MiR-375 is Essential for Human Spinal Motor Neuron Development and May Be Involved in Motor Neuron Degeneration

MicroRNA (miRNA) as a biomarker for diagnosis, prognosis, and therapeutics molecules in neurodegenerative disease

Neurodegenerative diseases that include Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS) that arise due to numerous causes like protein accumulation and autoimmunity characterized by neurologic depletion which lead to incapacity in normal physiological function such as thinking and movement in these patients. Glial cells perform an important role in protective neuronal function; in the case of neuroinflammation, glial cell dysfunction can promote the development of neurodegenerative diseases. miRNA that participates in gene regulation and plays a vital role in many biological processes in the body; in the central nervous system (CNS), it can play an essential part in neural maturation and differentiation. In neurodegenerative diseases, miRNA dysregulation occurs, enhancing the development of these diseases. In this review, we discuss neurodegenerative disease (Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS)) and how miRNA is preserved as a diagnostic biomarker or therapeutic agent in these disorders. Finally, we highlight miRNA as therapy.

miRNA-Mediated Mechanisms in the Generation of Effective and Safe Oncolytic Viruses

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by inhibiting the translation of target transcripts. The expression profiles of miRNAs vary in different tissues and change with the development of diseases, including cancer. This feature has begun to be used for the modification of oncolytic viruses (OVs) in order to increase their selectivity and efficacy. OVs represent a relatively new class of anticancer drugs; they are designed to replicate in cancer tumors and destroy them. These can be natural viruses that can replicate within cancer tumor cells, or recombinant viruses created in laboratories. There are some concerns regarding OVs' toxicity, due to their ability to partially replicate in healthy tissues. In addition, lytic and immunological responses upon OV therapy are not always sufficient, so various OV editing methods are used. This review discusses the latest results of preclinical and clinical studies of OVs, modifications of which are associated with the miRNA-mediated mechanism of gene silencing.

The role of DNA damage in neural stem cells ageing

Neural stem cells (NSCs) are pluripotent stem cells with the potential to differentiate into a variety of nerve cells. NSCs are susceptible to both intracellular and extracellular insults, thus causing DNA damage. Extracellular insults include ultraviolet, ionizing radiation, base analogs, modifiers, alkyl agents and others, while intracellular factors include Reactive oxygen species (ROS) radicals produced by mitochondria, mismatches that occur during DNA replication, deamination of bases, loss of bases, and more. When encountered with DNA damage, cells typically employ three coping strategies: DNA repair, damage tolerance, and apoptosis. NSCs, like many other stem cells, have the ability to divide, differentiate, and repair DNA damage to prevent mutations from being passed down to the next generation. However, when DNA damage accumulates over time, it will lead to a series of alterations in the metabolism of cells, which will cause cellular ageing. The ageing and exhaustion of neural stem cell will have serious effects on the body, such as neurodegenerative diseases. The purpose of this review is to examine the processes by which DNA damage leads to NSCs ageing and the mechanisms of DNA repair in NSCs.

MicroRNAs in Testicular Germ Cell Tumors: The Teratoma Challenge

Testicular germ cell tumors (TGCTs) are relatively common in young men, making accurate diagnosis and prognosis assessment essential. MicroRNAs (miRNAs), including microRNA-371a-3p (miR-371a-3p), have shown promise as biomarkers for TGCTs. This review discusses the recent advancements in the use of miRNA biomarkers in TGCTs, with a focus on the challenges surrounding the noninvasive detection of teratomas. Circulating miR-371a-3p, which is expressed in undifferentiated TGCTs but not in teratomas, is a promising biomarker for TGCTs. Its detection in serum, plasma, and, potentially, cystic fluid could be useful for TGCT diagnosis, surveillance, and monitoring of therapeutic response. Other miRNAs, such as miR-375-3p and miR-375-5p, have been investigated to differentiate between TGCT subtypes (teratoma, necrosis/fibrosis, and viable tumors), which can aid in treatment decisions. However, a reliable marker for teratoma has yet to be identified. The clinical applications of miRNA biomarkers could spare patients from unnecessary surgeries and allow for more personalized therapeutic approaches. Particularly in patients with residual masses larger than 1 cm following chemotherapy, it is critical to differentiate between viable tumors, teratomas, and necrosis/fibrosis. Teratomas, which mimic somatic tissues, present a challenge in differentiation and require a comprehensive diagnostic approach. The combination of miR-371 and miR-375 shows potential in enhancing diagnostic precision, aiding in distinguishing between teratomas, viable tumors, and necrosis. The implementation of miRNA biomarkers in TGCT care could improve patient outcomes, reduce overtreatment, and facilitate personalized therapeutic strategies. However, a reliable marker for teratoma is still lacking. Future research should focus on the clinical validation and standardization of these biomarkers to fully realize their potential.

Genomic and transcriptomic advances in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder and the most common motor neuron disease. ALS shows substantial clinical and molecular heterogeneity. In vitro and in vivo models coupled with multiomic techniques have provided important contributions to unraveling the pathomechanisms underlying ALS. To date, despite promising results and accumulating knowledge, an effective treatment is still lacking. Here, we provide an overview of the literature on the use of genomics, epigenomics, transcriptomics and microRNAs to deeply investigate the molecular mechanisms developing and sustaining ALS. We report the most relevant genes implicated in ALS pathogenesis, discussing the use of different high-throughput sequencing techniques and the role of epigenomic modifications. Furthermore, we present transcriptomic studies discussing the most recent advances, from microarrays to bulk and single-cell RNA sequencing. Finally, we discuss the use of microRNAs as potential biomarkers and promising tools for molecular intervention. The integration of data from multiple omic approaches may provide new insights into pathogenic pathways in ALS by shedding light on diagnostic and prognostic biomarkers, helping to stratify patients into clinically relevant subgroups, revealing novel therapeutic targets and supporting the development of new effective therapies.

FUS-dependent microRNA deregulations identify TRIB2 as a druggable target for ALS motor neurons

MicroRNAs (miRNAs) modulate mRNA expression, and their deregulation contributes to various diseases including amyotrophic lateral sclerosis (ALS). As fused in sarcoma (FUS) is a causal gene for ALS and regulates biogenesis of miRNAs, we systematically analyzed the miRNA repertoires in spinal cords and hippocampi from ALS-FUS mice to understand how FUS-dependent miRNA deregulation contributes to ALS. miRNA profiling identified differentially expressed miRNAs between different central nervous system (CNS) regions as well as disease states. Among the up-regulated miRNAs, miR-1197 targets the pro-survival pseudokinase Trib2. A reduced TRIB2 expression was observed in iPSC-derived motor neurons from ALS patients. Pharmacological stabilization of TRIB2 protein with a clinically approved cancer drug rescues the survival of iPSC-derived human motor neurons, including those from a sporadic ALS patient. Collectively, our data indicate that miRNA profiling can be used to probe the molecular mechanisms underlying selective vulnerability, and TRIB2 is a potential therapeutic target for ALS.

Role of circulating biomarkers in spinal muscular atrophy: insights from a new treatment era

Spinal muscular atrophy (SMA) is a lower motor neuron disease due to biallelic mutations in the SMN1 gene on chromosome 5. It is characterized by progressive muscle weakness of limbs, bulbar and respiratory muscles. The disease is usually classified in four different phenotypes (1-4) according to age at symptoms onset and maximal motor milestones achieved. Recently, three disease modifying treatments have received approval from the Food and Drug Administration (FDA) and the European Medicines Agency (EMA), while several other innovative drugs are under study. New therapies have been game changing, improving survival and life quality for SMA patients. However, they have also intensified the need for accurate biomarkers to monitor disease progression and treatment efficacy. While clinical and neurophysiological biomarkers are well established and helpful in describing disease progression, there is a great need to develop more robust and sensitive circulating biomarkers, such as proteins, nucleic acids, and other small molecules. Used alone or in combination with clinical biomarkers, they will play a critical role in enhancing patients' stratification for clinical trials and access to approved treatments, as well as in tracking response to therapy, paving the way to the development of individualized therapeutic approaches. In this comprehensive review, we describe the foremost circulating biomarkers of current significance, analyzing existing literature on non-treated and treated patients with a special focus on neurofilaments and circulating miRNA, aiming to identify and examine their role in the follow-up of patients treated with innovative treatments, including gene therapy.

