Dorsal-Ventral Polarity in the Drosophila Embryo

果蝇模式形成的一个关键步骤是 沿着两个主要身体轴沿着建立极性。至少 20个母性活跃的基因参与创造背- 腹极性各种实验表明， 背侧代表过程中的最后一步，它充当 腹侧形态基元将母体位置信息与 合子基因组斯图尔特博士克隆并鉴定了 dorsal基因，并发现它与脊椎动物密切相关 原癌基因c-rel在野生型胚胎中， 卵裂时存在于细胞质中。在原子核之后 迁移到胚胎的外围，从腹侧到背侧 建立核背蛋白梯度。形成 核梯度的破坏在突变胚胎从其他 母系活跃的背腹极性基因。背侧的 突变体胚胎中，仅观察到细胞质蛋白，而 腹侧化的胚胎，核梯度向背侧移动。 背侧蛋白质从细胞质重新定位到 背核似乎是作为形态发生素发挥作用的关键。 斯图尔特博士提出了一些实验，解决 问题是什么基因与背侧相互作用， 细胞质相对于细胞核的定位，或者对于 一旦蛋白质进入细胞核，它就能发挥背侧功能。具体 她将进行基因筛选， 特定背侧突变的抑制子。

A critical step in pattern formation in Drosophila is the establishment of polarity along the two major body axes. At least 20 maternally active genes are involved in creating dorsal- ventral polarity. A variety of experiments have shown that dorsal represents the last step in the process, it acts as the ventral morphogen relating the maternal positional information to the zygotic genome. Dr. Steward has cloned and characterized the dorsal gene and found it is closely related to the vertebrate proto-oncogene c-rel. In wild type embryos, the dorsal protein is present in the cytoplasm during cleavage. After the nuclei migrate to the periphery of the embryo, a ventral to dorsal gradient of nuclear dorsal protein is established. The formation of the nuclear gradient is disrupted in mutant embryos from other maternally active dorsal-ventral polarity genes. In dorsalized mutant embryos, only cytoplasmic protein is observed, while in ventralized embryos, the nuclear gradient is shifted dorsally. Relocalization of the dorsal protein from the cytoplasm to the nucleus appears critical for dorsal to function as a morphogen. Dr. Steward proposes a number of experiments that address the question of what genes either interact with dorsal to effect the cytoplasmic versus nuclear localization or are essential for dorsal function once the protein is in the nucleus. Specifically she will perform genetic screens to isolate second site suppressors of specific dorsal mutations.