The role of miRNA in motor neuron disease

Mechanistic Evaluation of miRNAs and Their Targeted Genes in the Pathogenesis and Therapeutics of Parkinson's Disease

MicroRNA (miRNA) are usually 18-25 nucleotides long non-coding RNA targeting post-transcriptional regulation of genes involved in various biological processes. The function of miRNA is essential for maintaining a homeostatic cellular condition, regulating autophagy, cellular motility, and inflammation. Dysregulation of miRNA is responsible for multiple disorders, including neurodegeneration, which has emerged as a severe problem in recent times and has verified itself as a life-threatening condition that can be understood by the continuous destruction of neurons affecting various cognitive and motor functions. Parkinson's disease (PD) is the second most common, permanently debilitating neurodegenerative disorder after Alzheimer's, mainly characterized by uncontrolled tremor, stiffness, bradykinesia or akinesia (slowness in movement), and post-traumatic stress disorder. PD is mainly caused by the demolition of the primary dopamine neurotransmitter secretory cells and dopaminergic or dopamine secretory neurons in the substantia nigra pars compacta of the midbrain, which are majorly responsible for motor functions. In this study, a systematic evaluation of research articles from year 2017 to 2022 was performed on multiple search engines, and lists of miRNA being dysregulated in PD in different body components were generated. This study highlighted miR-7, miR-124, miR-29 family, and miR-425, showing altered expression levels during PD's progression, further regulating the expression of multiple genes responsible for PD.

The role of microRNAs in the pathophysiology of human central nervous system: A focus on neurodegenerative diseases

microRNAs (miRNAs) are suggested to play substantial roles in regulating the development and various physiologic functions of the central nervous system (CNS). These include neurogenesis, cell fate and differentiation, morphogenesis, formation of dendrites, and targeting non-neural mRNAs. Notably, deregulation of an increasing number of miRNAs is associated with several neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and CNS tumors. They are particularly known to affect the amyloid β (Aβ) cleavage and accumulation, tau protein homeostasis, and expression of alpha-synuclein (α-syn), Parkin, PINK1, and brain-derived neurotrophic factor (BDNF) that play pivotal roles in the pathogenesis of neurodegenerative diseases. These include miR-16, miR-17-5p, miR-20a, miR-106a, miR-106b, miR-15a, miR-15b, miR-103, miR-107, miR-298, miR-328, miR-195, miR-485, and miR-29. In CNS tumors, several miRNAs, including miR-31, miR-16, and miR-21 have been identified to modulate tumorigenesis through impacting tumor invasion and apoptosis. In this review article, we have a look at the recent advances on our knowledge about the role of miRNAs in human brain development and functions, neurodegenerative diseases, and their clinical potentials.

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.

Downexpression of miR-200c-3p Contributes to Achalasia Disease by Targeting the PRKG1 Gene

Achalasia is an esophageal smooth muscle motility disorder with unknown pathogenesis. Taking into account our previous results on the downexpression of miR-200c-3p in tissues of patients with achalasia correlated with an increased expression of PRKG1, SULF1, and SYDE1 genes, our aim was to explore the unknown biological interaction between these genes and human miR-200c-3p and if this relation could unravel their functional role in the etiology of achalasia. To search for putative miR-200c-3p binding sites in the 3'-UTR of PRKG1, SULF1 and SYDE1, a bioinformatics tool was used. To test whether PRKG1, SULF1, and SYDE1 are targeted by miR-200c-3p, a dual-luciferase reporter assay and quantitative PCR on HEK293 and fibroblast cell lines were performed. To explore the biological correlation between PRKG1 and miR-200c-3p, an immunoblot analysis was carried out. The overexpression of miR-200c-3p reduced the luciferase activity in cells transfected with a luciferase reporter containing a fragment of the 3'-UTR regions of PRKG1, SULF1, and SYDE1 which included the miR-200c-3p seed sequence. The deletion of the miR-200c-3p seed sequence from the 3'-UTR fragments abrogated this reduction. A negative correlation between miR-200c-3p and PRKG1, SULF1, and SYDE1 expression levels was observed. Finally, a reduction of the endogenous level of PRKG1 in cells overexpressing miR-200c-3p was detected. Our study provides, for the first time, functional evidence about the PRKG1 gene as a direct target and SULF1 and SYDE1 as potential indirect substrates of miR-200c-3p and suggests the involvement of NO/cGMP/PKG signaling in the pathogenesis of achalasia.

Mitochondrial Dysfunction in Cyanotic Congenital Heart Disease: A Promising Therapeutic Approach for the Future

Congenital heart disease (CHD) is one of the most specific and yet challenging fields of heart surgery. Apart from the known clinical approaches, including surgery, a significant scale of regenerative therapeutic options is available, which increase the number of cardiomyocytes and restore cardiac function. Although it has been revealed in recent years that mitochondrial transplantation can be used as a promising treatment option in this disease group, there is no clinical evidence for the significance of mitochondrial function in myocardial tissue of patients with CHD regarding cardiac surgery. In this study, mitochondrial morphology and function, myocardial fibrosis, and myocyte atypia were evaluated in myocardial biopsy tissue of pediatric patients with cyanotic and acyanotic CHD, five from each group. After histopathological evaluation of myocardial tissue specimens, mitochondrial morphology and network were analyzed by immunofluorescence staining using an anti-Tom20 antibody, electron transport chain complexes of myocardium were examined by cytochrome c oxidase/succinate dehydrogenase staining, and the amount of ATP was measured by bioluminescence assay. In addition, cardiac markers have been tested to be reviewed as a potential indicator for postoperative follow-up. Myocyte atypia and fibrosis were classified on a scale of 1 to 4. In this study, unlike patients with acyanotic CHD, alterations in mitochondrial network and reduction in ATP production were detected in all pediatric patients with cyanotic CHD. A statistically significant correlation was also determined between mitochondrial dysfunction and cardiac markers. These findings may be assumed as a promising pathway for evaluating the relationship between mitochondrial dysfunction and cyanotic CHD.

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.