MicroRNA-375 Is Induced during Astrocyte-to-Neuron Reprogramming and Promotes Survival of Reprogrammed Neurons when Overexpressed

While astrocyte-to-neuron (AtN) reprogramming holds great promise in regenerative medicine, the molecular mechanisms that govern this unique biological process remain elusive. To understand the function of miRNAs during the AtN reprogramming process, we performed RNA-seq of both mRNAs and miRNAs on human astrocyte (HA) cultures upon NeuroD1 overexpression. Bioinformatics analyses showed that NeuroD1 not only activated essential neuronal genes to initiate the reprogramming process but also induced miRNA changes in HA. Among the upregulated miRNAs, we identified miR-375 and its targets, neuronal ELAVL genes (nELAVLs), which encode a family of RNA-binding proteins and were also upregulated by NeuroD1. We further showed that manipulating the miR-375 level regulated nELAVLs' expression during NeuroD1-mediated reprogramming. Interestingly, miR-375/nELAVLs were also induced by the reprogramming factors Neurog2 and ASCL1 in HA, suggesting a conserved function to neuronal reprogramming, and by NeuroD1 in the mouse astrocyte culture and spinal cord. Functionally, we showed that miR-375 overexpression improved NeuroD1-mediated reprogramming efficiency by promoting cell survival at early stages in HA and did not appear to compromise the maturation of the reprogrammed neurons. Lastly, overexpression of miR-375-refractory ELAVL4 induced apoptosis and reversed the cell survival-promoting effect of miR-375 during AtN reprogramming. Together, we demonstrated a neuroprotective role of miR-375 during NeuroD1-mediated AtN reprogramming.

Engineered human spinal cord-like tissues with dorsal and ventral neuronal progenitors for spinal cord injury repair in rats and monkeys

Transplanting human neural progenitor cells is a promising method of replenishing the lost neurons after spinal cord injury (SCI), but differentiating neural progenitor cells into the diverse types of mature functional spinal cord neurons in vivo is challenging. In this study, engineered human embryonic spinal cord-like tissues with dorsal and ventral neuronal characters (DV-SC) were generated by inducing human neural progenitor cells (hscNPCs) to differentiate into various types of dorsal and ventral neuronal cells on collagen scaffold in vitro. Transplantation of DV-SC into complete SCI models in rats and monkeys showed better therapeutic effects than undifferentiated hscNPCs, including pronounced cell survival and maturation. DV-SC formed a targeted connection with the host's ascending and descending axons, partially restored interrupted neural circuits, and improved motor evoked potentials and the hindlimb function of animals with SCI. This suggests that the transplantation of pre-differentiated hscNPCs with spinal cord dorsal and ventral neuronal characteristics could be a promising strategy for SCI repair.

MicroRNA-375 is induced during astrocyte-to-neuron reprogramming and promotes survival of reprogrammed neurons when overexpressed

While astrocyte-to-neuron (AtN) reprogramming holds great promise in regenerative medicine, the molecular mechanisms that govern this unique biological process remain elusive. MicroRNAs (miRNAs), as post-transcriptional regulators of gene expression, play crucial roles during development and under various pathological conditions. To understand the function of miRNAs during AtN reprogramming process, we performed RNA-seq of both mRNAs and miRNAs on human astrocyte (HA) cultures upon NeuroD1 overexpression. Bioinformatics analyses showed that NeuroD1 not only activates essential neuronal genes to initiate reprogramming process but also induces miRNA changes in HA. Among the upregulated miRNAs, we identified miR-375 and its targets, neuronal ELAVL genes ( nELAVLs ), which encode a family of RNA-binding proteins and are also upregulated by NeuroD1. We further showed that manipulating miR-375 level regulates nELAVLs expression during NeuroD1-mediated reprogramming. Interestingly, miR-375/ nELAVLs are also induced by reprogramming factors Neurog2 and ASCL1 in HA suggesting a conserved function to neuronal reprogramming, and by NeuroD1 in the mouse astrocyte culture and spinal cord. Functionally, we showed that miR-375 overexpression improves NeuroD1-mediated reprogramming efficiency by promoting cell survival at early stages in HA even in cultures treated with the chemotherapy drug Cisplatin. Moreover, miR-375 overexpression doesn't appear to compromise maturation of the reprogrammed neurons in long term HA cultures. Lastly, overexpression of miR-375-refractory ELAVL4 induces apoptosis and reverses the cell survival-promoting effect of miR-375 during AtN reprogramming. Together, we demonstrate a neuro-protective role of miR-375 during NeuroD1-mediated AtN reprogramming and suggest a strategy of combinatory overexpression of NeuroD1 and miR-375 for improving neuronal reprogramming efficiency.

The Expression Levels of MicroRNAs Differentially Expressed in Sudden Sensorineural Hearing Loss Patients' Serum Are Unchanged for up to 12 Months after Hearing Loss Onset

Sudden sensorineural hearing loss (SSNHL) is an acquired idiopathic hearing loss. Serum levels of small, non-coding RNAs and microRNAs (miRNAs) miR-195-5p/-132-3p/-30a-3p/-128-3p/-140-3p/-186-5p/-375-3p/-590-5p are differentially expressed in SSNHL patients within 28 days of hearing loss onset. This study determines if these changes persist by comparing the serum miRNA expression profile of SSNHL patients within 1 month of hearing loss onset with that of patients 3-12 months after hearing loss onset. We collected serum from consenting adult SSNHL patients at presentation or during clinic follow-up. We matched patient samples drawn 3-12 months after hearing loss onset (delayed group, n = 9 patients) by age and sex to samples drawn from patients within 28 days of hearing loss onset (immediate group, n = 14 patients). We compared the real-time PCR-determined expression levels of the target miRNAs between the two groups. We calculated the air conduction pure-tone-averaged (PTA) audiometric thresholds in affected ears at the initial and final follow-up visits. We undertook inter-group comparisons of hearing outcome status and initial and final PTA audiometric thresholds. There was no significant inter-group difference in miRNA expression level, hearing recovery status and initial and final affected ear PTA audiometric thresholds.

Modeling Movement Disorders via Generation of hiPSC-Derived Motor Neurons

Generation of motor neurons (MNs) from human-induced pluripotent stem cells (hiPSCs) overcomes the limited access to human brain tissues and provides an unprecedent approach for modeling MN-related diseases. In this review, we discuss the recent progression in understanding the regulatory mechanisms of MN differentiation and their applications in the generation of MNs from hiPSCs, with a particular focus on two approaches: induction by small molecules and induction by lentiviral delivery of transcription factors. At each induction stage, different culture media and supplements, typical growth conditions and cellular morphology, and specific markers for validation of cell identity and quality control are specifically discussed. Both approaches can generate functional MNs. Currently, the major challenges in modeling neurological diseases using iPSC-derived neurons are: obtaining neurons with high purity and yield; long-term neuron culture to reach full maturation; and how to culture neurons more physiologically to maximize relevance to in vivo conditions.

