Determining the role of microRNAs in psychiatric disorders. Nat Rev Neurosci. 2015;16:201-212. [PMID: 25790865 DOI: 10.1038/nrn3879]

MicroRNA dysregulation in glutamate and dopamine pathways of schizophrenia: From molecular pathways to diagnostic and therapeutic approaches

Schizophrenia is a complex psychiatric disorder, and genetic and environmental factors have been implicated in its development. Dysregulated glutamatergic and dopaminergic transmission pathways are involved in schizophrenia development. Besides genetic mutations, epigenetic dysregulation has a considerable role in dysregulating molecular pathways involved in schizophrenia. MicroRNAs (miRNAs) are small, non-coding RNAs that target specific mRNAs and inhibit their translation into proteins. As epigenetic factors, miRNAs regulate many genes involved in glutamate and dopamine signaling pathways; thereby, their dysregulation can contribute to the development of schizophrenia. Secretion of specific miRNAs from damaged cells into body fluids can make them one of the ideal non-invasive biomarkers in the early diagnosis of schizophrenia. Also, understanding the molecular mechanisms of miRNAs in schizophrenia pathogenesis can pave the way for developing novel treatments for patients with schizophrenia. In this study, we reviewed the glutamatergic and dopaminergic pathophysiology and highlighted the role of miRNA dysregulation in schizophrenia development. Besides, we shed light on the significance of circulating miRNAs for schizophrenia diagnosis and the recent findings on the miRNA-based treatment for schizophrenia.

miR126-mediated impaired vascular integrity in Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder that is caused by mutations in melty-CpG binding protein 2 (MeCP2). MeCP2 is a non-cell type-specific DNA binding protein, and its mutation influences not only neural cells but also non-neural cells in the brain, including vasculature associated with endothelial cells. Vascular integrity is crucial for maintaining brain homeostasis, and its alteration may be linked to the pathology of neurodegenerative disease, but a non-neurogenic effect, especially the relationship between vascular alternation and Rett syndrome pathogenesis, has not been shown. Here, we recapitulate a microvascular network using Rett syndrome patient-derived induced pluripotent stem (iPS) cells that carry MeCP2[R306C] mutation to investigate early developmental vascular impact. To expedite endothelial cell differentiation, doxycycline (DOX)-inducible ETV2 expression vectors were inserted into the AAVS1 locus of Rett syndrome patient-derived iPS cells and its isogenic control by CRISPR/Cas9. With these endothelial cells, we established a disease microvascular network (Rett-dMVNs) and observed higher permeability in the Rett-dMVNs compared to isogenic controls, indicating altered barrier function by MeCP2 mutation. Furthermore, we unveiled that hyperpermeability is involved in the upregulation of miR126-3p in Rett syndrome patient-derived endothelial cells by microRNA profiling and RNAseq, and rescue of miR126-3p level can recover their phenotype. We discover miR126-3p-mediated vascular impairment in Rett syndrome patients and suggest the potential application of these findings for translational medicine.

Extracellular microRNAs associated with psychiatric symptoms in the Normative Aging Study

Earlier studies have revealed microRNAs (miRNAs) as potential biomarkers for neurological conditions, however, such evidence on psychiatric outcomes is limited. We utilized the Normative Aging Study (NAS) cohort to investigate the associations between extracellular miRNAs (ex-miRNA) and psychiatric symptoms among a group of older male adults, along with the targeted genes and biological pathways. We studied 569 participants with miRNA profile primarily measured in extracellular vesicles isolated from plasma, and psychiatric symptoms reported over 1996-2014 with repeated measures. Global and dimension scales of psychiatric symptoms were measured via the administration of Brief Symptom Inventory (BSI) per visit covering nine aspects of psychiatric health, such as anxiety, depression, hostility, psychoticism, etc. Ex-miRNAs were profiled using small RNA sequencing. Associations of expression of 395 ex-miRNAs (present in >70% samples) with current mental status were assessed using single-miRNA as well as Least Absolute Shrinkage and Selection Operator (LASSO)-based multi-miRNAs linear mixed effects models adjusting for key demographic and behavioral factors. Biological functions were explored using pathway analyses. We identified ex-miRNAs associated with each BSI scale. In particular, hsa-miR-320d was consistently identified for two global scales. Similar overlapping miRNAs across global and dimension scores included hsa-miR-379-3p, hsa-miR-1976, hsa-miR-151a-5p, hsa-miR-151b, hsa-miR-144-3p, etc. Top KEGG pathways for identified miRNAs included p53 signaling, Hippo signaling, FoxO signaling, protein processing in endoplasmic reticulum and several pathways related with cancer and neurological diseases. This study provided early evidence supporting the associations between extracellular miRNAs and psychiatric conditions. MiRNAs may serve as biomarkers of subclinical psychiatric illness in older adults.

Influence of antipsychotic drugs on microRNA expression in schizophrenia patients - A systematic review

Schizophrenia (SCZ) is a severe psychiatric disorder with unclear pathophysiology. Moreover, there is no specific biological marker to help clinicians to define a diagnosis, and medication is decided according to the psychiatrist's experience. In this scenario, microRNAs (miRNAs), which are small noncoding RNA molecules that regulate several genes, emerge as potential peripheral biomarkers to help not only the evaluation of the disease state but also the treatment response. Here, we systematically reviewed indexed literature and evaluated follow-up studies investigating the changes in miRNA expression due to antipsychotic treatment. We also assessed target genes and performed pathway enrichment analysis of miRNAs listed in this systematic review. A total of 11 studies were selected according to research criteria, and we observed that 28 miRNAs play a relevant role in schizophrenia pathogenesis or response to antipsychotic treatment, seven of those of extreme interest as possible biomarkers either for condition or treatment. Predicted targets of the miRNAs reviewed here were previously associated with schizophrenia in genome-wide studies, and pathway analysis showed enrichment for genes related to neural processes. With this review, we expect to highlight the importance of miRNAs in schizophrenia pathogenesis and its treatment and point out interesting miRNAs to future studies.

Stress-Related Roles of Exosomes and Exosomal miRNAs in Common Neuropsychiatric Disorders

Exosomes, natural nanovesicles that contain a cargo of biologically active molecules such as lipids, proteins, and nucleic acids, are released from cells to the extracellular environment. They then act as autocrine, paracrine, or endocrine mediators of communication between cells by delivering their cargo into recipient cells and causing downstream effects. Exosomes are greatly enriched in miRNAs, which are small non-coding RNAs that act both as cytoplasmic post-transcriptional repression agents, modulating the translation of mRNAs into proteins, as well as nuclear transcriptional gene activators. Neuronal exosomal miRNAs have important physiologic functions in the central nervous system (CNS), including cell-to-cell communication, synaptic plasticity, and neurogenesis, as well as modulating stress and inflammatory responses. Stress-induced changes in exosomal functions include effects on neurogenesis and neuroinflammation, which can lead to the appearance of various neuropsychiatric disorders such as schizophrenia, major depression, bipolar disorder, and Alzheimer's and Huntington's diseases. The current knowledge regarding the roles of exosomes in the pathophysiology of common mental disorders is discussed in this review.

Identification of novel endoplasmic reticulum-related genes and their association with immune cell infiltration in major depressive disorder

BACKGROUND

Several lines of evidence point to an interaction between genetic predisposition and environmental factors in the onset of major depressive disorder (MDD). This study is aimed to investigate the pathogenesis of MDD by identifying key biomarkers, associated immune infiltration using bioinformatic analysis and human postmortem sample.

METHODS

The Gene Expression Omnibus (GEO) database of GSE98793 was adopted to identify hub genes linked to endoplasmic reticulum (ER) stress-related genes (ERGs) in MDD. Another GEO database of GSE76826 was employed to validate the novel target associated with ERGs and immune infiltration in MDD. Moreover, human postmortem sample from MDD patients was utilized to confirm the differential expression analysis of hub genes.

RESULTS

We discovered 12 ER stress-related differentially expressed genes (ERDEGs). A LASSO Cox regression analysis helped construct a diagnostic model for these ERDEGs, incorporating immune infiltration analysis revealed that three hub genes (ERLIN1, SEC61B, and USP13) show the significant and consistent expression differences between the two groups. Western blot analysis of postmortem brain samples indicated notably higher expression levels of ERLIN1 and SEC61B in the MDD group, with USP13 also tending to increase compared to control group.

LIMITATIONS

The utilization of the MDD gene chip in this analysis was sourced from the GEO database, which possesses a restricted number of pertinent gene chip samples.

