Endoplasmic-reticulum-mediated microtubule alignment governs cytoplasmic streaming

Nature Cell Biology 19, 399 (2017).
doi:10.1038/ncb3490

Authors: Kenji Kimura, Alexandre Mamane, Tohru Sasaki, Kohta Sato, Jun Takagi, Ritsuya Niwayama, Lars Hufnagel, Yuta Shimamoto, Jean-François Joanny, Seiichi Uchida & Akatsuki Kimura
Cytoplasmic streaming refers to a collective movement of cytoplasm observed in many cell types. The mechanism of meiotic cytoplasmic streaming (MeiCS) in Caenorhabditis elegans zygotes is puzzling as the direction of the flow is not predefined by cell polarity and occasionally reverses. Here, we demonstrate that the endoplasmic reticulum (ER) network structure is required for the collective flow. Using a combination of RNAi, microscopy and image processing of C. elegans zygotes, we devise a theoretical model, which reproduces and predicts the emergence and reversal of the flow. We propose a positive-feedback mechanism, where a local flow generated along a microtubule is transmitted to neighbouring regions through the ER. This, in turn, aligns microtubules over a broader area to self-organize the collective flow. The proposed model could be applicable to various cytoplasmic streaming phenomena in the absence of predefined polarity. The increased mobility of cortical granules by MeiCS correlates with the efficient exocytosis of the granules to protect the zygotes from osmotic and mechanical stresses.

Source: Nature Cell Biology - March 13, 2017 Category: Cytology Authors: Kenji Kimura Alexandre Mamane Tohru Sasaki Kohta Sato Jun Takagi Ritsuya Niwayama Lars Hufnagel Yuta Shimamoto Jean-Fran çois Joanny Seiichi Uchida Akatsuki Kimura Tags: Letter Source Type: research