MicroRNA-137 represses Klf4 and Tbx3 during differentiation of mouse embryonic stem cells

MicroRNA-mediated Krüppel-like factor 4 upregulation induces alternatively activated macrophage-associated marker and chemokine transcription in 4,4'-methylene diphenyl diisocyanate exposed macrophages

1. Occupational exposure to 4,4'-methylene diphenyl diisocyanate (MDI) is associated with occupational asthma (OA) development. Alveolar macrophage-induced recruitment of immune cells to the lung microenvironment plays an important role during asthma pathogenesis. Previous studies identified that MDI/MDI-glutathione (GSH)-exposure downregulates endogenous hsa-miR-206-3p/hsa-miR-381-3p. Our prior report shows that alternatively activated (M2) macrophage-associated markers/chemokines are induced by MDI/MDI-GSH-mediated Krüppel-Like Factor 4 (KLF4) upregulation in macrophages and stimulates immune cell chemotaxis. However, the underlying molecular mechanism(s) by which MDI/MDI-GSH upregulates KLF4 remain unclear.

2. Following MDI-GSH exposure, microRNA(miR)-inhibitors/mimics or plasmid transfection, endogenous hsa-miR-206-3p/hsa-miR-381-3p, KLF4, or M2 macrophage-associated markers (CD206, TGM2), and chemokines (CCL17, CCL22, CCL24) were measured by either RT-qPCR, western blot, or luciferase assay.

3. MDI-GSH exposure downregulates hsa-miR-206-3p/hsa-miR-381-3p by 1.46- to 9.75-fold whereas upregulates KLF4 by 1.68- to 1.99-fold, respectively. In silico analysis predicts binding between hsa-miR-206-3p/hsa-miR-381-3p and KLF4. Gain- and loss-of-function, luciferase reporter assays and RNA-induced silencing complex-immunoprecipitation (RISC-IP) studies confirm the posttranscriptional regulatory roles of hsa-miR-206-3p/hsa-miR-381-3p and KLF4 in macrophages. Furthermore, hsa-miR-206-3p/hsa-miR-381-3p regulate the expression of M2 macrophage-associated markers and chemokines via KLF4.

4. In conclusion, hsa-miR-206-3p/hsa-miR-381-3p play a major role in regulation of MDI/MDI-GSH-induced M2 macrophage-associated markers and chemokines by targeting the KLF4 transcript, and KLF4-mediated regulation in macrophages.

miR-137 regulates PTP61F, affecting insulin signaling, metabolic homeostasis, and starvation resistance in Drosophila

miR-137 is a highly conserved brain-enriched microRNA (miRNA) that has been associated with neuronal function and proliferation. Here, we show that Drosophila miR-137 null mutants display increased body weight with enhanced triglyceride content and decreased locomotor activity. In addition, when challenged by nutrient deprivation, miR-137 mutants exhibit reduced motivation to feed and prolonged survival. We show through genetic epistasis and rescue experiments that this starvation resistance is due to a disruption in insulin signaling. Our studies further show that miR-137 null mutants exhibit a drastic reduction in levels of the phosphorylated/activated insulin receptor, InR (InR-P). We investigated if this is due to the predicted miR-137 target, Protein Tyrosine Phosphatase 61F (PTP61F), ortholog of mammalian TC-PTP/PTP1B, which are known to dephosphorylate InR-P. Indeed, levels of an endogenously tagged GFP-PTP61F are significantly elevated in miR-137 null mutants, and we show that overexpression of PTP61F alone is sufficient to mimic many of the metabolic phenotypes of miR-137 mutants. Finally, we knocked-down elevated levels of PTP61F in the miR-137 null mutant background and show that this rescues levels of InR-P, restores normal body weight and triglyceride content, starvation sensitivity, as well as attenuates locomotor and starvation-induced feeding defects. Our study supports a model in which miR-137 is critical for dampening levels of PTP61F, thereby maintaining normal insulin signaling and energy homeostasis.

MiR-137-mediated negative relationship between LGR4 and RANKL modulated osteogenic differentiation of human adipose-derived mesenchymal stem cells

MicroRNA-137 (miR-137) has recently emerged as an osteogenic regulator in several cell lines. This study aimed to identify the function of miR-137 on the crosstalk between leucine rich repeat containing G protein-coupled receptor 4 (LGR4) and receptor activator of nuclear factor-κB ligand (RANKL), thus unveiling the critical role of LGR4-RANKL interplay in the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hASCs). By examining the osteogenic capacity and possible downstream genes expression with miR-137 overexpression/knockdown, we found that miR-137 downregulated LGR4 while upregulating RANKL. According to the results of dual-luciferase reporter assay, LGR4 was validated as a direct target of miR-137. Surprisingly, a negative relationship between LGR4 and RANKL was confirmed by the knockdown of these two genes. Furthermore, RANKL inhibitor could alleviate or reverse the inhibitory effects on osteogenesis generated by LGR4 knockdown. Collectively, this study indicated that miR-137-induced a negative crosstalk between LGR4 and RANKL that could contribute to the osteogenic regulation of hASCs and provide more systematic and in-depth understanding of epigenetic modulation by miR-137.

