Feedbacks, Bifurcations, and Cell Fate Decision-Making in the p53 System

Area of Science:

• Cellular biology
• Systems biology
• Cancer research

Background:

• The p53 transcription factor regulates critical cellular processes like DNA repair, cell cycle arrest, and apoptosis.
• Understanding the p53 network's role in cell fate decisions is crucial for cancer research.

Purpose of the Study:

• To investigate how the p53 network's complex circuitry enables stochastic yet unambiguous cell fate decisions.
• To model the p53 network's dynamics and understand its response to DNA damage.

Main Methods:

• Development of a Markov chain model for the p53 regulatory network.
• Analysis of feedback loops (negative for oscillations, positive for bistability) involving Mdm2, Wip1, and PTEN.
• Bifurcation analysis of the deterministic approximation to identify steady states and limit cycles.

Main Results:

• The model captures recurrent solutions (steady states, limit cycles) reflecting temporal responses of the stochastic system.
• A subcritical Neimark-Sacker bifurcation facilitates direct switching from oscillations to an apoptotic steady state.
• Diverse expression levels of Wip1 and PTEN explain varied cellular responses to DNA damage, from rapid apoptosis to prolonged oscillations.

Conclusions:

• The p53 network's architecture allows for robust cell fate decisions despite inherent stochasticity.
• Bifurcation analysis reveals mechanisms underlying the switch between cell survival (oscillations) and apoptosis.
• The study explains differential responses of cancer cell lines to DNA damage based on specific molecular players like PTEN and Wip1.