Department of Biology, Faculty of Sciences, University of A Coruña, A Coruña, Spain.
Centro de Investigaciones Científicas Avanzadas (CICA), University of A Coruña, A Coruña, Spain.
J Comp Neurol. 2022 Jul;530(10):1569-1587. doi: 10.1002/cne.25297. Epub 2022 Feb 9.
We studied the expression of neurogranin in the brain and some sensory organs (barbel taste buds, olfactory organs, and retina) of adult zebrafish. Database analysis shows zebrafish has two paralog neurogranin genes (nrgna and nrgnb) that translate into three peptides with a conserved IQ domain, as in mammals. Western blots of zebrafish brain extracts using an anti-neurogranin antiserum revealed three separate bands, confirming the presence of three neurogranin peptides. Immunohistochemistry shows neurogranin-like expression in the brain and sensory organs (taste buds, neuromasts and olfactory epithelium), not being able to discern its three different peptides. In the retina, the most conspicuous positive cells were bipolar neurons. In the brain, immunopositive neurons were observed in all major regions (pallium, subpallium, preoptic area, hypothalamus, diencephalon, mesencephalon and rhombencephalon, including the cerebellum), a more extended distribution than in mammals. Interestingly, dendrites, cell bodies and axon terminals of some neurons were immunopositive, thus zebrafish neurogranins may play presynaptic and postsynaptic roles. Most positive neurons were found in primary sensory centers (viscerosensory column and medial octavolateral nucleus) and integrative centers (pallium, subpallium, optic tectum and cerebellum), which have complex synaptic circuitry. However, we also observed expression in areas not related to sensory or integrative functions, such as in cerebrospinal fluid-contacting cells associated with the hypothalamic recesses, which exhibited high neurogranin-like immunoreactivity. Together, these results reveal important differences with the patterns reported in mammals, suggesting divergent evolution from the common ancestor.
我们研究了成年斑马鱼大脑和一些感觉器官（触须味蕾、嗅觉器官和视网膜）中神经颗粒蛋白的表达。数据库分析表明，斑马鱼有两个神经颗粒蛋白基因（nrgna 和 nrgnb），它们翻译成三个具有保守 IQ 结构域的肽，与哺乳动物中的神经颗粒蛋白相似。使用抗神经颗粒蛋白抗血清对斑马鱼脑提取物进行的 Western blot 分析显示出三条独立的带，证实存在三种神经颗粒蛋白肽。免疫组织化学显示神经颗粒蛋白样表达存在于大脑和感觉器官（味蕾、毛细胞和嗅上皮）中，无法区分其三种不同的肽。在视网膜中，最明显的阳性细胞是双极神经元。在大脑中，观察到免疫阳性神经元存在于所有主要区域（皮层、皮层下、视前区、下丘脑、间脑、中脑和后脑，包括小脑），分布比哺乳动物更广泛。有趣的是，一些神经元的树突、胞体和轴突末端呈免疫阳性，因此斑马鱼神经颗粒蛋白可能发挥突触前和突触后作用。大多数阳性神经元存在于初级感觉中枢（内脏感觉柱和内侧八脑室核）和整合中枢（皮层、皮层下、视顶盖和小脑）中，这些中枢具有复杂的突触回路。然而，我们还观察到在与感觉或整合功能无关的区域表达，例如与下丘脑隐窝相关的脑脊液接触细胞，它们表现出高神经颗粒蛋白样免疫反应性。总之，这些结果揭示了与哺乳动物报道的模式的重要差异，表明与共同祖先的进化分歧。
