Intact p53-dependent responses in miR-34-deficient mice

A comparison of the expression patterns and diagnostic capability of the ncRNAs NEAT1 and miR-34a in non-obstructive azoospermia and severe oligospermia

Infertility is a major global health problem, affecting 8-12% of couples worldwide, with male causes contributing to approximately 50% of cases. Notably, around 15% of infertile men are azoospermic. Consequently, there is a critical necessity to find noninvasive biomarkers to help in diagnosing and assessing the susceptibility of patients with various infertility disorders. This study is designed to determine the roles of NEAT1 and miR-34a as diagnostic and susceptibility biomarkers for non-obstructive azoospermia and severe oligospermia. The interactions between these non-coding RNA (ncRNAs) were explored, along with their correlations to hormonal profiles and clinical parameters like sperm count and motility. The potential of serum NEAT1 and miR-34a as diagnostic biomarkers for these conditions was explored. The study included 100 participants: 40 non-obstructive azoospermia patients, 40 severe oligospermia patients, and 20 healthy controls. Quantitative real-time PCR and transcriptomics-based bioinformatics tools were employed to explore the co-expression networks and molecular interactions of NEAT1, miR-34a, SIRT1, and their associated hormonal and genetic pathways. Results indicated that NEAT1 was significantly downregulated in severe oligospermia patients, while its levels in non-obstructive azoospermia patients did not differ significantly from healthy controls. Furthermore, serum miR-34a expression was considerably upregulated in both patient groups compared to controls. This study highlights the promise of serum NEAT1 and miR-34a as diagnostic markers for non-obstructive azoospermia and severe oligospermia. These findings provide valuable insights into male infertility and indicate potential avenues for personalized treatment strategies.

MicroRNA-34a suppresses KLF2 to promote pathological angiogenesis through the CXCR4/CXCL12 pathway in age-related macular degeneration

Age-related macular degeneration (AMD), characterized by pathologic choroidal neovascularization (CNV), is a leading cause of vision loss in the elderly. Vascular endothelial growth factor A (VEGFa) antagonists can prevent acute vision loss, but high treatment burden and loss of efficacy with chronic therapy highlight the need to explore alternative mechanisms. Recently, microRNA-34a (miR-34a) has emerged as a key regulator in aging and age-related diseases, but its role in neovascular AMD is unclear. In an injury-induced murine CNV model, we discovered miR-34a promoted pathological angiogenesis, without altering expression of Vegfa or its receptor Kdr, the canonical regulators of CNV. Mechanistically, miR-34a directly targets and inhibits the transcription factor KLF2 thereby upregulating the pro-angiogenic factors CXCR4 and CXCL12. Finally, we show miR-34a exacerbates CNV in aged mice and is expressed in CNV lesions excised from wet AMD patients. These findings establish a causal link between the age-related miR-34a and neovascularization in AMD.

Teaser

Identification of a molecular mechanism involved in the pathogenesis of a prevalent and debilitating age-related ocular disease.

In silico identification of novel pre-microRNA genes in Rift valley fever virus suggest new pathomechanisms for embryo-fetal dysgenesis

MicroRNAs (miRNAs) are small non-coding RNAs that regulate the post-transcriptional expression of target genes. Virus-encoded miRNAs play an important role in the replication of viruses, modulate gene expression in both the virus and host, and affect their persistence and immune evasion in hosts. This renders viral miRNAs as potential targets for therapeutic applications, especially against pathogenic viruses that infect humans and animals. Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic RNA virus that causes severe disease in both humans and livestock. High mortality among newborn lambs and abortion storms are key characteristics of an RVF outbreak. To date, limited information is available on RVFV-derived miRNAs. In this study, computational methods were used to analyse the RVFV genome for putative pre-miRNA genes, which were then analysed for the presence of mature miRNAs. We detected 19 RVFV-encoded miRNAs and identified their potential mRNAs targets in sheep (Ovis aries), the most susceptible host. The identification of significantly enriched O. aries genes in association with RVFV miRNAs will help elucidate the molecular mechanisms underlying RVFV pathogenesis and potentially uncover novel drug targets for RVFV.

The circulatory levels and bone expression of MIR21, 34a, 155 and their target genes in a section of Egyptian Population

Bone tissue is constantly regenerated and repaired through a finely balanced process known as bone remodeling. Many miRNAs act as regulators of the signaling pathways involved in bone metabolic processes to maintain tissue homeostasis. This study aimed to assess the circulating levels of MIR21, MIR34a, and MIR155 in human serum and their bone expression, and the expression of bone turnover-related genes which can reflect the bone quality. This prospective study was conducted on 60 patients (30 males and 30 females) indicated for surgical interventions for neural decompression +/- fixation. Relative quantification of expression of MIR21, miR34a, and MIR155 and bone related genes was assayed using PCR. The serum levels of osteocalcin and Serum Bone Alkaline Phosphatase (sBAP) were assayed using a human ELISA kit. The main finding of the present work was the strong positive association between the circulating levels of only miR21 and MIR155 and their bone expression in the population under study and with bone markers and target genes Also, a positive association was found between both bone expression and circulating MIR21 levels with age and sBAP. These results suggest that the circulating levels of these microRNAs as early markers for the predication of bone quality.

Genetic mechanisms of multiciliated cell development: from fate choice to differentiation in zebrafish and other models

Multiciliated cells (MCCS) form bundles of cilia and their activities are essential for the proper development and physiology of many organ systems. Not surprisingly, defects in MCCs have profound consequences and are associated with numerous disease states. Here, we discuss the current understanding of MCC formation, with a special focus on the genetic and molecular mechanisms of MCC fate choice and differentiation. Furthermore, we cast a spotlight on the use of zebrafish to study MCC ontogeny and several recent advances made in understanding MCCs using this vertebrate model to delineate mechanisms of MCC emergence in the developing kidney.

miR-34a is a tumor suppressor in zebrafish and its expression levels impact metabolism, hematopoiesis and DNA damage

Li-Fraumeni syndrome is caused by inherited TP53 tumor suppressor gene mutations. MicroRNA miR-34a is a p53 target and modifier gene. Interestingly, miR-34 triple-null mice exhibit normal p53 responses and no overt cancer development, but the lack of miR-34 promotes tumorigenesis in cancer-susceptible backgrounds. miR-34 genes are highly conserved and syntenic between zebrafish and humans. Zebrafish miR-34a and miR-34b/c have similar expression timing in development, but miR-34a is more abundant. DNA damage by camptothecin led to p53-dependent induction of miR-34 genes, while miR-34a mutants were adult-viable and had normal DNA damage-induced apoptosis. Nevertheless, miR-34a-/- compound mutants with a gain-of-function tp53R217H/ R217H or tp53-/- mutants were more cancer-prone than tp53 mutants alone, confirming the tumor-suppressive function of miR-34a. Through transcriptomic comparisons at 28 hours post-fertilization (hpf), we characterized DNA damage-induced transcription, and at 8, 28 and 72 hpf we determined potential miR-34a-regulated genes. At 72 hpf, loss of miR-34a enhanced erythrocyte levels and up-regulated myb-positive hematopoietic stem cells. Overexpression of miR-34a suppressed its reporter mRNA, but not p53 target induction, and sensitized injected embryos to camptothecin but not to γ-irradiation.

