Cooperative and independent functions of FGF and Wnt signaling during early inner ear development.
Cooperative and independent functions of FGF and Wnt signaling during early inner ear development.
复制标题
DOI：
10.1186/s12861-015-0083-8
复制
发表时间：
2015-10-06
影响因子：
--
通讯作者：
Shim K
中科院分区：
文献类型：
--
作者：
Wright KD;Mahoney Rogers AA;Zhang J;Shim K
在多种脊椎动物生物体中，包括鸡、爪蟾和斑马鱼，成纤维细胞生长因子（FGF）和Wnt信号传导在耳基板的形成期间协作。然而，在小鼠中，虽然FGF信号在耳基板诱导期间诱导Wnt 8a表达，但尚不清楚这两种信号通路是否在功能上合作。Sprouty（Spry）基因编码受体酪氨酸激酶信号传导（包括FGF信号传导）的细胞内拮抗剂。我们以前证明，Sprouty 1（Spry 1）和Sprouty 2（Spry 2）基因拮抗FGF信号在诱导的耳基板。在这里，我们研究了FGF/SPRY和Wnt信号之间的串扰在耳基板诱导和评估这两个信号通路是否在功能上合作在小鼠早期内耳发育。产生携带Spry 1无效等位基因、Spry 2无效等位基因、β-连环蛋白无效等位基因或Wnt报告基因转基因的组合的胚胎。耳表型进行了评估，原位杂交，半定量逆转录酶PCR，免疫组织化学，切片组织的形态学分析。Spry 1、Spry 2和Wnt报告基因在耳前和耳基板细胞中的表达的比较表明FGF信号传导先于Wnt信号传导并且在更多细胞中比Wnt信号传导更活跃。我们提供的体内证据表明，FGF信号激活Wnt信号通路上游的TCF/Lef转录激活。FGF对Wnt信号传导的调节是功能性的，因为Spry 1和Spry 2复合突变体胚胎中的早期内耳缺陷可以通过降低Wnt信号传导途径的活性来遗传拯救。有趣的是，我们发现，虽然在Spry 1和Spry 2复合突变体胚胎中整个耳基板的大小增加，但Wnt报告阳性结构域的大小并没有增加到与Wnt报告阴性结构域相同的程度。这项研究提供了遗传学证据，表明FGF和Wnt信号在小鼠早期内耳发育过程中相互作用。此外，我们的数据表明，虽然规格的耳基板可能是全球性的FGF信号调节，耳规格的细胞，其中FGF和Wnt信号都是积极的，可能会受到更严格的监管。本文的在线版本（doi：10.1186/s12861-015-0083-8）包含补充材料，可供授权用户使用。
In multiple vertebrate organisms, including chick, Xenopus, and zebrafish, Fibroblast Growth Factor (FGF) and Wnt signaling cooperate during formation of the otic placode. However, in the mouse, although FGF signaling induces Wnt8a expression during induction of the otic placode, it is unclear whether these two signaling pathways functionally cooperate. Sprouty (Spry) genes encode intracellular antagonists of receptor tyrosine kinase signaling, including FGF signaling. We previously demonstrated that the Sprouty1 (Spry1) and Sprouty2 (Spry2) genes antagonize FGF signaling during induction of the otic placode. Here, we investigate cross talk between FGF/SPRY and Wnt signaling during otic placode induction and assess whether these two signaling pathways functionally cooperate during early inner ear development in the mouse. Embryos were generated carrying combinations of a Spry1 null allele, Spry2 null allele, β-catenin null allele, or a Wnt reporter transgene. Otic phenotypes were assessed by in situ hybridization, semi-quantitative reverse transcriptase PCR, immunohistochemistry, and morphometric analysis of sectioned tissue. Comparison of Spry1, Spry2, and Wnt reporter expression in pre-otic and otic placode cells indicates that FGF signaling precedes and is active in more cells than Wnt signaling. We provide in vivo evidence that FGF signaling activates the Wnt signaling pathway upstream of TCF/Lef transcriptional activation. FGF regulation of Wnt signaling is functional, since early inner ear defects in Spry1 and Spry2 compound mutant embryos can be genetically rescued by reducing the activity of the Wnt signaling pathway. Interestingly, we find that although the entire otic placode increases in size in Spry1 and Spry2 compound mutant embryos, the size of the Wnt-reporter-positive domain does not increase to the same extent as the Wnt-reporter-negative domain. This study provides genetic evidence that FGF and Wnt signaling cooperate during early inner ear development in the mouse. Furthermore, our data suggest that although specification of the otic placode may be globally regulated by FGF signaling, otic specification of cells in which both FGF and Wnt signaling are active may be more tightly regulated. The online version of this article (doi:10.1186/s12861-015-0083-8) contains supplementary material, which is available to authorized users.