miR-17 regulates the proliferation and differentiation of the neural precursor cells during mouse corticogenesis

Association between Mir-17-92 gene promoter polymorphisms and depression in a Chinese population

BACKGROUND

Depression is a common chronic debilitating disease with a heavy social burden. single nucleotide polymorphisms (SNPs) can affect the function of microRNAs (miRNAs), which is in turn associated with neurological diseases. However, the association between SNPs located in the promoter region of miR-17-92 and the risk of depression remains unclear. Therefore, we investigated the association between rs982873, rs9588884 and rs1813389 polymorphisms in the promoter region of miR-17-92 and the incidence of depression in a Chinese population.

METHODS

we used GWAS (Genome-wide association study) and NCBI (National Center for Biotechnology Information) to screen three SNPs in the miR-17-92 cluster binding sites. A case-control study (including 555 cases and 541 controls) was conducted to investigate the relationship between the SNPs and risk of depression in different regions of China. The gene sequencing ii was used to genotype the collected blood samples.

RESULTS

the following genotypes were significantly associated with a reduced risk of depression: rs982873 TC (TC vs. TT: OR = 0.72, 95% CI, 0.54-0.96, P = 0.024; TC/CC vs. TT: OR = 0.74, 95% Cl, 0.56-0.96, P = 0.025); CG genotype of rs9588884 (CG vs. CC: OR = 0.74, 95% CI, 0.55-0.98, P = 0.033; CG/GG vs. CC: OR = 0.75, 95% Cl, 0.57-0.98, P = 0.036); and AG genotype of rs1813389 (AG vs. AA: OR = 0.75, 95% CI, 0.57-1.00, P = 0.049; AG/GG vs. AA: OR = 0.76, 95% Cl, 0.59-1.00, P = 0.047). Stratified analysis showed that there was no significant correlation between the three SNPS and variables such as family history of suicidal tendency (P > 0.05).

CONCLUSIONS

our findings suggest that rs982873, rs9588884, and rs1813389 polymorphisms may be associated with protective factors for depression.

microRNA and the Post-Transcriptional Response to Oxidative Stress during Neuronal Differentiation: Implications for Neurodevelopmental and Psychiatric Disorders

Oxidative stress is one of the most important environmental exposures associated with psychiatric disorders, but the underlying molecular mechanisms remain to be elucidated. In a previous study, we observed a substantial alteration of the gene expression landscape in neuron-like cells that were differentiated from SH-SY5Y cells after or during exposure to oxidative stress, with a subset of dysregulated genes being enriched for neurodevelopmental processes. To further explore the regulatory mechanisms that might account for such profound perturbations, we have now applied small RNA-sequencing to investigate changes in the expression of miRNAs. These molecules are known to play crucial roles in brain development and response to stress through their capacity to suppress gene expression and influence complex biological networks. Through these analyses, we observed more than a hundred differentially expressed miRNAs, including 80 previously reported to be dysregulated in psychiatric disorders. The seven most influential miRNAs associated with pre-treatment exposure, including miR-138-5p, miR-96-5p, miR-34c-5p, miR-1287-5p, miR-497-5p, miR-195-5p, and miR-16-5p, supported by at least 10 negatively correlated mRNA connections, formed hubs in the interaction network with 134 genes enriched with neurobiological function, whereas in the co-treatment condition, miRNA-mRNA interaction pairs were enriched in cardiovascular and immunity-related disease ontologies. Interestingly, 12 differentially expressed miRNAs originated from the DLK1-DIO3 location, which encodes a schizophrenia-associated miRNA signature. Collectively, our findings suggest that early exposure to oxidative stress, before and during prenatal neuronal differentiation, might increase the risk of mental illnesses in adulthood by disturbing the expression of miRNAs that regulate neurodevelopmentally significant genes and networks.

