Loss of the mitochondrial matrix protein Shaken not Stirring causes bang-sensitivity and early adult lethality. Daniel K. Bricker^1,3, Jon Van Vranken^2,3, Kelly J. Beumer^2,3, Dana Carroll^2,3, Jared Rutter^2,3, Carl S. Thummel^1,3. 1) Department of Human Genetics; 2) Department of Biochemistry; 3) University of Utah School of Medicine, Salt Lake City, UT.

   Mitochondria are complex organelles that have important roles in energy production, intermediary metabolism, signal transduction and apoptosis. Consistent with these activities, mitochondrial dysfunction is associated with a wide range of human diseases, including myopathies, cancers and neurodegenerative disorders. Given these critical cellular functions and links to disease, major efforts have been made to determine the identity of all mitochondrial proteins. The most comprehensive study to date identified 1200 proteins in the mouse mitochondrial proteome. Remarkably, about one fifth of these proteins have unknown functions. Moreover, many are represented by one or a few genes in most species, ranging from yeast to humans, suggesting they have a critical function maintained through evolution. We are characterizing a subset of these evolutionarily-conserved genes through a collaborative effort in both flies and yeast. Our current studies are focused on a protein that we have named Shaken not Stirring (SST) in Drosophila melanogaster. The yeast ortholog of sst encodes a mitochondrial matrix protein that is required for growth on media containing acetate. This phenotype can be complemented by expression of either the fly or human orthologs of the gene, indicating an evolutionarily-conserved function. Mutations in Drosophila sst have been generated using transcriptional activator like effector nucleases (TALENs) and by imprecise excision of a P-element. These null mutants are viable, but display a severely reduced lifespan under normal laboratory conditions. Interestingly, sst mutants are sensitive to paralytic seizures caused by mechanical stress, a classic phenotype termed bang sensitivity. This phenotype is closely associated with neuronal dysfunction and neurodegeneration. We are currently determining how SST maintains neuronal function through a combination of metabolomic analysis and a detailed examination of mitochondrial function in sst mutants.