From vascular tissue mechanics to Klf2 transcription factor-induced angiogenesis

在血管系统中，机械转导通路在血液流动或基底膜僵硬引起的机械刺激下被激活，在血管组织的发育和动态平衡中发挥重要作用。内皮细胞有许多力学转导分子，包括细胞-细胞连接处的钙粘附素和细胞-基质粘附处的整合素。这位法国合作伙伴最近证明，CCM复合体在一种遗传性和散发性脑血管疾病(脑海绵状血管畸形病理)中被耗尽，在依赖VE-钙粘附素的细胞与细胞之间的相互作用和依赖于β1整合素的细胞-ECM黏附之间起着一个节点的作用。当失去CCM蛋白复合体时，由于β1整合素的激活，细胞外基质的力学发生改变，并通过减弱VE-钙粘附素介导的细胞-细胞黏附和通过增加内皮通透性反馈到内皮细胞。这位德国合作伙伴证明，机械敏感转录因子KLF2在斑马鱼CCM2突变胚胎中上调，击倒KLF2可以恢复正常的心血管发育。双方合作发现，β1整合素参与了KLF2表达的上调。KLF2的高表达通过诱导ECM相关蛋白Egfl7导致斑马鱼CCM突变表型，Egfl7是Notch信号的负调控因子和Beta3整合素信号的激活因子。我们正在进行的合作支持这一假设，即CCM蛋白丢失时血管生成程序的激活可能由Beta1和Beta3整合素信号协调，进而刺激促血管生成KLF2机械敏感反应。首先，这项拨款提案旨在阐明在发育过程中和CCM病理生理条件下，β1整合素调节KLF2机械转导途径的收缩和信号通路。其次，我们将研究KLF2信号调节内皮细胞MT过程和内皮稳定性的机制(S)。我们的合作将斑马鱼模型的遗传学和发育生物学的力量与与创新生物物理研究相关的体外受控细胞培养的深入机制方法结合在一起。这个项目是一个跨学科的方法，旨在研究机械转导在心血管发育和CCM疾病中的作用，CCM疾病是脑血管系统的一种相关病理。

In the vascular system, mechanotransduction pathways are activated in response to mechanical stimuli induced by blood flow or basement membrane stiffness and play important roles during the development and in the homeostasis of vascular tissues. Endothelial cells have numerous mechanotransducers including cadherins at cell-cell junctions and integrins at cell-matrix adhesions. The French partner recently demonstrated that the CCM complex, depleted in a hereditary and sporadic cerebrovascular disease (the Cerebral Cavernous Malformation pathology), functions as a node between VE-cadherin-dependent cell-cell interactions and beta1 integrin-dependent cell-ECM adhesion. Upon loss of the CCM protein complex, extracellular matrix mechanics is changed due to beta1 integrin activation and feeds back onto endothelial cells by weakening VE-cadherin-mediated cell-cell adhesion and by raising endothelial permeability. The German partner demonstrated that the mechanosensitive transcription factor Klf2 is upregulated in zebrafish ccm2 mutant embryos and that knocking down Klf2 restores normal cardiovascular development. Collaboratively, both partners found that beta1 integrin is involved in the upregulation of Klf2 expression. High expression levels of Klf2 contribute to the ccm mutant phenotype in zebrafish through induction of Egfl7, an ECM-associated protein, which functions as a negative regulator of Notch signaling and activator of beta3 integrin signaling. Our ongoing collaboration supports the hypothesis that the activation of an angiogenesis program upon loss of CCM proteins might be orchestrated by beta1 and beta3 integrin signaling, which in turn stimulates the proangiogenic Klf2 mechanosensitive response. First, this grant proposal aims at elucidating the contractile and signaling pathways by which beta1 integrin regulates the Klf2 mechanotransduction pathway during development and under CCM pathophysiological conditions. Secondly, we will investigate the mechanism(s) by which Klf2 signaling regulates endoMT processes and endothelial stability. Our collaboration brings together the power of genetics and developmental biology of the zebrafish model with the in-depth mechanistic approach of in vitro controlled cell culture associated with innovative biophysical studies. This project is an interdisciplinary approach that aims at investigating the role of mechanotransduction in cardiovascular development and in the CCM disease, which is an associated pathology of the cerebrovasculature.