Role of Post-Transcriptional Regulation in Learning and Memory in Mammals

After many decades, during which most molecular studies on the regulation of gene expression focused on transcriptional events, it was realized that post-transcriptional control was equally important in order to determine where and when specific proteins were to be synthesized. Translational regulation is of the most importance in the brain, where all the steps of mRNA maturation, transport to different regions of the cells and actual expression, in response to specific signals, constitute the molecular basis for neuronal plasticity and, as a consequence, for structural stabilization/modification of synapses; notably, these latter events are fundamental for the highest brain functions, such as learning and memory, and are characterized by long-term potentiation (LTP) of specific synapses. Here, we will discuss the molecular bases of these fundamental events by considering both the role of RNA-binding proteins (RBPs) and the effects of non-coding RNAs involved in controlling splicing, editing, stability and translation of mRNAs. Importantly, it has also been found that dysregulation of mRNA metabolism/localization is involved in many pathological conditions, arising either during brain development or in the adult nervous system.

miR-17∼92 exerts stage-specific effects in adult V-SVZ neural stem cell lineages

Neural stem cells (NSCs) in the adult ventricular-subventricular zone (V-SVZ) generate neurons and glia throughout life. MicroRNAs are important post-transcriptional regulators frequently acting in a context-dependent manner. Here, microRNA profiling defines cohorts of miRNAs in quiescent and activated NSCs, with miR-17∼92 highly upregulated in activated NSCs and transit amplifying cells (TACs) versus quiescent NSCs. Conditional miR-17∼92 deletion in the adult V-SVZ results in stage-specific effects. In NSCs, it reduces proliferation in vitro and in vivo, whereas in TACs, it selectively shifts neurogenic OLIG2^- DLX2⁺ toward oligodendrogenic OLIG2⁺ DLX2^- TACs, due to de-repression of an oligodendrogenic program, leading to increased oligodendrogenesis in vivo. This differential regulation of TAC subpopulations highlights the importance of TAC heterogeneity. Finally, in the NSC lineage for intraventricular oligodendrocyte progenitors, miR-17∼92 deletion decreases proliferation and maturation. Together, these findings reveal multiple stage-specific functions of the miR-17∼92 cluster within different adult V-SVZ lineages.

Functions of the bone morphogenetic protein signaling pathway through non-coding RNAs

Bone morphogenetic proteins (BMPs) are proteins of the transforming growth factor-β (TGF-β) family, which plays an important role in the formation of skeletal and cartilage tissue and their regeneration. BMPs play a key role in the formation of new blood vessels and promote the migration, proliferation, and differentiation of mesenchymal stem cells (MSCs) into chondroblasts and osteoblasts. It is known that malfunction of BMPs signaling can cause a disease state. Epigenetic regulation of expression plays a key role in the control of many cellular processes. Important participants in this regulation are non-coding RNAs (ncRNAs), which are RNA molecules that are not translated into proteins. The best known of these are microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). In addition, the results of many studies make it possible to establish an unambiguous functional relationship between these ncRNAs. Being involved in the regulation of a large number of target genes responsible for the life of the cell, miRNAs, lncRNAs, and circRNAs are essential for the normal development and functioning of the body, and the violation of their functions accompanies the development of many pathophysiological processes including oncogenesis. In the present review, we discuss different insights into the regulation of BMPs signaling pathway by miRNAs, lncRNAs and circRNAs governed.

RNA processing in neurological tissue: development, aging and disease

Gene expression comprises a diverse array of enzymes, proteins, non-coding transcripts, and cellular structures to guide the transfer of genetic information to its various final products. In the brain, the coordination among genes, or lack thereof, characterizes individual brain regions, mediates a variety of brain-related disorders, and brings light to fundamental differences between species. RNA processing, occurring between transcription and translation, controls an essential portion of gene expression through splicing, editing, localization, stability, and interference. The machinery to regulate transcripts must operate with precision serving as a blueprint for proteins and non-coding RNAs to derive their identity. Therefore, RNA processing has a broad scope of influence in the brain, as it modulates cell morphogenesis during development and underlies mechanisms behind certain neurological diseases. Here, we present these ideas through recent findings on RNA processing in development and post-developmental maturity to advance therapeutic discoveries and the collective knowledge of the RNA life cycle.

