Loss of Wnt5a-induced branching morphogenesis during Tmem67−/− embryonic lung ex vivo organogenesis. (A) Embryonic (E12.5) lungs were explanted and treated for 0, 6 and 24 h with either control-conditioned medium or medium containing Wnt5a. Magnified insets (black frames) under high power are shown for 24-h treatments. Epithelial branching is significantly induced by Wnt5a in Tmem67+/+ lungs, but this response is absent in Tmem67−/− lungs. The bar graph shows quantification of the total number of branches in one lung for each genotype. Values shown are means of three independent replicates and error bars indicate ±s.e.m. The statistical significance of the pair-wise comparisons are represented as *P<0.05 and n.s. for non-significant, Student's two-tailed t-test. (B) H&E staining of ex-vivo-cultured embryonic lung sections, showing normal acini (ac) and mesenchymal tissue (ms, in green) for wild-type Tmem67+/+ lung, and the stimulation of normal epithelial branching by Wnt5a (green asterisk and arrowheads). In contrast, Tmem67−/− lungs have abnormal mesenchymal cell condensates (red arrowheads), suggesting defective epithelial-mesenchymal induction. The red asterisks indicate abnormal bronchiolar formation; cl indicates the direction of the central lung. (C) Rho activation pull-down assays of whole-cell extracts from wild-type Tmem67+/+ and mutant Tmem67−/− embryonic (E15.5) lungs. Total RhoA in input material is shown as the loading control, with the ratio indicating active:total RhoA levels. A positive control for the assay (+GTPγS; loading with non-hydrolyzable GTPγS) and a negative control (+GDP; loading with GDP) are also shown. (D) Quantitative real-time PCR assays of transcript expression levels in wild-type Tmem67+/+ and mutant Tmem67−/− embryonic (E15.5) lungs for Shh, downstream effectors of the Shh signalling pathway (Gli1 and Ptch1) and a downstream effector of the canonical Wnt signalling pathway (Axin2). Levels of transcripts were all significantly increased in Tmem67−/− embryonic lungs, with the indicated pair-wise comparisons represented as **P<0.01, Student's two-tailed t-test for n=3 independent assays. Error bars indicate ±s.e.m.