The microRNA miR-34 modulates ageing and neurodegeneration in Drosophila

Maintenance of age in human neurons generated by microRNA-based neuronal conversion of fibroblasts

Aging is a major risk factor in many forms of late-onset neurodegenerative disorders. The ability to recapitulate age-related characteristics of human neurons in culture will offer unprecedented opportunities to study the biological processes underlying neuronal aging. Here, we show that using a recently demonstrated microRNA-based cellular reprogramming approach, human fibroblasts from postnatal to near centenarian donors can be efficiently converted into neurons that maintain multiple age-associated signatures. Application of an epigenetic biomarker of aging (referred to as epigenetic clock) to DNA methylation data revealed that the epigenetic ages of fibroblasts were highly correlated with corresponding age estimates of reprogrammed neurons. Transcriptome and microRNA profiles reveal genes differentially expressed between young and old neurons. Further analyses of oxidative stress, DNA damage and telomere length exhibit the retention of age-associated cellular properties in converted neurons from corresponding fibroblasts. Our results collectively demonstrate the maintenance of age after neuronal conversion.

Extracellular RNA in aging

Since the discovery of extracellular RNA (exRNA) in circulation and other bodily fluids, there has been considerable effort to catalog and assess whether exRNAs can be used as markers for health and disease. A variety of exRNA species have been identified including messenger RNA and noncoding RNA such as microRNA (miRNA), small nucleolar RNA, transfer RNA, and long noncoding RNA. Age-related changes in exRNA abundance have been observed, and it is likely that some of these transcripts play a role in aging. In this review, we summarize the current state of exRNA profiling in various body fluids and discuss age-related changes in exRNA abundance that have been identified in humans and other model organisms. miRNAs, in particular, are a major focus of current research and we will highlight and discuss the potential role that specific miRNAs might play in age-related phenotypes and disease. We will also review challenges facing this emerging field and various strategies that can be used for the validation and future use of exRNAs as markers of aging and age-related disease. WIREs RNA 2017, 8:e1385. doi: 10.1002/wrna.1385 For further resources related to this article, please visit the WIREs website.

A let-7-to-miR-125 MicroRNA Switch Regulates Neuronal Integrity and Lifespan in Drosophila

Messenger RNAs (mRNAs) often contain binding sites for multiple, different microRNAs (miRNAs). However, the biological significance of this feature is unclear, since such co-targeting miRNAs could function coordinately, independently, or redundantly with one another. Here, we show that two co-transcribed Drosophila miRNAs, let-7 and miR-125, non-redundantly regulate a common target, the transcription factor Chronologically Inappropriate Morphogenesis (Chinmo). We first characterize novel adult phenotypes associated with loss of both let-7 and miR-125, which are derived from a common, polycistronic transcript that also encodes a third miRNA, miR-100. Consistent with the coordinate upregulation of all three miRNAs in aging flies, these phenotypes include brain degeneration and shortened lifespan. However, transgenic rescue analysis reveal separable roles for these miRNAs: adult miR-125 but not let-7 mutant phenotypes are associated with ectopic Chinmo expression in adult brains and are suppressed by chinmo reduction. In contrast, let-7 is predominantly responsible for regulating chinmo during nervous system formation. These results indicate that let-7 and miR-125 function during two distinct stages, development and adulthood, rather than acting at the same time. These different activities are facilitated by an increased rate of processing of let-7 during development and a lower rate of decay of the accumulated miR-125 in the adult nervous system. Thus, this work not only establishes a key role for the highly conserved miR-125 in aging. It also demonstrates that two co-transcribed miRNAs function independently during distinct stages to regulate a common target, raising the possibility that such biphasic control may be a general feature of clustered miRNAs.

Deregulation of mRNAs that are targeted by multiple miRNAs is a common feature of a number of diseased states including neurodegenerative disorders. The currently accepted model is that the combined action of all binding miRNAs ensures target repression. Here, we show that two co-expressed miRNAs exert distinct outcomes on a common target. While miR-125 extends lifespan by repressing its target, chinmo, in adult brains, let-7 downregulates Chinmo in developing animals. Our results indicate that differential processing and turnover rates of let-7 and miR-125 contribute to this switch in miRNA activity. This study has identified the physiological relevance of the targeting of a single mRNA by multiple miRNAs in a scenario where each miRNA exerts a distinct and non-overlapping outcome.

miR-29c contribute to glioma cells temozolomide sensitivity by targeting O6-methylguanine-DNA methyltransferases indirectely

Temozolomide (TMZ) is the most commonly used alkylating agent in glioma chemotherapy. However growing resistance to TMZ remains a major challenge to clinicians. The DNA repair protein O6-methylguanine-DNA methytransferase (MGMT) plays critical roles in TMZ resistance. Promoter methylation can inhibit MGMT expression and increase chemosensitivity. Here, we described a novel mechanism regulating MGMT expression. We showed that miR-29c suppressed MGMT expression indirectly via targeting specificity protein 1 (Sp1). MiR-29c overexpression increased TMZ efficacy in cultured glioma cells and in mouse xenograft models. The miR-29c levels were positively correlated with patient outcomes. Our data suggest miR-29c may be potential therapeutic targets for glioma treatment.

Noncoding Transcriptional Landscape in Human Aging

Aging is a universal phenomenon in metazoans, characterized by a general decline of the organism physiology associated with an increased risk of mortality and morbidity. Aging of an organism correlates with a decline in function of its cells, as shown for muscle, immune, and neuronal cells. As the DNA content of most cells within an organism remains largely identical throughout the life span, age-associated transcriptional changes must be achieved by epigenetic mechanisms. However, how aging may impact on the epigenetic state of cells is only beginning to be understood. In light of a growing number of studies demonstrating that noncoding RNAs can provide molecular signals that regulate expression of protein-coding genes and define epigenetic states of cells, we hypothesize that noncoding RNAs could play a direct role in inducing age-associated profiles of gene expression. In this context, the role of long noncoding RNAs (lncRNAs) as regulators of gene expression might be important for the overall transcriptional landscape observed in aged human cells. The possible functions of lncRNAs and other noncoding RNAs, and their roles in the regulation of aging-related cellular pathways will be analyzed.

An overview of circulating cell-free microRNAs as putative biomarkers in Alzheimer's and Parkinson's Diseases

Circulating cell-free microRNAs (miRNAs) are stable in many biological fluids and their expression profiles can suffer changes under different physiological and pathological conditions. In the last few years, miRNAs have been proposed as putative noninvasive biomarkers in diagnosis, prognosis and response to treatment for several diseases, including neurodegenerative disorders as Alzheimer's disease (AD) and Parkinson's disease (PD). Cognitive and/or motor impairments are usually considered for establishing clinical diagnosis, and at this stage, the majority of the neurons may already be lost making difficult attempts of novel therapies. In this review, we intend to survey the circulating cell-free miRNAs found as dysregulated in cerebrospinal fluid, serum and plasma samples in AD and PD patients, and show how those miRNAs can be useful for early and differential diagnosis. Beyond that, we highlighted the miRNAs that are possibly related to common molecular mechanisms in the neurodegeneration process, as well those miRNAs related to specific disease pathways.