Targeted therapy using nanocomposite delivery systems in cancer treatment: highlighting miR34a regulation for clinical applications

The clinical application of microRNAs in modern therapeutics holds great promise to uncover molecular limitations and conquer the unbeatable castle of cancer metastasis. miRNAs play a decisive role that regulating gene expression at the post-transcription level while controlling both the stability and translation capacity of mRNAs. Specifically, miR34a is a master regulator of the tumor suppressor gene, cancer progression, stemness, and drug resistance at the cell level in p53-dependent and independent signaling. With changing, trends in nanotechnology, in particular with the revolution in the field of nanomedicine, nano drug delivery systems have emerged as a prominent strategy in clinical practices coupled with miR34a delivery. Recently, it has been observed that forced miR34a expression in human cancer cell lines and model organisms limits cell proliferation and metastasis by targeting several signaling cascades, with various studies endorsing that miR34a deregulation in cancer cells modulates apoptosis and thus requires targeted nano-delivery systems for cancer treatment. In this sense, the present review aims to provide an overview of the clinical applications of miR34a regulation in targeted therapy of cancer.

In vivo functions of miRNAs in mammalian spermatogenesis

MicroRNAs (miRNAs) are believed to play important roles in mammalian spermatogenesis mainly because spermatogenesis is more or less disrupted when genes encoding key enzymes for miRNA biogenesis are mutated. However, it is challenging to study the functions of individual miRNAs due to their family-wise high sequence similarities and the clustered genomic distributions of their genes, both of which expose difficulties in using genetic methods. Accumulating evidence shows that a number of miRNAs indeed play important roles in mammalian spermatogenesis and the underlying mechanisms start to be understood. In this mini review, we focus on highlighting the roles of miRNAs in mammalian spermatogenesis elucidated mainly by using in vivo genetic methods and on discussing the underlying mechanisms. We propose that studies on the roles of miRNAs in spermatogenesis should and can be conducted in a more fruitful way given the progress in traditional methods and the birth of new technologies.

Targeting epigenetic regulators to overcome drug resistance in cancers

Drug resistance is mainly responsible for cancer recurrence and poor prognosis. Epigenetic regulation is a heritable change in gene expressions independent of nucleotide sequence changes. As the common epigenetic regulation mechanisms, DNA methylation, histone modification, and non-coding RNA regulation have been well studied. Increasing evidence has shown that aberrant epigenetic regulations contribute to tumor resistance. Therefore, targeting epigenetic regulators represents an effective strategy to reverse drug resistance. In this review, we mainly summarize the roles of epigenetic regulation in tumor resistance. In addition, as the essential factors for epigenetic modifications, histone demethylases mediate the histone or genomic DNA modifications. Herein, we comprehensively describe the functions of the histone demethylase family including the lysine-specific demethylase family, the Jumonji C-domain-containing demethylase family, and the histone arginine demethylase family, and fully discuss their regulatory mechanisms related to cancer drug resistance. In addition, therapeutic strategies, including small-molecule inhibitors and small interfering RNA targeting histone demethylases to overcome drug resistance, are also described.

The long-lasting effects of early life adversities are sex dependent: The signature of miR-34a

BACKGROUND

Exposure to early life adversities (ELA) can influence a plethora of biological mechanisms leading to stress-related disorders later in life through epigenetic mechanisms, such as microRNAs (miRs). MiR-34 is a critical modulator of stress response and stress-induced pathologies and a link between ELA and miR-34a has been reported.

METHODS

Here using our well-established model of ELA (Repeated Cross Fostering) we investigate the behavioral long-term effects of ELA in male and female mice. We also assess basal and ELA-induced miR-34a expression in adult mice and investigate whether ELA affects the later miR-34a response to adult acute stress exposure across brain areas (medial preFrontal Cortex, Dorsal Raphe Nuclei) and peripheral organs (heart, plasma) in animals from both sexes. Finally, based on our previous data demonstrating the critical role of Dorsal Raphe Nuclei miR-34a expression in serotonin (5-HT) transmission, we also investigated prefrontal-accumbal 5-HT outflow induced by acute stress exposure in ELA and Control females by in vivo intracerebral microdialysis.

RESULTS

ELA not just induces a depressive-like state as well as enduring changes in miR-34a expression, but also alters miR-34a expression in response to adult acute stress exclusively in females. Finally, altered DRN miR-34a expression is associated with prefrontal-accumbal 5-HT release under acute stress exposure in females.

LIMITATIONS

Translational study on humans is necessary to verify the results obtained in our animal models of ELA-induced depression.

CONCLUSIONS

This is the first evidence showing long-lasting sex related effects of ELA on brain and peripheral miR-34a expression levels in an animal model of depression-like phenotype.

Synthetic miR-34a against solid tumours: a predictable failure

A prolific scientific literature attributes pro- or anti-oncogenic properties to many human microRNAs ("miRNAs"). While many of these studies are based on unpersuasive analyses, one candidate suppressor tumour miRNA, miR-34a, appeared convincing enough to be administered to human patients in a clinical trial-with disappointing outcomes. Here, we review possible reasons for that failure, and their implications for other miRNAs.

MicroRNAs in doxorubicin-induced cardiotoxicity: The DNA damage response

Doxorubicin (DOX) is a chemotherapeutic drug widely used for cancer treatment, but its use is limited by cardiotoxicity. Although free radicals from redox cycling and free cellular iron have been predominant as the suggested primary pathogenic mechanism, novel evidence has pointed to topoisomerase II inhibition and resultant genotoxic stress as the more fundamental mechanism. Recently, a growing list of microRNAs (miRNAs) has been implicated in DOX-induced cardiotoxicity (DIC). This review summarizes miRNAs reported in the recent literature in the context of DIC. A particular focus is given to miRNAs that regulate cellular responses downstream to DOX-induced DNA damage, especially p53 activation, pro-survival signaling pathway inhibition (e.g., AMPK, AKT, GATA-4, and sirtuin pathways), mitochondrial dysfunction, and ferroptosis. Since these pathways are potential targets for cardioprotection against DOX, an understanding of how miRNAs participate is necessary for developing future therapies.

Csf1r mediates enhancement of intestinal tumorigenesis caused by inactivation of Mir34a

The CSF1 receptor (CSF1R) encoding mRNA represents a direct target of miR-34a. However, the in vivo relevance of the suppression of CSF1R by miR-34a for intestinal tumor suppression mediated by the p53/miR-34a pathway has remained unknown. Here, Apc^Min/+ mice with intestinal-epithelial cell (IEC)-specific deletions of Mir34a showed increased formation of adenomas and decreased survival, whereas deletion of Csf1r decreased adenoma formation and increased survival. In adenomas deletion of Mir34a enhanced proliferation, STAT3 signaling, infiltration with fibroblasts, immune cells and microbes, and tumor stem cell abundance and decreased apoptosis. Deletion of Csf1r had the opposite effects. In addition, homeostasis of intestinal secretory and stem cells, and tumoroid formation were affected in opposite directions by deletion of Mir34a and CSF1R. Concomitant deletion of Csf1r and Mir34a neutralized the effects of the single deletions. mRNAs containing Mir34a seed-matching sites, which encode proteins related to EMT (epithelial-mesenchymal transition), stemness and Wnt signaling, were enriched after Mir34a inactivation in adenomas and derived tumoroids. Netrin-1/Ntn1 and Transgelin/Tagln were characterized as direct targets of Mir34a and Csf1r signaling. Mir34a-inactivation related expression signatures were associated with CMS4/CRISB+D, stage 4 CRCs and poor patient survival. In tumoroids the loss of Mir34a conferred resistance to 5-FU which was mediated by Csf1r. This study provides genetic evidence for a requirement of Mir34a-mediated Csf1r suppression for intestinal stem/secretory cell homeostasis and tumor suppression, and suggests that therapeutic targeting of CSF1R may be effective for the treatment of CRCs with defects in the p53/miR-34a pathway.

