BACKGROUND N6-methyladenosine (m6A) is the most abundant epigenetic modification in eukaryotic messenger RNAs and is essential for multiple RNA processing events in physiological and pathological processes. However, precisely how m6A methylation is involved in major depressive disorder (MDD) is not fully understood. METHODS Circular RNA STAG1 (circSTAG1) was screened from the hippocampus of chronic unpredictable stress-treated mice using high-throughput RNA sequencing. Microinjection of circSTAG1 lentivirus into the mouse hippocampus was used to observe the role of circSTAG1 in depression. Sucrose preference, forced swim, and tail suspension tests were performed to evaluate the depressive-like behaviors of mice. Astrocyte dysfunction was examined by GFAP immunostaining and 3D reconstruction. Methylated RNA immunoprecipitation sequence analysis was used to identify downstream targets of circSTAG1/ALKBH5 (alkB homolog 5) axis. Cell Counting Kit-8 assay was performed to evaluate astrocyte viability in vitro. RESULTS circSTAG1 was significantly decreased in the chronic unpredictable stress-treated mouse hippocampus and in peripheral blood of patients with MDD. Overexpression of circSTAG1 notably attenuated astrocyte dysfunction and depressive-like behaviors induced by chronic unpredictable stress. Further examination indicated that overexpressed circSTAG1 captured ALKBH5 and decreased the translocation of ALKBH5 into the nucleus, leading to increased m6A methylation of fatty acid amide hydrolase (FAAH) messenger RNA and degradation of FAAH in astrocytes with subsequent attenuation of depressive-like behaviors and astrocyte loss induced by corticosterone in vitro. CONCLUSIONS Our findings dissect the functional link between circSTAG1 and m6A methylation in the context of MDD, providing evidence that circSTAG1 may be a novel therapeutic target for MDD.

中文翻译：

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N6-甲基腺苷修饰 circSTAG1 调节的星形胶质细胞功能障碍和抑郁样行为中的 FAAH mRNA

背景 N6-甲基腺苷 (m6A) 是真核信使 RNA 中最丰富的表观遗传修饰，对生理和病理过程中的多种 RNA 加工事件至关重要。然而，m6A 甲基化究竟如何参与重度抑郁症 (MDD) 尚不完全清楚。方法 使用高通量 RNA 测序从慢性不可预测的应激处理小鼠的海马中筛选出环状 RNA STAG1 (circSTAG1)。将circSTAG1慢病毒显微注射到小鼠海马中，观察circSTAG1在抑郁症中的作用。进行蔗糖偏好、强迫游泳和悬尾测试以评估小鼠的抑郁样行为。通过 GFAP 免疫染色和 3D 重建检查星形胶质细胞功能障碍。甲基化 RNA 免疫沉淀序列分析用于鉴定 circSTAG1/ALKBH5（alkB 同源物 5）轴的下游靶标。进行细胞计数 Kit-8 测定以评估体外星形胶质细胞的活力。结果 circSTAG1 在慢性不可预测的应激处理的小鼠海马和 MDD 患者的外周血中显着降低。circSTAG1 的过表达显着减轻了由慢性不可预测压力引起的星形胶质细胞功能障碍和抑郁样行为。进一步检查表明，过表达的 circSTAG1 捕获 ALKBH5 并减少 ALKBH5 易位到细胞核中，导致脂肪酸酰胺水解酶 (FAAH) 信使 RNA 的 m6A 甲基化增加和星形胶质细胞中 FAAH 的降解，随后在体外由皮质酮诱导的抑郁样行为和星形胶质细胞丢失减弱。结论 我们的研究结果剖析了 MDD 情况下 circSTAG1 和 m6A 甲基化之间的功能联系，为 circSTAG1 可能是 MDD 的新治疗靶点提供了证据。