The entorhinal cortex (EC) is the spatial processing center of the brain and structurally is an interface between the three layered paleocortex and six layered neocortex, known as the periarchicortex. Limited studies indicate peculiarities in the formation of the EC such as early emergence of cells in layers (L) II and late deposition of LIII, as well as divergence in the timing of maturation of cell types in the superficial layers. In this study, we examine developmental events in the entorhinal cortex using an understudied model in neuroanatomy and development, the pig and supplement the research with BrdU labeling in the developing mouse EC. We determine the pig serves as an excellent anatomical model for studying human neurogenesis, given its long gestational length, presence of a moderate sized outer subventricular zone and early cessation of neurogenesis during gestation. Immunohistochemistry identified prominent clusters of OLIG2+ oligoprogenitor-like cells in the superficial layers of the lateral EC (LEC) that are sparser in the medial EC (MEC). These are first detected in the subplate during the early second trimester. MRI analyses reveal an acceleration of EC growth at the end of the second trimester. BrdU labeling of the developing MEC, shows the deeper layers form first and prior to the superficial layers, but the LV/VI emerges in parallel and the LII/III emerges later, but also in parallel. We coin this lamination pattern parallel lamination. The early-born Reln+ stellate cells in the superficial layers express the classic LV marker, Bcl11b (Ctip2) and arise from a common progenitor that forms the late deep layer LV neurons. In summary, we characterize the developing EC in a novel animal model and outline in detail the formation of the EC. We further provide insight into how the periarchicortex forms in the brain, which differs remarkably to the inside-out lamination of the neocortex.

中文翻译：

---

内嗅皮层的发育通过神经发生过程中的平行层压发生。

内嗅皮层（EC）是大脑的空间处理中心，在结构上是三层古皮质和六层新皮质（称为周围皮质）之间的界面。有限的研究表明 EC 形成的特殊性，例如 (L) II 层细胞的早期出现和 LIII 的晚期沉积，以及浅层细胞类型成熟时间的差异。在这项研究中，我们使用神经解剖学和发育中的猪模型来检查内嗅皮层的发育事件，并用发育中的小鼠 EC 中的 BrdU 标记来补充研究。我们确定猪是研究人类神经发生的优秀解剖模型，因为它的妊娠长度长、存在中等大小的外部脑室下区以及妊娠期间神经发生的早期停止。免疫组织化学在外侧 EC (LEC) 的表层中发现了明显的 OLIG2+ 寡祖细胞样细胞簇，而在内侧 EC (MEC) 中则稀疏。这些首先在妊娠中期早期在底板中检测到。MRI 分析显示妊娠中期末 EC 生长加速。发育中的 MEC 的 BrdU 标记显示较深层先于浅层形成，但 LV/VI 并行出现，LII/III 稍后出现，但也是并行的。我们创造了这种层压模式平行层压。浅层中早期出生的 Reln+ 星状细胞表达经典的 LV 标记物 Bcl11b (Ctip2)，并且源自形成晚期深层 LV 神经元的共同祖细胞。总之，我们描述了新型动物模型中正在发育的 EC，并详细概述了 EC 的形成。我们进一步深入了解大脑周围皮质的形成方式，它与新皮质的由内而外的层压结构显着不同。