Principal Investigator Joern Dunkel
Symmetry-breaking transitions play a crucial role in the embryonic development of higher organisms, resulting in complex body shapes characterized by front-back, left-right and top-bottom asymmetry. In the fruit fly Drosophila, the anterior-posterior axis is laid out during egg formation (oogenesis) through localization of bicoid and oskar mRNAs to the anterior and posterior poles of the oocyte, respectively. This mRNA localization is believed to be dominated by motor-driven transport on a weakly polarized microtubule cytoskeleton, but how the noncentrosomal microtubule cytoskeleton is organised in three dimensions, is not known. To understand better the effect of cytoskeletal architure on diffusive, hydrodynamic and motor-driven mRNA transport, we have developed a detailed theoretical model for stage 9 oocytes. Based on observed cortical microtubule nucleation densities, this experimentally constrained model provides a fully three-dimensional description of cytoskeleton, cytoplasmic flows and cargo transport that accurately reproduces mRNA localizations in wild-type oocytes and mutants. Our analysis suggests that the architecture of the microtubule cytoskeleton in Drosophila oocytes is more ordered than previously thought.