MicroRNAs as biomarkers for CNS disease

Circulating RNAs as Potential Biomarkers in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex multi-system neurodegenerative disorder with currently limited diagnostic and no therapeutic options. Despite the intense efforts no clinically applicable biomarkers for ALS are yet established. Most current research is thus focused, in particular, in identifying potential non-invasive circulating biomarkers for more rapid and accurate diagnosis and monitoring of the disease. In this review, we have focused on messenger RNA (mRNA), non-coding RNAs (lncRNAs), micro RNAs (miRNAs) and circular RNA (circRNAs) as potential biomarkers for ALS in peripheral blood serum, plasma and cells. The most promising miRNAs include miR-206, miR-133b, miR-27a, mi-338-3p, miR-183, miR-451, let-7 and miR-125b. To test clinical potential of this miRNA panel, a useful approach may be to perform such analysis on larger multi-center scale using similar experimental design. However, other types of RNAs (lncRNAs, circRNAs and mRNAs) that, together with miRNAs, represent RNA networks, have not been yet extensively studied in blood samples of patients with ALS. Additional research has to be done in order to find robust circulating biomarkers and therapeutic targets that will distinguish key RNA interactions in specific ALS-types to facilitate diagnosis, predict progression and design therapy.

miR-101, miR-548b, miR-554, and miR-1202 are reliable prognosis predictors of the miRNAs associated with cancer immunity in primary central nervous system lymphoma

MicroRNAs (miRNAs) inhibit protein function by silencing the translation of target mRNAs. However, in primary central nervous system lymphoma (PCNSL), the expression and functions of miRNAs are inadequately known. Here, we examined the expression of 847 miRNAs in 40 PCNSL patients with a microarray and investigated for the miRNA predictors associated with cancer immunity-related genes such as T helper cell type 1/2 (Th-1/Th-2) and regulatory T cell (T-reg) status, and stimulatory and inhibitory checkpoint genes, for prognosis prediction in PCNSL. The aim of this study is to find promising prognosis markers based on the miRNA expression in PCNSL. We detected 334 miRNAs related to 66 cancer immunity-related genes in the microarray profiling. Variable importance measured by the random survival forest analysis and Cox proportional hazards regression model elucidated that 11 miRNAs successfully constitute the survival formulae dividing the Kaplan-Meier curve of the respective PCNSL subgroups. On the other hand, univariate analysis shortlisted 23 miRNAs for overall survival times, with four miRNAs clearly dividing the survival curves-miR-101/548b/554/1202. These miRNAs regulated Th-1/Th-2 status, T-reg cell status, and immune checkpoints. The miRNAs were also associated with gene ontology terms as Ras/MAP-kinase, ubiquitin ligase, PRC2 and acetylation, CDK, and phosphorylation, and several diseases including acquired immunodeficiency syndrome, glioma, and those related to blood and hippocampus with statistical significance. In conclusion, the results demonstrated that the four miRNAs comprising miR-101/548b/554/1202 associated with cancer immunity can be a useful prognostic marker in PCNSL and would help us understand target pathways for PCNSL treatments.

Modulation of NMDA receptor by miR-219 in the amygdala and hippocampus of patients with mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy with hippocampal sclerosis is the most frequent form of focal epilepsy in adults, and it is often refractory to drug treatment. Regardless of the efforts on developing new antiepileptic drugs for refractory cases, studies suggest a need for better understanding the molecular bases of epilepsy. The microRNAs have been progressively investigated as potential targets for both epilepsy mechanisms elucidation and treatment. Therefore, the goal of this study was to evaluate the differential expression of miR-219, miR-181b, and miR-195, previously described as regulators of the excitatory neurotransmitter receptors NMDA-R1 and AMPA-GluR2 and inhibitory neurotransmitter GABA_A (α2, β3, and γ2 subunits) in the amygdala and hippocampus of patients with mesial temporal lobe epilepsy. Based on genes and miRNAs' quantitative Polymerase Chain Reaction (qPCR) from 18 patients with epilepsy, our results showed an inverse relationship between miR-219 and NMDA-NR1 expression in both the amygdala and hippocampus in comparison to their expression in controls. NR1 and GluR2 were upregulated in the amygdala of epileptic patients. Low miR-195 expression was observed in the amygdala of patients with epilepsy. Our findings indicate that miR-219 has a possible regulatory role in excitatory neurotransmission in patients with epilepsy, contributing to the new avenue of miRNA biology in drug-resistant epilepsy, reserving huge potential for future applications and clinical interventions in conjunction with existing therapies.

The Relationship between DNA Methylation and Antidepressant Medications: A Systematic Review

Major depressive disorder (MDD) is the leading cause of disability worldwide and is associated with high rates of suicide and medical comorbidities. Current antidepressant medications are suboptimal, as most MDD patients fail to achieve complete remission from symptoms. At present, clinicians are unable to predict which antidepressant is most effective for a particular patient, exposing patients to multiple medication trials and side effects. Since MDD’s etiology includes interactions between genes and environment, the epigenome is of interest for predictive utility and treatment monitoring. Epigenetic mechanisms of antidepressant medications are incompletely understood. Differences in epigenetic profiles may impact treatment response. A systematic literature search yielded 24 studies reporting the interaction between antidepressants and eight genes (BDNF, MAOA, SLC6A2, SLC6A4, HTR1A, HTR1B, IL6, IL11) and whole genome methylation. Methylation of certain sites within BDNF, SLC6A4, HTR1A, HTR1B, IL11, and the whole genome was predictive of antidepressant response. Comparing DNA methylation in patients during depressive episodes, during treatment, in remission, and after antidepressant cessation would help clarify the influence of antidepressant medications on DNA methylation. Individuals’ unique methylation profiles may be used clinically for personalization of antidepressant choice in the future.

Extracellular vesicles in the diagnosis and treatment of central nervous system diseases

Extracellular vesicles, including exosomes and microvesicles, play a fundamental role in the activity of the nervous system, participating in signal transmission between neurons and providing the interaction of central nervous system with all body systems. In many neurodegenerative diseases, neurons pack toxic substances into vesicles and release them into the extracellular space, which leads to the spread of misfolded neurotoxic proteins. The contents of neuron-derived extracellular vesicles may indicate pathological changes in the central nervous system, and the analysis of extracellular vesicle molecular content contributes to the development of non-invasive methods for the diagnosis of many central nervous system diseases. Extracellular vesicles of neuronal origin can be isolated from various biological fluids due to their ability to cross the blood-brain barrier. Today, the diagnostic potential of almost all toxic proteins involved in nervous system disease pathogenesis, specifically α-synuclein, tau protein, superoxide dismutase 1, FUS, leucine-rich repeat kinase 2, as well as some synaptic proteins, has been well evidenced. Special attention is paid to extracellular RNAs mostly associated with extracellular vesicles, which are important in the onset and development of many neurodegenerative diseases. Depending on parental cell type, extracellular vesicles may have different therapeutic properties, including neuroprotective, regenerative, and anti-inflammatory. Due to nano size, biosafety, ability to cross the blood-brain barrier, possibility of targeted delivery and the lack of an immune response, extracellular vesicles are a promising vehicle for the delivery of therapeutic substances for the treatment of neurodegenerative diseases and drug delivery to the brain. This review describes modern approaches of diagnosis and treatment of central nervous system diseases using extracellular vesicles.

Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown

Progesterone has been shown to exert a wide range of remarkable protective actions in experimental models of central nervous system injury or disease. However, the intimate mechanisms involved in each of these beneficial effects are not fully depicted. In this review, we intend to give the readers a thorough revision on what is known about the participation of diverse receptors and signaling pathways in progesterone-mediated neuroprotective, pro-myelinating and anti-inflammatory outcomes, as well as point out to novel regulatory mechanisms that could open new perspectives in steroid-based therapies.

Circulating microRNAs as potential biomarkers for genetic generalized epilepsies: a three microRNA panel

BACKGROUND AND PURPOSE

Genetic generalized epilepsies (GGEs) encompass a group of syndromes of mainly genetic causes, characterized by the involvement of both hemispheres. MicroRNAs (miRNAs) are small non-coding RNAs with a critical role in the regulation of neuronal biological processes through gene expression modulation. Dysregulated miRNA expression has been shown in epilepsy. Due to their stability in biological fluids like serum, miRNAs have assumed a prominent role in biomarker research. Our aim was to evaluate circulating levels of three miRNAs in GGE patients and assess their putative diagnostic value.

