Branching parameters
�BMP4 may
prevent proximal type differentiation, allowing cells to accept
signals for distal development.
�TTF1 and
HNF3B may promote differentiation towards surfactant producing
cells.
�Shh may
induce proliferation and differentiation in mesenchyme and inhibit
epithelial proliferation signals (FGF10).
�TGF-B may
induce extracellular matrix production, which in turn may further
anchor and stabilize epithelial cells.