LaBonne C, Bronner-Fraser M
Division of Biology, Beckman Institute 139-74, California Institute of Technology, Pasadena, CA 91125, USA.
Development. 1998 Jul;125(13):2403-14. doi: 10.1242/dev.125.13.2403.
We have investigated the molecular interactions underlying neural crest formation in Xenopus. Using chordin overexpression to antagonize endogenous BMP signaling in whole embryos and explants, we demonstrate that such inhibition alone is insufficient to account for neural crest induction in vivo. We find, however, that chordin-induced neural plate tissue can be induced to adopt neural crest fates by members of the FGF and Wnt families, growth factors that have previously been shown to posteriorize induced neural tissue. Overexpression of a dominant negative XWnt-8 inhibits the expression of neural crest markers, demonstrating the necessity for a Wnt signal during neural crest induction in vivo. The requirement for Wnt signaling during neural crest induction is shown to be direct, whereas FGF-mediated neural crest induction may be mediated by Wnt signals. Overexpression of the zinc finger transcription factor Slug, one of the earliest markers of neural crest formation, is insufficient for neural crest induction. Slug-expressing ectoderm will generate neural crest in the presence of Wnt or FGF-like signals, however, bypassing the need for BMP inhibition in this process. A two-step model for neural crest induction is proposed.
我们研究了非洲爪蟾神经嵴形成的分子相互作用。通过在全胚胎和外植体中过表达脊索蛋白以拮抗内源性骨形态发生蛋白（BMP）信号，我们证明仅这种抑制不足以解释体内神经嵴的诱导。然而，我们发现，通过成纤维细胞生长因子（FGF）家族和Wnt家族的成员，可诱导脊索蛋白诱导的神经板组织获得神经嵴命运，这些生长因子先前已被证明可使诱导的神经组织向后方化。显性负性XWnt-8的过表达抑制了神经嵴标志物的表达，证明了体内神经嵴诱导过程中Wnt信号的必要性。结果表明，神经嵴诱导过程中对Wnt信号的需求是直接的，而FGF介导的神经嵴诱导可能由Wnt信号介导。锌指转录因子Slug是神经嵴形成最早的标志物之一，其过表达不足以诱导神经嵴。然而，在存在Wnt或FGF样信号的情况下，表达Slug的外胚层将产生神经嵴，在此过程中绕过了对BMP抑制的需求。我们提出了一个神经嵴诱导的两步模型。
