Characterizing the genetic basis for mitochondrial shaping defects in emmenthal mutants of Drosophila melanogaster. Will S. Mitchell, Karen G. Hales. Department of Biology, Davidson College, Davidson, NC.

   The regulation of mitochondrial dynamics in many organisms and cell types is important to viability and involves the highly specific and choreographed interactions of many gene products. A recessive male sterile mutation in Drosophila melanogaster, emmenthal, is associated with meiotic cytokinesis failure, vacuolated Nebenkerne (mitochondrial aggregates) and non-motile sperm. The emmenthal mutation was generated in a P-element insertion screen (Castrillon et al., 1993, Genetics 135: 489). The P-element insertion site was located using plasmid rescue and found to be among a cluster of genes with similar temporal and spatial expression in the Drosophila testis, though the insertion was not within any one gene. Initial RT-PCR analysis suggested that this insertion causes altered gene expression of a subset of these genes, which have no characterized homologs in other organisms and which have no recognizable protein domains. At least two of these genes appear to be transcribed in a polycistronic mRNA. The genes associated with the emmenthal phenotype may thus represent novel functions vital for mitochondrial regulation.