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The centrosome-organelle mutual pulling model for centrosome centration.
Press Release PNAS 108 137-142 (2011).
Kimura Laboratory, Cell Architecture Laboratory, Center for Frontier Research
Intracellular organelles mediate cytoplasmic pulling force for centrosome centration in the Caenorhabditis elegans early embryo
Kenji Kimura and Akatsuki Kimura
PNAS 108 137-142 (2011). DOI: 10.1073/pnas.1010929108

  The nucleus and centrosome are generally maintained at the center of the cell. In animal cells, the positioning is powered by the pulling force of microtubules elongating from the centrosome, which is dependent on cytoplasmic dynein. However, it is unclear how dynein brings the nucleus and centrosome to the cell center.

  In this study, we provide evidence that a population of dynein, which is located on intracellular organelles and is responsible for organelle transport toward the centrosome, generates the force required for centrosome centration. By using C. elegans embryos, we found that DYRB-1 (Fig. 1), which belongs to the dynein light chain/roadblock (LC7) family, is selectively involved in centration. DYRB-1 is required for organelle movement toward the minus end of the microtubules (Fig. 2). Centrosome centration was impaired when Rab7 and RILP, which mediate the association between organelles and dynein in mammalian cells, were knocked down. These results indicate that minus end-directed transport of intracellular organelles along the microtubules is required for centrosome centration in C. elegans embryos. On the basis of this finding, we propose a model in which the reaction forces of organelle transport generated along microtubules act as a driving force that pulls the centrosomes toward the cell center (Fig. 3).

Fig. 1. Confocal fluorescence image of C. elegans embryo expressing GFP::DYRB-1. The boxed region is shown magnified (Right). The arrowheads (black and white) indicate both ends of a filamentous signal of GFP::DYRB-1. bar = 5μm
Fig. 2.  Confocal fluorescence image of C. elegans embryo expressing the early endosome (EE) marker GFP::EEA-1(FYVE*2). White arrow indicates the centrosome (CS). Three sequential images of the boxed region are magnified below. A typical example of the movements of EEs for 2 min after pronuclear meeting is illustrated (Right).
Fig. 3.  The centrosome-organelle mutual pulling model for centrosome centration.