CONCLUSIONS

These findings indicate that ERDEGs especially including ERLIN1, SEC61B, and USP13 associated the infiltration of immune cells may be potential diagnostic indicators for MDD.

Exosomal miR-1202 mediates Brodmann Area 44 functional connectivity changes in medication-free patients with major depressive disorder: An fMRI study

Previous large-sample postmortem study revealed that the expression of miR-1202 in brain tissues from Brodmann area 44 (BA44) was dysregulated in patients with major depressive disorder (MDDs). However, the specific in vivo neuropathological mechanism of miR-1202 as well as its interplay with BA44 circuits in the depressed brain are still unclear. Here, we performed a case-control study with imaging-genetic approach based on resting-state functional magnetic resonance imaging (MRI) data and miR-1202 quantification from 110 medication-free MDDs and 102 healthy controls. Serum-derived circulating exosomes that readily cross the blood-brain barrier were isolated to quantify miR-1202. For validation, repeated MR scans were performed after a six-week follow-up of antidepressant treatment on a cohort of MDDs. Voxelwise factorial analysis revealed two brain areas (including the striatal-thalamic region) in which the effect of depression on the functional connectivity with BA44 was significantly dependent on the expression level of exosomal miR-1202. Moreover, longitudinal change of the BA44 connectivity with the striatal-thalamic region in MDDs after antidepressant treatment was found to be significantly related to the level of miR-1202 expression. These findings revealed that the in vivo neuropathological effect of miR-1202 dysregulation in depression is possibly exerted by mediating neural functional abnormalities in BA44-striatal-thalamic circuits.

MiRNA research-The potential for understanding the multiple facets of anorexia nervosa

Anorexia nervosa (AN) has a multifaceted and complex pathology, yet major gaps remain in our understanding of factors involved in AN pathology. MicroRNAs (miRNAs) play a regulatory role in translating genes into proteins and help understand and treat diseases. An extensive literature review on miRNAs with AN and comorbidities has uncovered a significant lack in miRNA research. To demonstrate the importance of understanding miRNA deregulation, we surveyed the literature on depression and obesity providing examples of relevant miRNAs. For AN, no miRNA sequencing or array studies have been found, unlike other psychiatric disorders. For depression and obesity, screenings and mechanistic studies were conducted, leading to clinical studies to improve understanding of their regulatory influences. MiRNAs are promising targets for studying AN due to their role as signaling molecules, involvement in psychiatric-metabolic axes, and potential as biomarkers. These characteristics offer valuable insights into the disease's etiology and potential new treatment options. The first miRNA-based treatment for rare metabolic disorders has been approved by the FDA and it is expected that these advancements will increase in the next decade. MiRNA research in AN is essential to examine its role in the development, manifestation, and progression of the disease. PUBLIC SIGNIFICANCE: The current understanding of the development and treatment of AN is insufficient. miRNAs are short regulatory sequences that influence the translation of genes into proteins. They are the subject of research in various diseases, including both metabolic and psychiatric disorders. Studying miRNAs in AN may elucidate their causal and regulatory role, uncover potential biomarkers, and allow for future targeted treatments.

Generation and transcriptomic characterization of MIR137 knockout miniature pig model for neurodevelopmental disorders

BACKGROUND

Neurodevelopmental disorders (NDD), such as autism spectrum disorders (ASD) and intellectual disorders (ID), are highly debilitating childhood psychiatric conditions. Genetic factors are recognized as playing a major role in NDD, with a multitude of genes and genomic regions implicated. While the functional validation of NDD-associated genes has predominantly been carried out using mouse models, the significant differences in brain structure and gene function between mice and humans have limited the effectiveness of mouse models in exploring the underlying mechanisms of NDD. Therefore, it is important to establish alternative animal models that are more evolutionarily aligned with humans.

RESULTS

In this study, we employed CRISPR/Cas9 and somatic cell nuclear transplantation technologies to successfully generate a knockout miniature pig model of the MIR137 gene, which encodes the neuropsychiatric disorder-associated microRNA miR-137. The homozygous knockout of MIR137 (MIR137-/-) effectively suppressed the expression of mature miR-137 and led to the birth of stillborn or short-lived piglets. Transcriptomic analysis revealed significant changes in genes associated with neurodevelopment and synaptic signaling in the brains of MIR137-/- miniature pig, mirroring findings from human ASD transcriptomic data. In comparison to miR-137-deficient mouse and human induced pluripotent stem cell (hiPSC)-derived neuron models, the miniature pig model exhibited more consistent changes in critical neuronal genes relevant to humans following the loss of miR-137. Furthermore, a comparative analysis identified differentially expressed genes associated with ASD and ID risk genes in both miniature pig and hiPSC-derived neurons. Notably, human-specific miR-137 targets, such as CAMK2A, known to be linked to cognitive impairments and NDD, exhibited dysregulation in MIR137-/- miniature pigs. These findings suggest that the loss of miR-137 in miniature pigs affects genes crucial for neurodevelopment, potentially contributing to the development of NDD.

CONCLUSIONS

Our study highlights the impact of miR-137 loss on critical genes involved in neurodevelopment and related disorders in MIR137-/- miniature pigs. It establishes the miniature pig model as a valuable tool for investigating neurodevelopmental disorders, providing valuable insights for potential applications in human research.

Effects of microRNA-305 knockdown on brain gene expression associated with division of labor in honey bee colonies (Apis mellifera)

Division of labor in honey bee colonies is based on the behavioral maturation of adult workers that involves a transition from working in the hive to foraging. This behavioral maturation is associated with distinct task-related transcriptomic profiles in the brain and abdominal fat body that are related to multiple regulatory factors including juvenile hormone (JH) and queen mandibular pheromone (QMP). A prominent physiological feature associated with behavioral maturation is a loss of abdominal lipid mass as bees transition to foraging. We used transcriptomic and physiological analyses to study whether microRNAs (miRNAs) are involved in the regulation of division of labor. We first identified two miRNAs that showed patterns of expression associated with behavioral maturation, ame-miR-305-5p and ame-miR-375-3p. We then downregulated the expression of these two miRNAs with sequence-specific antagomirs. Neither ame-miR-305-5p nor ame-miR-375-3p knockdown in the abdomen affected abdominal lipid mass on their own. Similarly, knockdown of ame-miR-305-5p in combination with JH or QMP also did not affect lipid mass. By contrast, ame-miR-305-5p knockdown in the abdomen caused substantial changes in gene expression in the brain. Brain gene expression changes included genes encoding transcription factors previously implicated in behavioral maturation. The results of these functional genomic experiments extend previous correlative associations of microRNAs with honey bee division of labor and point to specific roles for ame-miR-305-5p.

Clinical Insights into MicroRNAs in Depression: Bridging Molecular Discoveries and Therapeutic Potential

Depression is a major contributor to the overall global burden of disease. The discovery of biomarkers for diagnosis or prediction of treatment responses and as therapeutic agents is a current priority. Previous studies have demonstrated the importance of short RNA molecules in the etiology of depression. The most extensively researched of these are microRNAs, a major component of cellular gene regulation and function. MicroRNAs function in a temporal and tissue-specific manner to regulate and modify the post-transcriptional expression of target mRNAs. They can also be shuttled as cargo of extracellular vesicles between the brain and the blood, thus informing about relevant mechanisms in the CNS through the periphery. In fact, studies have already shown that microRNAs identified peripherally are dysregulated in the pathological phenotypes seen in depression. Our article aims to review the existing evidence on microRNA dysregulation in depression and to summarize and evaluate the growing body of evidence for the use of microRNAs as a target for diagnostics and RNA-based therapies.

