Fig. 2: Distinct signaling activity in different segments of the small intestine.
From: Positional BMP signaling orchestrates villus length in the small intestine
a Ki67 immunofluorescence staining in Axin2-mGFP knock-in mice across small intestine segments, showing grayscale and fluorescence intensity. Axin2 intensity was quantified from stem to TA cells within crypts, with error bars representing the standard deviation (SD), visualized as shaded regions in the plots. N = 3 mice/group. Scale bars, 50 μm. b p-Smad1/5 immunofluorescence staining showing BMP signaling intensity along the villus axis. Data is presented by absolute position (left) and relative position (right) for comparison with error bars representing the standard deviation (SD), visualized as shaded regions in the plots. N = 5 mice. Scale bars, 500 μm (left); 100 μm (zoomed-in images on the right). c Immunoblotting of p-Smad1/5, total Smad1, and β-actin from the villus region of the proximal and distal small intestine. N = 3 mice/group. d tdTomato signals in 4xBRE-tdTomato knock-in mice, with magnified views in insets. N = 3 mice/group. Scale bars, 100 μm. e Id1 expression detected by RNAscope, showing punctate signals of Id1 mRNA. Quantification is shown with mean values and standard error of the mean (SEM). N = 3 mice. Scale bar, 100 μm. f Expression of BMP-suppressed enterocyte genes in the proximal and distal small intestine. N = 3 mice/group. g Both BMP ligand and inhibitor undergo generation (\(\varnothing\)B, \(\varnothing\)I), diffusion (DB, DI), and degradation (decB, decI). The competitive binding of the inhibitor to the ligand impedes the interaction between the BMP ligand and receptor (R and decBR) (Created in BioRender. Liu (2025) https://BioRender.com/7ob2gem). h Spatial distribution of BMP ligand, receptor, and inhibitor from villus apex to stroma, with BMP distribution in the proximal and distal small intestine with the model solutions (smooth lines). i Scatter plots comparing BMP and inhibitor diffusion rates, with model solutions fitting p-Smad1/5 distribution. j Grem1 protein distribution in the stromal cells and crypt region of the proximal small intestine, quantified in both regions. N = 3 mice/group. Scale bar: 50 µm. k BMP signaling intensity variation from proximal to distal regions (Created in BioRender. Liu (2025) https://BioRender.com/x1duy74). The data were analyzed by an unpaired t-test with Welch-correction (two-sided) (j). Data represent mean ± SD.
