Fox genes in arterial-venous endothelial cell identity

描述（由申请人提供）：成人循环系统中的动脉和静脉在解剖学上是不同的，以前认为动脉和静脉内皮细胞的分化特性是对血液动力学力（如血压和血流方向）的反应。然而，最近的证据表明，动脉和静脉的规格/分化是由遗传机制之前的积极循环开始。该事件发生在血管重塑之前，动脉和静脉的特化/分化受损导致血管重塑失败。虽然已经表明，几个信号系统，如VEGF，Notch和ephrin信号通路参与了这一过程，转录因子如何发挥作用，以调节这些基因的表达的分子机制仍有待阐明。我们以前已经表明，两个基因编码密切相关的福克斯转录因子，Foxc 1和Foxc 2，在重叠的细胞群中表达，有助于血管的内皮细胞和间充质细胞。缺乏Foxc 1或Foxc 2的胚胎，以及大多数复合杂合子，在产前或围产期死亡，具有相似的异常表型，包括心血管系统的缺陷。复合Foxc 1; Foxc 2纯合子比单一纯合子死亡更早，缺陷更严重。最重要的是，复合纯合子具有动静脉畸形和血管重塑失败，并且在复合纯合子的内皮细胞中Notch信号基因和ephrinB 2下调。这些数据导致中心的假设，Foxc 1和Foxc 2在动脉-静脉细胞命运决定/分化的过程中发挥剂量依赖性，相互作用。这项资助的目标之一是测试Foxc蛋白是否在VEGF信号传导的下游起作用，以调节动脉-静脉特性（Aim 1）。将通过（a）分析与Tie 2-Cre小鼠杂交的内皮细胞中的Foxc 1和Foxc 2的条件性复合突变体和（B）拯救实验来检验所提出的假设，其中Tie 2-Foxc转基因小鼠与复合Foxc 1; Foxc 2突变体杂交（目的2）。最后，将鉴定在动脉和静脉的特化/分化过程中由Foxc 1和Foxc 2调节的直接靶基因（目的3）。阐明Foxcl/c2在血管发育过程中如何发挥作用的分子机制将显著有助于我们了解基因如何合作控制哺乳动物心血管发育，并将导致更好地了解人类先天性缺陷。

DESCRIPTION (provided by applicant): Arteries and veins are anatomically distinct within the adult circulatory system, and it was previously thought that the differentiated identities of arterial and venous endothelial cells arose in response to hemodynamic forces such as blood pressure and the direction of blood flow. However, recent evidence suggests that the specification/differentiation of arteries and veins is governed by genetic mechanisms before the active onset of circulation. This event occurs before remodeling of blood vessels, and impaired specification/differentiation of arteries and veins leads to failure to remodel blood vessels. Although it has been shown that several signaling systems such as the VEGF, Notch, and ephrin signaling pathways are involved in this process, molecular mechanisms of how transcription factors function to regulate expression of such genes remain to be elucidated. We have previously shown that the two genes encoding closely related Fox transcription factors, Foxc1 and Foxc2, are expressed in overlapping populations of cells contributing to the endothelial and mesenchymal cells of the blood vessels. Embryos lacking either Foxc1 or Foxc2, and most compound heterozygotes, die pre or perinatally with similar abnormal phenotypes, including defects in the cardiovascular system. Compound Foxc1; Foxc2 homozygotes die earlier and with much more severe defects than single homozygotes alone. Most importantly, compound homozygotes have arteriovenous malformations and the failure of blood vessels to remodel, and in the endothelial cells of compound homozygotes Notch signaling genes and ephrinB2 are downregulated. These data lead to the central hypothesis that Foxc1 and Foxc2 play dose-dependent, interactive roles in the process of arterial-venous cell fate determination/differentiation. One of the goals of this grant is to test whether Foxc proteins act downstream of VEGF signaling to regulate arterial-venous identity (Aim 1). The proposed hypothesis will be tested by (a) analyzing conditional compound mutants of Foxc1 and Foxc2 in endothelial cells crossed with Tie2-Cre mice and (b) rescue experiments in which Tie2-Foxc transgenic mice are crossed with compound Foxcl; Foxc2 mutants (Aims 2). Finally, direct target gene(s) regulated by Foxc1 and Foxc2 in the process of specification/differentiation of arteries and veins will be identified (Aim 3). Elucidating the molecular mechanisms of how Foxcl/c2 function during vascular development will significantly contribute to our knowledge of how genes cooperate to control mammalian cardiovascular development and will lead to a better understanding of human congenital defects.