A set of novel tadpole specific genes expressed only in the epidermis are down-regulated by thyroid hormone during Xenopus laevis metamorphosis
A set of novel tadpole specific genes expressed only in the epidermis are down-regulated by thyroid hormone during Xenopus laevis metamorphosis
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DOI：
10.1006/dbio.1996.8478
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发表时间：
1997-02-15
影响因子：
2.7
通讯作者：
Brown, DD
中科院分区：
文献类型：
--
作者：
Furlow, JD;Berry, DL;Brown, DD
筛选了甲状腺激素诱导的非洲爪蟾蝌蚪尾基因表达下调的4个基因。这四种基因编码的细胞外糖蛋白只在整个蝌蚪表皮的顶端细胞层表达，这相当于哺乳动物胎儿的外周皮。这四种新基因在胚胎发育后期开始表达，在蝌蚪的整个生命中都有活性，在外源添加的甲状腺激素中受到抑制，在蝌蚪生命末期自然停止表达，这些过程是密切协调的。这些事实表明，这些基因的蛋白质产物在蝌蚪表皮中形成了一种新的（尽管是暂时的）屏障或其他结构，其功能取代了成年表皮的角状、分层上皮。我们已经利用这些基因的克隆作为细胞特异性标记来跟踪顶端细胞在发育过程中的出现和丢失。我们能够直接证明，在真正表皮形成的开始阶段，顶端细胞来源于胚胎外胚层的分层。顶端细胞均匀地覆盖在蝌蚪的表面，直到蜕变，这时四个表皮特异性基因的表达在整个蝌蚪上协调地丧失。相反，成体表皮的发育具有明显的区域特异性：成体角蛋白首先表达至体表皮和尾表皮的一条线，最后仅在变质高潮时出现在尾部。最后，我们的分析表明，th诱导的变态过程中的基因表达下调程序与先前描述的涉及多种细胞类型和几波基因表达变化的上调程序非常不同。下调的程序只包括在幼虫细胞中表达的少数基因的抑制，这些基因在幼虫到成虫的蜕变过程中被预编程为死亡。(C) 1997学术出版社。
Four genes were identified in a screen for thyroid hormone-induced down-regulation of gene expression in Xenopus laevis tadpole tails. All four encode extracellular glycoproteins that are expressed exclusively in the apical cell layer of the entire tadpole epidermis, which is the equivalent of the mammalian fetal periderm. The onset of the four novel genes' expression late in embryogenesis, their activity throughout the life of the tadpole, their repression by exogenously added thyroid hormone, and the spontaneous cessation of their expression at the end of tadpole life are closely coordinated. These facts suggest that the protein products of these genes form a novel albeit temporary barrier or other structure in the tadpole epidermis that functions in lieu of the cornified, stratified epithelium of the adult epidermis. We have exploited the cloning of these genes for use as cell-specific markers to follow the appearance and loss of apical cells during development. We were able to demonstrate directly that the apical cells are derived from a stratification of the embryonic ectoderm at the onset of the formation of a true epidermis. The apical cells uniformly cover the surface of the tadpole until metamorphosis, when the expression of the four larval epidermis-specific genes is lost coordinately over the entire tadpole. In contrast, the adult epidermis develops with a distinct regional specificity: adult keratin is first expressed up to a line separating the body and tail epidermis and finally appears in the tail only at metamorphic climax. Finally, our analysis reveals that the TH-induced down-regulated gene expression program during metamorphosis is very different from the previously described up-regulated program which involves multiple cell types and several waves of gene expression changes. The down-regulated program only consists of the repression of a small number of genes which are expressed in larval cells preprogrammed to die during the larval to adult transition at metamorphosis. (C) 1997 Academic Press.