Treatment with 500 ng/ml FGF10-STAB1 resulted in notable morphological changes in the developing lung, manifested by significant dilation of the distal epithelium, lack of branching of both proximal and distal epithelial buds, and swelling of the buds into cyst-like structures (Figs. 5A; S6). The gene discussed is FGF10; the disease is cyst.