Epigenetics and aging

Over the past decade, a growing number of studies have revealed that progressive changes to epigenetic information accompany aging in both dividing and nondividing cells. Functional studies in model organisms and humans indicate that epigenetic changes have a huge influence on the aging process. These epigenetic changes occur at various levels, including reduced bulk levels of the core histones, altered patterns of histone posttranslational modifications and DNA methylation, replacement of canonical histones with histone variants, and altered noncoding RNA expression, during both organismal aging and replicative senescence. The end result of epigenetic changes during aging is altered local accessibility to the genetic material, leading to aberrant gene expression, reactivation of transposable elements, and genomic instability. Strikingly, certain types of epigenetic information can function in a transgenerational manner to influence the life span of the offspring. Several important conclusions emerge from these studies: rather than being genetically predetermined, our life span is largely epigenetically determined; diet and other environmental influences can influence our life span by changing the epigenetic information; and inhibitors of epigenetic enzymes can influence life span of model organisms. These new findings provide better understanding of the mechanisms involved in aging. Given the reversible nature of epigenetic information, these studies highlight exciting avenues for therapeutic intervention in aging and age-associated diseases, including cancer.

miR-146a is upregulated during retinal pigment epithelium (RPE)/choroid aging in mice and represses IL-6 and VEGF-A expression in RPE cells

PURPOSE

MicroRNA-146a (miR-146a) has been proposed as a marker for age-associated inflammation, or "inflammaging", acting as a negative regulator of cellular senescence and pro-inflammatory signaling pathways. However, the regulation and function of miR-146 during ocular aging remains unclear. Here we propose that miR-146 is regulated during aging of the retina and choroid, and functions in retinal pigment epithelial (RPE) cells to regulate key genes involved in inflammation and angiogenesis.

METHODS

The expression of miR-146a and miR-146b was examined in the neuroretina and RPE/choroid in mice aged from 2 months to 24 months. Then, the effect of synthetic miR-146a mimetic on IL-6 and VEGF-A expression was analyzed in RPE cells treated with and without TNF-α.

RESULTS

miR-146a and miR-146b was upregulated during aging of RPE/choroid but not neuroretina, supporting tissue-specific regulation of aging-related miRNAs in retinal tissues. Overexpression of miR-146a by miRNA mimics inhibited VEGF-A and TNF-α-induced IL-6 expression.

CONCLUSIONS

Elevation of miR-146a and miR-146b in the aging RPE/choroid but not neuroretina suggests a role for miRNAs in inflammaging in the RPE/choroid. miR-146a overexpression inhibits the expression IL-6 and VEGF-A in the RPE cells, supporting a negative feedback regulation mechanism by which inflammatory pathways may be dysregulated in RPE during aging.

Metformin-mediated increase in DICER1 regulates microRNA expression and cellular senescence

Metformin, an oral hypoglycemic agent, has been used for decades to treat type 2 diabetes mellitus. Recent studies indicate that mice treated with metformin live longer and have fewer manifestations of age‐related chronic disease. However, the molecular mechanisms underlying this phenotype are unknown. Here, we show that metformin treatment increases the levels of the microRNA‐processing protein DICER1 in mice and in humans with diabetes mellitus. Our results indicate that metformin upregulates DICER1 through a post‐transcriptional mechanism involving the RNA‐binding protein AUF1. Treatment with metformin altered the subcellular localization of AUF1, disrupting its interaction with DICER1 mRNA and rendering DICER1 mRNA stable, allowing DICER1 to accumulate. Consistent with the role of DICER1 in the biogenesis of microRNAs, we found differential patterns of microRNA expression in mice treated with metformin or caloric restriction, two proven life‐extending interventions. Interestingly, several microRNAs previously associated with senescence and aging, including miR‐20a, miR‐34a, miR‐130a, miR‐106b, miR‐125, and let‐7c, were found elevated. In agreement with these findings, treatment with metformin decreased cellular senescence in several senescence models in a DICER1‐dependent manner. Metformin lowered p16 and p21 protein levels and the abundance of inflammatory cytokines and oncogenes that are hallmarks of the senescence‐associated secretory phenotype (SASP). These data lead us to hypothesize that changes in DICER1 levels may be important for organismal aging and to propose that interventions that upregulate DICER1 expression (e.g., metformin) may offer new pharmacotherapeutic approaches for age‐related disease.

ROS, Cell Senescence, and Novel Molecular Mechanisms in Aging and Age-Related Diseases

The aging process worsens the human body functions at multiple levels, thus causing its gradual decrease to resist stress, damage, and disease. Besides changes in gene expression and metabolic control, the aging rate has been associated with the production of high levels of Reactive Oxygen Species (ROS) and/or Reactive Nitrosative Species (RNS). Specific increases of ROS level have been demonstrated as potentially critical for induction and maintenance of cell senescence process. Causal connection between ROS, aging, age-related pathologies, and cell senescence is studied intensely. Senescent cells have been proposed as a target for interventions to delay the aging and its related diseases or to improve the diseases treatment. Therapeutic interventions towards senescent cells might allow restoring the health and curing the diseases that share basal processes, rather than curing each disease in separate and symptomatic way. Here, we review observations on ROS ability of inducing cell senescence through novel mechanisms that underpin aging processes. Particular emphasis is addressed to the novel mechanisms of ROS involvement in epigenetic regulation of cell senescence and aging, with the aim to individuate specific pathways, which might promote healthy lifespan and improve aging.

Tiny giants of gene regulation: experimental strategies for microRNA functional studies

The discovery over two decades ago of short regulatory microRNAs (miRNAs) has led to the inception of a vast biomedical research field dedicated to understanding these powerful orchestrators of gene expression. Here we aim to provide a comprehensive overview of the methods and techniques underpinning the experimental pipeline employed for exploratory miRNA studies in animals. Some of the greatest challenges in this field have been uncovering the identity of miRNA-target interactions and deciphering their significance with regard to particular physiological or pathological processes. These endeavors relied almost exclusively on the development of powerful research tools encompassing novel bioinformatics pipelines, high-throughput target identification platforms, and functional target validation methodologies. Thus, in an unparalleled manner, the biomedical technology revolution unceasingly enhanced and refined our ability to dissect miRNA regulatory networks and understand their roles in vivo in the context of cells and organisms. Recurring motifs of target recognition have led to the creation of a large number of multifactorial bioinformatics analysis platforms, which have proved instrumental in guiding experimental miRNA studies. Subsequently, the need for discovery of miRNA-target binding events in vivo drove the emergence of a slew of high-throughput multiplex strategies, which now provide a viable prospect for elucidating genome-wide miRNA-target binding maps in a variety of cell types and tissues. Finally, deciphering the functional relevance of miRNA post-transcriptional gene silencing under physiological conditions, prompted the evolution of a host of technologies enabling systemic manipulation of miRNA homeostasis as well as high-precision interference with their direct, endogenous targets. For further resources related to this article, please visit the WIREs website.

