Figure 2.
The superficial lymphatic vasculature arises by continuous sprouting, proliferation, and migration of LECs. Prox1-CreERT2;R26R pregnant dams were injected with 5 mg of TM at E10.5, and embryos were analyzed by X-gal staining at later time points. (A) At E11.5, most lacZ+ LECs are anterior to the forelimb (arrow); however, cells are also scattered along the anteroposterior axis (arrowhead). (B) At E12.5, the number of lacZ+ LECs has uniformly increased along the embryonic axis. (C) At E13.5, the largest accumulations of lacZ+ LECs are seen around the jugular (black arrow), perimesonephric (black arrowhead), and periorbital (red arrowhead) regions. (D) At E14.5, the initial lymphatic network appears to sprout, and more superficial lacZ+ LECs are present in the jugular and perimesonephric regions (arrows). (E) At E15.5, the pattern of superficial lymphatics appears identical to the one seen in similarly staged Prox1+/LacZ embryos (shown in F). Lymphatic vessel sprouting can be clearly seen (arrows).