Association of T-box gene polymorphisms with the risk of Wolff-Parkinson-White syndrome in a Han Chinese population

Abnormal development of the atrioventricular ring can lead to the formation of a bypass pathway and the occurrence of Wolff-Parkinson-White (WPW) syndrome. The genetic mechanism underlying the sporadic form of WPW syndrome remains unclear. Existing evidence suggests that both T-box transcription factor 3 (TBX3) and T-box transcription factor 2 (TBX2) genes participate in regulating annulus fibrosus formation and atrioventricular canal development. Thus, we aimed to examine whether single-nucleotide polymorphisms (SNPs) in the TBX3 and TBX2 genes confer susceptibility to WPW syndrome in a Han Chinese Population. We applied a SNaPshot SNP assay to analyze 5 selected tagSNPs of TBX3 and TBX2 in 230 patients with sporadic WPW syndrome and 231 sex- and age-matched controls. Haplotype analysis was performed using Haploview software. Allele C of TBX3 rs1061657 was associated with a higher risk of WPW syndrome (odds ratio [OR] = 1.41, 95% confidence interval [CI]: 1.08-1.83, P = .011) and left-sided accessory pathways (OR = 1.40, 95% CI: 1.07-1.84, P = .016). However, allele C of TBX3 rs8853 was likely to reduce these risks (OR = 0.71, 95% CI: 0.54-0.92, P = .011; OR = 0.70, 95% CI: 0.53-0.92, P = .011, respectively). The data revealed no association between TBX3 rs77412687, TBX3 rs2242442, or TBX2 rs75743672 and WPW syndrome. TBX3 rs1061657 and rs8853 are significantly associated with sporadic WPW syndrome among a Han Chinese population. To verify our results, larger sample sizes are required in future studies.

Post-Transcriptional Regulation of Molecular Determinants during Cardiogenesis

Cardiovascular development is initiated soon after gastrulation as bilateral precardiac mesoderm is progressively symmetrically determined at both sides of the developing embryo. The precardiac mesoderm subsequently fused at the embryonic midline constituting an embryonic linear heart tube. As development progress, the embryonic heart displays the first sign of left-right asymmetric morphology by the invariably rightward looping of the initial heart tube and prospective embryonic ventricular and atrial chambers emerged. As cardiac development progresses, the atrial and ventricular chambers enlarged and distinct left and right compartments emerge as consequence of the formation of the interatrial and interventricular septa, respectively. The last steps of cardiac morphogenesis are represented by the completion of atrial and ventricular septation, resulting in the configuration of a double circuitry with distinct systemic and pulmonary chambers, each of them with distinct inlets and outlets connections. Over the last decade, our understanding of the contribution of multiple growth factor signaling cascades such as Tgf-beta, Bmp and Wnt signaling as well as of transcriptional regulators to cardiac morphogenesis have greatly enlarged. Recently, a novel layer of complexity has emerged with the discovery of non-coding RNAs, particularly microRNAs and lncRNAs. Herein, we provide a state-of-the-art review of the contribution of non-coding RNAs during cardiac development. microRNAs and lncRNAs have been reported to functional modulate all stages of cardiac morphogenesis, spanning from lateral plate mesoderm formation to outflow tract septation, by modulating major growth factor signaling pathways as well as those transcriptional regulators involved in cardiac development.

A NOTCH1/LSD1/BMP2 co-regulatory network mediated by miR-137 negatively regulates osteogenesis of human adipose-derived stem cells

Background

MicroRNAs have been recognized as critical regulators for the osteoblastic lineage differentiation of human adipose-derived stem cells (hASCs). Previously, we have displayed that silencing of miR-137 enhances the osteoblastic differentiation potential of hASCs partly through the coordination of lysine-specific histone demethylase 1 (LSD1), bone morphogenetic protein 2 (BMP2), and mothers against decapentaplegic homolog 4 (SMAD4). However, still numerous molecules involved in the osteogenic regulation of miR-137 remain unknown. This study aimed to further elucidate the epigenetic mechanisms of miR-137 on the osteogenic differentiation of hASCs.

Methods

Dual-luciferase reporter assay was performed to validate the binding to the 3′ untranslated region (3′ UTR) of NOTCH1 by miR-137. To further identify the role of NOTCH1 in miR-137-modulated osteogenesis, tangeretin (an inhibitor of NOTCH1) was applied to treat hASCs which were transfected with miR-137 knockdown lentiviruses, then together with negative control (NC), miR-137 overexpression and miR-137 knockdown groups, the osteogenic capacity and possible downstream signals were examined. Interrelationships between signaling pathways of NOTCH1-hairy and enhancer of split 1 (HES1), LSD1 and BMP2-SMADs were thoroughly investigated with separate knockdown of NOTCH1, LSD1, BMP2, and HES1.

