ANTEROPOSTERIOR ECTODERMAL PATTERNING IN XENOPUS

描述(申请人提供)：这个项目的长期目标是了解非洲爪蛙推测的中性外胚层(背部外胚层)的确定和模式形成的分子机制。这项提议的目的是通过探索标记基因的表达如何限制在假定的新皮层上，来询问新皮层是如何首先被搁置的。在一个用于定义神经模式的非常早期标记的消减克隆筛选中，Sive实验室分离出了OPL，它编码zic基因家族的一种锌指蛋白。在原肠形成过程中，OPL在整个假定的中胚层都有表达。在外胚层外植体中，骨形态发生蛋白(BMP)拮抗剂Noggin和Wnt3a可以激活OPL的表达。我们将把分泌因子Noggin和Wnt3a的活性与OPL表达的激活联系起来。尽管BMP拮抗剂与非洲爪哇的神经决定密切相关，但去除BMP激活下游基因的机制尚不清楚。同样，Wnt蛋白与后脑神经构型和一般神经决定有关，但它们激活神经直肠胚层靶基因的机制可能很复杂。OPL启动子对Noggin和Wnt3a的反应区域已经在外植体中定义。这些序列将被进一步分析，并与将OPL表达限制在转基因胚胎神经板上所需的序列进行比较。将确定一个与诺金反应元件相互作用的因子(S)。将定义OPI启动子中的系统发育保守元件。许多出生缺陷会影响神经管，但其遗传原因通常还不清楚。这一建议将界定正常的发育机制，从而洞察异常发育的原因。信号转导通路改变神经直肠胚层靶基因表达的机制尚不清楚，对信号分子的异常反应在包括癌症在内的多种疾病中发挥作用。该建议将有助于定义引发对信令事件的异常响应的机制。

DESCRIPTION (provided by applicant): The long-term goals of this project are to understand the molecular mechanisms responsible for determination and patterning of the presumptive neurectoderm (dorsal ectoderm) of the frog Xenopus laevis. The goals of this proposal are to ask how the neurectoderm is first set aside, by exploring how expression of a marker gene is restricted to the presumptive neurectoderm. In a subtractive cloning screen to define very early markers of neural pattern, the Sive lab isolated opl, which encodes a zinc finger protein, a member of the zic gene family. Opl is expressed throughout the presumptive neurectoderm during gastrulation. In ectodermal explants, opl expression can be activated by the Bone Morphogenetic Protein (BMP) antagonist Noggin and by Wnt3a. We will connect the activities of the secreted factors Noggin and Wnt3a with activation of opl expression. Although BMP antagonists have been strongly implicated in neural determination in Xenopus, the mechanism by which removal of BMPs activates downstream genes is not understood. Similarly, Wnt proteins are implicated in posterior neural patterning and general neural determination, but the mechanism by which they activate neurectodermal target genes may be complex. Regions of the opl promoter responsive to Noggin and to Wnt3a have been defined in explants. These sequences will be further analyzed and compared to those required to restrict opl expression to the neural plate of transgenic embryos. A factor(s), which interacts with the Noggin-responsive element will be identified. Phylogenetically conserved elements in the opI promoter will be defined. Many birth defects affect the neural tube, however their genetic cause is generally not understood. This proposal will define normal developmental mechanisms and therefore give insight into causes of abnormal development. The mechanisms through which signal transduction pathways change expression of neurectodermal target genes is poorly understood, and abnormal responses to signaling molecules play a role in multiple diseases, including cancers. This proposal will help define mechanisms by which abnormal response to a signaling event is elicited.