Figure 2: Cell polarity, perpendicular as well as asymmetric cell division in embryonic lung distal epithelial stem/progenitor cells. Panels (A-M), which are adapted from El-Hashash and Warburton (2011) show evidences of cell polarity and both perpendicular and asymmetric cell division in distal epithelial stem/progenitor cells of embryonic lungs (E14). (A-D) Immunofluorescence at E14 shows strong signals for actin (A), myosin II-b (B) as well as the polarity proteins: Par-3 (C) and Par-6 (D) proteins at the apical side of distal epithelial cells (arrowheads). Dashed line represents the collagen IV–stained basement membrane. (E,F) Most mitotic cells in the distal epithelium divide perpendicularly, as represented by the perpendicular orientation of pericentrin-stained centrosomes (E; arrowheads, arrows) relative to the basement membrane (dashed line; E,F), while only a few mitotic cells have their centrosomes aligned parallel to the basement membrane (F; arrowheads). (G) Quantitation of spindle orientations, expressed as a percentage of all divisions in the distal epithelium from the experiments shown in E,F (n=48). (H-M) Expression of the polarity proteins LGN, mInsc, NuMA, and Numb in lung distal epithelium, as shown by immunofluorescence (H-K). Note polarized apical localization of these proteins (H-K; arrowheads) relative to collagen IV–stained basement membrane (dashed line). (L) Quantitation of the apical localization of proteins shown in H-J, which is expressed as a percentage of all cells in the distal epithelium (n= 87). (M) Quantification of late mitotic distal epithelial cells, with Numb inherited by one(inset in M) or both daughter cells at E14. This is expressed as a percentage of all divisions in the distal epithelium (n=42). Scale bars . 50 mm.