Tight regulation of SpSoxB factors is required for patterning and morphogenesis in sea urchin embryos
Tight regulation of SpSoxB factors is required for patterning and morphogenesis in sea urchin embryos
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DOI：
10.1016/s0012-1606(03)00331-2
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发表时间：
2003-09-15
影响因子：
2.7
通讯作者：
Angerer, LM
中科院分区：
文献类型：
--
作者：
Kenny, AP;Oleksyn, DW;Angerer, LM
先前在海胆胚胎中的研究已经证明，β-连环蛋白的核化对于来自植物卵裂球的内胚层和间充质的规格的初始步骤是必不可少的。这个过程开始于第4个分裂阶段，并延伸到第9个分裂阶段，在此期间，SpSoxB 1转录调节因子被包括转录阻遏物SpKr 1在内的β-连环蛋白依赖性基因产物下调。这些观察结果提出了一种可能性，即SpSoxB 1的去除是允许植物发育进行所必需的。在这里，我们表明，升高和异位表达的这个因素抑制分化的所有植物细胞类型，表型是非常相似的抑制β-连环蛋白核功能的钙粘蛋白过表达所造成的。植物命运的抑制涉及蛋白质-蛋白质水平的干扰，因为阻止其与DNA结合的SpSoxB 1突变不会显著降低这种活性。SpSoxB 1水平的降低导致体内荧光素酶报告基因的TCF/Lef-beta-catenin依赖性表达升高，表明在正常胚胎中，这种蛋白质抑制了间充质和内胚层特化所需的主要植物信号传导机制。令人惊讶的是，SpSoxB 1的正常表达是原肠胚形成和内胚层分化所必需的，如吗啉介导的翻译干扰和显性负性蛋白的表达所示。一个密切相关的因子SpSoxB 2的类似的功能获得和功能丧失试验表明，它也是原肠胚形成所需的，并且它的过度表达可以抑制植物发育。然而，显着的表型差异是明显的，在两个扰动，表明SpSoxB 1和SpSoxB 2至少有一些不同的发育功能。所有这些研究的结果支持一个模型，其中SpSoxB因子的浓度必须沿着早期海胆胚胎的动物-植物轴进行严格调节，以允许内胚层和间充质细胞命运的β-连环蛋白依赖性规范以及激活原肠胚形成所需的靶基因。(C)2003年爱思唯尔公司All rights reserved.
Previous studies in sea urchin embryos have demonstrated that nuclearization of beta-catenin is essential for initial steps in the specification of endoderm and mesenchyme, which are derived from vegetal blastomeres. This process begins at the 4th and extends through the 9th cleavage stage, an interval in which the SpSoxB1 transcription regulator is downregulated by beta-catenin-dependent gene products that include the transcription repressor SpKrl. These observations raise the possibility that SpSoxB1 removal is required to allow vegetal development to proceed. Here we show that elevated and ectopic expression of this factor suppresses differentiation of all vegetal cell types, a phenotype that is very similar to that caused by the suppression of beta-catenin nuclear function by cadherin overexpression. Suppression of vegetal fates involves interference at the protein-protein level because a mutation of SpSoxB1 that prevents its binding to DNA does not significantly reduce this activity. Reduction in SpSoxB1 level results in elevated TCF/Lef-beta-catenin-dependent expression of a luciferase reporter gene in vivo, indicating that in the normal embryo this protein suppresses the primary vegetal signaling mechanism that is required for specification of mesenchyme and endoderm. Surprisingly, normal expression of SpSoxB1 is required for gastrulation and endoderm differentiation, as shown by both morpholino-mediated translational interference and expression of a dominant negative protein. Similar gain-of-function and loss-of-function assays of a closely related factor, SpSoxB2, demonstrate that it, too, is required for gastrulation and that its overexpression can suppress vegetal development. However, significant phenotypic differences are apparent in the two perturbations, indicating that SpSoxB1 and SpSoxB2 have at least some distinct developmental functions. The results of all these studies support a model in which the concentration of SpSoxB factors must be tightly regulated along the animal-vegetal axis of the early sea urchin embryo to allow beta-catenin-dependent specification of endoderm and mesenchyme cell fates as well as to activate target genes required for gastrulation. (C) 2003 Elsevier Inc. All rights reserved.