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The quantification and computer simulation of cytoplasmic flow

 Press Release 

Proceedings of the National Academy of Sciences
of the United States of America (PNAS)

Kimura Laboratory, Cell Architecture Laboratory, Center for Frontier Research

The hydrodynamic property of the cytoplasm is sufficient to mediate cytoplasmic streaming in the Caenorhabiditis elegans embryo.
Ritsuya Niwayama, Kyosuke Shinohara, Akatsuki Kimura.
Proceedings of the National Academy of Sciences of the United States of America (PNAS), 108 (27), 2011.
DOI: 10.1073/pnas.1101853108

Cytoplasmic streaming is a type of intra-cellular transport widely seen in nature. Cytoplasmic streaming in Caenorhabditis elegans at the one-cell stage is bi-directional; the flow near the cortex (“cortical flow”) is oriented toward the anterior, whereas the flow in the central region (“cytoplasmic flow”) is oriented toward the posterior. Both cortical flow and cytoplasmic flow depend on myosin, which primarily localizes in the cortex. The manner in which myosin proteins drive cytoplasmic flow in the opposite direction from remote locations has not been fully understood. In this study, we demonstrated that the hydrodynamic properties of the cytoplasm are sufficient to mediate the forces generated by the cortical myosin to drive bi-directional streaming throughout the cytoplasm. We quantified the flow velocities of cytoplasmic streaming using particle image velocimetry (PIV) and conducted a three-dimensional hydrodynamic simulation using the moving particle semi-implicit method. Our simulation quantitatively reconstructed the quantified flow velocity distribution resolved through PIV analysis. Our results suggest that locally generated force in the cell can be converted into flow and can affect the movements of remote cellular components.

The flow velocity distribution in vivo (left) and that in computer simulation (right) are represented with color.