title: Alk1 and Alk5 inhibition by Nrp1 controls vascular sprouting downstream of Notch.
abstract: Sprouting angiogenesis drives blood vessel growth in healthy and diseased tissues. Vegf and Dll4/Notch signalling cooperate in a negative feedback loop that specifies endothelial tip and stalk cells to ensure adequate vessel branching and function. Current concepts posit that endothelial cells default to the tip-cell phenotype when Notch is inactive. Here we identify instead that the stalk-cell phenotype needs to be actively repressed to allow tip-cell formation. We show this is a key endothelial function of neuropilin-1 (Nrp1), which suppresses the stalk-cell phenotype by limiting Smad2/3 activation through Alk1 and Alk5. Notch downregulates Nrp1, thus relieving the inhibition of Alk1 and Alk5, thereby driving stalk-cell behaviour. Conceptually, our work shows that the heterogeneity between neighbouring endothelial cells established by the lateral feedback loop of Dll4/Notch utilizes Nrp1 levels as the pivot, which in turn establishes differential responsiveness to TGF-β/BMP signalling.
authors.affiliation: Vascular Biology Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.
authors.forename: Irene Maria
authors.initials: IM
authors.lastname: Aspalter
authors.affiliation: Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Gordon
authors.affiliation: Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: Alexandre
authors.identifier: http://orcid.org/0000-0002-3829-2577
authors.initials: A
authors.lastname: Dubrac
authors.affiliation: Vascular Biology Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.
authors.forename: Anan
authors.initials: A
authors.lastname: Ragab
authors.affiliation: Transgenic Services, London Research Institute-Clare Hall Laboratories, Cancer Research UK, Potters Bar EN6 3LD, UK.
authors.forename: Jarek
authors.initials: J
authors.lastname: Narloch
authors.affiliation: Developmental Signalling Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.|Epigenetic Events in Cancer, Centre for Genomic Regulation and Universitat Pompeu Fabra, Barcelona 080003, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Vizán
authors.affiliation: Vascular Patterning Laboratory, Vesalius Research Center, VIB, KU Leuven B-3000, Belgium.
authors.forename: Ilse
authors.initials: I
authors.lastname: Geudens
authors.affiliation: Vascular Biology Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.|Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Strasse 10, Berlin 13125, Germany.
authors.forename: Russell Thomas
authors.initials: RT
authors.lastname: Collins
authors.affiliation: Vascular Biology Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.
authors.forename: Claudio Areias
authors.initials: CA
authors.lastname: Franco
authors.affiliation: Regeneron Pharmaceuticals, Tarrytown, New York 10591, USA.
authors.forename: Cristina Luna
authors.initials: CL
authors.lastname: Abrahams
authors.affiliation: Regeneron Pharmaceuticals, Tarrytown, New York 10591, USA.
authors.forename: Gavin
authors.initials: G
authors.lastname: Thurston
authors.affiliation: UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK.
authors.forename: Marcus
authors.initials: M
authors.lastname: Fruttiger
authors.affiliation: Transgenic Services, London Research Institute-Clare Hall Laboratories, Cancer Research UK, Potters Bar EN6 3LD, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Rosewell
authors.affiliation: Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, Connecticut 06510, USA.|CIRB Collège de France, Inserm U1050, Paris 75231, France.|Department of Cellular and Molecular Physiology, Yale University Medical School, New Haven, Connecticut 06520, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Eichmann
authors.affiliation: Vascular Biology Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK.|Vascular Patterning Laboratory, Vesalius Research Center, VIB, KU Leuven B-3000, Belgium.|Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Strasse 10, Berlin 13125, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Gerhardt
mesh_terms: D030201:Activin Receptors, Type I / Q000378:metabolism*; D030301:Activin Receptors, Type II; D000818:Animals; D004730:Endothelium, Vascular / Q000254:growth & development*; D055427:Growth Differentiation Factor 2 / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D039942:Neuropilin-1 / Q000378:metabolism*; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D051880:Receptors, Notch / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism
chemical_list: C526108:Gdf2 protein, mouse; D055427:Growth Differentiation Factor 2; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; D051900:Smad3 Protein; C064045:delta protein; D039942:Neuropilin-1; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D030301:Activin Receptors, Type II; C498931:Acvrl1 protein, mouse; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse