FGF10 diffusion accounts for branching morphogenesis.

<p>(<b>A</b>) Time lapse sequence of a growth simulation. The simulation relies on the laplacian model and couples the motion of the epithelial and mesothelial surfaces. Left image is a plot of the sigmoid growth response to FGF10 corresponding to the simulation. Colors in the mesenchyme stand for FGF10 flux, which focuses on distal tips. Branching occurs spontaneously and branches never meet each other, as observed in vivo. The epithelium to mesothelium distance is conserved, as branches never reach the mesothelium. (<b>B</b>) Results of three simulations with their respective growth responses. B1 features an other sigmoid growth response with a different spread. B2 and B3 feature linear growth responses with different values of <i>g</i>. The initial condition is always the initial tube displayed in A. The arbitrary scale is chosen the same for all (A) and (B) simulation results. While the morphologies obtained vary with the growth response, the initial non-branched tube always develops into a self-avoiding tree. (<b>C</b>) Time lapse sequence of a bud-scale 3D simulation based on the same model. The initial tube branches, while FGF10 flux focuses at bud tips, showing that the model and mechanisms are relevant to 3D geometry.