Results

We confirmed that miR-137 directly targeted the 3′ UTR of NOTCH1 while positively regulated HES1. Tangeretin reversed the effects of miR-137 knockdown on osteogenic promotion and downstream genes expression. After knocking down NOTCH1 or BMP2 individually, we found that these two signals formed a positive feedback loop as well as activated LSD1 and HES1. In addition, LSD1 knockdown induced NOTCH1 expression while suppressed HES1.

Conclusions

Collectively, we proposed a NOTCH1/LSD1/BMP2 co-regulatory signaling network to elucidate the modulation of miR-137 on the osteoblastic differentiation of hASCs, thus providing mechanism-based rationale for miRNA-targeted therapy of bone defect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02495-3.

Differential Spatio-Temporal Regulation of T-Box Gene Expression by microRNAs during Cardiac Development

Cardiovascular development is a complex process that starts with the formation of symmetrically located precardiac mesodermal precursors soon after gastrulation and is completed with the formation of a four-chambered heart with distinct inlet and outlet connections. Multiple transcriptional inputs are required to provide adequate regional identity to the forming atrial and ventricular chambers as well as their flanking regions; i.e., inflow tract, atrioventricular canal, and outflow tract. In this context, regional chamber identity is widely governed by regional activation of distinct T-box family members. Over the last decade, novel layers of gene regulatory mechanisms have been discovered with the identification of non-coding RNAs. microRNAs represent the most well-studied subcategory among short non-coding RNAs. In this study, we sought to investigate the functional role of distinct microRNAs that are predicted to target T-box family members. Our data demonstrated a highly dynamic expression of distinct microRNAs and T-box family members during cardiogenesis, revealing a relatively large subset of complementary and similar microRNA-mRNA expression profiles. Over-expression analyses demonstrated that a given microRNA can distinctly regulate the same T-box family member in distinct cardiac regions and within distinct temporal frameworks, supporting the notion of indirect regulatory mechanisms, and dual luciferase assays on Tbx2, Tbx3 and Tbx5 3' UTR further supported this notion. Overall, our data demonstrated a highly dynamic microRNA and T-box family members expression during cardiogenesis and supported the notion that such microRNAs indirectly regulate the T-box family members in a tissue- and time-dependent manner.

Priming mesenchymal stem cells with uric acid enhances neuroprotective properties in parkinsonian models

Mesenchymal stem cells (MSCs) are a potential source of cell-based disease-modifying therapy in Parkinsonian disorders. A promising approach to develop in vitro culture methods that mimic natural MSC niche is cell priming. Uric acid (UA), a powerful antioxidant, scavenges reactive oxygen species, which has a vital role in maintaining self-renewal and differentiation potential of MSCs. Here, we demonstrated that UA treatment in naïve MSCs stimulated glycolysis and upregulated transcriptional factors responsible for regulation of stemness, leading to increase in the expression levels of osteogenesis-, adipogenesis-, and chondrogenesis-related genes. UA-primed MSCs had more enhanced neuroprotective properties in cellular and parkinsonian animal models compared to naïve MSCs by inhibiting apoptotic signaling pathways. Additionally, expression of miR-137 and miR-145 was decreased in UA-treated MSCs. Our data demonstrated that priming MSCs with UA augment neuroprotective properties through enhanced self-renewal and differentiation potential, suggesting a practical strategy for improving the application of MSCs in parkinsonian disorders.

Portrait of Cancer Stem Cells on Colorectal Cancer: Molecular Biomarkers, Signaling Pathways and miRNAome

Colorectal cancer (CRC) is a leading cause of cancer death worldwide, and about 20% is metastatic at diagnosis and untreatable. Increasing evidence suggests that the heterogeneous nature of CRC is related to colorectal cancer stem cells (CCSCs), a small cells population with stemness behaviors and responsible for tumor progression, recurrence, and therapy resistance. Growing knowledge of stem cells (SCs) biology has rapidly improved uncovering the molecular mechanisms and possible crosstalk/feedback loops between signaling pathways that directly influence intestinal homeostasis and tumorigenesis. The generation of CCSCs is probably connected to genetic changes in members of signaling pathways, which control self-renewal and pluripotency in SCs and then establish function and phenotype of CCSCs. Particularly, various deregulated CCSC-related miRNAs have been reported to modulate stemness features, controlling CCSCs functions such as regulation of cell cycle genes expression, epithelial-mesenchymal transition, metastasization, and drug-resistance mechanisms. Primarily, CCSC-related miRNAs work by regulating mainly signal pathways known to be involved in CCSCs biology. This review intends to summarize the epigenetic findings linked to miRNAome in the maintenance and regulation of CCSCs, including their relationships with different signaling pathways, which should help to identify specific diagnostic, prognostic, and predictive biomarkers for CRC, but also develop innovative CCSCs-targeted therapies.

