Fig. 10. Working model of how FGF7 and FGF10 signaling through FGFR2b regulates morphogenesis. The model summarizes our findings, and the dotted lines show other potential mechanisms: MMP2 may regulate FGFR1 cleavage; FGF1 expression may stimulate both FGFR1 and FGFR2; cofactors or co-receptors may specify the localization of FGF binding and, therefore, where proliferation occurs.