The Notch ligand Delta-like 4 negatively regulates endothelial tip cell formation and vessel branching.
Delta-like 4 (Dll4) is a transmembrane ligand for Notch receptors that is expressed in arterial blood vessels and sprouting endothelial cells. Here we show that Dll4 regulates vessel branching during development by inhibiting endothelial tip cell formation. Heterozygous deletion of dll4 or pharmacological inhibition of Notch signaling using gamma-secretase inhibitor revealed a striking vascular phenotype, with greatly increased numbers of filopodia-extending endothelial tip cells and increased expression of tip cell marker genes compared with controls. Filopodia extension in dll4(+/-) retinal vessels required the vascular growth factor VEGF and was inhibited when VEGF signaling was blocked. Although VEGF expression was not significantly altered in dll4(+/-) retinas, dll4(+/-) vessels showed increased expression of VEGF receptor 2 and decreased expression of VEGF receptor 1 compared with wild-type, suggesting they could be more responsive to VEGF stimulation. In addition, expression of dll4 in wild-type tip cells was itself decreased when VEGF signaling was blocked, indicating that dll4 may act downstream of VEGF as a "brake" on VEGF-mediated angiogenic sprouting. Taken together, these data reveal Dll4 as a negative regulator of vascular sprouting and vessel branching that is required for normal vascular network formation during development.
Suchting
Steven
S
Institut National de la Santé et de la Recherche Médicale, U833, 75005 Paris, France.
Freitas
Catarina
C
le Noble
Ferdinand
F
Benedito
Rui
R
Bréant
Christiane
C
Duarte
Antonio
A
Eichmann
Anne
A
D048868:Adaptor Proteins, Signal Transducing; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors; D000818:Animals; D002135:Calcium-Binding Proteins; D004730:Endothelium, Vascular / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D012171:Retinal Vessels / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014280:Triglycerides / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives / Q000494:pharmacology
D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D014280:Triglycerides; D042461:Vascular Endothelial Growth Factor A; D005680:gamma-Aminobutyric Acid; C057077:1,2-dilinolenoyl-3-(4-aminobutyryl)propane-1,2,3-triol; D040262:Receptors, Vascular Endothelial Growth Factor; D053829:Amyloid Precursor Protein Secretases