Cortex-driven cytoplasmic flows in elongated cells

The Drosophila melanogaster embryo, an elongated multinucleated cell, is a classical model system for eukaryotic development and morphogenesis. Recent work has shown that bulk cytoplasmic flows, driven by cortical contractions along the walls of the embryo, enable the uniform spreading of nuclei along the anterior-posterior (AP) axis necessary for proper embryonic development. Here we first use mathematical modelling to develop analytical solutions for the cytoplasmic flows driven by tangential cortical contractions in elongated cells. We then apply our results to recent experiments on nuclear transport in cell cycles 4-6 of Drosophila embryo development. By fitting the cortical contractions in our model to measurements, we reveal numerically and theoretically that experimental cortical flows enable near-optimal axial spreading of nuclei.