METHODS

MiR-146a, miR-155 and miR-132 were quantified by real-time polymerase chain reaction in the serum of 79 GGE patients (47 women, 32 men, 35.1 ± 12.4 years) and 67 healthy individuals (41 women, 26 men, 42.4 ± 10.1 years). Relative expression values were calculated using the 2^-ΔΔCt method. Receiver operating characteristic curve analysis was performed to assess diagnostic value. MiRNA expression was correlated with clinicopathological features.

RESULTS

Serum levels of miR-146a and miR-155 were significantly upregulated in GGE patients relative to controls (3.13 and 6.05, respectively). Combined miR-146a, miR-155 and miR-132 serum levels performed well as a diagnostic biomarker, discriminating GGE patients from controls with an area under the curve of 0.85, 80% specificity and 73% sensitivity.

CONCLUSIONS

Our results indicate that miR-146a, miR-155 and miR-132 may partake in GGE epileptogenesis. A panel of three circulating miRNAs with potential value as a GGE biomarker is reported for the first time. Novel biomarkers may help to identify new treatment targets and contribute to improved patients' quality of life through earlier diagnosis and a more precise prognosis.

Exosomal miRNAs in central nervous system diseases: biomarkers, pathological mediators, protective factors and therapeutic agents

Exosomes are small bilipid layer-enclosed extracellular vesicles that can be found in tissues and biological fluids. As a key cell-to-cell and distant communication mediator, exosomes are involved in various central nervous system (CNS) diseases, potentially through transferring their contents such as proteins, lipids and nucleic acids to the target cells. Exosomal miRNAs, which are small non-coding RNAs in the exosomes, are known to be more stable than free miRNAs and therefore have lasting effects on disease-related gene expressions. There are distinct profiles of exosomal miRNAs in different types of CNS diseases even before the onset of irreversible neurological damages, indicating that exosomal miRNAs within tissues and biological fluids could serve as promising biomarkers. Emerging evidence has also demonstrated the pathological effects of several exosomal miRNAs in CNS diseases via specific modulation of disease-related factors. Moreover, exosomes carry therapeutically beneficial miRNAs across the blood-brain-barrier, which can be exploited as a powerful drug delivery tool to help alleviating multiple CNS diseases. In this review, we summarize the recent progress made in understanding the biological roles of exosomal miRNAs as potential diagnostic biomarkers, pathological regulators, and therapeutic targets/drugs for CNS diseases. A comprehensive discussion of the main concerns and challenges for the applications of exosomal miRNAs in the clinical setting is also provided.

Enrichment of Exosome-Like Extracellular Vesicles from Plasma Suitable for Clinical Vesicular miRNA Biomarker Research

Exosome-like extracellular vesicles (ELVs) contain biomolecules that have potential as diagnostic biomarkers, such as proteins, micro-RNAs (miRNAs), and lipids. However, it is difficult to enrich ELVs consistently with high yield and purity from clinical samples, which hampers the development of ELV biomarkers. This is particularly true for miRNAs in protein-rich plasma. Hence, we modified ELV isolation protocols of three commercially available polymer-precipitation-based kits using proteinase K (PK) treatment to quantify ELV-associated miRNAs in human plasma. We compared the yield, purity, and characteristics of enriched plasma ELVs, and measured the relative quantity of three selected miRNAs (miR-30c, miR-126, and miR-192) in ELVs using six human plasma samples. Compared with the original protocols, we demonstrated that ELVs can be isolated with PK treatment with high purity (i.e., lack of non-exosomal proteins and homogeneous size of vesicles) and yield (i.e., abundancy of exosomal markers), which were dependent on kits. Using the kit with the highest purity and yield with PK treatment, we successfully quantified ELV miRNAs (levels of 45%–65% in total plasma) with acceptable variability. Collectively, ELV enrichment using the modified easy-to-use method appears suitable for the analysis of miRNAs, although its clinical applicability needs to be confirmed in larger clinical studies.

Tumor and Cerebrospinal Fluid microRNAs in Primary Central Nervous System Lymphomas

Primary central nervous system lymphoma (PCNSL) is a rare, highly aggressive, extranodal form of non-Hodgkin lymphoma, predominantly diagnosed as primary diffuse large B-cell lymphoma of the central nervous system (CNS DLBCL). Fast and precise diagnosis of PCNSL is critical yet challenging. microRNAs, important regulators in physiology and pathology are potential biomarkers. In 131 patients with CNS DLBCL and with non-malignant brain lesions (n-ML), miR-21, miR-19b and miR-92a, miR-155, miR-196b, miR-let-7b, miR-125b, and miR-9 were examined by RT-qPCR in brain biopsy samples (formalin-fixed paraffin-embedded tissues, FFPET; CNS DLBCL, n = 52; n-ML, n = 42) and cerebrospinal fluid samples (CSF; CNS DLBCL, n = 30; n-ML, n = 23) taken for routine diagnosis. FFPET samples were split into study and validation sets. Significantly higher CSF levels of miR-21, miR-19b, and miR-92a were identified in PCNSL but not in n-ML, and differentiated PCNSL from n-ML with 63.33% sensitivity and 80.77% specificity. In FFPETs, miR-155 and miR-196b were significantly overexpressed and miR-let-7b, miR-125b, and miR-9 were downregulated in PCNSL as compared to n-ML. Combined miR-155 and miR-let-7b expression levels in FFPETs discriminated PCNSL and n-ML with a 97% accuracy. In conclusion, tissue miR-155, miR-196b, miR-9, miR-125b, and miR-let-7b expression profiles differentiate PCNSL from n-ML. PCNSL CSFs and the relevant biopsy samples are characterized by specific, different microRNA profiles. A logistic regression model is proposed to discriminate between PCNSL and non-malignant brain lesions. None of the examined microRNAs influenced overall survival of PCNSL patients. Further ongoing developments involve next generation sequencing-based profiling of biopsy and CSF samples.

Circulating Plasma microRNAs are Altered with Amyloidosis in a Mouse Model of Alzheimer's Disease

Pathological changes underlying Alzheimer's disease (AD) begin decades before the classical symptoms of memory loss become evident. As microRNAs are released from neurons and enter the bloodstream, circulating microRNAs may be reflective of AD progression and are ideal candidates as biomarkers for early-stage disease detection. Here, we provide a novel, in-depth analysis of how plasma microRNAs alter with aging, the most prominent risk factor for AD, and with development of amyloid-β (Aβ) plaque deposition. We assessed the circulating microRNAs in APPswe/PSEN1dE9 transgenic mice and wild-type controls at 4, 8 and 15 m (n = 8-10) using custom designed Taqman arrays representing 185 neuropathology-related microRNAs. We performed a linear mixed-effects model to investigate the effects of age and genotype on plasma microRNAs expression. Following this analysis, we found 8 microRNAs were significantly affected by age alone in wild-type animals and 12 microRNAs altered in APPswe/PSEN1dE9 mice, either prior to Aβ plaque deposition (4 m) or during the development of AD-like pathogenesis (8 m or 15 m). Importantly, we found that differing sets of microRNAs were identified at each time point. Functional analysis of these data revealed that while common biological pathways, such as Inflammatory Response, were enriched throughout the disease process, Free Radical Scavenging, Immunological Disease, and Apoptosis Signaling were specifically enriched later in the disease process. Overall, this study reinforces that distinct biological processes underpin the early versus late stages of AD-like pathogenesis and highlights potential pre-symptomatic microRNAs biomarkers of neurodegeneration.

A combined miRNA-piRNA signature to detect Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder causing huge emotional and economic burden to our societies. An effective therapy has not been implicated yet, which is in part also due to the fact that pathological changes occur years before clinical symptoms manifest. Thus, there is a great need for the development of a translatable biomarker. Recent evidence highlights microRNAs as candidate biomarkers. In this study, we use next-generation sequencing to study the small noncoding RNAome (sncRNAome) in exosomes derived from human cerebrospinal fluid (CSF). We show that the sncRNAome from CSF-derived exosomes is dominated not only by microRNAs (miRNAs) but also by PIWI-interacting RNAs (piRNAs). We define a combined signature consisting of three miRNAs and three piRNAs that are suitable to detect AD with an AUC of 0.83 in a replication cohort and furthermore predict the conversion of mild-cognitive impaired (MCI) patients to AD dementia with an AUC of 0.86 for the piRNA signature. When combining the smallRNA signature with pTau and Aβ 42/40 ratio the AUC reaches 0.98. Our study reports a novel exosomal small noncoding RNA signature to detect AD pathology and provides the first evidence that in addition to miRNAs, piRNAs should also be considered as a candidate biomarker for AD.

