Range Ryan, Lapraz François, Quirin Magali, Marro Sophie, Besnardeau Lydia, Lepage Thierry
UMR 7009 CNRS, Université Pierre et Marie Curie (Paris 6 Observatoire Océanologique, 06230 Villefranche-sur-mer, France.
Development. 2007 Oct;134(20):3649-64. doi: 10.1242/dev.007799. Epub 2007 Sep 12.
The TGF-beta family member Nodal is essential for specification of the dorsal-ventral axis of the sea urchin embryo, but the molecular factors regulating its expression are not known. Analysis of the nodal promoter is an excellent entry point to identify these factors and to dissect the regulatory logic driving dorsal-ventral axis specification. Using phylogenetic footprinting, we delineated two regulatory regions located in the 5' region of the nodal promoter and in the intron that are required for correct spatial expression and for autoregulation. The 5' regulatory region contains essential binding sites for homeodomain, bZIP, Oct, Tcf/Lef, Sox and Smad transcription factors, and a binding site for an unidentified spatial repressor possibly related to Myb. Soon after its initiation, nodal expression critically requires autoregulation by Nodal and signaling by the maternal TGF-beta Univin. We show that Univin is related to Vg1, that both Nodal and Univin signal through Alk4/5/7, and that zygotic expression of univin, like that of nodal, is dependent on SoxB1 function and Tcf/beta-catenin signaling. This work shows that Tcf, SoxB1 and Univin play essential roles in the regulation of nodal expression in the sea urchin and suggests that some of the regulatory interactions controlling nodal expression predate the chordates. The data are consistent with a model of nodal regulation in which a maternal TGF-beta acts in synergy with maternal transcription factors and with spatial repressors to establish the dorsal-ventral axis of the sea urchin embryo.
转化生长因子-β（TGF-β）家族成员Nodal对于海胆胚胎背腹轴的特化至关重要，但调控其表达的分子因子尚不清楚。分析Nodal启动子是识别这些因子并剖析驱动背腹轴特化的调控逻辑的绝佳切入点。利用系统发育足迹法，我们确定了位于Nodal启动子5'区域和内含子中的两个调控区域，它们对于正确的空间表达和自我调节是必需的。5'调控区域包含同源结构域、碱性亮氨酸拉链（bZIP）、Oct、Tcf/Lef、Sox和Smad转录因子的必需结合位点，以及一个可能与Myb相关的未鉴定空间阻遏物的结合位点。在其起始后不久，Nodal表达关键地需要Nodal的自我调节和母体TGF-β Univin的信号传导。我们表明Univin与Vg1相关，Nodal和Univin都通过Alk4/5/7信号传导，并且Univin的合子表达，与Nodal的表达一样，依赖于SoxB1功能和Tcf/β-连环蛋白信号传导。这项工作表明Tcf、SoxB1和Univin在海胆Nodal表达的调控中发挥重要作用，并表明一些控制Nodal表达的调控相互作用早于脊索动物。这些数据与一个Nodal调控模型一致，其中母体TGF-β与母体转录因子和空间阻遏物协同作用，以建立海胆胚胎的背腹轴。