Transcriptional and epigenetic regulation of autophagy in aging

Macroautophagy is a major intracellular degradation process recognized as playing a central role in cell survival and longevity. This multistep process is extensively regulated at several levels, including post-translationally through the action of conserved longevity factors such as the nutrient sensor TOR. More recently, transcriptional regulation of autophagy genes has emerged as an important mechanism for ensuring the somatic maintenance and homeostasis necessary for a long life span. Autophagy is increased in many long-lived model organisms and contributes significantly to their longevity. In turn, conserved transcription factors, particularly the helix-loop-helix transcription factor TFEB and the forkhead transcription factor FOXO, control the expression of many autophagy-related genes and are important for life-span extension. In this review, we discuss recent progress in understanding the contribution of these transcription factors to macroautophagy regulation in the context of aging. We also review current research on epigenetic changes, such as histone modification by the deacetylase SIRT1, that influence autophagy-related gene expression and additionally affect aging. Understanding the molecular regulation of macroautophagy in relation to aging may offer new avenues for the treatment of age-related diseases.

A long non-coding RNA targets microRNA miR-34a to regulate colon cancer stem cell asymmetric division

The roles of long non-coding RNAs (lncRNAs) in regulating cancer and stem cells are being increasingly appreciated. Its diverse mechanisms provide the regulatory network with a bigger repertoire to increase complexity. Here we report a novel LncRNA, Lnc34a, that is enriched in colon cancer stem cells (CCSCs) and initiates asymmetric division by directly targeting the microRNA miR-34a to cause its spatial imbalance. Lnc34a recruits Dnmt3a via PHB2 and HDAC1 to methylate and deacetylate the miR-34a promoter simultaneously, hence epigenetically silencing miR-34a expression independent of its upstream regulator, p53. Lnc34a levels affect CCSC self-renewal and colorectal cancer (CRC) growth in xenograft models. Lnc34a is upregulated in late-stage CRCs, contributing to epigenetic miR-34a silencing and CRC proliferation. The fact that lncRNA targets microRNA highlights the regulatory complexity of non-coding RNAs (ncRNAs), which occupy the bulk of the genome.

DOI:http://dx.doi.org/10.7554/eLife.14620.001

Tumors are made of millions of cells that are not all the same. A type of cancer cell known as cancer stem cells (or CSCs for short) are often better at dividing to produce new cells and moving to new sites in the body than other types of cancer cell. Very small molecules called micro ribonucleic acids (or microRNAs for short) can influence how CSCs grow and divide by regulating the activity of specific genes. For example, a microRNA molecule called miR-34a suppresses the activity of several genes – which slows the growth of various tumors, including lung and bowel cancers. This miR-34a is often missing from some types of cells in advanced tumors.

Genes encode the instructions to produce RNAs, and Wang, Bu et al. wanted to find out what stops miR-34a being produced in certain bowel cancer cells. The experiments revealed a new, very long RNA molecule – named long non-coding RNA 34 (or Lnc34a) – that binds to the gene that encodes miR-34a. Lnc34a recruits proteins that modify the gene and switch off the production of miR-34a.

Furthermore, microscopy experiments revealed that when colon cancer cells divide, Lnc34a is distributed unevenly so that it blocks the production of miR-34a in one daughter cell but not the other. Lastly, Wang, Bu et al. confirmed that Lnc34a is found in higher levels in CSCs than in other cancer cells, which helps them to grow and divide more rapidly. Future experiments will try to find out what controls the production of Lnc34a and search for drugs that can block this process in cancer cells.

DOI:http://dx.doi.org/10.7554/eLife.14620.002

MicroRNAs Circulate in the Hemolymph of Drosophila and Accumulate Relative to Tissue microRNAs in an Age-Dependent Manner

In mammals, extracellular miRNAs circulate in biofluids as stable entities that are secreted by normal and diseased tissues, and can enter cells and regulate gene expression. Drosophila melanogaster is a proven system for the study of human diseases. They have an open circulatory system in which hemolymph (HL) circulates in direct contact with all internal organs, in a manner analogous to vertebrate blood plasma. Here, we show using deep sequencing that Drosophila HL contains RNase-resistant circulating miRNAs (HL-miRNAs). Limited subsets of body tissue miRNAs (BT-miRNAs) accumulated in HL, suggesting that they may be specifically released from cells or particularly stable in HL. Alternatively, they might arise from specific cells, such as hemocytes, that are in intimate contact with HL. Young and old flies accumulated unique populations of HL-miRNAs, suggesting that their accumulation is responsive to the physiological status of the fly. These HL-miRNAs in flies may function similar to the miRNAs circulating in mammalian biofluids. The discovery of these HL-miRNAs will provide a new venue for health and disease-related research in Drosophila.

The 3'-5' exoribonuclease Dis3 regulates the expression of specific microRNAs in Drosophila wing imaginal discs

Dis3 is a highly conserved exoribonuclease which degrades RNAs in the 3'-5' direction. Mutations in Dis3 are associated with a number of human cancers including multiple myeloma and acute myeloid leukemia. In this work, we have assessed the effect of a Dis3 knockdown on Drosophila imaginal disc development and on expression of mature microRNAs. We find that Dis3 knockdown severely disrupts the development of wing imaginal discs in that the flies have a “no wing” phenotype. Use of RNA-seq to quantify the effect of Dis3 knockdown on microRNA expression shows that Dis3 normally regulates a small subset of microRNAs, with only 11 (10.1%) increasing in level ≥2-fold and 6 (5.5%) decreasing in level ≥2-fold. Of these microRNAs, miR-252–5p is increased 2.1-fold in Dis3-depleted cells compared to controls while the level of the miR-252 precursor is unchanged, suggesting that Dis3 can act in the cytoplasm to specifically degrade this mature miRNA. Furthermore, our experiments suggest that Dis3 normally interacts with the exosomal subunit Rrp40 in the cytoplasm to target miR-252–5p for degradation during normal wing development. Another microRNA, miR-982–5p, is expressed at lower levels in Dis3 knockdown cells, while the miR-982 precursor remains unchanged, indicating that Dis3 is involved in its processing. Our study therefore reveals an unexpected specificity for this ribonuclease toward microRNA regulation, which is likely to be conserved in other eukaryotes and may be relevant to understanding its role in human disease.

