Cooperative activity of multiple upper layer proteins for thalamocortical axon growth
Cooperative activity of multiple upper layer proteins for thalamocortical axon growth
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DOI：
10.1002/dneu.20592
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发表时间：
2008-02-15
影响因子：
3
通讯作者：
Yamamoto, Nobuhiko
中科院分区：
文献类型：
--
作者：
Maruyama, Takuro;Matsuura, Masahiro;Yamamoto, Nobuhiko
在发育过程中，感觉丘脑皮层（TC）轴突生长为新皮层，并主要在第4层终止。为了研究层特异性TC轴突终止的分子机制，我们研究了TC轴突对发育中的皮层上层表达的ephrin-A5、Sema7A和kit配体（KL）的响应性。从胚胎大鼠脑中分离的丘脑背侧细胞在培养皿中培养，培养皿中涂有这些分子的预簇fc标记的细胞外结构域。每种蛋白均以钟形曲线的剂量依赖性方式促进TIC轴突生长。这三种蛋白的任何组合在低浓度下都表现出协同效应，而在高浓度下则不表现出协同效应，这表明它们的促生长活性是通过共同的途径起作用的。在过滤膜上进一步测试了这些蛋白质空间分布的影响，使用一种新的蛋白质打印技术，即简单制备微孔蛋白质打印（STAMP2）方法，将这些蛋白质打印成与体内层流厚度相同的尺寸。结果表明，TC轴突在层粘连蛋白包被区域大量生长，但无法侵入邻近的ephrin- a5打印区域，这表明TC轴突在这些区域之间的生长效果存在相对差异。此外，KL和Sema7A的存在增强了ephrin-A5的抑制作用。综上所述，这些结果表明，层特异性TC轴突靶向机制涉及上层多个分子的生长抑制活性以及上层和深层之间分子环境的检测。(C) 2007 Wiley期刊公司
During development, sensory thalamocortical (TC) axons grow into the neocortex and terminate primarily in layer 4. To study the molecular mechanism that underlies lamina-specific TC axon termination, we investigated the responsiveness of TC axons to ephrin-A5, semaphorin-7A (Sema7A) and kit ligand (KL), which are expressed in the upper layers of the developing cortex. Dissociated cells of the dorsal thalamus from embryonic rat brain were cultured on dishes that were coated with preclustered Fc-tagged extracellular domains of these molecules. Each protein was found to promote TIC axon growth in a dose-dependent fashion of a bell-shaped curve. Any combination of the three proteins showed a cooperative effect in lower concentrations but not in higher concentrations, suggesting that their growth-promoting activities act in a common pathway. The effect of spatial distributions of these proteins was further tested on a filter membrane, in which these proteins were printed at a size that recapitulates the scale of laminar thickness in vivo, using a novel protein-printing technique, Simple-To-mAke Micropore Protein-Printing (STAMP2) method. The results demonstrated that TC axons grew massively on the laminin-coated region but were prevented from invading the adjacent ephrin-A5-printed region, suggesting that TC axons detect relative differences in the growth effect between these regions. Moreover, the inhibitory action of ephrin-A5 was enhanced by copresence with KL and Sema7A. Together, these results suggest that the lamina-specific TC axon targeting mechanism involves growth-inhibitory activity by multiple molecules in the upper layers and detection in the molecular environments between the upper and deep layers. (C) 2007 Wiley Periodicals, Inc.