Role of Drosophila 14-3-3/PAR-5 in ring canals. S. Wang, L. Cooley. Dept. Genetics, Yale Univ., New Haven, CT.

   Ring canals are large cytoplasmic bridges that connect the syncytial cells in many organisms including Drosophila. They are believed to originate from contractile rings after arrest of cytokinesis. The ring canals in Drosophila females allow the flow of cytoplasmic components from nurse cells to the oocyte, which helps the oocyte grow and mature. Also during egg chamber growth, the diameters of ring canals increase from less than 1m to 10 m. A loosely packed net of interconnected actin bundles, actin-binding proteins and regulatory proteins such as Src64 and Tec29 supports the ring canals.
   Drosophila 14-3-3/PAR-5 is expressed in germline cells and it is involved in A-P axis formation. 14-3-3 proteins regulate the activity or subcellular localization of many proteins by binding to a conserved phosphorylation-dependent motif. There are two 14-3-3 proteins in Drosophila: 14-3-3 and 14-3-3. Both proteins are slightly enriched at ring canals. We used a null mutation of 14-3-3 to study the role of 14-3-3/PAR-5 in ring canals. We found some of the 15 ring canals were smaller than normal, and the expression pattern of Ovhts-RC, which is another component of ring canals, was affected. We found that there is a 14-3-3 binding motif in the Ovhts sequence. We are investigating whether 14-3-3/PAR-5 binds to Ovhts, and if binding is dependent on phosphorylation of Ovhts.