ZFHX3 Promotes the Proliferation and Tumor Growth of ER-Positive Breast Cancer Cells Likely by Enhancing Stem-Like Features and MYC and TBX3 Transcription

Simple Summary

Breast cancer is a common malignancy, but the understanding of its cellular and molecular mechanisms is limited. The ZFHX3 transcription factor regulates mammary epithelial cells’ proliferation and differentiation by interacting with estrogen and progesterone receptors. Both these receptors play crucial roles in breast cancer development, but whether ZFHX3 also impacts breast cancer is unknown. In this study, the authors aim to determine if ZFHX3 promotes breast cancer cells’ proliferation and tumor growth and explore the underlying cellular and molecular mechanisms. Higher ZFHX3 expression is associated with worse patient survival in breast cancer, ZFHX3 promotes the proliferation and tumor growth of breast cancer cells, and several breast cancer stem cell factors appear to be involved in the role of ZFHX3 in breast cancer growth. The findings suggest that ZFHX3 is a novel oncogenic molecule promoting breast cancer development. Such a molecule could provide novel opportunities for the treatment of breast cancer.

Abstract

Breast cancer is a common malignancy, but the understanding of its cellular and molecular mechanisms is limited. ZFHX3, a transcription factor with many homeodomains and zinc fingers, suppresses prostatic carcinogenesis but promotes tumor growth of liver cancer cells. ZFHX3 regulates mammary epithelial cells’ proliferation and differentiation by interacting with estrogen and progesterone receptors, potent breast cancer regulators. However, whether ZFHX3 plays a role in breast carcinogenesis is unknown. Here, we found that ZFHX3 promoted the proliferation and tumor growth of breast cancer cells in culture and nude mice; and higher expression of ZFHX3 in human breast cancer specimens was associated with poorer prognosis. The knockdown of ZFHX3 in ZFHX3-high MCF-7 cells decreased, and ZFHX3 overexpression in ZFHX3-low T-47D cells increased the proportion of breast cancer stem cells (BCSCs) defined by mammosphere formation and the expression of CD44, CD24, and/or aldehyde dehydrogenase 1. Among several transcription factors that have been implicated in BCSCs, MYC and TBX3 were transcriptionally activated by ZFHX3 via promoter binding, as demonstrated by luciferase-reporter and ChIP assays. These findings suggest that ZFHX3 promotes breast cancer cells’ proliferation and tumor growth likely by enhancing BCSC features and upregulating MYC, TBX3, and others.

miR-137: A Novel Therapeutic Target for Human Glioma

MicroRNA (miR)-137 is highly expressed in the brain and plays a crucial role in the development and prognosis of glioma. In this review, we aim to summarize the latest findings regarding miR-137 in glioma cell apoptosis, proliferation, migration, invasion, angiogenesis, drug resistance, and cancer treatment. In addition, we focus on the identified miR-137 targets and pathways in the occurrence and development of glioma. Finally, future implications for the diagnostic and therapeutic potential of miR-137 in glioma were discussed.

Neurodevelopmental concepts of schizophrenia in the genome-wide association era: AKT/mTOR signaling as a pathological mediator of genetic and environmental programming during development

Normative brain development is contingent on the complex interplay between genes and environment. Schizophrenia (SCZ) is considered a highly polygenic, neurodevelopmental disorder associated with impaired neural circuit development, neurocognitive function and variations in neurotransmitter signaling systems, including dopamine. Significant evidence, accumulated over the last 30 years indicates a role for the in utero environment in SCZ pathophysiology. Emerging data suggests that changes in placental programming and function may mediate the link between genetic risk, early life complications (ELC) and adverse neurodevelopmental outcomes, with risk highlighted in key developmental drivers that converge on AKT/mTOR signaling. In this article we overview select risk genes identified through recent genome-wide association studies of SCZ including AKT3, miR-137, DRD2, and AKT1 itself. We propose that through convergence on AKT/mTOR signaling, these genes are critical factors directing both placentation and neurodevelopment, influencing risk for SCZ through dysregulation of placental function, metabolism and early brain development. We discuss association of risk genes in the context of their known roles in neurodevelopment, placental expression and their possible mechanistic links to SCZ in the broad context of the 'developmental origins of adult disease' construct. Understanding how common genetic variation impacts early fetal programming may advance our knowledge of disease etiology and identify early critical developmental windows for prevention and intervention.

Expression Profiles of MicroRNAs in Stem Cells Differentiation

Stem cells are undifferentiated cells and have a great potential in multilineage differentiation. These cells are classified into adult stem cells like Mesenchymal Stem Cells (MSCs) and Embryonic Stem Cells (ESCs). Stem cells also have potential therapeutic utility due to their pluripotency, self-renewal, and differentiation ability. These properties make them a suitable choice for regenerative medicine. Stem cells differentiation toward functional cells is governed by different signaling pathways and transcription factors. Recent studies have demonstrated the key role of microRNAs in the pathogenesis of various diseases, cell cycle regulation, apoptosis, aging, cell fate decisions. Several types of stem cells have different and unique miRNA expression profiles. Our review summarizes novel regulatory roles of miRNAs in the process of stem cell differentiation especially adult stem cells into a variety of functional cells through signaling pathways and transcription factors modulation. Understanding the mechanistic roles of miRNAs might be helpful in elaborating clinical therapies using stem cells and developing novel biomarkers for the early and effective diagnosis of pathologic conditions.