Molecular underpinnings of programming by early-life stress and the protective effects of early dietary ω6/ω3 ratio, basally and in response to LPS: Integrated mRNA-miRNAs approach

Early-life stress (ELS) exposure increases the risk for mental disorders, including cognitive impairments later in life. We have previously demonstrated that an early diet with low ω6/ω3 polyunsaturated fatty acid (PUFA) ratio protects against ELS-induced cognitive impairments. Several studies have implicated the neuroimmune system in the ELS and diet mediated effects, but currently the molecular pathways via which ELS and early diet exert their long-term impact are not yet fully understood. Here we study the effects of ELS and dietary PUFA ratio on hippocampal mRNA and miRNA expression in adulthood, both under basal as well as inflammatory conditions. Male mice were exposed to chronic ELS by the limiting bedding and nesting material paradigm from postnatal day(P)2 to P9, and provided with a diet containing a standard (high (15:1.1)) or protective (low (1.1:1)) ω6 linoleic acid to ω3 alpha-linolenic acid ratio from P2 to P42. At P120, memory was assessed using the object location task. Subsequently, a single lipopolysaccharide (LPS) injection was given and 24 h later hippocampal genome-wide mRNA and microRNA (miRNA) expression was measured using microarray. Spatial learning deficits induced by ELS in mice fed the standard (high ω6/ω3) diet were reversed by the early-life protective (low ω6/ω3) diet. An integrated miRNA - mRNA analysis revealed that ELS and early diet induced miRNA driven mRNA expression changes into adulthood. Under basal conditions both ELS and the diet affected molecular pathways related to hippocampal plasticity, with the protective (low ω6/ω3 ratio) diet leading to activation of molecular pathways associated with improved hippocampal plasticity and learning and memory in mice previously exposed to ELS (e.g., CREB signaling and endocannabinoid neuronal synapse pathway). LPS induced miRNA and mRNA expression was strongly dependent on both ELS and early diet. In mice fed the standard (high ω6/ω3) diet, LPS increased miRNA expression leading to activation of inflammatory pathways. In contrast, in mice fed the protective diet, LPS reduced miRNA expression and altered target mRNA expression inhibiting inflammatory signaling pathways and pathways associated with hippocampal plasticity, which was especially apparent in mice previously exposed to ELS. This data provides molecular insights into how the protective (low ω6/ω3) diet during development could exert its long-lasting beneficial effects on hippocampal plasticity and learning and memory especially in a vulnerable population exposed to stress early in life, providing the basis for the development of intervention strategies.

Exploratory Analysis of MicroRNA Alterations in a Neurodevelopmental Mouse Model for Autism Spectrum Disorder and Schizophrenia

MicroRNAs (miRNAs) play a crucial role in the regulation of gene expression levels and have been implicated in the pathogenesis of autism spectrum disorder (ASD) and schizophrenia (SCZ). In this study, we examined the adult expression profiles of specific miRNAs in the prefrontal cortex (PFC) of a neurodevelopmental mouse model for ASD and SCZ that mimics perinatal pathology, such as NMDA receptor hypofunction, and exhibits behavioral and neurophysiological phenotypes related to these disorders during adulthood. To model the early neuropathogenesis of the disorders, mouse pups were administered subcutaneously with ketamine (30 mg/Kg) at postnatal days 7, 9, and 11. We focused on a set of miRNAs most frequently altered in ASD (miR-451a and miR-486-3p) and in SCZ (miR-132-3p and miR-137-3p) according to human studies. Additionally, we explored miRNAs whose alterations have been identified in both disorders (miR-21-5p, miR-92a-2-5p, miR-144-3p, and miR-146a-5p). We placed particular emphasis on studying the sexual dimorphism in the dynamics of these miRNAs. Our findings revealed significant alterations in the PFC of this ASD- and SCZ-like mouse model. Specifically, we observed upregulated miR-451a and downregulated miR-137-3p. Furthermore, we identified sexual dimorphism in the expression of miR-132-3p, miR-137-3p, and miR-92a-2-5p. From a translational perspective, our results emphasize the potential involvement of miR-92a-2-5p, miR-132-3p, miR-137-3p, and miR-451a in the pathophysiology of ASD and SCZ and strengthen their potential as biomarkers and therapeutic targets of such disorders.

Role of Hydrogen Sulfide in Oncological and Non-Oncological Disorders and Its Regulation by Non-Coding RNAs: A Comprehensive Review

Recently, myriad studies have defined the versatile abilities of gasotransmitters and their synthesizing enzymes to play a "Maestro" role in orchestrating several oncological and non-oncological circuits and, thus, nominated them as possible therapeutic targets. Although a significant amount of work has been conducted on the role of nitric oxide (NO) and carbon monoxide (CO) and their inter-relationship in the field of oncology, research about hydrogen sulfide (H2S) remains in its infancy. Recently, non-coding RNAs (ncRNAs) have been reported to play a dominating role in the regulation of the endogenous machinery system of H2S in several pathological contexts. A growing list of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are leading the way as upstream regulators for H2S biosynthesis in different mammalian cells during the development and progression of human diseases; therefore, their targeting can be of great therapeutic benefit. In the current review, the authors shed the light onto the biosynthetic pathways of H2S and their regulation by miRNAs and lncRNAs in various oncological and non-oncological disorders.

Target-induced multipath-to-one-substrate approach for high-efficient bioanalysis of microRNA

Considering the significant potential of microRNA (miRNA) as an efficient biomarker and great challenge of accurate analysis of lowly abundant miRNA, herein, we proposed a target-induced multipath-to-one-substrate strategy to monitor miRNA in vivo and in vitro accurately with high-efficient performances. In presence of target miRNA, it could directly generate the catalytic hairpin assembly (CHA) amplification cycle based on hybridizing with hairpin 1 (H1) and H2 respectively to structure the H1-H2 duplex, then the H1-H2 duplex could activate the cleavage ability of CRISPR/Cas12a to cleavage H1 which represent miRNA indirectly consume H1, which achieve co-consumption of the same substrate H1 by multiple pathways. And thus, the quenched fluorescent signal on H1 could be recovered due to the enlarger distance between fluorescent probe and quencher by the formation of H1-H2 duplex or cleavage of H1, all of which were related directly with target miRNA or indirectly with H1-H2 duplex activated cleavage ability of CRISPR/Cas12a, generating ultrahigh sensitive analytical ability and high-efficient analytical performances, such as more simple, fast, efficient and so on, especially a linear correlation from 100 pM to 100 nM with a detection limit of 78 pM, opening a new door to monitor expression level of biomolecules for early diagnosis and prognosis evaluation of various diseases.

L-type calcium channels and neuropsychiatric diseases: Insights into genetic risk variant-associated genomic regulation and impact on brain development

Recent human genetic studies have linked a variety of genetic variants in the CACNA1C and CACNA1D genes to neuropsychiatric and neurodevelopmental disorders. This is not surprising given the work from multiple laboratories using cell and animal models that have established that Cav1.2 and Cav1.3 L-type calcium channels (LTCCs), encoded by CACNA1C and CACNA1D, respectively, play a key role in various neuronal processes that are essential for normal brain development, connectivity, and experience-dependent plasticity. Of the multiple genetic aberrations reported, genome-wide association studies (GWASs) have identified multiple single nucleotide polymorphisms (SNPs) in CACNA1C and CACNA1D that are present within introns, in accordance with the growing body of literature establishing that large numbers of SNPs associated with complex diseases, including neuropsychiatric disorders, are present within non-coding regions. How these intronic SNPs affect gene expression has remained a question. Here, we review recent studies that are beginning to shed light on how neuropsychiatric-linked non-coding genetic variants can impact gene expression via regulation at the genomic and chromatin levels. We additionally review recent studies that are uncovering how altered calcium signaling through LTCCs impact some of the neuronal developmental processes, such as neurogenesis, neuron migration, and neuron differentiation. Together, the described changes in genomic regulation and disruptions in neurodevelopment provide possible mechanisms by which genetic variants of LTCC genes contribute to neuropsychiatric and neurodevelopmental disorders.

Early-life iron deficiency persistently disrupts affective behaviour in mice

BACKGROUND/OBJECTIVE

Iron deficiency (ID) is the most common nutrient deficiency, affecting two billion people worldwide, including about 30% of pregnant women. During gestation, the brain is particularly vulnerable to environmental insults, which can irrevocably impair critical developmental processes. Consequently, detrimental consequences of early-life ID for offspring brain structure and function have been described. Although early life ID has been associated with an increased long-term risk for several neuropsychiatric disorders, the effect on depressive disorders has remained unresolved.

MATERIALS AND METHODS

A mouse model of moderate foetal and neonatal ID was established by keeping pregnant dams on an iron-deficient diet throughout gestation until postnatal day 10. The ensuing significant decrease of iron content in the offspring brain, as well as the impact on maternal behaviour and offspring vocalization was determined in the first postnatal week. The consequences of early-life ID for depression- and anxiety-like behaviour in adulthood were revealed employing dedicated behavioural assays. miRNA sequencing of hippocampal tissue of offspring revealed specific miRNAs signatures accompanying the behavioural deficits of foetal and neonatal ID in the adult brain.

