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.