A reverse genetic screen in the zebrafish identifies crb2b

详细信息    查看全文

• 作者：Lwaki Ebarasi ; Liqun He ; Kjell Hultenby ; Minoru Takemoto ; Christer Betsholtz ; Karl Tryggvason ; Arindam Majumdar
• 关键词：Podocyte ; Pronephros ; Glomerulus ; Glomerular filtration barrier ; Nephrin ; Zebrafish ; Crumbs ; Slit diaphragm ; Differentiation ; Cell polarity
• 刊名：Developmental Biology
• 出版年：2009
• 出版时间：1 October 2009
• 年：2009
• 卷：334
• 期：1
• 页码：1-9
• 全文大小：535 K

文摘

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.