MicroRNA-130b targets Fmr1 and regulates embryonic neural progenitor cell proliferation and differentiation

Fmr1 exon 14 skipping in late embryonic development of the rat forebrain

BACKGROUND

Fragile X syndrome, the major cause of inherited intellectual disability among men, is due to deficiency of the synaptic functional regulator FMR1 protein (FMRP), encoded by the FMRP translational regulator 1 (FMR1) gene. FMR1 alternative splicing produces distinct transcripts that may consequently impact FMRP functional roles. In transcripts without exon 14 the translational reading frame is shifted. For deepening current knowledge of the differential expression of Fmr1 exon 14 along the rat nervous system development, we conducted a descriptive study employing quantitative RT-PCR and BLAST of RNA-Seq datasets.

RESULTS

We observed in the rat forebrain progressive decline of total Fmr1 mRNA from E11 to P112 albeit an elevation on P3; and exon-14 skipping in E17-E20 with downregulation of the resulting mRNA. We tested if the reduced detection of messages without exon 14 could be explained by nonsense-mediated mRNA decay (NMD) vulnerability, but knocking down UPF1, a major component of this pathway, did not increase their quantities. Conversely, it significantly decreased FMR1 mRNA having exon 13 joined with either exon 14 or exon 15 site A.

CONCLUSIONS

The forebrain in the third embryonic week of the rat development is a period with significant skipping of Fmr1 exon 14. This alternative splicing event chronologically precedes a reduction of total Fmr1 mRNA, suggesting that it may be part of combinatorial mechanisms downregulating the gene's expression in the late embryonic period. The decay of FMR1 mRNA without exon 14 should be mediated by a pathway different from NMD. Finally, we provide evidence of FMR1 mRNA stabilization by UPF1, likely depending on FMRP.

Transcriptome sequencing reveals Gastrodia elata Blume could increase the cell viability of eNPCs under hypoxic condition by improving DNA damage repair ability

ETHNOPHARMACOLOGICAL RELEVANCE

Gastrodia elata Blume (GEB), known as Tianma in China, is a traditional medicinal herb that has been reported to have various pharmacological effects and neuroprotection, has long been used for treating dizziness, epilepsy, stroke. However, explanation of its underlying mechanisms remains a great challenge.

AIM OF THE STUDY

The neuroprotective mechanism of GEB on hypoxia-induced neuronal injury in cultured mouse embryonic neural progenitor cells (eNPCs) was investigated, with emphasis on the eNPCs proliferation and DNA damage repair.

MATERIALS AND METHODS

In this study, hypoxia was focused, which may be caused by stroke or acute cerebral ischemia and is considered as one of the important factors contributing to the Central Nervous System diseases. CoCl₂ was adopted to construct a hypoxic/ischemic condition in eNPCs. eNPCs proliferation analysis validated GEB neuroprotective effect under hypoxic/ischemic condition. Transcriptome and weighted gene co-expression network analysis (WGCNA) screened the special gene-network module correlated with what appeared to have significant positive correlation with GEB. Then, Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were performed to explore the biological functions of selected genes in the modules that had high correlation with GEB.

RESULTS

GEB has neuroprotective effect and could rescue eNPCs proliferation under hypoxic/ischemic condition induced by CoCl₂. Transcriptome and WGCNA unveil the neuroprotective mechanism of GEB on improving DNA damage repair ability by increasing the expression of genes associated with DNA repair and replication. Western blotting and qPCR showed that GEB could improve DNA damage repair ability by increasing the expression of Mcm2, Mcm6, Pold2, Pole, Pole2, Rfc1, Pole4, Dna2 and Rpa2, which were associated with DNA damage and replication.

CONCLUSION

Through transcriptome and WGCNA, this study unveiled Gastrodia elata Blume could increase the cell viability of eNPCs under hypoxic condition by improving DNA damage repair ability.

Transcriptional factor FoxM1-activated microRNA-335-3p maintains the self-renewal of neural stem cells by inhibiting p53 signaling pathway via Fmr1

Background

New mechanistic insights into the self-renewal ability and multipotent properties of neural stem cells (NSCs) are currently under active investigation for potential use in the treatment of neurological diseases. In this study, NSCs were isolated from the forebrain of fetal rats and cultured to induce NSC differentiation, which was associated with low expression of the non-coding RNA microRNA-335-3p (miR-335-3p).