Effects of Extracorporeal Shockwave Therapy on Functional Recovery and Circulating miR-375 and miR-382-5p after Subacute and Chronic Spinal Cord Contusion Injury in Rats

Extracorporeal shockwave therapy (ESWT) can stimulate processes to promote regeneration, including cell proliferation and modulation of inflammation. Specific miRNA expression panels have been established to define correlations with regulatory targets within these pathways. This study aims to investigate the influence of low-energy ESWT—applied within the subacute and chronic phase of SCI (spinal cord injury) on recovery in a rat spinal cord contusion model. Outcomes were evaluated by gait analysis, µCT and histological analysis of spinal cords. A panel of serum-derived miRNAs after SCI and after ESWT was investigated to identify injury-, regeneration- and treatment-associated expression patterns. Rats receiving ESWT showed significant improvement in motor function in both a subacute and a chronic experimental setting. This effect was not reflected in changes in morphology, µCT-parameters or histological markers after ESWT. Expression analysis of various miRNAs, however, revealed changes after SCI and ESWT, with increased miR-375, indicating a neuroprotective effect, and decreased miR-382-5p potentially improving neuroplasticity via its regulatory involvement with BDNF. We were able to demonstrate a functional improvement of ESWT-treated animals after SCI in a subacute and chronic setting. Furthermore, the identification of miR-375 and miR-382-5p could potentially provide new targets for therapeutic intervention in future studies.

Differentially Expressed miRNAs in Age-Related Neurodegenerative Diseases: A Meta-Analysis

To date, no neurodegenerative diseases (NDDs) have cures, and the underlying mechanism of their pathogenesis is undetermined. As miRNAs extensively regulate all biological processes and are crucial regulators of healthy brain function, miRNAs differentially expressed in NDDs may provide insight into the factors that contribute to the emergence of protein inclusions and the propagation of deleterious cellular environments. A meta-analysis of miRNAs dysregulated in Alzheimer’s disease, Parkinson’s disease, multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies and frontotemporal lobar degeneration (TDP43 variant) was performed to determine if diseases within a proteinopathy have distinct or shared mechanisms of action leading to neuronal death, and if proteinopathies can be classified on the basis of their miRNA profiles. Our results identified both miRNAs distinct to the anatomy, disease type and pathology, and miRNAs consistently dysregulated within single proteinopathies and across neurodegeneration in general. Our results also highlight the necessity to minimize the variability between studies. These findings showcase the need for more transcriptomic research on infrequently occurring NDDs, and the need for the standardization of research techniques and platforms utilized across labs and diseases.

Deregulated mitochondrial microRNAs in Alzheimer's disease: Focus on synapse and mitochondria

Alzheimer's disease (AD) is the most common cause of dementia and is currently one of the biggest public health concerns in the world. Mitochondrial dysfunction in neurons is one of the major hallmarks of AD. Emerging evidence suggests that mitochondrial miRNAs potentially play important roles in the mitochondrial dysfunctions, focusing on synapse in AD progression. In this meta-analysis paper, a comprehensive literature review was conducted to identify and discuss the (1) role of mitochondrial miRNAs that regulate mitochondrial and synaptic functions; (2) the role of various factors such as mitochondrial dynamics, biogenesis, calcium signaling, biological sex, and aging on synapse and mitochondrial function; (3) how synapse damage and mitochondrial dysfunctions contribute to AD; (4) the structure and function of synapse and mitochondria in the disease process; (5) latest research developments in synapse and mitochondria in healthy and disease states; and (6) therapeutic strategies that improve synaptic and mitochondrial functions in AD. Specifically, we discussed how differences in the expression of mitochondrial miRNAs affect ATP production, oxidative stress, mitophagy, bioenergetics, mitochondrial dynamics, synaptic activity, synaptic plasticity, neurotransmission, and synaptotoxicity in neurons observed during AD. However, more research is needed to confirm the locations and roles of individual mitochondrial miRNAs in the development of AD.

Therapeutic Implications of miRNAs for Muscle-Wasting Conditions

MicroRNAs (miRNAs) are small, non-coding RNA molecules that are mainly involved in translational repression by binding to specific messenger RNAs. Recently, miRNAs have emerged as biomarkers, relevant for a multitude of pathophysiological conditions, and cells can selectively sort miRNAs into extracellular vesicles for paracrine and endocrine effects. In the overall context of muscle-wasting conditions, a multitude of miRNAs has been implied as being responsible for the typical dysregulation of anabolic and catabolic pathways. In general, chronic muscle disorders are associated with the main characteristic of a substantial loss in muscle mass. Muscular dystrophies (MDs) are a group of genetic diseases that cause muscle weakness and degeneration. Typically, MDs are caused by mutations in those genes responsible for upholding the integrity of muscle structure and function. Recently, the dysregulation of miRNA levels in such pathological conditions has been reported. This revelation is imperative for both MDs and other muscle-wasting conditions, such as sarcopenia and cancer cachexia. The expression levels of miRNAs have immense potential for use as potential diagnostic, prognostic and therapeutic biomarkers. Understanding the role of miRNAs in muscle-wasting conditions may lead to the development of novel strategies for the improvement of patient management.

Profiles of microRNA in aqueous humor of normal tension glaucoma patients using RNA sequencing

We aimed to identify and compare microRNAs (miRNAs) from individual aqueous humor samples between normal-tension glaucoma (NTG) patients and normal controls. Aqueous humor (80 to 120 µl) was collected before cataract surgery. Six stable NTG patients and seven age-matched controls were included in the final analysis. RNA sequencing was conducted for RNA samples extracted from the 13 aqueous humor samples, and bioinformatics analysis was employed for the miRNA targets and related pathways. Two hundred and twenty-eight discrete miRNAs were detected in the aqueous humor and consistently expressed in all samples. Eight significantly upregulated miRNAs were found in the NTG patients compared to the controls (fold-change > 2, p < 0.05). They were hsa-let-7a-5p, hsa-let-7c-5p, hsa-let-7f-5p, hsa-miR-192-5p, hsa-miR-10a-5p, hsa-miR-10b-5p, hsa-miR-375, and hsa-miR-143-3p. These miRNAs were predicted to be associated with the biological processes of apoptosis, autophagy, neurogenesis, and aging in the gene ontology categories. The related Kyoto encyclopedia of genes and genomes pathways were extracellular matrix-receptor interaction, mucin-type O-glycan biosynthesis, biotin metabolism, and signaling pathways regulating the pluripotency of stem cells. The differentially expressed miRNA in the NTG samples compared to the controls suggest the possible roles of miRNA in the pathogenesis of NTG. The underlying miRNA-associated pathways further imply novel targets for the pathogenesis of NTG.

Deep Sequencing Discovery and Profiling of Known and Novel miRNAs Produced in Response to DNA Damage in Rice

Under extreme environmental conditions such as ultraviolet and ionizing radiation, plants may suffer DNA damage. If these damages are not repaired accurately and rapidly, they may lead to chromosomal abnormalities or even cell death. Therefore, organisms have evolved various DNA repair mechanisms to cope with DNA damage which include gene transcription and post-translational regulation. MicroRNA (miRNA) is a type of non-coding single-stranded RNA molecule encoded by endogenous genes. They can promote DNA damage repair by regulating target gene transcription. Here, roots from seedlings of the japonica rice cultivar ‘Yandao 8’ that were treated with bleomycin were collected for transcriptome-level sequencing, using non-treated roots as controls. A total of 14,716,232 and 17,369,981 reads mapping to miRNAs were identified in bleomycin-treated and control groups, respectively, including 513 known and 72 novel miRNAs. Compared with the control group, 150 miRNAs showed differential expression levels. Target predictions of these differentially expressed miRNAs yielded 8731 potential gene targets. KEGG annotation and a gene ontology analysis indicated that the highest-ranked target genes were classified into metabolic processes, RNA degradation, DNA repair, and so on. Notably, the DNA repair process was significantly enriched in both analyses. Among these differentially expressed miRNAs, 58 miRNAs and 41 corresponding potential target genes were predicted to be related to DNA repair. RT-qPCR results confirmed that the expression patterns of 20 selected miRNAs were similar to those from the sequencing results, whereas four miRNAs gave opposite results. The opposing expression patterns of several miRNAs with regards to their target genes relating to the DNA repair process were also validated by RT-qPCR. These findings provide valuable information for further functional studies of miRNA involvement in DNA damage repair in rice.