MicroRNA-34a, Prostate Cancer Stem Cells, and Therapeutic Development

Prostate cancer (PCa) is a highly heterogeneous disease and typically presents with multiple distinct cancer foci. Heterogeneity in androgen receptor (AR) expression levels in PCa has been observed for decades, from untreated tumors to castration-resistant prostate cancer (CRPC) to disseminated metastases. Current standard-of-care therapies for metastatic CRPC can only extend life by a few months. Cancer stem cells (CSCs) are defined as a subpopulation of cancer cells that exists in almost all treatment-naive tumors. Additionally, non-CSCs may undergo cellular plasticity to be reprogrammed to prostate cancer stem cells (PCSCs) during spontaneous tumor progression or upon therapeutic treatments. Consequently, PCSCs may become the predominant population in treatment-resistant tumors, and the "root cause" for drug resistance. microRNA-34a (miR-34a) is a bona fide tumor-suppressive miRNA, and its expression is dysregulated in PCa. Importantly, miR-34a functions as a potent CSC suppressor by targeting many molecules essential for CSC survival and functions, which makes it a promising anti-PCSC therapeutic. Here, we conducted a comprehensive literature survey of miR-34a in the context of PCa and especially PCSCs. We provided an updated overview on the mechanisms of miR-34a regulation followed by discussing its tumor suppressive functions in PCa. Finally, based on current advances in miR-34a preclinical studies in PCa, we offered potential delivery strategies for miR-34a-based therapeutics for treating advanced PCa.

MicroRNA-202 safeguards meiotic progression by preventing premature SEPARASE-mediated REC8 cleavage

MicroRNAs (miRNAs) are believed to play important roles in mammalian spermatogenesis but the in vivo functions of single miRNAs in this highly complex developmental process remain unclear. Here, we report that miR-202, a member of the let-7 family, plays an important role in spermatogenesis by phenotypic evaluation of miR-202 knockout (KO) mice. Loss of miR-202 results in spermatocyte apoptosis and perturbation of the zygonema-to-pachynema transition. Multiple processes during meiosis prophase I including synapsis and crossover formation are disrupted, and inter-sister chromatid synapses are detected. Moreover, we demonstrate that Separase mRNA is a miR-202 direct target and provides evidence that miR-202 upregulates REC8 by repressing Separase expression. Therefore, we have identified miR-202 as a new regulating noncoding gene that acts on the established SEPARASE-REC8 axis in meiosis.

A rationalized definition of general tumor suppressor microRNAs excludes miR-34a

While several microRNAs (miRNAs) have been proposed to act as tumor suppressors, a consensual definition of tumor suppressing miRNAs is still missing. Similarly to coding genes, we propose that tumor suppressor miRNAs must show evidence of genetic or epigenetic inactivation in cancers, and exhibit an anti-tumorigenic (e.g., anti-proliferative) activity under endogenous expression levels. Here we observe that this definition excludes the most extensively studied tumor suppressor candidate miRNA, miR-34a. In analyzable cancer types, miR-34a does not appear to be down-regulated in primary tumors relatively to normal adjacent tissues. Deletion of miR-34a is occasionally found in human cancers, but it does not seem to be driven by an anti-tumorigenic activity of the miRNA, since it is not observed upon smaller, miR-34a-specific alterations. Its anti-proliferative action was observed upon large, supra-physiological transfection of synthetic miR-34a in cultured cells, and our data indicates that endogenous miR-34a levels do not have such an effect. Our results therefore argue against a general tumor suppressive function for miR-34a, providing an explanation to the lack of efficiency of synthetic miR-34a administration against solid tumors.

miRNA ‐34c suppresses osteosarcoma progression in vivo by targeting Notch and E2F

The expression of microRNAs (miRNAs) is dysregulated in many types of cancers including osteosarcoma (OS) due to genetic and epigenetic alterations. Among these, miR‐34c, an effector of tumor suppressor P53 and an upstream negative regulator of Notch signaling in osteoblast differentiation, is dysregulated in OS. Here, we demonstrated a tumor suppressive role of miR‐34c in OS progression using in vitro assays and in vivo genetic mouse models. We found that miR‐34c inhibits the proliferation and the invasion of metastatic OS cells, which resulted in reduction of the tumor burden and increased overall survival in an orthotopic xenograft model. Moreover, the osteoblast‐specific overexpression of miR‐34c increased survival in the osteoblast specific p53 mutant OS mouse model. We found that miR‐34c regulates the transcription of several genes in Notch signaling (NOTCH1, JAG1, and HEY2) and in p53‐mediated cell cycle and apoptosis (CCNE2, E2F5, E2F2, and HDAC1). More interestingly, we found that the metastatic‐free survival probability was increased among a patient cohort from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) OS, which has lower expression of direct targets of miR‐34c that was identified in our transcriptome analysis, such as E2F5 and NOTCH1. In conclusion, we demonstrate that miR‐34c is a tumor suppressive miRNA in OS progression in vivo. In addition, we highlight the therapeutic potential of targeting miR‐34c in OS. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

SPARCLE, a p53-induced lncRNA, controls apoptosis after genotoxic stress by promoting PARP-1 cleavage

p53, master transcriptional regulator of the genotoxic stress response, controls cell-cycle arrest and apoptosis following DNA damage. Here, we identify a p53-induced lncRNA suicidal PARP-1 cleavage enhancer (SPARCLE) adjacent to miR-34b/c required for p53-mediated apoptosis. SPARCLE is a ∼770-nt, nuclear lncRNA induced 1 day after DNA damage. Despite low expression (<16 copies/cell), SPARCLE deletion increases DNA repair and reduces DNA-damage-induced apoptosis as much as p53 deficiency, while its overexpression restores apoptosis in p53-deficient cells. SPARCLE does not alter gene expression. SPARCLE binds to PARP-1 with nanomolar affinity and causes apoptosis by acting as a caspase-3 cofactor for PARP-1 cleavage, which separates PARP-1's N-terminal (NT) DNA-binding domain from its catalytic domains. NT-PARP-1 inhibits DNA repair. Expressing NT-PARP-1 in SPARCLE-deficient cells increases unrepaired DNA damage and restores apoptosis after DNA damage. Thus, SPARCLE enhances p53-induced apoptosis by promoting PARP-1 cleavage, which interferes with DNA-damage repair.

