Data Sheet 1_Endothelial Zmiz1 modulates developmental angiogenesis in the retina.pdf

Angiogenesis is a highly coordinated process involving the control of various endothelial cell behaviors. Mechanisms for transcription factor involvement in the regulation of endothelial cell dynamics and angiogenesis have become better understood, however much remains unknown, especially the role of non-DNA binding transcriptional cofactors. Here, we show that Zmiz1, a transcription cofactor, is enriched in the endothelium and critical for embryonic vascular development, postnatal retinal angiogenesis, and pathological angiogenesis in a model of oxygen-induced retinopathy (OIR). In mice, endothelial cell-specific deletion of Zmiz1 during embryogenesis led to lethality due to abnormal angiogenesis and vascular defects. Inducible endothelial cell-specific ablation of Zmiz1 postnatally resulted in impaired retinal vascular outgrowth, decreased vascular density, and increased vessel regression. In addition, angiogenic sprouting in the superficial and deep layers of the retina was markedly reduced. Correspondingly, vascular sprouting in fibrin bead assays was significantly reduced in the absence of Zmiz1, while further in vitro and in vivo evidence also suggested deficits in EC migration. In agreement with the defective sprouting angiogenesis phenotype, gene expression analysis of isolated retinal endothelial cells revealed downregulation of tip-cell enriched genes upon inactivation of Zmiz1. Lastly, our study suggested that endothelial Zmiz1 is critical for intraretinal revascularization following hypoxia exposure in the OIR model. Taken together, these findings begin to define the previously unspecified role of endothelial Zmiz1 in physiological and pathological angiogenesis.

血管生成（Angiogenesis）是一类高度协同的精密生物学过程，涉及多种内皮细胞行为的精准调控。此前，转录因子（transcription factor）参与调控内皮细胞动态变化与血管生成的机制已逐步得到阐明，但仍有诸多科学问题有待破解，尤其是非DNA结合型转录辅因子（transcriptional cofactors）所发挥的功能。本研究发现，转录辅因子Zmiz1在内皮细胞中特异性富集，且对胚胎血管发育、出生后视网膜血管生成以及氧诱导性视网膜病变（Oxygen-induced retinopathy, OIR）模型中的病理性血管生成均具有不可或缺的关键作用。在小鼠模型中，胚胎阶段内皮细胞特异性敲除Zmiz1会因异常血管生成与血管结构缺陷导致胚胎致死；出生后通过诱导实现的内皮细胞特异性敲除Zmiz1，则会引发视网膜血管生长受阻、血管密度降低以及血管退化程度加剧。此外，视网膜浅层与深层的血管出芽生长均受到显著抑制。相应地，在缺乏Zmiz1的情况下，纤维蛋白微球实验（fibrin bead assays）中的血管出芽活动显著减少；进一步的体内外实验也证实，内皮细胞的迁移功能存在明显缺陷。与受损的出芽性血管生成表型相符，对分离得到的视网膜内皮细胞进行基因表达分析后发现，Zmiz1失活后，顶端细胞（tip-cell）富集基因的表达水平显著下调。最后，本研究表明，在氧诱导性视网膜病变模型中，缺氧暴露后的视网膜内血管重建过程同样依赖于内皮细胞Zmiz1的正常功能。综上，本研究首次阐明了内皮细胞Zmiz1在生理性与病理性血管生成中此前未被明确的关键调控作用。