MicroRNA expression in animal models of amyotrophic lateral sclerosis and potential therapeutic approaches

A review of recent animal models of amyotrophic lateral sclerosis showed a large number of miRNAs had altered levels of expression in the brain and spinal cord, motor neurons of spinal cord and brainstem, and hypoglossal, facial, and red motor nuclei and were mostly upregulated. Among the miRNAs found to be upregulated in two of the studies were miR-21, miR-155, miR-125b, miR-146a, miR-124, miR-9, and miR-19b, while those downregulated in two of the studies included miR-146a, miR-29, miR-9, and miR-125b. A change of direction in miRNA expression occurred in some tissues when compared (e.g., miR-29b-3p in cerebellum and spinal cord of wobbler mice at 40 days), or at different disease stages (e.g., miR-200a in spinal cord of SOD1(G93A) mice at 95 days vs. 108 and 112 days). In the animal models, suppression of miR-129-5p resulted in increased lifespan, improved muscle strength, reduced neuromuscular junction degeneration, and tended to improve motor neuron survival in the SOD1(G93A) mouse model. Suppression of miR-155 was also associated with increased lifespan, while lowering of miR-29a tended to improve lifespan in males and increase muscle strength in SOD1(G93A) mice. Overexpression of members of miR-17~92 cluster improved motor neuron survival in SOD1(G93A) mice. Treatment with an artificial miRNA designed to target hSOD1 increased lifespan and improved muscle strength in SOD1(G93A) animals. Further studies with animal models of amyotrophic lateral sclerosis are warranted to validate these findings and identify specific miRNAs whose suppression or directed against hSOD1 results in increased lifespan, improved muscle strength, reduced neuromuscular junction degeneration, and improved motor neuron survival in SOD1(G93A) animals.

Role of miRNAs in Neurodegeneration: From Disease Cause to Tools of Biomarker Discovery and Therapeutics

Neurodegenerative diseases originate from neuronal loss in the central nervous system (CNS). These debilitating diseases progress with age and have become common due to an increase in longevity. The National Institute of Environmental Health Science’s 2021 annual report suggests around 6.2 million Americans are living with Alzheimer’s disease, and there is a possibility that there will be 1.2 million Parkinson’s disease patients in the USA by 2030. There is no clear-cut universal mechanism for identifying neurodegenerative diseases, and therefore, they pose a challenge for neurobiology scientists. Genetic and environmental factors modulate these diseases leading to familial or sporadic forms. Prior studies have shown that miRNA levels are altered during the course of the disease, thereby suggesting that these noncoding RNAs may be the contributing factor in neurodegeneration. In this review, we highlight the role of miRNAs in the pathogenesis of neurodegenerative diseases. Through this review, we aim to achieve four main objectives: First, we highlight how dysregulation of miRNA biogenesis led to these diseases. Second, we highlight the computational or bioinformatics tools required to identify the putative molecular targets of miRNAs, leading to biological molecular pathways or mechanisms involved in these diseases. Third, we focus on the dysregulation of miRNAs and their target genes leading to several neurodegenerative diseases. In the final section, we highlight the use of miRNAs as potential diagnostic biomarkers in the early asymptomatic preclinical diagnosis of these age-dependent debilitating diseases. Additionally, we discuss the challenges and advances in the development of miRNA therapeutics for brain targeting. We list some of the innovative strategies employed to deliver miRNA into target cells and the relevance of these viral and non-viral carrier systems in RNA therapy for neurodegenerative diseases. In summary, this review highlights the relevance of studying brain-enriched miRNAs, the mechanisms underlying their regulation of target gene expression, their dysregulation leading to progressive neurodegeneration, and their potential for biomarker marker and therapeutic intervention. This review thereby highlights ways for the effective diagnosis and prevention of these neurodegenerative disorders in the near future.

The Biogenesis of miRNAs and Their Role in the Development of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that affects upper and lower motor neurons. As there is no effective treatment for ALS, it is particularly important to screen key gene therapy targets. The identifications of microRNAs (miRNAs) have completely changed the traditional view of gene regulation. miRNAs are small noncoding single-stranded RNA molecules involved in the regulation of post-transcriptional gene expression. Recent advances also indicate that miRNAs are biomarkers in many diseases, including neurodegenerative diseases. In this review, we summarize recent advances regarding the mechanisms underlying the role of miRNAs in ALS pathogenesis and its application to gene therapy for ALS. The potential of miRNAs to target diverse pathways opens a new avenue for ALS therapy.

Dysregulation of Muscle-Specific MicroRNAs as Common Pathogenic Feature Associated with Muscle Atrophy in ALS, SMA and SBMA: Evidence from Animal Models and Human Patients

Motor neuron diseases (MNDs) are neurodegenerative disorders characterized by upper and/or lower MN loss. MNDs include amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and spinal and bulbar muscular atrophy (SBMA). Despite variability in onset, progression, and genetics, they share a common skeletal muscle involvement, suggesting that it could be a primary site for MND pathogenesis. Due to the key role of muscle-specific microRNAs (myomiRs) in skeletal muscle development, by real-time PCR we investigated the expression of miR-206, miR-133a, miR-133b, and miR-1, and their target genes, in G93A-SOD1 ALS, Δ7SMA, and KI-SBMA mouse muscle during disease progression. Further, we analyzed their expression in serum of SOD1-mutated ALS, SMA, and SBMA patients, to demonstrate myomiR role as noninvasive biomarkers. Our data showed a dysregulation of myomiRs and their targets, in ALS, SMA, and SBMA mice, revealing a common pathogenic feature associated with muscle impairment. A similar myomiR signature was observed in patients’ sera. In particular, an up-regulation of miR-206 was identified in both mouse muscle and serum of human patients. Our overall findings highlight the role of myomiRs as promising biomarkers in ALS, SMA, and SBMA. Further investigations are needed to explore the potential of myomiRs as therapeutic targets for MND treatment.

MiRNA-disease association prediction via hypergraph learning based on high-dimensionality features

Background

MicroRNAs (miRNAs) have been confirmed to have close relationship with various human complex diseases. The identification of disease-related miRNAs provides great insights into the underlying pathogenesis of diseases. However, it is still a big challenge to identify which miRNAs are related to diseases. As experimental methods are in general expensive and time‐consuming, it is important to develop efficient computational models to discover potential miRNA-disease associations.

Methods

This study presents a novel prediction method called HFHLMDA, which is based on high-dimensionality features and hypergraph learning, to reveal the association between diseases and miRNAs. Firstly, the miRNA functional similarity and the disease semantic similarity are integrated to form an informative high-dimensionality feature vector. Then, a hypergraph is constructed by the K-Nearest-Neighbor (KNN) method, in which each miRNA-disease pair and its k most relevant neighbors are linked as one hyperedge to represent the complex relationships among miRNA-disease pairs. Finally, the hypergraph learning model is designed to learn the projection matrix which is used to calculate uncertain miRNA-disease association score.

