title: ROBO2 restricts the nephrogenic field and regulates Wolffian duct-nephrogenic cord separation.
abstract: ROBO2 plays a key role in regulating ureteric bud (UB) formation in the embryo, with mutations in humans and mice leading to supernumerary kidneys. Previous studies have established that the number and position of UB outgrowths is determined by the domain of metanephric mesenchymal Gdnf expression, which is expanded anteriorly in Robo2 mouse mutants. To clarify how this phenotype arises, we used high-resolution 3D imaging to reveal an increase in the number of nephrogenic cord cells, leading to extension of the metanephric mesenchyme field in Robo2-null mouse embryos. Ex vivo experiments suggested a dependence of this effect on proliferative signals from the Wolffian duct. Loss of Robo2 resulted in a failure of the normal separation of the mesenchyme from the Wolffian duct/ureteric epithelium, suggesting that aberrant juxtaposition of these two compartments in Robo2-null mice exposes the mesenchyme to abnormally high levels of proliferative stimuli. Our data suggest a new model in which SLIT-ROBO signalling acts not by attenuating Gdnf expression or activity, but instead by limiting epithelial/mesenchymal interactions in the nascent metanephros and restricting the extent of the nephrogenic field. These insights illuminate the aetiology of multiplex kidney formation in human individuals with ROBO2 mutations.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Elanor N
authors.initials: EN
authors.lastname: Wainwright
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Wilhelm
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Combes
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Melissa H
authors.initials: MH
authors.lastname: Little
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia. Electronic address: p.koopman@imb.uq.edu.au.
authors.forename: Peter
authors.initials: P
authors.lastname: Koopman
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000166:cytology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000096:biosynthesis / Q000235:genetics*; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics; D007668:Kidney / Q000196:embryology*; D008648:Mesoderm / Q000166:cytology / Q000196:embryology; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D014928:Wolffian Ducts / Q000196:embryology*; D000098552:Slit Homolog 2 Protein; D000097905:Roundabout Proteins
chemical_list: D051100:Glial Cell Line-Derived Neurotrophic Factor; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D014157:Transcription Factors; D000098552:Slit Homolog 2 Protein; C498888:Robo2 protein, mouse; D000097905:Roundabout Proteins; C497420:Six2 protein, mouse
keywords: Kidney; Mouse; Nephrogenic cord; Ureteric bud; Wolffian duct