ALS-related FUS mutations alter axon growth in motoneurons and affect HuD/ELAVL4 and FMRP activity

Mutations in the RNA-binding protein (RBP) FUS have been genetically associated with the motoneuron disease amyotrophic lateral sclerosis (ALS). Using both human induced pluripotent stem cells and mouse models, we found that FUS-ALS causative mutations affect the activity of two relevant RBPs with important roles in neuronal RNA metabolism: HuD/ELAVL4 and FMRP. Mechanistically, mutant FUS leads to upregulation of HuD protein levels through competition with FMRP for HuD mRNA 3'UTR binding. In turn, increased HuD levels overly stabilize the transcript levels of its targets, NRN1 and GAP43. As a consequence, mutant FUS motoneurons show increased axon branching and growth upon injury, which could be rescued by dampening NRN1 levels. Since similar phenotypes have been previously described in SOD1 and TDP-43 mutant models, increased axonal growth and branching might represent broad early events in the pathogenesis of ALS.

Role of microRNA‑375‑3p‑mediated regulation in tinnitus development

Changes in the dorsal cochlear nucleus (DCN) following exposure to noise play an important role in the development of tinnitus. As the development of several diseases is known to be associated with microRNAs (miRNAs/miRs), the aim of the present study was to identify the miRNAs that may be implicated in pathogenic changes in the DCN, resulting in tinnitus. A previously developed tinnitus animal model was used for this study. The study consisted of four stages, including identification of candidate miRNAs involved in tinnitus development using miRNA microarray analysis, validation of miRNA expression using reverse transcription-quantitative PCR (RT-qPCR), evaluation of the effects of candidate miRNA overexpression on tinnitus development through injection of a candidate miRNA mimic or mimic negative control, and target prediction of candidate miRNAs using mRNA microarray analysis and western blotting. The miRNA microarray and RT-qPCR analyses revealed that miR-375-3p expression was significantly reduced in the tinnitus group compared with that in the non-tinnitus group. Additionally, miR-375-3p overexpression via injection of miR-375-3p mimic reduced the proportion of animals with persistent tinnitus. Based on mRNA microarray and western blot analyses, connective tissue growth factor (CTG.) was identified as a potential target for miR-375-3p. Thus, it was inferred that CTGF downregulation by miR-375-3p may weaken with the decrease in miRNA expression, and the increased pro-apoptotic activity of CTGF may result in more severe neuronal damage, contributing to tinnitus development. These findings are expected to contribute significantly to the development of a novel therapeutic approach to tinnitus, thereby bringing about a significant breakthrough in the treatment of this potentially debilitating condition.

The potential role of miRNA therapies in spinal muscle atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by low levels of full-length survival motor neuron (SMN) protein due to the loss of the survival motor neuron 1 (SMN1) gene and inefficient splicing of the survival motor neuron 2 (SMN2) gene, which mostly affects alpha motor neurons of the lower spinal cord. Despite the U.S. Food and Drug Administration (FDA) approved SMN-dependent therapies including Nusinersen, Zolgensma® and Evrysdi™, SMA is still a devastating disease as these existing expensive drugs may not be sufficient and thus, remains a need for additional therapies. The involvement of microRNAs (miRNAs) in SMA is expanding because miRNAs are important mediators of gene expression as each miRNA could target a number of genes. Hence, miRNA-based therapy could be utilized in treating this genetic disorder. However, the delivery of miRNAs into the target cells remains an obstacle in SMA, as there is no effective delivery system to date. This review highlights the potential strategies for intracellular miRNA delivery into target cells and current challenges in miRNA delivery. Furthermore, we provide the future prospects of miRNA-based therapeutic strategies in SMA.

MiR-375: A novel multifunctional regulator

MiR-375, a primitively described beta cell-specific miRNA, is confirmed to function as multi-functional regulator in diverse typical cellular pathways according to the follow-up researches. Based on the existing studies, miR-375 can regulate many functional genes and ectopic expressions of miR-375 are usually associated with pathological changes, and its expression regulation mechanism is mainly related to promoter methylation or circRNA. In this review, the regulatory functions of miR-375 in immunity, such as its relevance with macrophages, T helper cells and autoimmune diseases were briefly discussed. Also, the functions of miR-375 involved in inflammation, development and virus replication were reviewed. Finally, the mechanisms and application prospects of miR-375 in cancers were analyzed. Studies show that the application of miR-375 as therapeutic target and biomarker has a broad developing space in future. We hope this paper can provide reference for its further study.

Circulating microRNAs as potential biomarkers and therapeutic targets in spinal muscular atrophy

Spinal muscular atrophy (SMA), a leading genetic cause of infant death, is a neurodegenerative disease characterized by the selective loss of particular groups of motor neurons (MNs) in the anterior horn of the spinal cord with progressive muscle wasting. SMA is caused by a deficiency of the survival motor neuron (SMN) protein due to a homozygous deletion or mutation of the SMN1 gene. However, the molecular mechanisms whereby the SMN complex regulates MN functions are not fully elucidated. Emerging studies on SMA pathogenesis have turned the attention of researchers to RNA metabolism, given that increasingly identified SMN-associated modifiers are involved in both coding and non-coding RNA (ncRNA) processing. Among various ncRNAs, microRNAs (miRNAs) are the most studied in terms of regulation of posttranscriptional gene expression. Recently, the discovery that miRNAs are critical to MN function and survival led to the study of dysregulated miRNAs in SMA pathogenesis. Circulating miRNAs have drawn attention as a readily available biomarker due to their property of being clinically detectable in numerous human biofluids through non-invasive approaches. As there are recent promising findings from novel miRNA-based medicines, this article presents an extensive review of the most up-to-date studies connecting specific miRNAs to SMA pathogenesis and the potential applications of miRNAs as biomarkers and therapeutic targets for SMA.

AVPR1A main effect and OXTR-by-environment interplay in individual differences in depression level

Background

Multiple studies of depression indicated a significant role of gene-by-environment interactions; however, they are mainly limited to the examination of modulating effect of recent stressful life events. Other environmental factors occurring at different stages of ante- and postnatal development may affect the association between multiple genes and depression. The study aimed to analyze the main and haplotype-based effect of serotonergic system and HPA-axis gene polymorphisms on depression and to detect gene-by-environment interaction models explaining individual variance in depression in mentally healthy young adults from Russia.

Methods

Depression score was assessed using Beck Depression Inventory (BDI) in 623 healthy individuals (81% women; 17-25 years) of Caucasian origin (Russians, Tatars, Udmurts) from Russia. The main- and gene-based effects of 12 SNPs in SLC6A4 (5-HTTLPR, rs1042173), HTR2A (rs7322347), OXTR (rs7632287, rs2254298, rs13316193, rs53576, rs2228485, rs237911), AVPR1A (rs3803107, rs1042615), and AVPR1B (rs33911258) genes, and gene-by-environment interactions were tested with linear regression models (PLINK v.1.9) adjusted for multiple comparisons.

Results

We observed ethnicity-specific main effect of the AVPR1A rs3803107 (P = 0.003; P_FDR = 0.047) and gene-based effect of the OXTR gene (Р = 0.005; P_perm = 0.034) on BDI-measured depression, and modifying effect of paternal care on OXTR rs53576 (P = 0.004; P_FDR = 0.012) and birth order on OXTR rs237911 (P = 0.006; P_FDR = 0.018) association with depression level.

