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. ? ? ?
|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|
|Massimiani, M; Vecchione, L; Piccirilli, D et al. (2015) Epidermal growth factor-like domain 7 promotes migration and invasion of human trophoblast cells through activation of MAPK, PI3K and NOTCH signaling pathways. Mol Hum Reprod 21:435-51|
|Lacko, Lauretta A; Massimiani, Micol; Sones, Jenny L et al. (2014) Novel expression of EGFL7 in placental trophoblast and endothelial cells and its implication in preeclampsia. Mech Dev 133:163-76|
|Bambino, Kathryn; Lacko, Lauretta A; Hajjar, Katherine A et al. (2014) Epidermal growth factor-like domain 7 is a marker of the endothelial lineage and active angiogenesis. Genesis 52:657-70|
|Nichol, Donna; Stuhlmann, Heidi (2012) EGFL7: a unique angiogenic signaling factor in vascular development and disease. Blood 119:1345-52|
|Li, Jia; Stuhlmann, Heidi (2012) In vitro imaging of angiogenesis using embryonic stem cell-derived endothelial cells. Stem Cells Dev 21:331-42|
|Durrans, Anna; Stuhlmann, Heidi (2010) A role for Egfl7 during endothelial organization in the embryoid body model system. J Angiogenes Res 2:4|
|Nichol, Donna; Shawber, Carrie; Fitch, Michael J et al. (2010) Impaired angiogenesis and altered Notch signaling in mice overexpressing endothelial Egfl7. Blood 116:6133-43|
|Campagnolo, Luisa; Moscatelli, Ilana; Pellegrini, Manuela et al. (2008) Expression of EGFL7 in primordial germ cells and in adult ovaries and testes. Gene Expr Patterns 8:389-96|