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Fig. 4 crb2b morphants show defects in podocyte morphology. (A) Electron micrograph of a podocyte from control 4 dpf larvae shows the regular patterned array of foot processes along the GBM; GBM (black arrow) and slit diaphragms (black arrowheads). (B) In crb2b morphants, podocytes are attached to a GBM (black arrow), but the organization of regularly spaced foot processes is lost (white arrows show foot process fusion). Slit diaphragms are absent. Endothelial fenestrations are reduced in frequency. Nephrin protein is apically mis-localized in crb2b morphant podocytes. (C) Staining with α-Nephrin antibody shows that Nephrin protein is present (arrowheads) only along the surface of the GBM (visualized with WGA FITC). (D, E) In crb2b morphants, Nephrin protein is present throughout the podocytes with punctate staining (arrowheads) distal to the GBM. Nuclei visualized with DAPI; scale bar, 5 μm. (F) Immuno-electron microscopy with the α-Nephrin antibody in crb2b MO shows a podocyte with an apical membrane projection. White arrows indicate the GBM. (G) A magnification of the tip of the membrane projection indicated by the arrowhead in D. Nephrin protein is associated with the inner aspect of the plasma membrane (gold particles indicated by black arrowheads in E) within ectopic projections extending from podocyte apical membranes.
Reprinted from Developmental Biology, 334(1), Ebarasi, L., He, L., Hultenby, K., Takemoto, M., Betsholtz, C., Tryggvason, K., and Majumdar, A., A reverse genetic screen in the zebrafish identifies crb2b as a regulator of the glomerular filtration barrier, 1-9, Copyright (2009) with permission from Elsevier. Full text @ Dev. Biol.