Limitations

A hypothesis driven candidate gene approach, which examined a limited number of genetic variants in a moderately large sample, was used.

Conclusions

Our preliminary findings indicate that familial environment may play a permissive role modulating the manifestation of OXTR-based depression variance in mentally healthy subjects.

Regulation of Skeletal Muscle Atrophy in Cachexia by MicroRNAs and Long Non-coding RNAs

Skeletal muscle atrophy is a common complication of cachexia, characterized by progressive bodyweight loss and decreased muscle strength, and it significantly increases the risks of morbidity and mortality in the population with atrophy. Numerous complications associated with decreased muscle function can activate catabolism, reduce anabolism, and impair muscle regeneration, leading to muscle wasting. microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), types of non-coding RNAs, are important for regulation of skeletal muscle development. Few studies have specifically identified the roles of miRNAs and lncRNAs in cellular or animal models of muscular atrophy during cachexia, and the pathogenesis of skeletal muscle wasting in cachexia is not entirely understood. To develop potential approaches to improve skeletal muscle mass, strength, and function, a more comprehensive understanding of the known key pathophysiological processes leading to muscular atrophy is needed. In this review, we summarize the known miRNAs, lncRNAs, and corresponding signaling pathways involved in regulating skeletal muscle atrophy in cachexia and other diseases. A comprehensive understanding of the functions and mechanisms of miRNAs and lncRNAs during skeletal muscle wasting in cachexia and other diseases will, therefore, promote therapeutic treatments for muscle atrophy.

Anti-NMDA Receptor Encephalitis, Vaccination and Virus

Anti-N-methyl-d-aspartate (Anti-NMDA) receptor encephalitis is an acute autoimmune disorder. The symptoms range from psychiatric symptoms, movement disorders, cognitive impairment, and autonomic dysfunction. Previous studies revealed that vaccination might induce this disease. A few cases were reported to be related to H1N1 vaccine, tetanus/diphtheria/pertussis and polio vaccine, and Japanese encephalitis vaccine. Although vaccination is a useful strategy to prevent infectious diseases, in a low risk, it may trigger serious neurological symptoms. In addition to anti-NMDA receptor encephalitis, other neurological diseases were reported to be associated with a number of vaccines. In this paper, the anti-NMDA receptor encephalitis cases related to a number of vaccines and other neurological symptoms that might be induced by these vaccines were reviewed. In addition, anti-NMDA receptor encephalitis cases that were induced by virus infection were also reviewed.

Elevated exosomal secretion of miR-124-3p from spinal neurons positively associates with disease severity in ALS

MicroRNAs (miRs) are powerful regulators of CNS development and diseases. Plasma and cerebrospinal fluid (CSF) miRs have recently been implicated as potential new sources for biomarker development. Previously we showed that miR-124-3p, an essential miR for neuronal identity, is highly abundant in neuronal exosomes and its expression decreases in spinal cord of ALS model SOD1G93A mice. In the current study, we found a disease associated reduction of miR-124-3p levels specifically in spinal neurons using in situ hybridization. By employing our recently developed exosome reporter mice in combination with sciatic nerve injections, we observed an increased association of miR-124-3p with spinal motor neuron-derived exosomes in SOD1G93A mice, even at the pre-symptomatic stage. Sciatic nerve injection delivered miR-124-3p is also more frequently localized outside of spinal motor neurons in SOD1G93A mice. Subsequent quantitative analysis of miR-124-3p levels in CSF exosomes from ALS patients found a significant correlation between CSF exosomal miR-124-3p levels and disease stage (indicated by the ALSFRS-R score) of (male) ALS patients. These results provide preliminary evidence to support the potential use of CSF exosomal miR-124-3p as a disease stage indicator in ALS.

ALS, a cellular whodunit on motor neuron degeneration

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that primarily targets motor neurons. Motor neurons from ALS patients show cytoplasmic inclusions that are reflective of an altered RNA metabolism and protein degradation. Causal gene mutations are found in all cell types even though patient motor neurons are by far the most susceptible to the degeneration. Using induced pluripotent stem cell (iPSC) technology, researchers have generated motor neurons with the same genotype as the patient including sporadic ones. They have also generated other cell types associated with the disease such as astrocytes, microglia and oligodendrocytes. These cells provide not only new insights on the mechanisms of the disease from the early stage, but also a platform for drug screening that has led to several clinical trials. This review examines the knowledge gained from iPSC studies using patient cells on the gene mutations and cellular networks in ALS and relevant experimental therapies.

Connecting RNA-Modifying Similarities of TDP-43, FUS, and SOD1 with MicroRNA Dysregulation Amidst A Renewed Network Perspective of Amyotrophic Lateral Sclerosis Proteinopathy

Beyond traditional approaches in understanding amyotrophic lateral sclerosis (ALS), multiple recent studies in RNA-binding proteins (RBPs)-including transactive response DNA-binding protein (TDP-43) and fused in sarcoma (FUS)-have instigated an interest in their function and prion-like properties. Given their prominence as hallmarks of a highly heterogeneous disease, this prompts a re-examination of the specific functional interrelationships between these proteins, especially as pathological SOD1-a non-RBP commonly associated with familial ALS (fALS)-exhibits similar properties to these RBPs including potential RNA-regulatory capabilities. Moreover, the cytoplasmic mislocalization, aggregation, and co-aggregation of TDP-43, FUS, and SOD1 can be identified as proteinopathies akin to other neurodegenerative diseases (NDs), eliciting strong ties to disrupted RNA splicing, transport, and stability. In recent years, microRNAs (miRNAs) have also been increasingly implicated in the disease, and are of greater significance as they are the master regulators of RNA metabolism in disease pathology. However, little is known about the role of these proteins and how they are regulated by miRNA, which would provide mechanistic insights into ALS pathogenesis. This review seeks to discuss current developments across TDP-43, FUS, and SOD1 to build a detailed snapshot of the network pathophysiology underlying ALS while aiming to highlight possible novel therapeutic targets to guide future research.

MicroRNA regulatory networks in the pathogenesis of sarcopenia

Sarcopenia is an age‐related disease characterized by disturbed homeostasis of skeletal muscle, leading to a decline in muscle mass and function. Loss of muscle mass and strength leads to falls and fracture, and is often accompanied by other geriatric diseases, including osteoporosis, frailty and cachexia, resulting in a general decrease in quality of life and an increase in mortality. Although the underlying mechanisms of sarcopenia are still not completely understood, there has been a marked improvement in the understanding of the pathophysiological changes leading to sarcopenia in recent years. The role of microRNAs (miRNAs), especially, has been clearer in skeletal muscle development and homeostasis. miRNAs form part of a gene regulatory network and have numerous activities in many biological processes. Intervention based on miRNAs may develop into an innovative treatment strategy to conquer sarcopenia. This review is divided into three sections: firstly, the latest understanding of the pathogenesis of sarcopenia is summarized; secondly, increasing evidence for the involvement of miRNAs in the regulation of muscle quantity or quality and muscle homeostasis is highlighted; and thirdly, the possibilities and limitations of miRNAs as a treatment for sarcopenia are explored.

miR-206 family is important for mitochondrial and muscle function, but not essential for myogenesis in vitro

miR-206, miR-1a-1, and miR-1a-2 are induced during differentiation of skeletal myoblasts and promote myogenesis in vitro. miR-206 is required for skeletal muscle regeneration in vivo. Although this miRNA family is hypothesized to play an essential role in differentiation, a triple knock-out (tKO) of the three genes has not been done to test this hypothesis. We report that tKO C2C12 myoblasts generated using CRISPR/Cas9 method differentiate despite the expected derepression of the miRNA targets. Surprisingly, their mitochondrial function is diminished. tKO mice demonstrate partial embryonic lethality, most likely due to the role of miR-1a in cardiac muscle differentiation. Two tKO mice survive and grow normally to adulthood with smaller myofiber diameter, diminished physical performance, and an increase in PAX7 positive satellite cells. Thus, unlike other miRNAs important in other differentiation pathways, the miR-206 family is not absolutely essential for myogenesis and is instead a modulator of optimal differentiation of skeletal myoblasts.