MicroRNA function in Drosophila melanogaster

Over the last decade, microRNAs have emerged as critical regulators in the expression and function of animal genomes. This review article discusses the relationship between microRNA-mediated regulation and the biology of the fruit fly Drosophila melanogaster. We focus on the roles that microRNAs play in tissue growth, germ cell development, hormone action, and the development and activity of the central nervous system. We also discuss the ways in which microRNAs affect robustness. Many gene regulatory networks are robust; they are relatively insensitive to the precise values of reaction constants and concentrations of molecules acting within the networks. MicroRNAs involved in robustness appear to be nonessential under uniform conditions used in conventional laboratory experiments. However, the robust functions of microRNAs can be revealed when environmental or genetic variation otherwise has an impact on developmental outcomes.

Distinct cognitive effects and underlying transcriptome changes upon inhibition of individual miRNAs in hippocampal neurons

MicroRNAs (miRNA) are small, non-coding RNAs mediating post-transcriptional regulation of gene expression. miRNAs have recently been implicated in hippocampus-dependent functions such as learning and memory, although the roles of individual miRNAs in these processes remain largely unknown. Here, we achieved stable inhibition using AAV-delivered miRNA sponges of individual, highly expressed and brain-enriched miRNAs; miR-124, miR-9 and miR-34, in hippocampal neurons. Molecular and cognitive studies revealed a role for miR-124 in learning and memory. Inhibition of miR-124 resulted in an enhanced spatial learning and working memory capacity, potentially through altered levels of genes linked to synaptic plasticity and neuronal transmission. In contrast, inhibition of miR-9 or miR-34 led to a decreased capacity of spatial learning and of reference memory, respectively. On a molecular level, miR-9 inhibition resulted in altered expression of genes related to cell adhesion, endocytosis and cell death, while miR-34 inhibition caused transcriptome changes linked to neuroactive ligand-receptor transduction and cell communication. In summary, this study establishes distinct roles for individual miRNAs in hippocampal function.

Circulating miR-34a levels correlate with age-related hearing loss in mice and humans

Age-related hearing loss (AHL) is a progressive neurodegenerative disease that is largely silent in its initial stages. There is no sensitive blood biomarker for diagnosis or early detection of AHL. MicroRNAs (miRNAs or miRs) are abundant and highly stable in blood, and have been recently described as powerful circulating biomarkers in a wide range of diseases. In the present study, we identified concordant increases in miR-34a levels in the cochlea, auditory cortex, and plasma of C57BL/6 mice during aging. These increases were accompanied by elevated hearing thresholds and greater loss of hair cells. Levels of miR-34a targets, silent information regulator 1 (SIRT1), B-cell lymphoma-2 (Bcl-2), and E2F transcription factor 3 (E2F3), in the cochlea, auditory cortex, and plasma decreased with aging inversely to miR-34a. Moreover, plasma miR-34a levels were significantly higher in patients with AHL compared with controls who had normal hearing and had a receiver-operating characteristic curve that distinguished AHL patients from controls. However, SIRT1, Bcl-2, and E2F3 showed no correlation with AHL in humans. In summary, circulating miR-34a level may potentially serve as a useful biomarker for early detection of AHL.

MiR-298 Counteracts Mutant Androgen Receptor Toxicity in Spinal and Bulbar Muscular Atrophy

Spinal and bulbar muscular atrophy (SBMA) is a currently untreatable adult-onset neuromuscular disease caused by expansion of a polyglutamine repeat in the androgen receptor (AR). In SBMA, as in other polyglutamine diseases, a toxic gain of function in the mutant protein is an important factor in the disease mechanism; therefore, reducing the mutant protein holds promise as an effective treatment strategy. In this work, we evaluated a microRNA (miRNA) to reduce AR expression. From a list of predicted miRNAs that target human AR, we selected microRNA-298 (miR-298) for its ability to downregulate AR mRNA and protein levels when transfected in cells overexpressing wild-type and mutant AR and in SBMA patient-derived fibroblasts. We showed that miR-298 directly binds to the 3'-untranslated region of the human AR transcript, and counteracts AR toxicity in vitro. Intravenous delivery of miR-298 with adeno-associated virus serotype 9 vector resulted in efficient transduction of muscle and spinal cord and amelioration of the disease phenotype in SBMA mice. Our findings support the development of miRNAs as a therapeutic strategy for SBMA and other neurodegenerative disorders caused by toxic proteins.

miR-29c-3p promotes senescence of human mesenchymal stem cells by targeting CNOT6 through p53-p21 and p16-pRB pathways

Mesenchymal stem cells (MSCs) are important seed cells for tissue engineering and are promising targets for cell-based therapies. However, the replicative senescence of MSCs during in vitro culture limits their research and clinical applications. The molecular mechanisms underlying the replicative senescence of MSCs are not fully understood. Evidence suggests that miRNAs play important roles in replicative senescence. A microarray analysis found that the miR-29c-3p level was significantly increased during the MSC senescence process. In our study, we investigated the roles of miR-29c-3p in senescence of MSCs. We cultured MSCs for long periods of time, up and down-regulated the miR-29c-3p expression in MSCs, and examined the senescent phenotype changes. The over-expression of miR-29c-3p led to enhanced senescence-associated-β-galactosidase (SA-β-gal) staining, senescence associated secretory phenotype (SASP), senescence associated heterochromatic foci (SAHF), reduced proliferation ability, retarded osteogenic differentiation and corresponding changes in senescence markers, whereas the miR-29c-3p down-regulation had the opposite results. Dual-luciferase reporter assays demonstrated that CNOT6 is the target gene of miR-29c-3p. Knockdown of CNOT6 confirmed its inhibitory effects on the senescence of MSCs. In addition, Western blot results showed that both the p53-p21 and the p16-pRB pathways were activated during the miR-29c-3p-induced senescence of MSCs. In conclusion, our results demonstrate that miR-29c-3p promotes the senescence of MSCs by targeting CNOT6 through p53-p21 and p16-pRB pathways and highlight the contribution of post-transcriptional regulation to stem cell senescence.

