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Fig. 2 | BMC Systems Biology

Fig. 2

From: Computational analysis reveals the coupling between bistability and the sign of a feedback loop in a TGF-β1 activation model

Fig. 2

Calcium and KLF2 have potential influence on the steady state of TGF-β1 activation. a-b TGF-β1 abundance is plotted over time, after initializing the system from a given set of initial concentrations with (a) low calcium or (b) high calcium. In both cases, curves have been colored blue if they converge to a steady state with low TGF-β1 activation (ssP), and colored red if they converge to a steady state with high TGF-β1 activation (ssT). c Calcium causes a shift in the separatrix between steady states. Low-calcium and high-calcium simulations were performed using various initial concentrations of PLS and TSP1. After observing in Fig. 2a-b that initial conditions with 0.5ssP and 0.5ssT were usually in the basin of convergence for the ssP state (for the low calcium model), we decided to shift the initial conditions. For studying the behavior of the separatrix, the initial concentrations were set to .25*ssP and .75*ssT. The steady state outcomes are shown by colors, with red indicating the steady state with high TGF-β1 (ssT), and blue indicating low TGF-β1 (ssP). For each combination of PLS and TSP1, the low calcium result is indicated by the color of the small inner dot, and the high-calcium result is indicated by the color of the outer circle. d Two steady state (s.s.) levels of TGF-β1 and PAI1 under different levels of KLF2. Red squares represent steady states with high TGF-β1 activation (ssT), while blue dots represent steady states with low TGF-β1 activation (ssP). The y-axis is the log of the steady state concentration of TGF-β1. e Bifurcation analysis under KLF2 low and KLF2 high conditions

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