Methods

Loss- and gain-of-function experiments were performed in NSCs after induction of differentiation.

Results

Overexpression of miR-335-3p or FoxM1 and inhibition of the Fmr1 or p53 signaling pathways facilitated neurosphere formation, enhanced proliferation and cell cycle entry of NSCs, but restricted NSC differentiation. Mechanistically, FoxM1 positively regulated miR-335-3p by binding to its promoter region, while miR-335-3p targeted and negatively regulated Fmr1. Additionally, the promotive effect of miR-335-3p on NSC self-renewal occurred via p53 signaling pathway inactivation.

Conclusion

Taken together, miR-335-3p activated by FoxM1 could suppress NSC differentiation and promote NSC self-renewal by inactivating the p53 signaling pathway via Fmr1.

miRNA expression and interaction with the 3'UTR of FMR1 in FRAXopathy pathogenesis

FRAXopathies are caused by the expansion of the CGG repeat in the 5'UTR of the FMR1 gene, which encodes the protein responsible for the synthesis of FMRP. This mutation leads to dramatic changes in FMRP expression at both the mRNA and protein levels. Evidence is emerging that changes in FMR1 mRNA expression can lead to the dysregulation of the miRNAs that target its 3'UTR. In the present work, B-lymphocyte cell lines obtained from patients with FRAXopathies were used, and a wide variety of FMR1 gene activities were observed, allowing the identification of the relationships between FMR1 dysregulation and miRNA activity. We studied the expression levels of eight miRNAs that target the FMR1 gene. To prove the interaction of the studied miRNAs with FMR1, a plasmid was constructed that possesses three primary structures: the miRNA gene, with expression driven by an inducible promoter; a constitutively expressed FusionRed reporter; and an eGFP reporter followed by the 3'UTR of the FMR1 gene. We evaluated changes in miRNA expression in response to alterations in FMR1 gene activity in a model cell line as well as interactions with some miRNAs with the FMR1 3'UTR.

Prognostic values of microRNA-130 family expression in patients with cancer: a meta-analysis and database test

BACKGROUND

Emerging evidence shows that microRNA-130 (miRNA-130) family may be useful as prognostic biomarkers in cancer. However, there is no confirmation in an independent validation study. The aim of this study was to summarize the prognostic value of miRNA-130 family (miRNA-130a and miRNA-130b) for survival in patients with cancer.

METHODS

The pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to estimate the association strength between miRNA-130 family expression and prognosis. Kaplan-Meier plotters were used to verify the miRNA-130b expression and overall survival (OS).

RESULTS

A total of 2141 patients with OS and 1159 patients with disease-free survival (DFS)/progression-free survival (PFS) were analyzed in evidence synthesis. For the miRNA-130a, the overall pooled effect size (HR) was HR 1.58 (95% CI: 1.21-2.06, P < 0.001). Tissue and serum expression of miRNA-130a was significantly associated with the OS (HR = 1.54, 95% CI: 1.11-2.14, P = 0.009; HR = 1.65, 95% CI: 1.14-2.38, P = 0.008), and in gastric cancer (HR = 1.81, 95% CI: 1.34-2.45, P < 0.001). For the miRNA-13b, a statistical correlation was observed between high miRNA-130b expression and poor OS in patients with cancer (HR = 1.95, 95% CI: 1.47-2.59, P < 0.001), especially in tissue sample (HR = 2.01, 95% CI: 1.39-2.91, P < 0.001), Asian (HR = 2.55, 95% Cl: 1.77-3.69, P < 0.001) and hepatocellular carcinoma (HR = 1.87, 95% CI: 1.23-2.85, P = 0.004). The expression of miRNA-130b was significantly correlated with DFS/PFS (HR = 1.53, 95% CI: 1.31-1.77, P < 0.001), in tissue (HR = 1.98, 95% CI: 1.50-2.62, P < 0.001) and serum (HR = 1.37, 95% CI: 1.15-1.64, P < 0.001), especially in HCC (HR = 1.98, 95% CI: 1.50, 2.62, P < 0.001). In database test, a significant correlation between high miRNA-130b expression and poor OS for HCC patients was observed (HR = 1.55, 95% CI: 1.01, 2.35, P = 0.0045).

