The Wnt Pathway and Inductive Competence in Early Xenopus Development

0110893威尔逊细胞群之间的诱导信号控制着胚胎发育的大部分过程。 这些相互作用的一个中心特征是改变能力：细胞对特定信号配体的反应以复杂和精确调节的方式演变。 拟议研究的长期目标是了解能力的分子基础，使用早期非洲爪蟾发育中对Wnt信号的变化反应作为模型。 在非洲爪蟾发育的最初几个小时，Wnt信号通路的激活驱动背轴的形成;仅仅几个小时后，这种反应就消失了，该通路转而在中胚层和神经模式中发挥作用。 本项目的目的是了解为什么一个重要的靶基因siamois被早期而不是晚期Wnt信号激活，并将Wnt通路的能力与更广泛的胚胎学反应，背轴形成联系起来。使用简单的启动子-报告基因测定，将分析siamois启动子以鉴定在后期阶段Wnt响应性丧失中重要的序列元件。 然后将使用siamois的可诱导活化和抑制形式来检查siamois本身诱导背轴的能力，从而将该基因的调节与轴诱导能力联系起来。 这两个目标都将利用一种新开发的工具来诱导刺激Wnt反应，该工具由地塞米松诱导的激活形式的XTCF 3组成，XTCF 3是一种DNA结合蛋白，已知可介导对Wnt信号的转录反应。 这一工作将有助于阐明诱导能力的机制，这是发育生物学中一个重要而长期存在的问题。

0110893WilsonInductive signals between cell populations govern much of embryonic development. A central feature of these interactions is changing competence: the response of cells to particular signaling ligands evolves in a complex and precisely regulated manner. The long-term goal of the proposed research is to understand the molecular basis of competence, using changing responses to Wnt signaling in early Xenopus development as a model. In the first hours of Xenopus development, activation of the Wnt signaling pathway drives formation of the dorsal axis; only a few hours later, this response is lost, and the pathway instead functions in mesodermal and neural patterning. The objectives of the current project are to understand why an important target gene, siamois, is activated by early but not by late Wnt signaling, and to tie competence of the Wnt pathway to induce this gene to the broader embryological response, dorsal axis formation. Using a simple promoter-reporter assay, the siamois promoter will be analyzed to identify sequence elements important in the loss of Wnt responsiveness at later stages. Competence of siamois itself to induce a dorsal axis will then be examined using inducible activated and inhibitory versions of siamois, thus linking the regulation of this gene to axis induction competence. Both aims will make use of a newly developed tool for inducible stimulation of Wnt responses, consisting of a dexamethasone-inducible, activated form of XTCF3, a DNA-binding protein known to mediate transcriptional responses to Wnt signaling. This work will contribute to elucidating the mechanism of inductive competence, an important and long-standing problem in developmental biology.