Riddle R D, Johnson R L, Laufer E, Tabin C
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Cell. 1993 Dec 31;75(7):1401-16. doi: 10.1016/0092-8674(93)90626-2.
The zone of polarizing activity (ZPA) is a region at the posterior margin of the limb bud that induces mirror-image duplications when grafted to the anterior of a second limb. We have isolated a vertebrate gene, Sonic hedgehog, related to the Drosophila segment polarity gene hedgehog, which is expressed specifically in the ZPA and in other regions of the embryo, that is capable of polarizing limbs in grafting experiments. Retinoic acid, which can convert anterior limb bud tissue into tissue with polarizing activity, concomitantly induces Sonic hedgehog expression in the anterior limb bud. Implanting cells that express Sonic hedgehog into anterior limb buds is sufficient to cause ZPA-like limb duplications. Like the ZPA, Sonic hedgehog expression leads to the activation of Hox genes. Sonic hedgehog thus appears to function as the signal for antero-posterior patterning in the limb.
极化活性区（ZPA）是肢体芽后部边缘的一个区域，当移植到第二个肢体的前部时会诱导镜像重复。我们分离出了一个脊椎动物基因——音猬因子（Sonic hedgehog），它与果蝇体节极性基因刺猬因子（hedgehog）相关，在ZPA和胚胎的其他区域特异性表达，并且在移植实验中能够使肢体极化。视黄酸可将前肢芽组织转化为具有极化活性的组织，同时在前肢芽中诱导音猬因子的表达。将表达音猬因子的细胞植入前肢芽足以导致类似ZPA的肢体重复。与ZPA一样，音猬因子的表达会导致Hox基因的激活。因此，音猬因子似乎充当了肢体前后模式形成的信号。
