The Notch target genes Hey1 and Hey2 are required for embryonic vascular development

Abstract

The Delta-Notch signaling pathway plays a central role in the development of most vertebrate organs. The Hey family of bHLH transcription factors are direct targets of Notch signaling. Loss of Hey2 in the mouse leads to cardiac defects with high postnatal lethality. We have now generated a mouse Hey1 knockout that has no apparent phenotypic defect. The combined loss of Hey1 and Hey2, however, results in embryonic death after embryonic day 9.5 (E9.5) with a global lack of vascular remodeling and massive hemorrhage. Initial vasculogenesis appears unaffected, but all subsequently developing major vessels in the embryo and yolk sac are either small or absent. Furthermore, the placental labyrinth completely lacks embryonic blood vessels. Similar vascular defects are observed in Jagged1 and Notch1 knockout mice. In the latter we found Hey1 and Hey2 expression in yolk sacs to be strongly reduced. Remaining large arteries in both Notch1 and Hey1/Hey2 knockout mice fail to express the arterial endothelial markers CD44, neuropilin1, and ephrin-B2. This indicates that Hey1/Hey2 are essential transducers of Notch signals in cardiovascular development that may mediate arterial cell fate decision.[Keywords: Notch pathway; angiogenesis; vasculogenesis; arteriogenesis; Hey1; Hey2] Supplemental material is available at http://www.genesdev.org.

In vitro and in vivo arterial differentiation of human multipotent adult progenitor cells

“…54 However, despite this inhibitory effect on EC proliferation, Notch activation was still compatible with up-regulation of arterial EC markers, such as Hey-2, similar to what we and others documented in in vitro studies. 55,56 Shh has also been shown to support neuronal differentiation, 57 yet we did not observe the formation of neurons in our system despite the intrinsic ability of hMAPCs for neuronal differentiation, the latter of which requires a different cytokine cocktail ( Figure S1; Document S1).…”

Adam10 is essential for early embryonic cardiovascular development

“…Our investigation of Adam10 endothelial knockout mouse model explicitly demonstrates that Adam10 is essential for endocardial cushion formation, ventricular trabeculation, and vasculogenesis. The AEKO mice not only phenocopied the Notch1 and Notch targets knockouts (Krebs et al, 2000;Fischer et al, 2004;Timmerman et al, 2004;Limbourg et al, 2005;Grego-Bessa et al, 2007), but also showed downregulated expression of Notch target gene Snail and Bmp2 in the cardiac tissues. Because we delete Adam10 primarily in the endothelial cells, which are only small fraction of the total cardiac, the expression changes of Snail and Bmp2 could be more severe in Adam10 deficient endocardium.…”

Functional Arterial and Venous Fate Is Determined by Graded VEGF Signaling and Notch Status During Embryonic Stem Cell Differentiation

“…[7][8][9][10][11] To evaluate this, FACS sorted Flk1 ϩ cells were differentiated with or without ␥-secretase inhibitor (GSI) to block Notch signaling. Compared with control cultures, GSI treatment did neither alter CD31 and ␣SMA expression levels ( Figure 4A) nor the numbers of CD31 ϩ cells analyzed by FACS.…”

“…[7][8][9] Hey1 and Hey2 are two direct downstream genes of Notch signaling and both have been reported to promote arterial fate, possibly by upregulating EphrinB2 and inhibiting EphB4 expression. 10,11 In addition, VEGF upregulates both Dll4 and Notch1 in vitro and promotes arterial specification in vivo. [12][13][14] Conversely, the orphan nuclear receptor COUP-TFII has been postulated to repress Notch signaling in veins, establishing the first genetic determinant of venous cell fate.…”