Secretomics to Discover Regulators in Diseases

Secretory proteins play important roles in the cross-talk of individual functional units, including cells. Since secretory proteins are essential for signal transduction, they are closely related with disease development, including metabolic and neural diseases. In metabolic diseases, adipokines, myokines, and hepatokines are secreted from respective organs under specific environmental conditions, and play roles in glucose homeostasis, angiogenesis, and inflammation. In neural diseases, astrocytes and microglia cells secrete cytokines and chemokines that play roles in neurotoxic and neuroprotective responses. Mass spectrometry-based secretome profiling is a powerful strategy to identify and characterize secretory proteins. This strategy involves stepwise processes such as the collection of conditioned medium (CM) containing secretome proteins and concentration of the CM, peptide preparation, mass analysis, database search, and filtering of secretory proteins; each step requires certain conditions to obtain reliable results. Proteomic analysis of extracellular vesicles has become a new research focus for understanding the additional extracellular functions of intracellular proteins. Here, we provide a review of the insights obtained from secretome analyses with regard to disease mechanisms, and highlight the future prospects of this technology. Continued research in this field is expected to provide valuable information on cell-to-cell communication and uncover new pathological mechanisms.

Whole blood microRNA expression associated with stroke: Results from the Framingham Heart Study

Emerging evidence suggests microRNAs (miRNAs) may play an important role in explaining variation in stroke risk and recovery in humans, yet there are still few longitudinal studies examining the association between whole blood miRNAs and stroke. Accounting for multiple testing and adjusting for potentially confounding technical and clinical variables, here we show that whole blood miR-574-3p expression was significantly lower in participants with chronic stroke compared to non-cases. To explore the functional relevance of our findings, we analyzed miRNA-mRNA whole blood co-expression, pathway enrichment, and brain tissue gene expression. Results suggest miR-574-3p is involved in neurometabolic and chronic neuronal injury response pathways, including brain gene expression of DBNDD2 and ELOVL1. These results suggest miR-574-3p plays a role in regulating chronic brain and systemic cellular response to stroke and thus may implicate miR-574-3p as a partial mediator of long-term stroke outcomes.

miRNAs in depression vulnerability and resilience: novel targets for preventive strategies

The exposure to stressful experiences during the prenatal period and through the first years of life is known to affect the brain developmental trajectories, leading to an enhanced vulnerability for the development of several psychiatric disorders later in life. However, not all the subjects exposed to the same stressful experience develop a pathologic condition, as some of them, activating coping strategies, become more resilient. The disclosure of mechanisms associated with stress vulnerability or resilience may allow the identification of novel biological processes and potential molecules that, if properly targeted, may prevent susceptibility or potentiate resilience. Over the last years, miRNAs have been proposed as one of the epigenetic mechanisms mediating the long-lasting effects of stress. Accordingly, they are associated with the development of stress vulnerability or resilience-related strategies. Moreover, miRNAs have been proposed as possible biomarkers able to identify subjects at high risk to develop depression and to predict the response to pharmacological treatments. In this review, we aimed to provide an overview of findings from studies in rodents and humans focused on the involvement of miRNAs in the mechanisms of stress response with the final goal to identify distinct sets of miRNAs involved in stress vulnerability or resilience. In addition, we reviewed studies on alterations of miRNAs in the context of depression, showing data on the involvement of miRNAs in the pathogenesis of the disease and in the efficacy of pharmacological treatments, discussing the potential utility of miRNAs as peripheral biomarkers able to predict the treatment response.

Identification of Candidate miRNA Biomarkers for Glaucoma

Purpose

Glaucoma, a leading cause of blindness worldwide, often remains undetected until irreversible vision loss has occurred. Treatments focus on lowering intraocular pressure (IOP), the only modifiable and readily measurable risk factor. However, IOP can vary and does not always predict disease progression. MicroRNAs (miRNAs) are promising biomarkers. They are abundant and stable in biological fluids, including plasma and aqueous humor (AqH). We aimed to identify differentially expressed miRNAs in AqH and plasma from glaucoma, exfoliation syndrome (XFS), and control subjects.

Methods

Plasma and AqH from two ethnic cohorts were harvested from glaucoma or XFS (often associated with glaucoma, n = 33) and control (n = 31) patients undergoing elective surgery. A custom miRNA array measured 372 miRNAs. Molecular target prediction and pathway analysis were performed with Ingenuity Pathway Analysis (IPA) and DIANA bioinformatical tools.

Results

Levels of miRNAs in plasma, a readily accessible biomarker source, correlated with miRNA levels in AqH. Twenty circulating miRNAs were at least 1.5-fold higher in glaucoma or XFS patients than in controls across two ethnic cohorts: miR-4667-5p (P = 4.1 × 10⁻⁵), miR-99b-3p (P = 4.8 × 10⁻⁵), miR-637 (P = 5.1 × 10⁻⁵), miR-4490 (P = 5.7 × 10⁻⁵), miR-1253 (P = 6.0 × 10⁻⁵), miR-3190-3p (P = 3.1 × 10⁻⁴), miR-3173-3p (P = 0.001), miR-608 (P = 0.001), miR-4725-3p (P = 0.002), miR-4448 (P = 0.002), and miR-323b-5p (P = 0.002), miR-4538 (P = 0.003), miR-3913-3p (P = 0.003), miR-3159 (P = 0.003), miR-4663 (P = 0.003), miR-4767 (P = 0.003), miR-4724-5p (P = 0.003), miR-1306-5p (P = 0.003), miR-181b-3p (P = 0.004), and miR-433-3p (P = 0.004). miR-637, miR-1306-5p, and miR-3159, in combination, allowed discrimination between glaucoma patients and control subjects (AUC = 0.91 ± 0.008, sensitivity 85.0%, specificity 87.5%).

Conclusions

These results identify specific miRNAs as potential biomarkers and provide insight into the molecular processes underlying glaucoma.

Biological Significance of microRNA Biomarkers in ALS-Innocent Bystanders or Disease Culprits?

MicroRNAs (miRNAs) represent potential biomarkers for neurodegenerative disorders including amyotrophic lateral sclerosis (ALS). However, whether expression changes of individual miRNAs are simply an indication of cellular dysfunction and degeneration, or actually promote functional changes in target gene expression relevant to disease pathogenesis, is unclear. Here we used bioinformatics to test the hypothesis that ALS-associated miRNAs exert their effects through targeting genes implicated in disease etiology. We documented deregulated miRNAs identified in studies of ALS patients, noting variations in participants, tissue samples, miRNA detection or quantification methods used, and functional or bioinformatic assessments (if performed). Despite lack of experimental standardization, overlap of many deregulated miRNAs between studies was noted; however, direction of reported expression changes did not always concur. The use of in silico predictions of target genes for the most commonly deregulated miRNAs, cross-referenced to a selection of previously identified ALS genes, did not support our hypothesis. Specifically, although deregulated miRNAs were predicted to commonly target ALS genes, random miRNAs gave similar predictions. To further investigate biological patterns in the deregulated miRNAs, we grouped them by tissue source in which they were identified, indicating that for a core of frequently detected miRNAs, blood/plasma/serum may be useful for future profiling experiments. We conclude that in silico predictions of gene targets of deregulated ALS miRNAs, at least using currently available algorithms, are unlikely to be sufficient in informing disease pathomechanisms. We advocate experimental functional testing of candidate miRNAs and their predicted targets, propose miRNAs to prioritise, and suggest a concerted move towards protocol standardization for biomarker identification.

MicroRNA-124 Dysregulation is Associated With Retinal Inflammation and Photoreceptor Death in the Degenerating Retina

Purpose

We sought to determine the role and retinal cellular location of microRNA-124 (miR-124) in a neuroinflammatory model of retinal degeneration. Further, we explored the anti-inflammatory relationship of miR-124 with a predicted messenger RNA (mRNA) binding partner, chemokine (C-C motif) ligand 2 (Ccl2), which is crucially involved in inflammatory cell recruitment in the damaged retina.

Methods

Human AMD donor eyes and photo-oxidative damaged (PD) mice were labeled for miR-124 expression using in situ hybridization. PDGFRa-cre RFP mice were used for Müller cell isolation from whole retinas. MIO-M1 immortalized cells and rat primary Müller cells were used for in vitro analysis of miR-124 expression and its relationship with Ccl2. Therapeutic efficacy was tested with intravitreal administration of miR-124 mimic in mice, with electroretinography used to determine retinal function. IBA1 immunohistochemistry and photoreceptor row counts were used for assessment of inflammation and cell death.

