Fig. 4. Decreased expression of the E-cadherin reporter gene after deletion of intron 2 sequences at later embryonic stages. (A-C,F-H) Ecad-In2flox (A-C) and Ecad-In2floxdel embryos (F-H) were stained for ß-gal expression, at the indicated developmental stages, for 45 minutes (45', C,H) or overnight (ON, A,B,F,G). Increased expression in the skin is observed in Ecad-In2flox embryos during development. The E-cadherin locus without intron 2 is activated, but expression levels are significantly lower. (D,E,I,J) Isolated organs of E16.5 Ecad-In2flox (D,E) and Ecad-In2floxdel embryos (I,J) stained for ß-gal expression for 45 minutes (D,I) or overnight (E,J). High expression levels are found in the pancreas, stomach, gut and thymus of Ecad-In2flox embryos (D). After 45 minutes of staining, expression in organs of Ecad-In2floxdel embryos is only detected in pancreas and esophagus (I). After overnight incubation, lung epithelium is only weakly stained (J). (K-X) High magnification of sagittal sections of E11.5 embryos with the Ecad-In2flox (K-Q) and Ecad-In2floxdel allele (R-X). Organs or regions of the embryo are labeled in each figure. After sectioning, E-cadherin-specific expression can be observed in all tissues in Ecad-In2flox embryos, but no expression is found after deletion of intron 2, except for a faint expression detected in the pancreas primordium (V). Scale bars: 1 mm in A-J; 100 µm in K-X.