Molecular biomarkers for chronological age in animal ecology

The chronological age of an individual animal predicts many of its biological characteristics, and these in turn influence population-level ecological processes. Animal age information can therefore be valuable in ecological research, but many species have no external features that allow age to be reliably determined. Molecular age biomarkers provide a potential solution to this problem. Research in this area of molecular ecology has so far focused on a limited range of age biomarkers. The most commonly tested molecular age biomarker is change in average telomere length, which predicts age well in a small number of species and tissues, but performs poorly in many other situations. Epigenetic regulation of gene expression has recently been shown to cause age-related modifications to DNA and to cause changes in abundance of several RNA types throughout animal lifespans. Age biomarkers based on these epigenetic changes, and other new DNA-based assays, have already been applied to model organisms, humans and a limited number of wild animals. There is clear potential to apply these marker types more widely in ecological studies. For many species, these new approaches will produce age estimates where this was previously impractical. They will also enable age information to be gathered in cross-sectional studies and expand the range of demographic characteristics that can be quantified with molecular methods. We describe the range of molecular age biomarkers that have been investigated to date and suggest approaches for developing the newer marker types as age assays in nonmodel animal species.

Role of microRNAs in the age-associated decline of pancreatic beta cell function in rat islets

AIMS/HYPOTHESIS

Ageing can lead to reduced insulin sensitivity and loss of pancreatic beta cell function, predisposing individuals to the development of diabetes. The aim of this study was to assess the contribution of microRNAs (miRNAs) to age-associated beta cell dysfunction.

METHODS

The global mRNA and miRNA profiles of 3- and 12-month-old rat islets were collected by microarray. The functional impact of age-associated differences in miRNA expression was investigated by mimicking the observed changes in primary beta cells from young animals.

RESULTS

Beta cells from 12-month-old rats retained normal insulin content and secretion, but failed to proliferate in response to mitotic stimuli. The islets of these animals displayed modifications at the level of several miRNAs, including upregulation of miR-34a, miR-124a and miR-383, and downregulation of miR-130b and miR-181a. Computational analysis of the transcriptomic modifications observed in the islets of 12-month-old rats revealed that the differentially expressed genes were enriched for miR-34a and miR-181a targets. Indeed, the induction of miR-34a and reduction of miR-181a in the islets of young animals mimicked the impaired beta cell proliferation observed in old animals. mRNA coding for alpha-type platelet-derived growth factor receptor, which is critical for compensatory beta cell mass expansion, is directly inhibited by miR34a and is likely to be at least partly responsible for the effects of this miRNA.

CONCLUSIONS/INTERPRETATION

Changes in the level of specific miRNAs that occur during ageing affect the proliferative capacity of beta cells. This might reduce their ability to expand under conditions of increased insulin demand, favouring the development of type 2 diabetes.

Analysis of MicroRNA Function in Drosophila

MicroRNAs are short noncoding, ~22-nucleotide RNAs that regulate protein abundance. The growth in our understanding of this class of RNAs has been rapid since their discovery just over a decade ago. We now appreciate that miRNAs are deeply embedded within the genetic networks that control basic features of metazoan cells including their identity, metabolism, and reproduction. The Drosophila melanogaster model system has made and will continue to make important contributions to this analysis. Intended as an introductory overview, here we review the current methods and resources available for functional analysis of fly miRNAs for those interested in performing this type of analysis.

Aberrant expression of microRNAs as biomarker for schizophrenia: from acute state to partial remission, and from peripheral blood to cortical tissue

Based on our previous finding of a seven-miRNA (hsa-miR-34a, miR-449a, miR-564, miR-432, miR-548d, miR-572 and miR-652) signature as a potential biomarker for schizophrenia, this study aimed to examine if hospitalization could affect expressions of these miRNAs. We compared their expression levels between acute state and partial remission state in people with schizophrenia (n=48) using quantitative PCR method. Further, to examine whether the blood and brain show similar expression patterns, the expressions of two miRNAs (hsa-miR-34a and hsa-miR-548d) were examined in the postmortem brain tissue of people with schizophrenia (n=25) and controls (n=27). The expression level of the seven miRNAs did not alter after ~2 months of hospitalization with significant improvement in clinical symptoms, suggesting the miRNAs could be traits rather than state-dependent markers. The aberrant expression seen in the blood of hsa-miR-34a and hsa-miR-548d were not present in the brain samples, but this does not discount the possibility that the peripheral miRNAs could be clinically useful biomarkers for schizophrenia. Unexpectedly, we found an age-dependent increase in hsa-miR-34a expressions in human cortical (Brodmann area 46 (BA46)) but not subcortical region (caudate putamen). The correlation between hsa-miR-34a expression level in BA46 and age was much stronger in the controls than in the cases, and the corresponding correlation in the blood was only seen in the cases. The association between the miRNA dysregulations, the disease predisposition and aging warrants further investigation. Taken together, this study provides further insight on the candidate peripheral miRNAs as stable biomarkers for the diagnostics of schizophrenia.

Transcriptome analysis in calorie-restricted rats implicates epigenetic and post-translational mechanisms in neuroprotection and aging

BACKGROUND

Caloric restriction (CR) can increase longevity in rodents and improve memory function in humans. α-Lipoic acid (LA) has been shown to improve memory function in rats, but not longevity. While studies have looked at survival in rodents after switching from one diet to another, the underlying mechanisms of the beneficial effects of CR and LA supplementation are unknown. Here, we use RNA-seq in cerebral cortex from rats subjected to CR and LA-supplemented rats to understand how changes in diet can affect aging, neurodegeneration and longevity.

RESULTS

Gene expression changes during aging in ad libitum-fed rats are largely prevented by CR, and neuroprotective genes are overexpressed in response to both CR and LA diets with a strong overlap of differentially expressed genes between the two diets. Moreover, a number of genes are differentially expressed specifically in rat cohorts exhibiting diet-induced life extension. Finally, we observe that LA supplementation inhibits histone deacetylase (HDAC) protein activity in vitro in rat astrocytes. We find a single microRNA, miR-98-3p, that is overexpressed during CR feeding and LA dietary supplementation; this microRNA alters HDAC and histone acetyltransferase (HAT) activity, which suggests a role for HAT/HDAC homeostasis in neuroprotection.

CONCLUSIONS

This study presents extensive data on the effects of diet and aging on the cerebral cortex transcriptome, and also emphasises the importance of epigenetics and post-translational modifications in longevity and neuroprotection.

Changes in Regenerative Capacity through Lifespan

Most organisms experience changes in regenerative abilities through their lifespan. During aging, numerous tissues exhibit a progressive decline in homeostasis and regeneration that results in tissue degeneration, malfunction and pathology. The mechanisms responsible for this decay are both cell intrinsic, such as cellular senescence, as well as cell-extrinsic, such as changes in the regenerative environment. Understanding how these mechanisms impact on regenerative processes is essential to devise therapeutic approaches to improve tissue regeneration and extend healthspan. This review offers an overview of how regenerative abilities change through lifespan in various organisms, the factors that underlie such changes and the avenues for therapeutic intervention. It focuses on established models of mammalian regeneration as well as on models in which regenerative abilities do not decline with age, as these can deliver valuable insights for our understanding of the interplay between regeneration and aging.

