Molecular regulation of neural crest differentiation from embryonic ectoderm

狐狸因子(Winged-Helix转录因子)在早期胚胎模式形成中起着重要作用。我们已经证明，FoxD3(以前的Forkhead 6)是非洲爪哇胚胎神经峰决定的关键调节因子。FoxD3在推测的神经峰区的表达开始于原肠发育晚期，其表达方式与Slug相似，并与Zic-r1重叠。当FoxD3在胚胎和外胚层外植体中过表达时，会诱导神经脊标记的表达。通过显性负性FoxD3结构(FoxD3deIN)减弱FoxD3相关信号可以抑制体内神经脊的分化，而不抑制中枢神经系统标记Sox2。在动物帽子外植体中，由鼻涕虫和Wnt3a诱导的神经脊分化也被FoxD3delN抑制，但不被显性-负性形式的FoxD1抑制。使用显性-负性形式的FoxD3和Slug的功能丧失研究表明：(A)Zic因子诱导的Slug需要FoxD3相关的信号转导；(B)FoxD3和Slug具有不同的下游通路，调节神经峰标志物Ets-1和Twist的表达。这些数据表明，FoxD3在导致神经峰决定的上游调控途径中发挥重要作用。此外，我们最近建立了一种高效的小鼠ES细胞向神经脊分化的体外诱导体系。通过使用这个系统，我们目前正在分析早期神经脊线决定基因之间的详细基因交互作用。

Fox factors (winged-helix transcription factors) play important roles in early embryonic patterning. We have shown that FoxD3 (formerly, Forkhead 6) is a key regulator of neural crest determination in Xenopus embryos. Expression of FoxD3 in the presumptive neural crest region starts at the late gastrula stage in a manner similar to that of Slug, and overlaps with that of Zic-rl. When overexpressed in the embryo and in ectodermal explants, FoxD3 induces expression of neural crest markers. Attenuation of FoxD3-related signaling by a dominant-negative FoxD3 construct (FoxD3deIN) inhibits neural crest differentiation in vivo without suppressing the CNS marker Sox2. In animal cap explants, neural crest differentiation induced by Slug and Wnt3a is also inhibited by FoxD3delN but not by a dominant-negative form of FoxD1. Loss-of-function studies using dominant-negative forms of FoxD3 and Slug indicate(A) Slug induction by Zic factors requires FoxD3-related signaling(B) FoxD3 and Slug have distinct downstream pathways that regulate expression of neural crest markers such as Ets-1 and Twist.These data demonstrate that FoxD3 plays an essential role in the upstream regulatory pathway leading to neural crest determination. In addition, we have recently established an efficiently in vitro induction system for neural crest differentiation from mouse ES cells. By using this system, we are currently analyzing detailed gene interactions between early neural crest determination genes.