During Branching Morphogenesis in Lung Development, …

Question

During branching morphogenesis in lung development, …
A) FGF10 is secreted by epithelial cells at the tip of the growing epithelial tubes.
B) FGF10 inhibits Shh production by the epithelial cells at the tip of the growing epithelial tubes.
C) Shh inhibits FGF10 production by the epithelial cells at the tip of the growing epithelial tubes.
D) Shh is produced by epithelial cells at the tip of the growing epithelial tubes.
E) None of the above.

Accepted Answer

Fibroblast growth factor FGF10 is secreted by the mesenchymal cells, inviting the nearby epithelial cells at the tip of the growing tube to invade the mesenchyme. The Sonic hedgehog (Shh) signal is sent in the opposite direction-from the epithelial cells back to the mesenchymal cells-where it likely inhibits FGF10 production, leading to branching of the growing bud.