Identify a representative gene expression-based pattern within biologically relevant pathways that is indicative of MRC dysfunction. An RNA interference feeding approach will be used to inhibit expression of conserved complex I subunit nuclear genes. The effect of this disruption will be characterized on mitochondrial function, as assessed by oxidative phosphorylation capacity;on whole organism function as assessed by anesthetic sensitivity, lifespan, and growth rate;and on cellular compensatory mechanisms as assessed by microarray analysis of the entire C. elegans nuclear genome using gene set enrichment analysis of selected biologically-relevant gene clusters. RELEVANCE: Despite increased awareness of the important role mitochondria play in common diseases, such as type II diabetes, to less common inborn errors of metabolism, there is limited ability to pursue definitive genetic diagnoses. C. elegans presents an unparalleled ability to correlate findings of mitochondrial dysfunction to mutations in specific genes, and to suggest gene patterns that may be used to screen or diagnose human mitochondrial disease. Understanding specific genetic causes of mitochondrial disease will provide the basis for rational clinical diagnosis, treatment, and perhaps, cure.