Rasip1 is expressed in LEC progenitors and lymphatic valve-forming cells. (A) Immunostaining of E11.5 transverse sections. Yellow arrows indicate Rasip1 expression in LEC progenitors in the CV; white arrows indicate Rasip1 expression in initial migrating LECs. n=3. DA, dorsal aorta; CV, cardinal vein. (B) Immunostaining of E14.5 sagittal sections. White arrows indicate Rasip1 expression in lymph sacs. n=3 embryos. LS, lymph sac. (C) Whole-mount immunostaining of E14.5 dermal lymphatic capillaries. White arrows indicate lymphatic capillaries. n=3. (D) Whole-mount immunostaining of E18.5 mesentery collecting lymphatic vessels. Note that Rasip1 expression shows a junctional localization in C and D. n=3 embryos. Arrow indicates developing lymphatic valves. Scale bars: 100 µm in A,B; 50 µm in C,D.