Centripetal nuclear shape fluctuations associate with chromatin condensation in early prophase

Area of Science:

• Cell Biology
• Biophysics
• Molecular and Cellular Biology

Background:

• The nucleus is crucial for cellular processes like DNA replication and transcription.
• Emerging evidence links nuclear mechanics to cell-cycle progression, but this relationship needs further exploration.

Purpose of the Study:

• To investigate the dynamic changes in nuclear shape during the cell cycle.
• To explore the mechanical interplay between chromatin condensation and nuclear envelope breakdown during mitosis.

Main Methods:

• Monitoring nuclear shape fluctuations across different cell cycle stages.
• Perturbing chromatin and cytoskeletal structures to assess their impact on nuclear deformations.

Main Results:

• Observed increasing inward nuclear shape fluctuations in late G2 and early prophase.
• These fluctuations become instabilities approaching nuclear envelope breakdown.
• Nuclear deformations were found to correlate with chromatin condensation.

Conclusions:

• A mechanical link between chromatin condensation and nuclear envelope breakdown is proposed.
• Contrasting forces, including extensile stress and centripetal pulling from chromatin condensation, may mediate this link during mitosis.