CONCLUSION

The high expression of miRNA-130 family might predict poor prognosis in cancer patients. Prospectively, combining miRNA-130a and miRNA-130b may be considered as powerful prognostic predictor for clinical application.

mRNA and miRNA expression profiles in an ectoderm-biased substate of human pluripotent stem cells

The potential applications of human pluripotent stem cells, embryonic stem (ES) cells, and induced pluripotent stem (iPS) cells in cell therapy and regenerative medicine have been widely studied. The precise definition of pluripotent stem cell status during culture using biomarkers is essential for basic research and regenerative medicine. Culture conditions, including extracellular matrices, influence the balance between self-renewal and differentiation. Accordingly, to explore biomarkers for defining and monitoring the pluripotent substates during culture, we established different substates in H9 human ES cells by changing the extracellular matrix from vitronectin to Matrigel. The substate was characterised by low and high expression of the pluripotency marker R-10G epitope and the mesenchymal marker vimentin, respectively. Immunohistochemistry, induction of the three germ layers, and exhaustive expression analysis showed that the substate was ectoderm-biased, tended to differentiate into nerves, but retained the potential to differentiate into the three germ layers. Further integrated analyses of mRNA and miRNA microarrays and qPCR analysis showed that nine genes (COL9A2, DGKI, GBX2, KIF26B, MARCH1, PLXNA4, SLC24A4, TLR4, and ZHX3) were upregulated in the ectoderm-biased cells as ectoderm-biased biomarker candidates in pluripotent stem cells. Our findings provide important insights into ectoderm-biased substates of human pluripotent stem cells in the fields of basic research and regenerative medicine.

MicroRNA-129 modulates neuronal migration by targeting Fmr1 in the developing mouse cortex

During cortical development, neuronal migration is one of the most important steps for normal cortical formation and function, and defects in this process cause many brain diseases. However, the molecular mechanisms underlying this process remain largely unknown. In this study, we found that miR-129-5p and miR-129-3p were expressed in both neural progenitor cells and cortical neurons in the developing murine cortex. Moreover, abnormal miR-129 expression could block radial migration of both the deeper layer and upper layer neurons, and impair the multipolar to bipolar transition. However, antagomir-mediated inhibition resulted in overmigration of neurons. In addition, we showed that Fragile X Mental Retardation gene 1 (Fmr1), which is mutated in the autism spectrum disorder fragile X syndrome, is an important regulatory target for miR-129-5p. Furthermore, Fmr1 loss-of-function and gain-of-function experiments showed opposite effects on miR-129 regulation of neuronal migration, and restoring Fmr1 expression could counteract the deleterious effect of miR-129 on neuronal migration. Taken together, our results suggest that miR-129-5p could modulate the expression of fragile X mental retardation 1 protein (FMRP) to ensure normal neuron positioning in the developing cerebral cortex.

Non-coding RNA in Fragile X Syndrome and Converging Mechanisms Shared by Related Disorders

Fragile X syndrome (FXS) is one of the most common forms of hereditary intellectual disability. It is also a well-known monogenic cause of autism spectrum disorders (ASD). Repetitive trinucleotide expansion of CGG repeats in the 5'-UTR of FMR1 is the pathological mutation. Full mutation CGG repeats epigenetically silence FMR1 and thus lead to the absence of its product, fragile mental retardation protein (FMRP), which is an indispensable translational regulator at synapsis. Loss of FMRP causes abnormal neural morphology, dysregulated protein translation, and distorted synaptic plasticity, giving rise to FXS phenotypes. Non-coding RNAs, including siRNA, miRNA, and lncRNA, are transcribed from DNA but not meant for protein translation. They are not junk sequence but play indispensable roles in diverse cellular processes. FXS is the first neurological disorder being linked to miRNA pathway dysfunction. Since then, insightful knowledge has been gained in this field. In this review, we mainly focus on how non-coding RNAs, especially the siRNAs, miRNAs, and lncRNAs, are involved in FXS pathogenesis. We would also like to discuss several potential mechanisms mediated by non-coding RNAs that may be shared by FXS and other related disorders.

