The zebrafish pronephros: a genetic system for studies of kidney development.

The zebrafish, as a model system for vertebrate development, offers distinct experimental advantages for studies of organogenesis. The simplicity of the zebrafish pronephros, the feasibility of isolating large numbers of mutants, and the growth in infrastructure for genomics makes the zebrafish an attractive system for the analysis of kidney development. Mutants affecting several aspects of nephrogenesis, including differentiation of the intermediate mesoderm, nephron patterning, epithelial polarity, and angiogenesis, have been isolated. Analysis of mutant phenotypes and the cloning of mutant genes has revealed: (1) a role for bone morphogenetic proteins in patterning the ventral mesoderm, (2) an essential role for the pax2.1 gene in pronephric development, (3) multiple loci required for establishing epithelial polarity in the pronephric duct, (4) a central role for podocytes in directing glomerulogenesis, and (5) 15 loci associated with cystic maldevelopment in the pronephros. The striking similarities of pronephric cell types to those found in higher vertebrates, as well as the conservation of kidney-specific gene expression patterns, suggest that insights gained from studies in zebrafish will be broadly applicable to cell differentiation in the kidney.