Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
UAB Mood Disorder Program, Division of Behavioral Neurobiology, Department of Psychiatry and Behavioral Neurobiology, UAB Depression and Suicide Center, University of Alabama at Birmingham, SC711 Sparks Center, 1720 7th Avenue South, Birmingham, AL, USA.
Sci Rep. 2022 Jan 7;12(1):194. doi: 10.1038/s41598-021-03863-y.
Chronic stress is one of the key precipitating factors in major depressive disorder (MDD). Stress associated studies have underscored the mechanistic role of epigenetic master players like microRNAs (miRNAs) in depression pathophysiology at both preclinical and clinical levels. Previously, we had reported changes in miR-218-5p expression in response to corticosterone (CORT) induced chronic stress. MiR-218-5p was one of the most significantly induced miRNAs in the prefrontal cortex (PFC) of rats under chronic stress. In the present report, we have investigated how chronic CORT exposure mechanistically affected miR-218-5p expression in the rat brain and how miR-218 could trigger molecular changes on its downstream regulatory pathways. Elevated expression of miR-218-5p was found in the PFC of CORT-treated rats. A glucocorticoid receptor (GR) targeted Chromatin-Immunoprecipitation (ChIP) assay revealed high GR occupancy on the promoter region of Slit3 gene hosting miR-218-2 in its 3rd intron. RNA-sequencing data based on RNA Induced silencing Complex Immunoprecipitation (RISC-IP) with AGO2 in SH-SY5Y cells detected six consistent target genes of miR-218-5p (APOL4, DTWD1, BNIP1, METTL22, SNAPC1, and HDAC6). The expression of all five genes, except APOL4, was successfully validated with qPCR in CORT-treated rat PFC. Further, Hdac6-based ChIP-seq experiment helped in mapping major genomic loci enriched for intergenic regions in the PFC of CORT-treated rat. A proximity-based gene ontology (GO) analysis revealed a majority of the intergenic sites to be part of key genes implicated in central nervous system functions, notably synapse organization, neuron projection morphogenesis, and axonogenesis. Our results suggest that the upregulation of miR-218-5p in PFC of CORT-treated rats possibly resulted from GR biding in the promoter region of Slit3 gene. Interestingly, Hdac6 was one of the consistent target genes potentially found to regulate CNS related genes by chromatin modification. Collectively, these findings establish the role of miR-218-5p in chronic stress and the epigenetic function it plays to induce chromatin-based transcriptional changes of several CNS genes in triggering stress-induced disorders, including depression. This also opens up the scope to understand the role of miR-218-5p as a potential target for noncoding RNA therapeutics in clinical depression.
慢性应激是重性抑郁障碍（MDD）的主要诱发因素之一。应激相关研究强调了表观遗传主调控因子（如 microRNAs，miRNAs）在临床前和临床水平上在抑郁发病机制中的作用。先前，我们已经报告了皮质酮（CORT）诱导的慢性应激后 miR-218-5p 表达的变化。在慢性应激大鼠的前额叶皮层（PFC）中，miR-218-5p 是表达上调最显著的 miRNA 之一。在本报告中，我们研究了慢性 CORT 暴露如何在大鼠脑中引发 miR-218-5p 的表达，并研究了 miR-218 如何触发其下游调控途径的分子变化。发现 CORT 处理大鼠的 PFC 中 miR-218-5p 的表达升高。糖皮质激素受体（GR）靶向染色质免疫沉淀（ChIP）试验显示，Slit3 基因启动子区域上的 GR 占据率很高，该基因在其第 3 内含子中包含 miR-218-2。基于 RNA 诱导沉默复合物免疫沉淀（RISC-IP）与 SH-SY5Y 细胞中的 AGO2 的 RNA 测序数据检测到 miR-218-5p 的六个一致靶基因（APOL4、DTWD1、BNIP1、METTL22、SNAPC1 和 HDAC6）。在 CORT 处理的大鼠 PFC 中，用 qPCR 成功验证了除 APOL4 之外的所有五个基因的表达。此外，Hdac6 基于的 ChIP-seq 实验有助于绘制 CORT 处理大鼠 PFC 中富含基因间区域的主要基因组位点图谱。基于邻近的基因本体论（GO）分析表明，大多数基因间位点是中枢神经系统功能关键基因的一部分，特别是突触组织、神经元投射形态发生和轴突发生。我们的结果表明，CORT 处理大鼠 PFC 中 miR-218-5p 的上调可能是由于 GR 在 Slit3 基因启动子区域的结合所致。有趣的是，Hdac6 是通过染色质修饰潜在调节 CNS 相关基因的一致靶基因之一。总的来说，这些发现确立了 miR-218-5p 在慢性应激中的作用，以及它通过诱导几种与 CNS 相关的基因的染色质相关转录变化在引发应激诱导的疾病（包括抑郁症）中发挥的表观遗传功能。这也为理解 miR-218-5p 作为临床抑郁症中非编码 RNA 治疗的潜在靶点开辟了道路。
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