Maternal and umbilical cord serum-derived exosomes enhance endothelial cell proliferation and migration

We investigated the role of exosomes derived from maternal and umbilical cord blood in the regulation of angiogenesis. We report here that both maternal exosomes (MEs) and umbilical exosomes (UEs) significantly enhance HUVEC proliferation, migration, and tube formation. Importantly, ME-treated HUVECs (MEXs) displayed significantly increased migration, but not proliferation or tube formation, compared with UE-treated HUVECs (UEXs). We found that the expression of a subset of migration-related microRNAs (miRNAs), including miR-210-3p, miR-376c-3p, miR-151a-5p, miR-296-5p, miR-122-5p, and miR-550a-5p, among others, were significantly increased or decreased in UEs, and this altered expression was likely correlated with the differential regulation of HUVEC migration. We also found that the mRNA expression of hepatocyte growth factor (HGF) was up-regulated in MEXs and UEXs and, moreover, that inhibiting HGF partially abolished the enhanced cell migration induced by UEs. Our results suggest that both MEs and UEs greatly enhanced endothelial cell (EC) functions and differentially regulated EC migration, which was mostly attributed to the different expression profiles of exosomal miRNA. These findings highlight the importance of exosomes in the regulation of angiogenesis during pregnancy. Exosomal miRNAs, in particular, may be of great significance for the regulation of angiogenesis in maintaining normal pregnancy.-Jia, L., Zhou, X., Huang, X., Xu, X., Jia, Y., Wu, Y., Yao, J., Wu, Y., Wang, K. Maternal and umbilical cord serum-derived exosomes enhance endothelial cell proliferation and migration.

Foxm1 controls a pro-stemness microRNA network in neural stem cells

Cerebellar neural stem cells (NSCs) require Hedgehog-Gli (Hh-Gli) signalling for their maintenance and Nanog expression for their self-renewal. To identify novel molecular features of this regulatory pathway, we used next-generation sequencing technology to profile mRNA and microRNA expression in cerebellar NSCs, before and after induced differentiation (Diff-NSCs). Genes with higher transcript levels in NSCs (vs. Diff-NSCs) included Foxm1, which proved to be directly regulated by Gli and Nanog. Foxm1 in turn regulated several microRNAs that were overexpressed in NSCs: miR-130b, miR-301a, and members of the miR-15~16 and miR-17~92 clusters and whose knockdown significantly impaired the neurosphere formation ability. Our results reveal a novel Hh-Gli-Nanog-driven Foxm1-microRNA network that controls the self-renewal capacity of NSCs.

miR-130b regulates the proliferation, invasion and apoptosis of glioma cells via targeting of CYLD

MicroRNAs are short non-coding RNAs that play important roles in gliomas. However, the role of miR-130b in glioma remains unclear. In the present study, miR-130b expression was upregulated in glioma tissues and cell lines. Kaplan-Meier analysis indicated that the upregulation of miR-130b expression correlated with poor prognoses in glioma patients. Multivariate analysis demonstrated that this upregulation and a high-grade classification were independent factors that both predicted poor outcomes for glioma patients. Dual-luciferase assays identified that the cylindromatosis (CYLD) gene is a direct target of miR-130b. Functional studies demonstrated that a miR-130b mimic significantly promoted the growth and invasion of glioma cells, while also inhibiting apoptosis via selective targeting of CYLD, which was enhanced by CYLD-targeted siRNA. In contrast, a miR‑130b inhibitor suppressed these biological behaviors, and this inhibition was reversed by CYLD-targeted siRNA. These data revealed that miR-130b could act as a novel potential diagnostic biomarker for glioma, while also demonstrating the importance of miR‑130b in the cell proliferation and progression of glioma, indicating that it may serve as a useful therapeutic target for glioma.

MicroRNA-130b transcriptionally regulated by histone H3 deacetylation renders Akt ubiquitination and apoptosis resistance to 6-OHDA

