Supporting Information S2 A model of Delta-Notch-mediated lateral inhibition in a sheet of intestinal epithelial cells: Effects of varying Delta gene dosage

ü Define the geometry of the system and assign an index number to each cell. Specify the topology by listing the neighbours of each cell. latticevector1 = N@8Sqrt@3D, 0<D;H* for hexagonal lattice *L latticevector2 = N@8Sqrt@3D ê 2, 3 ê 2<D; H* for hexagonal lattice *L addresses = Flatten@Table@8ja, jb<, 8ja, 0, n1 1<, 8jb, 0, n2 1<D, 1D; H* list of lattice addresses of the cells in the patch *L ncells = Length@addressesD; index@8ja_, jb_<D := jb + 1 + n2 * ja; H* serial number of cell at lattice address 8ja,jb< *L neighbouraddresses@jcell_D := H8j1, j2< = addresses@@jcellDD; 88Mod@j1 + 1, n1D, j2<, 8Mod@j1 1, n1D, j2<, 8j1, Mod@j2 + 1, n2D<, 8j1, Mod@j2 1, n2D<, 8Mod@j1 1, n1D, Mod@j2 + 1, n2D<, 8Mod@j1 + 1, n1D, Mod@j2 1, n2D<<L H* hexagonal lattice, with cyclic boundary conditions *L Table@neighbourindices@jcellD = Flatten@index êü neighbouraddresses@jcellDD, 8jcell, 1, ncells<D; xyposition@jcell_D := latticevector1 * addresses@@jcell, 1DD + latticevector2 * addresses@@jcell, 2DD ;