Spatial heterogeneity accelerates phase-to-trigger wave transitions in frog egg extracts.

Area of Science:

• Cell Biology
• Developmental Biology
• Biophysics

Background:

• Cell cycle progression is regulated by cyclin-dependent kinase 1 (Cdk1) activity, exhibiting cyclical oscillations.
• Synchronous cell divisions in large early embryos require long-range coordination mechanisms beyond simple diffusion.
• Mitotic waves, including phase and trigger waves, have been proposed to explain this coordination, but their dynamic establishment is unclear.

Purpose of the Study:

• To investigate the dynamic establishment and relationship between phase and trigger waves in coordinating cell cycle oscillations.
• To elucidate the mechanisms underlying long-range cell cycle synchronization in early embryonic systems.

Main Methods:

• Utilized Xenopus laevis egg extracts for in vitro experiments.
• Employed a Cdk1 Förster resonance energy transfer (FRET) sensor to monitor Cdk1 activity dynamics.
• Incorporated numerical simulations to model wave propagation and entrainment dynamics.

Main Results:

• Observed a transition from phase wave to trigger wave dynamics in homogeneous Xenopus egg extracts.
• Demonstrated that spatial heterogeneity and the presence of nuclei accelerate the entrainment process.
• Numerical simulations indicated that phase waves are transient precursors to the more stable trigger waves.

Conclusions:

• Phase and trigger waves represent distinct but interconnected stages within a single biological process for long-range cell cycle coordination.
• The transition dynamics are crucial for establishing synchronized cell divisions in large cellular systems.
• This work provides a unified understanding of wave-based mechanisms coordinating cell cycle progression.