Apoptosis of DA neurons is a contributing cause of disability and death for Parkinson's disease (PD). Akt may become a potential therapeutic target for PD since Akt has been deactivated during DA neuron apoptosis. We previously demonstrated that Akt confers apoptosis resistance against 6-OHDA in DA neuron-like PC12 cells, yet the underlying mechanisms accounted for this are not fully understood. Here we report that microRNA-130b (miR-130b)-dependent and cylindromatosis (CYLD) repression-mediated Akt ubiquitination renders apoptosis resistance of PC12 cells to 6-OHDA, which elicits histone H3 deacetylation-induced transcriptional downregulation of miR-130b vice versa. CYLD deficiency ubiquitinates Akt at Lys63, thereby phosphorylating Akt and antagonizing 6-OHDA-initiated apoptosis. MiR-130b targetedly represses CYLD and increases apoptosis resistance to 6-OHDA. CYLD repression by miR-130b restores Akt ubiquitination and activation, GSK3β and FoxO3a phosphorylation, FoxO3a removal from Bim promoter as well as Bim downregulation during 6-OHDA administration. CYLD deficiency-mediated Akt activation is instrumental for the apoptosis-resistant phenotypes of miR-130b. In addition, 6-OHDA transcriptionally downregulates miR-130b through recruitment of HDAC3 at the promoter. Furthermore, EPO potentiates the ability of miR-130b to activate Akt and augment apoptosis resistance. Our findings identify the apoptosis-resistant function of miR-130b and suggest that histone H3 deacetylation plays a pivotal role in regulating miR-130b transcription in response to 6-OHDA.

MicroRNA-130b promotes cell migration and invasion by inhibiting peroxisome proliferator-activated receptor-γ in human glioma

Glioma is the most common and aggressive type of primary brain tumor. MicroRNA (miR)-130b functions as a tumor-associated miR. The dysregulation of miR-130b is involved in numerous biological characteristics and properties of certain types of cancer. The present study revealed the function and possible molecular mechanism of miR-130b in glioma cells, reporting that the level of miR-130b was markedly higher, increasing progressively as the histologic grade of the glioma increased, compared with the level in normal tissues. Additionally, the present study demonstrated that patients with high miR-130b expression exhibited a poor 3-year survival rate and miR-130b was an independent factor for predicting the prognosis of patients with glioma. The downregulation of miR-130b reduced invasion and migration in U373 and U87 cells. Furthermore, the downregulation of miR-130b increased peroxisome proliferator-activated receptor-γ (PPARγ) expression and inhibited epithelial-mesenchymal transition (EMT) in glioma cells. The present study identified PPARγ as a direct target of miR-130b in glioma in vitro. Furthermore, PPARγ knockdown was revealed to reduce the effect on EMT caused by the downregulation of miR-130b in U87 cells. The present study demonstrated that miR-130b promotes glioma proliferation, migration and invasion by suppressing PPARγ and subsequently inducing EMT.

H/ACA Box Small Nucleolar RNA 7A Promotes the Self-Renewal of Human Umbilical Cord Mesenchymal Stem Cells

Human umbilical cord blood derived mesenchymal stem cells (uMSC) are pluripotent cells that have been now considered as a promising candidate for various cell-based therapies. However, their limited in vitro proliferation ability and the gradual loss of pluripotency set barricades for further usages. Emerging evidence suggests that small nucleolar RNAs (snoRNA) are actively involved in cell proliferation especially in tumor cells, but their roles in stem cells are largely unknown. In this study, we demonstrated that H/ACA box small nucleolar RNA 7A (SNORA7A) is inversely correlated to the decreased proliferation rate during in vitro passaging of uMSC. Further investigations indicate that SNORA7A overexpression can promote uMSC proliferation and self-renewal. The inhibition of SNORA7A using antisense oligonucleotides significantly reduces the expression and the binding of SNORA7A to DKC1, core protein that essential to form small nucleolar ribonucleo-particles (snoRNP) complex and catalyze pseudouridines in 28S RNA. And the inhibition also significantly suppresses uMSC proliferation and self-renewal. Moreover, overexpression of SNORA7A transcripts with mutations of binding regions for snoRNP core proteins and 28S RNA did not induce proliferation and self-renewal. Besides, SNORA7A also suppresses both the osteogenic and adipogenic differentiation, strengthening its self-renewal maintaining roles in uMSC. Taken together, our study for the first time showed that H/ACA box snoRNAs are actively involved in MSC proliferation as well as pluripotency control, and we identify SNORA7A as one of the critical snoRNAs that regulate the proliferation and self-renewal of uMSC through snoRNP recruiting. Stem Cells 2017;35:222-235.

