Figure 4.

Summary of the segment polarity network model. (A) 1 dimensional representation of embryonic epidermis, where each block of 4 cells corresponds to one parasegment in the embryo. The only constraint on the state of each node is that the pair rule protein SLP is only expressed in cells 3 and 4 of each parasegment, because of an earlier developmental stage [14]. (B) Diagram representing the main interactions involved in the Drosophila segment polarity network model from [10,11]. Lines with red arrows/blue dots correspond to activation/inhibition (respectively). PTC is found on the cell surface but can trigger intra-cellular interactions. Inter-cellular interactions occur across cell boundaries.