Discovering new genes required for mitosis and meiosis by analysis of interactions with the kinesin Subito. Daniel J. DiSanto, Arunika Das, Kim S. McKim. Waksman Institute, Rutgers University, Piscataway, NJ.

   Accurate segregation of chromosomes during meiosis and mitosis is essential to an organisms growth and development. We are interested in chromosome segregation during Drosophila female meiosis, which differs from mitosis and male meiosis in that it does not use centrosomes as microtubule organizing centers. Since these processes are so similar, many of the proteins involved in mitosis are also used during meiosis. Taking advantage of this fact, we devised a genetic screen to select for mutants that enhanced the mitotic phenotype of a homozygous null subito (sub) mutant (synthetic lethality). Subito is a kinesin-6 protein used during both mitosis and meiosis that associates with and may bundle anti-parallel microtubules. Subito null mutants are viable but build defective mitotic spindles. By screening for synthetic lethal mutants in a sub null background, we isolated 17 mutations in genes that may function in the same pathway as Subito. Five of these mutants are alleles of Incenp and ial, genes previously known to be synthetic lethal with sub (including one homozygous viable Incenp allele). We are studying one of the new mutations isolated in the EMS screen, currently referred to as 27.89. Since 27.89 is homozygous lethal, germline clones were generated to view its phenotype during meiosis in stage 14 oocytes. 27.89 clones failed to develop mature oocytes, a phenotype of genes essential for the germline mitotic cell divisions such as Incenp and ial. Using a combination of genetic mapping and whole genome sequencing we will identify the 27.89 gene. This will reveal why it exhibits synthetic lethality with sub and what role it plays in meiosis.