Essential Roles of Efferent Duct Multicilia in Male Fertility

Cilia are microtubule-based hair-like organelles on the cell surface. Cilia have been implicated in various biological processes ranging from mechanosensation to fluid movement. Ciliary dysfunction leads to a plethora of human diseases, known as ciliopathies. Although non-motile primary cilia are ubiquitous, motile multicilia are found in restricted locations of the body, such as the respiratory tract, the oviduct, the efferent duct, and the brain ventricles. Multicilia beat in a whip-like motion to generate fluid flow over the apical surface of an epithelium. The concerted ciliary motion provides the driving force critical for clearing airway mucus and debris, transporting ova from the ovary to the uterus, maintaining sperm in suspension, and circulating cerebrospinal fluid in the brain. In the male reproductive tract, multiciliated cells (MCCs) were first described in the mid-1800s, but their importance in male fertility remained elusive until recently. MCCs exist in the efferent ducts, which are small, highly convoluted tubules that connect the testis to the epididymis and play an essential role in male fertility. In this review, we will introduce multiciliogenesis, discuss mouse models of male infertility with defective multicilia, and summarize our current knowledge on the biological function of multicilia in the male reproductive tract.

microRNA-based diagnostic and therapeutic applications in cancer medicine

It has been almost two decades since the first link between microRNAs and cancer was established. In the ensuing years, this abundant class of short noncoding regulatory RNAs has been studied in virtually all cancer types. This tremendously large body of research has generated innovative technological advances for detection of microRNAs in tissue and bodily fluids, identified the diagnostic, prognostic, and/or predictive value of individual microRNAs or microRNA signatures as potential biomarkers for patient management, shed light on regulatory mechanisms of RNA-RNA interactions that modulate gene expression, uncovered cell-autonomous and cell-to-cell communication roles of specific microRNAs, and developed a battery of viral and nonviral delivery approaches for therapeutic intervention. Despite these intense and prolific research efforts in preclinical and clinical settings, there are a limited number of microRNA-based applications that have been incorporated into clinical practice. We review recent literature and ongoing clinical trials that highlight most promising approaches and standing challenges to translate these findings into viable microRNA-based clinical tools for cancer medicine. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Regulation of airway immunity by epithelial miRNAs

The airway epithelium is essential to protect the host from inhaled pathogens and particles. It maintains immune homeostasis and mediates tissue repair after injury. Inflammatory diseases of the airways are associated with failure of epithelial functions, including loss of barrier integrity that results in increased tissue permeability and immune activation; excessive mucus secretion and impaired mucociliary clearance that leads to airflow obstruction and microbial overgrowth; and dysregulation of cellular signals that promotes inflammation and alters tissue structure and airway reactivity. MicroRNAs play crucial roles in mounting appropriate cellular responses to environmental stimuli and preventing disease, using a common machinery and mechanism to regulate gene expression in epithelial cells, immune cells of hematopoietic origin, and other cellular components of the airways. Respiratory diseases are accompanied by dramatic changes in epithelial miRNA expression that drive persistent immune dysregulation. In this review, we discuss responses of the epithelium that promote airway immunopathology, with a focus on miRNAs that contribute to the breakdown of essential epithelial functions. We emphasize the emerging role of miRNAs in regulation of epithelial responses in respiratory health and their value as diagnostic and therapeutic targets.

miR‑34a increases inflammation and oxidative stress levels in patients with necrotizing enterocolitis by downregulating SIRT1 expression

The miR‑34a/SIRT1 signaling axis is an important signaling axis in tumors and diseases. Notably, low SIRT1 expression in the intestinal tissues of patients with necrotizing enterocolitis (NEC) has been reported. However, whether miR‑34a/SIRT1 signaling as a target to protect the intestines during the NEC process is unclear and remains to be elucidated. Blood samples were collected from 30 patients with NEC, and an NEC rat model was used. The miR‑34a and SIRT1 gene and protein expression levels were assayed by qPCR and Western blotting method. The inflammatory cytokine levels and oxidative stress levels were detected using the ELISA method. The results demonstrated that birth weight, albumin and glucose concentrations were significantly decreased in the NEC patient group compared with the control group, but the C‑reactive protein (CRP) and procalcitonin (PCT) concentrations were significantly increased. The miR‑34a expression level was notably increased in the NEC group, but the SIRT1 expression level was markedly decreased. Notably, the miR‑34a was significantly correlated with NEC severity and the concentrations of CRP, PCT, IL‑6, TNF‑α, IL‑1β, IL‑8, MCP‑1, VCAM1 and malondialdehyde (MDA), but was significantly negatively correlated with SIRT1 gene expression and the concentration of IL‑10. Intestinal villi damage in NEC rats was decreased with miR‑34a inhibition and SIRT1 activation treatment by decreasing the levels of inflammatory cytokines, including IL‑6, TNF‑α, IL‑1β and IL‑8, and oxidative stress proteins, including MCP‑1, VCAM1, and MDA, as well as increasing the level of the anti‑inflammatory cytokine IL‑10. In addition, the results indicated that miR‑34a inhibition and SIRT1 activation strongly protected the intestine and decreased the damage caused by NEC, not only by decreasing the protein levels of SIRT1, TNF‑α, IL‑1β, IL‑6 and IL‑8, but also by increasing the IL‑10 protein levels. The miR‑34a inhibition and SIRT1 activation may decrease the damage caused by NEC by decreasing proinflammatory cytokines and oxidative stress proteins and by increasing the anti‑inflammatory cytokine pathway. Based on the aforementioned analysis, the miR‑34a and SIRT1 proteins may be potential novel therapeutic targets in NEC.

Up-regulation of miR-34b/c by JNK and FOXO3 protects from liver fibrosis

α1-Antitrypsin (AAT) deficiency is a common genetic disease presenting with lung and liver diseases. AAT deficiency results from pathogenic variants in the SERPINA1 gene encoding AAT and the common mutant Z allele of SERPINA1 encodes for Z α1-antitrypsin (ATZ), a protein forming hepatotoxic polymers retained in the endoplasmic reticulum of hepatocytes. PiZ mice express the human ATZ and are a valuable model to investigate the human liver disease of AAT deficiency. In this study, we investigated differential expression of microRNAs (miRNAs) between PiZ and control mice and found that miR-34b/c was up-regulated and its levels correlated with intrahepatic ATZ. Furthermore, in PiZ mouse livers, we found that Forkhead Box O3 (FOXO3) driving microRNA-34b/c (miR-34b/c) expression was activated and miR-34b/c expression was dependent upon c-Jun N-terminal kinase (JNK) phosphorylation on Ser⁵⁷⁴ Deletion of miR-34b/c in PiZ mice resulted in early development of liver fibrosis and increased signaling of platelet-derived growth factor (PDGF), a target of miR-34b/c. Activation of FOXO3 and increased miR-34c were confirmed in livers of humans with AAT deficiency. In addition, JNK-activated FOXO3 and miR-34b/c up-regulation were detected in several mouse models of liver fibrosis. This study reveals a pathway involved in liver fibrosis and potentially implicated in both genetic and acquired causes of hepatic fibrosis.

Next-generation sequencing analysis reveals segmental patterns of microRNA expression in yak epididymis

MicroRNAs (miRNAs) have emerged as potent regulators of gene expression and are widely expressed in biological systems. In reproduction, they have been shown to have a significant role in the acquisition and maintenance of male fertility, whereby deletion of Dicer in mouse germ cells leads to infertility. Evidence indicates that this role of miRNAs extends from the testis into the epididymis, controlling gene expression and contributing to regional variations in gene expression. In this study, RNA sequencing technology was used to investigate miRNA expression patterns in the yak epididymis. Region-specific miRNA expression was found in the yak epididymis. In all, 683 differentially expressed known miRNAs were obtained; 190, 186 and 307 differentially expressed miRNAs were identified for caput versus corpus, corpus versus cauda and caput versus cauda region pairs respectively. Kyoto Encyclopedia of Genes and Genomes results showed endocytosis as the most enriched pathway across region pairs, followed by protein processing in the endoplasmic reticulum, phagosome, spliceosome and biosynthesis of amino acids in region pair-specific hierarchical order. Gene ontology results showed varied enrichment in terms including cell, biogenesis, localisation, binding and locomotion across region pairs. In addition, significantly higher miR-34c expression was seen in the yak caput epididymidis relative to the corpus and cauda epididymidis.