The microRNA-17 ~ 92 Family as a Key Regulator of Neurogenesis and Potential Regenerative Therapeutics of Neurological Disorders

miR-17 ~ 92, an miRNA family containing three paralogous polycistronic clusters, was initially considered as an oncogene and was later demonstrated to trigger various physiological and pathological processes. Emerging evidence has implicated miR-17 ~ 92 family as a master regulator of neurogenesis. Through targeting numerous genes that affect cell cycle arrest, stemness deprivation, and lineage commitment, miR-17 ~ 92 family controls the proliferation and neuronal differentiation of neural stem/progenitor cells in both developmental and adult brains. Due to the essential roles of miR-17 ~ 92 family, its misexpression is widely associated with acute and chronic neurological disorders by attenuating neurogenesis and facilitating neuronal apoptosis. The promising neurogenic potential of miR-17 ~ 92 family also makes it a promising “medicine” to activate the endogenous and exogenous regenerative machinery, thus enhance tissue repair and function recovery after brain injury. In this review, we focus on the recent progress made toward understanding the involvement of miR-17 ~ 92 family in regulating both developmental and adult neurogenesis, and discuss the regenerative potential of miR-17 ~ 92 family in treating neurological disorders.

MicroRNA-Based Separation of Cortico-Fugal Projection Neuron-Like Cells Derived From Embryonic Stem Cells

The purification of pluripotent stem cell-derived cortico-fugal projection neurons (PSC-CFuPNs) is useful for disease modeling and cell therapies related to the dysfunction of cortical motor neurons, such as amyotrophic lateral sclerosis (ALS) or stroke. However, no CFuPN-specific surface markers for the purification are known. Recently, microRNAs (miRNAs) have been reported as alternatives to surface markers. Here, we investigated this possibility by applying the miRNA switch, an mRNA technology, to enrich PSC-CFuPNs. An array study of miRNAs in mouse fetal brain tissue revealed that CFuPNs highly express miRNA-124-3p at E14.5 and E16.5. In response, we designed a miRNA switched that responds to miRNA-124-3p and applied it to mouse embryonic stem cell (ESC)-derived cortical neurons. Flow cytometry and quantitative polymerase chain reaction (qPCR) analyses showed the miRNA-124-3p switch enriched CFuPN-like cells from this population. Immunocytechemical analysis confirmed vGlut1/Emx1/Bcl11b triple positive CFuPN-like cells were increased from 6.5 to 42%. Thus, our miRNA-124-3p switch can uniquely enrich live CFuPN-like cells from mouse ESC-derived cortical neurons.

MicroRNAs miR-25, let-7 and miR-124 regulate the neurogenic potential of Müller glia in mice

Müller glial cells (MG) generate retinal progenitor (RPC)-like cells after injury in non-mammalian species, although this does not occur in the mammalian retina. Studies have profiled gene expression in these cells to define genes that may be relevant to their differences in neurogenic potential. However, less is known about differences in micro-RNA (miRNA) expression. In this study, we compared miRNAs from RPCs and MG to identify miRNAs more highly expressed in RPCs, and others more highly expressed in MG. To determine whether these miRNAs are relevant to the difference in neurogenic potential between these two cell types, we tested them in dissociated cultures of MG using either mimics or antagomiRs to increase or reduce expression, respectively. Among the miRNAs tested, miR-25 and miR-124 overexpression, or let-7 antagonism, induced Ascl1 expression and conversion of ∼40% of mature MG into a neuronal/RPC phenotype. Our results suggest that the differences in miRNA expression between MG and RPCs contribute to their difference in neurogenic potential, and that manipulations in miRNAs provide a new tool with which to reprogram MG for retinal regeneration.

miR-155-5p Promotes Dorsal Root Ganglion Neuron Axonal Growth in an Inhibitory Microenvironment via the cAMP/PKA Pathway