Results

MiR-124 expression was correlated with progressive retinal damage, inflammation, and cell death in human AMD and PD mice. In addition, miR-124 expression was inversely correlated to Ccl2 expression in mice following PD. MiR-124 was localized to both neuronal-like photoreceptors and glial (Müller) cells in the retina, with a redistribution from neurons to glia occurring as a consequence of PD. Finally, intravitreal administration of miR-124 mimics decreased retinal inflammation and photoreceptor cell death, and improved retinal function.

Conclusions

This study has provided an understanding of the mechanism behind miR-124 in the degenerating retina and demonstrates the usefulness of miR-124 mimics for the modulation of retinal degenerations.

Music-performance regulates microRNAs in professional musicians

Musical training and performance require precise integration of multisensory and motor centres of the human brain and can be regarded as an epigenetic modifier of brain functions. Numerous studies have identified structural and functional differences between the brains of musicians and non-musicians and superior cognitive functions in musicians. Recently, music-listening and performance has also been shown to affect the regulation of several genes, many of which were identified in songbird singing. MicroRNAs affect gene regulation and studying their expression may give new insights into the epigenetic effect of music. Here, we studied the effect of 2 hours of classical music-performance on the peripheral blood microRNA expressions in professional musicians with respect to a control activity without music for the same duration. As detecting transcriptomic changes in the functional human brain remains a challenge for geneticists, we used peripheral blood to study music-performance induced microRNA changes and interpreted the results in terms of potential effects on brain function, based on the current knowledge about the microRNA function in blood and brain. We identified significant (FDR <0.05) up-regulation of five microRNAs; hsa-miR-3909, hsa-miR-30d-5p, hsa-miR-92a-3p, hsa-miR-222-3p and hsa-miR-30a-5p; and down-regulation of two microRNAs; hsa-miR-6803-3p and hsa-miR-1249-3p. hsa-miR-222-3p and hsa-miR-92a-3p putatively target FOXP2, which was found down-regulated by microRNA regulation in songbird singing. miR-30d and miR-222 corroborate microRNA response observed in zebra finch song-listening/learning. miR-222 is induced by ERK cascade, which is important for memory formation, motor neuron functions and neuronal plasticity. miR-222 is also activated by FOSL1, an immediate early gene from the FOS family of transcriptional regulators which are activated by auditory-motor stimuli. miR-222 and miR-92 promote neurite outgrowth by negatively regulating the neuronal growth inhibitor, PTEN, and by activating CREB expression and phosphorylation. The up-regulation of microRNAs previously found to be regulators of auditory and nervous system functions (miR-30d, miR-92a and miR-222) is indicative of the sensory perception processes associated with music-performance. Akt signalling pathway which has roles in cell survival, cell differentiation, activation of CREB signalling and dopamine transmission was one of the functions regulated by the up-regulated microRNAs; in accordance with functions identified from songbird learning. The up-regulated microRNAs were also found to be regulators of apoptosis, suggesting repression of apoptotic mechanisms in connection with music-performance. Furthermore, comparative analyses of the target genes of differentially expressed microRNAs with that of the song-responsive microRNAs in songbirds suggest convergent regulatory mechanisms underlying auditory perception.

Emerging Roles of miRNAs in Brain Development and Perinatal Brain Injury

In human beings the immature brain is highly plastic and depending on the stage of gestation is particularly vulnerable to a range of insults that if sufficiently severe, can result in long-term motor, cognitive and behavioral impairment. With improved neonatal care, the incidence of major motor deficits such as cerebral palsy has declined with prematurity. Unfortunately, however, milder forms of injury characterized by diffuse non-cystic white matter lesions within the periventricular region and surrounding white matter, involving loss of oligodendrocyte progenitors and subsequent axonal hypomyelination as the brain matures have not. Existing therapeutic options for treatment of preterm infants have proved inadequate, partly owing to an incomplete understanding of underlying post-injury cellular and molecular changes that lead to poor neurodevelopmental outcomes. This has reinforced the need to improve our understanding of brain plasticity, explore novel solutions for the development of protective strategies, and identify biomarkers. Compelling evidence exists supporting the involvement of microRNAs (miRNAs), a class of small non-coding RNAs, as important post-transcriptional regulators of gene expression with functions including cell fate specification and plasticity of synaptic connections. Importantly, miRNAs are differentially expressed following brain injury, and can be packaged within exosomes/extracellular vesicles, which play a pivotal role in assuring their intercellular communication and passage across the blood-brain barrier. Indeed, an increasing number of investigations have examined the roles of specific miRNAs following injury and regeneration and it is apparent that this field of research could potentially identify protective therapeutic strategies to ameliorate perinatal brain injury. In this review, we discuss the most recent findings of some important miRNAs in relation to the development of the brain, their dysregulation, functions and regulatory roles following brain injury, and discuss how these can be targeted either as biomarkers of injury or neuroprotective agents.

MicroRNA signature constituted of miR-30d, miR-93, and miR-181b is a promising prognostic marker in primary central nervous system lymphoma

MicroRNAs (miRNAs) are small RNA molecules that inhibit gene function by suppressing translation of target genes. However, in primary central nervous system lymphoma (PCNSL), the biological significance of miRNAs is largely unknown, although some miRNAs are known to be prognosis markers. Here, we analyzed 847 miRNAs expressed in 27 PCNSL specimens using microarray profiling and surveyed miRNA signature for prognostic prediction. Of these, 16 miRNAs were expressed in 27 PCNSL specimens at a frequency of 48%. Their variable importance measured by Random forest model revealed miR-192, miR-486, miR-28, miR-52, miR-181b, miR-194, miR-197, miR-93, miR-708, and let-7g as having positive effects; miR-29b-2*, miR-126, and miR-182 as having negative effects; and miR-18a*, miR-425, and miR-30d as neutral. After principal component analysis, the prediction formula for prognosis, consisting of the expression values of the above-mentioned miRNAs, clearly divided Kaplan-Meier survival curves by the calculated Z-score (HR = 6.4566, P = 0.0067). The 16 miRNAs were enriched by gene ontology terms including angiogenesis, cell migration and proliferation, and apoptosis, in addition to signaling pathways including TGF-β/SMAD, Notch, TNF, and MAPKinase. Their target genes included BCL2-related genes, HMGA2 oncogene, and LIN28B cancer stem cell marker. Furthermore, three miRNAs including miR-181b, miR-30d, and miR-93, selected from the 16 miRNAs, also showed comparable results for survival (HR = 8.9342, P = 0.0007), suggestive of a miRNA signature for prognostic prediction in PCNSL. These results indicate that this miRNA signature is useful for prognostic prediction in PCNSL and would help us understand target pathways for therapies in PCNSL.

Association of functional polymorphisms in 3'-untranslated regions of COMT, DISC1, and DTNBP1 with schizophrenia: a meta-analysis

INTRODUCTION

In recent years, various studies have accumulated evidence of the involvement of single nucleotide polymorphisms (SNPs) in introns and exons in schizophrenia. The association of functional SNPs in the 3'-untranslated regions with schizophrenia has been explored in a number of studies, but the results are inconclusive because of limited meta-analyses. To systematically analyze the association between SNPs in 3'-untranslated regions and schizophrenia, we conducted a meta-analysis by combining all available studies on schizophrenia candidate genes.

MATERIALS AND METHODS

We searched candidate genes from the schizophrenia database and performed a comprehensive meta-analysis using all the available data up to August 2017. The association between susceptible SNPs and schizophrenia was assessed by the pooled odds ratio with 95% confidence interval using fixed-effect and random-effect models.

RESULTS

A total of 21 studies including 8291 cases and 9638 controls were used for meta-analysis. Three investigated SNPs were rs165599, rs3737597, and rs1047631 of COMT, DISC1, and DTNBP1, respectively. Our results suggested that rs3737597 showed a significant association with schizophrenia in Europeans (odds ratio: 1.584, P: 0.002, 95% confidence interval: 1.176-2.134) under a random-effect framework.

CONCLUSION

This meta-analysis indicated that rs3737597 of DISC1 was significantly associated with schizophrenia in Europeans, and it can be suggested as an ethnic-specific risk genetic factor.