Fine-tuning multiciliated cell differentiation at the post-transcriptional level: contribution of miR-34/449 family members

Cell differentiation is a process that must be precisely regulated for the maintenance of tissue homeostasis. Differentiation towards a multiciliated cell fate is characterized by well-defined stages, where a transcriptional cascade is activated leading to the formation of multiple centrioles and cilia. Centrioles migrate and dock to the apical cell surface and, acting as basal bodies, give rise to multiple motile cilia. The concerted movement of cilia ensures directional fluid flow across epithelia and defects either in their number or structure can lead to disease phenotypes. Micro-RNAs (miRNAs; miRs) are small, non-coding RNA molecules that play an important role in post-transcriptional regulation of gene expression. miR-34b/c and miR-449a/b/c specifically function throughout the differentiation of multiciliated cells, fine-tuning the expression of many different centriole- and cilia-related genes. They strictly regulate the expression levels of genes that are required both for commitment towards the multiciliated cell fate (e.g. Notch) and for the establishment and maintenance of this fate by regulating the expression of transcription factors and structural components of the pathway. Herein we review miR-34 and miR-449 spatiotemporal regulation along with their roles during the different stages of multiciliogenesis.

Control of multiciliogenesis by miR-34/449 in the male reproductive tract through enforcing cell cycle exit

Multiciliated cells (MCCs) are terminally differentiated postmitotic cells that possess hundreds of motile cilia on their apical surface. Defects in cilia formation are associated with ciliopathies that affect many organs. In this study, we tested the role and mechanism of the miR-34/449 family in the regulation of multiciliogenesis in EDs using an miR-34b/c−/−; miR-449−/− double knockout (dKO) mouse model. MiR-34b/c and miR-449 depletion led to a reduced number of MCCs and abnormal cilia structure in the EDs starting from postnatal day (P)14. However, abnormal MCC differentiation in the dKO EDs could be observed as early as P7. RNA-seq analyses revealed that the aberrant development of MCCs in the EDs of dKO mice was associated with the upregulation of genes involved in cell cycle control. Using a cyclin-dependent kinase inhibitor to force cell cycle exit promoted MCC differentiation, and partially rescued the defective multiciliogenesis in the EDs of dKO mice. Taken together, our results suggest that miR-34b/c and miR-449 play an essential role in multiciliogenesis in EDs by regulating cell cycle exit.

Summary: Mutagenic, expression and histological analyses reveal an essential role for miR-34b/c and miR-449 in multiciliogenesis in efferent ductules of the male reproductive tract by regulating cell cycle exit.

The roles of microRNAs in mouse development

Hundreds of microRNAs (miRNAs) are expressed in distinct spatial and temporal patterns during embryonic and postnatal mouse development. The loss of all miRNAs through the deletion of critical miRNA biogenesis factors results in early lethality. The function of each miRNA stems from their cumulative negative regulation of multiple mRNA targets expressed in a particular cell type. During development, miRNAs often coordinate the timing and direction of cell fate transitions. In adults, miRNAs frequently contribute to organismal fitness through homeostatic roles in physiology. Here, we review how the recent dissection of miRNA-knockout phenotypes in mice as well as advances related to their targets, dosage, and interactions have collectively informed our understanding of the roles of miRNAs in mammalian development and adaptive responses.

MicroRNA-34a regulates 5-HT2C expression in dorsal raphe and contributes to the anti-depressant-like effect of fluoxetine

Selective serotonin reuptake inhibitors (SSRIs) are designed to improve mood by raising extracellular serotonin levels through the blockade of the serotonin transporter. However, they exhibit a slow onset of action, suggesting the involvement of adaptive regulatory mechanisms. We hypothesized that the microRNA-34 family facilitates the therapeutic activity of SSRIs. We show that genetic deletion of these microRNAs in mice impairs the response to chronic, but not acute, fluoxetine treatment, with a specific effect on behavioral constructs that are related to depression, rather than anxiety. Moreover, using a pharmacological strategy, we found that an increased expression of the serotonin 2C (5-HT2C) receptor in the dorsal raphe region of the brain contributes to this phenotype. The onset of the therapeutic efficacy of SSRIs is paralleled by the desensitization of the 5-HT2C receptor in the dorsal raphe, and 5-HT2C is a putative target of microRNA-34. In this study, acute and chronic fluoxetine treatment differentially alters the expression of 5-HT2C and microRNA-34a in the dorsal raphe. Moreover, by in vitro luciferase assay, we demonstrated the repressive regulatory activity of microRNA-34a against 5-HT2C mRNA. Specific blockade of this interaction through local infusion of a target site blocker was sufficient to prevent the behavioral effects of chronic fluoxetine. Our results demonstrate a new miR-34a-mediated regulatory mechanism of 5-HT2C expression in the dorsal raphe and implicate it in eliciting the behavioral responses to chronic fluoxetine treatment.

miR34a: a novel small molecule regulator with a big role in bronchopulmonary dysplasia

Preterm infants with bronchopulmonary dysplasia (BPD), characterized by pulmonary inflammation leading to impaired alveolarization and vascular dysregulation, have an increased risk of abnormal lung function in infancy, childhood, and adulthood. These include a heightened risk of pulmonary hypertension, and respiratory illnesses. MicroRNAs (miRNAs) are known to disrupt normal lung development and function by interrupting alveolarization and vascularization resulting in the development of BPD. Among the various miRs involved in BPD, miR34a has been shown to have a significant role in BPD pathogenesis. Targeting miR34a or its downstream targets may be a promising therapeutic intervention for BPD. In this review, we summarize the data on cellular arrest, proliferation, differentiation, epithelial-mesenchymal transition, mitochondrial dysfunction, and apoptosis impacted by miR34a in the development of BPD pulmonary phenotypes while predicting the future perspective of miR34a in BPD.

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.

Long non-coding RNA Mir22hg-derived miR-22-3p promotes skeletal muscle differentiation and regeneration by inhibiting HDAC4

Emerging studies have indicated that long non-coding RNAs (lncRNAs) play important roles in skeletal muscle growth and development. Nevertheless, it remains challenging to understand the function and regulatory mechanisms of these lncRNAs in muscle biology and associated diseases. Here, we identify a novel lncRNA, Mir22hg, that is significantly upregulated during myoblast differentiation and is highly expressed in skeletal muscle. We validated that Mir22hg promotes myoblast differentiation in vitro. Mechanistically, Mir22hg gives rise to mature microRNA (miR)-22-3p, which inhibits its target gene, histone deacetylase 4 (HDAC4), thereby increasing the downstream myocyte enhancer factor 2C (MEF2C) and ultimately promoting myoblast differentiation. Furthermore, in vivo, we documented that Mir22hg knockdown delays repair and regeneration following skeletal muscle injury and further causes a significant decrease in weight following repair of an injured tibialis anterior muscle. Additionally, Mir22hg gives rise to miR-22-3p to restrict HDAC4 expression, thereby promoting the differentiation and regeneration of skeletal muscle. Given the conservation of Mir22hg between mice and humans, Mir22hg might constitute a promising new therapeutic target for skeletal muscle injury, skeletal muscle atrophy, as well as other skeletal muscle diseases.

