受体酪氨酸激酶Tie2在血管生成与稳态维持中的调节机制研究

Receptor tyrosine kinase Tie2 is known to be required for blood vascular development. However, it is still incompletely understood about the underlying mechanism of Tie2 function. This project aims to analyse the role of Tie2 mediated signalling in the establishment and maintenance of vascular homeostasis using genetically modified mouse models, including: 1) To employ conditional knockout mouse model targeting Tie2 (Tie2Flox) and transgenic mice expressing CreERT2 recombinase in endothelial cells, we will analyse the effect of Tie2 deletion on blood vascular formation, remodelling and maintenance. 2) To establish conditional knockout mouse model targeting Tie2 tyrosine kinase domain and also mouse model with activation point mutation in Tie2 kinase region, we will analyse the mechanism underlying venous malformation related to the alteration of Tie2 signalling. 3) Using the above genetic models, we will study the role of Tie2 in endothelial cell junction formation as well as the regulation of vascular permeability. 4) To isolate primary blood vascular endothelial cells from wild-type and Tie2 mutant mice, and also generate endothelial cells with point mutations in Tie2 tyrosine kinase domain using the CRISPR/Cas9 technology, we will analyse the difference of gene expression as well as the downstream signalling in endothelial cells after Tie2 mutation. Findings from this study will provide experimental evidence for the elucidation of the mechanism underlying vascular homeostasis and the related diseases.

受体酷氨酸激酶Tie2在血管生成中起重要作用,但目前对于其作用机制还了解很少。本项目将利用靶向Tie2的遗传改造小鼠模型，剖析其在血管生成与稳态维持中的作用机制，具体包括：1）利用Tie2Flox与血管内皮细胞表达Cre重组酶的转基因小鼠,分析在不同阶段诱导敲除Tie2对血管生成、成熟重塑与稳态维持的影响；2）建立Tie2激酶域点突变小鼠模型（Tie2TKmut）及靶向Tie2激酶域的条件性基因敲除小鼠（Tie2TKFlox）, 分析Tie2激酶活性变化导致静脉血管异常的病理机制；3)分析Tie2在血管内皮细胞连接建立与渗透性调节中的作用机制；4）分离带有遗传修饰的原代血管内皮细胞，并利用CRISPR/Cas9技术制备针对Tie2激酶域酪氨酸点突变的内皮细胞株，比较分析野生型与Tie2突变体内皮细胞基因表达及下游信号的差异。研究结果将为阐述血管稳态维持与相关疾病的发生机制提供实验依据。

目前对静脉生成的调控机制尚了解较少。Tie2信号途径在血管内皮细胞存活与血管成熟过程中起重要作用，其激活突变与静脉异常生成有关。本项目利用靶向Tie2的基因敲除小鼠，通过全身性或在内皮细胞特异性诱导敲除Tie2的研究，揭示小鼠胚胎期缺失Tie2或减弱该信号途径能够导致皮肤静脉生成受阻，而且肠系膜动静脉对齐生成异常；出生后诱导敲除Tie2基因可导致视网膜新形成的静脉退化，并伴有血管瘤样血管丛形成，以及成年小鼠皮肤与视网膜静脉曲张等病理变化。进一步的机制研究表明，Tie2信号途径通过调控静脉生成关键转录因子COUP-TFII蛋白的稳定性，从而在静脉分化与维持过程中起关键作用。利用血管生成素（Angiopoietin-1）在血管内皮细胞激活Tie2信号可增加COUP-TFII的蛋白水平，通过siRNA敲降Tie2或PI3K/AKT的抑制剂可降低COUP-TFII的蛋白水平；而且，同时使用蛋白酶体抑制剂MG132处理可逆转AKT抑制剂诱导的COUP-TFII蛋白水平下降。该研究揭示了Tie2-AKT信号途径在静脉内皮细胞命运决定中的关键作用。研究成果为阐明静脉疾病的分子发生机制、以及研制靶向Tie2的血管相关药物提供了重要依据。