Asymmetrically expressed axin required for anterior development in Tribolium
Asymmetrically expressed axin required for anterior development in Tribolium
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DOI：
10.1073/pnas.1116641109
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发表时间：
2012-05-15
影响因子：
11.1
通讯作者：
Bucher, Gregor
中科院分区：
文献类型：
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作者：
Fu, Jinping;Posnien, Nico;Bucher, Gregor
经典的Wnt信号已经牵连在AP轴极化机制，在大多数动物，尽管有限的证据，从节肢动物。在长胚昆虫果蝇中，Wnt信号传导不是全局AP模式所需的，但在短胚昆虫包括赤拟谷盗中，Wnt信号传导的丧失影响生长区中片段的发育，但不影响胚盘中定义的片段的发育。为了确定异位Wnt信号传导的影响，我们分析了轴蛋白的表达和功能，轴蛋白编码该途径的高度保守的负调节因子。我们发现Tc-轴转录本母亲本地化的前极在新鲜产下的鸡蛋。在早期卵裂阶段，表达向后极传播，在胚基形成时变得无处不在。Tc-axin RNAi产生的子代表型范围从轻度受影响的胚胎（具有显示前部结构的分级损失的表皮细胞）到在没有浆膜的情况下在后极凝结的缺陷胚胎。几个胚盘标记物的表达域改变表明后命运的前扩张。其他典型的Wnt途径组件和扩展的Tc-尾表达，Wnt目标的分析表明，Tc-轴蛋白耗尽的影响是通过这一途径介导的，Wnt信号必须被抑制，以适当的前方发展拟谷盗。这些研究提供了独特的证据，典型的Wnt信号必须仔细调节沿着AP轴在节肢动物，并支持祖先的作用，Wnt活性在定义AP极性和后生动物的发展模式。
Canonical Wnt signaling has been implicated in an AP axis polarizing mechanism in most animals, despite limited evidence from arthropods. In the long-germ insect, Drosophila, Wnt signaling is not required for global AP patterning, but in short-germ insects including Tribolium castaneum, loss of Wnt signaling affects development of segments in the growth zone but not those defined in the blastoderm. To determine the effects of ectopic Wnt signaling, we analyzed the expression and function of axin, which encodes a highly conserved negative regulator of the pathway. We found Tc-axin transcripts maternally localized to the anterior pole in freshly laid eggs. Expression spread toward the posterior pole during the early cleavage stages, becoming ubiquitous by the time the germ rudiment formed. Tc-axin RNAi produced progeny phenotypes that ranged from mildly affected embryos with cuticles displaying a graded loss of anterior structures, to defective embryos that condensed at the posterior pole in the absence of serosa. Altered expression domains of several blastodermal markers indicated anterior expansion of posterior fates. Analysis of other canonical Wnt pathway components and the expansion of Tc-caudal expression, a Wnt target, suggest that the effects of Tc-axin depletion are mediated through this pathway and that Wnt signaling must be inhibited for proper anterior development in Tribolium. These studies provide unique evidence that canonical Wnt signaling must be carefully regulated along the AP axis in an arthropod, and support an ancestral role for Wnt activity in defining AP polarity and patterning in metazoan development.