Vasculogenesis and angiogenesis are controlled by a complex system of growth factors and their cognate receptors. These include VEGF/VEGFR and angiopoietin/Tie signaling pathways, as well as b-FGF, TGF-beta, ephrins, and their receptors. In addition, the importance of Notch signaling for vascular development and arterial-venous fate specification has been elucidated. While the importance of these pathways for vascular development has been documented, it is likely that other critical factors remain unidentified. Using a """"""""gene trap"""""""" approach, we recently identified Egfl7, a novel endothelial-restricted gene that encodes a secreted protein with an EMI domain, two EGF domains, and a putative DSL domain found in Notch ligands. Egfl7 is specifically expressed in the emerging vasculature and its progenitors in the yolk sac blood islands. In adults, Egfl7 is up-regulated during angiogenesis and arterial injury. Our preliminary studies indicate that EGFL7 binds to Notch 1 and 4 in vitro and mediates several of the known Notch effector functions. In the present proposal, we will test the hypothesis that EGFL7 is a novel ligand for Notch, that EGFL7 functions as a Notch agonist, and that EGFL7-induced Notch signaling mediates distinctive and non-redundant processes during vascular development and angiogenesis. We will test these hypotheses in primary human endothelial cells, and by using gain- and loss-of-function approaches in an ES cell in vitro differentiation system and in mice. We are proposing the following aims:
Aim 1 : Determine the role of EGFL7 in Notch signaling in HUVEC and in a chick chorioallantoic membrane model.
Aim 2 : Determine whether overexpression of Egfl7 in the endothelium leads to defects in vascular development. We will force expression of Egfl7 in endothelial cells by generating Tie2-Egfl7 transgenic mice, and induce Egfl7 expression in endothelial cells by generating VE-Cadherin:tTA;TRE-Egfl7 transgenic mice.
Aim 3 : Test whether Egfl7 function is crucial for early stages of vascular development. We will generate mice with a conditional knock-out allele and lentivirus-based siRNA knock-down in ES cells and mouse embryos.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Vascular Cell and Molecular Biology Study Section (VCMB)
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Schramm, Charlene A
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Weill Medical College of Cornell University
Anatomy/Cell Biology
Schools of Medicine
New York
United States
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Lacko, Lauretta A; Hurtado, Romulo; Hinds, Samantha et al. (2017) Altered feto-placental vascularization, feto-placental malperfusion and fetal growth restriction in mice with Egfl7 loss of function. Development 144:2469-2479
Kao, Der-I; Lacko, Lauretta A; Ding, Bi-Sen et al. (2015) Endothelial cells control pancreatic cell fate at defined stages through EGFL7 signaling. Stem Cell Reports 4:181-9
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