ALT Figure 2A-B: Lack of Osr1 in mesenchymal cells leads to lymphatic vasculature defects. (A) Maximal intensity projection images of Osr1+/+ and Osr1GCE/GCE E11.5 100 µm cross-sections after immunofluorescence. Immunolabeling for PROX1, VEGFR3 and PECAM1 shows normal commitment and delamination of LECs and normal blood endothelial structures in the dorsal part of the cardinal vein. Below, quantification of PROX1+ nuclei inside of the cardinal vein and dorsally migrating outside of the cardinal vein. n=3. (B) At E12.5, maximal intensity projection images of 100 µm cross-sections reveal first impairments in lymphatic structures labeled for PROX1 and VEGFR3. Below, quantification of VEGFR3+ lymphatic vasculature in the most dorsal region of the back. n=3. Dotted line represents the edge of the embryo