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Multiple signaling pathways control the specification of endothelial cells (ECs) to become arteries or veins during vertebrate embryogenesis. Current models propose that a cascade of Hedgehog (Hh), vascular endothelial growth factor (VEGF), and Notch signaling acts instructively on ECs to control the choice between arterial or venous fate. Differences in the phenotypes induced by Hh, VEGF, or Notch inhibition suggest that not all of the effects of Hh on arteriovenous specification are mediated by VEGF. We establish that full derepression of the Hh pathway in ptc1;ptc2 mutants converts the posterior cardinal vein into a second arterial vessel that manifests intact arterial gene expression, intersegmental vessel sprouting, and HSC gene expression. Importantly, although VEGF was thought to be absolutely essential for arterial fates, we find that normal and ectopic arterial differentiation can occur without VEGF signaling in ptc1;ptc2 mutants. Furthermore, Hh is able to bypass VEGF to induce arterial differentiation in ECs via the calcitonin receptor-like receptor, thus revealing a surprising complexity in the interplay between Hh and VEGF signaling during arteriovenous specification. Finally, our experiments establish a dual function of Hh during induction of runx1(+) HSCs.

Original publication

DOI

10.1182/blood-2011-10-383729

Type

Journal article

Journal

Blood

Publication Date

12/07/2012

Volume

120

Pages

477 - 488

Keywords

Animals, Animals, Genetically Modified, Arteries, Calcitonin Receptor-Like Protein, Core Binding Factor Alpha 2 Subunit, Gene Expression Regulation, Developmental, Gene Knockdown Techniques, Hedgehog Proteins, Hematopoietic Stem Cells, Mutation, Patched Receptors, Patched-1 Receptor, Receptors, Cell Surface, Receptors, Notch, Signal Transduction, Vascular Endothelial Growth Factor A, Zebrafish, Zebrafish Proteins