title: Erk MAP kinase regulates branching morphogenesis in the developing mouse kidney.
abstract: Branching morphogenesis of epithelium is a common and important feature of organogenesis; it is, for example, responsible for development of renal collecting ducts, lung airways, milk ducts of mammary glands and seminal ducts of the prostate. In each case, epithelial development is controlled by a variety of mesenchyme-derived molecules, both soluble (e.g. growth factors) and insoluble (e.g. extracellular matrix). Little is known about how these varied influences are integrated to produce a coherent morphogenetic response, but integration is likely to be achieved at least partly by cytoplasmic signal transduction networks. Work in other systems (Drosophila tracheae, MDCK models) suggests that the mitogen-activated protein (MAP) kinase pathway might be important to epithelial branching. We have investigated the role of the MAP kinase pathway in one of the best characterised mammalian examples of branching morphogenesis, the ureteric bud of the metanephric kidney. We find that Erk MAP kinase is normally active in ureteric bud, and that inhibiting Erk activation with the MAP kinase kinase inhibitor, PD98059, reversibly inhibits branching in a dose-dependent manner, while allowing tubule elongation to continue. When Erk activation is inhibited, ureteric bud tips show less cell proliferation than controls and they also produce fewer laminin-rich processes penetrating the mesenchyme and fail to show the strong concentration of apical actin filaments typical of controls; apoptosis and expression of Ret and Ros, are, however, normal. The activity of the Erk MAP kinase pathway is dependent on at least two known regulators of ureteric bud branching; the GDNF-Ret signalling system and sulphated glycosaminoglycans. MAP kinase is therefore essential for normal branching morphogenesis of the ureteric bud, and lies downstream of significant extracellular regulators of ureteric bud development.
authors.affiliation: Centre for Developmental Biology, Department of Biomedical Sciences, University of Edinburgh, George Square, Edinburgh, UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Fisher
authors.forename: L
authors.initials: L
authors.lastname: Michael
authors.forename: M W
authors.initials: MW
authors.lastname: Barnett
authors.forename: J A
authors.initials: JA
authors.lastname: Davies
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D006025:Glycosaminoglycans / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008648:Mesoderm; D051379:Mice; D008815:Mice, Inbred Strains; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009024:Morphogenesis; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; D012097:Repressor Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta; D014513:Ureter / Q000196:embryology / Q000378:metabolism
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; C495040:Gdnf protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D006025:Glycosaminoglycans; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D016212:Transforming Growth Factor beta; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; C494999:Ret protein, mouse; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one