Yuasa S
Laboratory of Neural Information, National Institute for Physiological Sciences, Okazaki, Japan.
Arch Histol Cytol. 2001 May;64(2):149-58. doi: 10.1679/aohc.64.149.
Tenascin-C (TN-C) is an astroglia-derived extracellular matrix protein that has been shown to be an early marker for astroglial precursors in the embryonic mouse brain. This study examined astroglial generation, migration, and differentiation in the developing mouse hippocampus by in situ hybridization histochemistry for TN-C mRNA. Special reference was given to the difference in the mode of astroglial development between the two cortical structures of the hippocampus: the dentate gyrus and Ammon's horn. TN-C-positive cells were found in the ventricular germinative zone of the hippocampus as early as the 15th gestational day, and the labeled cells in the zone apposed to the fimbria migrated tangentially through the subpial area towards the forming dentate gyrus. The TN-C-positive cells aligned in the dentate gyrus exhibited the characteristic morphology of unipolar astrocytes as revealed by double labeling with glial fibrillary acidic protein (GFAP)-immunohistochemistry. On the other hand, the TN-C-positive cells ranging over a wide area of the ventricular germinative zone facing the forming Ammon's horn migrated radially towards the cortex, with most of them aligned in the Ammon's horn exhibiting a GFAP-positive stellate morphology. The onset of migration towards the dentate gyrus was two days earlier than that towards the Ammon's horn. TN-C-positive cells in both cortical structures exhibited a DNA-replicating activity after settlement in the early postnatal stage and were considered to further generate astrocytes. On the other hand, TN-C-positive cells with DNA-replicating activity were also found in the subpial migratory stream moving towards the dentate gyrus and were considered to form the subpial matrix for the generation of the dentate astrocytes. Migratory TN-C-positive cells directed towards both the dentate gyrus and Ammon's horn were apposed to radial glial processes and were believed to be guided by contact with these processes in a manner similar to migratory immature neurons. These findings indicate that TN-C-positive cells for the dentate gyrus and those for the Ammon's horn have different migratory patterns and undergo different morphological differentiations depending on their site of origin at the early stage of astrogliogenesis and corresponding to the different modes of neurogenesis in the two cortical structures.
腱生蛋白-C（TN-C）是一种由星形胶质细胞衍生的细胞外基质蛋白，已被证明是胚胎小鼠大脑中星形胶质前体细胞的早期标志物。本研究通过对TN-C mRNA进行原位杂交组织化学，研究了发育中小鼠海马体中星形胶质细胞的生成、迁移和分化。特别关注了海马体两个皮质结构——齿状回和海马角——之间星形胶质细胞发育模式的差异。早在妊娠第15天，就在海马体的室生发区发现了TN-C阳性细胞，与海马伞相邻区域的标记细胞通过软膜下区域向形成中的齿状回进行切向迁移。用胶质纤维酸性蛋白（GFAP）免疫组织化学双重标记显示，在齿状回中排列的TN-C阳性细胞呈现出单极星形胶质细胞的特征形态。另一方面，在面向形成中的海马角的室生发区广泛区域中的TN-C阳性细胞向皮质进行径向迁移，其中大多数在海马角中排列呈现出GFAP阳性的星形形态。向齿状回迁移的开始时间比向海马角迁移早两天。出生后早期定居后，两个皮质结构中的TN-C阳性细胞均表现出DNA复制活性，并被认为可进一步生成星形胶质细胞。另一方面，在向齿状回移动的软膜下迁移流中也发现了具有DNA复制活性的TN-C阳性细胞，并被认为形成了用于生成齿状星形胶质细胞的软膜下基质。朝向齿状回和海马角的迁移性TN-C阳性细胞与放射状胶质细胞突起相邻，并被认为以类似于迁移性未成熟神经元的方式通过与这些突起的接触而受到引导。这些发现表明，齿状回的TN-C阳性细胞和海马角的TN-C阳性细胞具有不同的迁移模式，并根据它们在星形胶质细胞生成早期的起源部位以及对应于两个皮质结构中不同的神经发生模式，经历不同的形态分化。
