Kuo C T, Veselits M L, Barton K P, Lu M M, Clendenin C, Leiden J M
Committee on Genetics, University of Chicago, Chicago, Illinois 60637, USA.
Genes Dev. 1997 Nov 15;11(22):2996-3006. doi: 10.1101/gad.11.22.2996.
The transcriptional programs that regulate blood vessel formation are largely unknown. In this paper, we examine the role of the zinc finger transcription factor LKLF in murine blood vessel morphogenesis and homeostasis. By in situ hybridization and immunohistochemistry, we show that LKLF is expressed as early as embryonic day 9.5 (E9.5) in vascular endothelial cells throughout the developing mouse embryo. To better understand the function of LKLF, we used homologous recombination in embryonic stem (ES) cells to generate LKLF-deficient (LKLF-/-) mice. Both angiogenesis and vasculogenesis were normal in the LKLF-/- mice. However, LKLF-/- embryos died between E12.5 and E14.5 from severe intra-embryonic and intra-amniotic hemorrhaging. This bleeding disorder was associated with specific defects in blood vessel morphology. Umbilical veins and arteries in the LKLF-/- embryos displayed an abnormally thin tunica media and aneurysmal dilatation before rupturing into the amniotic cavity. Similarly, vascular smooth muscle cells in the aortae from the LKLF-/- animals displayed a cuboidal morphology and failed to organize into a compact tunica media. Consistent with these findings, electron microscopic analyses demonstrated endothelial cell necrosis, significant reductions in the number of vessel-wall pericytes and differentiating smooth muscle cells, and decreased deposition of extracellular matrix in the LKLF-/- vessels. Despite these defects, in situ hybridization demonstrated normal expression of platelet-derived growth factor B, Tie1, Tie2, transforming growth factor beta, and heparin-binding epidermal growth factor in the vasculature of the LKLF-/- embryos. Therefore, LKLF defines a novel transcriptional pathway in which endothelial cells regulate the assembly of the vascular tunica media and concomitant vessel wall stabilization during mammalian embryogenesis.
调节血管形成的转录程序在很大程度上尚不清楚。在本文中，我们研究了锌指转录因子LKLF在小鼠血管形态发生和体内平衡中的作用。通过原位杂交和免疫组织化学，我们发现LKLF早在胚胎第9.5天（E9.5）就在整个发育中的小鼠胚胎的血管内皮细胞中表达。为了更好地理解LKLF的功能，我们利用胚胎干细胞（ES）中的同源重组技术生成了LKLF缺陷（LKLF-/-）小鼠。LKLF-/-小鼠的血管生成和血管发生均正常。然而，LKLF-/-胚胎在E12.5至E14.5之间死于严重的胚胎内和羊膜内出血。这种出血性疾病与血管形态的特定缺陷有关。LKLF-/-胚胎的脐静脉和动脉在破裂进入羊膜腔之前，中膜异常变薄并出现动脉瘤样扩张。同样，LKLF-/-动物主动脉中的血管平滑肌细胞呈现立方形形态，未能组织成紧密的中膜。与这些发现一致，电子显微镜分析显示LKLF-/-血管中存在内皮细胞坏死、血管壁周细胞和分化的平滑肌细胞数量显著减少以及细胞外基质沉积减少。尽管存在这些缺陷，但原位杂交显示血小板衍生生长因子B、Tie1、Tie2、转化生长因子β和肝素结合表皮生长因子在LKLF-/-胚胎的脉管系统中表达正常。因此，LKLF定义了一种新的转录途径，在哺乳动物胚胎发育过程中，内皮细胞通过该途径调节血管中膜的组装和伴随的血管壁稳定。
