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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.04.017 Byline: Lwaki Ebarasi (a), Liqun He (b), Kjell Hultenby (c), Minoru Takemoto (d), Christer Betsholtz (b), Karl Tryggvason (a), Arindam Majumdar (a) Keywords: Podocyte; Pronephros; Glomerulus; Glomerular filtration barrier; Nephrin; Zebrafish; Crumbs; Slit diaphragm; Differentiation; Cell polarity Abbreviations: GBM, glomerular basement membrane; dpf, days post fertilization; crb, crumbs Abstract: The glomerular filtration barrier is necessary for the selective passage of low molecular weight waste products and the retention of blood plasma proteins. Damage to the filter results in proteinuria. The filtration barrier is the major pathogenic site in almost all glomerular diseases and its study is therefore of clinical significance. We have taken advantage of the zebrafish pronephros as a system for studying glomerular filtration. In order to identify new regulators of filtration barrier assembly, we have performed a reverse genetic screen in the zebrafish testing a group of genes which are enriched in their expression within the mammalian glomerulus. In this novel screen, we have coupled gene knockdown using morpholinos with a physiological glomerular dye filtration assay to test for selective glomerular permeability in living zebrafish larvae. Screening 20 genes resulted in the identification of ralgps1, rapgef2, rabgef1, and crb2b. The crumbs (crb) genes encode a family of evolutionarily conserved proteins important for apical-basal polarity within epithelia. The crb2b gene is expressed in zebrafish podocytes. Electron microscopic analysis of crb2b morphants reveals a gross disorganization of podocyte foot process architecture and loss of slit diaphragms while overall polarity is maintained. Nephrin, a major component of the slit diaphragm, is apically mis-localized in podocytes from crb2b morphants suggesting that crb2b is required for the proper protein trafficking of Nephrin. This report is the first to show a role for crb function in podocyte differentiation. Furthermore, these results suggest a novel link between epithelial polarization and the maintenance of a functional filtration barrier. Author Affiliation: (a) Division of Matrix Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Scheeles vag 2, Plan 4 B1, SE-171 77 Stockholm, Sweden (b) Laboratory of Vascular Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, 17177 Stockholm, Sweden (c) Department of Pathology, Karolinska University Hospital/Huddinge, Karolinska Institutet, Stockholm, Sweden (d) Department of Clinical Cell Biology and Medicine, Chiba University Graduate School of Medicine, Chiba, Japan Article History: Received 27 October 2008; Revised 26 March 2009; Accepted 16 April 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2007.10.049 Byline: Elisabeth Raschperger (a), Etienne P.A. Neve (b), Annika Wernerson (c), Kjell Hultenby (d), Ralf F. Pettersson (a), Arindam Majumdar (e) Keywords: CXADR; CAR; CTX; Zebrafish; Pronephros; Podocyte; Tubulogenesis; Microvillus; Tight junction Abstract: The coxsackie and adenovirus receptor (CAR) is a member of the immunoglobulin superfamily and a component of vertebrate tight junctions. CAR protein is widely expressed in fish and mammals in organs of epithelial origin suggesting possible functions in epithelial biology. In order to gain insight into its function, we knocked the CAR gene down in zebrafish using antisense morpholinos. We identified a requirement for CAR in the terminal differentiation of glomerular podocytes and pronephric tubular epithelia. Podocytes differentiate in CAR morphants but are not able to elaborate a regularly patterned architecture of foot processes. In the tubules, CAR was required for the apposition of plasma membranes from adjacent epithelial cells but did not appear to be necessary for the formation of tight junctions. Additionally, tubular epithelia lacking CAR were not able to elaborate apical brush border microvilli. These results establish a requirement for CAR in the terminal differentiation of renal glomerular and tubular cell types. Author Affiliation: (a) Ludwig Institute for Cancer Research, Karolinska Institutet, Stockholm, Sweden (b) Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden (c) Department of Laboratory Medicine, Division of Pathology, Karolinska Institute Karolinska University Hospital, Huddinge, Sweden (d) Department of Pathology, Karolinska University Hospital/Huddinge, Karolinska Institutet, Stockholm, Sweden (e) Division of Matrix Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden Article History: Received 24 May 2007; Revised 26 October 2007; Accepted 30 October 2007

Byline: Arindam Majumdar, Iain A. Drummond Keywords: zebrafish; floating head; pronephos; glomerulus; podocyte; sclerotome Abstract: In zebrafish, the pronepheric glumerulus occupies a middle position underneath the notochord and is vascularized through angiogenic capillary ingrowth from the dorsal aorta. The midline mutants floating head (flh), sonic you (syu), and you-too (yot) provide the opportunity to study glnzuerolur differentiation in the absence of the notochord and vascularization from the dorsal aorta. In flh, syn, and yot mutants, glomeruli differentiate at ectopic lateral positions within the embryo and contain morphologically identifiable podocyte and endothelial cell types. In the absence of the dorsal aorta, endothelia from an alternate source are recruited by podocytes during glomerular vascularization to make functional glomeruli. Our results suggest that middle signals are required for proper glomerular morphogenesis but not for the differentiation of podocytes. Podocytes apper to play an important role in directing celluar recruitment events leading to glomerular differentiation. Furthermore, we find defects in sclerotomal development that correlate with defects in glomerular morphogenesis suggesting a possible link between the formation of these embryonic stuctures. Author Affiliation: Renal Unit, Massachusetts General Hospital, 149 13th Street, Charlestown, Massachusetts 02129 Article History: Received 8 October 1999; Revised 24 January 2000; Accepted 24 January 2000

The importance of angiomotin (Amot) during embryonic angiogenesis is studied. Results demonstrate an important role for Amot during tube formation, with defects in endothelial cell (EC) polarization and growth factor-induced migration.

The article presents a study which identifies the function of angiomotin-like protein 1 (AmotL1) in comparison to angiomotin (Amot) in the polarization and migration of endothelial cell (EC). It states that (Amot) is a coiled-coil protein in ECs which controls migration, formation of tight junction (TJ) and cell polarity. Results of the small interfering ribonucleic acid-(RNA) mediated silencing in mouse cells show that AmotL1 has the same effects with Amot on EC migration and TJ formation.

Transcriptional readout downstream of canonical Wnt signaling is known to be mediated by β-catenin activation of well-described targets, but potential transcriptional readout in response to noncanonical Wnt signaling remains poorly understood. Here, we define a transcriptional pathway important in noncanonical Wnt signaling. We have found that Wnt11 is a direct target of a canonical β-catenin pathway in developing heart and that Wnt11 mutants show cardiac outflow tract defects. We provide genetic and biochemical evidence thatWnt11 signaling affects extracellular matrix composition, cytoskeletal rearrangements and polarized cell movement required for morphogenesis of the cardiac outflow tract. Notably, transforming growth factor β2 (TGFβ2), a key effector of organ morphogenesis, is regulated by Wnt11-mediated noncanonical signaling in developing heart and somites via one or more activating transcription factor (ATF)/cyclic AMP response element binding protein (CREB) family members. Thus, we propose that transcriptional readout mediated at least in part by a Wnt11 → ATF/CREB → TGFβ2 pathway is critical in regulating morphogenesis in response to noncanonical Wnt signaling. [ABSTRACT FROM AUTHOR]

Presents information on a study which explored the role of the Wnt11 glycoprotein in ureteric branching during metanephric kidney development. Embryonic tissue sources of the adult metanephric kidney of mammals; Analysis of the Wnt11 allele; Discussion on the genetic requirement for Wnt11 in kidney ureteric branching morphogenesis; Evaluation of Wnt genes proposed to play roles in branching morphogenesis.