Abstract 541: Nogo-B Receptor Is Essential for Embryonic Stem Cell Differentiation to Endothelial Cell Lineage and Primitive Blood Vessel Formation
Nogo isoforms-A, -B, and -C, are members of the reticulon family of proteins. Nogo-B was previously identified as a protein that is highly expressed in caveolin-1 enriched microdomains and/or lipid rafts of endothelial cells (EC) and vascular smooth muscle cells. Mice deficient in Nogo-A/B show exaggerated neointimal proliferation, abnormal remodeling and a deficit in ischemia induced arteriogenesis and angiogenesis. Nogo-B receptor (NgBR) is a type I receptor with a single transmembrane domain, and was identified as a receptor specific for Nogo-B. Our previous work has shown that Nogo-B and its receptor (NgBR) are essential for chemotaxis and morphogenesis of endothelial cells in vitro and intersomitic vessel formation in zebrafish via Akt pathway. Here, we further demonstrated the role of NgBR in regulating the differentiation of murine embryonic stem cells (ESC) into endothelial cell lineage and primitive blood vessel formation in 2D or 3D embryoid body culture systems. Murine NgBR gene-targeting ESC was generated by either gene-trap or homologous recombination approaches, respectively. Gene-targeting of NgBR was confirmed by Southern blot and qPCR. Homozygous knockout of NgBR in ESC results in cell apoptosis. Heterozygous knockout of NgBR does not affect ESC cell survival, but decreases the endothelial cell lineage commitment as well as reduces the formation and branching of primitive blood vessels in 2D or 3D embryoid body culture systems. However, there is no effect on the differentiation of ESC to vascular smooth muscle cell lineage. Mechanistically, NgBR has two potential regulatory roles during embryonic vasculature development. NgBR knockdown not only impairs both Nogo-B and VEGF-stimulated endothelial cell migration by abolishing Akt phosphorylation, but also decreases endothelial cell lineage commitment by delaying BMP4 production during the period of mesoderm formation. These results suggest that NgBR may be one of important genes coordinating the vasculature development.
- © 2012 by American Heart Association, Inc.