Sequential Ligand-Dependent Notch Signaling Activation Regulates Valve Primordium Formation and Morphogenesis

Donal MacGrogan, Gaetano D'Amato, Stanislao Travisano, Beatriz Martinez-Poveda, Guillermo Luxán, Gonzalo Del Monte-Nieto, Tania Papoutsi, Mauro Sbroggio, Vanesa Bou, Pablo Gomez-Del Arco, Manuel Jose Gómez, Bin Zhou, Juan Miguel Redondo, Luis J. Jiménez-Borreguero, José Luis De La Pompa

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Rationale: The Notch signaling pathway is crucial for primitive cardiac valve formation by epithelial-mesenchymal transition, and NOTCH1 mutations cause bicuspid aortic valve; however, the temporal requirement for the various Notch ligands and receptors during valve ontogeny is poorly understood. Objective: The aim of this study is to determine the functional specificity of Notch in valve development. Methods and Results: Using cardiac-specific conditional targeted mutant mice, we find that endothelial/endocardial deletion of Mib1-Dll4-Notch1 signaling, possibly favored by Manic-Fringe, is specifically required for cardiac epithelial-mesenchymal transition. Mice lacking endocardial Jag1, Notch1, or RBPJ displayed enlarged valve cusps, bicuspid aortic valve, and septal defects, indicating that endocardial Jag1 to Notch1 signaling is required for post-epithelial-mesenchymal transition valvulogenesis. Valve dysmorphology was associated with increased mesenchyme proliferation, indicating that Jag1-Notch1 signaling restricts mesenchyme cell proliferation non-cell autonomously. Gene profiling revealed upregulated Bmp signaling in Jag1-mutant valves, providing a molecular basis for the hyperproliferative phenotype. Significantly, the negative regulator of mesenchyme proliferation, Hbegf, was markedly reduced in Jag1-mutant valves. Hbegf expression in embryonic endocardial cells could be readily activated through a RBPJ-binding site, identifying Hbegf as an endocardial Notch target. Accordingly, addition of soluble heparin-binding EGF-like growth factor to Jag1-mutant outflow tract explant cultures rescued the hyperproliferative phenotype. Conclusions: During cardiac valve formation, Dll4-Notch1 signaling leads to epithelial-mesenchymal transition and cushion formation. Jag1-Notch1 signaling subsequently restrains Bmp-mediated valve mesenchyme proliferation by sustaining Hbegf-EGF receptor signaling. Our studies identify a mechanism of signaling cross talk during valve morphogenesis involved in the origin of congenital heart defects associated with reduced NOTCH function.

Original languageEnglish (US)
Pages (from-to)1480-1497
Number of pages18
JournalCirculation research
Volume118
Issue number10
DOIs
StatePublished - May 13 2016

Keywords

  • endocardial cushions
  • endocardium
  • epithelial-mesenchymal transition
  • heparin-binding EGF-like growth factor
  • valve morphogenesis

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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