Simulation of differential expression. Timecourse simulation for Alx1 (left) and Otx (right) expression in different territories up to 70 hours post fertilization (hpf) in arbitrary units (au). Parameters of the ODE model are not fitted to reproduce experimental data. Spatial expression patterns are nevertheless generated in our model: Expression in the total embryo (blue) is the sum of expression in endoderm (purple), mesoderm (brown) and PMC (green) expression. The plotted values are the means of 800 simulations using randomly sampled parameter sets (error bars not shown). In the left part, total Alx1 mRNA abundance equals abundance in PMC; abundance in endoderm and mesoderm are 0. The simulation results show differential expression in the different territories.