Hmga2−/−mice embryonic lung showed increased cell proliferation. (A) Lungs of Hmga2-KO (−/−) embryo were smaller (top) and showed a reduced lung-to-body-wet-weight ratio (bottom) when compared to WT (+/+) embryos at E18.5. Scale bars, 1 mm. Error bars show the SEM (n = 6). ***P <0.001; **P <0.01; *P <0.05 after one-way analysis of variance. (B) Representative of histological analysis using hematoxylin and eosin stain on sections of WT and Hmga2-KO embryonic lung at E18.5. Squares are shown at the bottom at higher magnification. Scale bars, 100 μm. (C) Sections of embryonic lung (E18.5) of WT and Hmga2-KO mice were analyzed by confocal microscopy after double immunostaining using KRT- and VIM-specific antibodies. Nuclear staining with DAPI (blue). Scale bars, 40 μm. (D) Quantification of proliferating (PCNA- or MKI67-positive) epithelial (KRT) and mesenchymal (VIM) cells showed increased proliferation in both tissues of Hmga2-KO embryonic lung. Sections of embryonic lung (E18.5) of WT and Hmga2-KO mice were treated as in E and used for quantification. Error bars show the SEM (n = 3). (E) Sections of embryonic lung (E18.5) of WT and Hmga2-KO mice were analyzed as in C using (left) KRT- and PCNA-specific antibodies or (right) VIM- and MKI67-specific antibodies. Nuclear staining with DAPI (blue). Scale bars, 40 μm. (F) Hmga2-KO enhanced expression of cell-cycle progression markers. Expression analysis of the indicated genes by quantitative RT-PCR in E18.5 lung of WT and Hmga2-KO mice. Rel nor exp, relative expression normalized to Tuba1a. Error bars show the SEM (n = 4). Asterisks as in A.