MiRNA-137-mediated modulation of mitochondrial dynamics regulates human neural stem cell fate

The role of miRNAs in determining human neural stem cell (NSC) fate remains elusive despite their high expression in the developing nervous system. In this study, we investigate the role of miR‐137, a brain‐enriched miRNA, in determining the fate of human induced pluripotent stem cells‐derived NSCs (hiNSCs). We show that ectopic expression of miR‐137 in hiNSCs reduces proliferation and accelerates neuronal differentiation and migration. TargetScan and MicroT‐CDS predict myocyte enhancer factor‐2A (MEF2A), a transcription factor that regulates peroxisome proliferator‐activated receptor‐gamma coactivator (PGC1α) transcription, as a target of miR‐137. Using a reporter assay, we validate MEF2A as a downstream target of miR‐137. Our results indicate that reduced levels of MEF2A reduce the transcription of PGC1α, which in turn impacts mitochondrial dynamics. Notably, miR‐137 accelerates mitochondrial biogenesis in a PGC1α independent manner by upregulating nuclear factor erythroid 2 (NFE2)‐related factor 2 (NRF2) and transcription factor A of mitochondria (TFAM). In addition, miR‐137 modulates mitochondrial dynamics by inducing mitochondrial fusion and fission events, resulting in increased mitochondrial content and activation of oxidative phosphorylation (OXPHOS) and oxygen consumption rate. Pluripotency transcription factors OCT4 and SOX2 are known to have binding sites in the promoter region of miR‐137 gene. Ectopic expression of miR‐137 elevates the expression levels of OCT4 and SOX2 in hiNSCs which establishes a feed‐forward self‐regulatory loop between miR‐137 and OCT4/SOX2. Our study provides novel molecular insights into NSC fate determination by miR‐137.

The roles and regulation of TBX3 in development and disease

TBX3, a member of the ancient and evolutionary conserved T-box transcription factor family, is a critical developmental regulator of several structures including the heart, mammary glands, limbs and lungs. Indeed, mutations in the human TBX3 lead to ulnar mammary syndrome which is characterized by several clinical malformations including hypoplasia of the mammary and apocrine glands, defects of the upper limb, areola, dental structures, heart and genitalia. In contrast, TBX3 has no known function in adult tissues but is frequently overexpressed in a wide range of epithelial and mesenchymal derived cancers. This overexpression greatly impacts several hallmarks of cancer including bypass of senescence, apoptosis and anoikis, promotion of proliferation, tumour formation, angiogenesis, invasion and metastatic capabilities as well as cancer stem cell expansion. The debilitating consequences of having too little or too much TBX3 suggest that its expression levels need to be tightly regulated. While we have a reasonable understanding of the mutations that result in low levels of functional TBX3 during development, very little is known about the factors responsible for the overexpression of TBX3 in cancer. Furthermore, given the plethora of oncogenic processes that TBX3 impacts, it must be regulating several target genes but to date only a few have been identified and characterised. Interestingly, while there is compelling evidence to support oncogenic roles for TBX3, a few studies have indicated that it may also have tumour suppressor functions in certain contexts. Together, the diverse functional elasticity of TBX3 in development and cancer is thought to involve, in part, the protein partners that it interacts with and this area of research has recently received some attention. This review provides an insight into the significance of TBX3 in development and cancer and identifies research gaps that need to be explored to shed more light on this transcription factor.

MiR-137 knockdown promotes the osteogenic differentiation of human adipose-derived stem cells via the LSD1/BMP2/SMAD4 signaling network

MicroRNAs are a group of endogenous regulators that participate in several cellular physiological processes. However, the role of miR-137 in the osteogenic differentiation of human adipose-derived stem cells (hASCs) has not been reported. This study verified a general downward trend in miR-137 expression during the osteogenic differentiation of hASCs. MiR-137 knockdown promoted the osteogenesis of hASCs in vitro and in vivo. Mechanistically, inhibition of miR-137 activated the bone morphogenetic protein 2 (BMP2)-mothers against the decapentaplegic homolog 4 (SMAD4) pathway, whereas repressed lysine-specific histone demethylase 1 (LSD1), which was confirmed as a negative regulator of osteogenesis in our previous studies. Furthermore, LSD1 knockdown enhanced the expression of BMP2 and SMAD4, suggesting the coordination of LSD1 in the osteogenic regulation of miR-137. This study indicated that miR-137 negatively regulated the osteogenic differentiation of hASCs via the LSD1/BMP2/SMAD4 signaling network, revealing a new potential therapeutic target of hASC-based bone tissue engineering.

