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Figure 2
Intestinal activity of the ngn3 promoter. The  -galactosidase protein marks ngn3 progenitor cells and their deriving enteroendocrine cells. A transgenic mouse model where a nuclear LacZ is driven by ngn3 regulatory sequences was generated and the stability of the -galactosidase protein was used to trace the progeny of ngn3-expressing cells. (A−D) Whole-mount X-Gal-stained E15.5 digestive tract (A) and adult duodenum (B) were sectioned (C and D, respectively); the blue nuclear staining indicates -galactosidase catalysis of the X-Gal substrate. At E15.5, X-Gal-stained cells are found all along the proximo-distal axis of the gut (A) in the intestinal epithelium (C). (E) Immunofluorescent co-staining for -galactosidase (red) and ngn3 (green) shows partial overlapping expression (yellow and orange cells, arrows in E). In the adult intestine, -Gal-labeled cells are found in the crypts (D, red immunofluoresence in F), in dividing PCNA+ cells (arrow in F) and also in the villi (D) where they co-stain with the pan-endocrine marker chromogranin A (dark brown cytoplasmic peroxidase staining, arrows in G) in differentiated enteroendocrine cells. The black line in (D) divides the crypt from the villus region. vi, villus; cr, crypt; d, duodenum.
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