Result

Compared with four state-of-the-art computational models, HFHLMDA achieved best results of 92.09% and 91.87% in leave-one-out cross validation and fivefold cross validation, respectively. Moreover, in case studies on Esophageal neoplasms, Hepatocellular Carcinoma, Breast Neoplasms, 90%, 98%, and 96% of the top 50 predictions have been manually confirmed by previous experimental studies.

Conclusion

MiRNAs have complex connections with many human diseases. In this study, we proposed a novel computational model to predict the underlying miRNA-disease associations. All results show that the proposed method is effective for miRNA–disease association predication.

MicroRNAs mediate precise control of spinal interneuron populations to exert delicate sensory-to-motor outputs

Although the function of microRNAs (miRNAs) during embryonic development has been intensively studied in recent years, their postnatal physiological functions remain largely unexplored due to inherent difficulties with the presence of redundant paralogs of the same seed. Thus, it is particularly challenging to uncover miRNA functions at neural circuit level since animal behaviors would need to be assessed upon complete loss of miRNA family functions. Here, we focused on the neural functions of MiR34/449 that manifests a dynamic expression pattern in the spinal cord from embryonic to postnatal stages. Our behavioral assays reveal that the loss of MiR34/449 miRNAs perturb thermally induced pain response thresholds and compromised delicate motor output in mice. Mechanistically, MiR34/449 directly target Satb1 and Satb2 to fine-tune the precise number of a sub-population of motor synergy encoder (MSE) neurons. Thus, MiR34/449 fine-tunes optimal development of Satb1/2^on interneurons in the spinal cord, thereby refining explicit sensory-to-motor circuit outputs.

The spinal cord is an information superhighway that connects the body with the brain. There, circuits of neurons process information from the brain before sending commands to muscles to generate movement. Each spinal cord circuit contains many types of neurons, whose identity is defined by the set of genes that are active or ‘expressed’ in each cell.

When a gene is turned on, its DNA sequence is copied to produce a messenger RNA (mRNA), a type of molecule that the cell then uses as a template to produce a protein. MicroRNAs (or miRNAs), on the other hand, are tiny RNA molecules that help to regulate gene expression by binding to and ‘deactivating’ specific mRNAs, stopping them from being used to make proteins.

Mammalian cells contain thousands of types of microRNAs, many of which have unknown roles: this includes MiR34/449, a group of six microRNAs found mainly within the nervous system. By using genetic technology to delete this family from the mouse genome, Chang et al. now show that MiR34/449 has a key role in regulating spinal cord circuits.

The first clue came from discovering that mice without the MiR34/449 family had unusual posture and a tendency to walk on tiptoe. The animals were also more sensitive to heat, flicking their tails away from a heat source more readily than control mice.

At a finer level, the spinal cords of the mutants contained greater numbers of cells in which two genes, Satb1 and Satb2, were turned on. Compared to their counterparts in control mice, the Satb1/2-positive neurons also showed differences in the rest of the genes they expressed. In essence, these neurons had a different genetic profile in MiR34/449 mutant mice, therefore disrupting the neural circuit they belong to.

Based on these findings, Chang et al. propose that in wild-type mice, the MiR34/449 family fine-tunes the expression of Satb1/2 in the spinal cord during development. In doing so, it regulates the formation of the spinal cord circuits that help to control movement. More generally, these results provide clues about how miRNAs help to determine cell identities; further studies could then examine whether other miRNAs contribute to the development and maintenance of neuronal circuits.

The microRNA-195 - BDNF pathway and cognitive deficits in schizophrenia patients with minimal antipsychotic medication exposure

Cognitive impairment is a core characteristic of schizophrenia, but its underlying neural mechanisms remain poorly understood. Reduced brain-derived neurotrophic factor (BDNF), a protein critical for neural plasticity and synaptic signaling, is one of the few molecules consistently associated with cognitive deficits in schizophrenia although the etiological pathway leading to BDNF reduction in schizophrenia is unclear. We examined microRNA-195 (miR-195), a known modulator of BDNF protein expression, as a potential mechanistic component. One-hundred and eighteen first-episode patients with schizophrenia either antipsychotic medication-naïve or within two weeks of antipsychotic medication exposure and forty-seven age- and sex-matched healthy controls were enrolled. MiR-195 and BDNF mRNA and BDNF protein levels in peripheral blood were tested. Cognitive function was assessed using the MATRICS Consensus Cognitive Battery (MCCB). MiR-195 was significantly higher (p = 0.01) whereas BDNF mRNA (p < 0.001) and protein (p = 0.016) levels were significantly lower in patients compared with controls. Higher miR-195 expression was significantly correlated to lower BDNF protein levels in patients (partial r = -0.28, p = 0.003) and lower BDNF protein levels were significantly associated with poorer overall cognitive performance by MCCB and also in speed of processing, working memory, and attention/vigilance domains composite score (p = 0.002-0.004). The subgroup of patients with high miR-195 and low BDNF protein showed the lowest level of cognitive functions, and miR-195 showed significant mediation effects on cognitive functions through BDNF protein. Elevated miR-195 may play a role in regulating BDNF protein expression thereby influencing cognitive impairments in schizophrenia, suggesting that development of cognition enhancing treatment for schizophrenia may consider a micro-RNA based strategy.

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.

The conserved microRNA miR-210 regulates lipid metabolism and photoreceptor maintenance in the Drosophila retina

Increasing evidence suggests that miRNAs play important regulatory roles in the nervous system. However, the molecular mechanisms of how specific miRNAs affect neuronal development and functions remain less well understood. In the present study, we provide evidence that the conserved microRNA miR-210 regulates lipid metabolism and prevents neurodegeneration in the Drosophila retina. miR-210 is specifically expressed in the photoreceptor neurons and other sensory organs. Genetic deletion of miR-210 leads to lipid droplet accumulation and photoreceptor degeneration in the retina. These effects are associated with abnormal activation of the Drosophila sterol regulatory element-binding protein signaling. We further identify the acetyl-coenzyme A synthetase (ACS) as one functionally important target of miR-210 in this context. Reduction of ACS in the miR-210 mutant background suppresses the neurodegeneration defects, suggesting that miR-210 acts through regulation of the ACS transcript. Together, these results reveal an unexpected role of miR-210 in controlling lipid metabolism and neuronal functions.

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.

