Figure 2.

CDX2 Is Required for Lgr5⁺ ISC Proliferation and Differentiation

(A) Serial tissue sections from control and Cdx2^ISC-Del intestines 4 days after TAM, showing CDX2 loss in patches of LGR5-GFP-Cre⁺ crypts (dashed areas magnified to right). CDX2 is retained in some Paneth cells in these crypts (arrows).

(B) Representative cell-cycle analysis of Lgr5⁺ ISCs from control and Cdx2^ISC-Del proximal small bowel. Flow cytometry of Cdx2^Del ISCs stained with Hoechst dye reveals accumulation in G1, with a reduced S-phase fraction.

(C) Cdx2^Fl/Fl;Lgr5^KI;R26R^YFP and control mice were injected with TAM for 5 days and examined at the indicated times. YFP fluorescence at 10 days indicates that traced Cdx2^Del crypts retain some ability to contribute to villi. At 90 days, tracing in Cdx2^ISC-Del intestines is confined to cysts (asterisk) and unproductive crypts.

(D) H&E staining of the cysts shows luminal debris. IHC confirms that traced cysts lack CDX2 and are surrounded by CDX2⁺ crypts that did not express the Lgr5^KI allele. Alkaline phosphatase (AP), periodic acid-Schiff (PAS), and Alcian blue (AB) staining show absence of mature enterocytes and goblet cells in the cystic structures.

Scale bars represent 30 μm (A and D) and 50 μm (C). See also Figure S1.