Regime shifts driven by dynamic correlations in gene expression noise
  Gene expression is a noisy process that leads to regime shift between alternative steady states among individual living cells, inducing phenotypic variability. The effects of white noise on the regime shift in bistable systems have been well characterized, however little is known about such effects of colored noise (noise with non-zero correlation time). Here, we show that noise correlation time, by considering a genetic circuit of autoactivation, can have significant effect on the regime shift in gene expression. We demonstrate this theoretically, using stochastic potential, stationary probability density function and first-passage time based on the Fokker-Planck description, where the Ornstein-Uhlenbeck process is used to model colored noise. We find that increase in noise correlation time in degradation rate can induce a regime shift from low to high protein concentration state and enhance the bistable regime, while increase in noise correlation time in basal rate retain the bimodal distribution. We then show how cross-correlated colored noises in basal and degradation rates can induce regime shifts from low to high protein concentration state, but reduce the bistable regime. In addition, we show that early warning indicators can also be used to predict shifts between distinct phenotypic states in gene expression. Predictions that a cell is about to shift to a harmful phenotype could improve early therapeutic intervention in complex human diseases. 
Yogita Sharma and Partha Sharathi Dutta
q-bio.MN nlin.AO q-bio.SC