Department of Cell and Tissues, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt.
Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Sohag University, Sohag, Egypt.
Microsc Res Tech. 2024 Oct;87(10):2336-2354. doi: 10.1002/jemt.24617. Epub 2024 May 22.
Teleost fish exhibit the most pronounced and widespread adult neurogenesis. Recently, functional development and the fate of newborn neurons have been reported in the optic tectum (OT) of fish. To determine the role of neurogenesis in the OT, this study used histological, immunohistochemical, and electron microscopic investigations on 18 adult Molly fish specimens (Poecilia sphenops). The OT of the Molly fish was a bilateral lobed structure located in the dorsal part of the mesencephalon. It exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. The stratum opticum (SO) was supplied by optic nerve fibers, in which the neuropil was the main component. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). Furthermore, oligodendrocytes with their processes wrapped around the nerve fibers could be observed. The stratum album centrale (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. The neuronal cells of the SO and large tectal cells of the SAC expressed autophagy-related protein-5 (APG5). Interleukin-1β (IL-1β) was expressed in both neurons and glia cells of SGC. Additionally, inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventriculare (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. In all strata, S100 protein and Oligodendrocyte Lineage Transcription Factor 2 (Olig2) were expressed by microglia, oligodendrocytes, and astrocytes. In conclusion, it was possible to identify different varieties of neurons in the optic tectum, each with a distinct role. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT. RESEARCH HIGHLIGHTS: The OT of the Molly fish exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). The stratum album central (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. Inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventricular (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT.
硬骨鱼表现出最显著和广泛的成年神经发生。最近，鱼类视顶盖（OT）中的新生神经元的功能发育和命运已经有报道。为了确定神经发生在 OT 中的作用，本研究使用组织学、免疫组织化学和电子显微镜对 18 个成年 Molly 鱼标本（Poecilia sphenops）进行了研究。Molly 鱼的 OT 是位于中脑背侧的双侧叶状结构。它具有由纤维和细胞层交替组成的层状结构，组织成六个主要层。光感受器层（SO）由视神经纤维供应，其中神经原纤维是主要成分。在纤维状和灰色浅层（SFGS）中观察到具有微管束的放射状双极神经元。此外，可以观察到其过程缠绕在神经纤维周围的少突胶质细胞。中央白蛋白层（SAC）主要由中央灰质层（SGC）和大视丘、梨形和水平神经元的轴突组成。SO 和 SAC 的大视丘细胞的神经元表达自噬相关蛋白-5（APG5）。白细胞介素-1β（IL-1β）在 SGC 的神经元和神经胶质细胞中均有表达。此外，诱导型一氧化氮合酶（iNOS）在 SAC 突触层的神经原纤维和室旁层（SPV）的颗粒细胞中表达。此外，转化生长因子-β（TGF-β）、SRY 盒转录因子 9（SOX9）和肌肉生长抑制素在增殖神经元中明显表达。在所有层中，S100 蛋白和少突胶质细胞谱系转录因子 2（Olig2）由小胶质细胞、少突胶质细胞和星形胶质细胞表达。总之，可以在视顶盖中识别出不同种类的神经元，每种神经元都具有不同的作用。星形胶质细胞、增殖神经元和干细胞的存在突出了 OT 的再生能力。研究亮点：Molly 鱼的 OT 表现出由纤维和细胞层交替组成的层状结构，组织成六个主要层。在纤维状和灰色浅层（SFGS）中观察到具有微管束的放射状双极神经元。中央白蛋白层（SAC）主要由中央灰质层（SGC）和大视丘、梨形和水平神经元的轴突组成。诱导型一氧化氮合酶（iNOS）在 SAC 突触层的神经原纤维和室旁层（SPV）的颗粒细胞中表达。此外，转化生长因子-β（TGF-β）、SRY 盒转录因子 9（SOX9）和肌肉生长抑制素在增殖神经元中明显表达。星形胶质细胞、增殖神经元和干细胞的存在突出了 OT 的再生能力。
