SoxF factors and Notch regulate nr2f2 gene expression during venous differentiation in zebrafish.

Initial embryonic determination of artery or vein identity is regulated by genetic factors that work in concert to specify the endothelial cell׳s (EC) fate, giving rise to two structurally unique components of the circulatory loop. The Shh/VEGF/Notch pathway is critical for arterial specification, while the orphan receptor nr2f2 (COUP-TFII) has been implicated in venous specification. Studies in mice have shown that nr2f2 is expressed in venous but not arterial ECs, and that it preferentially induces markers of venous cell fate. We have examined the role of nr2f2 during early arterial-venous development in the zebrafish trunk. We show that expression of a subset of markers of venous endothelial identity requires nr2f2, while the expression of nr2f2 itself requires sox7 and sox18 gene function. However, while sox7 and sox18 are expressed in both the cardinal vein and the dorsal aorta during early trunk development, nr2f2 is expressed only in the cardinal vein. We show that Notch signaling activity present in the dorsal aorta suppresses expression of nr2f2, restricting nr2f2-dependent promotion of venous differentiation to the cardinal vein.

Swift MR ，Pham VN ，Castranova D ，Bell K ，Poole RJ ，Weinstein BM ... -  《-》

Zebrafish Sox7 and Sox18 function together to control arterial-venous identity.

Pendeville H ，Winandy M ，Manfroid I ，Nivelles O ，Motte P ，Pasque V ，Peers B ，Struman I ，Martial JA ，Voz ML ... -  《-》

Sox7 controls arterial specification in conjunction with hey2 and efnb2 function.

SoxF family members have been linked to arterio-venous specification events and human pathological conditions, but in contrast to Sox17 and Sox18, a detailed in vivo analysis of a Sox7 mutant model is still lacking. In this study we generated zebrafish sox7 mutants to understand the role of Sox7 during vascular development. By in vivo imaging of transgenic zebrafish lines we show that sox7 mutants display a short circulatory loop around the heart as a result of aberrant connections between the lateral dorsal aorta (LDA) and either the venous primary head sinus (PHS) or the common cardinal vein (CCV). In situ hybridization and live observations in flt4:mCitrine transgenic embryos revealed increased expression levels of flt4 in arterial endothelial cells at the exact location of the aberrant vascular connections in sox7 mutants. An identical circulatory short loop could also be observed in newly generated mutants for hey2 and efnb2. By genetically modulating levels of sox7, hey2 and efnb2 we demonstrate a genetic interaction of sox7 with hey2 and efnb2. The specific spatially confined effect of loss of Sox7 function can be rescued by overexpressing the Notch intracellular domain (NICD) in arterial cells of sox7 mutants, placing Sox7 upstream of Notch in this aspect of arterial development. Hence, sox7 levels are crucial in arterial specification in conjunction with hey2 and efnb2 function, with mutants in all three genes displaying shunt formation and an arterial block.

Hermkens DM ，van Impel A ，Urasaki A ，Bussmann J ，Duckers HJ ，Schulte-Merker S ... -  《-》

β-Catenin-dependent transcription is central to Bmp-mediated formation of venous vessels.

β-catenin regulates the transcription of genes involved in diverse biological processes, including embryogenesis, tissue homeostasis and regeneration. Endothelial cell (EC)-specific gene-targeting analyses in mice have revealed that β-catenin is required for vascular development. However, the precise function of β-catenin-mediated gene regulation in vascular development is not well understood, since β-catenin regulates not only gene expression but also the formation of cell-cell junctions. To address this question, we have developed a novel transgenic zebrafish line that allows the visualization of β-catenin transcriptional activity specifically in ECs and discovered that β-catenin-dependent transcription is central to the bone morphogenetic protein (Bmp)-mediated formation of venous vessels. During caudal vein (CV) formation, Bmp induces the expression of aggf1, a putative causative gene for Klippel-Trenaunay syndrome, which is characterized by venous malformation and hypertrophy of bones and soft tissues. Subsequently, Aggf1 potentiates β-catenin transcriptional activity by acting as a transcriptional co-factor, suggesting that Bmp evokes β-catenin-mediated gene expression through Aggf1 expression. Bmp-mediated activation of β-catenin induces the expression of Nr2f2 (also known as Coup-TFII), a member of the nuclear receptor superfamily, to promote the differentiation of venous ECs, thereby contributing to CV formation. Furthermore, β-catenin stimulated by Bmp promotes the survival of venous ECs, but not that of arterial ECs. Collectively, these results indicate that Bmp-induced activation of β-catenin through Aggf1 regulates CV development by promoting the Nr2f2-dependent differentiation of venous ECs and their survival. This study demonstrates, for the first time, a crucial role of β-catenin-mediated gene expression in the development of venous vessels.

Kashiwada T ，Fukuhara S ，Terai K ，Tanaka T ，Wakayama Y ，Ando K ，Nakajima H ，Fukui H ，Yuge S ，Saito Y ，Gemma A ，Mochizuki N ... -  《-》

Divergence of zebrafish and mouse lymphatic cell fate specification pathways.

van Impel A ，Zhao Z ，Hermkens DM ，Roukens MG ，Fischer JC ，Peterson-Maduro J ，Duckers H ，Ober EA ，Ingham PW ，Schulte-Merker S ... -  《-》