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Abstract：
Within the developing embryo, cells assemble and remodel their surrounding extracellular matrix during morphogenesis. Fibronectin is an extracellular matrix glycoprotein and is a ligand for several members of the Integrin adhesion receptor family. Here, we compare the expression pattern and loss of function phenotypes of the two zebrafish fibronectin paralogs fn1a and fn1b. We engineered two fluorescently tagged knock-in alleles to facilitate live in vivo imaging of the Fibronectin matrix. Genetic complementation experiments indicate that the knock-in alleles are fully functional. Fn1a-mNeonGreen and Fn1b-mCherry are co-localized in ECM fibers on the surface of the paraxial mesoderm and myotendinous junction. In 5-days old zebrafish larvae, Fn1a-mNeonGreen predominantly localizes to the branchial arches, heart ventricle, olfactory placode and within the otic capsule while Fn1b-mCherry is deposited at the pericardium, proximal convoluted tubule, posterior hindgut and at the ventral mesoderm/cardinal vein. We examined Fn1a-mNeonGreen and Fn1b-mCherry in maternal zygotic integrin α5 mutants and integrin β1a; β1b double mutants and find distinct requirements for these Integrins in assembling the two Fibronectins into ECM fibers in different tissues. Rescue experiments via mRNA injection indicate that the two fibronectins are not fully inter-changeable. Lastly, we examined cross-regulation between the two Fibronectins and find fn1a is necessary for normal Fn1b fibrillogenesis in the presomitic mesoderm, but fn1b is dispensable for the normal pattern of Fn1a deposition.
摘要：
在发育中的胚胎中，细胞在形态发生过程中组装并重塑其周围的细胞外基质。纤连蛋白是一种细胞外基质糖蛋白，是整联蛋白粘附受体家族几个成员的配体。这里,我们比较了两种斑马鱼纤连蛋白同源物fn1a和fn1b的表达模式和功能表型缺失。我们设计了两个荧光标记的敲入等位基因，以促进纤连蛋白基质的活体内成像。遗传互补实验表明敲入等位基因是完全功能性的。Fn1a-mNeonGreen和Fn1b-mCherry共定位在旁轴中胚层和肌肌腱连接处表面的ECM纤维中。在5天大的斑马鱼幼虫中，Fn1a-mNeonGreen主要位于分支弓，心脏心室,嗅觉胎盘和耳囊内，而Fn1b-mCherry沉积在心包，近曲小管，后肠和腹侧中胚层/主静脉。我们检查了母体合子整合素α5突变体和整合素β1a中的Fn1a-mNeonGreen和Fn1b-mCherry；β1b双突变体，并发现了这些整合素在将两种纤连体蛋白组装成不同组织中的ECM纤维时对这些整合素的不同要求。通过mRNA注射的挽救实验表明两种纤连蛋白不是完全可互换的。最后,我们检查了两种纤维连接蛋白之间的交叉调节，发现fn1a是正常的Fn1b纤维形成所必需的，但Fn1b对于Fn1a沉积的正常模式是不必要的。
