Figure 1.
Changes in intestinal crypt pathology 5 d after the first injection of the cre-inducing agent β-napthoflavone. (a,b). Hematoxylin-and-eosin-stained sections for control, induced Cre+Apc+/+ (a), and induced Cre+Apcfl/fl (b) mice, showing an enlarged crypt-like region in the induced Cre+Apcfl/fl mice. (c,d) Apc immunofluorescence in induced Cre+Apc+/+ (c) and in induced Cre+Apcfl/fl (d) mice. Loss of Apc protein was observed in all morphologically atypical cells (below the arrow) in Cre+Apcfl/fl mice. Apc staining was observed in unrecombined morphologically normal cells in the villus (above the arrow). (e,f) Wholemount preparations of intestines stained for lacZ activity to report cre-mediated recombination at the Rosa26R locus. Recombined control cells completely repopulate the crypt–villus axis (e) but fail to do so in the absence of Apc (f). (g) Sectioned material from f confirming that the pattern of recombination scored by LacZ activity directly overlays the pattern of histological change. Note that the staining for β-galactosidase exactly complements the Apc staining, with only the morphologically atypical cells (below the arrows) staining for β-galactosidase. For all panels, arrows indicate the point of demarcation between normal and atypical histology.