The coupled GRN. The four cell types considered in the coupled GRN are shown numbered in circles. They were represented by a GRN one for each attractor recovered in the single-cell models. Color filled nodes are the diffusible or mobile elements of the GRN. Note that these mobile elements can act non-cell autonomously or move among cells. For clarity we only show the main movement directions with arrows with the same color code as that used for the network nodes which movement is allowed. All the movements allowed in the model are listed in additional file 4. The figures show how, regardless of the initial configuration, the model always converges to the same attractor with the same spatial structure.