DETERMINATION OF EMBRYONIC POLARITY

在胚胎发育的早期阶段， 胚轴起始于胚胎的一极。的大部分地区都 关于这一过程背后的分子机制的已知是基于 在两栖动物胚胎中，母体衍生的决定因素控制着这一点， 极性 在鸟类和哺乳动物中，这是不可能的，因为 胚胎在更晚的阶段可以启动轴的形成， 位置 在这里，决定胚胎极性的机制， 将使用鸡胚研究发育的早期阶段， 一个模型，因为他们易于操作和文化。 首先，下胚层的作用（曾被认为是 负责极性确定）将直接进行测试。然后， 与两栖动物“Nieuwkoop中心”同源的区域（该中心具有 在青蛙中展示，以确定未来“组织者”的位置， 轴向细胞）将被定位。 最后，一些已经发现的基因 来预测胚胎未来的极性 将按照等级顺序排列，利用这一事实， 部分胚胎将启动轴的形成时， 胚胎的其余部分。 该项目的结果将有助于建议如何 早期发展中的分子级联 低等脊椎动物（鱼类、两栖动物）可应用于高等 脊椎动物（鸟类和哺乳动物）。 潜在地，这些知识 级联可能导致新的分子诊断工具的发展 许多严重的先天性疾病， 胚胎轴的发展，并可能有助于确定是否 同卵双生和连体双生可能有分子基础。

During the early stages on embryonic development, the formation of the embryonic axis is initiated at one pole of the embryo. Most of what is known about the molecular mechanisms underlying this process is based on amphibian embryos, where maternally-derived determinants control this polarity. In amniotes (birds and mammals) this is unlikely because embryos at much later stages can initiate axis formation at any position. Here, the mechanisms that determine embryonic polarity in the early stages of development will be studied using the chick embryo as a model, because of their ease of manipulation and culture. First, the role of the hypoblast (which had been suggested to be responsible for polarity determination) will be tested directly. Then, the region homologous to the amphibian "Nieuwkoop center" (which has been shown in frogs to determine the position of future "organizer" and axial cells) will be located. Finally, a number of genes already found to be expressed in a way that predicts the future polarity of the embryo will be placed in hierarchial order, taking advantage of the fact that portions of the embryo will initiate axis formation when isolated from the rest of the embryo. The results of this project will be of value in suggesting how the molecular cascades that have been implicated in the early development of lower vertebrates (fish, amphibians) can be applied to higher vertebrates (birds and mammals). Potentially, knowledge of these cascades could lead to the development of new molecular diagnostic tools for some of the many serious congenital disorders that affect the early development of the embryonic axis, and may help determine whether monozygotic and conjoined twinning are likely to have a molecular basis.