Fig. 2. PDX1+ progenitors give rise to three types of pancreatic tissues in adult mice. Reporter Z/AP mice were crossed with pGK-Cre (B), Pdx1-Cre (C,D) or Pdx1-Cre-ER^TM (E-H, tamoxifen was given at E9.5). The pancreata of double transgenic mice were stained for HPAP activity 4 or 8 weeks after birth. (A) HPAP staining is not observed in controls in the absence of recombination. (B) Positive control shows that all pancreatic cells stain for HPAP when a general deletor line, pGK-Cre was mated with the reporter line. (C,D) In pancreata of Pdx1-Cre;Z/AP mice (4 weeks old), all exocrine, endocrine, and duct cells express HPAP, whereas mesenchyme and blood vessels do not. (C) Blood vessels are stained light brown with an anti-mouse PECAM antibody. (D) A confocal image of a Pdx1-Cre;Z/AP pancreas section which is double labeled by ß-galactosidase antibodies (stained red with Cy3) and antibodies against PECAM + vimentin (antigens present in endothelial or mesenchymal cells only, stained green with FITC). Yellow and orange stain (resulting from the combination of red and green) are observed, but not green or red only, demonstrating that only the blood vessel or mesenchymal cells maintain lacZ expression. Note that this section was not stained for HPAP, i.e. the dark areas are acini, islets (i) and ducts. (E-H) The HPAP staining pattern (8 weeks old) when Pdx1-Cre-ER^TM animals are crossed with Z/AP and TM is administered at E9.5. Islet (E), acini (F) and ducts (G-H) are labeled in a mosaic fashion. In H, the small ducts are stained with Wisteria floribunda agglutinin as brown and HPAP as blue. Note the blue staining in the small duct but not the adjacent acinar cells. (a, acini, broken white lines; d, duct, broken green lines; i, islets, broken red lines; v, blood vessel). Scale bars: in D, 20 µm; in G, 20 µm; in H, 20 µm for A, B, C, E, F and H.