MicroRNAs as Biomarkers in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable and fatal disorder characterized by the progressive loss of motor neurons in the cerebral cortex, brain stem, and spinal cord. Sporadic ALS form accounts for the majority of patients, but in 1–13.5% of cases the disease is inherited. The diagnosis of ALS is mainly based on clinical assessment and electrophysiological examinations with a history of symptom progression and is then made with a significant delay from symptom onset. Thus, the identification of biomarkers specific for ALS could be of a fundamental importance in the clinical practice. An ideal biomarker should display high specificity and sensitivity for discriminating ALS from control subjects and from ALS-mimics and other neurological diseases, and should then monitor disease progression within individual patients. microRNAs (miRNAs) are considered promising biomarkers for neurodegenerative diseases, since they are remarkably stable in human body fluids and can reflect physiological and pathological processes relevant for ALS. Here, we review the state of the art of miRNA biomarker identification for ALS in cerebrospinal fluid (CSF), blood and muscle tissue; we discuss advantages and disadvantages of different approaches, and underline the limits but also the great potential of this research for future practical applications.

Analytics of Cerebrospinal Fluid MicroRNA Quantitative PCR Studies

MicroRNAs (miRNAs) are small non-coding RNAs that regulate post-transcriptional gene expression. Recent studies have shown that human disease states correlate with measurable differences in the level of circulating miRNAs relative to healthy controls. Thus, there is great interest in developing clinical miRNA assays as diagnostic or prognostic biomarkers for diseases, and as surrogate measures for therapeutic outcomes. Our studies have focused on miRNAs in human cerebral spinal fluid (CSF) as biomarkers for central nervous system (CNS) diseases. Our objective here was to examine factors that may affect the outcome of quantitative PCR (qPCR) studies on CSF miRNAs, in order to guide planning and interpretation of future CSF miRNA TaqMan® low-density array (TLDA) studies. We obtained CSF from neurologically normal (control) donors and used TLDAs to measure miRNA expression. We examined sources of error in the TLDA outcomes due to (1) nonspecific amplification of products in total RNA, (2) variations in RNA isolations performed on different days, (3) miRNA primer probe efficiency, and (4) variations in individual TLDA cards. We also examined the utility of card-to-card TLDA corrections and use of an unchanged "reference standard" to remove batch processing effects in large-scale studies.

RNA accessibility impacts potency of Tough Decoy microRNA inhibitors

MicroRNAs (miRNAs) are small RNA molecules that post-transcriptionally regulate gene expression through silencing of complementary target mRNAs. miRNAs are involved in many biological processes, including cell proliferation, differentiation, cell signaling and cellular defense responses to infection. Strategies that allow for strong and stable suppression of specific microRNA activity are needed to study miRNA functions and to develop therapeutic intervention strategies aimed at interfering with miRNA activity in vivo. One of these classes of miRNA inhibitors are Tough Decoys (TuD) RNAs, which comprise of an imperfect RNA hairpin structure that harbors two opposing miRNA binding sites. Upon developing TuDs targeting Epstein-Barr virus miRNAs, we observed a strong variation in inhibitory potential between different TuD RNAs targeting the same miRNA. We show that the composition of the 'bulge' sequence in the miRNA binding sites has a strong impact on the inhibitory potency of the TuD. Our data implies that miRNA inhibition correlates with the thermodynamic properties of the TuD and that design aimed at lowering the TuD opening energy increases TuD potency. Our study provides specific guidelines for the design and construction of potent decoy-based miRNA inhibitors, which may be used for future therapeutic intervention strategies.

Dual-center, dual-platform microRNA profiling identifies potential plasma biomarkers of adult temporal lobe epilepsy

Background

There are no blood-based molecular biomarkers of temporal lobe epilepsy (TLE) to support clinical diagnosis. MicroRNAs are short noncoding RNAs with strong biomarker potential due to their cell-specific expression, mechanistic links to brain excitability, and stable detection in biofluids. Altered levels of circulating microRNAs have been reported in human epilepsy, but most studies collected samples from one clinical site, used a single profiling platform or conducted minimal validation.

Method

Using a case-control design, we collected plasma samples from video-electroencephalogram-monitored adult TLE patients at epilepsy specialist centers in two countries, performed genome-wide PCR-based and RNA sequencing during the discovery phase and validated findings in a large (>250) cohort of samples that included patients with psychogenic non-epileptic seizures (PNES).

Findings

After profiling and validation, we identified miR-27a-3p, miR-328-3p and miR-654-3p with biomarker potential. Plasma levels of these microRNAs were also changed in a mouse model of TLE but were not different to healthy controls in PNES patients. We determined copy number of the three microRNAs in plasma and demonstrate their rapid detection using an electrochemical RNA microfluidic disk as a prototype point-of-care device. Analysis of the microRNAs within the exosome-enriched fraction provided high diagnostic accuracy while Argonaute-bound miR-328-3p selectively increased in patient samples after seizures. In situ hybridization localized miR-27a-3p and miR-328-3p within neurons in human brain and bioinformatics predicted targets linked to growth factor signaling and apoptosis.

Interpretation

This study demonstrates the biomarker potential of circulating microRNAs for epilepsy diagnosis and mechanistic links to underlying pathomechanisms.

MicroRNAs in depression and suicide: Recent insights and future perspectives

Suicide is a major public health concern. A significant proportion of depressed individuals show suicidal ideation. The currently available medications are not optimal and a large number of depressed/suicidal patients do not respond to these medications. Thus, there is an urgent need to fully understand the neurobiological mechanisms associated with depression and suicidal behavior and to find novel targets for therapeutic interventions. In this regard, microRNAs (miRNAs), member of small non-coding RNA family, have emerged as an invaluable tool not only to understand disease pathogenesis but also to precisely pinpoint the targets that can be developed as drugs. In this review, these aspects have been discussed in a comprehensive and critical manner.

Discovery and validation of blood microRNAs as molecular biomarkers of epilepsy: Ways to close current knowledge gaps

There is a major unmet need for biomarkers of epilepsy. Biofluids such as blood offer a potential source of molecular biomarkers. MicroRNAs (miRNAs) fulfill several key requirements for a blood‐based molecular biomarker being enriched in the brain and dysregulated in epileptic brain tissue, and manipulation of miRNAs can have seizure‐suppressive and disease‐modifying effects in preclinical models. Biofluid miRNAs also possess qualities that are favorable for translation, including stability and easy and cheap assay techniques. Herein we review findings from both clinical and animal models. Studies have featured a mix of unbiased profiling and hypothesis‐driven efforts. Blood levels of several brain‐enriched miRNAs are altered in patients with epilepsy and in patients with drug‐resistant compared to drug‐responsive seizures, with encouraging receiver‐operating characteristic (ROC) curve analyses, both in terms of sensitivity and specificity. Both focal and generalized epilepsies are associated with altered blood miRNA profiles, and associations with clinical parameters including seizure burden have been reported. Results remain preliminary, however. There is a need for continued discovery and validation efforts that include multicenter studies and attention to study design, sample collection methodology, and quality control. Studies focused on epileptogenesis as well as associations with covariables such as sex, etiology, and timing of sampling remain limited. We identify 10 knowledge gaps and propose experiments to close these. If adequately addressed, biofluid miRNAs may be an important future source of diagnostic biomarkers that could also support forthcoming trials of antiepileptogenesis or disease‐modifying therapies.

Circulating miRNAs as Diagnostic Biomarkers for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. Its main neuropathological hallmarks are the degeneration of dopaminergic neurons in the substantia nigra and alpha-synuclein containing protein inclusions, called Lewy Bodies. The diagnosis of idiopathic PD is still based on the assessment of clinical criteria, leading to an insufficient diagnostic accuracy. Additionally, there is no biomarker available allowing the prediction of the disease course or monitoring the response to therapeutic approaches. So far, protein biomarker candidates such as alpha-synuclein have failed to improve diagnosis of PD. Circulating microRNAs (miRNAs) in body fluids are promising biomarker candidates for PD, as they are easily accessible by non- or minimally-invasive procedures and changes in their expression are associated with pathophysiological processes relevant for PD. Advances in miRNA analysis methods resulted in numerous recent publications on miRNAs as putative biomarkers. Here, we discuss the applicability of different body fluids as sources for miRNA biomarkers, highlight technical aspects of miRNA analysis and give an overview on published studies investigating circulating miRNAs as biomarker candidates for diagnosis of PD and other Parkinsonian syndromes.

Glioma in Schizophrenia: Is the Risk Higher or Lower?

