Figure 3.

Bmi1⁺ lineage analysis in the small intestine. (a–e) After a single injection of tamoxifen, the Bmi1⁺ lineage is present from day 5 up to 9 months. The Bmi1⁺ lineage in the whole intestine is more abundant in the duodenum (top left corner) and in the first part of the jejunum, with almost no staining in the ileum (bottom right corner). After 1 month, there is an apparent modest progressive reduction in the number of labeled crypts. (f) The intestine of a 4-month-old Bmi1^CreER/+;Rosa26^LacZ/+ mouse does not show any LacZ staining without tamoxifen induction. (g,h) Two Bmi1^CreER/+; Rosa26^LacZ/+ mice received tamoxifen injection for 3 consecutive d (g), whereas two other mice with the same genotype were treated three times at 5-d intervals (h). Five days after the last injection, the intestines were harvested and stained for LacZ. (i) Intestinal mucosa of a Bmi1^CreER/+; Rosa26^LacZ/+ mouse 4 months after a single tamoxifen injection. The Bmi1⁺ lineage is visible on villi as a ‘line’ of cells coming from the crypt. White scale bar, 5 mm; black scale bar, 1 mm.