RESULTS

Mothers receiving iron-deficient food during pregnancy and lactation exhibited significantly less licking and grooming behaviour, while active pup retrieval and pup ultrasonic vocalizations were unaltered. Adult offspring with a history of foetal and neonatal ID showed an increase in depression- and anxiety-like behaviour, paralleled by a deranged miRNA expression profile in the hippocampus, specifically levels of miR200a and miR200b.

CONCLUSION

ID during the foetal and neonatal periods has life-long consequences for affective behaviour in mice and leaves a specific and persistent mark on the expression of miRNAs in the brain. Foetal and neonatal ID needs to be further considered as risk factor for the development of depression and anxiety disorders later in life.Key MessagesMarginal reduction of gestational alimentary iron intake decreases brain iron content of the juvenile offspring.Early-life ID is associated with increased depression- and anxiety-like behaviour in adulthood.Reduction of maternal alimentary iron intake during pregnancy is reflected in an alteration of miRNA signatures in the adult offspring brain.

Stress, microRNAs, and stress-related psychiatric disorders: an overview

Stress is a major risk factor for psychiatric disorders. During and after exposure to stressors, the stress response may have pro- or maladaptive consequences, depending on several factors related to the individual response and nature of the stressor. However, the mechanisms mediating the long-term effects of exposure to stress, which may ultimately lead to the development of stress-related disorders, are still largely unknown. Epigenetic mechanisms have been shown to mediate the effects of the environment on brain gene expression and behavior. MicroRNAs, small non-coding RNAs estimated to control the expression of about 60% of all genes by post-transcriptional regulation, are a fundamental epigenetic mechanism. Many microRNAs are expressed in the brain, where they work as fine-tuners of gene expression, with a key role in the regulation of homeostatic balance, and a likely influence on pro- or maladaptive brain changes. Here we have selected a number of microRNAs, which have been strongly implicated as mediators of the effects of stress in the brain and in the development of stress-related psychiatric disorders. For all of them recent evidence is reported, obtained from rodent stress models, manipulation of microRNAs levels with related behavioral changes, and clinical studies of stress-related psychiatric disorders. Moreover, we have performed a bioinformatic analysis of the predicted brain-expressed target genes of the microRNAs discussed, and found a central role for mechanisms involved in the regulation of synaptic function. The complex regulatory role of microRNAs has suggested their use as biomarkers for diagnosis and treatment response, as well as possible therapeutic drugs. While, microRNA-based diagnostics have registered advancements, particularly in oncology and other fields, and many biotech companies have launched miRNA therapeutics in their development pipeline, the development of microRNA-based tests and drugs for brain disorders is comparatively slower.

MicroRNA-409-5p Inhibits GIST Tumorigenesis and Improves Imatinib Resistance by Targeting KDM4D Expression

OBJECTIVE

Gastrointestinal stromal tumors (GISTs) can rapidly proliferate through angiogenesis. Previous studies indicated the potential influence of microRNA on the progression of tumor immature angiogenesis. This study aimed to explore the specific mechanism by which microRNA-409-5p (miR-409-5p) contributes to GIST.

METHODS

To identify genes potentially involved in the development and progression of GIST, the differences of miR-409-5p between tumors and adjacent tissues were first analyzed. Following this analysis, target genes were predicted. To further investigate the function of miRNA in GIST cells, two GIST cell lines (GIST-T1 and GIST882) were transfected with lentiviruses that stably expressed miR-409-5p and scrambled miRNA (negative control). Later, the cells were subjected to Western blotting and ELSA to determine any differences in angiogenesis-related genes.

RESULTS

In GISTs, there was a decrease in the expression levels of miR-409-5p compared to the adjacent tissues. It was observed that the upregulation of miR-409-5p in GIST cell lines effectively inhibited the proteins hypoxia-inducible transcription factor 1β (HIF1β) and vascular endothelial growth factor A (VEGF-A). Further investigations revealed that miR-409-5p acted as an inhibitor of angiogenesis by binding to the 3'-UTR of Lysine-specific demethylase 4D (KDM4D) mRNA. Moreover, the combination of miR-409-5p with imatinib enhanced its inhibitory effect on angiogenesis.

CONCLUSION

This study demonstrated that the miRNA-409-5p/KDM4D/HIF1β/VEGF-A signaling pathway could serve as a novel target for the development of therapeutic strategies for the treatment of imatinib-resistance in GIST patients.

Ethanol-induced AMPA alterations are mediated by mGLU5 receptors through miRNA upregulation in hippocampal slices

Prenatal alcohol exposure (PAE) affects neuronal networks and brain development causing a range of physical, cognitive and behavioural disorders in newborns that persist into adulthood. The array of consequences associated with PAE can be grouped under the umbrella-term 'fetal alcohol spectrum disorders' (FASD). Unfortunately, there is no cure for FASD as the molecular mechanisms underlying this pathology are still unknown. We have recently demonstrated that chronic EtOH exposure, followed by withdrawal, induces a significant decrease in AMPA receptor (AMPAR) expression and function in developing hippocampus in vitro. Here, we explored the EtOH-dependent pathways leading to hippocampal AMPAR suppression. Organotypic hippocampal slices (2 days in cultures) were exposed to EtOH (150 mM) for 7 days followed by 24 h EtOH withdrawal. Then, the slices were analysed by means of RT-PCR for miRNA content, western blotting for AMPA and NMDA related-synaptic proteins expression in postsynaptic compartment and electrophysiology to record electrical properties from CA1 pyramidal neurons. We observed that EtOH induces a significant downregulation of postsynaptic AMPA and NMDA subunits and relative scaffolding protein expression and, accordingly, a decrease of AMPA-mediated neurotransmission. Simultaneously, we found that chronic EtOH induced-upregulation of miRNA 137 and 501-3p and decreased AMPA-mediated neurotransmission are prevented by application of the selective mGlu5 antagonist MPEP during EtOH withdrawal. Our data indicate mGlu5 via miRNA137 and 501-3p expression as key factors in the regulation of AMPAergic neurotransmission that may contribute, at least in part, to the pathogenesis of FASD.

Inversely Regulated Inflammation-Related Processes Mediate Anxiety-Obesity Links in Zebrafish Larvae and Adults

Anxiety and metabolic impairments are often inter-related, but the underlying mechanisms are unknown. To seek RNAs involved in the anxiety disorder-metabolic disorder link, we subjected zebrafish larvae to caffeine-induced anxiety or high-fat diet (HFD)-induced obesity followed by RNA sequencing and analyses. Notably, differentially expressed (DE) transcripts in these larval models and an adult zebrafish caffeine-induced anxiety model, as well as the transcript profiles of inherently anxious versus less anxious zebrafish strains and high-fat diet-fed versus standard diet-fed adult zebrafish, revealed inversely regulated DE transcripts. In both larval anxiety and obesity models, these included long noncoding RNAs and transfer RNA fragments, with the overrepresented immune system and inflammation pathways, e.g., the "interleukin signaling pathway" and "inflammation mediated by chemokine and cytokine signaling pathway". In adulthood, overrepresented immune system processes included "T cell activation", "leukocyte cell-cell adhesion", and "antigen processing and presentation". Furthermore, unlike adult zebrafish, obesity in larvae was not accompanied by anxiety-like behavior. Together, these results may reflect an antagonistic pleiotropic phenomenon involving a re-adjusted modulation of the anxiety-metabolic links with an occurrence of the acquired immune system. Furthermore, the HFD potential to normalize anxiety-upregulated immune-related genes may reflect the high-fat diet protection of anxiety and neurodegeneration reported by others.

microRNA-dependent regulation of gene expression in GABAergic interneurons

Information processing within neuronal circuits relies on their proper development and a balanced interplay between principal and local inhibitory interneurons within those circuits. Gamma-aminobutyric acid (GABA)ergic inhibitory interneurons are a remarkably heterogeneous population, comprising subclasses based on their morphological, electrophysiological, and molecular features, with differential connectivity and activity patterns. microRNA (miRNA)-dependent post-transcriptional control of gene expression represents an important regulatory mechanism for neuronal development and plasticity. miRNAs are a large group of small non-coding RNAs (21-24 nucleotides) acting as negative regulators of mRNA translation and stability. However, while miRNA-dependent gene regulation in principal neurons has been described heretofore in several studies, an understanding of the role of miRNAs in inhibitory interneurons is only beginning to emerge. Recent research demonstrated that miRNAs are differentially expressed in interneuron subclasses, are vitally important for migration, maturation, and survival of interneurons during embryonic development and are crucial for cognitive function and memory formation. In this review, we discuss recent progress in understanding miRNA-dependent regulation of gene expression in interneuron development and function. We aim to shed light onto mechanisms by which miRNAs in GABAergic interneurons contribute to sculpting neuronal circuits, and how their dysregulation may underlie the emergence of numerous neurodevelopmental and neuropsychiatric disorders.

