Kanemura Hoshimi, Satoh Takaya, Bilasy Shymaa E, Ueda Shuji, Hirashima Masanori, Kataoka Tohru
Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Japan.
Biochem Biophys Res Commun. 2009 Oct 2;387(4):754-9. doi: 10.1016/j.bbrc.2009.07.108. Epub 2009 Jul 25.
RA-GEF-1 is a guanine nucleotide exchange factor for the small GTPase Rap1. RA-GEF-1 knockout mice show defects in vascular development starting around 7.5days post coitum and die by 9.5days post coitum. Here, we employed in vitro culture systems for allantois explants and endothelial cells to gain insights into the mechanism for RA-GEF-1-mediated regulation of embryonic vascular network formation. The development of the vascular plexus and the accumulation of VE-cadherin at cell-cell junctions were significantly impaired in the RA-GEF-1 knockout allantois and yolk sac. Rap1 activation as visualized by an activation-specific probe was also diminished by RA-GEF-1 knockout. Reduced accumulation of VE-cadherin at cell-cell junctions and defects in blood vessel formation in vitro due to the lack of RA-GEF-1 were suppressed by ectopic expression of constitutively activated Rap1. Overall, these results suggest the involvement of Rap1 downstream of RA-GEF-1 in the regulation of vascular network formation in mouse embryos.
RA-GEF-1是小GTP酶Rap1的鸟嘌呤核苷酸交换因子。RA-GEF-1基因敲除小鼠在交配后约7.5天开始出现血管发育缺陷，并在交配后9.5天死亡。在此，我们利用尿囊外植体和内皮细胞的体外培养系统，以深入了解RA-GEF-1介导的胚胎血管网络形成调节机制。在RA-GEF-1基因敲除的尿囊和卵黄囊中，血管丛的发育以及VE-钙黏蛋白在细胞间连接处的积累均受到显著损害。通过激活特异性探针可视化的Rap1激活也因RA-GEF-1基因敲除而减弱。组成型激活的Rap1的异位表达抑制了由于缺乏RA-GEF-1而导致的细胞间连接处VE-钙黏蛋白积累减少和体外血管形成缺陷。总体而言，这些结果表明RA-GEF-1下游的Rap1参与了小鼠胚胎血管网络形成的调节。
