Saulnier Didier M E, Ghanbari Hedyeh, Brändli André W
Department of Applied Biosciences, Swiss Federal Institute of Technology (ETHZ), CH-8057 Zürich, Switzerland.
Dev Biol. 2002 Aug 1;248(1):13-28. doi: 10.1006/dbio.2002.0712.
In the vertebrate embryo, development of the excretory system is characterized by the successive formation of three distinct kidneys: the pronephros, mesonephros, and metanephros. While tubulogenesis in the metanephric kidney is critically dependent on the signaling molecule Wnt-4, it is unknown whether Wnt signaling is equally required for the formation of renal epithelia in the other embryonic kidney forms. We therefore investigated the expression of Wnt genes during the pronephric kidney development in Xenopus. Wnt4 was found to be associated with developing pronephric tubules, but was absent from the pronephric duct. Onset of pronephric Wnt-4 expression coincided with mesenchyme-to-epithelium transformation. To investigate Wnt-4 gene function, we performed gain- and loss-of-function experiments. Misexpression of Wnt4 in the intermediate and lateral mesoderm caused abnormal morphogenesis of the pronephric tubules, but was not sufficient to initiate ectopic tubule formation. We used a morpholino antisense oligonucleotide-based gene knockdown strategy to disrupt Wnt-4 gene function. Xenopus embryos injected with antisense Wnt-4 morpholinos developed normally, but marker gene and morphological analysis revealed a complete absence of pronephric tubules. Pronephric duct development was largely unaffected, indicating that ductogenesis may occur normally in the absence of pronephric tubules. Our results show that, as in the metanephric kidney, Wnt-4 is critically required for tubulogenesis in the pronephric kidney, indicating that a common, evolutionary conserved gene regulatory network may control tubulogenesis in different vertebrate excretory organs.
在脊椎动物胚胎中，排泄系统的发育特征是依次形成三种不同的肾脏：前肾、中肾和后肾。虽然后肾中的肾小管形成严重依赖于信号分子Wnt-4，但尚不清楚Wnt信号对于其他胚胎肾脏形式中肾上皮的形成是否同样必需。因此，我们研究了非洲爪蟾前肾发育过程中Wnt基因的表达情况。发现Wnt4与发育中的前肾小管相关，但在前肾管中不存在。前肾Wnt-4表达的开始与间充质到上皮的转变同时发生。为了研究Wnt-4基因的功能，我们进行了功能获得和功能丧失实验。在中胚层中部和外侧中误表达Wnt4会导致前肾小管形态发生异常，但不足以启动异位肾小管的形成。我们使用基于吗啉代反义寡核苷酸的基因敲低策略来破坏Wnt-4基因的功能。注射反义Wnt-4吗啉代的非洲爪蟾胚胎正常发育，但标记基因和形态学分析显示完全没有前肾小管。前肾管的发育基本未受影响，这表明在没有前肾小管的情况下，管道形成可能正常发生。我们的结果表明，与后肾一样，Wnt-4对于前肾中的肾小管形成至关重要，这表明一个共同的、进化保守的基因调控网络可能控制不同脊椎动物排泄器官中的肾小管形成。