miR-483-5p offsets functional and behavioural effects of stress in male mice through synapse-targeted repression of Pgap2 in the basolateral amygdala

Severe psychological trauma triggers genetic, biochemical and morphological changes in amygdala neurons, which underpin the development of stress-induced behavioural abnormalities, such as high levels of anxiety. miRNAs are small, non-coding RNA fragments that orchestrate complex neuronal responses by simultaneous transcriptional/translational repression of multiple target genes. Here we show that miR-483-5p in the amygdala of male mice counterbalances the structural, functional and behavioural consequences of stress to promote a reduction in anxiety-like behaviour. Upon stress, miR-483-5p is upregulated in the synaptic compartment of amygdala neurons and directly represses three stress-associated genes: Pgap2, Gpx3 and Macf1. Upregulation of miR-483-5p leads to selective contraction of distal parts of the dendritic arbour and conversion of immature filopodia into mature, mushroom-like dendritic spines. Consistent with its role in reducing the stress response, upregulation of miR-483-5p in the basolateral amygdala produces a reduction in anxiety-like behaviour. Stress-induced neuromorphological and behavioural effects of miR-483-5p can be recapitulated by shRNA mediated suppression of Pgap2 and prevented by simultaneous overexpression of miR-483-5p-resistant Pgap2. Our results demonstrate that miR-483-5p is sufficient to confer a reduction in anxiety-like behaviour and point to miR-483-5p-mediated repression of Pgap2 as a critical cellular event offsetting the functional and behavioural consequences of psychological stress.

Brain-derived neurotrophic factor (BDNF) epigenomic modifications and brain-related phenotypes in humans: A systematic review

Epigenomic modifications of the brain-derived neurotrophic factor (BDNF) gene have been postulated to underlie the pathogenesis of neurodevelopmental, psychiatric, and neurological conditions. This systematic review summarizes current evidence investigating the association of BDNF epigenomic modifications (DNA methylation, non-coding RNA, histone modifications) with brain-related phenotypes in humans. A novel contribution is our creation of an open access web-based application, the BDNF DNA Methylation Map, to interactively visualize specific positions of CpG sites investigated across all studies for which relevant data were available. Our literature search of four databases through September 27, 2021 returned 1701 articles, of which 153 met inclusion criteria. Our review revealed exceptional heterogeneity in methodological approaches, hindering the identification of clear patterns of robust and/or replicated results. We summarize key findings and provide recommendations for future epigenomic research. The existing literature appears to remain in its infancy and requires additional rigorous research to fulfill its potential to explain BDNF-linked risk for brain-related conditions and improve our understanding of the molecular mechanisms underlying their pathogenesis.

Analysis of common genetic variation across targets of microRNAs dysregulated both in ASD and epilepsy reveals negative correlation

Genetic overlap involving rare disrupting mutations may contribute to high comorbidity rates between autism spectrum disorders and epilepsy. Despite their polygenic nature, genome-wide association studies have not reported a significant contribution of common genetic variation to comorbidity between both conditions. Analysis of common genetic variation affecting specific shared pathways such as miRNA dysregulation could help to elucidate the polygenic mechanisms underlying comorbidity between autism spectrum disorders and epilepsy. We evaluated here the role of common predisposing variation to autism spectrum disorders and epilepsy across target genes of 14 miRNAs selected through bibliographic research as being dysregulated in both disorders. We considered 4,581 target genes from various in silico sources. We described negative genetic correlation between autism spectrum disorders and epilepsy across variants located within target genes of the 14 miRNAs selected (p = 0.0228). Moreover, polygenic transmission disequilibrium test on an independent cohort of autism spectrum disorders trios (N = 233) revealed an under-transmission of autism spectrum disorders predisposing alleles within miRNAs’ target genes across autism spectrum disorders trios without comorbid epilepsy, thus reinforcing the negative relationship at the common genetic variation between both traits. Our study provides evidence of a negative relationship between autism spectrum disorders and epilepsy at the common genetic variation level that becomes more evident when focusing on the miRNA regulatory networks, which contrasts with observed clinical comorbidity and results from rare variation studies. Our findings may help to conceptualize the genetic heterogeneity and the comorbidity with epilepsy in autism spectrum disorders.

Potential of Circulating miRNAs as Molecular Markers in Mood Disorders and Associated Suicidal Behavior

Mood disorders are the most prevalent psychiatric disorders associated with significant disability, morbidity, and mortality. The risk of suicide is associated with severe or mixed depressive episodes in patients with mood disorders. However, the risk of suicide increases with the severity of depressive episodes and is often presented with higher incidences in bipolar disorder (BD) patients than in patients with major depression (MDD). Biomarker study in neuropsychiatric disorders is critical for developing better treatment plans by facilitating more accurate diagnosis. At the same time, biomarker discovery also provides more objectivity to develop state-of-the-art personalized medicine with increased accuracy through clinical interventions. Recently, colinear changes in miRNA expression between brain and systemic circulation have added great interest in examining their potential as molecular markers in mental disorders, including MDD, BD, and suicidality. A present understanding of circulating miRNAs in body fluids implicates their role in managing neuropsychiatric conditions. Most notably, their use as prognostic and diagnostic markers and their potential role in treatment response have significantly advanced our knowledge base. The present review discusses circulatory miRNAs and their underlying possibilities to be used as a screening tool for assessing major psychiatric conditions, including MDD, BD, and suicidal behavior.

The long-lasting effects of early life adversities are sex dependent: The signature of miR-34a

BACKGROUND

Exposure to early life adversities (ELA) can influence a plethora of biological mechanisms leading to stress-related disorders later in life through epigenetic mechanisms, such as microRNAs (miRs). MiR-34 is a critical modulator of stress response and stress-induced pathologies and a link between ELA and miR-34a has been reported.

METHODS

Here using our well-established model of ELA (Repeated Cross Fostering) we investigate the behavioral long-term effects of ELA in male and female mice. We also assess basal and ELA-induced miR-34a expression in adult mice and investigate whether ELA affects the later miR-34a response to adult acute stress exposure across brain areas (medial preFrontal Cortex, Dorsal Raphe Nuclei) and peripheral organs (heart, plasma) in animals from both sexes. Finally, based on our previous data demonstrating the critical role of Dorsal Raphe Nuclei miR-34a expression in serotonin (5-HT) transmission, we also investigated prefrontal-accumbal 5-HT outflow induced by acute stress exposure in ELA and Control females by in vivo intracerebral microdialysis.

RESULTS

ELA not just induces a depressive-like state as well as enduring changes in miR-34a expression, but also alters miR-34a expression in response to adult acute stress exclusively in females. Finally, altered DRN miR-34a expression is associated with prefrontal-accumbal 5-HT release under acute stress exposure in females.

LIMITATIONS

Translational study on humans is necessary to verify the results obtained in our animal models of ELA-induced depression.

CONCLUSIONS

This is the first evidence showing long-lasting sex related effects of ELA on brain and peripheral miR-34a expression levels in an animal model of depression-like phenotype.

The diagnostic utility of miRNA and elucidation of pathological mechanisms in major depressive disorder

AIMS

Our study aims to explore how miRNAs can elucidate the molecular mechanisms of major depressive disorder (MDD) by comparing the miRNA levels in the blood serum of patients with depression and healthy individuals. It also explores the potential of miRNAs to differentiate between depressed patients and healthy controls.

METHODS

60 healthy controls (n = 45 females) were matched to 60 depressed patients (n = 10 unmedicated) for age (±7), sex, ethnicity, and years of education. Depression severity was measured using the Hamilton Depression Rating Scale, and venous blood was collected using PAXgene Blood RNA tubes for miRNA profiling. To further identify the depression-related biological pathways that are influenced by differentially expressed miRNAs, networks were constructed using QIAGEN Ingenuity Pathway Analysis. Receiver operating characteristic (ROC) analyses were also conducted to examine the discriminative ability of miRNAs to distinguish between depressed and healthy individuals.

RESULTS

Six miRNAs (miR-542-3p, miR-181b-3p, miR-190a-5p, miR-33a-3p, miR-3690 and miR-6895-3p) showed to be considerably down-regulated in unmedicated depressed patients relative to healthy controls. miR-542-3p, in particular, also has experimentally verified mRNA targets that are predicted to be associated with MDD. ROC analyses found that a panel combining miR-542-3p, miR-181b-3p and miR-3690 produced an area under the curve value of 0.67 in distinguishing between depressed and healthy individuals.

