Department of Human Anatomy, School of Medicine, Murcia Institute of Biomedical Research, University of Murcia, El Palmar, 30120 Murcia, Spain.
Department of Cell Biology, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain.
Int J Mol Sci. 2023 Jun 5;24(11):9769. doi: 10.3390/ijms24119769.
This essay reexamines molecular evidence supporting the existence of the 'preisthmus', a caudal midbrain domain present in vertebrates (studied here in the mouse). It is thought to derive from the embryonic m2 mesomere and appears intercalated between the isthmus (caudally) and the inferior colliculus (rostrally). Among a substantial list of gene expression mappings examined from the Allen Developing and Adult Brain Atlases, a number of quite consistent selective positive markers, plus some neatly negative markers, were followed across embryonic stages E11.5, E13.5, E15.5, E18.5, and several postnatal stages up to the adult brain. Both alar and basal subdomains of this transverse territory were explored and illustrated. It is argued that the peculiar molecular and structural profile of the preisthmus is due to its position as rostrally adjacent to the isthmic organizer, where high levels of both FGF8 and WNT1 morphogens must exist at early embryonic stages. Isthmic patterning of the midbrain is discussed in this context. Studies of the effects of the isthmic morphogens usually do not attend to the largely unknown preisthmic complex. The adult alar derivatives of the preisthmus were confirmed to comprise a specific preisthmic sector of the periaqueductal gray, an intermediate stratum represented by the classic cuneiform nucleus, and a superficial stratum containing the subbrachial nucleus. The basal derivatives, occupying a narrow retrorubral domain intercalated between the oculomotor and trochlear motor nuclei, include dopaminergic and serotonergic neurons, as well as a variety of peptidergic neuron types.
本文重新审视了支持‘preisthmus’存在的分子证据，该结构存在于脊椎动物（本文以小鼠为研究对象）的中脑尾部。它被认为源自胚胎 m2 中胚节，位于脑桥（尾部）和下丘（头部）之间。在 Allen 发育和成人脑图谱中检查的大量基因表达图谱中，在胚胎阶段 E11.5、E13.5、E15.5、E18.5 以及出生后多个阶段直至成年脑，发现了一些相当一致的阳性选择性标记物和一些明显的阴性标记物。该横向区域的翼状和基底亚区都进行了探索和说明。有人认为，preisthmus 的特殊分子和结构特征与其位于靠近脑桥组织者的头部相邻的位置有关，在早期胚胎阶段，这里必须存在高水平的 FGF8 和 WNT1 形态发生素。在此背景下讨论了中脑的脑桥模式化。对脑桥形态发生素的影响的研究通常不关注尚未被广泛了解的 preisthmus 复合体。preisthmus 的成年翼状突衍生物被证实包含了导水管周围灰质的一个特定的 preisthmus 区、由经典楔形核代表的中间层和含有臂旁核的浅层。基底衍生物位于动眼神经核和滑车神经核之间的狭窄的 retro-rubral 区域，包含多巴胺能和 5-羟色胺能神经元以及各种肽能神经元类型。