Circulating MicroRNAs as Diagnostic Biomarkers for Motor Neuron Disease

Motor neuron disease (MND) is a kind of neurodegenerative disease that selectively invades spinal cord anterior horn cells, brainstem motor neurons, cortical pyramidal cells and the pyramidal tract. The main clinical features are the symptoms and signs of impaired upper and lower motor neurons, manifested as muscle weakness, atrophy and pyramidal tract signs. Histopathology has shown the disappearance of pyramidal cells in the motor cortex, loss of motor neurons in the anterior horn of the spinal cord and brainstem, and degeneration of the corticospinal tract. Due to the lack of effective treatment methods, the prognosis is generally poor, so it is of great significance to confirm the diagnosis early by various means. However, the current diagnosis of MND mainly relies on the combination of clinical manifestations and neurophysiological examinations, lacking effective means of early diagnosis. Circulating microRNA (CmiRNA) is a kind of stable miRNA molecule in serum, plasma and other body fluids, which has the characteristics of distinct differential expression, sensitive detection and convenient sample collection. As a possible new biomarker of MND, CmiRNA can not only reveal the pathophysiological process of MND, but also monitor disease progression and response to drug therapy. With the development of miRNA detection technology, more and more CmiRNAs as biomarkers with potential diagnostic value have been investigated. In this review, we explored the possibility of circulating samples as different sources of biomarkers for the diagnosis of MND, analyzing the progress of CmiRNA detection techniques, and presenting potential diagnostic MND biomarkers that have been reported.

Downregulation of miR-335-5P in Amyotrophic Lateral Sclerosis Can Contribute to Neuronal Mitochondrial Dysfunction and Apoptosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease for which the pathophysiological mechanisms of motor neuron loss are not precisely clarified. Environmental and epigenetic mechanisms such as microRNAs (miRNAs) could have a role in disease progression. We studied the expression pattern of miRNAs in ALS serum from 60 patients and 29 healthy controls. We also analyzed how deregulated miRNAs found in serum affected cellular pathways such as apoptosis, autophagy and mitochondrial physiology in SH-SY5Y cells. We found that miR-335-5p was downregulated in ALS serum. SH-SY5Y cells were transfected with a specific inhibitor of miR-335-5p and showed abnormal mitochondrial morphology, with an increment of reactive species of oxygen and superoxide dismutase activity. Pro-apoptotic caspases-3 and 7 also showed an increased activity in transfected cells. The downregulation of miR-335-5p, which has an effect on mitophagy, autophagy and apoptosis in SH-SY5Y neuronal cells could have a role in the motor neuron loss observed in ALS.

miR-206 Reduces the Severity of Motor Neuron Degeneration in the Facial Nuclei of the Brainstem in a Mouse Model of SMA

Spinal muscular atrophy (SMA) is a severe neuromuscular disease affecting infants caused by alterations of the survival motor neuron gene, which results in progressive degeneration of motor neurons (MNs). Although an effective treatment for SMA patients has been recently developed, the molecular pathway involved in selective MN degeneration has not been yet elucidated. In particular, miR-206 has been demonstrated to play a relevant role in the regeneration of neuromuscular junction in several MN diseases, and particularly it is upregulated in the quadriceps, tibialis anterior, spinal cord, and serum of SMA mice. In the present paper, we demonstrated that miR-206 was transiently upregulated also in the brainstem of the mouse model of SMA, SMAΔ7, in the early phase of the disease paralleling MN degeneration and was down-regulated in the late symptomatic phase. To prevent this downregulation, we intracerebroventricularly injected miR-206 in SMA pups, demonstrating that miR-206 reduced the severity of SMA pathology, slowing down disease progression, increasing survival rate, and improving behavioral performance of mice. Interestingly, exogenous miRNA-206-induced upregulation caused a reduction of the predicted target sodium calcium exchanger isoform 2, NCX2, one of the main regulators of intracellular [Ca²⁺] and [Na⁺]. Therefore, we hypothesized that miR-206 might exert part of its neuroprotective effect modulating NCX2 expression in SMA disease.

Comparative proteomes change and possible role in different pathways of microRNA-21a-5p in a mouse model of spinal cord injury

Our previous study found that microRNA-21a-5p (miR-21a-5p) knockdown could improve the recovery of motor function after spinal cord injury in a mouse model, but the precise molecular mechanism remains poorly understood. In this study, a modified Allen's weight drop was used to establish a mouse model of spinal cord injury. A proteomics approach was used to understand the role of differential protein expression with miR-21a-5p knockdown, using a mouse model of spinal cord injury without gene knockout as a negative control group. We found that after introducing miR-21a-5p knockdown, proteins that played an essential role in the regulation of inflammatory processes, cell protection against oxidative stress, cell redox homeostasis, and cell maintenance were upregulated compared with the negative control group. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis identified enriched pathways in both groups, such as the oxidative phosphorylation pathway, which is relevant to Parkinson's disease, Huntington's disease, Alzheimer's disease, and cardiac muscle contraction. We also found that miR-21a-5p could be a potential biomarker for amyotrophic lateral sclerosis, as miR-21a-5p becomes deregulated in this pathway. These results indicate successful detection of some important proteins that play potential roles in spinal cord injury. Elucidating the relationship between these proteins and the recovery of spinal cord injury will provide a reference for future research of spinal cord injury biomarkers. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Shandong University of China on March 5, 2014.

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.

MiR-206 inhibits epilepsy and seizure-induced brain injury by targeting CCL2

To determine the function of miR-206 in epilepsy. Epileptic rat model was established by intra-amygdala injection of kainic acid (KA). Expression levels of miR-206, C-C Motif Chemokine Ligand 2 (CCL2) and interleukin-1β (Il-1β) in hippocampus tissues was measured by reverse transcription-quantitative PCR (RT-qPCR) and western blot. Dual luciferase reporter assay was performed to determine the binding of miR-206 to 3' untranslated region (UTR) of CCL2. Finally, brain waves were recorded and Hematoxylin and eosin (HE) staining and Nissl's staining were performed on the epileptic rat injected with LPS, miR-206 agomir, adeno-associated virus (AAV) expressed CCL2 alone or in combination. Expression of miR-206 was specially decreased in hippocampus tissues compared to cortex in response to KA induced pathologic brain activity. Enforced expression of miR-206 by injection miR-206 agomir not only decreased seizure activity, but also protected KA-induced neuronal loss. And enforced expression of miR-206 suppressed increase of C-C Motif Chemokine Ligand 2 (CCL2) and interleukin-1β (Il-1β) which were induced by injection of KA or KA combined with lipopolysaccharide (LPS). Further more, results of dual luciferase reporter assay confirmed CCL2 was a target of miR-206. Finally, co-injection adeno-associated virus (AAV) expressed CCL2 with miR-206 agomir abolished the function of miR-206 agomir. Taken together, our results showed that expression of miR-206 could inhibit seizure-induced brain injury by targeting CCL2. Our results showed that expression of miR-206 could inhibit seizure-induced brain injury by targeting CCL2.