Up-regulation of microRNA-375 ameliorates the damage of dopaminergic neurons, reduces oxidative stress and inflammation in Parkinson's disease by inhibiting SP1

Background: This study is conducted to investigate the protective role of elevated microRNA-375 (miR-375) in dopaminergic neurons in Parkinson’s disease through down-regulating transcription factor specificity protein 1 (SP1).

Results: The successfully modeled rats with Parkinson’s disease showed aggregated neurobehavioral change, increased neuroinflammatory response and oxidative stress, and lowered dopamine content. Parkinson’s disease rats treated with overexpressed miR-375 displayed improved neurobehavioral change, ameliorated neuroinflammatory response and oxidative stress, heightened dopamine content and abated neuronal apoptosis by down-regulating SP1. Up-regulation of SP1 reversed the protective effect of upregulated miR-375 on Parkinson’s disease.

Conclusion: Up-regulation of miR-375 ameliorated the damage of dopaminergic neurons, reduced oxidative stress and inflammation in Parkinson’s disease by inhibiting SP1.

Methods: Parkinson’s disease rat model was established by targeted injection of 6-hydroxydopamine to damage the substantia nigra striatum. The successfully modeled Parkinson’s disease rats were intracerebroventricularly injected with miR-375 mimics or pcDNA3.1-SP1. The functions of miR-375 and SP1 in neurobehavioral change, neuroinflammatory response, oxidative stress, dopamine content and expression of apoptosis-related proteins in the substantia nigra of Parkinson’s disease rats were evaluated. The target relation of miR-375 and SP1 was confirmed by bioinformatics analysis and dual luciferase reporter gene assay.

Multifaceted roles of microRNAs: From motor neuron generation in embryos to degeneration in spinal muscular atrophy

Two crucial questions in neuroscience are how neurons establish individual identity in the developing nervous system and why only specific neuron subtypes are vulnerable to neurodegenerative diseases. In the central nervous system, spinal motor neurons serve as one of the best-characterized cell types for addressing these two questions. In this review, we dissect these questions by evaluating the emerging role of regulatory microRNAs in motor neuron generation in developing embryos and their potential contributions to neurodegenerative diseases such as spinal muscular atrophy (SMA). Given recent promising results from novel microRNA-based medicines, we discuss the potential applications of microRNAs for clinical assessments of SMA disease progression and treatment.

Serum Exosome MicroRNAs Predict Multiple Sclerosis Disease Activity after Fingolimod Treatment

We and others have previously demonstrated the potential for circulating exosome microRNAs to aid in disease diagnosis. In this study, we sought the possible utility of serum exosome microRNAs as biomarkers for disease activity in multiple sclerosis patients in response to fingolimod therapy. We studied patients with relapsing-remitting multiple sclerosis prior to and 6 months after treatment with fingolimod. Disease activity was determined using gadolinium-enhanced magnetic resonance imaging. Serum exosome microRNAs were profiled using next-generation sequencing. Data were analysed using univariate/multivariate modelling and machine learning to determine microRNA signatures with predictive utility. Accordingly, we identified 15 individual miRNAs that were differentially expressed in serum exosomes from post-treatment patients with active versus quiescent disease. The targets of these microRNAs clustered in ontologies related to the immune and nervous systems and signal transduction. While the power of individual microRNAs to predict disease status post-fingolimod was modest (average 77%, range 65 to 91%), several combinations of 2 or 3 miRNAs were able to distinguish active from quiescent disease with greater than 90% accuracy. Further stratification of patients identified additional microRNAs associated with stable remission, and a positive response to fingolimod in patients with active disease prior to treatment. Overall, these data underscore the value of serum exosome microRNA signatures as non-invasive biomarkers of disease in multiple sclerosis and suggest they may be used to predict response to fingolimod in future clinical practice. Additionally, these data suggest that fingolimod may have mechanisms of action beyond its known functions.

AAV9-mediated delivery of miR-23a reduces disease severity in Smn2B/-SMA model mice

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by deletions or mutations in survival motor neuron 1 (SMN1). The molecular mechanisms underlying motor neuron degeneration in SMA remain elusive, as global cellular dysfunction obscures the identification and characterization of disease-relevant pathways and potential therapeutic targets. Recent reports have implicated microRNA (miRNA) dysregulation as a potential contributor to the pathological mechanism in SMA. To characterize miRNAs that are differentially regulated in SMA, we profiled miRNA levels in SMA induced pluripotent stem cell (iPSC)-derived motor neurons. From this array, miR-23a downregulation was identified selectively in SMA motor neurons, consistent with previous reports where miR-23a functioned in neuroprotective and muscle atrophy-antagonizing roles. Reintroduction of miR-23a expression in SMA patient iPSC-derived motor neurons protected against degeneration, suggesting a potential miR-23a-specific disease-modifying effect. To assess this activity in vivo, miR-23a was expressed using a self-complementary adeno-associated virus serotype 9 (scAAV9) viral vector in the Smn2B/- SMA mouse model. scAAV9-miR-23a significantly reduced the pathology in SMA mice, including increased motor neuron size, reduced neuromuscular junction pathology, increased muscle fiber area, and extended survival. These experiments demonstrate that miR-23a is a novel protective modifier of SMA, warranting further characterization of miRNA dysfunction in SMA.

Deregulated miR-29b-3p Correlates with Tissue-Specific Activation of Intrinsic Apoptosis in An Animal Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is one of the most common incurable motor neuron disorders in adults. The majority of all ALS cases occur sporadically (sALS). Symptoms of ALS are caused by a progressive degeneration of motor neurons located in the motor cortex and spinal cord. The question arises why motor neurons selectively degenerate in ALS, while other cells and systems appear to be spared the disease. Members of the intrinsic apoptotic pathway are frequent targets of altered microRNA expression. Therefore, microRNAs and their effects on cell survival are subject of controversial debates. In this study, we investigated the expression of numerous members of the intrinsic apoptotic cascade by qPCR, western blot, and immunostaining in two different regions of the CNS of wobbler mice. Further we addressed the expression of miR-29b-3p targeting BMF, Bax, and, Bak, members of the apoptotic pathway. We show a tissue-specific differential expression of BMF, Bax, and cleaved-Caspase 3 in wobbler mice. An opposing regulation of miR-29b-3p expression in the cerebellum and cervical spinal cord of wobbler mice suggests different mechanisms regulating the intrinsic apoptotic pathway. Based on our findings, it could be speculated that miR-29b-3p might regulate antiapoptotic survival mechanisms in CNS areas that are not affected by neurodegeneration in the wobbler mouse ALS model.

RNA Dysregulation in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease and is characterized by the degeneration of upper and lower motor neurons. It has become increasingly clear that RNA dysregulation is a key contributor to ALS pathogenesis. The major ALS genes SOD1, TARDBP, FUS, and C9orf72 are involved in aspects of RNA metabolism processes such as mRNA transcription, alternative splicing, RNA transport, mRNA stabilization, and miRNA biogenesis. In this review, we highlight the current understanding of RNA dysregulation in ALS pathogenesis involving these major ALS genes and discuss the potential of therapeutic strategies targeting disease RNAs for treating ALS.

