The Xenopus homologue of Bicaudal-C is a localized maternal mRNA that can induce endoderm formation.
The Xenopus homologue of Bicaudal-C is a localized maternal mRNA that can induce endoderm formation.
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发表时间：
2000-05
期刊：
影响因子：
4.6
通讯作者：
O. Wessely;E. Robertis
中科院分区：
文献类型：
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作者：
O. Wessely;E. Robertis
在非洲爪哇，合子转录在受精后6小时的中期囊胚期开始，因此胚胎发育的第一步受到母体遗传蛋白和mRNAs的调控。虽然动植物两极在卵母细胞中已经存在，但背腹轴只有在受精时才能通过精子进入和随后的卵皮质旋转来建立。在筛选其稳定性受大脑皮层旋转调节的母体mRNAs时，我们分离了果蝇基因Bicaudal-C(xBic-C)的非洲爪哇同源物。它编码一个假定的RNA结合分子，在母体中表达，并主要定位于鸡蛋的植物部分。在受精和皮质旋转时，xBic-C mRNA与沉重的卵黄一起移位到未来胚胎的背侧。在紫外线腹壁的胚胎中，xBic-C的多腺化程度低于未经处理的皮质旋转的胚胎。通过在整个胚胎或外胚层组织中注射合成的mRNA过表达xBic-C会导致异位内胚层的形成。这种诱导内胚层的活性依赖于蛋白质的RNA结合域的存在。与已知的另外两个母系编码的内胚层诱导剂Vg1和Vegt不同，xBic-C的异位表达在没有中胚层诱导的情况下特异性地导致内胚层的形成。
In Xenopus, zygotic transcription starts 6 hours after fertilization at the midblastula transition and therefore the first steps in embryonic development are regulated by maternally inherited proteins and mRNAs. While animal-vegetal polarity is already present in the oocyte, the dorsoventral axis is only established upon fertilization by the entry of the sperm and the subsequent rotation of the egg cortex. In a screen for maternal mRNAs whose stability is regulated by this cortical rotation, we isolated the Xenopus homologue of the Drosophila gene Bicaudal-C (xBic-C). It encodes a putative RNA-binding molecule expressed maternally and localized predominantly to the vegetal half of the egg. Upon fertilization and cortical rotation, xBic-C mRNA is displaced together with the heavy yolk towards the future dorsal side of the embryo. In UV-ventralized embryos, xBic-C is polyadenylated less than in untreated embryos that undergo cortical rotation. Overexpression of xBic-C by injection of synthetic mRNA in whole embryos or in ectodermal explants leads to ectopic endoderm formation. This endoderm-inducing activity is dependent on the presence of the RNA-binding domain of the protein. In contrast to the two other known maternally encoded endoderm inducers, Vg1 and VegT, xBic-C ectopic expression leads specifically to endoderm formation in the absence of mesoderm induction.