Vascular Robo4 restricts proangiogenic VEGF signaling in breast.
Formation of the vascular system within organs requires the balanced action of numerous positive and negative factors secreted by stromal and epithelial cells. Here, we used a genetic approach to determine the role of SLITs in regulating the growth and organization of blood vessels in the mammary gland. We demonstrate that vascularization of the gland is not affected by loss of Slit expression in the epithelial compartment. Instead, we identify a stromal source of SLIT, mural cells encircling blood vessels, and show that loss of Slit in the stroma leads to elevated blood vessel density and complexity. We examine candidate SLIT receptors, Robo1 and Robo4, and find that increased vessel angiogenesis is phenocopied by loss of endothelial-specific Robo4, as long as it is combined with the presence of an angiogenic stimulus such as preneoplasia or pregnancy. In contrast, loss of Robo1 does not affect blood vessel growth. The enhanced growth of blood vessels in Robo4(-/-) endothelium is due to activation of vascular endothelial growth factor (VEGF)-R2 signaling through the Src and FAK kinases. Thus, our studies present a genetic dissection of SLIT/ROBO signaling during organ development. We identify a stromal, rather than epithelial, source of SLITs that inhibits blood vessel growth by signaling through endothelial ROBO4 to down-regulate VEGF/VEGFR2 signaling.
Marlow
Rebecca
R
Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064, USA.
Binnewies
Mikhail
M
Sorensen
Lise K
LK
Monica
Stefanie D
SD
Strickland
Phyllis
P
Forsberg
E Camilla
EC
Li
Dean Y
DY
Hinck
Lindsay
L
D000818:Animals; D036341:Intercellular Signaling Peptides and Proteins / Q000172:deficiency / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000098:blood supply* / Q000378:metabolism*; D008565:Membrane Proteins / Q000172:deficiency / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000378:metabolism*; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000172:deficiency / Q000378:metabolism*; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein
D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein; C540792:Robo4 protein, mouse; C432251:Slit3 protein, mouse