Identification of differentially expressed microRNAs between Bacillus thuringiensis Cry1Ab-resistant and -susceptible strains of Ostrinia furnacalis

The Asian corn borer (ACB), Ostrinia furnacalis (Guenée), can develop strong resistance to Cry1Ab, the most widely commercialized Cry toxin for Bt maize worldwide. It is essential to understand the mechanism of resistance for management of this species, but information on the post-transcriptional regulation of Bt resistance in this target insect is limited. In the present study, RNA was extracted from the ACB in various larval stages (1–5 instar) from Cry1Ab-sensitive (ACB-BtS) and -resistant (ACB-AbR) strains, each of which included two biological replicates. Using Illumina sequencing, a total of 23,809,890 high-quality reads were collected from the four ACB libraries. The numbers of known microRNAs (miRNAs) were 302 and 395 for ACB-BtS and 268 and 287 for ACB-AbR. Using Mireap software, we identified 32 and 16 potential novel miRNAs for ACB-BtS and 18 and 22 for ACB-AbR. Among them, 21 known and 1 novel miRNAs had significantly different expression between ACB-BtS and ACB-AbR. Several miRNAs were observed to target potential Bt receptor genes, such as aminopeptidase N and cadherin-like protein. The glycosylphosphatidylinositol-anchor biosynthetic process and ABC transporters pathway were identified through Gene Ontology and KEGG pathway analysis of target genes of the differentially expressed miRNAs.

Expression Change of miR-214 and miR-135 during Muscle Differentiation

Objective

MicroRNAs (miRNAs) are a class of small non-coding RNAs that play pivotal roles in many biological processes such as regulating skeletal muscle development where alterations in miRNA expression are reported during myogenesis. In this study, we aimed to investigate the impact of predicted miRNAs and their target genes on the myoblast to myocyte differentiation process.

Materials and Methods

This experimental study was conducted on the C2C12 cell line. Using a bioinformatics approach, miR-214 and miR-135 were selected according to their targets as potential factors in myoblast to myocyte differentiation induced by 3% horse serum. Immunocytochemistry (ICC) was undertaken to confirm the differentiation process and quantitative real-time polymerase chain reaction (PCR) to determine the expression level of miRNAs and their targets.

Results

During myoblast to myocyte differentiation, miR-214 was significantly down- regulated while miRNA-135, Irs2, Akt2 and Insr were overexpressed during the process.

Conclusion

miR-214 and miR-135 are potential regulators of myogenesis and are involved in skeletal muscle development through regulating the IRS/PI3K pathway.

Drosophila as an In Vivo Model for Human Neurodegenerative Disease

With the increase in the ageing population, neurodegenerative disease is devastating to families and poses a huge burden on society. The brain and spinal cord are extraordinarily complex: they consist of a highly organized network of neuronal and support cells that communicate in a highly specialized manner. One approach to tackling problems of such complexity is to address the scientific questions in simpler, yet analogous, systems. The fruit fly, Drosophila melanogaster, has been proven tremendously valuable as a model organism, enabling many major discoveries in neuroscientific disease research. The plethora of genetic tools available in Drosophila allows for exquisite targeted manipulation of the genome. Due to its relatively short lifespan, complex questions of brain function can be addressed more rapidly than in other model organisms, such as the mouse. Here we discuss features of the fly as a model for human neurodegenerative disease. There are many distinct fly models for a range of neurodegenerative diseases; we focus on select studies from models of polyglutamine disease and amyotrophic lateral sclerosis that illustrate the type and range of insights that can be gleaned. In discussion of these models, we underscore strengths of the fly in providing understanding into mechanisms and pathways, as a foundation for translational and therapeutic research.

Role of miR-34c in ketamine-induced neurotoxicity in neonatal mice hippocampus

Ketamine is a commonly used pediatric anesthetic, but it might affect development, or even induce neurotoxicity in the neonatal brain. We have used an in vivo neonatal mouse model to induce ketamine-related neurotoxicity in the hippocampus, and found that miR-34c, a microRNA associated with pathogenesis of Alzheimer's disease, was significantly upregulated during ketamine-induced hippocampal neurodegeneration. Functional assay of silencing miR-34c demonstrated that downregulation of miR-34c activated PKC-ERK pathway, upregulated anti-apoptotic protein BCL2, and ameliorated ketamine-induced apoptosis in the hippocampus. Cognitive examination with the Morris water maze test showed that ketamine-induced memory impairment was significantly improved by miR-34c downregulation. Thus, miR-34c is important in regulating ketamine-induced neurotoxicity in hippocampus.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

A transgenic resource for conditional competitive inhibition of conserved Drosophila microRNAs

Although the impact of microRNAs (miRNAs) in development and disease is well established, understanding the function of individual miRNAs remains challenging. Development of competitive inhibitor molecules such as miRNA sponges has allowed the community to address individual miRNA function in vivo. However, the application of these loss-of-function strategies has been limited. Here we offer a comprehensive library of 141 conditional miRNA sponges targeting well-conserved miRNAs in Drosophila. Ubiquitous miRNA sponge delivery and consequent systemic miRNA inhibition uncovers a relatively small number of miRNA families underlying viability and gross morphogenesis, with false discovery rates in the 4-8% range. In contrast, tissue-specific silencing of muscle-enriched miRNAs reveals a surprisingly large number of novel miRNA contributions to the maintenance of adult indirect flight muscle structure and function. A strong correlation between miRNA abundance and physiological relevance is not observed, underscoring the importance of unbiased screens when assessing the contributions of miRNAs to complex biological processes.

Investigation of Gene Regulatory Networks Associated with Autism Spectrum Disorder Based on MiRNA Expression in China

Autism spectrum disorder (ASD) comprise a group of neurodevelopmental disorders characterized by deficits in social and communication capacities and repetitive behaviors. Increasing neuroscientific evidence indicates that the neuropathology of ASD is widespread and involves epigenetic regulation in the brain. Differentially expressed miRNAs in the peripheral blood from autism patients were identified by high-throughput miRNA microarray analyses. Five of these miRNAs were confirmed through quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. A search for candidate target genes of the five confirmed miRNAs was performed through a Kyoto encyclopedia of genes and genomes (KEGG) biological pathways and Gene Ontology enrichment analysis of gene function to identify gene regulatory networks. To the best of our knowledge, this study provides the first global miRNA expression profile of ASD in China. The differentially expressed miR-34b may potentially explain the higher percentage of male ASD patients, and the aberrantly expressed miR-103a-3p may contribute to the abnormal ubiquitin-mediated proteolysis observed in ASD.

