Potential of activated microglia as a source of dysregulated extracellular microRNAs contributing to neurodegeneration in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron degeneration in adults, and several mechanisms underlying the disease pathology have been proposed. It has been shown that glia communicate with other cells by releasing extracellular vesicles containing proteins and nucleic acids, including microRNAs (miRNAs), which play a role in the post-transcriptional regulation of gene expression. Dysregulation of miRNAs is commonly observed in ALS patients, together with inflammation and an altered microglial phenotype. However, the role of miRNA-containing vesicles in microglia-to-neuron communication in the context of ALS has not been explored in depth. This review summarises the evidence for the presence of inflammation, pro-inflammatory microglia and dysregulated miRNAs in ALS, then explores how microglia may potentially be responsible for this miRNA dysregulation. The possibility of pro-inflammatory ALS microglia releasing miRNAs which may then enter neuronal cells to contribute to degeneration is also explored. Based on the literature reviewed here, microglia are a likely source of dysregulated miRNAs and potential mediators of neurodegenerative processes. Therefore, dysregulated miRNAs may be promising candidates for the development of therapeutic strategies

Corrigendum: an overview of MicroRNAs as biomarkers of ALS

A Corrigendum on An Overview of MicroRNAs as Biomarkers of ALS by Joilin, G., Leigh, P. N., Newbury, S. F., and Hafezparast, M. (2019). Front. Neurol. 10:186. doi: 10.3389/fneur.2019.00186 In the original article, there was a mistake in Table 1 as published. Some of the miRNAs listed in the table were incorrectly placed in the wrong column and/or row. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated

An ALS-associated mutation dysregulates microglia-derived extracellular microRNAs in a sex-specific manner

Evidence suggests the presence of microglial activation and microRNA (miRNA) dysregulation in amyotrophic lateral sclerosis (ALS), the most common form of adult motor neuron disease. However, few studies have investigated whether the miRNA dysregulation originates from microglia. Furthermore, TDP-43 (encoded by TARDBP), involved in miRNA biogenesis, aggregates in tissues of ∼98% of ALS cases. Thus, this study aimed to determine whether expression of the ALS-linked TDP-43M337V mutation in a transgenic mouse model dysregulates microglia-derived miRNAs. RNA sequencing identified several dysregulated miRNAs released by transgenic microglia and a differential miRNA release by lipopolysaccharide-stimulated microglia, which was more pronounced in cells from female mice. We validated the downregulation of three candidate miRNAs, namely, miR-16-5p, miR-99a-5p and miR-191-5p, by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and identified their predicted targets, which primarily include genes involved in neuronal development and function. These results suggest that altered TDP-43 function leads to changes in the miRNA population released by microglia, which may in turn be a source of the miRNA dysregulation observed in the disease. This has important implications for the role of neuroinflammation in ALS pathology and could provide potential therapeutic targets

Identification of a potential non-coding RNA biomarker signature for amyotrophic lateral sclerosis

Objective biomarkers for the clinically heterogeneous adult-onset neurodegenerative disorder amyotrophic lateral sclerosis are crucial to facilitate assessing emerging therapeutics, and improve the diagnostic pathway in what is a clinically heterogeneous syndrome. With non-coding RNA transcripts including microRNA, piwi-RNA, and transfer RNA present in human biofluids, we sought to identify whether non-coding RNA in serum could be biomarkers for amyotrophic lateral sclerosis. Serum samples from our Oxford Study for Biomarkers in MND/ALS discovery cohort of amyotrophic lateral sclerosis patients (n=48), disease mimics (n=16), and age- and sex-matched healthy controls (n=24) were profiled for non-coding RNA expression using RNA-sequencing, which showed a wide range of non-coding RNA to be dysregulated. We confirmed significant alterations with reverse transcription-quantitative PCR in the expression of hsa-miR-16-5p, hsa-miR-21-5p, hsa-miR-92a-3p, hsa-piR-33151, TRV-AAC4-1.1, and TRA-AGC6-1.1. Furthermore, hsa-miR-206, a previously identified amyotrophic lateral sclerosis biomarker, showed a binary-like pattern of expression in our samples. Using the expression of these non-coding RNA, we were able to discriminate amyotrophic lateral sclerosis samples from healthy controls in our discovery cohort using a random forest analysis with 93.7% accuracy with promise in predicting progression rate of patients. Importantly, cross-validation of this novel signature using a new geographically distinct cohort of samples from the United Kingdom and Germany with both amyotrophic lateral sclerosis and control samples (n=156) yielded an accuracy of 73.9%. The high prediction accuracy of this non-coding RNA-based biomarker signature, even across heterogeneous cohorts, demonstrates the strength of our approach as a novel platform to identify and stratify amyotrophic lateral sclerosis patients

