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Fig 2. Basement membrane proteins are deposited on both the basal and apical surfaces of early vessels in Xenopus.(A-G) Representative confocal images of transverse sections of the dorsal aorta (DA) and posterior cardinal veins (PCV) stained with laminin or fibronectin (red). In A,B,D,E,F staining with GFP to mark cell membranes (MEM-GFP) and DAPI to mark nuclei (blue) is also shown. In C and G, Flk-1:GFP transgenic animals were used to identify endothelial cells (green). All images taken at 63x magnification with scale bars indicating 20 μm. Dotted white lines in all panels delineate the endothelial cells comprising each vessel. As anatomical references, the hypochord in (A-B) and the kidney in (D-F) are indicated by solid white lines. Dotted lines in the magnified images represent vessels. Asterisks denote the vessel lumen. (A). The DA of early tadpole stage (stage 35/36) control embryos display deposition of fibronectin on both apical and basal surfaces (arrowheads point to apical staining). (B). DA of early tadpole stage (stage 35/36) control embryo exhibits the laminin staining on the basal and the apical surfaces of the vessel (arrowheads point to apical staining). (C). By late tadpole stage (stage 46), proper polarity is established in the dorsal aorta with laminin localizing to the basal surface of endothelial cells (arrowheads point to basal staining). (D) PCV of early tadpole stage (stage 35/36) control embryo exhibits apically and basally deposited fibronectin (arrowheads point to apical staining). (E-F). The kidney displays appropriate basal expression of laminin (arrow), however, the PCV of early tadpole stage (stage 35/36) control embryos display aggregates of laminin staining on the apical surface (arrowheads). (G) Laminin becomes distributed on the basal surface of the posterior cardinal vein in late tadpole stage (stage 46) embryos (arrowheads point to basal staining). 3–4 embryos from each condition/stage were assessed from at least three independent injection batches at the same position along the anterior-posterior axis of the embryo. |
