... proteolytic activation of latent ligand, ligandbioavailability, ligand binding proteins and receptor affinity and presentation, receptor complexassembly and kinase activation, phosphorylation and ... hence stereotypy of the proximalairway branches. The model also predicts that the dynamically changingrelative activity of SHH, FGF10 and mSPRY2 may impartautomaticity to the branching process. ... pathway. In the upper panel, the FGF pathway is shown signaling the activation of MAP kinase/ERK2 via the FGFR, FRS2, Shp2, Grb2, Sos, Ras and Raf pathway. In the lower panel Sprouty2 (SPRY2)...