Genes and pathways involved in senescence bypass identified by functional genetic screens

Cellular senescence is a state of stable and irreversible cell cycle arrest with active metabolism, that normal cells undergo after a finite number of divisions (Hayflick limit). Senescence can be triggered by intrinsic and/or extrinsic stimuli including telomere shortening at the end of a cell's lifespan (telomere-initiated senescence) and in response to oxidative, genotoxic or oncogenic stresses (stress-induced premature senescence). Several effector mechanisms have been proposed to explain senescence programmes in diploid cells, including the induction of DNA damage responses, a senescence-associated secretory phenotype and epigenetic changes. Senescent cells display senescence-associated-β-galactosidase activity and undergo chromatin remodeling resulting in heterochromatinisation. Senescence is established by the pRb and p53 tumour suppressor networks. Senescence has been detected in in vitro cellular settings and in premalignant, but not malignant lesions in mice and humans expressing mutant oncogenes. Despite oncogene-induced senescence, which is believed to be a cancer initiating barrier and other tumour suppressive mechanisms, benign cancers may still develop into malignancies by bypassing senescence. Here, we summarise the functional genetic screens that have identified genes, uncovered pathways and characterised mechanisms involved in senescence evasion. These include cell cycle regulators and tumour suppressor pathways, DNA damage response pathways, epigenetic regulators, SASP components and noncoding RNAs.

MicroRNA-34a: the bad guy in age-related vascular diseases

The age-related vasculature alteration is the prominent risk factor for vascular diseases (VD), namely, atherosclerosis, abdominal aortic aneurysm, vascular calcification (VC) and pulmonary arterial hypertension (PAH). The chronic sterile low-grade inflammation state, alias inflammaging, characterizes elderly people and participates in VD development. MicroRNA34-a (miR-34a) is emerging as an important mediator of inflammaging and VD. miR-34a increases with aging in vessels and induces senescence and the acquisition of the senescence-associated secretory phenotype (SASP) in vascular smooth muscle (VSMCs) and endothelial (ECs) cells. Similarly, other VD risk factors, including dyslipidemia, hyperglycemia and hypertension, modify miR-34a expression to promote vascular senescence and inflammation. miR-34a upregulation causes endothelial dysfunction by affecting ECs nitric oxide bioavailability, adhesion molecules expression and inflammatory cells recruitment. miR-34a-induced senescence facilitates VSMCs osteoblastic switch and VC development in hyperphosphatemia conditions. Conversely, atherogenic and hypoxic stimuli downregulate miR-34a levels and promote VSMCs proliferation and migration during atherosclerosis and PAH. MiR34a genetic ablation or miR-34a inhibition by anti-miR-34a molecules in different experimental models of VD reduce vascular inflammation, senescence and apoptosis through sirtuin 1 Notch1, and B-cell lymphoma 2 modulation. Notably, pleiotropic drugs, like statins, liraglutide and metformin, affect miR-34a expression. Finally, human studies report that miR-34a levels associate to atherosclerosis and diabetes and correlate with inflammatory factors during aging. Herein, we comprehensively review the current knowledge about miR-34a-dependent molecular and cellular mechanisms activated by VD risk factors and highlight the diagnostic and therapeutic potential of modulating its expression in order to reduce inflammaging and VD burn and extend healthy lifespan.

miRNA-Based Therapies in B Cell Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma (NHL) is a diverse class of hematological cancers, many of which arise from germinal center (GC)-experienced B cells. Thus GCs, the sites of antibody affinity maturation triggered during immune responses, also provide an environment that facilitates B cell oncogenic transformation. miRNAs provide attractive and mechanistically different strategies to treat these malignancies based on their potential for simultaneous modulation of multiple targets. Here, we discuss the scientific rationale for miRNA-based therapeutics in B cell neoplasias and review recent advances that may help establish a basis for novel candidate miRNA-based therapies for B cell-NHL (B-NHL).

The Role of Non-coding RNAs in Oncology

For decades, research into cancer biology focused on the involvement of protein-coding genes. Only recently was it discovered that an entire class of molecules, termed non-coding RNA (ncRNA), plays key regulatory roles in shaping cellular activity. An explosion of studies into ncRNA biology has since shown that they represent a diverse and prevalent group of RNAs, including both oncogenic molecules and those that work in a tumor suppressive manner. As a result, hundreds of cancer-focused clinical trials involving ncRNAs as novel biomarkers or therapies have begun and these are likely just the beginning.

Targeting miR-34a/Pdgfra interactions partially corrects alveologenesis in experimental bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth characterized by arrested lung alveolarization, which generates lungs that are incompetent for effective gas exchange. We report here deregulated expression of miR‐34a in a hyperoxia‐based mouse model of BPD, where miR‐34a expression was markedly increased in platelet‐derived growth factor receptor (PDGFR)α‐expressing myofibroblasts, a cell type critical for proper lung alveolarization. Global deletion of miR‐34a; and inducible, conditional deletion of miR‐34a in PDGFRα⁺ cells afforded partial protection to the developing lung against hyperoxia‐induced perturbations to lung architecture. Pdgfra mRNA was identified as the relevant miR‐34a target, and using a target site blocker in vivo, the miR‐34a/Pdgfra interaction was validated as a causal actor in arrested lung development. An antimiR directed against miR‐34a partially restored PDGFRα⁺ myofibroblast abundance and improved lung alveolarization in newborn mice in an experimental BPD model. We present here the first identification of a pathology‐relevant microRNA/mRNA target interaction in aberrant lung alveolarization and highlight the translational potential of targeting the miR‐34a/Pdgfra interaction to manage arrested lung development associated with preterm birth.

miR-99 regulates normal and malignant hematopoietic stem cell self-renewal

The mechanisms that regulate self-renewal in hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs) are poorly understood. Herein, Khalaj et al. identify microRNA-99 (miR-99) as a novel noncoding RNA critical for the maintenance of HSCs and LSCs and demonstrate that miR-99 mediates its role by suppressing multiple target genes, including HOXA1.

The microRNA-99 (miR-99) family comprises a group of broadly conserved microRNAs that are highly expressed in hematopoietic stem cells (HSCs) and acute myeloid leukemia stem cells (LSCs) compared with their differentiated progeny. Herein, we show that miR-99 regulates self-renewal in both HSCs and LSCs. miR-99 maintains HSC long-term reconstitution activity by inhibiting differentiation and cell cycle entry. Moreover, miR-99 inhibition induced LSC differentiation and depletion in an MLL-AF9–driven mouse model of AML, leading to reduction in leukemia-initiating activity and improved survival in secondary transplants. Confirming miR-99’s role in established AML, miR-99 inhibition induced primary AML patient blasts to undergo differentiation. A forward genetic shRNA library screen revealed Hoxa1 as a critical mediator of miR-99 function in HSC maintenance, and this observation was independently confirmed in both HSCs and LSCs. Together, these studies demonstrate the importance of noncoding RNAs in the regulation of HSC and LSC function and identify miR-99 as a critical regulator of stem cell self-renewal.

