Fig. 4

Abnormal alveolar epithelium and decreased type I pneumocytes in Col4a1 ^+/Δex41. a–g co-staining of pSPC and podoplanin (PDPL). a, c, e PDPL normally lines the majority of the internal saccular surface and alveoli. b At E18.5, Col4a1 ^+/Δex41 PDPL lined the collapsed saccules, which are surrounded by clusters of pSPC cells. d, f At P6 and P30, the Col4a1 ^+/Δex41 alveolar epithelium is disorganized, as PDPL and pSPC staining shows. g Tie2-Cre; Col4a1 ^+/Flex41 mice pSPC cell clustering was absent. h–n HOPX staining in the nucleus and cytosol of type I pneumocytes. (i, k, m) Col4a1 ^+/Δex41 lungs display fewer nuclear HOPX⁺ cells (arrows), more prominently at P6 and P30. n Tie2-Cre; Col4a1 ^+/Flex41 lungs show similar staining to normal lungs. Scale bars = 50 μm in a–g and 200 μm in h–n