title: BMP-SMAD signalling output is highly regionalized in cardiovascular and lymphatic endothelial networks.
abstract: Bone morphogenetic protein (BMP) signalling has emerged as a fundamental pathway in endothelial cell biology and deregulation of this pathway is implicated in several vascular disorders. BMP signalling output in endothelial cells is highly context- and dose-dependent. Phosphorylation of the BMP intracellular effectors, SMAD1/5/9, is routinely used to monitor BMP signalling activity. To better understand the in vivo context-dependency of BMP-SMAD signalling, we investigated differences in BMP-SMAD transcriptional activity in different vascular beds during mouse embryonic and postnatal stages. For this, we used the BRE::gfp BMP signalling reporter mouse in which the BMP response element (BRE) from the ID1-promotor, a SMAD1/5/9 target gene, drives the expression of GFP.
  
  
  
  A mosaic pattern of GFP was present in various angiogenic sprouting plexuses and in endocardium of cardiac cushions and trabeculae in the heart. High calibre veins seemed to be more BRE::gfp transcriptionally active than arteries, and ubiquitous activity was present in embryonic lymphatic vasculature. Postnatal lymphatic vessels showed however only discrete micro-domains of transcriptional activity. Dynamic shifts in transcriptional activity were also observed in the endocardium of the developing heart, with a general decrease in activity over time. Surprisingly, proliferative endothelial cells were almost never GFP-positive. Patches of transcriptional activity seemed to correlate with vasculature undergoing hemodynamic alterations.
  
  
  
  The BRE::gfp mouse allows to investigate selective context-dependent aspects of BMP-SMAD signalling. Our data reveals the highly dynamic nature of BMP-SMAD mediated transcriptional regulation in time and space throughout the vascular tree, supporting that BMP-SMAD signalling can be a source of phenotypic diversity in some, but not all, healthy endothelium. This knowledge can provide insight in vascular bed or organ-specific diseases and phenotypic heterogeneity within an endothelial cell population.
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Beets
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Staring
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.
authors.forename: Nathan
authors.initials: N
authors.lastname: Criem
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Maas
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.
authors.forename: Niels
authors.initials: N
authors.lastname: Schellinx
authors.affiliation: Department Anatomy and Embryology, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: Susana M Chuva
authors.initials: SM
authors.lastname: de Sousa Lopes
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium.|Department of Human Genetics, KU Leuven, Leuven, Belgium.|Department of Development and Regeneration, KU Leuven, Leuven, Belgium.
authors.forename: Lieve
authors.initials: L
authors.lastname: Umans
authors.affiliation: VIB Center for the Biology of Disease, VIB, Leuven, Belgium. an.zwijsen@cme.vib-kuleuven.be.|Department of Human Genetics, KU Leuven, Leuven, Belgium. an.zwijsen@cme.vib-kuleuven.be.
authors.forename: An
authors.identifier: 0000-0002-8583-1721
authors.initials: A
authors.lastname: Zwijsen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D002319:Cardiovascular System / Q000196:embryology / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism*; D004699:Endocardium / Q000254:growth & development / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D015398:Signal Transduction; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D019485:Bone Morphogenetic Proteins; D051785:Smad Proteins; D049452:Green Fluorescent Proteins
keywords: BMP-SMAD signalling; Endocardium; Heterogeneity; Lymphangiogenesis; Morphogen; Phenotype switching; Retina; Sprouting angiogenesis; Stochastic expression; Valve development