Figure 2. Functional GUCY2C is expressed in Lgr5⁺ cells.

(A) Flow sorting of GFP⁺ and GFP^– cells from crypts of Lgr5-EGFP-Cre-Gucy2c^+/+ mice produced populations of active stem (Lgr5^High/SI^Low) and differentiated (Lgr5^Low/SI^High) cells (n = 3). (B) GUCY2C mRNA expression, quantified by RT-PCR, was compared in Lgr5^High/SI^Low and Lgr5^Low/SI^High cells. (C) GUCY2C (green), immunofluorescence in GFP⁺ (red) cells. β-catenin (cyan) highlights individual cells and DAPI (blue) highlights nuclei. (D) ST activates GUCY2C and downstream VASP serine 239 phosphorylation (P-VASP-239) (white) in GFP⁺ (green) cells in Gucy2c^+/+, but not Gucy2c^–/–, mice. β-catenin (red) highlights individual cells and DAPI (blue) highlights nuclei. (E–F) 8Br-cGMP reconstitutes levels of (E) Lgr5⁺GFP⁺ and (F) Bmi1⁺ cells in crypts of Gucy2c^–/– mice that are comparable to those in Gucy2c^+/+ mice. (G) Linaclotide enhances the enteroid-forming capacity of crypts in Gucy2c^–/– mice relative to Gucy2c^+/+ mice. *p < 0.05; ns, not significant. Bar in C represents 50 µm; bar in D represents 20 µm.