Profiling non-coding RNA expression in cerebrospinal fluid of amyotrophic lateral sclerosis patients

Introduction Objective biomarkers for the fatal neurodegenerative disease amyotrophic lateral sclerosis or motor neuron disease (ALS/MND) are critical for diagnosis, drug development, clinical trials, and insight into disease pathology. Key candidates for biomarkers present in biofluids include non-coding RNA (ncRNA) transcripts including microRNA, piwi-interacting RNA and transfer RNA. To determine if the central nervous system was the source of the dysregulated ncRNA biomarkers we previously observed in serum, we sought to identify dysregulated ncRNA candidates in cerebrospinal fluid (CSF) which may provide new insight into the disease pathology. Methods and materials Small RNA sequencing (RNA-seq) was undertaken on CSF samples from healthy controls (n = 18), disease mimics (n = 8), and ALS patients (n = 40) in our Oxford Study for Biomarkers of ALS cohort, with RT-qPCR used to confirm their dysregulation. Results We found a range of ncRNA that were dysregulated in the RNA-seq screen, but these failed to be validated or detected in some cases using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Additionally, our previously identified serum ncRNA biomarker showed no change in CSF or correlation to serum. Conclusions This study suggests the CSF may not be the source of dysregulated ncRNA in the serum and highlights the difficulty in identifying ncRNA in CSF as biomarkers for ALS

Boletín Oficial de la Provincia de Oviedo: Número 235 - 1942 octubre 24

The genome of humans and other eukaryotes contain multiple non-coding elements including microRNA, which are now recognised as important negative regulators of gene expression. Indeed, microRNA are likely to be critical regulators of the biological processes underlying memory and its dysfunction in Alzheimer’s disease. Long-term potentiation (LTP) is the preeminent model of memory widely used to understand its underlying molecular and cellular processes. LTP induced at hippocampal perforant path synapses of awake freely moving animals shows remarkable persistence, which is underpinned by dynamic regulation of gene networks. Our recent bioinformatic analysis predicted microRNA to be important contributors in regulating LTP-related gene expression. Further, our microarray analysis demonstrated concurrent with rapid up-regulation of mRNA expression post-LTP induction was rapid down-regulation of microRNA expression. Therefore, it was hypothesised that a release of microRNA-mediated inhibition on gene expression may contribute to LTP persistence. To explore the significance of microRNA regulation following LTP, the expression of two mature microRNA (miR-34a-5p and miR-132-3p), down-regulated in the microarray analysis, were assessed with RT-qPCR in our in vivo LTP model in awake male Sprague-Dawley rats. These microRNA, previously linked to multiple LTP-related processes, including neurotransmission, transcription, and dendritic spine morphology, were confirmed to be down-regulated 20 min post-LTP induction in a N-methyl-D-aspartic acid receptor-dependent manner. While levels of both microRNA returned to baseline by 24 h, miR-34a-5p remained down-regulation at 5 h. Further, no temporal regulation of pri-miR-34a was found, while pri-miR-132/212 showed a dramatic up-regulation at 20 min, attenuated by 5 h, and down-regulated at 24 h. Therefore, multiple regulatory mechanisms appear to underlie the expression of these microRNA following LTP induction. To fully understand the potential contribution of miR-34a-5p and miR-132-3p to the persistence of LTP, a number of bioinformatic tools were utilised to identify novel targets of these microRNA. A Weighted Gene Co-Expression Network Analysis demonstrated these microRNA did not target clusters of genes temporally co-expressed post-LTP. Next, evaluation of nine microRNA targeting algorithms showed no one algorithm, or their intersection, predicted sufficiently previously validated targets. Their union, however, covered the majority of this microRNA-target interactome, and was filtered for genes annotated as involved in LTP-related processes. This identified several novel targets of miR-34a-5p and miR-132-3p. Of interest were predicted interactions between miR-132-3p and the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor subunit gene Gria2, and the important signalling molecule gene Mapk1. Luciferase assays demonstrated miR-132-3p does interact with Mapk1, but not Gria2. Further investigation of Mapk1 using RT-qPCR and Western blots found that the mRNA and associated p42-MAPK protein were up-regulated 5 and 24 h following LTP induction. These results support the hypothesis that miR-132-3p is involved in regulating Mapk1 post-LTP induction. In summary, this work demonstrated that microRNA are dynamically regulated following LTP induction and that they can target genes involved in the processes underlying its persistence. Further, with careful consideration, microRNA targeting algorithms have the potential to identify microRNA targets for further investigation. Thus, microRNA are likely to play an important role in regulating gene expression underlying LTP persistence and memory

