Figure 7. Simple simulations of the effect on patterning by phase separation, of making a parameter responsive to a large-scale gradient.

In (a,b) the strength of homotypic adhesion is proportional to the concentration of a substance forming a linear gradient from (a) the left edges and (b) the centre of the culture. The scale is the same as in Figure 1a; the result is more efficient sorting to form larger patches, with ‘fingers’ emerging from it. In (c), homophilic adhesion is unaltered but heterophilic adhesion increases with distance from the left edge; the result is a change from patch production to very fine-scale mixing of different cell types; both parts are patterned, in the sense that they have a degree of order. To our knowledge, phase separation patterning systems with gradient-controlled parameters have not yet been built in real cells (simulation produced for this review).