Copeland Jessica N, Feng Yi, Neradugomma Naveen K, Fields Patrick E, Vivian Jay L
Department of Pathology and Laboratory Medicine and Institute for Reproductive Health and Regenerative Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA.
BMC Dev Biol. 2011 Feb 25;11:12. doi: 10.1186/1471-213X-11-12.
The signaling cascades that direct the morphological differentiation of the vascular system during early embryogenesis are not well defined. Several signaling pathways, including Notch and VEGF signaling, are critical for the formation of the vasculature in the mouse. To further understand the role of Notch signaling during endothelial differentiation and the genes regulated by this pathway, both loss-of-function and gain-of-function approaches were analyzed in vivo.
Conditional transgenic models were used to expand and ablate Notch signaling in the early embryonic endothelium. Embryos with activated Notch1 signaling in the vasculature displayed a variety of defects, and died soon after E10.5. Most notably, the extraembryonic vasculature of the yolk sac displayed remodeling differentiation defects, with greatly enlarged lumens. These phenotypes were distinct from endothelial loss-of-function of RBPJ, a transcriptional regulator of Notch activity. Gene expression analysis of RNA isolated from the yolk sac endothelia of transgenic embryos indicated aberrant expression in a variety of genes in these models. In particular, a variety of secreted factors, including VEGF and TGF-β family members, displayed coordinate expression defects in the loss-of-function and gain-of-function models.
Morphological analyses of the in vivo models confirm and expand the understanding of Notch signaling in directing endothelial development, specifically in the regulation of vessel diameter in the intra- and extraembryonic vasculature. Expression analysis of these in vivo models suggests that the vascular differentiation defects may be due to the regulation of key genes through the Notch-RBPJ signaling axis. A number of these genes regulated by Notch signaling encode secreted factors, suggesting that Notch signaling may mediate remodeling and vessel diameter in the extraembryonic yolk sac via autocrine and paracrine cell communication. We propose a role for Notch signaling in elaborating the microenvironment of the nascent arteriole, suggesting novel regulatory connections between Notch signaling and other signaling pathways during endothelial differentiation.
在胚胎早期发育过程中指导血管系统形态分化的信号级联尚未明确界定。包括Notch和VEGF信号在内的几种信号通路对小鼠血管的形成至关重要。为了进一步了解Notch信号在内皮分化过程中的作用以及受该通路调控的基因，我们在体内分析了功能丧失和功能获得两种方法。
使用条件转基因模型在早期胚胎内皮中扩展和消除Notch信号。血管中Notch1信号激活的胚胎表现出各种缺陷，并在E10.5后不久死亡。最显著的是，卵黄囊的胚外血管显示出重塑分化缺陷，管腔大大扩大。这些表型与Notch活性的转录调节因子RBPJ的内皮功能丧失不同。从转基因胚胎的卵黄囊内皮中分离的RNA的基因表达分析表明，这些模型中多种基因存在异常表达。特别是，包括VEGF和TGF-β家族成员在内的多种分泌因子在功能丧失和功能获得模型中表现出协同表达缺陷。
体内模型的形态学分析证实并扩展了对Notch信号指导内皮发育的理解，特别是在调节胚胎内和胚外血管的血管直径方面。这些体内模型的表达分析表明，血管分化缺陷可能是由于通过Notch-RBPJ信号轴调节关键基因所致。许多受Notch信号调控的这些基因编码分泌因子，表明Notch信号可能通过自分泌和旁分泌细胞通讯介导胚外卵黄囊的重塑和血管直径。我们提出Notch信号在新生小动脉微环境形成中的作用，提示在内皮分化过程中Notch信号与其他信号通路之间存在新的调节联系。