MicroRNAs as regulators of cell death mechanisms in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting upper and lower motor neurons (MNs), resulting in paralysis and precocious death from respiratory failure. Although the causes of ALS are incompletely understood, the role of alterations in RNA metabolism seems central. MicroRNAs (miRNAs) are noncoding RNAs implicated in the regulation of gene expression of many relevant physiological processes, including cell death. The recent model of programmed cell death (PCD) encompasses different mechanisms, from apoptosis to regulated necrosis (RN), in particular necroptosis. Both apoptosis and necroptosis play a significant role in the progressive death of MNs in ALS. In this review, we present key research related to miRNAs that modulate apoptosis and RN pathways in ALS. We also discuss whether these miRNAs represent potential targets for therapeutic development in patients.

Dysregulation of microRNA metabolism in motor neuron diseases: Novel biomarkers and potential therapeutics

In the last 15 years, several classes of small regulatory RNAs have been identified, uncovering the widespread impact of non-coding elements in the human genome on cell homeostasis and human diseases. MicroRNAs (miRNAs) are a family of small, non-coding RNAs, which exert silencing of mRNA targets in a sequence-dependent fashion. Many miRNAs are specifically expressed in the central nervous system, where they display roles in differentiation, neuronal survival, neuronal plasticity and learning. On the other hand, deregulated miRNA/mRNA expression networks are deeply involved in neurodegeneration. Recent findings suggest a role for miRNAs in the pathogenesis of motor neuron diseases. In particular, cell-specific changes in miRNA profile are involved in the motor neuron disease phenotype and might be implicated in their selective vulnerability. Exploitation of noncoding RNAs, in particular miRNAs, for therapeutic strategies is being assessed for implementing current therapies. In this regard, the neuroprotective potential of certain miRNAs could represent a promising potential tool to improve therapies for motor-neuron diseases. This review focuses on emerging roles of miRNAs in motor neuron diseases and on their impact on neuron life-span and integrity.

Mapping the Pax6 3' untranslated region microRNA regulatory landscape

BACKGROUND

PAX6 is a homeodomain transcription factor that acts in a highly dosage-sensitive manner to regulate the development and function of the eyes, nose, central nervous system, gut, and endocrine pancreas. Several individual microRNAs (miRNA) have been implicated in regulating PAX6 in different cellular contexts, but a more general view of how they contribute to the fine-tuning and homeostasis of PAX6 is poorly understood.

RESULTS

Here, a comprehensive analysis of the Pax6 3' untranslated region was performed to map potential miRNA recognition elements and served as a backdrop for miRNA expression profiling experiments to identify potential cell/tissue-specific miRNA codes. Pax6 3'UTR pull-down studies identified a cohort of miRNA interactors in pancreatic αTC1-6 cells that, based on the spacing of their recognition sites in the Pax6 3'UTR, revealed 3 clusters where cooperative miRNA regulation may occur. Some of these interacting miRNAs have been implicated in α cell function but have not previously been linked to Pax6 function and may therefore represent novel PAX6 regulators.

CONCLUSIONS

These findings reveal a regulatory landscape upon which miRNAs may participate in the developmental control, fine-tuning and/or homeostasis of PAX6 levels.

Comparison of multi-lineage differentiation of hiPSCs reveals novel miRNAs that regulate lineage specification

MicroRNAs (miRNAs) are known to be crucial players in governing the differentiation of human induced pluripotent stem cells (hiPSCs). Despite their utter importance, identifying key lineage specifiers among the myriads of expressed miRNAs remains challenging. We believe that the current practice in mining miRNA specifiers via delineating dynamic fold-changes only is inadequate. Our study, therefore, provides evidence to pronounce "lineage specificity" as another important attribute to qualify for these lineage specifiers. Adopted hiPSCs were differentiated into representative lineages (hepatic, nephric and neuronal) over all three germ layers whilst the depicted miRNA expression changes compiled into an integrated atlas. We demonstrated inter-lineage analysis shall aid in the identification of key miRNAs with lineage-specificity, while these shortlisted candidates were collectively known as "lineage-specific miRNAs". Subsequently, we followed through the fold-changes along differentiation via computational analysis to identify miR-192 and miR-372-3p, respectively, as representative candidate key miRNAs for the hepatic and nephric lineages. Indeed, functional characterization validated that miR-192 and miR-372-3p regulate lineage differentiation via modulation of the expressions of lineage-specific genes. In summary, our presented miRNA atlas is a resourceful ore for the mining of key miRNAs responsible for lineage specification.

Differential effects of chronic stress in young-adult and old female mice: cognitive-behavioral manifestations and neurobiological correlates

Stress-related psychopathology is highly prevalent among elderly individuals and is associated with detrimental effects on mood, appetite and cognition. Conversely, under certain circumstances repeated mild-to-moderate stressors have been shown to enhance cognitive performance in rodents and exert stress-inoculating effects in humans. As most stress-related favorable outcomes have been reported in adolescence and young-adulthood, this apparent disparity could result from fundamental differences in how aging organisms respond to stress. Furthermore, given prominent age-related alterations in sex hormones, the effect of chronic stress in aging females remains a highly relevant yet little studied issue. In the present study, female C57BL/6 mice aged 3 (young-adult) and 20-23 (old) months were subjected to 8 weeks of chronic unpredictable stress (CUS). Behavioral outcomes were measured during the last 3 weeks of the CUS protocol, followed by brain dissection for histological and molecular end points. We found that in young-adult female mice, CUS resulted in decreased anxiety-like behavior and enhanced cognitive performance, whereas in old female mice it led to weight loss, dysregulated locomotion and memory impairment. These phenotypes were paralleled by differential changes in the expression of hypothalamic insulin and melanocortin-4 receptors and were consistent with an age-dependent reduction in the dynamic range of stress-related changes in the hippocampal transcriptome. Supported by an integrated microRNA (miRNA)-mRNA expression analysis, the present study proposes that, when confronted with ongoing stress, neuroprotective mechanisms involving the upregulation of neurogenesis, Wnt signaling and miR-375 can be harnessed more effectively during young-adulthood. Conversely, we suggest that aging alters the pattern of immune activation elicited by stress. Ultimately, interventions that modulate these processes could reduce the burden of stress-related psychopathology in late life.

Transcription factor mechanisms guiding motor neuron differentiation and diversification

The embryonic generation of motor neurons is a complex process involving progenitor patterning, fate specification, differentiation, and maturation. Throughout this progression, the differential expression of transcription factors has served as our road map for the eventual cell fate of nascent motor neurons. Recent findings from in vivo and in vitro models of motor neuron development have expanded our understanding of how transcription factors govern motor neuron identity and their individual regulatory mechanisms. With the advent of next generation sequencing approaches, researchers now have unprecedented access to the gene regulatory dynamics involved in motor neuron development and are uncovering new connections linking neurodevelopment and neurodegenerative disease.