Whether persons with schizophrenia have a higher or lower incidence of cancer has been discussed for a long time. Due to the complex mechanisms and characteristics of different types of cancer, it is difficult to evaluate the exact relationship between cancers and schizophrenia without considering the type of tumor. Schizophrenia, a disabling mental illness that is now recognized as a neurodevelopmental disorder, is more correlated with brain tumors, such as glioma, than other types of tumors. Thus, we mainly focused on the relationship between schizophrenia and glioma morbidity. Glioma tumorigenesis and schizophrenia may share similar mechanisms; gene/pathway disruption would affect neurodevelopment and reduce the risk of glioma. The molecular defects of disrupted-in-schizophrenia-1 (DISC1), P53, brain-derived neurotrophic factor (BDNF) and C-X-C chemokine receptors type 4 (CXCR4) involved in schizophrenia pathogenesis might play opposite roles in glioma development. Many microRNAs (miRNAs) such as miR-183, miR-9, miR-137 and miR-126 expression change may be involved in the cross talk between glioma prevalence and schizophrenia. Finally, antipsychotic drugs may have antitumor effects. All these factors show that persons with schizophrenia have a decreased incidence of glioma; therefore, epidemiological investigation and studies comparing genetic and epigenetic aberrations involved in both of these complex diseases should be performed. These studies can provide more insightful knowledge about glioma and schizophrenia pathophysiology and help to determine the target/strategies for the prevention and treatment of the two diseases.

Current Enlightenment About Etiology and Pharmacological Treatment of Autism Spectrum Disorder

Autistic Spectrum Disorder (ASD) is a complex neurodevelopmental brain disorder characterized by two core behavioral symptoms, namely impairments in social communication and restricted/repetitive behavior. The molecular mechanisms underlying ASD are not well understood. Recent genetic as well as non-genetic animal models contributed significantly in understanding the pathophysiology of ASD, as they establish autism-like behavior in mice and rats. Among the genetic causes, several chromosomal mutations including duplications or deletions could be possible causative factors of ASD. In addition, the biochemical basis suggests that several brain neurotransmitters, e.g., dopamine (DA), serotonin (5-HT), gamma-amino butyric acid (GABA), acetylcholine (ACh), glutamate (Glu) and histamine (HA) participate in the onset and progression of ASD. Despite of convincible understanding, risperidone and aripiprazole are the only two drugs available clinically for improving behavioral symptoms of ASD following approval by Food and Drug Administration (FDA). Till date, up to our knowledge there is no other drug approved for clinical usage specifically for ASD symptoms. However, many novel drug candidates and classes of compounds are underway for ASD at different phases of preclinical and clinical drug development. In this review, the diversity of numerous aetiological factors and the alterations in variety of neurotransmitter generation, release and function linked to ASD are discussed with focus on drugs currently used to manage neuropsychiatric symptoms related to ASD. The review also highlights the clinical development of drugs with emphasis on their pharmacological targets aiming at improving core symptoms in ASD.

The roles of extracellular vesicle microRNAs in the central nervous system

MicroRNAs (miRNAs) are small, highly conserved non-coding RNA molecules that post-transcriptionally regulate protein expression and most biological processes. Mature miRNAs are recruited to the RNA-induced silencing complex (RISC) and target mRNAs via complementary base-pairing, thus resulting in translational inhibition and/or transcript degradation. Here, we present evidence implicating miRNAs within extracellular vesicles (EVs), including microvesicles and exosomes, as mediators of central nervous system (CNS) development, homeostasis, and injury. EVs are extracellular vesicles that are secreted by all cells and represent a novel method of intercellular communication. In glial cells, the transfer of miRNAs via EVs can alter the function of recipient cells and significantly impacts cellular mechanisms involved in both injury and repair. This review discusses the value of information to be gained by studying miRNAs within EVs in the context of CNS diseases and their potential use in the development of novel disease biomarkers and therapeutic strategies.

Non-Contingent Exposure to Amphetamine in Adolescence Recruits miR-218 to Regulate Dcc Expression in the VTA

The development of the dopamine input to the medial prefrontal cortex occurs during adolescence and is a process that is vulnerable to disruption by stimulant drugs such as amphetamine. We have previously linked the amphetamine-induced disruption of dopamine connectivity and prefrontal cortex maturation during adolescence to the downregulation of the Netrin-1 receptor, DCC, in dopamine neurons. However, how DCC expression in dopamine neurons is itself regulated is completely unknown. MicroRNA (miRNA) regulation of mRNA translation and stability is a prominent mechanism linking environmental events to changes in protein expression. Here, using male mice, we show that miR-218 is expressed in dopamine neurons and is a repressor of DCC. Whereas Dcc mRNA levels increase from early adolescence to adulthood, miR-218 exhibits the exact opposite switch, most likely maintaining postnatal Dcc expression. This dynamic regulation appears to be selective to Dcc since the expression of Robo 1, the other guidance cue receptor target of miR-218, does not vary with age. Amphetamine in adolescence, but not in adulthood, increases miR-218 in the VTA and this event is required for drug-induced downregulation of Dcc mRNA and protein expression. This effect seems to be specific to Dcc because amphetamine does not alter Robo1. Furthermore, the upregulation of miR-218 by amphetamine requires dopamine D2 receptor activation. These findings identify miR-218 as regulator of DCC in the VTA both in normal development and after drug exposure in adolescence.

MicroRNAs in Human Cerebrospinal Fluid as Biomarkers for Alzheimer's Disease

BACKGROUND

Currently available biomarkers of Alzheimer's disease (AD) include cerebrospinal fluid (CSF) protein analysis and amyloid PET imaging, each of which has limitations. The discovery of extracellular microRNAs (miRNAs) in CSF raises the possibility that miRNA may serve as novel biomarkers of AD.

OBJECTIVE

Investigate miRNAs in CSF obtained from living donors as biomarkers for AD.

METHODS

We profiled miRNAs in CSF from 50 AD patients and 49 controls using TaqMan® arrays. Replicate studies performed on a subset of 32 of the original CSF samples verified 20 high confidence miRNAs. Stringent data analysis using a four-step statistical selection process including log-rank and receiver operating characteristic (ROC) tests, followed by random forest tests, identified 16 additional miRNAs that discriminate AD from controls. Multimarker modeling evaluated linear combinations of these miRNAs via best-subsets logistic regression, and computed area under the ROC (AUC) curve ascertained classification performance. The influence of ApoE genotype on miRNA biomarker performance was also evaluated.

RESULTS

We discovered 36 miRNAs that discriminate AD from control CSF. 20 of these retested in replicate studies verified differential expression between AD and controls. Stringent statistical analysis also identified these 20 miRNAs, and 16 additional miRNA candidates. Top-performing linear combinations of 3 and 4 miRNAs have AUC of 0.80-0.82. Addition of ApoE genotype to the model improved performance, i.e., AUC of 3 miRNA plus ApoE4 improves to 0.84.

CONCLUSIONS

CSF miRNAs can discriminate AD from controls. Combining miRNAs improves sensitivity and specificity of biomarker performance, and adding ApoE genotype improves classification.

Protective role of microRNA-219-5p inhibitor against spinal cord injury via liver receptor homolog-1/Wnt/β-catenin signaling pathway regulation

The present study aimed to investigate the role of microRNA (miR)-219-5p in spinal cord injury (SCI) and to examine the underlying molecular mechanism. SCI rat and cell models were conducted in the current study, while reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the level of miR-219-5p in the SCI mice and neurons. Bioinformatics analysis was applied to predict the target genes of miR-219-5p, and dual-luciferase reporter assay was performed to verify the prediction. In addition, MTT assay and flow cytometry were conducted to determine the cell viability and cell apoptosis of the neurons, respectively. Western blot analysis was also performed to detect the expression of associated proteins. The study results demonstrated that miR-219-5p was highly expressed in SCI mice and neurons, and directly targets liver receptor homolog-1 (LRH-1). The neuron viability was significantly reduced by SCI, however, it was recovered upon transfection with an miR-219-5p inhibitor. Neuron apoptosis was notably induced by SCI and inhibited by miR-219-5p inhibition. The LRH-1/Wnt/β-catenin signaling pathway was also inhibited by SCI, while it was significantly enhanced by the miR-219-5p inhibitor. Furthermore, LRH-1 overexpression eliminated the effects of the miR-219-5p inhibitor on SCI. In conclusion, these data indicated that the miR-219-5p inhibitor served a protective role in SCI via regulating the LRH-1/Wnt/β-catenin signaling pathway.

