Sluka Susanna H M, Akhmedov Alexander, Vogel Johannes, Unruh Dusten, Bogdanov Vladimir Y, Camici Giovanni G, Lüscher Thomas F, Ruf Wolfram, Tanner Felix C
Cardiovascular Research, Institute of Physiology, University of Zurich, Zurich, Switzerland; Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland.
PLoS One. 2014 May 30;9(5):e97793. doi: 10.1371/journal.pone.0097793. eCollection 2014.
Tissue factor (TF) triggers blood coagulation and is translated from two mRNA splice isoforms, encoding membrane-anchored full-length TF (flTF) and soluble alternatively-spliced TF (asTF). The complete knockout of TF in mice causes embryonic lethality associated with failure of the yolk sac vasculature. Although asTF plays roles in postnatal angiogenesis, it is unknown whether it activates coagulation sufficiently or makes previously unrecognized contributions to sustaining integrity of embryonic yolk sac vessels. Using gene knock-in into the mouse TF locus, homozygous asTF knock-in (asTFKI) mice, which express murine asTF in the absence of flTF, exhibited embryonic lethality between day 9.5 and 10.5. Day 9.5 homozygous asTFKI embryos expressed asTF protein, but no procoagulant activity was detectable in a plasma clotting assay. Although the α-smooth-muscle-actin positive mesodermal layer as well as blood islands developed similarly in day 8.5 wild-type or homozygous asTFKI embryos, erythrocytes were progressively lost from disintegrating yolk sac vessels of asTFKI embryos by day 10.5. These data show that in the absence of flTF, asTF expressed during embryonic development has no measurable procoagulant activity, does not support embryonic vessel stability by non-coagulant mechanisms, and fails to maintain a functional vasculature and embryonic survival.
组织因子（TF）触发血液凝固，由两种mRNA剪接异构体翻译而来，分别编码膜锚定的全长TF（flTF）和可溶性可变剪接TF（asTF）。小鼠TF的完全敲除会导致胚胎致死，这与卵黄囊脉管系统功能衰竭有关。尽管asTF在出生后血管生成中发挥作用，但尚不清楚它是否能充分激活凝血，或者是否对维持胚胎卵黄囊血管的完整性有此前未被认识到的作用。通过将基因敲入小鼠TF基因座，纯合asTF敲入（asTFKI）小鼠在缺乏flTF的情况下表达鼠asTF，在第9.5天至10.5天之间表现出胚胎致死性。第9.5天的纯合asTFKI胚胎表达asTF蛋白，但在血浆凝血试验中未检测到促凝血活性。尽管在第8.5天的野生型或纯合asTFKI胚胎中，α-平滑肌肌动蛋白阳性的中胚层以及血岛发育相似，但到第10.5天时，asTFKI胚胎解体的卵黄囊血管中的红细胞逐渐丢失。这些数据表明，在缺乏flTF的情况下，胚胎发育过程中表达的asTF没有可测量的促凝血活性，不能通过非凝血机制支持胚胎血管稳定性，也无法维持功能性脉管系统和胚胎存活。