A case for non-coding RNA as a suitable biomarker of amyotrophic lateral sclerosis

No description supplied</p

The ALS-associated TDP-43M337V mutation dysregulates microglia-derived extracellular microRNAs in a sex-specific manner.

Evidence suggests the presence of microglial activation and microRNA (miRNA) dysregulation in amyotrophic lateral sclerosis (ALS), the most common form of adult motor neuron disease. However, few studies have investigated whether the miRNA dysregulation may originate from microglia. Furthermore, TDP-43, involved in miRNA biogenesis, aggregates in tissues of ∼98% of ALS cases. Thus, this study aimed to determine whether expression of the ALS-linked TDP-43M337V mutation in a transgenic mouse model dysregulates microglia-derived miRNAs. RNA sequencing identified several dysregulated miRNAs released by transgenic microglia, and a differential miRNA release by lipopolysaccharide-stimulated microglia, which was more pronounced in cells from female mice. We validated the downregulation of three candidate miRNAs, miR-16-5p, miR-99a-5p, and miR-191-5p by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), and identified their predicted targets, which include primarily genes involved in neuronal development and function. These results suggest that altered TDP-43 function leads to changes in the miRNA population released by microglia, which may in turn be a source of the miRNA dysregulation observed in the disease. This has important implications for the role of neuroinflammation in ALS pathology and could provide potential therapeutic targets.</p

Potential of Non-Coding RNA as Biomarkers for Progressive Supranuclear Palsy.

Objective markers for the neurodegenerative disorder progressive supranuclear palsy (PSP) are needed to provide a timely diagnosis with greater certainty. Non-coding RNA (ncRNA), including microRNA, piwi-interacting RNA, and transfer RNA, are good candidate markers in other neurodegenerative diseases, but have not been investigated in PSP. Therefore, as proof of principle, we sought to identify whether they were dysregulated in matched serum and cerebrospinal fluid (CSF) samples of patients with PSP. Small RNA-seq was undertaken on serum and CSF samples from healthy controls (n = 20) and patients with PSP (n = 31) in two cohorts, with reverse transcription-quantitative PCR (RT-qPCR) to confirm their dysregulation. Using RT-qPCR, we found in serum significant down-regulation in hsa-miR-92a-3p, hsa-miR-626, hsa-piR-31068, and tRNA-ValCAC. In CSF, both hsa-let-7a-5p and hsa-piR-31068 showed significant up-regulation, consistent with their changes observed in the RNA-seq results. Interestingly, we saw no correlation in the expression of hsa-piR-31068 within our matched serum and CSF samples, suggesting there is no common dysregulatory mechanism between the two biofluids. While these changes were in a small cohort of samples, we have provided novel evidence that ncRNA in biofluids could be possible diagnostic biomarkers for PSP and further work will help to expand this potential