Suppression of Notch signalling by the COUP-TFII transcription factor regulates vein identity

Abstract

Arteries and veins are anatomically, functionally and molecularly distinct. The current model of arterial-venous identity proposes that binding of vascular endothelial growth factor to its heterodimeric receptor--Flk1 and neuropilin 1 (NP-1; also called Nrp1)--activates the Notch signalling pathway in the endothelium, causing induction of ephrin B2 expression and suppression of ephrin receptor B4 expression to establish arterial identity. Little is known about vein identity except that it involves ephrin receptor B4 expression, because Notch signalling is not activated in veins; an unresolved question is how vein identity is regulated. Here, we show that COUP-TFII (also known as Nr2f2), a member of the orphan nuclear receptor superfamily, is specifically expressed in venous but not arterial endothelium. Ablation of COUP-TFII in endothelial cells enables veins to acquire arterial characteristics, including the expression of arterial markers NP-1 and Notch signalling molecules, and the generation of haematopoietic cell clusters. Furthermore, ectopic expression of COUP-TFII in endothelial cells results in the fusion of veins and arteries in transgenic mouse embryos. Thus, COUP-TFII has a critical role in repressing Notch signalling to maintain vein identity, which suggests that vein identity is under genetic control and is not derived by a default pathway.

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

“…You et al have previously shown that overexpression of COUP-TFII gave defective vessels indicating an arterial to venous fate shift and their study placed COUP-TFII upstream of Notch. 15 Our data indicate a regulation of COUP-TFII by Notch signaling possibly through a feedback loop triggered by strong VEGF signaling.…”

“…[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. 15 These data places VEGF-Notch crosstalk in a central position for vascular morphogenesis.…”

The expression pattern of nuclear receptors during cerebellar development

“…In general, COUP-TFI is more highly expressed in the neuronal tissue of the central and peripheral nervous systems, whereas COUP-TFII is expressed in the mesenchyme of developing organs (Pereira et al, 1995). Loss of function assays indicate that COUP-TFI is important for neurogenesis and neural crest cell differentiation during embryonic development Zhou et al, 2001;Yamaguchi et al, 2004), while COUP-TFII acts as a major regulator of angiogenesis, vein identity, and organ development (Pereira et al, 1999;Takamoto et al, 2005;You et al, 2005). In the cerebellum, the expressions patterns of these two receptors are not co-localized.…”

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

“…9,10 Studies in Xenopus, zebrafish, and mice have revealed that, besides blood flow, 11 vessel-intrinsic cues and-later in development-signals from outside the vasculature 12,13 are implicated in defining arterial or venous fate such as members of the TGF-␤ pathway, 14,15 VEGF isoforms, 13,[16][17][18] neuropilins, 17 angiopoietins, 19 the Notch pathway, 7,9,[20][21][22] the patched pathway, 20 and COUP-TFII, a member of the orphan nuclear receptor superfamily. 6 Although it has been shown that some of these pathways are well conserved from zebrafish to mouse, less information is available on whether they have a similar role in humans. Because these molecular differences between arterial and venous ECs exist independently of blood flow and some of these factors work in an EC-intrinsic way, 2 it should be possible to manipulate some or all of these to endow ECs with an arterial or venous fate.…”

“…Arterial and venous endothelial cells (ECs) also have a distinct molecular signature, and such molecular specification occurs before the onset of blood flow. 3 Indeed, arteriovenous (AV) specification of ECs is accomplished early in development and is associated with the expression of a specific complement of factors: venous endothelium is characterized by the expression of EphB4, 4 Lefty-1, 5 Lefty-2, 5 COUP-TFII, 6 and MYO1-␤, 5 and arterial ECs express high levels of Notch 1 and 4, 7 Dll-4, 8 EphrinB1 and EphrinB2, 4 Jagged-1 and -2, 7 connexin-40, and Hey-2 (gridlock zebrafish ortholog). 9,10 Studies in Xenopus, zebrafish, and mice have revealed that, besides blood flow, 11 vessel-intrinsic cues and-later in development-signals from outside the vasculature 12,13 are implicated in defining arterial or venous fate such as members of the TGF-␤ pathway, 14,15 VEGF isoforms, 13,[16][17][18] neuropilins, 17 angiopoietins, 19 the Notch pathway, 7,9,[20][21][22] the patched pathway, 20 and COUP-TFII, a member of the orphan nuclear receptor superfamily.…”