Beck C W, Whitman M, Slack J M
Developmental Biology Programme, Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.
Dev Biol. 2001 Oct 15;238(2):303-14. doi: 10.1006/dbio.2001.0407.
Tail bud formation in Xenopus depends on interaction between a dorsal domain (dorsal roof) expressing lunatic fringe and Notch, and a ventral domain (posterior wall) expressing the Notch ligand Delta. Ectopic expression of an activated form of Notch, Notch ICD, by means of an animal cap graft into the posterior neural plate, results in the formation of an ectopic tail-like structure containing a neural tube and fin. However, somites are never formed in these tails. Here, we show that BMP signaling is activated in the posterior wall of the tail bud and is involved in the formation of tail somites from this region. Grafts into the posterior neural plate, in which BMP signaling is activated, will form tail-like outgrowths. Unlike the Notch ICD tails, the BMP tails contain well-organized somites as well as neural tube and fin, with the graft contributing to both somites and neural tube. Through a variety of epistasis-type experiments, we show that the most likely model involves a requirement for BMP signaling upstream of Notch activation, resulting in formation of the secondary neural tube, as well as a Notch-independent pathway leading to the formation of tail somites from the posterior wall.
非洲爪蟾的尾芽形成依赖于表达 lunatic fringe 和 Notch 的背侧区域（背顶）与表达 Notch 配体 Delta 的腹侧区域（后壁）之间的相互作用。通过将动物帽移植到后神经板中异位表达活化形式的 Notch（Notch ICD），会导致形成包含神经管和鳍的异位尾状结构。然而，这些尾巴中从未形成体节。在此，我们表明 BMP 信号在尾芽的后壁中被激活，并参与该区域尾体节的形成。移植到 BMP 信号被激活的后神经板中会形成尾状突出物。与 Notch ICD 尾巴不同，BMP 尾巴包含组织良好的体节以及神经管和鳍，移植组织对体节和神经管都有贡献。通过各种上位性实验，我们表明最可能的模型涉及在 Notch 激活上游需要 BMP 信号，从而导致次级神经管的形成，以及一条不依赖 Notch 的途径，该途径导致从后壁形成尾体节。
