Expression of TCF/LEF-family genes in E11.5 lung endoderm. (a) RT-PCR analysis of TCF/LEF family genes in distal and proximal endoderm. E11.5 lungs were collected, dissected into trachea and primary bronchi (proximal region), and the remainder (distal region) and endoderm was separated from mesoderm using enzymatic treatment. Total RNA isolated from whole lungs (W) and proximal (P) and distal (D) endoderm was used for RT-PCR. The absence of Wnt2 RNA from the endoderm fractions confirms the removal of the mesoderm. (b-d) Lef1 protein is localized in the nuclei of lung epithelial cells at E14.5 (b), and nuclei are also stained with DAPI (c). The images are merged in (d); the bar is 50 μm.