Fig. 4. High levels of Nmyc inhibit epithelial cell differentiation. (A,B) Sections of normal and severely affected E18.5 transgenic lungs hybridized with riboprobes for Scgb1a1 (a marker for differentiated Clara cells) and Sftpc (a marker, when expressed at high levels, for type II cells). (A,C) In wild type, a sharp boundary is present (arrowheads) at the BADJ between bronchioles lined with Clara cells (red) and the future alveoli, lined by type II cells (green). In the transgenic lung the boundary is not sharp (white bracket). (C,D) Sections of the same lungs after staining with antibody to Sox2. In normal lungs (C), Sox2 is restricted to nuclei of proximal epithelial cells, with a sharp boundary at the BADJ (arrowheads). In the transgenic lung (D), the boundary is not sharp (white bracket). Nuclei are stained with DAPI. (E) Gene expression assayed by RT-PCR of total RNA extracted from two normal and two transgenic lungs. Representative genes are lung differentiation markers (Aqp5, SftpA, SftpB, SftpC, and Scgb1a1), upregulated genes from microarray data (Ppan, Nol5a, Rog, cyclin D2 and claudin 6), and Sox9. Scale bars: 50 µm.