Clathrin is required for the function of the mitotic spindle

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Clathrin is essential for vesicle formation and intracellular transport in non-dividing cells.
• During mitosis, clathrin relocates from vesicle formation to the spindle apparatus.
• The precise role of clathrin during mitosis remained largely uncharacterized.

Purpose of the Study:

• To investigate the function of clathrin during mitosis.
• To determine how clathrin interacts with the mitotic spindle.
• To elucidate the structural requirements for clathrin's mitotic function.

Main Methods:

• RNA interference (RNAi) to deplete clathrin heavy chain.
• Microscopy to observe mitotic progression and chromosome congression.
• Functional rescue experiments using clathrin constructs.

Main Results:

• Clathrin directly binds to the mitotic spindle via its amino-terminal domain.
• Depletion of clathrin heavy chain destabilizes kinetochore fibers, impairing chromosome congression.
• Mitotic duration is prolonged, and the spindle assembly checkpoint is persistently activated upon clathrin depletion.
• Full-length clathrin triskelia, but not the N-terminal domain alone, rescued normal mitosis, highlighting the importance of clathrin's structure.

Conclusions:

• Clathrin is a critical structural component of the mitotic spindle, stabilizing kinetochore fibers for accurate chromosome segregation.
• Clathrin's role in mitosis is independent of its canonical vesicle-coating function and relies on its specific structural integrity.
• Dysregulation of clathrin during mitosis may contribute to chromosomal instability and has implications for understanding cancers with clathrin gene fusions.