Inhibition of Lkb1 in the lung results in abnormal branching but not polarity defects. (A) E12.5 lung explants were cultured on transwell filters for 2 DIV with 1 µM 1NMPP1. Branches derived from a single bud are pseudocolored. (B) 1NMPP1-treated Lkb1^WT/WT (top) and Lkb1^MG/MG (bottom) epithelial buds show similar patterns of E-cadherin and Muc-1 staining. (C) Mesenchyme-free epithelial explants grown in matrigel show branching defects when Lkb1 activity is inhibited. (D) E-cadherin and ZO-1 staining patterns are similar between Lkb1^WT/WT (top) and Lkb1^MG/MG (bottom) mesenchyme-free epithelial explants, both grown in the presence of 1NMPP1. (E) Branching phenotype of epithelial tissue co-cultured with mesenchyme in transplant experiments depends on the genotype of the epithelium but not the mesenchyme. The four combinations of epithelial-mesenchymal co-cultures grown in the presence of 1NMPP1 are shown at setup (with mesenchyme pseudocolored) and at 48 h. Bars: (A and E) 500 µm; (B and C) 100 µm; (D) 10 µm.