Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF.
Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF.
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发表时间：
1999-07
期刊：
影响因子：
4.6
通讯作者：
A. Rodaway;H. Takeda;S. Koshida;J. Broadbent;B. Price;James C. Smith;R. Patient;N. Holder
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文献类型：
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作者：
A. Rodaway;H. Takeda;S. Koshida;J. Broadbent;B. Price;James C. Smith;R. Patient;N. Holder
内胚层形成肠道和相关器官，并由脊椎动物胚胎原肠胚阶段出现的一层细胞发育而来。与中胚层和外胚层相比，我们对诱导内胚层的信号知之甚少。内胚层的起源与中胚层的起源密切相关，既通过它们在胚胎中的位置，也通过可以诱导它们的分子。我们对斑马鱼 gata5 基因进行了表征，该基因在囊胚阶段的内胚层中表达，并表明其转录是由来自卵黄细胞的信号诱导的。这些信号还诱导中胚层表达的无尾转录因子 (ntl)，其初始表达与最靠近胚盘边缘的细胞中的 gata5 一致，然后扩散到胚环。我们已经表征了这些基因的诱导，并表明激活素的异位表达以模仿内源表达的模式诱导gata5和ntl，而显性失活激活素受体的表达消除了ntl和gata5表达。注射编码组成型活性激活素受体的RNA会导致gata5和ntl的异位表达。 gata5是细胞自主激活的，而ntl是在远离接受RNA的细胞中诱导的，这表明虽然这两个基因的表达都是由TGF-β信号诱导的，但ntl的表达随后通过中继机制传播。成纤维细胞生长因子（eFGF）或显性负作用FGF受体的表达表明，ntl而非gata5受FGF信号调节，这意味着这可能是导致ntl表达扩散的中继信号。在同时缺乏斜视和独眼巨人（TGF-β相关分子节点组成员）的胚胎中，胚盘中的gata5表达被消除，使得这些因子成为诱导gata5的内源性TGF-β信号的主要候选因子。
The endoderm forms the gut and associated organs, and develops from a layer of cells which emerges during gastrula stages in the vertebrate embryo. In comparison to mesoderm and ectoderm, little is known about the signals which induce the endoderm. The origin of the endoderm is intimately linked with that of mesoderm, both by their position in the embryo, and by the molecules that can induce them. We characterised a gene, zebrafish gata5, which is expressed in the endoderm from blastula stages and show that its transcription is induced by signals originating from the yolk cell. These signals also induce the mesoderm-expressed transcription factor no tail (ntl), whose initial expression coincides with gata5 in the cells closest to the blastoderm margin, then spreads to encompass the germ ring. We have characterised the induction of these genes and show that ectopic expression of activin induces gata5 and ntl in a pattern which mimics the endogenous expression, while expression of a dominant negative activin receptor abolishes ntl and gata5 expression. Injection of RNA encoding a constitutively active activin receptor leads to ectopic expression of gata5 and ntl. gata5 is activated cell-autonomously, whereas ntl is induced in cells distant from those which have received the RNA, showing that although expression of both genes is induced by a TGF-beta signal, expression of ntl then spreads by a relay mechanism. Expression of a fibroblast growth factor (eFGF) or a dominant negatively acting FGF receptor shows that ntl but not gata5 is regulated by FGF signalling, implying that this may be the relay signal leading to the spread of ntl expression. In embryos lacking both squint and cyclops, members of the nodal group of TGF-beta related molecules, gata5 expression in the blastoderm is abolished, making these factors primary candidates for the endogenous TGF-beta signal inducing gata5.