ABSTRACT
Growth of functional arteries is essential for the restoration of blood flow to ischemic organs. Notch signaling regulates arterial differentiation upstream of ephrin-B2 during embryonic development, but its role during postnatal arteriogenesis is unknown. Here, we identify the Notch ligand Delta-like 1 (Dll1) as an essential regulator of postnatal arteriogenesis. Dll1 expression was specifically detected in arterial endothelial cells, but not in venous endothelial cells or capillaries. During ischemia-induced arteriogenesis endothelial Dll1 expression was strongly induced, Notch signaling activated and ephrin-B2 upregulated, whereas perivascular cells expressed proangiogenic vascular endothelial growth factor, and the ephrin-B2 activator EphB4. In heterozygous Dll1 mutant mice endothelial Notch activation and ephrin-B2 induction after hindlimb ischemia were absent, arterial collateral growth was abrogated and recovery of blood flow was severely impaired, but perivascular vascular endothelial growth factor and EphB4 expression was unaltered. In vitro, angiogenic growth factors synergistically activated Notch signaling by induction of Dll1, which was necessary and sufficient to regulate ephrin-B2 expression and to induce ephrin-B2 and EphB4-dependent branching morphogenesis in human arterial EC. Thus, Dll1-mediated Notch activation regulates ephrin-B2 expression and postnatal arteriogenesis.
Subject(s)
Arteries/cytology , Endothelium, Vascular/cytology , Gene Expression Regulation/physiology , Intercellular Signaling Peptides and Proteins/physiology , Ischemia/physiopathology , Membrane Proteins/physiology , Neovascularization, Physiologic/physiology , Receptors, Notch/physiology , Animals , Aorta/cytology , Arteries/chemistry , Arteries/growth & development , Calcium-Binding Proteins , Capillaries/chemistry , Cells, Cultured/drug effects , Cells, Cultured/metabolism , Collateral Circulation/physiology , Constriction , Culture Media, Serum-Free , Endothelial Cells/metabolism , Gene Silencing , Hindlimb/blood supply , Humans , Intercellular Signaling Peptides and Proteins/deficiency , Intercellular Signaling Peptides and Proteins/genetics , Ischemia/etiology , Ischemia/genetics , Mice , Mice, Transgenic , Morphogenesis/genetics , Morphogenesis/physiology , Neovascularization, Physiologic/genetics , Organ Specificity , RNA, Small Interfering/pharmacology , Receptor, EphB2/biosynthesis , Receptor, EphB2/genetics , Receptor, EphB2/physiology , Receptor, EphB4/biosynthesis , Receptor, EphB4/genetics , Receptor, EphB4/physiology , Veins/chemistryABSTRACT
Marfan syndrome is caused by mutations in fibrillin-1, a large gene spanning approximately 200 kb of genomic DNA on chromosome 15q21. So far, more than 600 different mutations have been identified, accounting for 60-90% of all Marfan syndrome cases, the vast majority being single nucleotide exchanges as well as small deletions and insertions. Only four major rearrangements have been described in the literature so far. We have screened 11 individuals fulfilling the diagnostic criteria of Marfan syndrome but negative for point mutations in the fibrillin-1 gene by SSCP and/or direct sequencing, for large rearrangements. We report here the largest known de novo and out of frame deletion in the fibrillin-1 gene in a patient fulfilling the diagnostic criteria of Marfan syndrome. We identified the deletion breakpoints at the genomic and transcript levels and studied the expression of the mutated allele at the transcript and protein level. We conclude that large rearrangements may account for a non-negligible proportion of all Marfan cases.
