Molecular signaling in aortic valve development and congenital aortic valve defect

摘要 正常的主动脉瓣为三尖瓣，有来自多个细胞系的三片叶。 胚胎发生。主动脉瓣的模式是由基因控制的，瓣膜中的单个细胞- 形成场决定了它们的命运和功能，以响应位置和环境的暗示。遗传 改变细胞-细胞和细胞环境信号的突变可以扰乱发育过程， 导致主动脉瓣畸形，例如二尖瓣(BAV)。影响~2%的 在美国普通人群中，BAV是最常见的先天性心脏病。三个中的两个融合 在胚胎发育过程中出现小叶或缺少一个小叶会导致不同的BAV亚型。出生后， 超过一半的BAV患者在没有有效药物的情况下发展为钙化性主动脉瓣疾病，而BAV亚型 有各种各样的心脏并发症，这决定了疾病的结局。与国际双尖瓣大动脉 瓣膜联盟(BAVCon)正在成立，以确定BAV在人类、动物模型中的遗传原因 为了阐明人BAV的形态发生和细胞机制，以及 控制主动脉瓣形态以确定疾病治疗靶点的分子信号 预防。为此，我们已经建立了两种BAV小鼠模型，它们具有明显的信号缺陷和 反常的传单。在第一个模型中，敲除瓣膜心内膜细胞(VECs)中的Notch1受体(Notch1) 概括了最常见的人类BAV亚型-左和右冠状动脉叶融合，主要是 血管内皮细胞经上皮细胞向间充质细胞转化。该模型还揭示了NOTCH1- 血管内皮细胞的TNFa信号调控瓣膜间充质细胞的凋亡。在第二个模型中，删除 血管内皮细胞中SRY-box转录因子17(Sox17)导致一种罕见但更严重的BAV缺失型 非冠状叶，其中VMC主要来自第二心场(SHF)来源 这种图案化缺陷与VEC-VMC PDGFB信号的减少有关。基于 这些发现，我们假设协调的VEC-VMC信号控制正常的主动脉瓣模式和 它们的破坏导致了不同的BAV亚型，在受影响细胞的来源和位置的背景下。我们会 在两个目标上检验这一假设。AIM 1计划在正常情况下揭示协调的VEC-VMC信号网络 主动脉瓣模式和识别在不同BAV亚型中被破坏的信号事件。AIM 2是专门设计的 揭示PDGF信号在正常主动脉瓣形成中的作用，并以此为例 说明中断的信号事件如何改变细胞的命运和功能，从而导致特定的BAV。成功 这些目标的实现将为BAV的发病机制提供新的见解，并具有广泛的意义 先天性心脏瓣膜病。

ABSTRACT The normal aortic valve is tricuspid with three leaflets derived from multiple cell lineages during embryogenesis. Aortic valve patterning is genetically controlled where individual cells in the valve- forming field refine their fates and functions in response to positional and environmental cues. Genetic mutations that alter cell-cell and cell-environmental signals can disrupt the developmental process, leading to anomalous aortic valve, for example, bicuspid aortic valve (BAV). Affecting ~2% of the general population in US, BAV is the most common congenital heart defect. Fusion of two of three leaflets or absence of one leaflet during embryogenesis results in various BAV subtypes. After birth, over half of BAV patients develop calcific aortic valve disease with no effective medicine, while BAV subtypes have varied cardiac complications, which decide the disease outcome. With the International Bicuspid Aortic Valve Consortium (BAVCon) being established to identify the genetic causes of BAV in humans, animal models of BAV are critically needed to elucidate morphogenic and cellular mechanisms of human BAV, as well as molecular signals that control aortic valve patterning in order to identify therapeutic targets for disease prevention. To this end, we have generated two mouse models of BAV with distinct signaling defects and anomalous leaflets. In the first model, knocking out notch receptor 1 (Notch1) in valve endocardial cells (VECs) recapitulates the most common human BAV subtype – fusion of left and right coronary leaflets, which are mainly derived from VECs by epithelial to mesenchymal transformation. This model also reveals that the NOTCH1- TNFa signaling from VECs controls apoptosis of valve mesenchymal cells (VMCs). In the second model, deleting SRY-box transcription factor 17 (Sox17) in VECs results in a rare but more severe type of BAV – absence of non-coronary leaflet, of which VMCs arise predominantly from the second heart field (SHF)-derived cardiomyocytes, and the patterning defect is associated with reduced VEC-VMC PDGFB signaling. Based on these findings, we hypothesize that coordinated VEC-VMC signals control normal aortic valve patterning and their disruption leads to various BAV subtypes, in the context of the origin and location of affected cells. We will test this hypothesis in two Aims. Aim 1 is planned to reveal coordinated VEC-VMC signal networks during normal aortic valve patterning and identify signaling events that are disrupted in various BAV subtypes. Aim 2 is designed to uncover the functions of PDGF signaling in normal aortic valve patterning as well as use it as an example to illustrate how a disrupted signaling event can alters cell fate and function, leading to a specific BAV. Successful accomplishment of these Aims will provide new insights into BAV pathogenesis, with a broad implication in congenital heart valve disease.