UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK.
Development. 2014 Feb;141(3):556-62. doi: 10.1242/dev.103028. Epub 2014 Jan 8.
Neuropilin 1 (NRP1) is a receptor for class 3 semaphorins and vascular endothelial growth factor (VEGF) A and is essential for cardiovascular development. Biochemical evidence supports a model for NRP1 function in which VEGF binding induces complex formation between NRP1 and VEGFR2 to enhance endothelial VEGF signalling. However, the relevance of VEGF binding to NRP1 for angiogenesis in vivo has not yet been examined. We therefore generated knock-in mice expressing Nrp1 with a mutation of tyrosine (Y) 297 in the VEGF binding pocket of the NRP1 b1 domain, as this residue was previously shown to be important for high affinity VEGF binding and NRP1-VEGFR2 complex formation. Unexpectedly, this targeting strategy also severely reduced NRP1 expression and therefore generated a NRP1 hypomorph. Despite the loss of VEGF binding and attenuated NRP1 expression, homozygous Nrp1(Y297A/Y297A) mice were born at normal Mendelian ratios, arguing against NRP1 functioning exclusively as a VEGF164 receptor in embryonic angiogenesis. By overcoming the mid-gestation lethality of full Nrp1-null mice, homozygous Nrp1(Y297A/Y297A) mice revealed essential roles for NRP1 in postnatal angiogenesis and arteriogenesis in the heart and retina, pathological neovascularisation of the retina and angiogenesis-dependent tumour growth.
神经纤毛蛋白 1（NRP1）是一类 3 号信号素和血管内皮生长因子（VEGF）A 的受体，对于心血管发育至关重要。生化证据支持 NRP1 功能的一种模型，即 VEGF 结合诱导 NRP1 和 VEGFR2 之间形成复合物，以增强内皮细胞的 VEGF 信号转导。然而，VEGF 与 NRP1 结合对于体内血管生成的相关性尚未得到检验。因此，我们生成了表达 Nrp1 的敲入小鼠，该蛋白在 NRP1 b1 结构域的 VEGF 结合口袋中的酪氨酸（Y）297 发生突变，因为先前已经表明该残基对于高亲和力 VEGF 结合和 NRP1-VEGFR2 复合物形成非常重要。出乎意料的是，这种靶向策略也严重降低了 NRP1 的表达，因此产生了 NRP1 低功能。尽管 VEGF 结合丧失和 NRP1 表达减弱，纯合子 Nrp1（Y297A/Y297A）小鼠仍以正常孟德尔比例出生，这表明 NRP1 并非在胚胎血管生成中仅作为 VEGF164 受体发挥作用。通过克服完全 Nrp1 缺失小鼠的中期胚胎致死性，纯合子 Nrp1（Y297A/Y297A）小鼠揭示了 NRP1 在心脏和视网膜中的新生血管形成和动脉生成、视网膜病理性新生血管形成以及血管生成依赖性肿瘤生长中的重要作用。
