Department of Molecular and Cell Biology and Center for Integrative Genomics, University of California, Berkeley, CA 94720-3200, USA.
Dev Biol. 2010 Jan 15;337(2):335-50. doi: 10.1016/j.ydbio.2009.11.008. Epub 2009 Nov 10.
In ectodermal explants from Xenopus embryos, inhibition of BMP signaling is sufficient for neural induction, leading to the idea that neural fate is the default state in the ectoderm. Many of these experiments assayed the action of BMP antagonists on animal caps, which are relatively naïve explants of prospective ectoderm, and different results have led to debate regarding both the mechanism of neural induction and the appropriateness of animal caps as an assay system. Here we address whether BMP antagonists are only able to induce neural fates in pre-patterned explants, and the extent to which neural induction requires FGF signaling. We suggest that some discrepancies in conclusion depend on the interpretations of sox gene expression, which we show not only marks definitive neural tissue, but also tissue that is not yet committed to neural fates. Part of the early sox2 domain requires FGF signaling, but in the absence of organizer signaling, this domain reverts to epidermal fates. We also reinforce the evidence that ectodermal explants are naïve, and that explants that lack any dorsal prepattern are readily neuralized by BMP antagonists, even when FGF signaling is inhibited.
在非洲爪蟾胚胎的外胚层外植体中，抑制 BMP 信号足以诱导神经发生，这使得神经命运成为外胚层中的默认状态。许多此类实验检测了 BMP 拮抗剂在动物帽上的作用，动物帽是相对原始的外胚层外植体，不同的结果导致了关于神经诱导机制和动物帽作为一种测定系统的适当性的争论。在这里，我们研究了 BMP 拮抗剂是否仅能够在外胚层预成型的外植体中诱导神经命运，以及神经诱导需要 FGF 信号的程度。我们认为，结论中的一些差异取决于 sox 基因表达的解释，我们表明 sox 基因不仅标记明确的神经组织，而且还标记尚未确定为神经命运的组织。早期 sox2 结构域的一部分需要 FGF 信号，但在没有组织者信号的情况下，该结构域会恢复为表皮命运。我们还加强了外胚层外植体是原始的，并且缺乏任何背侧预成型的外植体很容易被 BMP 拮抗剂神经化的证据，即使 FGF 信号被抑制。
