Drosophila models of human mitochondrial diseases

PROJECT SUMMARY / ABSTRACT Defects in mitochondria are associated with a spectrum of conditions, ranging from metabolic and degenerative diseases to premature aging. Mitochondrial defects are also associated with multiple organ defects, including muscular weakness, cardiac failure, diabetes, renal dysfunction, and hepatic disease. One approach to understanding the physiopathology of mitochondrial diseases is to create animal models that enable detailed mechanistic studies of the underlying perturbations. Drosophila is an established cost-effective model system for studying human diseases, including mitochondrial diseases. Validation of fly models relies on two critical sets of tools: reagents that perturb gene function and reagents that recognize proteins. While perturbation reagents are readily available for nearly all 14,000 Drosophila genes, there are relatively few reagents for detection of fly proteins. Our proposal focuses on generating reagents that will serve as a resource to enable the characterization and validation of Drosophila models of human mitochondrial diseases. We will generate two sets of reagents, based on the target gene structure, for the detection of proteins encoded by 394 high confidence Drosophila orthologs of human mitochondrial disease genes. For Group 1 genes (Aim 1), where all isoforms share the same C-terminus exon, we will insert a NanoTag epitope at the C-terminus of the endogenous gene using CRISPR-based genome engineering. We selected the 3’ end to insert the tag as inserting it at the N terminus could interfere with the mitochondrial localization signal. The resulting protein fusions can then be recognized by an existing high-affinity nanobody against the NanoTag. For Group 2 genes (Aim 2), which encode multiple isoforms, including some with different C-terminus exons, we will use a protein domain common to all isoforms to screen for nanobodies. These reagents will be used together with existing RNAi transgenic lines to validate fly models of human mitochondrial diseases (Aim 3). The resource of nanobodies and fly stocks with NanoTags ‘knocked-in’ to endogenous genes will dramatically expand the scope of available reagents for detection and biochemical characterization of fly mitochondrial proteins.