The exonuclease Nibbler regulates age-associated traits and modulates piRNA length in Drosophila

Nibbler (Nbr) is a 3'-to-5' exonuclease that trims the 3'end of microRNAs (miRNAs) to generate different length patterns of miRNAs in Drosophila. Despite its effect on miRNAs, we lack knowledge of its biological significance and whether Nbr affects other classes of small RNAs such as piRNAs and endo-siRNAs. Here, we characterized the in vivo function of nbr by defining the Nbr protein expression pattern and loss-of-function effects. Nbr protein is enriched in the ovary and head. Analysis of nbr null animals reveals adult-stage defects that progress with age, including held-up wings, decreased locomotion, and brain vacuoles, indicative of accelerated age-associated processes upon nbr loss. Importantly, these effects depend on catalytic residues in the Nbr exonuclease domain, indicating that the catalytic activity is responsible for these effects. Given the impact of nbr on miRNAs, we also analyzed the effect of nbr on piRNA and endo-siRNA lengths by deep-sequence analysis of libraries from ovaries. As with miRNAs, nbr mutation led to longer length piRNAs - an effect that was dependent on the catalytic residues of the exonuclease domain. These analyses indicate a role of nbr on age-associated processes and to modulate length of multiple classes of small RNAs including miRNAs and piRNAs in Drosophila.

Polymorphisms Falling Within Putative miRNA Target Sites in the 3'UTR Region of SIRT2 and DRD2 Genes Are Correlated With Human Longevity

Many studies have suggested that individual differences in aging phenotypes may be associated to polymorphisms affecting gene regulation. As single-nucleotide polymorphisms (SNPs) in the 3'-untranslated regions (3'UTR) targeted by microRNAs (miRNAs) can alter the strength of miRNA binding (and, consequently, the regulation of target genes), we wondered whether these SNPs (known as miRSNPs) affect the individual chance to become long-lived. Thus, we estimated the effect of miRSNPs falling in the 3'-untranslated regions of 140 aging-related genes on the DNA/miRNA bond. The 24 miRSNPs with the highest difference of binding energy between the two alleles were then investigated for their association with longevity by case-control analysis. Two SNPs,SIRT2-rs45592833 G/T and DRD2-rs6276 A/G, provided a significant association with human longevity, also after correcting for multiple comparisons. For both SNPs, the minor allele was associated with a significantly decreased chance to became long-lived in an allele dose-dependent manner (p= 1.090 × 10(-6)and 1.964 × 10(-4)forSIRT2 and DRD2, respectively). The results indicate that the individual aging phenotype may be affected by the variability of specific miRNA targeted regions, as shown for SIRT2 and DRD2, and may suggest further studies to analyze the variability of gene expression regulation as a modulator of aging phenotypes.

Resveratrol inhibits dysfunction of dendritic cells from chronic obstructive pulmonary disease patients through promoting miR-34

BACKGROUND

Resveratrol has demonstrated many beneficial effects against aging, including anti-inflammatory and antioxidant roles. The present study was designed to observe the effects of resveratrol on the dysfunction of dendritic cells (DCs) from COPD patients and its possible mechanism and use in the treatment for COPD.

METHODS

Flow cytometry analysis was used to examine the expression of costimulatory markers CD80 and CD86 and ELISA was used to examine the secretion of IFN-α. Expression of miR-34 was examined by using real-time PCR. Expression vector of miR-34, LV3-miR-34 was also constructed and transfected into DCs to observe the effects on functions of DCs.

RESULTS

The results showed that there was remarkable upregulation of CD80 and CD86 and secretion of cytokines IFN-α in DCs from COPD patients. Resveratrol displayed a dose-dependent cytotoxicity action over 10 µg/mL and pretreatment with resveratrol inhibited upregulation of CD80 and CD86 and secretion of cytokines IFN-α. Further study showed resveratrol upregulated the expression of miR-34, which inhibited the dysfunction of DCs.

CONCLUSION

These proofs suggest that resveratrol inhibited dysfunction of DCs from COPD patients through promoting miR-34.

Up-Regulation of miR-34a Expression in Response to the Luteolin-Induced Neurite Outgrowth of PC12 Cells

Luteolin (3',4',5,7-tetrahydroxyflavone), a flavonoid found in several vegetables and fruits, has been reported to possess neurotrophic activities that are associated with its capacity to promote neuronal survival and differentiation. In the present study, we report for the first time a genomewide screen for microRNAs (miRNAs) regulated during the luteolin-mediated neurite outgrowth of PC12 cells. We found that after luteolin treatment, the abundance of 16 miRNAs was markedly up-regulated and that of 3 miRNAs was down-regulated in PC12 cells. The induction of miR-34a by luteolin was the most pronounced among these differentially expressed miRNAs. The correlation between miR-34a down-regulation and decreased luteolin-mediated neurite outgrowth may indicate a mechanism by which miR-34a may act as a modulator of neuronal differentiation. Furthermore, we found that luteolin enhanced the phosphorylation of p53 at Ser15, which was associated with the promotion of miR-34a transcription and neurite outgrowth. Moreover, the level of sirtuin 1 (SIRT1), a known miR-34a target, was reduced during luteolin-induced neurite outgrowth. In turn, the level of acetylated p53, a substrate of SIRT1, was correspondingly increased in luteolin-treated PC12 cells. In addition to p53 activation, we further identified that luteolin-induced miR-34a transcription and neurite outgrowth involved the activation of the JNK and p38 MAPK pathways. However, the inhibition of JNK and p38 MAPK activation did not block luteolin-induced p53 activation in PC12 cells. Our findings suggested that the activation of both p53-dependent and p53-independent miR-34a/SIRT1 pathways plays a critical role in the mechanisms underlying luteolin-induced neuritogenesis.

MiR-34a suppresses ovarian cancer proliferation and motility by targeting AXL

Increasing evidence has suggested that dysregulation of microRNAs (miRNAs) could contribute to tumor progression. The miR-34 family is directly transactivated by tumor suppressor p53 which is frequently mutated in various cancers; however, the effect of miR-34a on the ovarian cancer cells remains unclear. The aim of the paper was to study the expression of miR-34a in ovarian cancer and miR-34a's relation to the cell proliferation and metastasis in ovarian cancer in vitro. miR-34a expression was determined by quantitative RT-PCR in a panel of 60 human ovarian cancer samples. Functional characterization of miR-34a was accomplished by reconstitution of miR-34a expression in ovarian cancer cells by determining changes in proliferation, migration, and invasion. Our results showed that miR-34a is downregulated in ovarian cancer tissues compared with the corresponding adjacent non-neoplastic tissues, and the expression level of miR-34a was significantly lower in ovarian cancer cell lines in comparison with normal human fallopian tube epithelial cell line. The 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-diphenytetrazoliumromide (MTT) assay revealed significant cell proliferation inhibition in miR-34a transfectant compared with the control from HO8910 and SKOV3 cells, which displayed lowest expressions of miR-34a. Furthermore, the transwell assay also showed significant cell migration inhibition in miR-34a transfectant, compared with cell lines transfected with NC. Overexpression of miR-34a led to the inhibition of AXL expression, indicating that AXL is a target gene for miR-34a. Our data suggest that miR-34a may function as a tumor suppressor through repression of oncogenic AXL in ovarian cancer.

