Objective: To analyze the differential genes and related signaling pathways of microglia subpopulations in Parkinson's disease (PD) -like mouse brains induced by paraquat (PQ) based on single-cell RNA sequencing, and provide clues to elucidate the mechanism of PQ-induced PD-like changes in the brain of animals. Methods: In September 2021, six male 6-week-old C57BL/6 mice were randomly divided into control group and experimental group (three mice in each group) . The mice were injected with saline, 10.0 mg/kg PQ intraperitoneally, once every three days, and 10 consecutive injections were used for modeling. After infection, the brains of mice were taken and 10×Genomics single-cell RNA sequencing was performed. Microglia subpopulations were screened based on gene expression characteristics, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed. The differential genes of microglia subpopulations between the experimental group and control group were further screened, and functional enrichment analysis was performed using bioinformatics tools. Mouse microglia (BV2 cells) were treated with 0, 60, 90 μmol/L PQ solution, respectively. And real-time fluorescence quantitative PCR experiments were conducted to validate the expressions of differential genes hexokinase 2 (Hk2) , ATPase H+ Transporting V0 Subunit B (Atp6v0b) and Neuregulin 1 (Nrg1) . Results: Cluster 7 and Cluster 20 were identified as microglia subpopulations based on the signature genes inositol polyphosphate-5-phosphatase d, Inpp5d (Inpp5d) and transforming growth factor beta receptor 1 (Tgfbr1) , and they reflected the microglia-activated M2 phenotype. The bioinformatics analysis showed that the characteristic genes of identified microglia subpopulations were enriched in endocytosis. In terms of molecular function, it mainly enriched in transmembrane receptor protein kinase activity and cytokine binding. The up-regulated genes of Cluster 7 were mainly enriched in lysosomal pathway, endocytosis pathway, and down-regulated genes were mainly enriched in neurodegenerative disease and other signaling pathways. The up-regulated genes of Cluster 20 were mainly enriched in signaling pathways related to PD, and down-regulated genes were mainly enriched in cyclic adenosine 3', 5'-monophosphate (cAMP) signaling pathways, neurological development, synaptic function and other signaling pathways. The results of real-time fluorescence quantitative PCR showed that the expressions of Hk2 mRNA and Atp6v0b mRNA increased and the expression of Nrg1 mRNA decreased in the 90 μmol/L PQ-treated BV2 cells compared with the 0 μmol/L, and the differences were statistically significant (P<0.05) . Conclusion: Microglia are activated in the PQ-induced PD-like mouse model and polarized toward the M2 phenotype. And their functions are associated with lysosomal (endocytosis) , synaptic functions and the regulation of PD-related pathways.
目的： 基于单细胞转录组测序分析百草枯（PQ）诱导的帕金森病（PD）样小鼠大脑小胶质细胞亚群差异基因和相关信号通路，为阐明PQ致动物大脑PD样改变的机制研究提供线索。 方法： 于2021年9月，将6周龄C57BL/6雄性小鼠6只随机分为对照组和实验组（每组3只），分别以生理盐水、10.0 mg/kg PQ进行腹腔注射，每3天1次，连续10次注射造模。染毒结束后取小鼠大脑，进行10× Genomics单细胞转录组测序。根据基因表达特征筛选小胶质细胞亚群，进行基因本体（GO）富集分析和京都基因与基因组百科全书（KEGG）富集分析。进一步筛选实验组和对照组间小胶质细胞亚群的差异基因，利用生物信息学工具进行功能显著性富集分析。采用0、60、90 μmol/L的PQ溶液处理小鼠小胶质细胞（BV2细胞），通过实时荧光定量PCR实验验证差异基因己糖激酶2（Hk2）、ATPase H+转运V0亚基b（Atp6v0b）、神经调节蛋白1（Nrg1）的表达情况。 结果： 根据特征基因肌醇多磷酸-5-磷酸酶d（Inpp5d）和转化生长因子β受体1（Tgfbr1）将Cluster 7和Cluster 20亚群识别为小胶质细胞亚群，且该亚群反映小胶质细胞活化M2表型。生物信息学分析结果显示，所识别小胶质细胞亚群特征基因均富集到内吞作用；在分子功能方面主要富集跨膜受体蛋白激酶活性和细胞因子结合等功能。Cluster 7亚群上调基因主要富集于溶酶体通路、内吞作用等通路；下调基因主要富集于神经退行性疾病等信号通路。Cluster 20亚群上调基因主要富集于与PD相关的信号通路；下调基因主要富集于环磷酸腺苷（cAMP）信号传导途径、神经系统发育、突触功能等信号通路。实时荧光定量PCR检测结果显示，与0 μmol/L比较，90 μmol/L PQ溶液处理后BV2细胞的Hk2 mRNA和Atp6v0b mRNA表达水平升高，Nrg1 mRNA表达水平降低，差异均有统计学意义（P<0.05）。 结论： 小胶质细胞在PQ诱导的PD样小鼠模型中被激活，且向M2表型极化，其功能与溶酶体（内吞）、突触功能及PD相关信号通路的调节有关。.
Keywords: Differentially expressed gene; Enrichment analysis; Microglia; Paraquat; Parkinson's disease; Single-cell transcriptome.