The miR-34 family and its clinical significance in ovarian cancer

The tumor suppressor miR-34 family is transcriptionally induced by p53. Clinical significance of the various miR-34 family members has not been studied in ovarian cancer. In 228 ovarian cancers and in 19 non-neoplastic fallopian tube samples we analysed miR-34 a/b/c expression in relation to clinicopathological characteristics and clinical outcome. We found significantly lower levels of miR-34 a/b/c in ovarian cancers as compared to control-tissues (P=0.002, P<0.001, P<0.001, respectively). Expression of miR-34 b/c revealed an inverse correlation with BRCA1/2 mRNA-expression (BRCA1: miR34 b/c P=0.002 each; BRCA2: miR-34 b/c P<0.001 each), the same was true for miR-34a and BRCA2 mRNA-expression (P<0.001). The miR-34 family expression was found to be significantly lower in type 2 in comparison to type 1 cancers (P<0.001) and in TP53-mutated compared with TP53-wild-type ovarian cancers (P<0.001, P=0.002, P=0.004, respectively). When low grade serous ovarian cancers were compared with high grade serous cancers the respective miR-34 a/b/c expression was 2.6-, 40.8- and 32.3-fold higher. The expression of each of the miR-34 family members was revealed to be of independent prognostic relevance regarding progression free survival (PFS); miR-34a: HR 0.6, P=0.033; miR-34b: HR 0.2, P=0.001 and miR-34c: HR 0.3, P=0.002, respectively). For overall survival (OS) independency of the prognostic value was confined to miR-34b (HR 0.4, P=0.016) and miR-34c (HR 0.6, P=0.049). The independency of the prognostic value of our identified thresholds was confirmed for PFS for miR-34c in a publicly available dataset (NCBI Gene Expression Omnibus GSE73582). Our findings suggest that downregulation of miR-34 family is a crucial part in ovarian cancer development. Low miR-34 levels are linked to a worse overall survival and progression free survival and may indicate a more aggressive disease.

Microarray expression and functional analysis of circular RNAs in the glomeruli of NZB/W F1 mice with lupus nephritis

The present study applied a circular RNA (circRNA) microarray to examine the circRNA expression profiles in the glomeruli of NZB/W F1 mice with lupus nephritis (LN) during the pathogenesis of the disease. Glomeruli from two groups of female NZB/W F1 mice of the same age with either severe or mild LN were isolated by perfusion with dynabeads. A microarray analysis was then performed to evaluate the differentially expressed circRNAs of the glomeruli in the two groups, which were then confirmed by reverse transcription-quantitative PCR (RT-qPCR) assays. In addition, using a biomathematical strategy, the differentially-expressed circRNAs were identified in severe LN when compared with mild LN, and the commonly expressed circRNA species among these profiles were optimized via competing endogenous RNA (ceRNA) analysis. The predicted microRNAs (miRNAs/miRs) as downstream targets of circRNAs and upstream regulators of mRNAs were verified by RT-qPCR and the final circRNA-miRNA-mRNA network was constructed to identify the circRNA that was a pathogenic link in LN. The present study obtained 116 differentially expressed circRNAs, including 41 up- and 75 downregulated circRNAs, in severe LN when compared with mild LN, and 12 circRNAs were confirmed by RT-qPCR. The most significant difference was in the expression of mmu_circRNA_34428 (P<0.001) when comparing severe and mild LN glomeruli. A network of mmu_circRNA_34428-targeted miRNA-gene interactions was subsequently constructed, including miR-338-3p, miR-670-3p, miR-3066-5p, miR-210-5p and their corresponding mRNA targets. To the best of our knowledge, the present study elucidated, for the first time, circRNA profiling and the circRNA-miRNA interactions in the development of LN in female NZB/W F1 mice. The results revealed that mmu_circRNA_34428 could serve an important role in LN progression; however, the present study did not elucidate the functions of this circRNA or others in LN progression.

microRNA-14 as an efficient suppressor to switch off ecdysone production after ecdysis in insects

The precise increase and decrease of hormone ecdysone are critical for accurate development in insects. Most previous works focus on transcriptional activation of ecdysone production; however, little is known about the mechanism of switching off ecdysone biosynthesis after ecdysis. Here, we showed that the precursor microRNA-14 (pre-miR-14) encodes two mature miRNAs in silkworm; both of these two mature miRNAs regulate various genes in the ecdysone-signalling pathway. Bmo-miR-14-5p targets on nine genes whereas Bmo-miR-14-3p targets on two genes in the same pathway. These two mature miRNAs increased immediately after the ecdysis, efficiently suppressing the 20-hydroxyecdysone (20E) biosynthesis, the upstream regulation, and the downstream response genes. Knocking down either of two mature miRNAs or both of them delays moult development, impairing development synchrony in antagomir-treated groups. In addition, overexpressing Bmo-miR-14-5p but not Bmo-miR-14-3p significantly affected the 20E titer and increased the moulting time variation, suggesting that Bmo-miR-14-5p, though it is less abundant, has more potent effects in development regulation than Bmo-miR-14-3p. In summary, we present evidence that a pre-miRNA encodes two mature miRNAs targeting on the same pathway, which significantly improves miRNA regulation efficiencies to programmatically switch off ecdysone biosynthesis.

Telomere Dysfunction Induces Sirtuin Repression that Drives Telomere-Dependent Disease

Telomere shortening is associated with stem cell decline, fibrotic disorders, and premature aging through mechanisms that are incompletely understood. Here, we show that telomere shortening in livers of telomerase knockout mice leads to a p53-dependent repression of all seven sirtuins. P53 regulates non-mitochondrial sirtuins (Sirt1, 2, 6, and 7) post-transcriptionally through microRNAs (miR-34a, 26a, and 145), while the mitochondrial sirtuins (Sirt3, 4, and 5) are regulated in a peroxisome proliferator-activated receptor gamma co-activator 1 alpha-/beta-dependent manner at the transcriptional level. Administration of the NAD(+) precursor nicotinamide mononucleotide maintains telomere length, dampens the DNA damage response and p53, improves mitochondrial function, and, functionally, rescues liver fibrosis in a partially Sirt1-dependent manner. These studies establish sirtuins as downstream targets of dysfunctional telomeres and suggest that increasing Sirt1 activity alone or in combination with other sirtuins stabilizes telomeres and mitigates telomere-dependent disorders.

Selected serum microRNA, abdominal aortic calcification and risk of osteoporotic fracture

CONTEXT

MicroRNA (miRNA) regulate post-transcriptionally the expression of osteogenesis and angiogenesis associated genes and emerge as potential non-invasive biomarkers in vascular and bone diseases. Severe abdominal aortic calcification (AAC) is associated with higher risk of cardiovascular event and of fragility fracture.

OBJECTIVE

To identify miRNA linked to the aggravation of AAC and to incident osteoporotic fracture.

DESIGN

Postmenopausal women (>50 years) with available serum at inclusion and data for each outcome (Kauppila score and incident fracture) were selected from the OFELY prospective cohort. We conducted a case-control study in 434 age-matched women, 50% with incident osteoporotic fracture over 20 years of follow-up and a second study in 183 women to explore AAC over 17 years.