Signal Exchange through Extracellular Vesicles in Neuromuscular Junction Establishment and Maintenance: From Physiology to Pathology

Neuromuscular junction (NMJ) formation involves morphological changes both in motor terminals and muscle membrane. The molecular mechanisms leading to NMJ formation and maintenance have not yet been fully elucidated. During the last decade, it has become clear that virtually all cells release different types of extracellular vesicles (EVs), which can be taken up by nearby or distant cells modulating their activity. Initially, EVs were associated to a mechanism involved in the elimination of unwanted material; subsequent evidence demonstrated that exosomes, and more in general EVs, play a key role in intercellular communication by transferring proteins, lipids, DNA and RNA to target cells. Recently, EVs have emerged as potent carriers for Wnt, bone morphogenetic protein, miRNA secretion and extracellular traveling. Convincing evidence demonstrates that presynaptic terminals release exosomes that are taken up by muscle cells, and these exosomes can modulate synaptic plasticity in the recipient muscle cell in vivo. Furthermore, recent data highlighted that EVs could also be a potential cause of neurodegenerative disorders. Indeed, mutant SOD1, TDP-43 and FUS/TLS can be secreted by neural cells packaged into EVs and enter in neighboring neural cells, contributing to the onset and severity of the disease.

Mir-17∼92 Confers Motor Neuron Subtype Differential Resistance to ALS-Associated Degeneration

Progressive degeneration of motor neurons (MNs) is the hallmark of amyotrophic lateral sclerosis (ALS). Limb-innervating lateral motor column MNs (LMC-MNs) seem to be particularly vulnerable and are among the first MNs affected in ALS. Here, we report association of this differential susceptibility with reduced expression of the mir-17∼92 cluster in LMC-MNs prior to disease onset. Reduced mir-17∼92 is accompanied by elevated nuclear PTEN in spinal MNs of presymptomatic SOD1^G93A mice. Selective dysregulation of the mir-17∼92/nuclear PTEN axis in degenerating SOD1^G93A LMC-MNs was confirmed in a double-transgenic embryonic stem cell system and recapitulated in human SOD1^+/L144F-induced pluripotent stem cell (iPSC)-derived MNs. We further show that overexpression of mir-17∼92 significantly rescues human SOD1^+/L144F MNs, and intrathecal delivery of adeno-associated virus (AAV)9-mir-17∼92 improves motor deficits and survival in SOD1^G93A mice. Thus, mir-17∼92 may have value as a prognostic marker of MN degeneration and is a candidate therapeutic target in SOD1-linked ALS. VIDEO ABSTRACT.

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.

Dysregulation of MicroRNAs and Target Genes Networks in Peripheral Blood of Patients With Sporadic Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease. While genetics and other factors contribute to ALS pathogenesis, critical knowledge is still missing and validated biomarkers for monitoring the disease activity have not yet been identified. To address those aspects we carried out this study with the primary aim of identifying possible miRNAs/mRNAs dysregulation associated with the sporadic form of the disease (sALS). Additionally, we explored miRNAs as modulating factors of the observed clinical features. Study included 56 sALS and 20 healthy controls (HCs). We analyzed the peripheral blood samples of sALS patients and HCs with a high-throughput next-generation sequencing followed by an integrated bioinformatics/biostatistics analysis. Results showed that 38 miRNAs (let-7a-5p, let-7d-5p, let-7f-5p, let-7g-5p, let-7i-5p, miR-103a-3p, miR-106b-3p, miR-128-3p, miR-130a-3p, miR-130b-3p, miR-144-5p, miR-148a-3p, miR-148b-3p, miR-15a-5p, miR-15b-5p, miR-151a-5p, miR-151b, miR-16-5p, miR-182-5p, miR-183-5p, miR-186-5p, miR-22-3p, miR-221-3p, miR-223-3p, miR-23a-3p, miR-26a-5p, miR-26b-5p, miR-27b-3p, miR-28-3p, miR-30b-5p, miR-30c-5p, miR-342-3p, miR-425-5p, miR-451a, miR-532-5p, miR-550a-3p, miR-584-5p, miR-93-5p) were significantly downregulated in sALS. We also found that different miRNAs profiles characterized the bulbar/spinal onset and the progression rate. This observation supports the hypothesis that miRNAs may impact the phenotypic expression of the disease. Genes known to be associated with ALS (e.g., PARK7, C9orf72, ALS2, MATR3, SPG11, ATXN2) were confirmed to be dysregulated in our study. We also identified other potential candidate genes like LGALS3 (implicated in neuroinflammation) and PRKCD (activated in mitochondrial-induced apoptosis). Some of the downregulated genes are involved in molecular bindings to ions (i.e., metals, zinc, magnesium) and in ions-related functions. The genes that we found upregulated were involved in the immune response, oxidation-reduction, and apoptosis. These findings may have important implication for the monitoring, e.g., of sALS progression and therefore represent a significant advance in the elucidation of the disease's underlying molecular mechanisms. The extensive multidisciplinary approach we applied in this study was critically important for its success, especially in complex disorders such as sALS, wherein access to genetic background is a major limitation.