MiRNA Influences in Neuroblast Modulation: An Introspective Analysis

Neuroblastoma (NB) is the most common occurring solid paediatric cancer in children under the age of five years. Whether of familial or sporadic origin, chromosome abnormalities contribute to the development of NB and cause dysregulation of microRNAs (miRNAs). MiRNAs are small non-coding, single stranded RNAs that target messenger RNAs at the post-transcriptional levels by repressing translation within all facets of human physiology. Such gene 'silencing' activities by miRNAs allows the development of regulatory feedback loops affecting multiple functions within the cell, including the possible differentiation of neural stem cell (NSC) lineage selection. Neurogenesis includes stages of self-renewal and fate specification of NSCs, migration and maturation of young neurones, and functional integration of new neurones into the neural circuitry, all of which are regulated by miRNAs. The role of miRNAs and their interaction in cellular processes are recognised aspects of cancer genetics, and miRNAs are currently employed as biomarkers for prognosis and tumour characterisation in multiple cancer models. Consequently, thorough understanding of the mechanisms of how these miRNAs interplay at the transcriptomic level will definitely lead to the development of novel, bespoke and efficient therapeutic measures, with this review focusing on the influences of miRNAs on neuroblast modulations leading to neuroblastoma.

Dosing, collection, and quality control issues in cerebrospinal fluid research using animal models

Cerebrospinal fluid (CSF) is a complex fluid filling the ventricular system and surrounding the brain and spinal cord. Although the bulk of CSF is created by the choroid plexus, a significant fraction derives from the interstitial fluid in the brain and spinal cord parenchyma. For this reason, CSF can often be used as a source of pharmacodynamic and prognostic biomarkers to reflect biochemical changes occurring within the brain. For instance, CSF biomarkers can be used to diagnose and track progression of disease as well as understand pharmacokinetic and pharmacodynamic relationships in clinical trials. To facilitate the use of these biomarkers in humans, studies in preclinical species are often valuable. This review summarizes methods for preclinical CSF collection for biomarkers from mice, rats, and nonhuman primates. In addition, dosing directly into CSF is increasingly being used to improve drug levels in the brain. Therefore, this review also summarizes the state of the art in CSF dosing in these preclinical species.

Regional and subtype-dependent miRNA signatures in sporadic Creutzfeldt-Jakob disease are accompanied by alterations in miRNA silencing machinery and biogenesis

Increasing evidence indicates that microRNAs (miRNAs) are contributing factors to neurodegeneration. Alterations in miRNA signatures have been reported in several neurodegenerative dementias, but data in prion diseases are restricted to ex vivo and animal models. The present study identified significant miRNA expression pattern alterations in the frontal cortex and cerebellum of sporadic Creutzfeldt-Jakob disease (sCJD) patients. These changes display a highly regional and disease subtype-dependent regulation that correlates with brain pathology. We demonstrate that selected miRNAs are enriched in sCJD isolated Argonaute(Ago)-binding complexes in disease, indicating their incorporation into RNA-induced silencing complexes, and further suggesting their contribution to disease-associated gene expression changes. Alterations in the miRNA-mRNA regulatory machinery and perturbed levels of miRNA biogenesis key components in sCJD brain samples reported here further implicate miRNAs in sCJD gene expression (de)regulation. We also show that a subset of sCJD-altered miRNAs are commonly changed in Alzheimer's disease, dementia with Lewy bodies and fatal familial insomnia, suggesting potential common mechanisms underlying these neurodegenerative processes. Additionally, we report no correlation between brain and cerebrospinal fluid (CSF) miRNA-profiles in sCJD, indicating that CSF-miRNA profiles do not faithfully mirror miRNA alterations detected in brain tissue of human prion diseases. Finally, utilizing a sCJD MM1 mouse model, we analyzed the miRNA deregulation patterns observed in sCJD in a temporal manner. While fourteen sCJD-related miRNAs were validated at clinical stages, only two of those were changed at early symptomatic phase, suggesting that the miRNAs altered in sCJD may contribute to later pathogenic processes. Altogether, the present work identifies alterations in the miRNA network, biogenesis and miRNA-mRNA silencing machinery in sCJD, whereby contributions to disease mechanisms deserve further investigation.

Blood-Bourne MicroRNA Biomarker Evaluation in Attention-Deficit/Hyperactivity Disorder of Han Chinese Individuals: An Exploratory Study

Background: Attention-deficit/hyperactivity disorder (ADHD) is a highly genetic neurodevelopmental disorder, and its dysregulation of gene expression involves microRNAs (miRNAs). The purpose of this study was to identify potential miRNAs biomarkers and then use these biomarkers to establish a diagnostic panel for ADHD. Design and methods: RNA samples from white blood cells (WBCs) of five ADHD patients and five healthy controls were combined to create one pooled patient library and one control library. We identified 20 candidate miRNAs with the next-generation sequencing (NGS) technique (Illumina). Blood samples were then collected from a Training Set (68 patients and 54 controls) and a Testing Set (20 patients and 20 controls) to identify the expression profiles of these miRNAs with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). We used receiver operating characteristic (ROC) curves and the area under the curve (AUC) to evaluate both the specificity and sensitivity of the probability score yielded by the support vector machine (SVM) model. Results: We identified 13 miRNAs as potential ADHD biomarkers. The ΔCt values of these miRNAs in the Training Set were integrated to create a biomarker model using the SVM algorithm, which demonstrated good validity in differentiating ADHD patients from control subjects (sensitivity: 86.8%, specificity: 88.9%, AUC: 0.94, p < 0.001). The results of the blind testing showed that 85% of the subjects in the Testing Set were correctly classified using the SVM model alignment (AUC: 0.91, p < 0.001). The discriminative validity is not influenced by patients' age or gender, indicating both the robustness and the reliability of the SVM classification model. Conclusion: As measured in peripheral blood, miRNA-based biomarkers can aid in the differentiation of ADHD in clinical settings. Additional studies are needed in the future to clarify the ADHD-associated gene functions and biological mechanisms modulated by miRNAs.

Making Dopamine Connections in Adolescence

A dramatic maturational process ongoing in adolescence is prefrontal cortex development, including its dopamine innervation. Dopamine axons grow from the striatum to the prefrontal cortex, the only known case of long-distance axon growth during adolescence. This is coordinated by the Netrin-1 guidance cue receptor DCC (deleted in colorectal cancer), which in turn controls the intrinsic development of the prefrontal cortex itself. Stimulant drugs in adolescence alter DCC in dopamine neurons and, in turn prefrontal cortex maturation, impacting cognitive abilities. Variations in DCC expression are linked to psychiatric conditions of prefrontal cortex dysfunction, and microRNA regulation of DCC may be key to determining adolescent vulnerability or resilience. Since early interventions are proving to effectively ameliorate disease outcome, the Netrin-1 system is a promising therapeutic target.

Formin 2 links neuropsychiatric phenotypes at young age to an increased risk for dementia

Age-associated memory decline is due to variable combinations of genetic and environmental risk factors. How these risk factors interact to drive disease onset is currently unknown. Here we begin to elucidate the mechanisms by which post-traumatic stress disorder (PTSD) at a young age contributes to an increased risk to develop dementia at old age. We show that the actin nucleator Formin 2 (Fmn2) is deregulated in PTSD and in Alzheimer's disease (AD) patients. Young mice lacking the Fmn2 gene exhibit PTSD-like phenotypes and corresponding impairments of synaptic plasticity, while the consolidation of new memories is unaffected. However, Fmn2 mutant mice develop accelerated age-associated memory decline that is further increased in the presence of additional risk factors and is mechanistically linked to a loss of transcriptional homeostasis. In conclusion, our data present a new approach to explore the connection between AD risk factors across life span and provide mechanistic insight to the processes by which neuropsychiatric diseases at a young age affect the risk for developing dementia.

HIV/neuroAIDS biomarkers

HIV infection often causes neurological symptoms including cognitive and motor dysfunction, which have been collectively termed HIV/neuroAIDS. Neuropsychological assessment and clinical symptoms have been the primary diagnostic criteria for HIV/neuroAIDS, even for the mild cognitive and motor disorder, the most prevalent form of HIV/neuroAIDS in the era of combination antiretroviral therapy. Those performance-based assessments and symptoms are generally descriptive and do not have the sensitivity and specificity to monitor the diagnosis, progression, and treatment response of the disease when compared to objective and quantitative laboratory-based biological markers, or biomarkers. In addition, effects of demographics and comorbidities such as substance abuse, psychiatric disease, nutritional deficiencies, and co-infection on HIV/neuroAIDS could be more readily determined using biomarkers than using neuropsychological assessment and clinical symptoms. Thus, there have been great efforts in identification of HIV/neuroAIDS biomarkers over the past two decades. The need for reliable biomarkers of HIV/neuroAIDS is expected to increase as the HIV-infected population ages and their vulnerability to neurodegenerative diseases, particularly Alzheimer's disease increases. Currently, three classes of HIV/neuroAIDS biomarkers are being pursued to establish objective laboratory-based definitions of HIV-associated neurologic injury: cerebrospinal fluid biomarkers, blood biomarkers, and neuroimaging biomarkers. In this review, we will focus on the current knowledge in the field of HIV/neuroAIDS biomarker discovery.