MicroRNA-365 modulates astrocyte conversion into neuron in adult rat brain after stroke by targeting Pax6

Reactive astrocytes induced by ischemia can transdifferentiate into mature neurons. This neurogenic potential of astrocytes may have therapeutic value for brain injury. Epigenetic modifications are widely known to involve in developmental and adult neurogenesis. PAX6, a neurogenic fate determinant, contributes to the astrocyte‐to‐neuron conversion. However, it is unclear whether microRNAs (miRs) modulate PAX6‐mediated astrocyte‐to‐neuron conversion. In the present study we used bioinformatic approaches to predict miRs potentially targeting Pax6, and transient middle cerebral artery occlusion (MCAO) to model cerebral ischemic injury in adult rats. These rats were given striatal injection of glial fibrillary acidic protein targeted enhanced green fluorescence protein lentiviral vectors (Lv‐GFAP‐EGFP) to permit cell fate mapping for tracing astrocytes‐derived neurons. We verified that miR‐365 directly targets to the 3′‐UTR of Pax6 by luciferase assay. We found that miR‐365 expression was significantly increased in the ischemic brain. Intraventricular injection of miR‐365 antagomir effectively increased astrocytic PAX6 expression and the number of new mature neurons derived from astrocytes in the ischemic striatum, and reduced neurological deficits as well as cerebral infarct volume. Conversely, miR‐365 agomir reduced PAX6 expression and neurogenesis, and worsened brain injury. Moreover, exogenous overexpression of PAX6 enhanced the astrocyte‐to‐neuron conversion and abolished the effects of miR‐365. Our results demonstrate that increase of miR‐365 in the ischemic brain inhibits astrocyte‐to‐neuron conversion by targeting Pax6, whereas knockdown of miR‐365 enhances PAX6‐mediated neurogenesis from astrocytes and attenuates neuronal injury in the brain after ischemic stroke. Our findings provide a foundation for developing novel therapeutic strategies for brain injury.

A Regulatory Circuitry Between Gria2, miR-409, and miR-495 Is Affected by ALS FUS Mutation in ESC-Derived Motor Neurons

Mutations in fused in sarcoma (FUS) cause amyotrophic lateral sclerosis (ALS). FUS is a multifunctional protein involved in the biogenesis and activity of several types of RNAs, and its role in the pathogenesis of ALS may involve both direct effects of disease-associated mutations through gain- and loss-of-function mechanisms and indirect effects due to the cross talk between different classes of FUS-dependent RNAs. To explore how FUS mutations impinge on motor neuron-specific RNA-based circuitries, we performed transcriptome profiling of small and long RNAs of motor neurons (MNs) derived from mouse embryonic stem cells carrying a FUS-P517L knock-in mutation, which is equivalent to human FUS-P525L, associated with a severe and juvenile-onset form of ALS. Combining ontological, predictive and molecular analyses, we found an inverse correlation between several classes of deregulated miRNAs and their corresponding mRNA targets in both homozygous and heterozygous P517L MNs. We validated a circuitry in which the upregulation of miR-409-3p and miR-495-3p, belonging to a brain-specific miRNA subcluster implicated in several neurodevelopmental disorders, produced the downregulation of Gria2, a subunit of the glutamate α‐amino‐3‐hydroxy‐5‐methyl-4-isoxazole propionic acid (AMPA) receptor with a significant role in excitatory neurotransmission. Moreover, we found that FUS was involved in mediating such miRNA repression. Gria2 alteration has been proposed to be implicated in MN degeneration, through disturbance of Ca²⁺ homeostasis, which triggers a cascade of damaging “excitotoxic” events. The molecular cross talk identified highlights a role for FUS in excitotoxicity and in miRNA-dependent regulation of Gria2. This circuitry also proved to be deregulated in heterozygosity, which matches the human condition perfectly.

Astrocyte-produced miR-146a as a mediator of motor neuron loss in spinal muscular atrophy

Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, is caused by the loss of the survival motor neuron-1 (SMN1) gene, which leads to motor neuron loss, muscle atrophy, respiratory distress, and death. Motor neurons exhibit the most profound loss, but the mechanisms underlying disease pathogenesis are not fully understood. Recent evidence suggests that motor neuron extrinsic influences, such as those arising from astrocytes, contribute to motor neuron malfunction and loss. Here we investigated both loss-of-function and toxic gain-of-function astrocyte mechanisms that could play a role in SMA pathology. We had previously found that glial derived neurotrophic factor (GDNF) is reduced in SMA astrocytes. However, reduced GDNF expression does not play a major role in SMA pathology as viral-mediated GDNF re-expression did not improve astrocyte function or motor neuron loss. In contrast, we found that SMA astrocytes increased microRNA (miR) production and secretion compared to control astrocytes, suggesting potential toxic gain-of-function properties. Specifically, we found that miR-146a was significantly upregulated in SMA induced pluripotent stem cell (iPSC)-derived astrocytes and SMNΔ7 mouse spinal cord. Moreover, increased miR-146a was sufficient to induce motor neuron loss in vitro, whereas miR-146a inhibition prevented SMA astrocyte-induced motor neuron loss. Together, these data indicate that altered astrocyte production of miR-146a may be a contributing factor in astrocyte-mediated SMA pathology.

MiR-375 attenuates injury of cerebral ischemia/reperfusion via targetting Ctgf

Ischemic stroke is the leading cause of disability and deaths worldwide. MiRNAs have been shown to play an important role in development and pathogenesis of the nervous system. However, the precise function and mechanism of miRNAs are not fully understood in the brain injury induced by ischemia/reperfusion (I/R). Herein, our study showed that miR-375 expression was significantly down-regulated in the rat I/R brain. With the in vivo and in vitro I/R stroke models, we found that miR-375 mimic provides significant protection from injury to cerebral I/R, which is reflected by reduced infarct volumes and cell apoptosis, and increased proliferation and migration of PC12 cells. Mechanistically, our findings showed that miR-375 binds to 3′-UTR region of Ctgf mRNA, subsequently leading to the decreased expression of Ctgf in the I/R brain. Furthermore, we showed that miR-375/Ctgf-mediated protective effects are associated with p21/PI3K/Akt signaling pathways. Our findings thus provide a new insight into the mechanism of cerebral I/R injury and pave a potential new way for the therapy of cerebral I/R injury.

Overexpression of microRNA-375 impedes platelet-derived growth factor-induced proliferation and migration of human fetal airway smooth muscle cells by targeting Janus kinase 2

The abnormal proliferation and migration of airway smooth muscle (ASM) cells play a critical role in airway remodeling during the development of asthma. MicroRNAs (miRNAs) have emerged as critical regulators of ASM cell proliferation and migration in airway remodeling. In this study, we aimed to investigate the potential role of miR-375 in the regulation of platelet-derived growth factor (PDGF)-induced fetal ASM cell proliferation and migration. Our results showed that miR-375 expression was significantly decreased in fetal ASM cells that were treated with PDGF. Functional data showed that overexpression of miR-375 inhibited the proliferation and migration of fetal ASM cells, whereas inhibition of miR-375 enhanced the proliferation and migration of fetal ASM cells. The results of bioinformatics analysis and a dual-luciferase reporter assay showed that miR-375 binds directly to the 3'-untranslated region of Janus kinase 2 (JAK2). Further data confirmed that miR-375 negatively regulates the expression of JAK2 in fetal ASM cells. Moreover, miR-375 also impeded the PDGF-induced activation of signal transducer and activator of transcription 3 (STAT3) in fetal ASM cells. However, restoration of JAK2 expression partially reversed the inhibitory effect of miR-375 on fetal ASM cell proliferation and migration. Overall, our results demonstrate that miR-375 inhibits fetal ASM cell proliferation and migration by targeting JAK2/STAT3 signaling. Our study provides a potential therapeutic target for the development of novel treatment strategies for pediatric asthma.

miRNA in spinal muscular atrophy pathogenesis and therapy

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease characterized by the selective death of lower motor neurons in the brain stem and spinal cord. SMA is caused by mutations in the survival motor neuron 1 gene (SMN1), leading to the reduced expression of the full-length SMN protein. microRNAs (miRNAs) are small RNAs that regulate post-transcriptional gene expression. Recent findings have suggested an important role for miRNAs in the pathogenesis of motor neuron diseases, including SMA. Motor neuron-specific miRNA dysregulation in SMA might be implicated in their selective vulnerability. In this study, we discuss recent findings regarding the consequences of SMN defects on miRNAs and their target mRNAs in motor neurons. Taken together, these data suggest that cell-specific changes in miRNAs are not only involved in the SMA motor neuron phenotype but can also be used as biomarkers and therapeutic targets.