THE MOLECULAR-BASIS OF EMBRYONIC KIDNEY DEVELOPMENT

The development of the mature mammalian kidney begins with the invasio n of metanephric mesenchyme by ureteric bud. Mesenchymal cells near th e bud become induced and convert to an epithelium which goes on to gen erate the functional filtering unit of the kidney, the nephron. The co llecting duct system is elaborated by the branching ureter, the growth of which is dependent upon signals from the metanephric mesenchyme. T he process of reciprocal induction between ureter and mesenchyme is re peated many times over during development and is the key step in gener ating the overall architecture of the kidney. Genetic studies in mice have allowed researchers to begin to unravel the molecular signals tha t govern these early events. These experiments have revealed that a nu mber of essential gene products are required for distinct steps in kid ney organogenesis. Here we review and summarize the developmental role played by some of these molecules, especially certain transcription f actors and growth factors and their receptors. Although the factors in volved are far from completely known a rough framework of a molecular cascade which governs embryonic kidney development is beginning to eme rge. (C) 1997 Elsevier Science Ireland Ltd.