CONCLUSIONS

miRNAs - most notably, miR-542-3p, miR-181b-3p and miR-3690 - may be biomarkers with targets that are implicated in the pathophysiology of depression. They could also be used to distinguish between depressed and healthy individuals with reasonable accuracy.

Involvement of miR-135a-5p Downregulation in Acute and Chronic Stress Response in the Prefrontal Cortex of Rats

Stress is a key risk factor in the onset of neuropsychiatric disorders. The study of the mechanisms underlying stress response is important to understand the etiopathogenetic mechanisms and identify new putative therapeutic targets. In this context, microRNAs (miRNAs) have emerged as key regulators of the complex patterns of gene/protein expression changes in the brain, where they have a crucial role in the regulation of neuroplasticity, neurogenesis, and neuronal differentiation. Among them, miR-135a-5p has been associated with stress response, synaptic plasticity, and the antidepressant effect in different brain areas. Here, we used acute unavoidable foot-shock stress (FS) and chronic mild stress (CMS) on male rats to study whether miR-135a-5p was involved in stress-induced changes in the prefrontal cortex (PFC). Both acute and chronic stress decreased miR-135a-5p levels in the PFC, although after CMS the reduction was induced only in animals vulnerable to CMS, according to a sucrose preference test. MiR-135a-5p downregulation in the primary neurons reduced dendritic spine density, while its overexpression exerted the opposite effect. Two bioinformatically predicted target genes, Kif5c and Cplx1/2, were increased in FS rats 24 h after stress. Altogether, we found that miR-135a-5p might play a role in stress response in PFC involving synaptic mechanisms.

Anti-inflammatory effect of miR-125a-5p on experimental optic neuritis by promoting the differentiation of Treg cells

Methylprednisolone pulse treatment is currently used for optic neuritis. It can speed visual recovery, but does not improve the ultimate visual outcomes. Recent studies have reported that miR-125a-5p has immunomodulatory effects on autoimmune diseases. However, it remains unclear whether miR-125a-5p has effects on optic neuritis. In this study, we used adeno-associated virus to overexpress or silence miR-125a-5p in mice. We found that silencing miR-125a-5p increased the latency of visual evoked potential and aggravated inflammation of the optic nerve. Overexpression of miR-125a-5p suppressed inflammation of the optic nerve, protected retinal ganglion cells, and increased the percentage of Treg cells. Our findings show that miR-125a-5p exhibits anti-inflammatory effects through promoting the differentiation of Treg cells.

Assessment of Basic Biological Functions Exerted by miRNAs

To evaluate basic miRNA function, it is vital to assess various cellular processes, such as cell viability and proliferation, under different miRNA levels. Here we describe the process of overexpression of miRNA in vitro via transfection and subsequent downstream evaluation using the acid phosphatase assay.

Evaluation of miRNA Expression in 3D In Vitro Scaffold-Based Cancer Models

Accumulating experimental evidence suggests that 3D in vitro cancer models strengthen our understanding of vital processes in the tumor microenvironment (TME) and accelerate the drug discovery pipeline. Previous studies examining the effects of specific miRNAs on cancer cells in vitro have involved ectopic expression of miRNA mimics in 2D in vitro culture. Assessment of cell viability and gene expression ensures that upregulation of the chosen miRNA and repression of its target genes have been achieved. However, this 2D culture is overly simplified and lacks the complex cell to extracellular matrix (ECM) interactions observed in the native TME, yielding results often not reproduced when progressed to in vivo studies. Hence, this chapter describes a novel method of overexpressing the miRNA mimic in cells cultured on 3D collagen-based scaffolds adapted from tissue engineering techniques. Cell growth on scaffolds is sequentially monitored via a DNA quantification assay, and overexpression of the miRNA mimic and repression of its target gene is assessed via reverse transcription quantitative PCR (RT-qPCR).

MAD2B Blunts Chronic Unpredictable Stress and Corticosterone Stimulation-Induced Depression-Like Behaviors in Mice

BACKGROUND

Depression is a prevalent and recurrent psychiatric disorder. Aberrant neural structure and activity play fundamental roles in the occurrence of depression. Mitotic arrest deficient protein (MAD2B) is highly expressed in neurons and may be implicated in synaptic plasticity in the central nervous system. However, the effect of MAD2B in depression, as well as the related molecular mechanism, is uncertain.

METHODS

Here, we employed mouse models of depression induced by chronic unpredictable stress exposure or corticosterone (CORT) stimulation. Depression-like behaviors in mice were evaluated by sucrose preference, forced swimming, and tail suspension tests. Hippocampal MAD2B overexpression was mediated by adeno-associated virus 8 containing enhanced green fluorescent protein. In vitro primary neuronal cells were obtained from the hippocampus of rat embryos and were treated with CORT, and MAD2B overexpression was performed using lentivirus. MAD2B and glutamate metabotropic receptor 4 (GRM4) levels were evaluated by western blots and quantitative PCR. Primary neuronal miR-29b-3p expression was detected by quantitative PCR.

RESULTS

MAD2B expression was reduced in the hippocampus in mice exhibiting depressive-like behaviors. However, hippocampal MAD2B overexpression protected mice from developing either chronic unpredictable stress- or CORT-induced depression-like behaviors, an effect associated with reduced expression of GRM4, a presynaptic receptor involved in depression. Moreover, MAD2B overexpression in primary neuronal cells also decreased GRM4 expression while enhancing the level of miR-29b-3p; this phenomenon was also observed under CORT stimulation.

CONCLUSIONS

Our results suggest an important role of neuronal MAD2B in the pathogenesis of depression via the miR-29b-3p/GRM4 signaling pathway. MAD2B could be a potential therapeutic target for depressive disorders.

Sex-specific roles of hippocampal microRNAs in stress vulnerability and resilience

Contrary to intuition, most individuals are resilient to psychological trauma and only a minority is vulnerable. Men and women are known to respond differently to trauma exposure, however, mechanisms underlying the relationship between sex differences and trauma resilience and vulnerability are not yet fully understood. Taking advantage of the Behavioral Profiling approach, which enables differentiating between 'affected' and 'unaffected' individuals, we examined sex-associated differences in stress exposure effects on hippocampal expression of selected stress-related GABA-A receptor targeting miRNAs. Levels of the miRNA-144 and miRNA-33 were measured in male and female affected (vulnerable, e.g., higher freezing time) and unaffected (resilient) rats. In male rats, increased levels of miRNA-144 and miRNA-33 were observed in the dorsal dentate gyrus (dDG) and ventral dentate gyrus (vDG) respectively, of stress-exposed but unaffected animals. In females, we observed an increased expression of miRNA-144 and miRNA-33 in the ventral cornu ammonis 1 (vCA1) of affected animals. Accordingly, we inhibited miRNAs expression selectively in hippocampal subregions using oligonucleotides containing locked nucleic acid bases, to examine the miRNAs' causal contribution to either vulnerability or resilience to stress in each sex. Inhibition of miRNA-144 in dDG and miRNA-33 in vDG in males resulted in an increased prevalence of vulnerable animals, while inhibition of miRNA-144 and miRNA-33 in vCA1 in females increased the proportion of resilient animals. The current findings reveal a critical sex-associated difference in the role of miRNAs in stress vulnerability and resilience. This novel understanding of sex-associated epigenetic involvement in the mechanism of stress-related psychopathologies may help improve gender-specific diagnosis and effective treatment.

Therapeutic Implications of microRNAs in Depressive Disorders: A Review

MicroRNAs are hidden players in complex psychophysical phenomena such as depression and anxiety related disorders though the activation and deactivation of multiple proteins in signaling cascades. Depression is classified as a mood disorder and described as feelings of sadness, loss, or anger that interfere with a person’s everyday activities. In this review, we have focused on exploration of the significant role of miRNAs in depression by affecting associated target proteins (cellular and synaptic) and their signaling pathways which can be controlled by the attachment of miRNAs at transcriptional and translational levels. Moreover, miRNAs have potential role as biomarkers and may help to cure depression through involvement and interactions with multiple pharmacological and physiological therapies. Taken together, miRNAs might be considered as promising novel therapy targets themselves and may interfere with currently available antidepressant treatments.