Differential Expression of Several miRNAs and the Host Genes AATK and DNM2 in Leukocytes of Sporadic ALS Patients

Genetic studies have managed to explain many cases of familial amyotrophic lateral sclerosis (ALS) through mutations in several genes. However, the cause of a majority of sporadic cases remains unknown. Recently, epigenetics, especially miRNA studies, show some promising aspects. We aimed to evaluate the differential expression of 10 miRNAs, including miR-9, miR-338, miR-638, miR-663a, miR-124a, miR-143, miR-451a, miR-132, miR-206, and let-7b, for which some connection to ALS was shown previously in ALS culture cells, animal models or patients, and in three miRNA host genes, including C1orf61 (miR-9), AATK (miR-338), and DNM2 (miR-638), in leukocyte samples of 84 patients with sporadic ALS. We observed significant aberrant dysregulation across our patient cohort for miR-124a, miR-206, miR-9, let-7b, and miR-638. Since we did not use neurological controls we cannot rule out that the revealed differences in expression of investigated miRNAs are specific for ALS. Nevertheless, the group of these five miRNAs is worth of additional research in leukocytes of larger cohorts from different populations in order to verify their potential association to ALS disease. We also detected a significant up-regulation of the AAKT gene and down-regulation of the DNM2 gene, and thus, for the first time, we connected these with sporadic ALS cases. These findings open up new research toward miRNAs as diagnostic biomarkers and epigenetic processes involved in ALS. The detected significant deregulation of AAKT and DNM2 in sporadic ALS also represents an interesting finding. The DNM2 gene was previously found to be mutated in Charcot-Marie-Tooth neuropathy-type CMT2M and centronuclear myopathy (CNM). In addition, as recent studies connected AATK and frontotemporal dementia (FTD) and DNM2 and hereditary spastic paraplegia (HSP), these two genes together with our results genetically connect, at least in part, five diseases, including FTD, HSP, Charcot-Marie-Tooth (type CMT2M), CNM, and ALS, thus opening future research toward a better understanding of the cell biology involved in these partly overlapping pathologies.

Amyotrophic lateral sclerosis as a protein level, non-genomic disease: Therapy with S2RM exosome released molecules

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease that leads to death. No effective treatments are currently available. Based on data from epidemiological, etiological, laboratory, and clinical studies, I offer a new way of thinking about ALS and its treatment. This paper describes a host of extrinsic factors, including the exposome, that disrupt the extracellular matrix and protein function such that a spreading, prion-like disease leads to neurodegeneration in the motor tracts. A treatment regimen is described using the stem cell released molecules from a number of types of adult stem cells to provide tissue dependent molecules that restore homeostasis, including proteostasis, in the ALS patient. Because stem cells themselves as a therapeutic are cumbersome and expensive, and when implanted in a host cause aging of the host tissue and often fail to engraft or remain viable, only the S2RM molecules are used. Rebuilding of the extracellular matrix and repair of the dysfunctional proteins in the ALS patient ensues.

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.

FUS Mutant Human Motoneurons Display Altered Transcriptome and microRNA Pathways with Implications for ALS Pathogenesis

The FUS gene has been linked to amyotrophic lateral sclerosis (ALS). FUS is a ubiquitous RNA-binding protein, and the mechanisms leading to selective motoneuron loss downstream of ALS-linked mutations are largely unknown. We report the transcriptome analysis of human purified motoneurons, obtained from FUS wild-type or mutant isogenic induced pluripotent stem cells (iPSCs). Gene ontology analysis of differentially expressed genes identified significant enrichment of pathways previously associated to sporadic ALS and other neurological diseases. Several microRNAs (miRNAs) were also deregulated in FUS mutant motoneurons, including miR-375, involved in motoneuron survival. We report that relevant targets of miR-375, including the neural RNA-binding protein ELAVL4 and apoptotic factors, are aberrantly increased in FUS mutant motoneurons. Characterization of transcriptome changes in the cell type primarily affected by the disease contributes to the definition of the pathogenic mechanisms of FUS-linked ALS.

Exosomes from NSC-34 Cells Transfected with hSOD1-G93A Are Enriched in miR-124 and Drive Alterations in Microglia Phenotype

Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset neurodegenerative disorder affecting motor neurons (MNs). Evidences indicate that ALS is a non-cell autonomous disease in which glial cells participate in both disease onset and progression. Exosomal transfer of mutant copper-zinc superoxide dismutase 1 (mSOD1) from cell-to-cell was suggested to contribute to disease dissemination. Data from our group and others showed that exosomes from activated cells contain inflammatory-related microRNAs (inflamma-miRNAs) that recapitulate the donor cell. While glia-derived exosomes and their effects in neurons have been addressed by several studies, only a few investigated the influence of motor neuron (MN)-derived exosomes in other cell function, the aim of the present study. We assessed a set of inflamma-miRs in NSC-34 MN-like cells transfected with mutant SOD1(G93A) and extended the study into their derived exosomes (mSOD1 exosomes). Then, the effects produced by mSOD1 exosomes in the activation and polarization of the recipient N9 microglial cells were investigated. Exosomes in coculture with N9 microglia and NSC-34 cells [either transfected with either wild-type (wt) human SOD1 or mutant SOD1(G93A)] showed to be transferred into N9 cells. Increased miR-124 expression was found in mSOD1 NSC-34 cells and in their derived exosomes. Incubation of mSOD1 exosomes with N9 cells determined a sustained 50% reduction in the cell phagocytic ability. It also caused a persistent NF-kB activation and an acute generation of NO, MMP-2, and MMP-9 activation, as well as upregulation of IL-1β, TNF-α, MHC-II, and iNOS gene expression, suggestive of induced M1 polarization. Marked elevation of IL-10, Arginase 1, TREM2, RAGE, and TLR4 mRNA levels, together with increased miR-124, miR-146a, and miR-155, at 24 h incubation, suggest the switch to mixed M1 and M2 subpopulations in the exosome-treated N9 microglial cells. Exosomes from mSOD1 NSC-34 MNs also enhanced the number of senescent-like positive N9 cells. Data suggest that miR-124 is translocated from the mSOD1 MNs to exosomes, which determine early and late phenotypic alterations in the recipient N9-microglial cells. In conclusion, modulation of the inflammatory-associated miR-124, in mSOD1 NSC-34 MNs, with potential benefits in the cargo of their exosomes may reveal a promising therapeutic strategy in halting microglia activation and associated effects in MN degeneration.

MicroRNA Metabolism and Dysregulation in Amyotrophic Lateral Sclerosis

MicroRNAs (miRNAs) are a subset of endogenous, small, non-coding RNA molecules involved in the post-transcriptional regulation of eukaryotic gene expression. Dysregulation in miRNA-related pathways in the central nervous system (CNS) is associated with severe neuronal injury and cell death, which can lead to the development of neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS). ALS is a fatal adult onset disease characterized by the selective loss of upper and lower motor neurons. While the pathogenesis of ALS is still largely unknown, familial ALS forms linked to TAR DNA-binding protein 43 (TDP-43) and fused in sarcoma (FUS) gene mutations, as well as sporadic forms, display changes in several steps of RNA metabolism, including miRNA processing. Here, we review the current knowledge about miRNA metabolism and biological functions and their crucial role in ALS pathogenesis with an in-depth analysis on different pathways. A more precise understanding of miRNA involvement in ALS could be useful not only to elucidate their role in the disease etiopathogenesis but also to investigate their potential as disease biomarkers and novel therapeutic targets.

