title: Notch1 is pan-endothelial at the onset of flow and regulated by flow.
abstract: Arteriovenous differentiation is a key event during vascular development and hemodynamic forces play an important role. Arteriovenous gene expression is present before the onset of flow, however it remains plastic and flow can alter arteriovenous identity. Notch signaling is especially important in the genetic determination of arteriovenous identity. Nevertheless, the effect of the onset of circulation on Notch expression and signaling has not been studied. The aim of this study is therefore to investigate the interaction of Notch1 signaling and hemodynamic forces during early vascular development. We find that the onset of Notch1 expression coincides with the onset of flow, and that expression is pan-endothelial at the onset of circulation in mouse embryos and only becomes arterial-specific after remodeling has occurred. When we ablate flow in the early embryo, endothelial cells fail to express Notch1. We show that low and disturbed flow patterns upregulate Notch1 expression in endothelial cells in vitro, but that higher shear stress levels do not (≥10 dynes/cm2). Using siRNA, we knocked down Notch1 to investigate the role of Notch1 in mechanotransduction. When we applied shear stress levels similar to those found in embryonic arteries, we found an upregulation of Klf2, Dll1, Dll4, Jag1, Hey1, Nrp1 and CoupTFII but that only Dll4, Hey1, Nrp1 and EphB4 required Notch1 for flow-induced expression. Our results therefore indicate that Notch1 can modulate mechanotransduction but is not a critical mediator of the process since many genes mechanotransduce normally in the absence of Notch1, including genes involved in arteriovenous differentiation.
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, 3755 Côte Ste Catherine, Montreal, Quebec, H3T 1E2, Canada; Department of Biomedical Engineering, McGill University, 3775 University St, Montreal, QC, H3A 2B4, Canada.
authors.forename: Espen D
authors.initials: ED
authors.lastname: Jahnsen
authors.affiliation: Centro Interdisciplinar de Investigação em Sanidade Animal, Faculdade de Medicina Veterinária, University of Lisbon, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Trindade
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, 3755 Côte Ste Catherine, Montreal, Quebec, H3T 1E2, Canada.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Zaun
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, 3755 Côte Ste Catherine, Montreal, Quebec, H3T 1E2, Canada.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lehoux
authors.affiliation: Centro Interdisciplinar de Investigação em Sanidade Animal, Faculdade de Medicina Veterinária, University of Lisbon, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Duarte
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, 3755 Côte Ste Catherine, Montreal, Quebec, H3T 1E2, Canada; Department of Biomedical Engineering, McGill University, 3775 University St, Montreal, QC, H3A 2B4, Canada; Department of Cardiovascular Science, KU Leuven, UZ Herestraat 49-box 911, 3000, Leuven, Belgium.
authors.forename: Elizabeth A V
authors.initials: EA
authors.lastname: Jones
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D040542:Mechanotransduction, Cellular; D051379:Mice; D011518:Proto-Oncogene Proteins; D051881:Receptor, Notch1 / Q000502:physiology*; D000074562:Receptor, Notch4; D051880:Receptors, Notch; D012039:Regional Blood Flow; D066253:Vascular Remodeling
chemical_list: D018797:Cell Cycle Proteins; C120420:Hey1 protein, mouse; C497762:Notch1 protein, mouse; D011518:Proto-Oncogene Proteins; D051881:Receptor, Notch1; D000074562:Receptor, Notch4; D051880:Receptors, Notch; C073572:Notch4 protein, mouse
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