Tranfer of calmodulin between cells and calmodulin dependence of nurse cell dumping and embryonic cleavage division. B.F. Andruss , C. Bolduc , D.C. Markesich , K. Beckingham. Department of Biochemistry and Cell Biology, Rice University, 6100 Main St., Houston, TX 77005-1892 (713) 527-8101 ext. 2715.

   Calmodulin (CaM), a primary mediator of calcium signaling, is thought to be essential in all eukaryotic cells. To date, the regulation of developmental processes by calcium/CaM based signaling is largely unexplored. We have used null mutations in the single calmodulin gene (Cam) in Drosophila to generate, for the first time, cells incapable of synthesizing CaM within an intact organism. Surprisingly, these experiments revealed the transfer of CaM into cells in the Drosophila ovary and embryonic CNS. In the ovary, CaM is transfered into Cam null germ-line clones, but not into Cam null clones in the somatic cells of the ovary. In the embryo, CaM is transported into a segmentally repeating pattern of cells late in embryogenesis. This indicates a previously unsuspected ability of CaM to pass across cell membranes. Embryos from Cam null germ-line clones fail to hatch due to early defects in the syncitial nuclear cleavage divisions. Cam null germ line clones also reveal defects in the process of nurse cell cytoplasmic dumping. We will report on the progress of experiments to determine the source and mechanism of CaM transfer and further characterization of the mitotic and cytoplasmic dumping phenotypes.