title: Slit-roundabout signaling regulates the development of the cardiac systemic venous return and pericardium.
abstract: BACKGROUND
  The Slit-Roundabout (Robo) signaling pathway has pleiotropic functions during Drosophila heart development. However, its role in mammalian heart development is largely unknown.
  
  
  OBJECTIVE
  To analyze the role of Slit-Robo signaling in the formation of the pericardium and the systemic venous return in the murine heart.
  
  
  RESULTS
  Expression of genes encoding Robo1 and Robo2 receptors and their ligands Slit2 and Slit3 was found in or around the systemic venous return and pericardium during development. Analysis of embryos lacking Robo1 revealed partial absence of the pericardium, whereas Robo1/2 double mutants additionally showed severely reduced sinus horn myocardium, hypoplastic caval veins, and a persistent left inferior caval vein. Mice lacking Slit3 recapitulated the defects in the myocardialization, alignment, and morphology of the caval veins. Ligand binding assays confirmed Slit3 as the preferred ligand for the Robo1 receptor, whereas Slit2 showed preference for Robo2. Sinus node development was mostly unaffected in all mutants. In addition, we show absence of cross-regulation with previously identified regulators Tbx18 and Wt1. We provide evidence that pericardial defects are created by abnormal localization of the caval veins combined with ectopic pericardial cavity formation. Local increase in neural crest cell death and impaired neural crest adhesive and migratory properties underlie the ectopic pericardium formation.
  
  
  CONCLUSIONS
  A novel Slit-Robo signaling pathway is involved in the development of the pericardium, the sinus horn myocardium, and the alignment of the caval veins. Reduced Slit3 binding in the absence of Robo1, causing impaired cardiac neural crest survival, adhesion, and migration, underlies the pericardial defects.
authors.affiliation: Department of Cell and Developmental Biology, University College London, London, UK.
authors.forename: Mathilda T M
authors.initials: MT
authors.lastname: Mommersteeg
authors.forename: William D
authors.initials: WD
authors.lastname: Andrews
authors.forename: Athena R
authors.initials: AR
authors.lastname: Ypsilanti
authors.forename: Pavol
authors.initials: P
authors.lastname: Zelina
authors.forename: Mason L
authors.initials: ML
authors.lastname: Yeh
authors.forename: Julia
authors.initials: J
authors.lastname: Norden
authors.forename: Andreas
authors.initials: A
authors.lastname: Kispert
authors.forename: Alain
authors.initials: A
authors.lastname: Chédotal
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Christoffels
authors.forename: John G
authors.initials: JG
authors.lastname: Parnavelas
mesh_terms: D000818:Animals; D017209:Apoptosis; D002448:Cell Adhesion; D002465:Cell Movement; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D006330:Heart Defects, Congenital / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009024:Morphogenesis; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009432:Neural Crest / Q000002:abnormalities / Q000378:metabolism; D010496:Pericardium / Q000002:abnormalities / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D012849:Sinoatrial Node / Q000002:abnormalities / Q000378:metabolism; D020825:T-Box Domain Proteins / Q000378:metabolism; D046509:Tissue Culture Techniques; D014684:Venae Cavae / Q000002:abnormalities / Q000378:metabolism*; D025721:WT1 Proteins / Q000378:metabolism; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D020825:T-Box Domain Proteins; D025721:WT1 Proteins; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein; C498888:Robo2 protein, mouse; C432251:Slit3 protein, mouse; C420983:Tbx18 protein, mouse