Figure 2. Foxl1⁺ cells have long processes and express potential niche supporting factors.

(A) Schema of Foxl1-Cre; Rosa-mTmG mouse used to drive expression of a membrane-bound green fluorescence protein (GFP) in Foxl1-Cre positive cells. (B) Foxl1-Cre-driven expression of membrane-bound GFP is restricted to pericryptal mesenchymal cells, which elaborate long extensions into the villus tips and surrounding intestinal crypts. Immunofluorescence staining for GFP (green) and αSMA (red) shows very limited overlap between the two markers, indicating that Foxl1⁺ cells represent a unique cell population. αSMA expression is present in the core of the lamina propria, whereas GFP expression is located at the pericryptal sheath. (C) Immunofluorescence staining for Foxl1-Cre driven GFP (green) and Myh11 (red) indicates very limited overlap between the two markers. (D) A histogram of fluorescence-activated cell sorting of intestinal mesenchymal cells isolated from C57BLl6 control and Foxl1Cre; Rosa-YFP mice using YFP fluorescence. The x-axis shows YFP fluorescence intensity, and the gate indicated in the Foxl1Cre; Rosa-YFP plot shows the sorted cells from which RNA was isolated for RNA sequence analysis. Note the absence of high-intensity YFP⁺ cells in the control histogram. (E) Relative mRNA levels of various markers and key signaling molecules in sorted Lgr5⁺-epithelial stem cells, differentiated villus epithelial cells, and sorted Foxl1⁺ cells.