ALS Along the Axons - Expression of Coding and Noncoding RNA Differs in Axons of ALS models

Amyotrophic lateral sclerosis (ALS) is a multifactorial lethal motor neuron disease with no known treatment. Although the basic mechanism of its degenerative pathogenesis remains poorly understood, a subcellular spatial alteration in RNA metabolism is thought to play a key role. The nature of these RNAs remains elusive, and a comprehensive characterization of the axonal RNAs involved in maintaining neuronal health has yet to be described. Here, using cultured spinal cord (SC) neurons grown using a compartmented platform followed by next-generation sequencing (NGS) technology, we find that RNA expression differs between the somatic and axonal compartments of the neuron, for both mRNA and microRNA (miRNA). Further, the introduction of SOD1^G93A and TDP43^A315T, established ALS-related mutations, changed the subcellular expression and localization of RNAs within the neurons, showing a spatial specificity to either the soma or the axon. Altogether, we provide here the first combined inclusive profile of mRNA and miRNA expression in two ALS models at the subcellular level. These data provide an important resource for studies on the roles of local protein synthesis and axon degeneration in ALS and can serve as a possible target pool for ALS treatment.

Unraveling gene expression profiles in peripheral motor nerve from amyotrophic lateral sclerosis patients: insights into pathogenesis

The aim of the present study is to investigate the molecular pathways underlying amyotrophic lateral sclerosis (ALS) pathogenesis within the peripheral nervous system. We analyzed gene expression changes in human motor nerve diagnostic biopsies obtained from eight ALS patients and seven patients affected by motor neuropathy as controls. An integrated transcriptomics and system biology approach was employed. We identified alterations in the expression of 815 genes, with 529 up-regulated and 286 down-regulated in ALS patients. Up-regulated genes clustered around biological process involving RNA processing and protein metabolisms. We observed a significant enrichment of up-regulated small nucleolar RNA transcripts (p = 2.68*10-11) and genes related to endoplasmic reticulum unfolded protein response and chaperone activity. We found a significant down-regulation in ALS of genes related to the glutamate metabolism. Interestingly, a network analysis highlighted HDAC2, belonging to the histone deacetylase family, as the most interacting node. While so far gene expression studies in human ALS have been performed in postmortem tissues, here specimens were obtained from biopsy at an early phase of the disease, making these results new in the field of ALS research and therefore appealing for gene discovery studies.

Bladder overactivity involves overexpression of MicroRNA 132 and nerve growth factor

AIM

Here, we assessed the expression of non-protein coding microRNAs (miRs), nerve growth factor and inflammatory molecules in the rat model of acetic acid induced bladder overactivity.

MAIN METHODS

Under isoflurane anesthesia, adult female Sprague-Dawley rats were instilled for 30min with either saline or NGF antisense oligonucleotide complexed with liposomes. 24h later, treated rats were exposed to either intravesical infusion of saline or saline containing 0.25% acetic acid at the rate of 0.04mL/min for 2h under urethane anesthesia (1g/kg; s.c). After CMG, bladder was harvested to study expression of NGF, cytokines and 8 specific miRNAs involved in bladder dysfunctions. The role of miR-132 in bladder overactivity was independently assessed through bladder wall transfection of plasmid encoding miR-132.

KEY FINDINGS

NGF overexpression in bladder overactivity was associated with ~2-fold upregulation and downregulation of miR-132 and miR-221, respectively. Pretreatment with NGF antisense restored the expression of miR-221 and miR-132 to control levels and also reduced the expression of NGF and cytokines (MCP-1 and sICAM-1). There was insignificant alteration in the expression of miR-199a-5p, and expression of, miR-210, miR-212, miR-155, miR-134 and miR-206 remained similar across the experimental groups. Bladder wall transfection of miR-132 plasmid in absence of acetic acid exposure was able to independently induce bladder overactivity, bladder hypertrophy and upregulate the expression of NGF and other cytokines.

SIGNIFICANCE

Overall, our work sheds light on the role of miR-132 in bladder overactivity, bladder hypertrophy, NGF signaling and expression of inflammatory mediators. Findings demonstrate that aberrant expression of NGF and miR-132 is involved in voiding dysfunctions.

Cell-type-specific miR-431 dysregulation in a motor neuron model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal-recessive pediatric neurodegenerative disease characterized by selective loss of spinal motor neurons. It is caused by mutation in the survival of motor neuron 1, SMN1, gene and leads to loss of function of the full-length SMN protein. microRNAs (miRNAs) are small RNAs that are involved in post-transcriptional regulation of gene expression. Prior studies have implicated miRNAs in the pathogenesis of motor neuron disease. We hypothesized that motor neuron-specific miRNA expression changes are involved in their selective vulnerability in SMA. Therefore, we sought to determine the effect of SMN loss on miRNAs and their target mRNAs in spinal motor neurons. We used microarray and RNAseq to profile both miRNA and mRNA expression in primary spinal motor neuron cultures after acute SMN knockdown. By integrating the miRNA:mRNA profiles, a number of dysregulated miRNAs were identified with enrichment in differentially expressed putative mRNA targets. miR-431 expression was highly increased, and a number of its putative mRNA targets were significantly downregulated in motor neurons after SMN loss. Further, we found that miR-431 regulates motor neuron neurite length by targeting several molecules previously identified to play a role in motor neuron axon outgrowth, including chondrolectin. Together, our findings indicate that cell-type-specific dysregulation of miR-431 plays a role in the SMA motor neuron phenotype.

Neuromuscular Junctions as Key Contributors and Therapeutic Targets in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a recessive autosomal neuromuscular disease, representing the most common fatal pediatric pathology. Even though, classically and in a simplistic way, it is categorized as a motor neuron (MN) disease, there is an increasing general consensus that its pathogenesis is more complex than expected. In particular, neuromuscular junctions (NMJs) are affected by dramatic alterations, including immaturity, denervation and neurofilament accumulation, associated to impaired synaptic functions: these abnormalities may in turn have a detrimental effect on MN survival. Here, we provide a description of NMJ development/maintenance/maturation in physiological conditions and in SMA, focusing on pivotal molecules and on the time-course of pathological events. Moreover, since NMJs could represent an important target to be exploited for counteracting the pathology progression, we also describe several therapeutic strategies that, directly or indirectly, aim at NMJs.

