Supèr H, Soriano E, Uylings H B
Department of Animal and Plant Cell Biology, Faculty of Biology, University of Barcelona, Spain.
Brain Res Brain Res Rev. 1998 Jun;27(1):40-64. doi: 10.1016/s0165-0173(98)00005-8.
Recently, it has been shown that the early developmental organization of the archicortical hippocampus resembles that of the neocortex. In both cortices at embryonic stages, a preplate is present, which is split by the formation of the cortical plate into a marginal zone and a subplate layer. The pioneer neurons of the preplate are believed to form a phylogenetically ancient cortical structure. Neurons in these preplate layers are the first postmitotic neurons and have important roles in the development of the cerebral cortex. Cajal-Retzius cells in the marginal zone regulate the phenotype of radial glial cells and may direct neuronal migration establishing the inside-out gradient of corticogenesis. Furthermore, pioneer neurons form the initial axonal connections with other (sub)cortical structures. A significant difference between the hippocampus and neocortex, however, is that in the hippocampus, most afferents are guided by the pioneer neurons in the prominent marginal zone, while in the neocortex most ingrowing afferent axons enter via the subplate. At later developmental periods, most pioneer neurons disappear by cell death or transform into other neuronal shapes. Here, we review the early developmental organization of the mammalian cerebral cortex (both neocortex and hippocampus) and discuss the functions and fate of pioneer neurons in cortical development, in particular that of Cajal-Retzius cells. Evaluating the developmental properties of the hippocampus and neocortex, we present the hypothesis that the distribution of the main ingrowing afferent systems in the developing neocortex, which differs from the one in the hippocampal region, may have enabled the specific evolution of the neocortex.
最近的研究表明，古皮质海马体的早期发育组织与新皮质相似。在胚胎期的这两种皮质中，都存在一个前板层，该前板层会因皮质板的形成而分裂为一个边缘区和一个亚板层。前板层的先驱神经元被认为形成了一种系统发育上古老的皮质结构。这些前板层中的神经元是最早的有丝分裂后神经元，在大脑皮质的发育中具有重要作用。边缘区的 Cajal-Retzius 细胞调节放射状胶质细胞的表型，并可能指导神经元迁移，建立皮质发生的由内向外梯度。此外，先驱神经元与其他（亚）皮质结构形成最初的轴突连接。然而，海马体和新皮质之间的一个显著差异在于，在海马体中，大多数传入纤维由突出的边缘区中的先驱神经元引导，而在新皮质中，大多数向内生长的传入轴突通过亚板层进入。在发育后期，大多数先驱神经元通过细胞死亡消失或转变为其他神经元形态。在这里，我们回顾了哺乳动物大脑皮质（新皮质和海马体）的早期发育组织，并讨论了先驱神经元在皮质发育中的功能和命运，特别是 Cajal-Retzius 细胞的功能和命运。通过评估海马体和新皮质的发育特性，我们提出了一个假说，即发育中的新皮质中主要向内生长的传入系统的分布与海马体区域不同，这可能促成了新皮质的特定进化。
