Marchak Alexander, Grant Paaqua A, Neilson Karen M, Datta Majumdar Himani, Yaklichkin Sergey, Johnson Diana, Moody Sally A
Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington DC, USA.
Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington DC, USA; Department of Biological Sciences, George Washington University, Washington DC, USA.
Dev Biol. 2017 Sep 1;429(1):213-224. doi: 10.1016/j.ydbio.2017.06.025. Epub 2017 Jun 27.
In many animals, maternally synthesized mRNAs are critical for primary germ layer formation. In Xenopus, several maternal mRNAs are enriched in the animal blastomere progenitors of the embryonic ectoderm. We previously identified one of these, WW-domain binding protein 2 N-terminal like (wbp2nl), that others previously characterized as a sperm protein (PAWP) that promotes meiotic resumption. Herein we demonstrate that it has an additional developmental role in regionalizing the embryonic ectoderm. Knock-down of Wbp2nl in the dorsal ectoderm reduced cranial placode and neural crest gene expression domains and expanded neural plate domains; knock-down in ventral ectoderm reduced epidermal gene expression. Conversely, increasing levels of Wbp2nl in the neural plate induced ectopic epidermal and neural crest gene expression and repressed many neural plate and cranial placode genes. The effects in the neural plate appear to be mediated, at least in part, by down-regulating chd, a BMP antagonist. Because the cellular function of Wbp2nl is not known, we mutated several predicted motifs. Expressing mutated proteins in embryos showed that a putative phosphorylation site at Thr45 and an α-helix in the PH-G domain are required to ectopically induce epidermal and neural crest genes in the neural plate. An intact YAP-binding motif also is required for ectopic epidermal gene expression as well as for down-regulating chd. This work reveals novel developmental roles for a cytoplasmic protein that promotes epidermal and neural crest formation at the expense of neural ectoderm.
在许多动物中，母源合成的mRNA对于初级胚层的形成至关重要。在非洲爪蟾中，几种母源mRNA在胚胎外胚层的动物卵裂球祖细胞中富集。我们之前鉴定出其中一种，即WW结构域结合蛋白2 N端样蛋白（wbp2nl），其他人之前将其表征为一种促进减数分裂恢复的精子蛋白（PAWP）。在此我们证明它在胚胎外胚层区域化中具有额外的发育作用。在背侧外胚层中敲低Wbp2nl会降低颅基板和神经嵴基因表达域，并扩大神经板域；在腹侧外胚层中敲低会降低表皮基因表达。相反，在神经板中增加Wbp2nl的水平会诱导异位的表皮和神经嵴基因表达，并抑制许多神经板和颅基板基因。在神经板中的这些作用似乎至少部分是通过下调BMP拮抗剂chd来介导的。由于Wbp2nl的细胞功能尚不清楚，我们对几个预测的基序进行了突变。在胚胎中表达突变蛋白表明，Thr45处的一个假定磷酸化位点和PH-G结构域中的一个α螺旋是在神经板中异位诱导表皮和神经嵴基因所必需的。一个完整的YAP结合基序对于异位表皮基因表达以及下调chd也是必需的。这项工作揭示了一种细胞质蛋白的新的发育作用，该蛋白以神经外胚层为代价促进表皮和神经嵴的形成。
