Abstract
Fetalization associated with a delay in development and the preservation of the features of the embryonic structure of the brain dominates the ontogeny of salmonids. The aim of the present study was to comparatively analyze the distribution of the glial-type aNSC markers such as vimentin and glial fibrillar acidic protein (GFAP) and the migratory neuronal precursors such as doublecortin in the telencephalon subpallium of juvenile masu salmon, Oncorhynchus masou, in normal conditions and at 1 week after an injury to the dorsal pallium. Immunohistochemical labeling of vimentin, GFAP, and doublecortin in the pallium of intact juvenile masu salmon revealed single cells with similar morphologies corresponding to a persistent pool of neuronal and/or glial progenitors. The study of the posttraumatic process showed the presence of intensely GFAP-labeled cells of the neuroepithelial type that form reactive neurogenic zones in all areas of the subpallial zone of juvenile masu salmon. A comparative analysis of the distribution of radial glia in the dorsal, ventral, and lateral zones of the subpallium showed a maximum concentration of cells in the dorsal part of subpallium (VD) and a minimum concentration in the lateral part of subpallium VL. An essential feature of posttraumatic immunolabeling in the masu salmon subpallium is the GFAP distribution patterns that are granular intracellular in the apical periventricular zone (PVZ) and fibrillar extracellular in the subventricular (SVZ) and parenchymal zones (PZ). In contrast to those in intact animals, most of the GFAP+ granules and constitutive neurogenic niches in injured fish were localized in the basal part of the PVZ. With the traumatic injury to the subpallium, the number of Vim+ cells in the lateral and ventral regions significantly increased. At 1 week post-injury, the total immunolabeling of vimentin cells in the PVZ was replaced by the granular pattern of Vim immunodistribution spreading from the PVZ to the SVZ and deeper parenchymal layers of the brain in all areas of the subpallium. A significant increase in the number of DC+ cells was observed also in all areas of the subpallium. The number of cells increased both in the PVZ and in the SVZ, as well as in the deeper PZ. Thus, at 1 week after the injury to the dorsal pallium, the number of DC, Vim, and GFAP expressing cells of the neuroepithelial type in the subpallium of juvenile masu salmon increased, and additionally GFAP+ radial glia appeared in VD, which was absent from intact animals.
Highlights
The number of cells increased both in the periventricular zone (PVZ) and in the subventricular zone (SVZ), as well as in the deeper parenchymal zone (PZ)
At 1 week after the injury to the dorsal pallium, the number of DC, Vim, and glial fibrillar acidic protein (GFAP) expressing cells of the neuroepithelial type in the subpallium of juvenile masu salmon increased, and GFAP+ radial glia appeared in dorsal part of subpallium (VD), which was absent from intact animals
When doublecortin was immunolabeled in intact animals in all areas of the subpallium, positive cells were detected mainly in the periventricular (PVZ) and subventricular (SVZ)
Summary
This article is an open access articleThe telencephalon of teleost fishes, in contrast to the mammalian cerebral cortex, does not have a multilayer structure, but rather is formed by various cell clusters and extended cell populations and shows the ability to grow throughout life [1–6]. The bodies of embryonic stem cells and radial glial cells in the pallium are located on the surface of the brain, surrounded by the ventricular space and tela choroidea, a remnant of the roof plate [6]. Recent results of studies on perciforms have shown that, apart from the ventricular zone, there are very few proliferating cells in the dorsal pallium [6]. The proliferative potential of the telencephalon during active growth and the capability of increasing multifold in volume differ between various fish species [1,2,6,11]. These data apply more to the pallial regions of the brain than to the subpallium, which is much less studied
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