N6-Methyladenosine Modification of Fatty Acid Amide Hydrolase Messenger RNA in Circular RNA STAG1–Regulated Astrocyte Dysfunction and Depressive-like Behaviors

Abstract

BACKGROUND: N 6-methyladenosine (m 6 A) 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 m 6 A 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 stresstreated 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 m 6 A 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 m 6 A methylation in the context of MDD, providing evidence that circSTAG1 may be a novel therapeutic target for MDD.

RNA Editing and Modifications in Mood Disorders

“…Huang et al showed that circSTAG1 overexpression inhibited the ALKBH5 translocation into the nucleus, leading to an increased m6A methylation of FAAH mRNA and its degradation in astrocytes. This in turn determined an improvement of astrocyte functionality and a reduction of depressive-like behaviors induced by CUS [90].…”

Early Life Stress Induced DNA Methylation of Monoamine Oxidases Leads to Depressive-Like Behavior

“…Methylated RNA immunoprecipitation sequence analysis in the peripheral blood found that circSTAG1 is significantly reduced in chronic unpredictable mild stress (CUMS) mice and MDD patients. On the contrary, overexpression of circSTAG1 induced a positive effect on CUMS-induced astrocyte dysfunction and depression-like behavior (Huang et al, 2020). With the same detection method, the methylation level of the serotonin 1-A receptor (5-HT1A) promoter was found to be closely related to mRNA transcription and protein expression, the presence of stress increased the level of 5-HT1A mRNA in the prefrontal cortex of CUMS mice by 50%.…”

Circular RNA: metabolism, functions and interactions with proteins

“…Additionally, circFOXP1 promotes the Warburg effect and gallbladder progression by increasing the cytoplasmic translocation of PTBP1 that binds to the 3′-UTR and coding region of pyruvate kinase L/R (PKLR) mRNA, protecting it from decay [ 138 ]. Similarly, circSTAG1 ameliorated astrocyte dysfunction and depressive-like behaviors induced by chronic unpredictable stress by capturing ALKBH5 in the cytoplasm and increasing m6A levels of fatty acid amide hydrolase (FAAH) mRNA [ 139 , 166 ]. CircBACH1 [ 140 ] and circZFP609 [ 141 ] also fall in this situation.…”