title: CCBE1 is essential for mammalian lymphatic vascular development and enhances the lymphangiogenic effect of vascular endothelial growth factor-C in vivo.
abstract: BACKGROUND
  Collagen- and calcium-binding EGF domains 1 (CCBE1) has been associated with Hennekam syndrome, in which patients have lymphedema, lymphangiectasias, and other cardiovascular anomalies. Insight into the molecular role of CCBE1 is completely lacking, and mouse models for the disease do not exist.
  
  
  OBJECTIVE
  CCBE1 deficient mice were generated to understand the function of CCBE1 in cardiovascular development, and CCBE1 recombinant protein was used in both in vivo and in vitro settings to gain insight into the molecular function of CCBE1.
  
  
  RESULTS
  Phenotypic analysis of murine Ccbe1 mutant embryos showed a complete lack of definitive lymphatic structures, even though Prox1(+) lymphatic endothelial cells get specified within the cardinal vein. Mutant mice die prenatally. Proximity ligation assays indicate that vascular endothelial growth factor receptor 3 activation appears unaltered in mutants. Human CCBE1 protein binds to components of the extracellular matrix in vitro, and CCBE1 protein strongly enhances vascular endothelial growth factor-C-mediated lymphangiogenesis in a corneal micropocket assay.
  
  
  CONCLUSIONS
  Our data identify CCBE1 as a factor critically required for budding and migration of Prox-1(+) lymphatic endothelial cells from the cardinal vein. CCBE1 probably exerts these effects through binding to components of the extracellular matrix. CCBE1 has little lymphangiogenic effect on its own but dramatically enhances the lymphangiogenic effect of vascular endothelial growth factor-C in vivo. Thus, our data suggest CCBE1 to be essential but not sufficient for lymphangiogenesis.
authors.affiliation: Hubrecht Institute-KNAW, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
authors.forename: Frank L
authors.initials: FL
authors.lastname: Bos
authors.forename: Maresa
authors.initials: M
authors.lastname: Caunt
authors.forename: Josi
authors.initials: J
authors.lastname: Peterson-Maduro
authors.forename: Lara
authors.initials: L
authors.lastname: Planas-Paz
authors.forename: Joe
authors.initials: J
authors.lastname: Kowalski
authors.forename: Terhi
authors.initials: T
authors.lastname: Karpanen
authors.forename: Andreas
authors.initials: A
authors.lastname: van Impel
authors.forename: Raymond
authors.initials: R
authors.lastname: Tong
authors.forename: James A
authors.initials: JA
authors.lastname: Ernst
authors.forename: Jeroen
authors.initials: J
authors.lastname: Korving
authors.forename: Johan H
authors.initials: JH
authors.lastname: van Es
authors.forename: Eckhard
authors.initials: E
authors.lastname: Lammert
authors.forename: Henricus J
authors.initials: HJ
authors.lastname: Duckers
authors.forename: Stefan
authors.initials: S
authors.lastname: Schulte-Merker
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D003315:Cornea / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D004729:Endothelium, Lymphatic / Q000098:blood supply* / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D042583:Lymphangiogenesis / Q000235:genetics / Q000502:physiology*; D042601:Lymphatic Vessels / Q000196:embryology* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D011485:Protein Binding / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D042582:Vascular Endothelial Growth Factor C / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: C546964:CCBE1 protein, human; D002135:Calcium-Binding Proteins; D025521:Tumor Suppressor Proteins; D042582:Vascular Endothelial Growth Factor C; C467483:vascular endothelial growth factor C, mouse