Sensory dysfunction post spinal cord injury causes patients great distress. Sciatic nerve conditioning injury (SNCI) has been shown to restore sensory function after spinal cord dorsal column injury (SDCL); however, the underlying mechanism of this recovery remains unclear. We performed a microarray assay to determine the associated miRNAs that might regulate the process of SNCI promoting SDCL repair. In total, 13 miRNAs were identified according to our inclusion criteria, and RT-qPCR was used to verify the microarray results. Among the 13 miRNAs, the miR-155-5p levels were decreased at 9 h, 3 d, 7 d, 14 d, 28 d, 2 m and 3 m timepoints in the SDCL group, while the SNCI group had a smaller decrease. Thus, miR-155-5p was chosen for further study after a literature review and an analysis with the TargetScan online tool. Specifically, miR-155-5p targets PKI-α, and the expression pattern of PKI-α was opposite that of miR-155-5p in both the SDCL and SNCI groups. Interestingly, miR-155-5p could promote dorsal root ganglion (DRG) neuron axon growth via the cAMP/PKA pathway and in a TNF-α, IL-1β or MAG inhibitory microenvironment in vitro. Furthermore, miR-155-5p could regulate the cAMP/PKA pathway and promote sensory conduction function recovery post dorsal column injury as detected by NF-200 immunohistochemistry, somatosensory-evoked potentials, BBB scale and tape removal test. Collectively, our results demonstrated that miR-155-5p participates in the molecular mechanism by which SNCI promotes the repair of SDCL and that upregulated miR-155-5p can repair SDCL by enhancing DRG neuron axon growth via the cAMP/PKA pathway. These findings suggest a novel treatment target for spinal cord injury.

Upregulation of microRNA-17-5p contributes to hypoxia-induced proliferation in human pulmonary artery smooth muscle cells through modulation of p21 and PTEN

BACKGROUND

Pulmonary arterial smooth muscle cell (PASMC) proliferation in response to hypoxia plays an important role in the vascular remodelling that occurs in hypoxic pulmonary hypertension. MicroRNAs (miRs) are emerging as important regulators in the progression of pulmonary hypertension. In this study, we investigated whether the expression of miR-17-5p is modulated by hypoxia and is involved in the hypoxia-induced proliferation of PASMCs.

METHODS

Human PASMCs were cultured under hypoxic conditions. miR-17-5p expression was determined by real-time RT-PCR. A BrdU incorporation assay and time-lapse recording were utilized to determine cell proliferation and migration.

RESULTS

PASMC proliferation was increased by moderate hypoxia (3% oxygen) but was reduced by severe hypoxia (0.1% oxygen) after 48 h. Moderate hypoxia induced miR-17-5p expression. Overexpression of miR-17-5p by transfection with miR-17-5p enhanced cell proliferation and migration in normoxia, whereas knockdown of miR-17-5p with anti-miR-17-5p inhibitors significantly reduced cell proliferation and migration. The expression of miR-17-5p target genes, specifically phosphatase and tensin homologue (PTEN) and cyclin-dependent kinase inhibitor 1 (p21WAF1/Cip1, p21), was reduced under moderate hypoxia in PASMCs. Under normoxia, overexpression of miR-17-5p in PASMCs reduced the expression of PTEN and p21.

CONCLUSION

Our data indicate that miR-17-5p might play a significant role in hypoxia-induced pulmonary vascular smooth muscle cell proliferation by regulating multiple gene targets, including PTEN and p21, and that miR-17-5p could be a novel therapeutic target for the management of hypoxia-induced PH.

Treating the placenta to prevent adverse effects of gestational hypoxia on fetal brain development

Some neuropsychiatric disease, including schizophrenia, may originate during prenatal development, following periods of gestational hypoxia and placental oxidative stress. Here we investigated if gestational hypoxia promotes damaging secretions from the placenta that affect fetal development and whether a mitochondria-targeted antioxidant MitoQ might prevent this. Gestational hypoxia caused low birth-weight and changes in young adult offspring brain, mimicking those in human neuropsychiatric disease. Exposure of cultured neurons to fetal plasma or to secretions from the placenta or from model trophoblast barriers that had been exposed to altered oxygenation caused similar morphological changes. The secretions and plasma contained altered microRNAs whose targets were linked with changes in gene expression in the fetal brain and with human schizophrenia loci. Molecular and morphological changes in vivo and in vitro were prevented by a single dose of MitoQ bound to nanoparticles, which were shown to localise and prevent oxidative stress in the placenta but not in the fetus. We suggest the possibility of developing preventative treatments that target the placenta and not the fetus to reduce risk of psychiatric disease in later life.

