Abstract
The developing kidney is a classic model system used to study mechanisms of organogenesis in mammals. Morphogenesis is regulated by epithelial-mesenchymal tissue interactions and involves inductive signaling across interactive tissue layers, ureter bud and metanephrogemc mesenchyme. As a response to induction a developmental program is activated in mesenchymal cells, and nephrons will develop as a result of mesenchymalepithelial transformation and subsequent simple morphogenesis which follows the process. Molecular genetic experimentation where gene function has been disrupted by gene targeting has proven to be fruitful in revealing the molecular mechanisms of kidney development and attracted attention again to this model system. These experiments indicated that sequentially activated genes regulate organogenesis and that cell signaling between epithelial ureter and kidney mesenchymal tissue is a key morphogenetic regulator. Molecular mediators from such gene families as transcription factors, cell adhesion molecules, kinases and secreted signaling molecules play an important role and are involved in the translation of cell behavior into morphogenesis. Recent data indicates that members of the Wnt gene family encoding secreted growth and differentiation factors act as classic tubule inducing signals. They are essential factors that control tubule induction and development in vitro and in vivo. A hypothetical model for some of the molecular mediators of tubule induction in vivo is presented.
