Figure 5. Constitutive β-Catenin activation did not induce Paneth cell to proliferate.

(A) Adult β-Catenin ex3^fl/fl; R26R-tdT; Lyz1^CreER mice were injected by tamoxifen and assessed for proliferation after 8 and 24 hours. Animals were labeled with EdU for 30 minutes before sacrifice.

(B) 8 and 24 hours after tamoxifen injection, tdT⁺ Paneth cells (purple) were readily detected with nuclear β-Catenin signals (green, pointed by arrowheads). β-Catenin remained largely at junctions in tdT⁻ cells.

(C) 8 and 24 hours after tamoxifen injection to induce β-Catenin activation, tdT⁺ Paneth cells (red) did not show EdU incorporation (green). E-Cad (in white) was used to outline cell boundaries.

(D) Genomic PCR using two sets of PCR primers (F+R1; F+R2) revealed robust recombination (excision of exon 3) in FACS-sorted tdT⁺ cells from tamoxifen-injected ex3^fl/fl; R26R-tdT; Lyz1^CreER and ex3^fl/+; R26R-tdT; Lyz1^CreER mice. Water and tail DNA served as controls.

(E) Adult β-Catenin ex3^fl/fl; R26R-tdT; Lyz1^CreER mice was subcutaneously embedded with 21-day slow-releasing tamoxifen pellets, and assessed after a prolonged tracing up to 1, 3, and 6 months.

(F) Tamoxifen-treated β-Catenin ex3^fl/fl; R26R-tdT; Lyz1^CreER mice, after a long-term tracing did not show epithelial hyperplasia or adenoma formation at 3 and 6 months (total of 8 mice).

(G) Tamoxifen-treated β-Catenin ex3^fl/fl; Villin-CreER mice exhibited formation of tubular adenoma within 1 week. (H-I), Lysozyme-expressing Paneth cells of above tamoxifen-treated animals did not express cell proliferation marker Ki67 (G, I) and PCNA (H, J).

Scale bars, 10 μm.