Liprin β1 is expressed in lymphatic endothelial cells and mediates lymphatic vessel integrity. (A-B) Immunofluorescent staining of iLECs (A) and HDMECs (B) for liprin β1 (red) and DAPI (blue). HDMECs are mixed dermal endothelial cell populations containing both LECs and BECs. Bars represent 50 μm. (C) Immunofluorescent staining of HDMECs for liprin β1 (green), PROX1 (red), and DAPI (blue). HDMECs are mixed dermal endothelial cell populations containing both LECs and BECs. Bar represents 50 μm. (D) Liprin β1 is expressed in human small intestinal lacteals. Liprin β1 (red), PROX1 (green), and DAPI (blue). Bar represents 20 μm. (E-F) Blood capillaries in small intestinal villi do not express liprin β1. Immunofluorescent staining of liprin β1 (red) and VE-cadherin (green). Arrow indicates lacteal. Bars represent 50 μm. (G-I) Whole-mount immunofluorescent staining of the mouse mesentery at P5 for liprin β1 (red) and VEGFR-3 (green). Note the high liprin β1 expression in lymphatic valves. Bars represent 100 μm. (J-K) Liprin β1 knockdown in Xenopus tadpoles results in edema formation. Tadpoles are from stage 45. Bar represents 1000 μm. (L-O′) Impaired assembly of DCLVs and ventral caudal lymph vessels (VCLVs) in stage 46 liprin β1-morphants of the Tg(Flk1:eGFP) transgenic line. Lymphatic endothelial cells are identified by the uptake of TRITC-dextran after intracardial injection and extravasation from blood vessels, whereas blood vessels express only GFP. Note grossly normal blood vascular assembly. (N′-O′) Close-up view of DCLVs from panels N-O. Bars represent the following: L-M, 1000 μm; N-O, 500 μm; N′-O′, 100 μm. (P-Q) Impaired drainage of locally injected fluorescent TRITC-dextran dye after liprin β1 knockdown. Arrows indicate normal dye drainage in control tadpoles. Tadpoles are at stage 46. Bar represents 500 μm.