ProNodal acts via FGFR3 to govern duration of Shh expression in the prechordal mesoderm.
ProNodal acts via FGFR3 to govern duration of Shh expression in the prechordal mesoderm.
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DOI：
10.1242/dev.119628
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发表时间：
2015-11-15
期刊：
影响因子：
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通讯作者：
Placzek M
中科院分区：
文献类型：
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作者：
Ellis PS;Burbridge S;Soubes S;Ohyama K;Ben-Haim N;Chen C;Dale K;Shen MM;Constam D;Placzek M
分泌型糖蛋白sonic hedgehog(Shh)在脊索前中胚层表达，在腹侧前脑的诱导和模式形成中起关键作用。目前，关于Shh在前索组织中是如何调控的知之甚少。在这里，我们发现在胚胎雏鸡中，Shh在前索中胚层中瞬时表达，并由未加工的Nodal控制。将前索中胚层微培养细胞暴露在Nodal条件培养液、Nodal抑制剂CERs或ALK4/5/7抑制剂中，发现Nodal是维持Shh和GSC表达所必需的，但GSC主要是通过规范信号来维持的，Nodal信号是通过非规范途径来维持Shh的。此外，Shh的表达可被重组Nodal裂解突变体proNodal维持，但不能被纯化的成熟Nodal维持。一系列证据表明，pronodal通过FGFR3发挥作用。ProNodal和FGFR3免疫共沉淀，ProNodal增加FGFR3酪氨酸磷酸化。在微培养中，可溶性FGFR3可在不影响GSC表达的情况下取消Shh。此外，FGFR3 siRNA下调FGFR3表达的脊索前中胚层细胞无法与ProNodal结合。最后，在体内，将FGFR3 siRNA定向电穿孔到索前中胚层会导致Shh过早下调，而不会影响GSC。我们报告了proNodal-FGFR3信号和pSmad1/5/8之间的负相关关系，并表明proNodal-FGFR3信号对抗BMP介导的pSmad1/5/8信号，这可能下调Shh。我们的研究表明，proNodal/FGFR3信号通过抑制典型的BMP信号来控制Shh持续时间，一旦内源性Nodal-FGFR3信号下调，局部BMP就会迅速抑制Shh。重点文章：在鸡脊索前中胚层中，结节前体proNodal通过非规范途径抑制BMP信号，从而维持Shh的表达
The secreted glycoprotein sonic hedgehog (Shh) is expressed in the prechordal mesoderm, where it plays a crucial role in induction and patterning of the ventral forebrain. Currently little is known about how Shh is regulated in prechordal tissue. Here we show that in the embryonic chick, Shh is expressed transiently in prechordal mesoderm, and is governed by unprocessed Nodal. Exposure of prechordal mesoderm microcultures to Nodal-conditioned medium, the Nodal inhibitor CerS, or to an ALK4/5/7 inhibitor reveals that Nodal is required to maintain both Shh and Gsc expression, but whereas Gsc is largely maintained through canonical signalling, Nodal signals through a non-canonical route to maintain Shh. Further, Shh expression can be maintained by a recombinant Nodal cleavage mutant, proNodal, but not by purified mature Nodal. A number of lines of evidence suggest that proNodal acts via FGFR3. ProNodal and FGFR3 co-immunoprecipitate and proNodal increases FGFR3 tyrosine phosphorylation. In microcultures, soluble FGFR3 abolishes Shh without affecting Gsc expression. Further, prechordal mesoderm cells in which Fgfr3 expression is reduced by Fgfr3 siRNA fail to bind to proNodal. Finally, targeted electroporation of Fgfr3 siRNA to prechordal mesoderm in vivo results in premature Shh downregulation without affecting Gsc. We report an inverse correlation between proNodal-FGFR3 signalling and pSmad1/5/8, and show that proNodal-FGFR3 signalling antagonises BMP-mediated pSmad1/5/8 signalling, which is poised to downregulate Shh. Our studies suggest that proNodal/FGFR3 signalling governs Shh duration by repressing canonical BMP signalling, and that local BMPs rapidly silence Shh once endogenous Nodal-FGFR3 signalling is downregulated. Highlighted article: In the chick prechordal mesoderm, the Nodal precursor proNodal acts via a non-canonical route to inhibit BMP signalling and thus maintain Shh expression