METHODS

Serum expression of three miRNA involved in vascular calcification and bone turnover regulation (miRs-26a-5p,-34a-5p, and -223-5p) was quantified at baseline by TaqMan Advanced miRNA technology and expressed by relative quantification. Outcomes were the association of miRNA levels with (1) incident osteoporotic fractures during 20 years, (2) AAC aggravation during 17 years.

RESULTS

MiRNA level was not associated with incident fractures (miR-26a-5p: 1.06 vs 0.99, p = 0.07; miR-34a-5p: 1.15 vs 1.26, p = 0.35; miR-223a-5p: 1.01 vs 1.05, p = 0.32). 93 women had an increase in Kauppila score over 17 years while 90 did not. None of the miRNAs was associated with an aggravation in AAC (miR-26a-5p: 1.09 vs 1.10, p = 0.95; miR-34a-5p: 0.78 vs 0.73, p = 0.90; miR-223-5p: 0.97 vs 0.78, p = 0.11).

CONCLUSIONS

Circulating miR-26a-5p, -34a-5p and -223-5p are not significantly associated with incident fracture and AAC aggravation.

Delivery of biologically active miR-34a in normal and cancer mammary epithelial cells by synthetic nanoparticles

Functional RNAs, such as microRNAs, are emerging as innovative tools in the treatment of aggressive and incurable cancers. In this study, we explore the potential of silica dioxide nanoparticles (SiO₂NPs) in the delivery of biologically active miRNAs. Focusing on the tumor-suppressor miR-34a, we evaluated miRNAs delivery by SiO₂NPs into the mammary gland, using in vitro as well as in vivo model systems. We showed that silica nanoparticles can efficiently deliver miR-34a into normal and cancer epithelial cells grown in culture without major signs of toxicity. Delivered miRNA retained the ability to silence artificial as well endogenous targets and can reduce the growth of mammospheres in 3D culture. Finally, miR-34a delivery through intra-tumor administration of SiO₂NPs leads to a reduced mammary tumor growth. In conclusion, our studies suggest that silica nanoparticles can mediate the delivery of miR-34a directly into mammary tumors while preserving its molecular and biological activity.

MicroRNAs and metastasis: small RNAs play big roles

MicroRNAs (miRNAs) are small non-coding RNAs regulating post-transcriptional gene expression. They play important roles in many biological processes under physiological or pathological conditions, including development, metabolism, tumorigenesis, metastasis, and immune response. Over the past 15 years, significant insights have been gained into the roles of miRNAs in cancer. Depending on the cancer type, miRNAs can act as oncogenes, tumor suppressors, or metastasis regulators. In this review, we focus on the role of miRNAs as components of molecular networks regulating metastasis. These miRNAs, termed metastamiRs, promote or inhibit metastasis through various mechanisms, including regulation of migration, invasion, colonization, cancer stem cell properties, epithelial-mesenchymal transition, and microenvironment. Some of these metastamiRs represent attractive therapeutic targets for cancer treatment.

MiR-34a and miR-34b/c have distinct effects on the suppression of lung adenocarcinomas

Three miR-34 family members (miR-34a, miR-34b, and miR-34c) are clustered on two different chromosomal loci, Mir34a and Mir34b/c. These miRNAs have identical seed sequences, which are predicted to target the same set of genes. However, miR-34a and miR-34c have different sets of negatively correlated genes in lung adenocarcinoma data from The Cancer Genome Atlas. Therefore, we hypothesized that the individual miR-34 family members, which are tumor suppressive miRNAs, would have varying effects on lung tumorigenesis. To show this, we overexpressed each miR-34 cluster in murine lung cancer cells. MiR-34b/c enhanced cancer cell attachment and suppressed cell growth and invasion compared with miR-34a. In a syngeneic mouse model, both miR-34a and miR-34b/c blocked lung metastasis. However, miR-34b/c suppressed tumor growth more than miR-34a. MiR-34b/c also decreased the expression of mesenchymal markers (Cdh2 and Fn1) and increased the expression of epithelial markers (Cldn3, Dsp, and miR-200) to a greater degree than miR-34a. These results imply that miR-34b and miR-34c inhibit epithelial-to-mesenchymal transition. Furthermore, knockout of all three miR-34 members promoted mutant Kras-driven lung tumor progression in mice. Similarly, lung adenocarcinoma patients with higher miR-34a/b/c levels had better survival rates than did those with lower levels. In summary, we suggest that miR-34b and miR-34c are more effective tumor suppressors than miR-34a.

Exploring the effects of three similar small RNA molecules called micro-RNAs (miRNAs) that can restrict the activity of specific genes reveals how they might be used in cancer treatment. RNA is best known as messenger RNA, which carries a copy of a gene’s information into the cell cytoplasm to direct protein manufacture. Many small RNAs play less well-known but crucial roles by binding to messenger RNA molecules to regulate their activity. Researchers in South Korea and USA, led by Young-Ho Ahn at Ewha Womans University in Seoul, investigated how these miRNAs can suppress lung cancer in mice. Their results reveal details of how the miRNAs inhibit the expression of specific tumor-supporting genes. They suggest that three of the RNAs administered together might treat cancer more effectively than using only one as in previous trials.

miR-34a is a microRNA safeguard for Citrobacter-induced inflammatory colon oncogenesis

Inflammation often induces regeneration to repair the tissue damage. However, chronic inflammation can transform temporary hyperplasia into a fertile ground for tumorigenesis. Here, we demonstrate that the microRNA miR-34a acts as a central safeguard to protect the inflammatory stem cell niche and reparative regeneration. Although playing little role in regular homeostasis, miR-34a deficiency leads to colon tumorigenesis after Citrobacter rodentium infection. miR-34a targets both immune and epithelial cells to restrain inflammation-induced stem cell proliferation. miR-34a targets Interleukin six receptor (IL-6R) and Interleukin 23 receptor (IL-23R) to suppress T helper 17 (Th17) cell differentiation and expansion, targets chemokine CCL22 to hinder Th17 cell recruitment to the colon epithelium, and targets an orphan receptor Interleukin 17 receptor D (IL-17RD) to inhibit IL-17-induced stem cell proliferation. Our study highlights the importance of microRNAs in protecting the stem cell niche during inflammation despite their lack of function in regular tissue homeostasis.

6mer seed toxicity in tumor suppressive microRNAs

Many small-interfering (si)RNAs are toxic to cancer cells through a 6mer seed sequence (positions 2–7 of the guide strand). Here we performed an siRNA screen with all 4096 6mer seeds revealing a preference for guanine in positions 1 and 2 and a high overall G or C content in the seed of the most toxic siRNAs for four tested human and mouse cell lines. Toxicity of these siRNAs stems from targeting survival genes with C-rich 3′UTRs. The master tumor suppressor miRNA miR-34a-5p is toxic through such a G-rich 6mer seed and is upregulated in cells subjected to genotoxic stress. An analysis of all mature miRNAs suggests that during evolution most miRNAs evolved to avoid guanine at the 5′ end of the 6mer seed sequence of the guide strand. In contrast, for certain tumor-suppressive miRNAs the guide strand contains a G-rich toxic 6mer seed, presumably to eliminate cancer cells.

Small interfering (siRNAs) can be toxic to cancer cells. Here the authors investigate the toxicity of microRNA in cancer cells by performing a siRNA screen that tests the miRNA activities of an extensive list of miRNAs with different 6mer seed sequences.