Fig. 3. Alveolar type I and type II cell maturation is disrupted in Cebpa^/ mice. Serial sections of lung from E18.5 control and Cebpa^/ mice were stained for FOXA1 (A,B), TTF1 (C,D) and Aqp5 (E,F). In Cebpa^/ mice, the cuboidal epithelium of the peripheral lung saccules homogeneously expressed FOXA1 and TTF1, indicative of structural immaturity. Consistent with pulmonary immaturity, Aqp5 staining, a marker of squamous type I cells, was absent in lungs of Cebpa^/ mice. Scale bar: 25 µm.