Figure 2.

Impact of positive feedback loops on the cell cycle robustness. (A) Scheme of a toy model for embryonic cell cycle (C, cyclin; M, CDK; X, protease), with positive feedback (PF) loop denoted by the red arrow. (B,C) Deterministic (blue curves) and stochastic (red curves) limit cycle obtained without (B) or with (C) PF loop (see Gonze and Hafner (2010) for details). The dashed, black curve is the steady state of M as a function of C obtained when C is kept constant. (D) Scheme of the skeleton model for the mammalian cell cycle. The red arrows indicated the PFs. (E,G) Stochastic temporal evolution of cyclin E/CDK2 and cyclin B/CDK1 in the absence (E) or presence (G) of PF driving the G1/S and G2/M transitions of the cell cycle. (F,H) Deterministic (red curves) and stochastic (black curves) limit cycle oscillations in the cyclin B/CDK1 vs. cyclin A/CDK2 plot in the absence (F) or presence (H) of PF loops. See Gérard et al. (2012) for details.