Connors Stephanie A, Tucker Jennifer A, Mullins Mary C
Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, 1211 BRBII, 421 Curie Blvd., Philadelphia, PA 19104-6058, USA.
Dev Biol. 2006 May 1;293(1):191-202. doi: 10.1016/j.ydbio.2006.01.029. Epub 2006 Mar 10.
In vertebrates, a bone morphogenetic protein (BMP) signaling pathway patterns all ventral cell fates along the embryonic axis. BMP activity is positively regulated by Tolloid, a metalloprotease, that can eliminate the activity of the BMP antagonist Chordin. A tolloid mutant in zebrafish, mini fin (mfn), exhibits a specific loss of ventral tail tissues. Here, we investigate the spatial and temporal requirements for Tolloid (Mfn) in dorsoventral patterning of the tail. Through chimeric analyses, we found that Tolloid (Mfn) functions cell non-autonomously in the ventral-most vegetal cells of the gastrula or their derivatives. We generated a tolloid transgene under the control of the inducible hsp70 promoter and demonstrate that tolloid (mfn) is first required at the completion of gastrulation. Although tolloid is expressed during gastrulation and dorsally and ventrally within the tail bud, our results indicate that Tolloid (Mfn) acts specifically in the ventral tail bud during a approximately 4 h period extending from the completion of gastrulation to early somitogenesis stages to regulate BMP signaling. Examination of the temporal requirements of Chordin activity by overexpression of the hsp70-tolloid transgene indicates that Chordin is required both during and after gastrulation for proper patterning of the tail, contrasting Tld's requirement only during post-gastrula stages. We hypothesize that the gastrula role of Chordin in tail patterning is to generate the proper size domains of cells to enter the ventral and dorsal tail bud, whereas post-gastrula Chordin activity patterns the derivatives of the tail bud. Thus, fine modulation of BMP signaling levels through the negative and positive actions of Chordin and Tolloid, respectively, patterns tail tissues.
在脊椎动物中，骨形态发生蛋白（BMP）信号通路决定了沿胚胎轴的所有腹侧细胞命运。BMP活性受到金属蛋白酶Tolloid的正向调节，Tolloid可消除BMP拮抗剂Chordin的活性。斑马鱼中的一个Tolloid突变体——小鳍（mfn），表现出腹侧尾部组织的特异性缺失。在这里，我们研究了Tolloid（Mfn）在尾部背腹模式形成中的时空需求。通过嵌合体分析，我们发现Tolloid（Mfn）在原肠胚最腹侧的植物细胞或其衍生物中发挥非细胞自主功能。我们构建了一个在可诱导的hsp70启动子控制下的Tolloid转基因，并证明Tolloid（mfn）在原肠胚形成完成时首次发挥作用。尽管Tolloid在原肠胚形成期间以及尾芽的背侧和腹侧均有表达，但我们的结果表明，Tolloid（Mfn）在从原肠胚形成完成到早期体节形成阶段的大约4小时内，在腹侧尾芽中特异性发挥作用，以调节BMP信号。通过过表达hsp70 - Tolloid转基因来检测Chordin活性的时间需求，结果表明Chordin在原肠胚形成期间和之后对于尾部的正确模式形成都是必需的，这与Tld仅在原肠胚后期阶段发挥作用形成对比。我们推测，Chordin在尾部模式形成中的原肠胚作用是产生适当大小的细胞区域，以进入腹侧和背侧尾芽，而原肠胚后期的Chordin活性则决定了尾芽衍生物的模式。因此，分别通过Chordin和Tolloid的负向和正向作用对BMP信号水平进行精细调节，从而决定了尾部组织的模式。