A role for miR-19 in the migration of adult-born neurons and schizophrenia

The latest miRNA database (Release 21) annotated 2588 and 1915 miRNAs in the human and mouse genomes, respectively.¹ However, the biological roles of miRNAs in vivo remain largely unknown. In particular, the physiological and pathological roles of individual microRNAs in the brain have not been investigated extensively although expression profiles of microRNAs have been reported in many given conditions. In a recent study,² we identified miR-19, which is enriched in adult hippocampal neural progenitor cells (NPCs), as a key regulator for adult hippocampal neurogenesis. miR-19 is an intrinsic factor regulating the migration of newborn neurons by modulating expression level of RAPGEF2. After observing the abnormal expression patterns of miR-19 and RAPGEF2 in NPCs derived from induced pluripotent stem cells of schizophrenic patients, which display aberrant cell migration, we proposed miR-19 as a molecule associated with schizophrenia. The results illustrate that a single microRNA has the potential to impact the functions of the brain. Identifying miRNA-mediated posttranscriptional gene regulation in the brain will expand our understanding of brain development and functions and the etiologies of several brain disorders.

The role of the miR-17-92 cluster in neurogenesis and angiogenesis in the central nervous system of adults

It is well known that neurogenesis is not the only concern for the fully functional recovery after brain or spinal cord injury, as it has been shed light on the critical role of angiogenesis in improving neurological functional recovery. Angiogenesis and neurogenesis coordinately interact with each other in the developing and adult brain, during which they may respond to similar mediators and receptors, in which they share a common posttranscriptional regulator: the miR-17-92 cluster. The miR-17-92 cluster was initially described as an oncogene and was later demonstrated to drive key physiological and pathological responses during development and diseases respectively. It has been reported that the miR-17-92 cluster regulates both neurogenesis and angiogenesis. The miR-17-92 cluster modulates neural progenitor cells proliferation not only during development but also during neurological disorders such as stroke. It has also been shown that the endothelial miR-17-92 cluster regulates angiogenesis during embryonic stage and adulthood. In this review, we have discussed the actions of the miR-17-92 cluster in neuronal and vascular plasticity, and its potential as a novel therapeutic strategy for CNS injury. © 2016 Wiley Periodicals, Inc.

miR-17-92 facilitates neuronal differentiation of transplanted neural stem/precursor cells under neuroinflammatory conditions

Background

Neural stem/precursor cells (NSCs) are of particular interest because of their potential application in cell therapy for brain damage. However, most brain injury cases are followed with neuroinflammatory stress, which affects the lineage selection of grafted NSCs by promoting astrocytogenesis, thus hampering the potential for neural replacement. The present study investigated the role of miR-17-92 in protecting against detrimental effects of neuroinflammation on NSC differentiation in cell therapy.

Methods

NSCs were treated with conditioned medium from lesioned astrocytes with/without neutralizing antibodies of leukemia inhibitory factor (LIF) or/and ciliary neurotrophic factor (CNTF), respectively. Afterward, the levels of p-STAT3 and p-JAK2 were determined by western blotting while expression of glial fibrillary acidic protein (GFAP) and β-tubulin III was assessed by immunostaining. The activation of JAK-STAT pathway and cell differentiation were also evaluated after we overexpressed miR-17-92 in NSCs under different neuroinflammatory conditions. After the transplantation of miR-17-92-overexpressing NSCs into injured mouse cortex, PH3, nestin, GFAP, and NeuN were analyzed by immunostaining. In addition, motor coordination of mice was evaluated by rotarod test.

Results

Conditioned medium from lesioned astrocytes activated JAK-STAT pathway and facilitated astrocytic differentiation in NSCs while neutralizing antibodies of LIF and CNTF remarkably attenuated such effects. miR-17-92 cluster repressed the expression of multiple proteins including GP130, CNTFR, JAK2, and STAT3 in JAK-STAT pathway. Overexpression of miR-17-92 in NSCs systematically blocked the activation of JAK-STAT pathway mediated by LIF and CNTF, which facilitated neuronal differentiation in vitro. Furthermore, miR-17-92 increased neuronal generation of grafted NSCs and reduced astrogliosis, which resulted in the improvement of motor coordination of brain-injured mice.

