Figure 2. Endothelial-Specific Deletion of Snail1 Derails Vascular Development.

(a-f) Whole-mount PECAM-1 immunofluorescent staining of E10.5 WT (a-c) and Snail1 LOF (d-f) embryos. Defective remodeling and branching are highlighted in the cephalic (rectangled area in a and d), tail (rectangled area in b and e) and intersomitic vessels (area demarcated by dotted lines in c and f with ISV width of field marked by the double-headed arrows). Scale bar: 100 μm.

(g-i) Quantification of relative vascular density in tail (PECAM-1 positive vessel area in rectangle box; g) vessels as well as vessel length (h) and branch points (defined as the junction point of 3 vessels; i) of ISV in WT and Snail1 LOF embryos (n=4 in each group). Data are presented as mean ± SEM. **p < 0.01, Student’s t test.

(j-q) Cross-sections (j,k,n,o) and sagittal sections (l,m,p,q) obtained from E10.5 WT (j-m) and Snail1 LOF (n-q) embryos were stained with anti-PECAM and anti-α-SMA antibodies to detect ECs and vascular smooth muscle cells, respectively. Boxed areas in l and p are shown at higher magnification in m and q, respectively. The arteries in WT embryos are surrounded by α-SMA positive cells, whereas arteries in LOF embryos recruited few α-SMA positive cells. Scale bar: 50 μm (j,k,n,o); 100 μm (l,p) 10 μm (m,q).

(r) Cross-sections from E10.5 Snail1^LacZ/wt embryos were stained with X-Gal/lacZ followed by PECAM-1 immunohistochemical staining. Green or red arrows denote the Snail1-positive ECs and perivascular cells, respectively. Scale bar: 50 μm.

(s) Cross-sections from E12.5 ROSA26;Dermo1-Cre⁺ embryos were stained with X-Gal/lacZ followed by α-SMA immunohistochemical staining. Red arrows mark dual-positive perivascular cells. Scale bar: 50 μm.

(t) Gross examination of whole embryos from Dermo1-Cre crosses at E14.5. No differences were observed between Snail1^fl/fl;Dermo1-Cre⁺ mutants and their control littermates in size, stage or overall appearance. Scale bar: 2 mm.