Two distinct cell populations in the floor plate of the zebrafish are induced by different pathways.
Two distinct cell populations in the floor plate of the zebrafish are induced by different pathways.
复制标题
DOI：
10.1006/dbio.1999.9589
复制
发表时间：
2000-03
影响因子：
2.7
通讯作者：
J. Odenthal;F. V. Eeden;P. Haffter;P. Ingham;C. Nüsslein-Volhard
中科院分区：
文献类型：
--
作者：
J. Odenthal;F. V. Eeden;P. Haffter;P. Ingham;C. Nüsslein-Volhard
底板是位于脊椎动物腹侧脊髓中线沿着的上皮细胞的形态学上独特的结构。它是引导轴突沿着和穿过神经管中线生长的引导分子的来源。在斑马鱼中，底板约为三个细胞宽，由立方细胞组成。两个细胞群可以通过几个标记基因的表达模式来区分，包括音刺猬（shh）和叉头结构域基因fkd 4：一排同时表达shh和fkd 4的内侧底板（MFP）细胞，两侧是表达fkd 4但不表达shh的外侧底板（LFP）细胞。在斑马鱼胚胎中进行的系统性突变搜索已经确定了一些基因，这些基因的突变明显减少了底板。在这些突变体中，MFP或LFP细胞不存在，如通过分析shh和fkd 4表达模式所揭示的。MFP细胞不存在，但LFP细胞存在，在突变体的剑水蚤，独眼针头，和schmalspur，其中线结构的发展受到影响。LFP细胞不存在，但MFP细胞存在，存在于四个基因的突变体中，即sonic you、you、you-too和chameleon，统称为you型基因。这组突变体还显示了近轴中胚层图案化的缺陷，导致U形体节而不是V形体节。其中一个you-type基因，sonic you，最近被证明编码斑马鱼Shh蛋白，这表明you-type基因编码Shh信号通路的成分。先前已经表明，在斑马鱼中，shh是诱导LFP细胞所必需的，但不是MFP细胞的发育所必需的。这一结论得到以下发现的支持：注射shh RNA导致LFP细胞数量增加，但不导致MFP细胞数量增加。鬣蜥，绕道，和umleitung胚胎突变体共享缺乏LFP细胞与你型突变体，而体节图案没有受到严重影响。在脊索发育失败的突变体中，可能存在MFP细胞，但总是被LFP细胞包围。这些数据表明，在脊索和/或MFP细胞中表达的shh诱导LFP细胞的形成。在独眼巨人（cyc）和音速小子（syu）的胚胎双突变体中，LFP和MFP细胞都被删除。cyc;syu双突变体中初级运动神经元的数量明显减少，而单突变体中基本正常，这表明这两种不同的途径在初级运动神经元的诱导中具有重叠的功能。
The floor plate is a morphologically distinct structure of epithelial cells situated along the midline of the ventral spinal cord in vertebrates. It is a source of guidance molecules directing the growth of axons along and across the midline of the neural tube. In the zebrafish, the floor plate is about three cells wide and composed of cuboidal cells. Two cell populations can be distinguished by the expression patterns of several marker genes, including sonic hedgehog (shh) and the fork head-domain gene fkd4: a single row of medial floor plate (MFP) cells, expressing both shh and fkd4, is flanked by rows of lateral floor plate (LFP) cells that express fkd4 but not shh. Systematic mutant searches in zebrafish embryos have identified a number of genes, mutations in which visibly reduce the floor plate. In these mutants either the MFP or the LFP cells are absent, as revealed by the analysis of the shh and fkd4 expression patterns. MFP cells are absent, but LFP cells are present, in mutants of cyclops, one-eyed pinhead, and schmalspur, whose development of midline structures is affected. LFP cells are absent, but MFP cells are present, in mutants of four genes, sonic you, you, you-too, and chameleon, collectively called the you-type genes. This group of mutants also shows defects in patterning of the paraxial mesoderm, causing U- instead of V-shaped somites. One of the you-type genes, sonic you, was recently shown to encode the zebrafish Shh protein, suggesting that the you-type genes encode components of the Shh signaling pathway. It has been shown previously that in the zebrafish shh is required for the induction of LFP cells, but not for the development of MFP cells. This conclusion is supported by the finding that injection of shh RNA causes an increase in the number of LFP, but not MFP cells. Embryos mutant for iguana, detour, and umleitung share the lack of LFP cells with you-type mutants while somite patterning is not severely affected. In mutants that fail to develop a notochord, MFP cells may be present, but are always surrounded by LFP cells. These data indicate that shh, expressed in the notochord and/or the MFP cells, induces the formation of LFP cells. In embryos doubly mutant for cyclops (cyc) and sonic you (syu) both LFP and MFP cells are deleted. The number of primary motor neurons is strongly reduced in cyc;syu double mutants, while almost normal in single mutants, suggesting that the two different pathways have overlapping functions in the induction of primary motor neurons.