Centrosomes are the major microtubule organizing centers of animal cells and play a critical role in mitosis to organize the mitotic spindle and orchestrate chromosome segregation. The two centrosomes present at the onset of mitosis must separate in a timely and accurate fashion along the surface of the nucleus to ensure proper bipolar spindle assembly.
The microtubule-associated motor dynein plays a pivotal role in centrosome separation, but the underlying mechanisms remain elusive, particularly regarding how dynein coordinates this process in space and time. Where in the cell do motors act to separate centrosomes? How are forces organized to bring centrosomes in opposite directions? And how robust is this process?
To address these questions, we have dissected centrosome separation in the C.elegans one-cell stage embryo. We have quantitatively measured and modeled centrosome separation using a combination of 3D fluorescence time-lapse microscopy, image processing and computational modeling. Our analysis reveals that centrosome separation is powered by the joint action of dynein at the nuclear envelope and at the cell cortex. Strikingly, we demonstrate that dynein at the cell cortex acts as a force-transmitting device that harnesses polarized actomyosin cortical flows initiated by the centrosomes earlier in the cell cycle. This novel mechanism elegantly couples cell polarization with centrosome separation, thus ensuring faithful cell division.