EGFL7 is required for junctional reorganization but not for the hierarchical assembly of tight junctions.

<p>(<b>A-H</b>). Representative confocal images of transverse sections of the dorsal aorta (DA) and posterior cardinal veins (PCV) stained with Claudin-5 (red), GFP to mark cell membranes (MEM-GFP; green), and DAPI to mark nuclei (blue). Phase contrast images for the PCVs represent the <i>Erg</i> in situ signal. All images taken at 63x magnification with scale bars indicating 20 μm. Dotted white and red lines in all panels delineate the endothelial cells comprising each vessel. As anatomical references, the hypochord in (A-D) and the kidney in (E-H) are indicated by solid white lines. (<b>A-B</b>). Claudin-5 expression is absent from endothelial cells of the DA in late tailbud stage (stage 33/34) control and EGFL7-depleted embryos. (<b>C</b>). Claudin-5 localizes to tight junctions between endothelial cells once the DA lumen has formed in early tadpole stage (stage 35/36) control embryos. (<b>D</b>). Claudin-5 expression is apparent in tight junctions between EGFL7-depleted endothelial cells of the DA despite failed lumen formation at early tadpole stage (stage 35/36). (<b>E-F</b>). Claudin-5 expression is absent from endothelial cells of the PCV in late tailbud stage (stage 33/34) control and EGFL7-depleted embryos. (<b>G</b>). Claudin-5 localizes to distinct tight junctions between endothelial cells around the periphery of the PCV lumen in early tadpole stage (stage 35/36) control embryos. (<b>H</b>). Claudin-5 localizes to tight junctions along endothelial cell contacts within the PCV of early tadpole stage (stage 35/36) EGFL7-depleted embryos. 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.