Figure 7. Altered cell homeostasis in Ngn3-deficient small intestine.

Sections of adult control (A, C, and E) and mutant (B, D, and F) intestine were examined for the status of the proliferative crypt compartment (A, B, E, and F), villus length (measurements in G), and cell turn over (C, D, and measurement in H). (A and B) Immunofluorescence staining for the proliferative cell marker Ki67 clearly demonstrates an up to 2-fold enlargement of the proliferative crypt compartment (dashed bars in A and B) in Ngn3-deficient intestine. Arrows point to chromogranin A⁺ cells. (G) Measurement of the villi length indicates an approximately 40% reduction in their length in mutant intestine. (C and D) Twenty-four hours before dissection, adult control and mutant mice were injected with BrdU, and BrdU-labeled cells were then visualized by immunofluorescence staining. Then the distance from the villus base to last labeled BrdU⁺ cell was measured (dashed bars in C and D), demonstrating a 1.6-fold accelerated cell turnover in Ngn3-deficient intestine. Arrows point to chromogranin A⁺ cells. (E and F) H&E staining showing the enlargement of the crypt compartment seen in Ngn3 mutant intestine. n = 3. The age of the animals analyzed is 10–12 weeks.