Blood miR-144-3p: a novel diagnostic and therapeutic tool for depression

Major depressive disorder (MDD) is the leading cause of disability worldwide. There is an urgent need for objective biomarkers to diagnose this highly heterogeneous syndrome, assign treatment, and evaluate treatment response and prognosis. MicroRNAs (miRNAs) are short non-coding RNAs, which are detected in body fluids that have emerged as potential biomarkers of many disease conditions. The present study explored the potential use of miRNAs as biomarkers for MDD and its treatment. We profiled the expression levels of circulating blood miRNAs from mice that were collected before and after exposure to chronic social defeat stress (CSDS), an extensively validated mouse model used to study depression, as well as after either repeated imipramine or single-dose ketamine treatment. We observed robust differences in blood miRNA signatures between stress-resilient and stress-susceptible mice after an incubation period, but not immediately after exposure to the stress. Furthermore, ketamine treatment was more effective than imipramine at re-establishing baseline miRNA expression levels, but only in mice that responded behaviorally to the drug. We identified the red blood cell-specific miR-144-3p as a candidate biomarker to aid depression diagnosis and predict ketamine treatment response in stress-susceptible mice and MDD patients. Lastly, we demonstrate that systemic knockdown of miR-144-3p, via subcutaneous administration of a specific antagomir, is sufficient to reduce the depression-related phenotype in stress-susceptible mice. RNA-sequencing analysis of blood after such miR-144-3p knockdown revealed a blunted transcriptional stress signature as well. These findings identify miR-144-3p as a novel target for diagnosis of MDD as well as for antidepressant treatment, and enhance our understanding of epigenetic processes associated with depression.

microRNA Biology on Brain Development and Neuroimaging Approach

Proper brain development requires the precise coordination and orchestration of various molecular and cellular processes and dysregulation of these processes can lead to neurological diseases. In the past decades, post-transcriptional regulation of gene expression has been shown to contribute to various aspects of brain development and function in the central nervous system. MicroRNAs (miRNAs), short non-coding RNAs, are emerging as crucial players in post-transcriptional gene regulation in a variety of tissues, such as the nervous system. In recent years, miRNAs have been implicated in multiple aspects of brain development, including neurogenesis, migration, axon and dendrite formation, and synaptogenesis. Moreover, altered expression and dysregulation of miRNAs have been linked to neurodevelopmental and psychiatric disorders. Magnetic resonance imaging (MRI) is a powerful imaging technology to obtain high-quality, detailed structural and functional information from the brains of human and animal models in a non-invasive manner. Because the spatial expression patterns of miRNAs in the brain, unlike those of DNA and RNA, remain largely unknown, a whole-brain imaging approach using MRI may be useful in revealing biological and pathological information about the brain affected by miRNAs. In this review, we highlight recent advancements in the research of miRNA-mediated modulation of neuronal processes that are important for brain development and their involvement in disease pathogenesis. Also, we overview each MRI technique, and its technological considerations, and discuss the applications of MRI techniques in miRNA research. This review aims to link miRNA biological study with MRI analytical technology and deepen our understanding of how miRNAs impact brain development and pathology of neurological diseases.

Role of MicroRNAs, Aptamers in Neuroinflammation and Neurodegenerative Disorders

Exploring the microRNAs and aptamers for their therapeutic role as biological drugs has expanded the horizon of its applicability against various human diseases, explicitly targeting the genetic materials. RNA-based therapeutics are widely being explored for the treatment and diagnosis of multiple diseases, including neurodegenerative disorders (NDD). Latter includes microRNA, aptamers, ribozymes, and small interfering RNAs (siRNAs), which control the gene expression mainly at the transcriptional strata. One RNA transcript translates into different protein types; hence, therapies targeted at the transcriptional sphere may have prominent and more extensive effects than alternative therapeutics. Unlike conventional gene therapy, RNAs, upon delivery, can either altogether abolish or alter the synthesis of the protein of interest, therefore, regulating their activities in a controlled and diverse manner. NDDs like Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, Prion disease, and others are characterized by deposition of misfolded protein such as amyloid-ß, tau, α-synuclein, huntingtin and prion proteins. Neuroinflammation, one of the perquisites for neurodegeneration, is induced during neurodegenerative pathogenesis. In this review, we discuss microRNAs and aptamers' role as two different RNA-based approaches for their unique ability to regulate protein production at the transcription level, hence offering many advantages over other biologicals. The microRNA acts either by alleviating the malfunctioning RNA expression or by working as a replacement to lost microRNA. On the contrary, aptamer act as a chemical antibody and forms an aptamer-target complex.

Molecular changes in nucleus accumbens due to amelioration of depressive-like behavior by housing with companion

Social support are positively and causally related to mental health. Higher levels of perceived social support and group memberships are shown to be associated with lower depression symptomatology and recovery from depression, but the molecular biological mechanism behind its remains largely unknown. Here, we report that accompanying with companion ameliorated chronic unpredictable mild stress (CUMS) induced depression-like behaviors in mice. Accompanying with companion altered RNA expression profiles of nucleus accumbens (NAc) in CUMS-induced susceptible and resilience mice. 117 differentially expressed genes (DEGs) were found to be associated with depression-like behaviors, 17 DEGs associated with resilient behaviors, 43 DEGs associated with accompanying with companion. Importantly, 234 differentially expressed miRNAs that associated with accompanying with companion were obtained, and the miRNA-mRNA network associated with companion was established in NAc, based on the miRNA and mRNA profiles. Taken together, our findings revealed a potential new approach to improve depression-like behaviors, as well as many potential drug targets for the prevention or treatment of depression.

MicroRNAs in Learning and Memory and Their Impact on Alzheimer’s Disease

Learning and memory formation rely on the precise spatiotemporal regulation of gene expression, such as microRNA (miRNA)-associated silencing, to fine-tune gene expression for the induction and maintenance of synaptic plasticity. Much progress has been made in presenting direct evidence of miRNA regulation in learning and memory. Here, we summarize studies that have manipulated miRNA expression using various approaches in rodents, with changes in cognitive performance. Some of these are involved in well-known mechanisms, such as the CREB-dependent signaling pathway, and some of their roles are in fear- and stress-related disorders, particularly cognitive impairment. We also summarize extensive studies on miRNAs correlated with pathogenic tau and amyloid-β that drive the processes of Alzheimer’s disease (AD). Although altered miRNA profiles in human patients with AD and in mouse models have been well studied, little is known about their clinical applications and therapeutics. Studies on miRNAs as biomarkers still show inconsistencies, and more challenges need to be confronted in standardizing blood-based biomarkers for use in AD.

Region-specific microRNA alterations in marmosets carrying SLC6A4 polymorphisms are associated with anxiety-like behavior

BACKGROUND

Psychiatric diseases such as depression and anxiety are multifactorial conditions, highly prevalent in western societies. Human studies have identified a number of high-risk genetic variants for these diseases. Among them, polymorphisms in the promoter region of the serotonin transporter gene (SLC6A4) have attracted much attention. However, due to the paucity of experimental models, molecular alterations induced by these genetic variants and how they correlate to behavioral deficits have not been examined. In this regard, marmosets have emerged as a powerful model in translational neuroscience to investigate molecular underpinnings of complex behaviors.

METHODS

Here, we took advantage of naturally occurring genetic polymorphisms in marmoset SLC6A4 gene that have been linked to anxiety-like behaviors. Using FACS-sorting, we profiled microRNA contents in different brain regions of genotyped and behaviorally-phenotyped marmosets.

FINDINGS

We revealed that marmosets bearing different SLC6A4 variants exhibit distinct microRNAs signatures in a region of the prefrontal cortex whose activity has been consistently altered in patients with depression/anxiety. We also identified Deleted in Colorectal Cancer (DCC), a gene previously linked to these diseases, as a downstream target of the differently expressed microRNAs. Significantly, we showed that levels of both microRNAs and DCC in this region were highly correlated to anxiety-like behaviors.

INTERPRETATION

Our findings establish links between genetic variants, molecular modifications in specific cortical regions and complex behavioral responses, providing new insights into gene-behavior relationships underlying human psychopathology.