MicroRNA‑138‑5p regulates neural stem cell proliferation and differentiation in vitro by targeting TRIP6 expression

Research on neural stem cells (NSCs) has recently focused on microRNAs (miRNAs), a class of small non-coding RNAs that have crucial roles in regulating NSC proliferation and differentiation. In the present study, a quantitative-polymerase chain reaction assay revealed that the expression of miRNA (miR)-138-5p was significantly decreased during neural differentiation of NSCs in vitro. Overexpression of miR-138-5p reduced NSC proliferation and increased NSC differentiation. Furthermore, suppression of miR-138-5p via transfection with a miRNA inhibitor enhanced NSC proliferation and attenuated NSC differentiation. Additionally, expression of thyroid hormone receptor interacting protein 6 (TRIP6), a critical regulator of NSCs, was negatively correlated with the miR-138-5p level. A luciferase assay demonstrated that miR-138-5p regulate TRIP6 by directly binding the 3′-untranslated region of the mRNA. Additionally, upregulation of TRIP6 rescued the NSC proliferation deficiency induced by miR-138-5p and abolished miR-138-5p-promoted NSCs differentiation. By contrast, downregulation of TRIP6 produced the opposite effect on proliferation and differentiation of NSCs transfected with anti-miR-138-5p. Taken together, the data suggest that miR-138-5p regulates NSCs proliferation and differentiation, and may be useful in developing novel treatments for neurological disorders via manipulation of miR-138-5p in NSCs.

Pharmacoepigenomics of opiates and methadone maintenance treatment: current data and perspectives

Current treatments of opioid addiction include primarily maintenance medications such as methadone. Chronic exposure to opiate and/or long-lasting maintenance treatment induce modulations of gene expression in brain and peripheral tissues. There is increasing evidence that epigenetic modifications underlie these modulations. This review summarizes published results on opioid-induced epigenetic changes in animal models and in patients. The epigenetic modifications observed with other drugs of abuse often used by opiate abusers are also outlined. Specific methadone maintenance treatment induced epigenetic modifications at different treatment stages may be combined with the ones resulting from patients’ substance use history. Therefore, research comparing groups of addicts with similar history and substances use disorders but contrasting for well-characterized treatment phenotypes should be encouraged.

Tiny RNAs and their voyage via extracellular vesicles: Secretion of bacterial small RNA and eukaryotic microRNA

MicroRNAs are small non-coding RNAs that bind to the 3'-untranslated region of target mRNAs and have transcriptional or translational inhibitory function in eukaryotes. Before microRNAs were widely known, bacterial non-coding small RNAs around 50-200 nt in length were discovered whose mechanism of action resembled that of microRNAs. Recently, RNAs that are of similar size to or smaller than microRNAs have been discovered in bacteria and indeed, this class of small RNAs have been found throughout all domains of life. Moreover, recent findings suggest that these tiny RNAs can be released via extracellular vesicles (such as exosomes in eukaryotes and outer membrane vesicles in bacteria), which in turn heralds a new field of research, interkingdom communication. This review discusses two similar classes of small RNAs in evolutionarily distinct eukaryotes and bacteria. In addition to their biogenesis and regulation, we discuss small RNA vehicles and their secretion. Impact statement The possible endogenous functions of small RNAs such as regulatory small RNAs in bacteria and microRNAs in eukaryotes have been extensively studied since they were first discovered. However, their powerful functions should not be seen as limited to their cells of origin. Recently, several papers have demonstrated that small RNAs function as signaling molecules between cells. This is possible because small RNAs can be shuttled around after being incorporated into environmentally protective extracellular vesicles. It is now clearly plausible that secreted small RNAs can regulate other types of cells through biofluids. Given their "common molecule" status, the role of small RNAs in mediating bacteria-human crosstalk is an emerging and competitive area of genetic research. This review provides insight into the function of small RNAs in intercellular and even interkingdom communication.

Consensus paper of the WFSBP Task Force on Biological Markers: Criteria for biomarkers and endophenotypes of schizophrenia, part III: Molecular mechanisms

OBJECTIVES

Despite progress in identifying molecular pathophysiological processes in schizophrenia, valid biomarkers are lacking for both the disease and treatment response.

METHODS

This comprehensive review summarises recent efforts to identify molecular mechanisms on the level of protein and gene expression and epigenetics, including DNA methylation, histone modifications and micro RNA expression. Furthermore, it summarises recent findings of alterations in lipid mediators and highlights inflammatory processes. The potential that this research will identify biomarkers of schizophrenia is discussed.

RESULTS

Recent studies have not identified clear biomarkers for schizophrenia. Although several molecular pathways have emerged as potential candidates for future research, a complete understanding of these metabolic pathways is required to reveal better treatment modalities for this disabling condition.

CONCLUSIONS

Large longitudinal cohort studies are essential that pair a thorough phenotypic and clinical evaluation for example with gene expression and proteome analysis in blood at multiple time points. This approach might identify biomarkers that allow patients to be stratified according to treatment response and ideally also allow treatment response to be predicted. Improved knowledge of molecular pathways and epigenetic mechanisms, including their potential association with environmental influences, will facilitate the discovery of biomarkers that could ultimately be effective tools in clinical practice.

Aberrant microRNA expression in patients with painful peripheral neuropathies

Changes in the neuro-immune balance play a major role in the induction and maintenance of neuropathic pain. We recently reported pathophysiologically relevant alterations in skin and sural nerve cytokine expression in peripheral neuropathies of different etiologies. Immune processes and cytokine expression are under tight control of microRNAs (miRNAs). To identify potential master switches in the neuro-immune balance, we aimed at characterizing inflammation-regulating miRNA profiles in patients with peripheral neuropathies. In an unselected patient cohort with polyneuropathies of different etiologies seen at our neuromuscular center between 2014 and 2015, we determined the systemic and local relative expression of miR-21-5p, miR-146a, and miR-155. In white blood cells we found higher miR-21 (p<0.001) and miR-146a (p<0.001) expression and lower miR-155 (p<0.001) expression when compared to healthy controls. In sural nerve, miR-21 (p<0.02) was increased in painful compared to painless neuropathies. In painful neuropathies, skin biopsies from the lower leg had reduced miR-146a (p<0.001) and miR-155 (p<0.001) expression compared to the thigh. Thus, peripheral neuropathies are associated with aberrant miRNA expression in white blood cells, sural nerve, and skin. These miRNA patterns may help to identify factors that determine the painfulness of peripheral neuropathies and lead to druggable targets.

MicroRNA-4639 Is a Regulator of DJ-1 Expression and a Potential Early Diagnostic Marker for Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder and has profound impacts on the daily lives of patients. However, there is a lack of effective biomarkers for early diagnosis, and the mechanisms of PD pathogenesis remain obscure. microRNAs (miRNAs) are post-transcriptional gene regulators and can be easily detected in plasma, which suggests a promising role as diagnostic markers. Here, we aimed to explore a peripheral biomarker, which not only can be applied for early diagnosis of PD but also has the potential to be a therapeutic target. Through miRNA microarray screening and further validation in plasma from 169 sporadic PD patients, 170 healthy controls, and 60 essential tremor (ET) patients, hsa-miR-4639-5p level was identified to be significantly up-regulated in PD patients. Also, it was able to discriminate between early PD patients (disease duration ≤2 years or Hoehn and Yahr stage 1–2.5) and healthy controls. Furthermore, hsa-miR-4639-5p was shown to negatively regulate DJ-1 (PARK7), a well-known PD-related gene, in the post-transcriptional level. Abnormal up-regulation of hsa-miR-4639-5p caused down-regulation of DJ-1 protein level, leading to severe oxidative stress and neuronal death. In conclusion, hsa-miR-4639-5p has the potential to be a peripheral diagnostic biomarker and therapeutic target for early PD.