GENETIC ANALYSIS OF POLARITY

果蝇图案形成的一个关键步骤是 沿两个主体轴的两极的建立。至少20个 母体活跃的基因参与了背腹两极的形成。 各种实验表明，背部是最后一步。 在这个过程中，它扮演着连接母体的腹侧形态因子的角色 合子基因组的位置信息。我们已经克隆了 描述了背部基因的特征，发现它与 脊椎动物原癌基因c-rel。在野生型胚胎中，背部 在卵裂过程中，蛋白质存在于细胞质中。在原子核之后 迁移到胚胎的外围，腹侧到背侧的梯度 建立了核背部蛋白。原子核的形成 来自其他母系活跃的突变胚胎的梯度被打乱 背腹两极基因。在背部突变的胚胎中，只有 细胞质蛋白被观察到，而在腹壁胚胎中， 核梯度向后移位。背部再定位 从细胞质到细胞核的蛋白质似乎对背部到 起到形态生成剂的作用。 我们提出了一些实验来解决这两个基本问题 问题：(1)核梯度是如何形成的，有哪些因素 (2)背侧是如何发挥形态原功能的。

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. We have 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. We propose a number of experiments that address the two basic questions of (1) how is the nuclear gradient formed and what factors are involved, and (2) how does dorsal exert its function as a morphogen.