A binding site for Gli proteins is essential for HNF-3beta floor plate enhancer activity in transgenics and can respond to Shh in vitro.
A binding site for Gli proteins is essential for HNF-3beta floor plate enhancer activity in transgenics and can respond to Shh in vitro.
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发表时间：
1997-04
期刊：
影响因子：
4.6
通讯作者：
H. Sasaki;C. Hui;M. Nakafuku;H. Kondoh
中科院分区：
文献类型：
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作者：
H. Sasaki;C. Hui;M. Nakafuku;H. Kondoh
底板在脊椎动物胚胎神经管的腹侧图案形成和轴突引导中起重要作用。底板发育的一个关键事件是诱导翅螺旋转录因子，肝细胞核因子-3 β（HNF-3 β）。HNF-3 β底板表达增强子位于转录单位的3'端，由多个元件组成。HNF-3 β的诱导依赖于脊索来源的信号，Sonic hedgehog（Shh）。在果蝇中的遗传分析已经导致参与Hh信号通路的基因的鉴定，并且编码具有五个锌指基序的蛋白质的cubitus interruptus（ci）被置于下游。在目前的工作中，我们测试参与Gli蛋白，小鼠同源的Ci，在激活的地板增强子HNF-3 β。转基因分析表明，Gli结合位点是体内HNF-3 β最小底板增强子活性所必需的。三个Gli基因在发育中的神经管中差异表达。Gli表达仅限于腹侧部分，而Gli 2和Gli 3分别在整个神经管和背侧表达。强Gli和Gli 2以及弱Gli 3表达在其诱导时与HNF-3 β短暂重叠。与腹侧定位表达一致，Gli表达可以在细胞系中被Shh上调。最后，Gli结合位点充当Shh响应元件，并且人GLI（而不是GLI 3）可以在组织培养中激活该结合位点。综上所述，这些发现表明，Gli，也可能是Gli 2，是很好的候选人的转录激活因子的HNF-3 β底板增强子，Gli蛋白的结合位点是一个关键因素，为响应Shh信号。这些结果也支持Gli/Ci是Hedgehog信号通路中进化保守的转录因子的观点。
The floor plate plays important roles in ventral pattern formation and axonal guidance within the neural tube of vertebrate embryos. A critical event for floor plate development is the induction of a winged helix transcription factor, Hepatocyte Nuclear Factor-3beta (HNF-3beta). The enhancer for floor plate expression of HNF-3beta is located 3' of the transcription unit and consists of multiple elements. HNF-3beta induction depends on the notochord-derived signal, Sonic hedgehog (Shh). Genetic analysis in Drosophila has led to the identification of genes involved in the Hh signalling pathway, and cubitus interruptus (ci), encoding a protein with five zinc finger motifs, was placed downstream. In the present work, we test the involvement of Gli proteins, the mouse homologues of Ci, in activation of the floor plate enhancer of HNF-3beta. Transgenic analysis shows that a Gli-binding site is required for the activity of the minimal floor plate enhancer of HNF-3beta in vivo. Three Gli genes are differentially expressed in the developing neural tube. Gli expression is restricted to the ventral part, while Gli2 and Gli3 are expressed throughout the neural tube and dorsally, respectively. Strong Gli and Gli2, and weak Gli3 expressions transiently overlap with HNF-3beta at the time of its induction. Consistent with ventrally localized expression, Gli expression can be up-regulated by Shh in a cell line. Finally, the Gli-binding site acts as a Shh responsive element, and human GLI, but not GLI3, can activate this binding site in tissue culture. Taken together, these findings suggest that Gli, and probably also Gli2, are good candidates for transcriptional activators of the HNF-3beta floor plate enhancer, and the binding site for Gli proteins is a key element for response to Shh signalling. These results also support the idea that Gli/Ci are evolutionary conserved transcription factors in the Hedgehog signalling pathway.