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Updated: May 29, 2026
10:52
Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
Organization of the smallest eukaryotic spindle
Lu Gan1, Mark S Ladinsky, Grant J Jensen
1Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
Current Biology : CB
|September 13, 2011
Summary
In the smallest eukaryote, Ostreococcus tauri, mitosis involves fewer spindle microtubules than chromosomes. This suggests chromosomes are physically linked and segregated in groups, challenging typical spindle checkpoint models.
Area of Science:
- Cell Biology
- Eukaryotic Cell Division
- Microbiology
Background:
- The spindle checkpoint ensures accurate chromosome segregation by monitoring kinetochore microtubule (kMT) attachment.
- Some unicellular eukaryotes challenge this model with fewer kMTs than chromosomes, raising questions about checkpoint satisfaction.
- Previous studies often used chemical fixation, potentially compromising visualization of dynamic spindle structures.
Purpose of the Study:
- To investigate the spindle microtubule organization during mitosis in Ostreococcus tauri, the smallest known eukaryote.
- To determine how the spindle checkpoint functions in O. tauri given its unique cellular structure.
- To resolve conflicting previous reports on microtubule-kinetochore attachments in unicellular eukaryotes.
Main Methods:
- Enrichment of mitotic cells from Ostreococcus tauri cultures.
- High-pressure freezing for sample preservation.
- 3D electron tomography imaging in both plastic and frozen-hydrated states.
Main Results:
- Ostreococcus tauri exhibits mitosis with fewer spindle microtubules than chromosomes.
- A distinctive intranuclear "spindle tunnel" contains incomplete microtubules at each end.
- The spindle checkpoint appears functional despite the unusual microtubule configuration.
Conclusions:
- Ostreococcus tauri's mitotic process involves approximately four short, incomplete microtubules per spindle pole.
- These findings suggest O. tauri's 20 chromosomes are physically linked and segregate as a small number of groups.
- This challenges conventional understanding of spindle checkpoint satisfaction in eukaryotes.
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