CENP-E is required for chromosome bi-orientation in meiosis in Drosophila females. Tranchau L. Hoang¹, Sarah J. Radford², Kim S. McKim^1,2. 1) Genetics Department, Rutgers University, Piscataway, NJ; 2) Waksman Institute, Rutgers University, Piscataway, NJ.

   Defects in chromosome segregation in meiosis lead to aneuploidy, which causes the death of embryos or diseases such as Down syndrome, Turners syndrome, and Klinefelters syndrome in humans. For accurate chromosome segregation to occur, chromosomes interact with a bipolar array of microtubules called the spindle. During mitosis, microtubules emanate from the organizing centers at the poles called centrosomes. The microtubules attach to chromosomes at the kinetochores, protein complexes that assemble at the centromeres. These connections facilitate chromosome bi-orientation and accurate segregation. There are no centrosomes in oocytes; therefore, how chromosomes interact with the spindle is not known. CENP-E, a kinesin motor protein at the centromeres, is required for chromosome congression during mitosis. We are testing if CENP-E is required for chromosome bi-orientation during meiosis. The Drosophila melanogaster genome encodes two homologues of CENP-E, which are CANA and CMET. The cana and cmet genes are adjacent to each other in an inverted orientation, suggesting the possibility of recent duplication and redundancy. CENP-E mutants were generated by screening for imprecise excision of a P element, which was inserted between the cana and cmet genes. Even though cmet mutants are lethal, cana mutants are viable and fertile. In CANA-depleted oocytes, chromosomes were oriented properly. However, CMET-depleted oocytes had mis-oriented chromosomes at metaphase I. In addition, oocytes of double cana cmet knock down showed chromosomes with the same mis-orientation defect at metaphase I as in CMET-depleted oocytes. In general, the bipolar spindle looks normal in cana cmet mutant oocytes. These results indicate that CMET but not CANA is required for accurate alignment of chromosomes during meiosis. For future research, we would like to investigate the mechanism and proteins that CMET interacts with to ensure the bi-orientation of chromosomes in meiosis.