Expression of microRNAs in human post-mortem amyotrophic lateral sclerosis spinal cords provides insight into disease mechanisms

Amyotrophic lateral sclerosis is a late-onset and terminal neurodegenerative disease. The majority of cases are sporadic with unknown causes and only a small number of cases are genetically linked. Recent evidence suggests that post-transcriptional regulation and epigenetic mechanisms, such as microRNAs, underlie the onset and progression of neurodegenerative disorders; therefore, altered microRNA expression may result in the dysregulation of key genes and biological pathways that contribute to the development of sporadic amyotrophic lateral sclerosis. Using systems biology analyses on postmortem human spinal cord tissue, we identified dysregulated mature microRNAs and their potential targets previously implicated in functional process and pathways associated with the pathogenesis of ALS. Furthermore, we report a global reduction of mature microRNAs, alterations in microRNA processing, and support for a role of the nucleotide binding protein, TAR DNA binding protein 43, in regulating sporadic amyotrophic lateral sclerosis-associated microRNAs, thereby offering a potential underlying mechanism for sporadic amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis: mechanisms and therapeutics in the epigenomic era

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of the motor neurons, which results in weakness and atrophy of voluntary skeletal muscles. Treatments do not modify the disease trajectory effectively, and only modestly improve survival. A complex interaction between genes, environmental exposure and impaired molecular pathways contributes to pathology in patients with ALS. Epigenetic mechanisms control the hereditary and reversible regulation of gene expression without altering the basic genetic code. Aberrant epigenetic patterns-including abnormal microRNA (miRNA) biogenesis and function, DNA modifications, histone remodeling, and RNA editing-are acquired throughout life and are influenced by environmental factors. Thus, understanding the molecular processes that lead to epigenetic dysregulation in patients with ALS might facilitate the discovery of novel therapeutic targets and biomarkers that could reduce diagnostic delay. These achievements could prove crucial for successful disease modification in patients with ALS. We review the latest findings regarding the role of miRNA modifications and other epigenetic mechanisms in ALS, and discuss their potential as therapeutic targets.

MicroRNAs of two medically important mosquito species: Aedes aegypti and Anopheles stephensi

MicroRNAs (miRNAs) are endogenous, single-stranded small RNAs that have important regulatory functions at the post-transcriptional level. In the present study, we characterize miRNAs in two divergent mosquito species, Aedes aegypti and Anopheles stephensi, through deep sequencing of small RNAs spanning all developmental stages. We discovered eight novel miRNAs in Ae. aegypti and 20 novel miRNAs in An. stephensi, which enabled the first systematic analysis of miRNA evolution in mosquitos. We traced the phylogenetic history of all miRNAs in both species and report a rate of 0.055-0.13 miRNA net gain per million years. Most novel miRNAs originate de novo. Duplications that produced miRNA clusters and families are more common in Ae. aegypti than in An. stephensi. We also identified arm-switch as a source of new miRNAs. Expression profile analysis identified mosquito-specific miRNAs that showed strong stage-specific expression in one or both lineages. For example, the aae-miR-2941/2946 family represents the most abundant maternally deposited and zygotically transcribed miRNAs in Ae. aegypti. miR-2943 is a highly expressed zygotic miRNA in both Ae. aegypti and An. stephensi. Such information provides the basis from which to study the function of these miRNAs in biology common to all mosquitos or unique to one particular lineage.

Up-regulation of neural and cell cycle-related microRNAs in brain of amyotrophic lateral sclerosis mice at late disease stage

Background

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective motor neuron degeneration in motor cortex, brainstem and spinal cord. microRNAs (miRNAs) are small non-coding RNAs that bind complementary target sequences and modulate gene expression; they are key molecules for establishing a neuronal phenotype, and in neurodegeneration. Here we investigated neural miR-9, miR-124a, miR-125b, miR-219, miR-134, and cell cycle-related miR-19a and -19b, in G93A-SOD1 mouse brain in pre-symptomatic and late stage disease.

Results

Expression of miR-9, miR-124a, miR-19a and -19b was significantly increased in G93A-SOD1 whole brain at late stage disease compared to B6.SJL and Wt-SOD1 control brains. These miRNAs were then analyzed in manually dissected SVZ, hippocampus, primary motor cortex and brainstem motor nuclei in 18-week-old ALS mice compared to same age controls. In SVZ and hippocampus miR-124a was up-regulated, miR-219 was down-regulated, and numbers of neural stem progenitor cells (NSPCs) were significantly increased. In G93A-SOD1 brainstem motor nuclei and primary motor cortex, miR-9 and miR-124a were significantly up-regulated, miR-125b expression was also increased. miR-19a and -19b were up-regulated in primary motor cortex and hippocampus, respectively. Expression analysis of predicted miRNA targets identified miRNA/target gene pairs differentially expressed in G93A-SOD1 brain regions compared to controls.

Conclusions

Hierarchical clustering analysis, identifying two clusters of miRNA/target genes, one characterizing brainstem motor nuclei and primary motor cortex, the other hippocampus and SVZ, suggests that altered expression of neural and cell cycle-related miRNAs in these brain regions might contribute to ALS pathogenesis in G93A-SOD1 mice. Re-establishing their expression to normal levels could be a new therapeutic approach to ALS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-015-0095-0) contains supplementary material, which is available to authorized users.

ALS as a distal axonopathy: molecular mechanisms affecting neuromuscular junction stability in the presymptomatic stages of the disease

Amyotrophic Lateral Sclerosis (ALS) is being redefined as a distal axonopathy, in that many molecular changes influencing motor neuron degeneration occur at the neuromuscular junction (NMJ) at very early stages of the disease prior to symptom onset. A huge variety of genetic and environmental causes have been associated with ALS, and interestingly, although the cause of the disease can differ, both sporadic and familial forms of ALS show a remarkable similarity in terms of disease progression and clinical manifestation. The NMJ is a highly specialized synapse, allowing for controlled signaling between muscle and nerve necessary for skeletal muscle function. In this review we will evaluate the clinical, animal experimental and cellular/molecular evidence that supports the idea of ALS as a distal axonopathy. We will discuss the early molecular mechanisms that occur at the NMJ, which alter the functional abilities of the NMJ. Specifically, we focus on the role of axon guidance molecules on the stability of the cytoskeleton and how these molecules may directly influence the cells of the NMJ in a way that may initiate or facilitate the dismantling of the neuromuscular synapse in the presymptomatic stages of ALS.