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Updated: Sep 29, 2026
Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
Reorganization of the microtubule array in prophase/prometaphase requires cytoplasmic dynein-dependent microtubule
Nasser M Rusan1, U Serdar Tulu, Carey Fagerstrom
1Department of Biology, Program in Molecular and Cellular Biology, Morrill Science Center, University of Massachusetts, N. Pleasant Street, Amherst, MA 01003, USA.
Abstract:
When mammalian somatic cells enter mitosis, a fundamental reorganization of the Mt cytoskeleton occurs that is characterized by the loss of the extensive interphase Mt array and the formation of a bipolar mitotic spindle. Microtubules in cells stably expressing GFP-alpha-tubulin were directly observed from prophase to just after nuclear envelope breakdown (NEBD) in early prometaphase. Our results demonstrate a transient stimulation of individual Mt dynamic turnover and the formation and inward motion of microtubule bundles in these cells. Motion of microtubule bundles was inhibited after antibody-mediated inhibition of cytoplasmic dynein/dynactin, but was not inhibited after inhibition of the kinesin-related motor Eg5 or myosin II. In metaphase cells, assembly of small foci of Mts was detected at sites distant from the spindle; these Mts were also moved inward. We propose that cytoplasmic dynein-dependent inward motion of Mts functions to remove Mts from the cytoplasm at prophase and from the peripheral cytoplasm through metaphase. The data demonstrate that dynamic astral Mts search the cytoplasm for other Mts, as well as chromosomes, in mitotic cells.
Insights
During mitosis, microtubules reorganize. Researchers observed dynamic microtubule (Mt) behavior, finding inward motion of Mt bundles is driven by cytoplasmic dynein, aiding cellular reorganization.
Area of Science:
- Cell Biology
- Cytoskeleton Dynamics
- Mitosis
Background:
- Mammalian somatic cells undergo significant cytoskeletal reorganization during mitosis.
- The interphase microtubule (Mt) array is lost and a bipolar mitotic spindle forms.
- Understanding microtubule dynamics is crucial for comprehending mitotic progression.
Purpose of the Study:
- To directly observe microtubule behavior during early mitosis.
- To investigate the forces driving microtubule reorganization.
- To elucidate the role of motor proteins in microtubule dynamics during mitosis.
Main Methods:
- Live-cell imaging of microtubules using GFP-alpha-tubulin in mammalian cells.
- Observation from prophase through early prometaphase (after nuclear envelope breakdown).
- Functional inhibition of motor proteins (cytoplasmic dynein/dynactin, Eg5, myosin II) using antibodies.
Main Results:
- A transient increase in individual microtubule turnover was observed.
- Formation and inward motion of microtubule bundles occurred.
- Inward motion of microtubule bundles was dependent on cytoplasmic dynein/dynactin but not Eg5 or myosin II.
- Dynamic astral microtubules were observed searching the cytoplasm for other microtubules and chromosomes.
Conclusions:
- Cytoplasmic dynein-dependent inward microtubule motion helps clear microtubules from the cytoplasm during prophase and metaphase.
- Dynamic astral microtubules actively search cellular compartments during mitosis.
- These findings provide insight into the active mechanisms governing microtubule organization during cell division.
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