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Organizing signal and the tectal and cerebellar differentiation

组织信号以及顶盖和小脑的分化

基本信息

批准号：
13480243
负责人：
NAKAMURA Harukazu
金额：
$ 9.66万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13480243/
关键词：
mesencephaon metencephalon organizer Fgf8 Ras-ERK signaling pathway cerebellar differentiation Fgf8a Fgf8b Otx2 Glx2 Irx2 視蓋小脳

项目摘要

The isthmus works as an organizer, and Fgf8 mimics the organizing activity. The isthmic organizer plays a role for the development of the tectum and the cerebellum in the mesencephalon and in the metencephalon, respectively. It is very interesting that completely different architecture of the tectum and the cerebellum differentiates under a common signal. We paid attention to that among 8 isoforms of Fgf8, Fgf8a and Fgf8b are expressed in the isthmus, and carried out misexpression of Fgf8a and Fgf8b by in ovo electroporation. Fgf8a induced the tectum in the diencephalon as expected. It was surprising that Fgf8b changed the fate of the mesencephalic alar plate to the cerebellum. Fgf8b repressed Otx2 expression in the mesencephalon, but induced expression of Gbx2 and Irx2, which are normally expressed in the metencephalon. The quantitative study revealed that the difference between Fgf8a and Fgf8b could be attributed to the difference in the intensity of the signal. It was suggested that strong signal of Fgf8 turns the gene expression cascade toward the cerebellar differentiation.We were then interested in Ras-ERK pathway as the signal transduction pathway downstream of the Fgf8 signal. In normal embryos ERK is activated at the site where Fgf8 mRNA is localized. Fgf8b activated ERK while Fgf8a or lower dose of Fgf8b did not activate ERK in the mes/metencephalon. Disruption of the Ras-ERK signaling pathway by dominant negative form of Ras (Ras^<S17N>) changed the fate or the metencephalic alar plate from cerebellum to tectum. Ras^<S17N> canceled the effects of Fgf8b, while co-transfection of Fgf8a and Ras^<S17N> exerted additive effects. The results indicate that the presumptive metencephalon receives strong Fgf8 signal that activates the Ras-ERK pathway and differentiates into the cerebellum.

峡部起组织者的作用，而Fgf8模仿组织活动。峡部组织者在中脑和后脑分别对顶盖和小脑的发育起作用。非常有趣的是，在一个共同的信号下，顶盖和小脑的完全不同的结构区分开来。我们注意到在8种Fgf8亚型中，Fgf8a和Fgf8b在峡部表达，并通过体内电穿孔实现了Fgf8a和Fgf8b的错误表达。FGF8a不出所料地诱导了间脑的顶盖。令人惊讶的是，Fgf8b将中脑翼板的命运改变到了小脑。Fgf8b抑制了OTX2在中脑的表达，但诱导了在中脑正常表达的Gbx2和Irx2的表达。定量研究表明，Fgf8a和Fgf8b之间的差异可能归因于信号强度的不同。这表明Fgf8的强信号使基因表达级联向小脑分化，因此我们对Ras-ERK通路作为Fgf8信号下游的信号转导途径感兴趣。在正常胚胎中，ERK在Fgf8基因的定位部位被激活。Fgf8b激活MES/后脑ERK，而Fgf8a或低剂量Fgf8b不激活ERK。显性负性RAS(Ras^&lt；S17N&gt；)阻断Ras-ERK信号通路改变了后脑翼板从小脑到顶盖的命运。Ras^lt；S17N&gt；取消了Fgf8b的作用，而Fgf8a与Ras^lt；S17N&gt；共转染则表现为相加效应。结果表明，推测的后脑接收到强烈的Fgf8信号，激活Ras-ERK通路并分化为小脑。