Synthetic signaling circuits provide a versatile framework for programming contact-dependent cell behaviors, yet their collective dynamics are strongly shaped by cell density and processing delay. In this work, we studied a reduced delay differential model motivated by synNotch-type signaling with density-dependent attenuation and adaptive inhibition. The analysis was organized along two complementary routes. First, the equilibrium structure was characterized through a density-driven saddle-node bifurcation analysis, which identified the emergence of a three-equilibrium region and, when the outer-branch trace condition is satisfied, a low/high bistable subinterval. Second, the local dynamics around positive equilibria were examined through a delay-induced Hopf bifurcation analysis, which determined the onset of oscillatory behavior and the associated stability switching. Numerical simulations confirmed the predicted branch structure and the delay-dependent stability switching on the upper equilibrium branch. These results provided a compact dynamical description of how density and intracellular processing time jointly regulated state selection and rhythmic activity in contact-mediated synthetic signaling systems.
Citation: Huichao Xing, Jun Wu, Conghua Wang. Bistability and delay-induced oscillations in a density-gated synNotch model[J]. AIMS Mathematics, 2026, 11(5): 13216-13232. doi: 10.3934/math.2026545
Synthetic signaling circuits provide a versatile framework for programming contact-dependent cell behaviors, yet their collective dynamics are strongly shaped by cell density and processing delay. In this work, we studied a reduced delay differential model motivated by synNotch-type signaling with density-dependent attenuation and adaptive inhibition. The analysis was organized along two complementary routes. First, the equilibrium structure was characterized through a density-driven saddle-node bifurcation analysis, which identified the emergence of a three-equilibrium region and, when the outer-branch trace condition is satisfied, a low/high bistable subinterval. Second, the local dynamics around positive equilibria were examined through a delay-induced Hopf bifurcation analysis, which determined the onset of oscillatory behavior and the associated stability switching. Numerical simulations confirmed the predicted branch structure and the delay-dependent stability switching on the upper equilibrium branch. These results provided a compact dynamical description of how density and intracellular processing time jointly regulated state selection and rhythmic activity in contact-mediated synthetic signaling systems.
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