Chen Dongying, Wang Xia, Liang Dong, Gordon Julie, Mittal Ashok, Manley Nancy, Degenhardt Karl, Astrof Sophie
Sidney Kimmel Medical College of Thomas Jefferson University, Department of Medicine, Center for Translational Medicine, 1020 Locust Street, Philadelphia, PA 19107, USA; Cell and Developmental Biology graduate program, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA 19107, USA.
Sidney Kimmel Medical College of Thomas Jefferson University, Department of Medicine, Center for Translational Medicine, 1020 Locust Street, Philadelphia, PA 19107, USA.
Dev Biol. 2015 Nov 15;407(2):195-210. doi: 10.1016/j.ydbio.2015.09.016. Epub 2015 Oct 3.
Fibronectin (Fn1) is an evolutionarily conserved extracellular matrix glycoprotein essential for embryonic development. Global deletion of Fn1 leads to mid-gestation lethality from cardiovascular defects. However, severe morphogenetic defects that occur early in embryogenesis in these embryos precluded assigning a direct role for Fn1 in cardiovascular development. We noticed that Fn1 is expressed in strikingly non-uniform patterns during mouse embryogenesis, and that its expression is particularly enriched in the pharyngeal region corresponding with the pharyngeal arches 3, 4, and 6. This region bears a special importance for the developing cardiovascular system, and we hypothesized that the localized enrichment of Fn1 in the pharyngeal region may be essential for cardiovascular morphogenesis. To test this hypothesis, we ablated Fn1 using the Isl1(Cre) knock-in strain of mice. Deletion of Fn1 using the Isl1(Cre) strain resulted in defective formation of the 4th pharyngeal arch arteries (PAAs), aberrant development of the cardiac outflow tract (OFT), and ventricular septum defects. To determine the cell types responding to Fn1 signaling during cardiovascular development, we deleted a major Fn1 receptor, integrin α5 using the Isl1(Cre) strain, and observed the same spectrum of abnormalities seen in the Fn1 conditional mutants. Additional conditional mutagenesis studies designed to ablate integrin α5 in distinct cell types within the Isl1(+) tissues and their derivatives, suggested that the expression of integrin α5 in the pharyngeal arch mesoderm, endothelium, surface ectoderm and the neural crest were not required for PAA formation. Our studies suggest that an (as yet unknown) integrin α5-dependent signal extrinsic to the pharyngeal endothelium mediates the formation of the 4th PAAs.
纤连蛋白（Fn1）是一种在进化上保守的细胞外基质糖蛋白，对胚胎发育至关重要。Fn1的整体缺失会导致因心血管缺陷而在妊娠中期致死。然而，这些胚胎在胚胎发生早期出现的严重形态发生缺陷，使得难以确定Fn1在心血管发育中的直接作用。我们注意到，在小鼠胚胎发生过程中，Fn1以明显不均匀的模式表达，并且其表达在与咽弓3、4和6相对应的咽部区域特别丰富。该区域对发育中的心血管系统具有特殊重要性，我们推测Fn1在咽部区域的局部富集可能对心血管形态发生至关重要。为了验证这一假设，我们使用Isl1（Cre）基因敲入小鼠品系敲除了Fn1。使用Isl1（Cre）品系敲除Fn1导致第四咽弓动脉（PAA）形成缺陷、心脏流出道（OFT）异常发育和室间隔缺损。为了确定在心血管发育过程中对Fn1信号作出反应的细胞类型，我们使用Isl1（Cre）品系敲除了主要的Fn1受体整合素α5，并观察到与Fn1条件性突变体中相同的异常谱。旨在在Isl1（+）组织及其衍生物内的不同细胞类型中敲除整合素α5的其他条件性诱变研究表明，咽弓中胚层、内皮、表面外胚层和神经嵴中整合素α5的表达对于PAA形成并非必需。我们的研究表明，咽内皮外部的一种（尚未明确的）整合素α5依赖性信号介导了第四PAA的形成。
