Kiecker C, Niehrs C
Division of Molecular Embryology, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Development. 2001 Nov;128(21):4189-201. doi: 10.1242/dev.128.21.4189.
Anteroposterior (AP) patterning of the vertebrate neural plate is initiated during gastrulation and is regulated by Spemann's organizer and its derivatives. The prevailing model for AP patterning predicts a caudally increasing gradient of a 'transformer' which posteriorizes anteriorly specified neural cells. However, the molecular identity of the transforming gradient has remained elusive. We show that in Xenopus embryos (1) dose-dependent Wnt signalling is both necessary and sufficient for AP patterning of the neuraxis, (2) Wnt/beta-catenin signalling occurs in a direct and long-range fashion within the ectoderm, and (3) that there is an endogenous AP gradient of Wnt/beta-catenin signalling in the presumptive neural plate of the Xenopus gastrula. Our results indicate that an activity gradient of Wnt/beta-catenin signalling acts as transforming morphogen to pattern the Xenopus central nervous system.
脊椎动物神经板的前后模式在原肠胚形成期间启动，并受施佩曼组织者及其衍生物的调控。前后模式形成的主流模型预测，一种“转化因子”的梯度在尾部逐渐增加，该梯度使前部指定的神经细胞向尾部化。然而，转化梯度的分子身份一直难以捉摸。我们发现，在非洲爪蟾胚胎中：（1）剂量依赖性Wnt信号对于神经轴的前后模式形成既是必需的也是充分的；（2）Wnt/β-连环蛋白信号以直接且长距离的方式在外胚层内发生；（3）在非洲爪蟾原肠胚的假定神经板中存在Wnt/β-连环蛋白信号的内源性前后梯度。我们的结果表明，Wnt/β-连环蛋白信号的活性梯度作为转化形态发生素，为非洲爪蟾中枢神经系统构建模式。
