Mechanisms of the development of neuronal cell society in the central nervous system

在发育中的大脑皮层中，大多数出生在脑室附近的神经元作为多极迁移神经元在室下区（SVZ）积累，然后在进入皮质板（CP）之前转化为运动神经元。当运动细胞到达边缘区（MZ）以下的层时，我们观察到它们发生了各种戏剧性的形态变化，并终止了迁移。例如，它们开始形成顶端原始树突，并在MZ下方积聚，这表明它们可能开始与邻近细胞形成新的细胞间关系，从而形成适当的层状结构。此外，运动神经元在CP径向胶质纤维的引导下，一旦其前导过程到达枕状表面，最终会发生染色体易位（“末端易位”）。为了了解调节这些事件的机制，我们在本研究中采用了几种方法。首先，我们筛选了在胚胎皮质壁每个区域的细胞中特异性表达的基因：心室区（VZ）、SVZ或MZ以下的细胞。因此，我们确定了大约4000个在VZ中优先表达的基因，其中659个基因是分泌或跨膜分子。在SVZ区和MZ区以下的细胞中，我们分别发现在每个区有大约20个和40个基因优先表达。我们在这项研究中分析了其中一些基因的生物学功能。阐明这些分子的迁移阶段依赖性基因表达谱的调控机制是今后研究的重要内容。

In the developing cerebral cortex, most neurons that are born near the ventricle accumulate in the subventricular zone (SVZ) as multipolar migrating neurons and are then transformed to locomoting neurons prior to entering the cortical plate (CP). When the locomoting cells reach the layer beneath the marginal zone (MZ), we observed that they undergo various dramatic morphological changes, in addition to the termination of migration. For example, they begin to develop apical primitive dendrites and accumulate beneath the MZ, suggesting that they probably start to form new intercellular relationships with adjacent cells and thereby develop an appropriate layer structure. Furthermore, locomoting neurons guided by radial glial fibers in the CP ultimately undergo somal translocation once their leading processes reach the pial surface ("terminal translocation"). To understand the mechanisms that regulate these events, we took several approaches in this study. Firstly, we screened for genes that are specifically expressed in cells in each zone of the embryonic cortical wall: ventricular zone (VZ), SVZ, or cells beneath the MZ. Consequently, we identified approximately 4, 000 genes that are preferentially expressed in the VZ, among which 659 genes are secretory or transmembrane molecules. As for the SVZ and the cells beneath the MZ, we found about 20 genes and 40 genes expressed preferentially in each zone, respectively. We have analyzed the biological functions of some of these genes in this study. To clarify the regulatory mechanisms of gene expression profiles of these molecules in a migratory stage-dependent manner would be important in the future study.