Figure 2: Models of directional sensing in migrating cells and back suppression in a gradient.
From: Evolutionarily conserved coupling of adaptive and excitable networks mediates eukaryotic chemotaxis
(a) Three classes of models of directional sensing in migrating cells involving a stochastic amplification module (see text). The representative schemes of the three classes of models are shown below. (b) Steady-state profile of the simulated activities of the three schemes under spatial gradients of varying steepness. (c) Left: representative images of migrating Dictyostelium cells expressing LimE-RFP in the absence (top) or presence (bottom) of cAMP gradient. Right: circular histogram showing frequency of LimE patches with or without a gradient. Scale bar, 10 μm. (d) Top: frames from a time-lapse video of a Dictyostelium cell expressing PH-GFP treated with 5 μM latrunculin. Dotted lines indicate the direction of the tip of a cAMP-filled micropipette. Scale bar, 10 μm. The cosine angle between the direction of the PH activity and that of the micropipette tip is plotted on the lower left graph (blue line), along with the cytosolic fluorescence intensity normalized to the pre-stimulus level (green line). Shaded grey regions indicate durations of cAMP gradient. Bottom right: circular histogram showing frequency of PH patches from 4 cells (derived from 300 frames for ‘no needle’ and 510 frames for ‘with needle’).
