Mathematical model of a cell size checkpoint.

Area of Science:

• Cell Biology
• Biophysics
• Computational Biology

Background:

• Cell size control is crucial for cell division and organism development.
• A proposed mechanism in fission yeast links cell size to cell cycle via Pom1 and Cdr2 protein distribution.
• Pom1 inhibits Cdr2, which promotes the G2 to M phase transition.

Purpose of the Study:

• To model the molecular mechanism linking cell size and cell cycle regulation in fission yeast.
• To investigate the roles of Pom1 and Cdr2 protein dynamics in cell size control.
• To propose a mechanism involving Cdr2's downstream action on Wee1 phosphorylation.

Main Methods:

• Utilized a deterministic reaction-diffusion-convection system to model protein chemistry.
• Integrated a deterministic model for microtubule dynamics.
• Performed simulations mimicking experimental data from wild-type and mutant fission yeast.

Main Results:

• Simulations accurately reproduced experimental data for wild-type fission yeast under varying growth rates.
• Model behavior matched experimental observations of a Pom1 overexpression mutant.
• Simulations replicated WT yeast responses to microtubule depolymerizing drugs.

Conclusions:

• The study provides a quantitative model for cell size regulation in fission yeast.
• The proposed mechanism highlights the spatial distribution of Pom1 and Cdr2 in controlling cell cycle entry.
• This work offers insights into the downstream effects of Cdr2 on cell division timing.