Geometric Control of Cytoplasmic Streaming in the Drosophila Oocyte

This work probes the role of geometry in orienting self-organized fluid flows in the late stage Drosophila oocyte. Recent work has shown that a theoretical model, which relies only on hydrodynamic interactions of flexible, cortically anchored microtubules (MTs) and the mechanical loads from kinesin motors moving upon them, is sufficient to generate observed flows. While the emergence of flows has been computationally studied in spheres, actual late-stage oocytes are ellipsoidal.

This work uses novel experimental techniques to show a geometric dependence on flow direction in late-stage oocytes. The experiments are supplemented with simulations that confirm the role of geometry in breaking the symmetry of the system and setting a direction for the flow. The simulations suggest that MT elastic energy minimization under motor-protein load may help choose the observed flow orientation around the axis of an ellipsoidal cell. The orientation of the flow has biological consequences for transport and mixing, which are critical for healthy oocyte development.