The Big Role of Small RNAs in Anxiety and Stress-Related Disorders

MAPK Is a Mutual Pathway Targeted by Anxiety-Related miRNAs, and E2F5 Is a Putative Target for Anxiolytic miRNAs

Anxiety-related disorders (ARDs) are chronic neuropsychological diseases and the sixth leading cause of disability in the world. As dysregulation of microRNAs (miRs) are observed in the pathological course of neuropsychiatric disorders, the present study aimed to introduce miRs that underlie anxiety processing in the brain. First, we collected the experimentally confirmed anxiety-related miRNAs (ARmiRs), predicted their target transcripts, and introduced critical cellular pathways with key commune hub genes. As a result, we have found nine anxiolytic and ten anxiogenic ARmiRs. The anxiolytic miRs frequently target the mRNA of Acyl-CoA synthetase long-chain family member 4 (Acsl4), AFF4-AF4/FMR2 family member 4 (Aff4), and Krüppel like transcription factor 4 (Klf4) genes, where miR-34b-5p and miR-34c-5p interact with all of them. Moreover, the anxiogenic miRs frequently target the mRNA of nine genes; among them, only two miR (miR-142-5p and miR-218-5p) have no interaction with the mRNA of trinucleotide repeat-containing adaptor 6B (Tnrc6b), and miR-124-3p interacts with all of them where MAPK is the main signaling pathway affected by both anxiolytic and anxiogenic miR. In addition, the anxiolytic miR commonly target E2F transcription factor 5 (E2F5) in the TGF-β signaling pathway, and the anxiogenic miR commonly target Ataxin 1 (Atxn1), WASP-like actin nucleation promoting factor (Wasl), and Solute Carrier Family 17 Member 6 (Slc17a6) genes in the notch signaling, adherence junction, and synaptic vesicle cycle pathways, respectively. Taken together, we conclude that the most important anxiolytic (miR-34c, Let-7d, and miR-17) and anxiogenic (miR-19b, miR-92a, and 218) miR, as hub epigenetic modulators, potentially influence the pathophysiology of anxiety, primarily via interaction with the MAPK signaling pathway. Moreover, the role of E2F5 as a novel putative target for anxiolytic miRNAs in ARDs disorders deserves further exploration.

A functional SNP rs895819 on pre-miR-27a is associated with bipolar disorder by targeting NCAM1

The aberrant expression or genomic mutations of microRNA are associated with several human diseases. This study analyzes the relationship between genetic variations of miRNA and schizophrenia or bipolar disorder. We performed case-control studies for ten SNPs in a total sample of 1584 subjects. All these ten SNPs were on or near mature microRNAs. We identified the association between bipolar disorder and the T/C polymorphism at rs895819. To illustrate the function of miR-27a, we constructed several miR-27a knockout (KO) cell lines, determined candidates of miR-27a, and then verified NCAM1 as a target gene of miR-27a. Further studies revealed that the T/C polymorphism on miR-27a led to the differential expression of mature and precursor miR-27a without affecting the expression of primary miR-27a. Furthermore, the C mutation on pre-miR-27a suppresses cell migration and dopamine expression levels. Our study highlights the importance of miR-27a and its polymorphism at rs895819 in bipolar disorder.

A T/C variant in miR-27a is associated with bipolar disorder, potentially by reducing the ability of this microRNA to target important neurodevelopmental genes like NCAM1.

Fear conditioning downregulates miR-138 expression in the hippocampus to facilitate the formation of fear memory

Fear memory is important for the survival of animals and is associated with certain anxiety disorders, such as posttraumatic stress disorder. A thorough understanding of the molecular mechanisms of fear memory, especially associative fear memory, is imperative. MicroRNA-138 (miR-138) is a widely distributed microRNA in the brain and is locally enriched at synaptic sites. The role of miR-138 in the formation of fear memory is still largely unknown. In this study, a contextual fear conditioning (CFC) paradigm, bioinformatic methods, a luciferase assay, real-time PCR and western blot were used to evaluate the detailed effects of miR-138 on fear memory. We found that miR-138 transiently decreased in the dorsal hippocampus (DH) after CFC training. Upregulation or downregulation of miR-138 in the DH with miR-138 agomir or antagomir treatment significantly impaired or enhanced the formation of CFC memory, respectively. Moreover, the effects of miR-138 in the DH on the formation of CFC memory were achieved by changing the expression of the downstream target gene calpain 1 (Capn1). Taken together, both the in-vitro evidence and the in-vivo evidence presented in this study support the involvement of miR-138 in CFC memory formation, at least partly via the regulation of Capn1-mediated synaptic plasticity changes. Therapeutic use of miR-138/Capn1 is promising as an alternative option in the treatment of fear memory-related anxiety disorders.