Syndecan-2 is essential for angiogenic sprouting during zebrafish development

Abstract

We used a morpholino-based gene-targeting screen to identify a novel protein essential for vascular development using the zebrafish, Danio rerio. We show that syndecan-2, a cell-surface heparan sulfate proteoglycan, is essential for angiogenic sprouting during embryogenesis. The vascular function of syndecan-2 is likely conserved, as zebrafish and mouse syndecan-2 show similar expression patterns around major trunk vessels, and human syndecan-2 can restore angiogenic sprouting in syndecan-2 morphants. In contrast, forced expression of a truncated form of syndecan-2 results in embryos with defects in angiogenesis, indicating that the highly conserved cytoplasmic tail is important for the vascular function of syndecan-2. We further show that vascular endothelial growth factor (VEGF) and syndecan-2 genetically interact in vivo using both gain-of-function and loss-offunction studies in zebrafish. VEGF-mediated ectopic signaling is compromised in syndecan-2 morphants, and ectopic syndecan-2 potentiates ectopic VEGF signaling. Syndecan-2 as a novel angiogenic factor is a potential candidate for use in the development of angiogenesis-based therapies. IntroductionVascular formation is composed of 2 processes, vasculogenesis and angiogenesis. In vasculogenesis, angioblasts derived from the lateral mesoderm migrate and differentiate into endothelial cells that form the tubular structures of primary vasculature. In angiogenesis, new vessels sprout from pre-existing vasculature and are further remodeled to form mature blood vessels. Angiogenesis is an important process during development, various physiologic phenomena, and pathologic conditions such as tumor growth and diabetic retinopathy. 1 Growth factors such as vascular endothelial growth factor (VEGF), angiopoietins, and ephrins play key roles during angiogenesis. [1][2][3] Identification and characterization of novel angiogenic factors during vertebrate development may further the understanding of key molecular players in angiogenesis as well as hold promise for potential application in angiogenesis-based therapies. [4][5][6] Conservation of vascular development in vertebrates 7 and the capacity to effectively target this process using morpholinos 8 allowed us to embark on a morpholino-based screen for novel angiogenic factors using zebrafish as the model system. Morpholinos were designed based on 5Ј leader sequences from a collection of zebrafish expressed sequence tags (ESTs) with high homology to human, Drosophila, or Fugu gene. Bioinformatics methods to enrich for partial sequences of cell-surface or secreted proteins based on full-length reference protein data sets have been determined as previously described. 9 As part of this ongoing effort, we have identified syndecan-2 (syn-2), a cell-surface heparan sulfate proteoglycan, as a novel factor essential for angiogenic sprouting during vascular development.Previous studies have demonstrated the important roles played by heparan sulfate proteoglycans (HSPGs) in a variety of biologic processes such as early embryon...

Extra-embryonic syndecan 2 regulates organ primordia migration and fibrillogenesis throughout the zebrafish embryo

“…4). Further evidence for a functional difference between embryonic and extra-embryonic Sdc2 comes from traditional morphant studies in which knockdown of sdc2 in embryonic cells alters angiogenesis (Chen et al, 2004) and left-right patterning (data not shown) but does not lead to a bifid heart or gut. Although it is possible that extra-embryonic Sdc2 modulates a signal in the YSL that induces secretion of an unknown signal out of the YSL into the embryo to mediate fibrillogenesis, cell polarization and cell migration in the embryo, or that extraembryonic Sdc2 plays a role in yolk syncytial nuclei movement that somehow modulates cardiac primordia patterning (Carvalho et al, 2009), a more parsimonious explanation is that extra-embryonic Sdc2 directly controls fibrillogenesis at the YSL-embryo interface and subsequently controls cell migration.…”

Cooperative interaction of Angiopoietin-like proteins 1 and 2 in zebrafish vascular development

“…Zangptl1 is expressed in the myotome, and Zangptl2 is predominantly expressed in the yolk sac extension, especially in the yolk syncytial layer and the spinal cord, suggesting that both factors might act on endothelial cells of ISVs sprouting toward such structures. To examine the physiological functions of both genes simultaneously, we used a loss-offunction strategy by using morpholinos, an antisense technology widely used to knockdown multiple genes predicted to act cooperatively (26,27). Our studies indicate that both Angptl1 and Angptl2 possess antiapoptotic activity through the phosphatidylinositol 3-kinase (PI3-K)͞Akt pathway and that their cooperative activities are required for vascular development in zebrafish embryogenesis.…”

Transmembrane domains of the syndecan family of growth factor coreceptors display a hierarchy of homotypic and heterotypic interactions

“…In mammals, where four syndecan paralogs exist (1)(2)(3)(4)(5), syndecan expression is tissue-specific and developmentally regulated, with most cells expressing one or more syndecans (6,7). Syndecan-1 plays roles in early development (8)(9)(10) and wound healing (11), and syndecan-2 participates in neuronal dendritic spine morphogenesis (12), angiogenic sprouting (13), and Xenopus left/right axis formation (14). Syndecan-3 is involved in skeletogenesis (15), and syndecan-4 participates in the formation of integrin-containing focal adhesions (16).…”