FUNDING

This work was supported by France National Agency, NRJ Foundation, Celphedia and Fondation de France as well as the Wellcome Trust.

miR-218: A Stress-Responsive Epigenetic Modifier

Understanding the epigenetic role of microRNAs (miRNAs) has been a critical development in the field of neuropsychiatry and in understanding their underlying pathophysiology. Abnormalities in miRNA expression are often seen as key to the pathogenesis of many stress-associated mental disorders, including major depressive disorder (MDD). Recent advances in omics biology have further contributed to this understanding and expanded the role of miRNAs in networking a diverse array of molecular pathways, which are essentially related to the stress adaptivity of a healthy brain. Studies have highlighted the role of many such miRNAs in causing maladaptive changes in the brain's stress axis. One such miRNA is miR-218, which is debated as a critical candidate for increased stress susceptibility. miR-218 is expressed throughout the brain, notably in the hippocampus and prefrontal cortex (PFC). It is expressed at various levels through life stages, as seen by adolescent and adult animal models. Until now, a minimal number of studies have been conducted on human subjects to understand its role in stress-related abnormalities in brain circuits. However, several studies, including animal and cell-culture models, have been used to understand the impact of miR-218 on stress response and hypothalamic-pituitary-adrenal (HPA) axis function. So far, expression changes in this miRNA have been found to regulate signaling pathways such as glucocorticoid signaling, serotonergic signaling, and glutamatergic signaling. Recently, the developmental role of miR-218 has generated interest, given its increasing expression from adolescence to adulthood and targeting the Netrin-1/DCC signaling pathway. Since miR-218 expression affects neuronal development and plasticity, it is expected that a change in miR-218 expression levels over the course of development may negatively impact the process and make individuals stress-susceptible in adulthood. In this review, we describe the role of miR-218 in stress-induced neuropsychiatric conditions with an emphasis on stress-related disorders.

Signalling pathways in autism spectrum disorder: mechanisms and therapeutic implications

Autism spectrum disorder (ASD) is a prevalent and complex neurodevelopmental disorder which has strong genetic basis. Despite the rapidly rising incidence of autism, little is known about its aetiology, risk factors, and disease progression. There are currently neither validated biomarkers for diagnostic screening nor specific medication for autism. Over the last two decades, there have been remarkable advances in genetics, with hundreds of genes identified and validated as being associated with a high risk for autism. The convergence of neuroscience methods is becoming more widely recognized for its significance in elucidating the pathological mechanisms of autism. Efforts have been devoted to exploring the behavioural functions, key pathological mechanisms and potential treatments of autism. Here, as we highlight in this review, emerging evidence shows that signal transduction molecular events are involved in pathological processes such as transcription, translation, synaptic transmission, epigenetics and immunoinflammatory responses. This involvement has important implications for the discovery of precise molecular targets for autism. Moreover, we review recent insights into the mechanisms and clinical implications of signal transduction in autism from molecular, cellular, neural circuit, and neurobehavioural aspects. Finally, the challenges and future perspectives are discussed with regard to novel strategies predicated on the biological features of autism.

Circulating miRNAs as Potential Biomarkers for Patient Stratification in Bipolar Disorder: A Combined Review and Data Mining Approach

Bipolar disorder is a debilitating psychiatric condition that is shaped in a concerted interplay between hereditary and triggering risk factors. Profound depression and mania define the disorder, but high clinical heterogeneity among patients complicates diagnosis as well as pharmacological intervention. Identification of peripheral biomarkers that capture the genomic response to the exposome may thus progress the development of personalized treatment. MicroRNAs (miRNAs) play a prominent role in of post-transcriptional gene regulation in the context of brain development and mental health. They are coordinately modulated by multifarious effectors, and alteration in their expression profile has been reported in a variety of psychiatric conditions. Intriguingly, miRNAs can be released from CNS cells and enter circulatory bio-fluids where they remain remarkably stable. Hence, peripheral circulatory miRNAs may act as bio-indicators for the combination of genetic risk, environmental exposure, and/or treatment response. Here we provide a comprehensive literature search and data mining approach that summarize current experimental evidence supporting the applicability of miRNAs for patient stratification in bipolar disorder.

Three-in-One System Based on Multi-Path Nucleic Acid Amplification for Bioanalysis of Pre-miRNA/miRNA and Dicer Activity

Today, a lot of attention is being paid to the pre-miRNAs/miRNAs or activity of Dicer due to their important functions in various physiological processes. Especially, the intrinsic relationship among these associated targets is of significant importance for more in-depth research on the mechanism of disease formation and early diagnosis. Herein, a strategy for simultaneous bioanalysis of miRNAs/pre-miRNAs and Dicer enzyme based on the self-designed multi-path nucleic acid amplification technology was proposed. Typically, in the presence of pre-miRNA-155, it can hybridize with Helper to generate a structure with two new toeholds, one of which could react with H1, H2, and H3, performing a modified CHA reaction with obvious fluorescence responses of FAM, and another of which could hybridize with H4, H5, and H6 to construct the [H4-H5-H6]_n DNA nanosphere with obvious fluorescence responses of Cy5. Similarly, miRNA-155 could just hybridize with H1, H2, and H3 to generate the same modified CHA reaction with obvious fluorescence responses of FAM. Due to the successful multi-path nucleic acid amplification, the proposed bioanalysis strategy could be successfully employed for miRNA-155 and pre-miRNA-155 analysis in the range from 500 pM to 100 nM and 1 to 300 nM, respectively. The proposed strategy could be applied to explore another inter-related nucleic acid relationship also, providing great potential in bioanalysis of various nucleic acids.

EpisomiR, a New Family of miRNAs, and Its Possible Roles in Human Diseases

MicroRNAs (miRNAs) are synthesized through a canonical pathway and play a role in human diseases, such as cancers and cardiovascular, neurodegenerative, psychiatric, and chronic inflammatory diseases. The development of sequencing technologies has enabled the identification of variations in noncoding miRNAs. These miRNA variants, called isomiRs, are generated through a non-canonical pathway, by several enzymes that alter the length and sequence of miRNAs. The isomiR family is, now, expanding further to include episomiRs, which are miRNAs with different modifications. Since recent findings have shown that isomiRs reflect the cell-specific biological function of miRNAs, knowledge about episomiRs and isomiRs can, possibly, contribute to the optimization of diagnosis and therapeutic technology for precision medicine.

TINY IN SIZE, BIG IN IMPACT: EXTRACELLULAR VESICLES AS MODULATORS OF MOOD, ANXIETY AND NEURODEVELOPMENTAL DISORDERS

Extracellular Vesicles (EVs) are tiny vesicles used by cells as means of cellular communication, through which the function and state of a given cell can be changed. A body of evidence has suggested that EVs could be culprits in the development and progression of various types of diseases, including neurodegenerative diseases such as Multiple Sclerosis (MS) and Alzheimer's Disease (AD). Unsurprisingly, EVs have also been implicate in mood, anxiety and neurodevelopmental disorders, such as Major Depressive Disorder (MDD), anxiety disorder and Autism-Spectrum Disorder (ASD), respectively. Here, we review the state-of-art regarding the roles of EVs in the aforementioned diseases and focus on the mechanisms by which they can cause and worsen disease. Harnessing the knowledge of EVs is not only important to deliver different cargos to cells in a specific manner to treat these diseases, but also to establish reliable disease biomarkers, which will aid in the early disease diagnosis and treatment, increasing the chance of successful treatment.

Transcriptional biomarkers of response to pharmacological treatments in severe mental disorders: A systematic review

Variation in the expression level and activity of genes involved in drug disposition and action in tissues of pharmacological importance have been increasingly investigated in patients treated with psychotropic drugs. Findings are promising, but reliable predictive biomarkers of response have yet to be identified. Here we conducted a PRISMA-compliant systematic search of PubMed, Scopus and PsycInfo up to 12 September 2020 for studies investigating RNA expression levels in cells or biofluids from patients with major depressive disorder, schizophrenia or bipolar disorder characterized for response to psychotropic drugs (antidepressants, antipsychotics or mood stabilizers) or adverse effects. Among 5497 retrieved studies, 123 (63 on antidepressants, 33 on antipsychotics and 27 on mood stabilizers) met inclusion criteria. Studies were either focused on mRNAs (n = 96), microRNAs (n = 19) or long non-coding RNAs (n = 1), with only a minority investigating both mRNAs and microRNAs levels (n = 7). The most replicated results include genes playing a role in inflammation (antidepressants), neurotransmission (antidepressants and antipsychotics) or mitochondrial function (mood stabilizers). Compared to those investigating response to antidepressants, studies focused on antipsychotics or mood stabilizers more often showed lower sample size and lacked replication. Strengths and limitations of available studies are presented and discussed in light of the specific designs, methodology and clinical characterization of included patients for transcriptomic compared to DNA-based studies. Finally, future directions of transcriptomics of psychopharmacological interventions in psychiatric disorders are discussed.