ORGANIZER AND EMBRYONIC REGULATION

Hensen‘s结节，羊膜上相当于两栖动物“Spemann’s” 组织者“，是最重要的区域，很早，原肠形成 胚胎。它不仅产生了身体的中线器官 (神经管的脊索、体节、肠道、底板)，但也是 负责诱导和形成整个中枢神经的模式 系统。经典研究声称，基于形态标准， 当Hensen‘s结节被切除时，脊索和体节正常形成。 这个项目包括对这个问题的新的调查，采取 利用目前可用的许多分子标记来揭示 将胚胎的这一独特区域指定为“ 组织者“，并将其细胞与原始条纹的其余部分分开。 这项研究将有助于在分子和分子水平上确定组织者 胚胎学术语，并确定导致 该区域中几个基因的表达调控。最后， 结果将显示管理器的哪些属性位于 在胚胎发育的非常早期阶段独立控制。 利用移植实验结合原位杂交和 逆转录病毒载体导致特定基因的错误表达，如下 具体问题将被解决：脊索和体节是否形成 在结节消融后？原始条纹的树桩是否表示节点- 结节消融后的特异性标记物(如鹅卵石、声波刺猬)？ 结节消融后，原始条纹的残端会不会 神经诱导能力和/或在大脑中诱导额外手指的能力 寄主肢芽？重新生成的节点是否左/右不对称(如 正常节点)？重新生成节点属性的能力是否仅限于 原始条纹的特定部分？如果上述任何属性 不能被原始条纹获取，它能被再生吗？ 这些特性是否被用来表达适当的节点标记基因？

Hensen's node, the amniote equivalent of the amphibian "Spemann's organizer", is the most important region of the very early, gastrulating embryo. Not only does it generate the midline organs of the body (notochord, somites, gut, floor plate of the neural tube), but is also responsible for inducing and patterning the whole of the central nervous system. Classical studies have claimed, based on morphological criteria, that when Hensen's node is ablated, notochord and somites form normally. This project consists of new investigation of this problem, taking advantage of the many molecular markers now available, to reveal the conditions that specify this unique region of the embryo as "the organizer" and set its cells aside from the rest of the primitive streak. The study will help to define the organizer in both molecular and embryological terms and to identify the conditions that lead to the regulation of expression of several genes in this region. Finally, the results will reveal which properties of the organizer are under independent control at very early stages of embryonic development. Using transplantation experiments combined with in situ hybridization and retroviral vectors to cause misexpression of specific genes, the following specific questions will be addressed: Do the notochord and somites form after node ablation? Does the stump of the primitive streak express node- specific markers (e.g. goosecoid, sonic hedgehog) after node ablation? After ablation of the node, can the stump of the primitive streak acquire neural inducing ability and/or the ability to induce extra digits in a host limb bud? Is the regenerated node left/right asymmetric (like the normal node)? Is the ability to regenerate node properties restricted to a specific portion of the primitive streak? If any of the above properties cannot be acquired by the primitive streak, can it be made to regenerate these properties if made to express appropriate node marker genes?