Dynamic expression of miRNAs across immature and adult stages of the malaria mosquito Anopheles stephensi

Background

MicroRNAs are small non-coding RNAs that are involved in various biological processes including insect development. Anopheles stephensi serves as primary vector of malaria parasite in Asia and exhibits holometabolous life cycle that involves four different stages of development. Regulation and role of mosquito miRNAs during various stages of mosquito development remain largely unknown.

Methods

High throughput small RNA sequencing was employed for identification and profiling of miRNAs across immature and adult stages of malaria vector, which were further validated using Northern hybridization and real time PCR. Target prediction and pathway analysis was carried out to understand the role of regulated miRNAs in insect development. Degradome sequencing was employed to identify cleaved targets of some regulated miRNAs. Loss of function strategy was employed for miR-989 to understand its probable role in female reproductive process.

Results

Small RNA sequencing and data analysis revealed 111 and 14 known and novel miRNAs respectively across all stages of Anopheles stephensi. Nine miRNAs showed gender specific regulation across different stages of mosquito development. Analysis of miRNAs revealed regulation of 24 and 26 miRNAs across different stages of male and female mosquito development respectively. mRNA targets and significant pathways targeted by regulated miRNAs were identified for each stage of mosquito development. Degradome sequencing revealed twenty nine cleaved targets of insect miRNAs. MicroRNA-989 showed significant up-regulation in the adult female as compared to adult male mosquito. Knockdown of miR-989 expression in adult female using miRNA specific antagomir affected targets playing roles in protein binding, proteolysis and nucleic acid binding in ovary tissue of female mosquito post blood feeding.

Conclusions

This is the first comprehensive effort to understand regulation of Anopheles stephensi miRNAs across developmental stages of male and female mosquito. Preliminary role of regulated miRNAs in mosquito development was revealed by target prediction and pathway analysis. MicroRNA-989 emerged to have important roles in adult female mosquitoes showing significant up-regulation which was further studied using miR-989 specific antagomir. This study provides insights into mosquito development and reproductive process and has implications for effective control of mosquito population required for reducing spread of mosquito-borne infectious diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0772-y) contains supplementary material, which is available to authorized users.

Comparison of senescence-associated miRNAs in primary skin and lung fibroblasts

MicroRNAs are non-coding RNAs with roles in many cellular processes. Tissue-specific miRNA profiles associated with senescence have been described for several cell and tissue types. We aimed to characterise miRNAs involved in core, rather than tissue-specific, senescence pathways by assessment of common miRNA expression differences in two different cell types, with follow-up of predicted targets in human peripheral blood. MicroRNAs were profiled in early and late passage primary lung and skin fibroblasts to identify commonly-deregulated miRNAs. Expression changes of their bioinformatically-predicted mRNA targets were then assessed in both cell types and in human peripheral blood from elderly participants in the InCHIANTI study. 57/178 and 26/492 microRNAs were altered in late passage skin and lung cells respectively. Three miRNAs (miR-92a, miR-15b and miR-125a-3p) were altered in both tissues. 14 mRNA targets of the common miRNAs were expressed in lung and skin fibroblasts, of which two demonstrated up-regulation in late passage skin and lung cells (LYST; p = 0.02 [skin] and 0.02 [lung] INMT; p = 0.03 [skin] and 0.04 [lung]). ZMPSTE24 and LHFPL2 demonstrated altered expression in late passage skin cells only (p = 0.01 and 0.05 respectively). LHFPL2 was also positively correlated with age in peripheral blood (p value = 6.6 × 10(-5)). We find that the majority of senescence-associated miRNAs demonstrate tissue-specific effects. However, miRNAs showing common effects across tissue types may represent those associated with core, rather than tissue-specific senescence processes.

Identification of age- and disease-related alterations in circulating miRNAs in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized clinically by the progressive decline of memory and cognition. Histopathologically, two main hallmarks have been identified in AD: amyloid-β peptide extracellular neuritic plaques and neurofibrillary tangles formed by posttranslational modified tau protein. A definitive diagnosis can only be achieved after the post mortem verification of the histological mentioned alterations. Therefore, the development of biomarkers that allow an early diagnosis and/or predict disease progression is imperative. The prospect of a blood-based biomarker is possible with the finding of circulating microRNAs (miRNAs), a class of small non-coding RNAs of 22-25 nucleotides length that regulate mRNA translation rate. miRNAs travel through blood and recent studies performed in potential AD cases suggest the possibility of finding pathology-associated differences in circulating miRNA levels that may serve to assist in early diagnosis of the disease. However, these studies analyzed samples at a single time-point, limiting the use of miRNAs as biomarkers in AD progression. In this study we evaluated miRNA levels in plasma samples at different time-points of the evolution of an AD-like pathology in a transgenic mouse model of the disease (3xTg-AD). We performed multiplex qRT-PCR and compared the plasmatic levels of 84 miRNAs previously associated to central nervous system development and disease. No significant differences were detected between WT and transgenic young mice. However, age-related significant changes in miRNA abundance were observed for both WT and transgenic mice, and some of these were specific for the 3xTg-AD. In agreement, variations in the levels of particular miRNAs were identified between WT and transgenic old mice thus suggesting that the age-dependent evolution of the AD-like pathology, rather than the presence and expression of the transgenes, modifies the circulating miRNA levels in the 3xTg-AD mice.

A neuroprotective role for microRNA miR-1000 mediated by limiting glutamate excitotoxicity

Evidence has begun to emerge for microRNAs as regulators of synaptic signaling, specifically acting to control postsynaptic responsiveness during synaptic transmission. In this report, we provide evidence that Drosophila melanogaster miR-1000 acts presynaptically to regulate glutamate release at the synapse by controlling expression of the vesicular glutamate transporter (VGlut). Genetic deletion of miR-1000 led to elevated apoptosis in the brain as a result of glutamatergic excitotoxicity. The seed-similar miR-137 regulated VGluT2 expression in mouse neurons. These conserved miRNAs share a neuroprotective function in the brains of flies and mice. Drosophila miR-1000 showed activity-dependent expression, which might serve as a mechanism to allow neuronal activity to fine-tune the strength of excitatory synaptic transmission.