Spiel-ohne-grenzen/pou2 mediates regional competence to respond to Fgf8 during zebrafish early neural development.
Spiel-ohne-grenzen/pou2 mediates regional competence to respond to Fgf8 during zebrafish early neural development.
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发表时间：
2002-02
期刊：
影响因子：
4.6
通讯作者：
Gerlinde Reim;M. Brand
中科院分区：
文献类型：
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作者：
Gerlinde Reim;M. Brand
脊椎动物大脑的神经模式在原肠形成过程中始于外胚层，需要神经外胚层中的组织者细胞群的活动。一个这样的组织者位于预期的中脑-后脑边界(MHB)，通过分泌的信号分子Fgf8控制中脑和前后脑的发育。然而，关于神经前体对Fgf8的反应能力是如何调节的，人们知之甚少。我们研究了斑马鱼spg基因在早期神经发育中的作用。随附的论文中提出的遗传图谱和分子特征表明，spg突变破坏了pou2基因，该基因编码一种在MHB原基中特异表达的POU结构域转录因子，并与哺乳动物Oct3/Oct4同源。我们发现，spg/pou2纯合子胚胎在中脑和后脑原基发育方面存在严重缺陷。在spg突变胚胎中，参与MHB形成的关键分子，如pax2.1、spry4、wnt1、her5、eng2和eng3，以及在后脑发育中起作用的关键分子，如krox20、gbx2、fkd3和pou2都是异常的。相比之下，在MHB建立复杂的调节级联之前，通过OTX2和gbx1的互补表达在神经外胚层对未来MHB的区域性定义在SPG胚胎中是正常的。此外，Fgf8和Wnt1信号通路在MHb被正常激活，但在原肠发育结束时依赖spg。因此，SPG在MHB原基的建立和维持中起着至关重要的作用。移植嵌合体表明，神经外胚层需要正常的spg功能，而内胚层则不需要。重要的是，通过注射Fgf8和Pou2或Fgf8珠体的获得功能实验以及对spg-ace双突变体的分析表明，spg胚胎对Fgf8不敏感，尽管下游MAPK信号通路的Fgf8受体表达和活性似乎完好无损。我们认为Spg/POU2是一种转录因子，调节区域对Fgf8信号的反应能力。
Neural patterning of the vertebrate brain starts within the ectoderm during gastrulation and requires the activity of organizer cell populations in the neurectoderm. One such organizer is located at the prospective midbrain-hindbrain boundary (MHB) and controls development of the midbrain and the anterior hindbrain via the secreted signaling molecule Fgf8. However, little is known about how the ability of neural precursors to respond to Fgf8 is regulated. We have studied the function of the zebrafish spiel-ohne-grenzen (spg) gene in early neural development. Genetic mapping and molecular characterization presented in the accompanying paper revealed that spg mutations disrupt the pou2 gene, which encodes a POU domain transcription factor that is specifically expressed in the MHB primordium, and is orthologous to mammalian Oct3/Oct4. We show that embryos homozygous for spg/pou2 have severe defects in development of the midbrain and hindbrain primordium. Key molecules that function in the formation of the MHB, such as pax2.1, spry4, wnt1, her5, eng2 and eng3, and in hindbrain development, such as krox20, gbx2, fkd3 and pou2, are all abnormal in spg mutant embryos. By contrast, regional definition of the future MHB in the neuroectoderm by complementary expression of otx2 and gbx1, before the establishment of the complex regulatory cascade at the MHB, is normal in spg embryos. Moreover, the Fgf8 and Wnt1 signaling pathways are activated normally at the MHB but become dependent on spg towards the end of gastrulation. Therefore, spg plays a crucial role both in establishing and in maintaining development of the MHB primordium. Transplantation chimeras show that normal spg function is required within the neuroectoderm but not the endomesoderm. Importantly, gain-of-function experiments by mRNA injection of fgf8 and pou2 or Fgf8 bead implantations, as well as analysis of spg-ace double mutants show that spg embryos are insensitive to Fgf8, although Fgf receptor expression and activity of the downstream MAP kinase signaling pathway appear intact. We suggest that spg/pou2 is a transcription factor that mediates regional competence to respond to Fgf8 signaling.