Current understanding and clinical utility of miRNAs regulation of colon cancer stem cells

Cancer stem cells (CSCs) in colorectal tumorigenesis are suggested to be responsible for initiation, development and propagation of colorectal cancer (CRC) and have been extensively characterized by the expression of phenotypic determinants, such as surface or intracellular proteins. The generation of CSCs is likely due to a dysregulation of the signaling pathways that principally control self-renewal and pluripotency in normal intestinal stem cells (ISCs) through different (epi)genetic changes that define cell fate, identity, and phenotype of CSCs. These aspects are currently under intense investigation. In the framework of the oncogenic signaling pathways controlled by microRNAs (miRNAs) during CRC development, a plethora of data suggests that miRNAs can play a key role in several regulatory pathways involving CSCs biology, epithelial-mesenchymal transition (EMT), angiogenesis, metastatization, and pharmacoresistance. This review examines the most relevant evidences about the role of miRNAs in the etiology of CRC, through the regulation of colon CSCs and the principal differences between colorectal CSCs and benign stem cells. In this perspective, the utility of the principal CSCs-related miRNAs changes is explored, emphasizing their use as potential biomarkers to aid in diagnosis, prognosis and predicting response to therapy in CRC patients, but also as promising targets for more effective and personalized anti-CRC treatments.

A comprehensive review of the genetic and biological evidence supports a role for MicroRNA-137 in the etiology of schizophrenia

Since it was first associated with schizophrenia (SCZ) in a 2011 genome-wide association study (GWAS), there have been over 100 publications focused on MIR137, the gene encoding microRNA-137. These studies have examined everything from its fundamental role in the development of mice, flies, and fish to the intriguing enrichment of its target gene network in SCZ. Indeed, much of the excitement surrounding MIR137 is due to the distinct possibility that it could regulate a gene network involved in SCZ etiology, a disease which we now recognize is highly polygenic. Here we comprehensively review, to the best of our ability, all published genetic and biological evidence that could support or refute a role for MIR137 in the etiology of SCZ. Through a careful consideration of the literature, we conclude that the data gathered to date continues to strongly support the involvement of MIR137 and its target gene network in neuropsychiatric traits, including SCZ risk. There remain, however, more unanswered than answered questions regarding the mechanisms linking MIR137 genetic variation with behavior. These questions need answers before we can determine whether there are opportunities for diagnostic or therapeutic interventions based on MIR137. We conclude with a number of suggestions for future research on MIR137 that could help to provide answers and hope for a greater understanding of this devastating disorder.

Roles of microRNAs and RNA-Binding Proteins in the Regulation of Colorectal Cancer Stem Cells

Colorectal cancer stem cells (CSCs) are responsible for the initiation, progression and metastasis of human colorectal cancers, and have been characterized by the expression of cell surface markers, such as CD44, CD133, CD166 and LGR5. MicroRNAs (miRNAs) are differentially expressed between CSCs and non-tumorigenic cancer cells, and play important roles in the maintenance and regulation of stem cell properties of CSCs. RNA binding proteins (RBPs) are emerging epigenetic regulators of various RNA processing events, such as splicing, localization, stabilization and translation, and can regulate various types of stem cells. In this review, we summarize current evidences on the roles of miRNA and RBPs in the regulation of colorectal CSCs. Understanding the epigenetic regulation of human colorectal CSCs will help to develop biomarkers for colorectal cancers and to identify targets for CSC-targeting therapies.

The tumour suppressor, miR-137, inhibits malignant melanoma migration by targetting the TBX3 transcription factor

The transcription factor, TBX3, is a key driver of malignant melanoma and any drug that impacts its expression is likely to have an impact on the treatment of this highly aggressive and treatment resistant cancer. Replacement of miRNAs that target oncogenes has gained much attention as a therapy because it is anticipated to be effective with little side-effects since miRNAs are naturally occurring and often target large set of genes in the same oncogenic pathway. Here we show that miR-137 levels correlate inversely with TBX3 mRNA levels in a panel of melanoma cell lines and in a cohort of patients with primary melanoma. Low levels of miR-137 and high levels of TBX3 are shown to be associated with poor patient survival. We show that miR-137 binds a conserved site in the TBX3 3' untranslated region and that a miR-137 mimic significantly reduces endogenous levels of TBX3 and inhibits anchorage independent growth and migration of malignant melanoma cells. Novel data are provided that the miR-137/TBX3/E-cadherin axis plays an important role in melanomagenesis and that miR-137 replacement is a potential therapeutic approach for treating melanomas.

MiR-137: an important player in neural development and neoplastic transformation

MicroRNAs (miRNAs) represent an important class of small regulatory RNAs that control gene expression posttranscriptionally by targeting mRNAs for degradation or translation inhibition. Early studies have revealed a complex role for miRNAs in major biological processes such as development, differentiation, growth and metabolism. MiR-137 in particular, has been of great interest due to its critical role in brain function and putative involvement in the etiology of both neuropsychiatric disorders and cancer. Several lines of evidence suggest that development, differentiation and maturation of the nervous system is strongly linked to the expression of miR-137 and its regulation of a large number of downstream target genes in various pathways. Dysregulation of this molecule has also been implicated in major mental illnesses through its position in a variant allele highly associated with schizophrenia in the largest mega genome-wide association studies. Interestingly, miR-137 has also been shown to act as a tumor suppressor, with numerous studies finding reduced expression in neoplasia including brain tumor. Restoration of miR-137 expression has also been shown to inhibit cell proliferation, migration and metastasis, and induce cell cycle arrest, differentiation and apoptosis. These properties of miR-137 propose its potential for prognosis, diagnosis and as a therapeutic target for treatment of several human neurological and neoplastic disorders. In this review, we provide details on the discovery, targets, function, regulation and disease involvement of miR-137 with a broad look at recent discovery in this area.