MicroRNAs: Not "Fine-Tuners" but Key Regulators of Neuronal Development and Function

MicroRNAs (miRNAs) are a class of short non-coding RNAs that operate as prominent post-transcriptional regulators of eukaryotic gene expression. miRNAs are abundantly expressed in the brain of most animals and exert diverse roles. The anatomical and functional complexity of the brain requires the precise coordination of multilayered gene regulatory networks. The flexibility, speed, and reversibility of miRNA function provide precise temporal and spatial gene regulatory capabilities that are crucial for the correct functioning of the brain. Studies have shown that the underlying molecular mechanisms controlled by miRNAs in the nervous systems of invertebrate and vertebrate models are remarkably conserved in humans. We endeavor to provide insight into the roles of miRNAs in the nervous systems of these model organisms and discuss how such information may be used to inform regarding diseases of the human brain.

A 3' untranslated region variant in FMR1 eliminates neuronal activity-dependent translation of FMRP by disrupting binding of the RNA-binding protein HuR

Fragile X syndrome is a common cause of intellectual disability and autism spectrum disorder. The gene underlying the disorder, fragile X mental retardation 1 (FMR1), is silenced in most cases by a CGG-repeat expansion mutation in the 5' untranslated region (UTR). Recently, we identified a variant located in the 3'UTR of FMR1 enriched among developmentally delayed males with normal repeat lengths. A patient-derived cell line revealed reduced levels of endogenous fragile X mental retardation protein (FMRP), and a reporter containing a patient 3'UTR caused a decrease in expression. A control reporter expressed in cultured mouse cortical neurons showed an expected increase following synaptic stimulation that was absent when expressing the patient reporter, suggesting an impaired response to neuronal activity. Mobility-shift assays using a control RNA detected an RNA-protein interaction that is lost with the patient RNA, and HuR was subsequently identified as an associated protein. Cross-linking immunoprecipitation experiments identified the locus as an in vivo target of HuR, supporting our in vitro findings. These data suggest that the disrupted interaction of HuR impairs activity-dependent translation of FMRP, which may hinder synaptic plasticity in a clinically significant fashion.

Epigenetics, microRNA, and addiction

Drug addiction is characterized by uncontrolled drug consumption and high rates of relapse to drug taking during periods of attempted abstinence. Addiction is now largely considered a disorder of experience-dependent neuroplasticity, driven by remodeling of synapses in reward and motivation relevant brain circuits in response to a history of prolonged drug intake. Alterations in gene expression play a central role in addiction-relevant neuroplasticity, but the mechanisms by which additive drugs remodel brain motivation circuits remains unclear. MicroRNAs (miRNAs) are a class of noncoding RNA that can regulate the expression of large numbers of protein-coding mRNA transcripts by binding to the 3' untranslated region (3' UTR) of target transcripts and blocking their translation into the encoded protein or triggering their destabilization and degradation. Emerging evidence has implicated miRNAs in regulating addiction-relevant neuroplasticity in the brain, and in controlling the motivational properties of cocaine and other drugs of abuse. Here, the role for miRNAs in regulating basic aspects of neuronal function is reviewed. The involvement of miRNAs in controlling the motivational properties of addictive drugs is also summarized. Finally, mechanisms by which miRNAs exert their actions on drug intake, when known, are considered.

A molecular model for neurodevelopmental disorders

Genes implicated in neurodevelopmental disorders (NDDs) important in cognition and behavior may have convergent function and several cellular pathways have been implicated, including protein translational control, chromatin modification, and synapse assembly and maintenance. Here, we test the convergent effects of methyl-CpG binding domain 5 (MBD5) and special AT-rich binding protein 2 (SATB2) reduced dosage in human neural stem cells (NSCs), two genes implicated in 2q23.1 and 2q33.1 deletion syndromes, respectively, to develop a generalized model for NDDs. We used short hairpin RNA stably incorporated into healthy neural stem cells to supress MBD5 and SATB2 expression, and massively parallel RNA sequencing, DNA methylation sequencing and microRNA arrays to test the hypothesis that a primary etiology of NDDs is the disruption of the balance of NSC proliferation and differentiation. We show that reduced dosage of either gene leads to significant overlap of gene-expression patterns, microRNA patterns and DNA methylation states with control NSCs in a differentiating state, suggesting that a unifying feature of 2q23.1 and 2q33.1 deletion syndrome may be a lack of regulation between proliferation and differentiation in NSCs, as we observed previously for TCF4 and EHMT1 suppression following a similar experimental paradigm. We propose a model of NDDs whereby the balance of NSC proliferation and differentiation is affected, but where the molecules that drive this effect are largely specific to disease-causing genetic variation. NDDs are diverse, complex and unique, but the optimal balance of factors that determine when and where neural stem cells differentiate may be a major feature underlying the diverse phenotypic spectrum of NDDs.

