Foxc transcription factors directly regulate Dll4 and Hey2 expression by interacting with the VEGF-Notch signaling pathways in endothelial cells.
BACKGROUND
Recent studies have shown that in the developing embryo, arterial and venous identity is established by genetic mechanisms before circulation begins. Vascular endothelial growth factor (VEGF) signaling and its downstream Notch pathway play critical roles in arterial cell fate determination. We have recently shown that Foxc1 and Foxc2, two closely related Fox transcription factors, are essential for arterial cell specification during development by directly inducing the transcription of Delta-like 4 (Dll4), a ligand for Notch receptors. However, the basic mechanisms whereby the VEGF and Notch signaling pathways control transcriptional regulation of arterial-specific genes have yet to be elucidated.


RESULTS
In the current study, we examined whether and how Foxc transcription factors are involved in VEGF and Notch signaling in induction of Dll4 as well as the Notch target gene Hey2 in endothelial cells. We found that Foxc1 and Foxc2 directly activate the Hey2 promoter via Foxc binding elements. Significantly, Foxc2 physically and functionally interacts with a Notch transcriptional activation complex containing Su(H) and Notch intracellular domain to induce Hey2 promoter activity. Moreover, activation of the Dll4 and Hey2 promoters is induced by VEGF in conjunction with either Foxc1 or Foxc2 more than by either component alone. VEGF-activated PI3K and ERK intracellular pathways modulate the transcriptional activity of Foxc proteins in Dll4 and Hey2 induction.


CONCLUSIONS
Our new findings demonstrate that Foxc transcriptional factors interact with VEGF and Notch signaling to regulate arterial gene expression in multiple steps of the VEGF-Dll4-Notch-Hey2 signaling pathway.
Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
Hisaki
H
Hayashi
Tsutomu
T
Kume
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D002135:Calcium-Binding Proteins; D017931:DNA Primers; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008817:Mice, Mutant Strains; D051880:Receptors, Notch / Q000378:metabolism*; D012097:Repressor Proteins / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D051792:Basic Helix-Loop-Helix Proteins; D002135:Calcium-Binding Proteins; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; D012097:Repressor Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C519665:DLL4 protein, mouse; C485778:Hey2 protein, mouse