MiR-137 affects melanin synthesis in mouse melanocyte by repressing the expression of c-Kit and Tyrp2 in SCF/c-Kit signaling pathway

Previously, we created miR-137 overexpressing transgenic mice that produced lighten color phenotypes including gray mice phenotype. However, the miR-137 functional role in coat color regulation is still not well understood. In this study, the quantity of melanin granule and the relative expression of TYRP2 in gray miR-137 overexpression transgenic mouse skin were significantly lower than that in C57BL/6J black mouse skin. The mRNA and protein expression level of c-Kit and c-Kit downstream gene Tyrp2 in miR-137 expression plasmid-transfected melanocytes were significantly down-regulated comparing with that of the control melanocytes. In melanocytes, miR-137 overexpression could decrease the enhanced expression of c-Kit and Tyrp2 and the increased melanin production caused by UV treatment. The target relationship of miR-137 and c-Kit was identified by luciferase assay. The results suggest that miR-137 could inhibit melanogenesis in mouse skin melanocytes by repressing the expression of c-Kit and Tyrp2 in SCF/c-Kit signaling pathway.

Regulation of the T-box transcription factor Tbx3 by the tumour suppressor microRNA-206 in breast cancer

BACKGROUND

The Tbx3 transcription factor is over-expressed in breast cancer, where it has been implicated in proliferation, migration and regulation of the cancer stem cell population. The mechanisms that regulate Tbx3 expression in cancer have not been fully explored. In this study, we demonstrate that Tbx3 is repressed by the tumour suppressor miR-206 in breast cancer cells.

METHODS

Bioinformatics prediction programmes and luciferase reporter assays were used to demonstrate that miR-206 negatively regulates Tbx3. We examined the impact of miR-206 on Tbx3 expression in breast cancer cells using miR-206 mimic and inhibitor. Gene/protein expression was examined by quantitative reverse-transcription-PCR and immunoblotting. The effects of miR-206 and Tbx3 on apoptosis, proliferation, invasion and cancer stem cell population was investigated by cell-death detection, colony formation, 3D-Matrigel and tumorsphere assays.

RESULTS

In this study, we examined the regulation of Tbx3 by miR-206. We demonstrate that Tbx3 is directly repressed by miR-206, and that this repression of Tbx3 is necessary for miR-206 to inhibit breast tumour cell proliferation and invasion, and decrease the cancer stem cell population. Moreover, Tbx3 and miR-206 expression are inversely correlated in human breast cancer. Kaplan-Meier analysis indicates that patients exhibiting a combination of high Tbx3 and low miR-206 expression have a lower probability of survival when compared with patients with low Tbx3 and high miR-206 expression. These studies uncover a novel mechanism of Tbx3 regulation and identify a new target of the tumour suppressor miR-206.

CONCLUSIONS

The present study identified Tbx3 as a novel target of tumour suppressor miR-206 and characterised the miR-206/Tbx3 signalling pathway, which is involved in proliferation, invasion and maintenance of the cancer stem cell population in breast cancer cells. Our results suggest that restoration of miR-206 in Tbx3-positive breast cancer could be exploited for therapeutic benefit.

Meta gene set enrichment analyses link miR-137-regulated pathways with schizophrenia risk

BACKGROUND

A single nucleotide polymorphism (SNP) within MIR137, the host gene for miR-137, has been identified repeatedly as a risk factor for schizophrenia. Previous genetic pathway analyses suggest that potential targets of this microRNA (miRNA) are also highly enriched in schizophrenia-relevant biological pathways, including those involved in nervous system development and function.

METHODS

In this study, we evaluated the schizophrenia risk of miR-137 target genes within these pathways. Gene set enrichment analysis of pathway-specific miR-137 targets was performed using the stage 1 (21,856 subjects) schizophrenia genome wide association study data from the Psychiatric Genomics Consortium and a small independent replication cohort (244 subjects) from the Mind Clinical Imaging Consortium and Northwestern University.

RESULTS

Gene sets of potential miR-137 targets were enriched with variants associated with schizophrenia risk, including target sets involved in axonal guidance signaling, Ephrin receptor signaling, long-term potentiation, PKA signaling, and Sertoli cell junction signaling. The schizophrenia-risk association of SNPs in PKA signaling targets was replicated in the second independent cohort.

CONCLUSIONS

These results suggest that these biological pathways may be involved in the mechanisms by which this MIR137 variant enhances schizophrenia risk. SNPs in targets and the miRNA host gene may collectively lead to dysregulation of target expression and aberrant functioning of such implicated pathways. Pathway-guided gene set enrichment analyses should be useful in evaluating the impact of other miRNAs and target genes in different diseases.