Computational identification and experimental validation of microRNAs binding to the fragile X syndrome gene Fmr1

MicroRNAs (miRNAs) usually bind to their target mRNAs through imperfect base pairing in the 3'-untranslated regions (3' UTRs) and regulate target gene expression via post-transcriptional suppression. In recent years, computational approaches to predict miRNA targets have facilitated the identification of potential target sites. In this study, we used three programs TargetScan, miRDB and miRanda to predict potential miRNA binding sites to the fragile X gene Fmr1 and picked out 61 miRNAs which were predicted by all three programs for further investigation. Excitingly, 5 out of these miRNAs, miR-23a, miR-32, miR-124, miR-335-5p and miR-350, were experimentally verified by luciferase reporter assays. Furthermore, overexpression of miR-124 in mouse embryonic neural progenitor cells (eNPC) could not only significantly reduce Fmr1 level, but also increase Cdk4 and cyclin D1 levels which coincidently promoted eNPC proliferation. Our results imply that miR-124 plays an important role in the proliferation of mouse embryonic stem cells by promoting Cdk4 and cyclin D1 expression through directly inhibiting Fmr1 expression.

Biomarker development for C9orf72 repeat expansion in ALS

The expanded GGGGCC hexanucleotide repeat in the non-coding region of the C9orf72 gene on chromosome 9p21 has been discovered as the cause of approximately 20-50% of familial and up to 5-20% of sporadic amyotrophic lateral sclerosis (ALS) cases, making this the most common known genetic mutation of ALS to date. At the same time, it represents the most common genetic mutation in frontotemporal dementia (FTD; 10-30%). Because of the high prevalence of mutant C9orf72, pre-clinical efforts in identifying therapeutic targets and developing novel therapeutics for this mutation are highly pursued in the hope of providing a desperately needed disease-modifying treatment for ALS patients, as well as other patient populations affected by the C9orf72 mutation. The current lack of effective treatments for ALS is partially due to the lack of appropriate biomarkers that aide in assessing drug efficacy during clinical trials independent of clinical outcome measures, such as increased survival. In this review we will summarize the opportunities for biomarker development specifically targeted to the newly discovered C9orf72 repeat expansion. While drugs are being developed for this mutation, it will be crucial to provide a reliable biomarker to accompany the clinical development of these novel therapeutic interventions to maximize the chances of a successful clinical trial. This article is part of a Special Issue entitled ALS complex pathogenesis.

miR-21 induces myofibroblast differentiation and promotes the malignant progression of breast phyllodes tumors

Phyllodes tumors of breast, even histologically diagnosed as benign, can recur locally and have metastatic potential. Histologic markers only have limited value in predicting the clinical behavior of phyllodes tumors. It remains unknown what drives the malignant progression of phyllodes tumors. We found that the expression of myofibroblast markers, α-smooth muscle actin (α-SMA), fibroblast activation protein (FAP), and stromal cell-derived factor-1 (SDF-1), is progressively increased in the malignant progression of phyllodes tumors. Microarray showed that miR-21 was one of the most significantly upregulated microRNAs in malignant phyllodes tumors compared with benign phyllodes tumors. In addition, increased miR-21 expression was primarily localized to α-SMA-positive myofibroblasts. More importantly, α-SMA and miR-21 are independent predictors of recurrence and metastasis, with their predictive value of recurrence better than histologic grading. Furthermore, miR-21 mimics promoted, whereas miR-21 antisense oligos inhibited, the expression of α-SMA, FAP, and SDF-1, as well as the proliferation and invasion of primary stromal cells of phyllodes tumors. The ability of miR-21 to induce myofibroblast differentiation was mediated by its regulation on Smad7 and PTEN, which regulate the migration and proliferation, respectively. In breast phyllodes tumor xenografts, miR-21 accelerated tumor growth, induced myofibroblast differentiation, and promoted metastasis. This study suggests an important role of myofibroblast differentiation in the malignant progression of phyllodes tumors that is driven by increased miR-21.