title: Endoplasmic-reticulum-mediated microtubule alignment governs cytoplasmic streaming.
abstract: 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.
authors.affiliation: Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima 411-8540, Japan.|Department of Genetics, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Mishima 411-8540, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kimura
authors.affiliation: Physicochimie Curie (Centre National de la Recherche Scientifique-UMR168, UPMC), Institut Curie, PSL Research University, Section de Recherche, Paris 75248, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mamane
authors.affiliation: Human Interface Laboratory, Department of Advanced Information Technology, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Human Interface Laboratory, Department of Advanced Information Technology, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Kohta
authors.initials: K
authors.lastname: Sato
authors.affiliation: Quantitative Mechanobiology Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima 411-8540, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Takagi
authors.affiliation: Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima 411-8540, Japan.|Department of Genetics, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Mishima 411-8540, Japan.
authors.forename: Ritsuya
authors.initials: R
authors.lastname: Niwayama
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Hufnagel
authors.affiliation: Department of Genetics, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Mishima 411-8540, Japan.|Quantitative Mechanobiology Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima 411-8540, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shimamoto
authors.affiliation: Physicochimie Curie (Centre National de la Recherche Scientifique-UMR168, UPMC), Institut Curie, PSL Research University, Section de Recherche, Paris 75248, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Joanny
authors.affiliation: Human Interface Laboratory, Department of Advanced Information Technology, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Uchida
authors.affiliation: Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima 411-8540, Japan.|Department of Genetics, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Mishima 411-8540, Japan.
authors.forename: Akatsuki
authors.identifier: 0000-0003-4227-4811
authors.initials: A
authors.lastname: Kimura
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism; D003595:Cytoplasmic Streaming; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057446:Hydrodynamics; D018613:Microscopy, Confocal; D008870:Microtubules / Q000378:metabolism*; D034622:RNA Interference; D059008:Time-Lapse Imaging; D014982:Xenopus laevis; D015053:Zygote / Q000378:metabolism
chemical_list: D049452:Green Fluorescent Proteins