Crucial roles of Robo proteins in midline crossing of cerebellofugal axons and lack of their up-regulation after midline crossing.
Crucial roles of Robo proteins in midline crossing of cerebellofugal axons and lack of their up-regulation after midline crossing.
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DOI：
10.1186/1749-8104-3-29
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发表时间：
2008-11-05
影响因子：
3.6
通讯作者：
Murakami F
中科院分区：
文献类型：
--
作者：
Tamada A;Kumada T;Zhu Y;Matsumoto T;Hatanaka Y;Muguruma K;Chen Z;Tanabe Y;Torigoe M;Yamauchi K;Oyama H;Nishida K;Murakami F
Robo1、Robo2 和 Rig-1 (Robo3) 是 Robo 蛋白家族的成员，是化学防护剂 Slit 的候选受体，已知在脊髓连合轴突引导中发挥关键作用。然而，它们在其他轴向水平上的作用仍然未知。在这里，我们检查了后脑头侧小脑 (CF) 连合轴突的 Robo 蛋白表达，并通过分析 Robo 基因敲除小鼠来研究它们在 CF 轴突寻路中的作用。我们分析了啮齿动物胚胎中小脑深部神经元 CF 轴突的 Robo 蛋白表达，重点关注中线交叉和交叉后导航的发育阶段。在CF轴突中线交叉阶段，Robo1和Robo2的mRNA在小脑核过渡区表达，该区是小脑深部核原基所在的位置，支持CF轴突表达Robo1和Robo2的观点。事实上，通过电穿孔标记小脑深部核神经元的 CF 轴突的免疫组织化学分析表明，Robo1 蛋白（可能还有 Robo2 蛋白）由穿过中线的 CF 轴突表达。然而，在 CF 轴突的纵向部分发现这些蛋白质的表达较弱或没有表达。在 Robo1/2 双敲除小鼠中，许多 CF 轴突到达中线但未能退出。我们发现 CF 轴突在到达中线之前表达 Rig-1 (Robo3)，但在纵向旋转之后不表达。与体内观察一致，从小脑外植体与底板外植体共培养中引出的轴突表达 Rig-1。在 Rig-1 缺陷小鼠胚胎中，CF 轴突似乎向同侧突出，但未到达中线。这些结果表明 Robo1、Robo2 或两者都是 CF 轴突中线出口所必需的。相比之下，他们需要 Rig-1 才能接近中线。然而，这些蛋白质的交叉后上调在脊柱连合轴突引导中起重要作用，但中线交叉后 CF 轴突的纵向导航似乎不需要这些蛋白质。我们的结果表明，尽管在不同轴向水平上的中线穿越有共同的机制，但穿越后导航存在显着差异。
Robo1, Robo2 and Rig-1 (Robo3), members of the Robo protein family, are candidate receptors for the chemorepellents Slit and are known to play a crucial role in commissural axon guidance in the spinal cord. However, their roles at other axial levels remain unknown. Here we examine expression of Robo proteins by cerebellofugal (CF) commissural axons in the rostral hindbrain and investigate their roles in CF axon pathfinding by analysing Robo knockout mice. We analysed the expression of Robo proteins by CF axons originating from deep cerebellar neurons in rodent embryos, focusing on developmental stages of their midline crossing and post-crossing navigation. At the stage of CF axon midline crossing, mRNAs of Robo1 and Robo2 are expressed in the nuclear transitory zone of the cerebellum, where the primordium of the deep cerebellar nuclei are located, supporting the notion that CF axons express Robo1 and Robo2. Indeed, immunohistochemical analysis of CF axons labelled by electroporation to deep cerebellar nuclei neurons indicates that Robo1 protein, and possibly also Robo2 protein, is expressed by CF axons crossing the midline. However, weak or no expression of these proteins is found on the longitudinal portion of CF axons. In Robo1/2 double knockout mice, many CF axons reach the midline but fail to exit it. We find that CF axons express Rig-1 (Robo3) before they reach the midline but not after the longitudinal turn. Consistent with this in vivo observation, axons elicited from a cerebellar explant in co-culture with a floor plate explant express Rig-1. In Rig-1 deficient mouse embryos, CF axons appear to project ipsilaterally without reaching the midline. These results indicate that Robo1, Robo2 or both are required for midline exit of CF axons. In contrast, Rig-1 is required for their approach to the midline. However, post-crossing up-regulation of these proteins, which plays an important role in spinal commissural axon guidance, does not appear to be required for the longitudinal navigation of CF axons after midline crossing. Our results illustrate that although common mechanisms operate for midline crossing at different axial levels, significant variation exists in post-crossing navigation.
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影响因子：
64.5
作者：
Brose, K;Bland, KS;Kidd, T
通讯作者：
Kidd, T
影响因子：
4.6
作者：
Andrews, William;Liapi, Anastasia;Richards, Linda J.
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Richards, Linda J.
影响因子：
16.2
作者：
Kidd, T;Russell, C;Tear, G
通讯作者：
Tear, G
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3.6
作者：
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通讯作者：
Shirasaki, R
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作者：
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