_Loss of epithelial FGF receptor leads to loss of branching
_FGF10 in mice from mesenchyme binds to FGFR2 on epithelial cells.
_Epithelial Shh (sonic hedgehog) shuts off FGF10 from mesenchyme, stopping
growth. New buds form in Shh negative areas
that have persistent FGF10 production
_Other FGF (e.g. FGF7) and other FGFR (e.g. FGFR3 and 4) may play a
similar role in later stages of distal/alveolar
lung development.