Association of a miRNA-137 polymorphism with schizophrenia in a Southern Chinese Han population

Both genome wide association study (GWAS) and biochemical studies of Caucasian populations indicate a robust association between the miR-137 genetic variant rs1625579 and schizophrenia, but inconsistent results have been reported. To assay the association between this variant and schizophrenia, we genotyped 611 schizophrenic patients from Southern Chinese Han population for the risk single nucleotide polymorphism (SNP) rs1625579 using the SNaPshot technique and compared the clinical profiles of different genotypes. Additionally, a meta-analysis was performed using the combined sample groups from five case-control publications and the present study. Both the genotype and allele distributions of the rs1625579 SNP were significantly different between patients and controls (P = 0.036 and 0.026, SNP). TT genotype carriers showed slightly lower Brief Assessment of Cognition in Schizophrenia- (BACS-) derived working memory performance than G carriers (15.58 ± 9.56 versus 19.71 ± 8.18, P = 0.045). In the meta-analysis, we observed a significant association between rs1625579 and schizophrenia under different genetic models (all P < 0.05). The results of our study and meta-analysis provide convincing evidence that rs1625579 is significantly associated with schizophrenia. Furthermore, the miR-137 polymorphism influences the working memory performance of schizophrenic patients in a Chinese Han population.

miR-137: a new player in schizophrenia

Schizophrenia is a complex genetic disease and characterized by affective, cognitive, neuromorphological, and molecular abnormalities that may have a neurodevelopmental origin. MicroRNAs (miRNAs) are critical to neurodevelopment and adult neuronal processes by modulating the activity of multiple genes within biological networks. MiR-137 as a brain-enriched microRNA, plays important roles in regulating embryonic neural stem cells (NSCs) fate determination, neuronal proliferation and differentiation, and synaptic maturation. Its dysregulation causes changes in the gene expression regulation network of the nervous system, thus inducing mental disorders. Recently, miR-137 has been confirmed as a gene related to schizophrenia susceptibility. In the following review, we summarize the expression pattern, epigenetic regulation and functions of miR-137. A more complete picture of the miR-137, which is dysregulated in psychiatric illness, may improve our understanding of the molecular mechanisms underlying schizophrenia.

MicroRNAs and epigenetics in adult neurogenesis

Neurogenesis occurs throughout adulthood in the mammalian brain. Neural stem cells (NSCs) exist in three distinct areas of the brain: the subventricular zone, the olfactory bulb, and the dentate gyrus of the hippocampus. MicroRNAs (miRNAs) are small noncoding RNA molecules that posttranscriptionally regulate gene expression. Epigenetic regulation of gene expression, which includes DNA methylation and histone modification, plays a significant role in modulating NSC proliferation and differentiation. However, the functions of miRNAs in neurogenesis are just beginning to be understood. Based on the recent literature, miRNAs are suggested to play an important role in the epigenetic regulation of NSCs and differentiation of lineage populations, which include neurons, astrocytes, and oligodendrocytes. Recent studies have elucidated the roles of miRNAs in embryonic and adult neurogenesis, specifically, their involvement in stem cell maintenance and differentiation, neuronal maturation and neurite outgrowth, dendritogenesis, and spine formation. The cross-talk between miRNAs and epigenetic regulators appears to modulate neurogenesis in the adult mammalian brain. Since the dysfunction in miRNA machinery contributes to many types of neurodegenerative disorders, a better understanding of how miRNAs influence the neurogenesis and differentiation may offer novel targets for therapeutic application.

Role of miRNAs and epigenetics in neural stem cell fate determination

The regulation of gene expression that determines stem cell fate determination is tightly controlled by both epigenetic and posttranscriptional mechanisms. Indeed, small non-coding RNAs such as microRNAs (miRNAs) are able to regulate neural stem cell fate by targeting chromatin-remodeling pathways. Here, we aim to summarize the latest findings regarding the feedback network of epigenetics and miRNAs during embryonic and adult neurogenesis.

MicroRNAs as the cause of schizophrenia in 22q11.2 deletion carriers, and possible implications for idiopathic disease: a mini-review

The 22q11.2 deletion is the strongest known genetic risk factor for schizophrenia. Research has implicated microRNA-mediated dysregulation in 22q11.2 deletion syndrome (22q11.2DS) schizophrenia-risk. Primary candidate genes are DGCR8 (DiGeorge syndrome critical region gene 8), which encodes a component of the microprocessor complex essential for microRNA biogenesis, and MIR185, which encodes microRNA 185. Mouse models of 22q11.2DS have demonstrated alterations in brain microRNA biogenesis, and that DGCR8 haploinsufficiency may contribute to these alterations, e.g., via down-regulation of a specific microRNA subset. miR-185 was the top-scoring down-regulated microRNA in both the prefrontal cortex and the hippocampus, brain areas which are the key foci of schizophrenia research. This reduction in miR-185 expression contributed to dendritic and spine development deficits in hippocampal neurons. In addition, miR-185 has two validated targets (RhoA, Cdc42), both of which have been associated with altered expression levels in schizophrenia. These combined data support the involvement of miR-185 and its down-stream pathways in schizophrenia. This review summarizes evidence implicating microRNA-mediated dysregulation in schizophrenia in both 22q11.2DS-related and idiopathic cases.