Fig. 1

BLECs in the meningeal layer and scavenger endothelial cells (SECs) in the cardinal vein show the same substrate specificity. (a) Cartoon depicting the zebrafish head region (dorsal view, anterior at the top) with the position of the two BLEC loop structures highlighted in red. The boxed area shows the position of the maximum projection of BLECs depicted in (b-j). Injection of the different fluorescently labeled substrates occurred either into the center of the optic tectum or into the ventricles of embryos at 5dpf. (b,c) Uptake of IgG-Alexa647 by BLECs. Dorsal confocal projections of a lyve1:DsRed positive BLEC (b), which has internalized fluorescent IgG-Alexa647 (c). (d-j) Confocal projections of BLECs that have internalized the indicated substrate combinations. (k) Overview about the uptake of the analyzed classes of substrate molecules by BLECs in either wild type, stab2 ^−/− mutant, mrc1a ^−/− mutant or stab2^−/−;mrc1a^−/− double mutant embryos. (l) Schematic overview of a zebrafish embryo, depicting injection of different fluorescent dyes into the bloodstream. Examples of substance uptake by SECs in the cardinal vein (boxed area) is shown in (m-v). (m-o) Maximum projection highlighting venous and lymphatic endothelial cells by flt4:mCitrine expression (n) and showing accumulation of the injected IgG-Alexa647 in the cardinal vein area (o). Uptake of different substrates by SECs in the cardinal vein (p-v). (w) Summary of the SEC uptake capacity for different classes of substrates which were tested in wild type, stab2 ^−/− mutant, mrc1a ^−/− mutant and stab2^−/−;mrc1a ^−/− double mutants. (m-o) mrc1a ^+/−, (p–t) wild type embryo; (u-v) mrc1a ^+/−. Scale bars in (b-j) represent 12.5 μm and in (m-v) 50 μm