Conclusions

Our results suggest that miR-17-92 promotes neuronal differentiation of grafted NSCs under neuroinflammatory condition via inhibition of multiple proteins in JAK-STAT pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0685-5) contains supplementary material, which is available to authorized users.

Signaling Receptors for TGF-β Family Members

Transforming growth factor β (TGF-β) family members signal via heterotetrameric complexes of type I and type II dual specificity kinase receptors. The activation and stability of the receptors are controlled by posttranslational modifications, such as phosphorylation, ubiquitylation, sumoylation, and neddylation, as well as by interaction with other proteins at the cell surface and in the cytoplasm. Activation of TGF-β receptors induces signaling via formation of Smad complexes that are translocated to the nucleus where they act as transcription factors, as well as via non-Smad pathways, including the Erk1/2, JNK and p38 MAP kinase pathways, and the Src tyrosine kinase, phosphatidylinositol 3'-kinase, and Rho GTPases.

Altered MicroRNA Expression Is Associated with Tumor Grade, Molecular Background and Outcome in Childhood Infratentorial Ependymoma

Background

Ependymal tumors are the third most common group of brain tumors in children, accounting for about 10% of all primary brain neoplasms. According to the current WHO classification, they comprise four entities with the most frequent ependymoma and anaplastic ependymoma. The most of pediatric tumors are located within the posterior fossa, with a tendency to infiltrate the vital brain structures. This limits surgical resection and poses a considerable clinical problem. Moreover, there are no appropriate outcome prognostic factors besides the extent of surgical resection. Despite definition of molecular subgroups, the majority of childhood ependymomas present a balanced genome, which makes it difficult to establish molecular prognostic factors.

Methods

The purpose of our study was to explore whether miRNA expression could be used as prognostic markers in pediatric infratentorial ependymomas. We also performed a mRNA expression pattern analysis of NELL2 and LAMA2 genes, with immunohistochemical illustrations of representative cases. The miRNA and mRNA expression was measured in 53 pediatric infratentorial ependymomas using a real-time quantitative PCR.

Results

Three miRNAs were shown to efficiently differentiate between grade II and III ependymomas: miR-17-5p, miR-19a-3p, and miR-106b-5p. Survival analysis showed that the probabilities of overall (p = 0.036) and event-free survival (p = 0.002) were reduced with higher than median miRNA expression levels of miR-17-5p. Using multivariate analysis adjusted for patient's age, sex, tumor grade and localization, we showed statistically significant associations with event-free survival (p = 0004) and borderline statistical significance with overall survival (p = 0.057) for miR-17-5p. Correlation analysis of miR-19a, miR-17-5p, miR-106b revealed that their expression levels were significantly correlated with EZH2 expression, suggested marker of PFA ependymomas. Furthermore, lower expression level of LAMA2 mRNA was shown to be associated with an increased risk of death in covariate-adjusted analyses.

Conclusions

Our data provide a better understanding of pediatric ependymoma and suggests the presence of plausible molecular biomarkers connected with the outcome.

Heterochronic microRNAs in temporal specification of neural stem cells: application toward rejuvenation

Plasticity is a critical factor enabling stem cells to contribute to the development and regeneration of tissues. In the mammalian central nervous system (CNS), neural stem cells (NSCs) that are defined by their capability for self-renewal and differentiation into neurons and glia, are present in the ventricular neuroaxis throughout life. However, the differentiation potential of NSCs changes in a spatiotemporally regulated manner and these cells progressively lose plasticity during development. One of the major alterations in this process is the switch from neurogenesis to gliogenesis. NSCs initiate neurogenesis immediately after neural tube closure and then turn to gliogenesis from midgestation, which requires an irreversible competence transition that enforces a progressive reduction of neuropotency. A growing body of evidence indicates that the neurogenesis-to-gliogenesis transition is governed by multiple layers of regulatory networks consisting of multiple factors, including epigenetic regulators, transcription factors, and non-coding RNA (ncRNA). In this review, we focus on critical roles of microRNAs (miRNAs), a class of small ncRNA that regulate gene expression at the post-transcriptional level, in the regulation of the switch from neurogenesis to gliogenesis in NSCs in the developing CNS. Unraveling the regulatory interactions of miRNAs and target genes will provide insights into the regulation of plasticity of NSCs, and the development of new strategies for the regeneration of damaged CNS.

