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BP: Fachverband Biologische Physik

BP 27: Posters: Complex Fluids and Soft Matter

BP 27.8: Poster

Tuesday, March 17, 2015, 14:00–16:00, Poster A

The mechanical properties of early Drosophila embryos measured by high-speed video microrheology — •Alok Daniel Wessel and Christoph F. Schmidt — Drittes Physikalisches Institut, Georg-August-Universität Göttingen

In early development, Drosophila melanogaster embryos form a syncytium, i.e. multiplying nuclei are not yet separated by cell membranes, but are interconnected by cytoskeletal polymer networks consisting of actin and microtubules. Between division cycles 9 and 13, nuclei and cytoskeleton form a 2D cortical layer. To probe the mechanical properties and dynamics of this self-organizing "pre-tissue", we measured shear moduli in the embryo by high-speed video microrheology. We recorded position fluctuations of injected micron-sized fluorescent beads with kHz sampling frequencies and characterized the viscoelasticity of the embryo in different locations. Between nuclear layer and yolk the cytoplasm was homogeneous and viscously-dominated, with a viscosity three orders of magnitude higher than that of water. Within the nuclear layer we found an increase of the elastic and viscous moduli consistent with an increased microtubule density. Drug-interference experiments showed that microtubules contribute to the measured viscoelasticity inside the embryo whereas actin only plays a minor role. Myosin inhibition had only minor effects on the probe particle's fluctuation. Measurements at different stages of the nuclear division cycle showed little variation, besides at anphase where we observe directed motion.