A switch between cis-activation and cis-inhibition.

<p>(A–C) Stationary Notch signal in a cell () <i>versus</i> the amount of ligand in that cell () and the amount of primary signaling source () for (A) , (B) and (C) . Red lines show the Notch signal dependence on in the absence of the primary signaling source () and for a primary signaling source with . Decreasing curves indicate cis-inhibition and increasing curves show cis-activation. In B, cis-interactions drive cis-activation at low values, whereas they drive cis-inhibition at higher . (D) Parameter space showing where cis-activation (gray region) and cis-inhibition (white region) occurs, according to inequality 5. (E–F) Effective circuit architectures of the model when cis-interactions drive cis-activation (top) and cis-inhibition (bottom) for (E) isolated cells with a primary signaling source (straight arrow) and for (F) two adjacent cells that interact through trans-binding. Black arrows stand for activation, while red blunt arrows for inhibition. Parameter values: in panels A–C, and in panel D.