MicroRNA-29A/PTEN pathway modulates neurite outgrowth in PC12 cells

PTEN serves as an intrinsic brake on neurite outgrowth, but the regulatory mechanism that governs its action is not clear. In the present study, miR-29a was found to increase neurite outgrowth by decreasing PTEN expression. Results showed that miR-92a-1, miR-29a, miR-92b, and miR-29c expression levels increased during nerve growth factor (NGF)-induced differentiation of PC12 cells. Based on in silico analysis of possible miR-29a targets, PTEN mRNA may be a binding site for miR-29a. A protein expression assay and luciferase reporter assay showed that miR-29a could directly target the 3'-UTRs (untranslated regions) of PTEN mRNA and down-regulate the expression of PTEN. PC12 cells infected with lentiviral pLKO-miR-29a showed far higher levels of miR-29a and Akt phosphorylation level than those infected with control. This promoted neurite outgrowth of PC12 cells. Collectively, these results indicate that miR-29a is an important regulator of neurite outgrowth via targeting PTEN and that it may be a promising therapeutic target for neural disease.

Functions of the bone morphogenetic protein signaling pathway through microRNAs (review)

MicroRNAs (miRNAs or miRs) have emerged as key regulators of gene expression in essential cellular processes, such as cell growth, differentiation and development. Recent findings have established that the levels of miRNAs are modulated by cell signaling mechanisms, including the bone morphogenetic protein (BMP) signaling pathway. The BMP signaling pathway controls diverse cellular activities by modulating the levels of miRNAs, indicating the complexity of gene regulation by the BMP signaling pathway. The tight regulation of the levels of miRNAs is critical for maintaining normal physiological conditions, and dysregulated miRNA levels contribute to the development of diseases. In the present review, we discuss different insights (provided over the past decade) into the regulation of miRNAs governed by the BMP signaling pathway and the implications of this regulation on the understanding of the cellular differentiation of vascular smooth muscle cells (VSMCs), osteoblasts and neuronal cells.

MicroRNAs: Small molecules with big roles in neurodevelopment and diseases

MicroRNAs (miRNAs) are single-stranded, non-coding RNA molecules that play important roles in the development and functions of the brain. Extensive studies have revealed critical roles for miRNAs in brain development and function. Dysregulation or altered expression of miRNAs is associated with abnormal brain development and pathogenesis of neurodevelopmental diseases. This review serves to highlight the versatile roles of these small RNA molecules in normal brain development and their association with neurodevelopmental disorders, in particular, two closely related neuropsychiatric disorders of neurodevelopmental origin, schizophrenia and bipolar disorder.

The Silencing Effect of microRNA miR-17 on p21 Maintains the Neural Progenitor Pool in the Developing Cerebral Cortex

Expansion of the neural progenitor pool in the developing cerebral cortex is crucial for controlling brain size, since proliferation defects have been associated with the pathogenesis of microcephaly in humans. Cell cycle regulators play important roles in proliferation of neural progenitors. Here, we show that the cyclin-dependent kinase inhibitor p21 (also called Cdkn1a and Cip1) negatively regulates proliferation of radial glial cells (RGCs) and intermediate progenitors (IPs) in the embryonic mouse cortex. MicroRNA-17 (miR-17) displays reciprocal expressions with p21 in the developing cortex. Opposite to p21, miR-17 promotes expansion of RGCs and IPs, as demonstrated by overexpressing miR-17 precursors and miR-17 sponges that can knock down the endogenous miR-17. Moreover, p21 is a putative target normally silenced by miR-17. Co-expression of miR-17 with p21 is sufficient to rescue the negative regulation of p21 on progenitor proliferation. Our results indicate a mechanism of controlling the neural progenitor pool, which is to suppress p21 by miR-17 in the developing cortex.