Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG), Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan.
Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG), Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan; Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan.
Biochem Biophys Res Commun. 2020 Oct 8;531(1):67-74. doi: 10.1016/j.bbrc.2020.01.145. Epub 2020 Feb 5.
Guanine-rich DNA and RNA can form a four-stranded structure, termed G-quadruplexes (G4s) in vitro as well as in cells. The formation of G4 is implicated in many physiological events, such as gene transcription, translation, and epigenetics. However, the presence of G4 has not been revealed in the brain. Here, we demonstrate the localization of G4 in the mouse brain by immunohistochemical analysis. In cultured mouse forebrain neurons, numerous punctate G4 foci were observed in nuclei as well as in cytoplasmic areas, including axons, dendrites, and postsynapses. Interestingly, the G4 foci in nuclei show more marked co-localizations with the bright spots of DAPI-positive heterochromatin clusters in mature neurons compared to immature ones. In slices from adult mouse brain, the G4 foci were distributed throughout the brain but were particularly prominent in the hippocampus, olfactory bulb, and cerebellum. In the hippocampus, G4 foci were strongly expressed in neurons and weakly in astrocytes. Consistent with the results in cultured neurons, the nuclear G4 foci were co-localized with heterochromatin in calbindin-positive mature granule cells but less in doublecortin-positive neuronal progenitor cells in the dentate gyrus. Electron microscopic immunolabeling revealed G4 foci on nucleolus-associated chromosomal domains (NADs) and cytoplasm in the adult mouse hippocampal CA1 region. These observations suggest potentially critical roles of G4 in neuronal developmental stages through regulating chromatin structures and cytoplasmic metabolism of RNA.
富含鸟嘌呤的 DNA 和 RNA 可以形成一种四链结构，在体外和细胞中称为 G-四链体 (G4)。G4 的形成与许多生理事件有关，如基因转录、翻译和表观遗传学。然而，在大脑中尚未发现 G4 的存在。在这里，我们通过免疫组织化学分析证明了 G4 存在于小鼠大脑中。在培养的小鼠前脑神经元中，在细胞核以及细胞质区域（包括轴突、树突和突触后）中观察到大量点状 G4 焦点。有趣的是，与未成熟神经元相比，成熟神经元核中 G4 焦点与 DAPI 阳性异染色质簇的亮点表现出更明显的共定位。在成年小鼠脑切片中，G4 焦点分布在整个大脑中，但在海马体、嗅球和小脑尤为明显。在海马体中，G4 焦点在神经元中强烈表达，在星形胶质细胞中较弱。与培养神经元的结果一致，核 G4 焦点与齿状回 calbindin 阳性成熟颗粒细胞中的异染色质共定位，但在 doublecortin 阳性神经元祖细胞中较少共定位。电镜免疫标记显示成年小鼠海马 CA1 区核仁相关染色体区 (NAD) 和细胞质上存在 G4 焦点。这些观察结果表明，G4 通过调节染色质结构和 RNA 的细胞质代谢，在神经元发育阶段可能发挥关键作用。
