Leclerc Catherine, Webb Sarah E, Miller Andrew L, Moreau Marc
Centre de Biologie du Développement, UMR 5547 and GDR 2688, Université Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse, Cedex 04, France.
Dev Biol. 2008 Sep 15;321(2):357-67. doi: 10.1016/j.ydbio.2008.06.029. Epub 2008 Jul 2.
The pronephros is the first kidney to develop and is the functional embryonic kidney in lower vertebrates. It has previously been shown that pronephric tubules can be induced to form ex vivo in ectodermal tissue by treatment with activin A and retinoic acid. In this study, we investigated the role of Ca(2+) signaling in the formation of the pronephric tubules both in intact Xenopus embryos and ex vivo. In the ex vivo system, retinoic acid but not activin A stimulated the generation of Ca(2+) transients during tubule formation. Furthermore, tubule differentiation could be induced by agents that increase the concentration of intracellular Ca(2+) in activin A-treated ectoderm. In addition, tubule formation was inhibited by loading the ectodermal tissue with the Ca(2+) chelator, BAPTA-AM prior to activin A/retinoic acid treatment. In intact embryos, Ca(2+) transients were also recorded during tubule formation, and photo-activation of the caged Ca(2+) chelator, diazo-2, localized to the pronephric domain, produced embryos with a shortened and widened tubule phenotype. In addition, the location of the Ca(2+) transients observed, correlated with the expression pattern of the specific pronephric tubule gene, XSMP-30. These data indicate that Ca(2+) might be a necessary signal in the process of tubulogenesis both ex vivo and in intact embryos.
前肾是最早发育的肾脏，也是低等脊椎动物胚胎期起功能作用的肾脏。此前已有研究表明，通过激活素A和视黄酸处理，可在体外诱导外胚层组织形成前肾小管。在本研究中，我们研究了钙离子信号在非洲爪蟾完整胚胎及体外前肾小管形成过程中的作用。在体外系统中，视黄酸而非激活素A在肾小管形成过程中刺激了钙离子瞬变的产生。此外，增加激活素A处理的外胚层细胞内钙离子浓度的试剂可诱导肾小管分化。另外，在激活素A/视黄酸处理前，用钙离子螯合剂BAPTA-AM处理外胚层组织可抑制肾小管形成。在完整胚胎中，肾小管形成过程中也记录到了钙离子瞬变，对定位于前肾区域的笼锁钙离子螯合剂重氮-2进行光激活，可产生肾小管表型缩短变宽的胚胎。此外，观察到的钙离子瞬变位置与特定前肾小管基因XSMP-30的表达模式相关。这些数据表明，钙离子可能是体外及完整胚胎肾小管发生过程中的必要信号。
