Figure 4. DLL4 expression and Notch signaling are high in adult lacteals.

(A) DLL4 (white) displays perinuclear (arrows) and surface localization on villus arterioles. Endomucin (green) marks villus venules. Endothelial cells were identified by staining for zonula occludens 1 (ZO1, red). (B) DLL4 (white) is highly expressed on tip cells of villus blood capillaries (PECAM1, green). (C) DLL4 (white) is highly expressed on tip cells of villus lacteals (LYVE1, red); DAPI, blue. Dotted staining outside of lacteals is likely due to shedding from intestinal epithelial cells, where DLL4 was previously reported to be highly expressed (82). Relative DLL4 intensity (mean ± SD) in lacteal tip cells compared with neighboring stalk cells; n = 3. (D) Villus arterioles (VEGFR2, blue, arrowheads) have higher levels of Notch reporter (Venus, green) compared with venules (MAdCAM-1, red, arrows) in CBF1:H2B-Venus mice. Percentage (mean) Venus intensity of MAdCAM-1–negative arterioles versus MAdCAM-1–positive venules; n = 2. (E) Whole-mount immunostaining of lacteals (LYVE1, blue) and Venus (green) from adult CBF1:H2B-Venus mice. All LEC nuclei (PROX1, red) were also Venus⁺. Scale bars: 50 μm, A and D; 10 μm, B and C; 20 μm, E. **P < 0.01, 2-tailed unpaired Student’s t test.