Shen Meilun, Shang Mengjuan, Tian Ruofei, Hu Yang, Han Qian, Hu Junfeng, An Guangzhou, Wang Bingxia, Cao Zhi, Lin Xiaoyu, Yang Hao, Xing Junling
Department of Radiation Biology, Faculty of Preventive Medicine, Fourth Military Medical University, Xi'an, ShaanXi 710032, China.
Department of Cell Biology, National Translational Science Center for Molecular Medicine, Fourth Military Medical University, Xi'an, ShaanXi 710032, China.
Brain Res. 2023 May 15;1807:148309. doi: 10.1016/j.brainres.2023.148309. Epub 2023 Mar 2.
Recent evidence indicates that hippocampus is important for conditioned fear memory (CFM). Though few studies consider the roles of various cell types' contribution to such a process, as well as the accompanying transcriptome changes during this process. The purpose of this study was to explore the transcriptional regulatory genes and the targeted cells that are altered by CFM reconsolidation.
A fear conditioning experiment was established on adult male C57 mice, after day 3 tone-cued CFM reconsolidation test, hippocampus cells were dissociated. Using single cell RNA sequencing (scRNA-seq) technique, alterations of transcriptional genes expression were detected and cell cluster analysis were performed and compared with those in sham group.
Seven non-neuronal and eight neuronal cell clusters (including four known neurons and four newly identified neuronal subtypes) has been explored. Among them, CA subtype 1 has characteristic gene markers of Ttr and Ptgds, which is speculated to be the outcome of acute stress and promotes the production of CFM. The results of KEGG pathway enrichment indicate the differences in the expression of certain molecular protein functional subunits in long-term potentiation (LTP) pathway between two types of neurons (DG and CA1) and astrocytes, thus providing a new transcriptional perspective for the role of hippocampus in the CFM reconsolidation. More importantly, the correlation between the reconsolidation of CFM and neurodegenerative diseases-linked genes is substantiated by the results from cell-cell interactions and KEGG pathway enrichment. Further analysis shows that the reconsolidation of CFM inhibits the risk-factor genes App and ApoE in Alzheimer's Disease (AD) and activates the protective gene Lrp1.
This study reports the transcriptional genes expression changes of hippocampal cells driven by CFM, which confirm the involvement of LTP pathway and suggest the possibility of CFM-like behavior in preventing AD. However, the current research is limited to normal C57 mice, and further studies on AD model mice are needed to prove this preliminary conclusion.
近期证据表明，海马体对条件性恐惧记忆（CFM）至关重要。尽管很少有研究考虑各种细胞类型在此过程中的作用，以及此过程中伴随的转录组变化。本研究的目的是探索由CFM再巩固改变的转录调控基因和靶向细胞。
在成年雄性C57小鼠上建立恐惧条件反射实验，在第3天进行音调提示的CFM再巩固测试后，分离海马体细胞。使用单细胞RNA测序（scRNA-seq）技术，检测转录基因表达的变化并进行细胞聚类分析，并与假手术组进行比较。
已探索出7个非神经元细胞簇和8个神经元细胞簇（包括4种已知神经元和4种新鉴定的神经元亚型）。其中，CA1亚型具有Ttr和Ptgds的特征性基因标记，推测这是急性应激的结果，并促进CFM的产生。KEGG通路富集结果表明，两种类型的神经元（DG和CA1）与星形胶质细胞在长时程增强（LTP）通路中某些分子蛋白功能亚基的表达存在差异，从而为海马体在CFM再巩固中的作用提供了新的转录视角。更重要的是，细胞间相互作用和KEGG通路富集的结果证实了CFM再巩固与神经退行性疾病相关基因之间的相关性。进一步分析表明，CFM的再巩固抑制了阿尔茨海默病（AD）中的危险因素基因App和ApoE，并激活了保护基因Lrp1。
本研究报告了由CFM驱动的海马体细胞转录基因表达变化，证实了LTP通路的参与，并提示了类似CFM的行为预防AD的可能性。然而，目前的研究仅限于正常C57小鼠，需要对AD模型小鼠进行进一步研究以证实这一初步结论。
