Molecular regulation of neural crest differentiation from embryonic ectoderm

Fox因子（翼螺旋转录因子）在早期胚胎形成中起重要作用。我们已经表明，FoxD 3（以前，叉头6）是非洲爪蟾胚胎神经嵴决定的关键调节因子。FoxD 3在假定的神经嵴区域中的表达以与Slug类似的方式在原肠胚晚期开始，并且与Zic-rl的表达重叠。当在胚胎和外胚层外植体中过表达时，FoxD 3诱导神经嵴标志物的表达。显性负性FoxD 3构建体（FoxD 3deIN）减弱FoxD 3相关信号传导抑制体内神经嵴分化，而不抑制CNS标记物Sox 2。在动物帽外植体中，由Slug和Wnt 3a诱导的神经嵴分化也被FoxD 3delN抑制，但不被显性负性形式的FoxD 1抑制。使用显性阴性形式的FoxD 3和Slug的功能丧失研究表明（A）通过Zic因子的Slug诱导需要FoxD 3相关的信号传导（B）FoxD 3和Slug具有调节神经嵴标记物（例如Ets-1和Twist）表达的不同下游途径。此外，我们最近建立了一个有效的体外诱导系统，从小鼠ES细胞神经嵴分化。通过使用这个系统，我们目前正在分析早期神经嵴决定基因之间的详细基因相互作用。

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.