Oocyte nuclear defects are prevalent in swallow mutants. R. Wing, N.J. Pokrywka. Department of Biology, Vassar College, Poughkeepsie, NY.

   Swallow (swa) encodes a novel protein implicated in RNA localization and cytoskeletal organization during oogenesis. Swallow is required for the localization of several RNAs to both the anterior and posterior poles of late stage oocytes, and may interact with elements of the microtubule cytoskeleton in oocytes and early embryos. We have identified a genetic interaction between swallow and maternal alpha tubulin 67C, implying swallow may also play a role in female meiosis. We have used propidium iodide staining to examine the effect of seven swallow alleles on oocyte nuclear positioning and nuclear morphology. In wildtype oocytes, the oocyte nucleus occupies an anterior-dorsal position in mature oocytes, and is arrested in metaphase I of meiosis. Swallow mutants show increased variation in nuclear position along the length axis of the oocyte when compared to wild type. In addition, propidium iodide staining has revealed several morphological abnormalities in swallow oocyte nuclei including precocious nuclear division with occasional anaphase bridges.