Sun Hongmin, Yang Tony L, Yang Angela, Wang Xixi, Ginsburg David
Department of Internal Medicine, Division of Molecular Medicine and Genetics, University of Michigan, Ann Arbor, 48109,USA.
Blood. 2003 Oct 15;102(8):2856-61. doi: 10.1182/blood-2003-04-1225. Epub 2003 Jul 10.
Coagulation factor V (FV) is a central regulator of the coagulation cascade. Circulating FV is found in plasma and within platelet alpha granules. The specific functions of these distinct FV pools are uncertain. We now report the generation of transgenic mice with FV gene expression restricted to either the liver or megakaryocyte/platelet lineage using bacterial artificial chromosome (BAC) constructs. Six of 6 independent albumin BAC transgenes rescue the neonatal lethal hemorrhage of FV deficiency. Rescued mice all exhibit liver-specific Fv expression at levels ranging from 6% to 46% of the endogenous Fv gene, with no detectable FV activity within the platelet pool. One of the 3 Pf4 BAC transgenes available for analysis also rescues the lethal FV null phenotype, with FV activity restricted to only the platelet pool (approximately 3% of the wild-type FV level). FV-null mice rescued by either the albumin or Pf4 BAC exhibit nearly normal tail bleeding times. These results demonstrate that Fv expression in either the platelet or plasma FV pool is sufficient for basal hemostasis. In addition, these findings indicate that the murine platelet and plasma FV pools are biosynthetically distinct, in contrast to a previous report demonstrating a plasma origin for platelet FV in humans.
凝血因子V（FV）是凝血级联反应的核心调节因子。循环中的FV存在于血浆和血小板α颗粒中。这些不同FV库的具体功能尚不清楚。我们现在报告利用细菌人工染色体（BAC）构建体生成转基因小鼠，其FV基因表达仅限于肝脏或巨核细胞/血小板谱系。6个独立的白蛋白BAC转基因中有6个挽救了FV缺乏导致的新生儿致死性出血。获救小鼠均表现出肝脏特异性Fv表达，其水平为内源性Fv基因的6%至46%，血小板库中未检测到FV活性。可用于分析的3个Pf4 BAC转基因中有1个也挽救了致死性FV缺失表型，FV活性仅限于血小板库（约为野生型FV水平的3%）。由白蛋白或Pf4 BAC挽救的FV缺失小鼠表现出几乎正常的尾部出血时间。这些结果表明，血小板或血浆FV库中的Fv表达足以实现基础止血。此外，这些发现表明，与之前证明人类血小板FV起源于血浆的报告相反，小鼠血小板和血浆FV库在生物合成上是不同的。
