Fig. 1

IHC and IF analysis of cell lineage, SC markers, and proliferating cells in early developing mouse prostate. Sagittal sections of urogenital sinus day E18.5 embryo (a) and sagittal sections of postnatal day P0 (b–i) were subjected to antibodies against AR (a; red), p63 (b; DAB), Ki67 (c–i; red), KRT-8 (c; green), TROP-2 (d; green), Sca-1 (e; green), CD133 (f; green), CD44 (g; green), c-kit (h; green), and KRT-7 (i; green). Note mesenchymal AR expression (arrowheads) and absence of epithelial AR (arrows) during bud induction (a). Arrow in (b) shows p63 expression in ‘luminally’ located cells of distal epithelium in newborn prostates. Note weak luminally located KRT-8 expression of both proximal (arrowheads) and distal epithelium (arrow, c). Both TROP-2 and Sca-1 showed broader expression in the proximal AP (arrowhead, d, e) than in the distal AP (rightmost arrow, d, e) and distal DLP (leftmost arrow, d, e). Both markers, however, extended into the distal VP (lower arrow, d, e). CD133 expression was restricted to proximal periurethral mesenchyme (yellow arrowheads, f). CD44 was not, or only very rarely, detected in duct epithelium (arrowheads, g), but abundantly expressed in proliferative (c–i) distal tips (arrows, g). Note proximal periurethral expression of CD44 in mesenchyme (yellow arrowheads, g). C-kit was expressed in rare cells, preferentially located in proximal epithelium (arrowheads, h), the majority negative for Ki67 (arrows, h). Note a single proliferating KRT-7-positive cell (arrow, i) at the proximal/intermediate border of the AP (arrowhead; proximal epithelium). Counterstaining when used was either HTX (IHC) or DAPI (IF). Scale bars = 100 μm (a, f, h–i), 200 μm (c–e, g) and 500 μm (b); b is a composite image of several micrographs. In (b), the ventral lobe (VP), anterior prostate (AP), dorso-lateral prostate (DLP), ejaculatory sinus (ES), and urethra (Ur) are indicated