MicroRNA-9 is a ponderable index for the prognosis of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common primary malignant tumors of the liver worldwide; however, despite its significance, there is a lack of treatment methods and clear prognoses. MicroRNA-9 (miR-9) is known to play an important role in tumor tumorigenesis and progression. Talin-1, which plays a significant role in regulating the transmutation of carcinoma, has been demonstrated to be downregulated by miR-9 in epithelial ovarian cancer. In the present study, we researched the potential role of miR-9 in the prognosis of HCC. The expression levels of miR-9 and Talin-1 mRNA in HCC tissues (n = 60), adjacent non-cancerous tissues (n = 60), and normal liver tissues (n = 20) were detected using a real-time quantitative assay; protein expression levels of Talin-1 were detected using western blot. The expression levels of miR-9 were significantly higher in HCC tissues (P < 0.001) than in normal liver and adjacent non-cancerous tissues. These levels were significantly associated with tumor grade, tumor size, portal vein tumor thrombus, integral capsule, and 2.0-year disease-free survival rate (P < 0.05). High levels of miR-9 were strongly associated with the malignant progression of HCC, and overexpression of miR-9 is a risk factor that has a statistically significant effect on survival rate. miR-9 could play a role as an HCC tumor activator by regulating the expression of Talin-1; therefore, miR-9 might be a potentially valuable biomarker for the prognosis in HCC patients.

BRAF activated non-coding RNA (BANCR) promoting gastric cancer cells proliferation via regulation of NF-κB1

BACKGROUND AND OBJECTIVE

Long non-coding RNA, BANCR, has been demonstrated to contribute to the proliferation and migration of tumors. However, its molecular mechanism underlying gastric cancer is still unknown. In present study, we investigated whether BANCR was involved in the development of gastric cancer cells via regulation of NF-κB1.

METHODS

Human gastric cancer tissues were isolated as well as human gastric cell lines MGC803 and BGC823 were cultured to investigate the role of BANCR in gastric cancer.

RESULTS

BANCR expression was significantly up-regulated in gastric tumor tissues and gastric cell lines. Down-regulation of BANCR inhibited gastric cancer cell growth and promoted cell apoptosis, and it also contributed to a significant decrease of NF-κB1 (P50/105) expression and 3'UTR of NF-κB1 activity. Overexpression of NF-κB1 reversed the effect of BANCR on cancer cell growth and apoptosis. MiroRNA-9 (miR-9) targeted NF-κB1, and miR-9 inhibitor also reversed the effects of BANCR on gastric cancer cell growth and apoptosis.

CONCLUSION

BANCR was highly expressed both in gastric tumor tissues and in cancer cells. NF-κB1 and miR-9 were involved in the role of BANCR in gastric cancer cell growth and apoptosis.

Neural fate decisions mediated by combinatorial regulation of Hes1 and miR-9

In the nervous system, Hes1 shows an oscillatory manner in neural progenitors but a persistent one in neurons. Many models involving Hes1 have been provided for the study of neural differentiation but few of them take the role of microRNA into account. It is known that a microRNA, miR-9, plays crucial roles in modulating Hes1 oscillations. However, the roles of miR-9 in controlling Hes1 oscillations and inducing transition between different cell fates still need to be further explored. Here we provide a mathematical model to show the interaction between miR-9 and Hes1, with the aim of understanding how the Hes1 oscillations are produced, how they are controlled, and further, how they are terminated. Based on the experimental findings, the model demonstrates the essential roles of Hes1 and miR-9 in regulating the dynamics of the system. In particular, the model suggests that the balance between miR-9 and Hes1 plays important roles in the choice between progenitor maintenance and neural differentiation. In addition, the synergistic (or antagonistic) effects of several important regulations are investigated so as to elucidate the effects of combinatorial regulation in neural decision-making. Our model provides a qualitative mechanism for understanding the process in neural fate decisions regulated by Hes1 and miR-9.

miR-9 promotes cell proliferation and inhibits apoptosis by targeting LASS2 in bladder cancer

MicroRNA-9 upregulation was reported in several tumors. However, its function and mechanism in human bladder cancer remains obscure. The present study aims to identify the expression pattern, biological roles and potential mechanism of miR-9 in human bladder cancers. We found that expression level of miR-9 in bladder cancer tissues was higher than normal tissues. miR-9 mimic transfection was performed in T24 and 5637 cells with low miR-9 expression, and miR-9 inhibitor was employed in BIU-87 cell line with high endogenous expression. miR-9 increased cell proliferation, cell cycle progression, invasion and chemoresistance, with upregulation of cyclin D1, MMP9, Bcl-2, and survivin and downregulation of E-cadherin. Using luciferase reporter assay, we confirmed that LASS2 was a direct target of miR-9 in bladder cancer cells. Transfection of miR-9 mimic downregulated LASS2 expression. LASS2 transfection downregulated Bcl-2 and survivin expression, which were induced by miR-9 mimic in both cell lines. In conclusion, these results indicate that miR-9 upregulation might be associated with malignant phenotype of bladder cancer. miR-9 promotes chemoresistance of bladder cancer cells by target LASS2.

Regulation of UHRF1 by microRNA-9 modulates colorectal cancer cell proliferation and apoptosis

The UHRF1 protein is pivotal for DNA methylation and heterochromatin formation, leading to decreased expressions of tumor suppressor genes and contributing to tumorigenesis. However, the factors that modulate UHRF1 expression in colorectal cancer (CRC) remain unclear. Here we showed that, compared with corresponding normal tissues, UHRF1 was upregulated and microRNA-9 (miR-9) was downregulated in CRC tissues. The expression of UHRF1 was inversely correlated with overall survival rates of patients with CRC. Overexpression of miR-9 in CRC cell lines significantly attenuated CRC cell proliferation and promoted cell apoptosis. The expression of UHRF1 was markedly reduced in pre-miR-9 transfected CRC cells. Using luciferase reporter assay, we confirmed that miR-9 was a direct upstream regulator of UHRF1. Finally, analysis of miR-9 and UHRF1 levels in human CRC tissues revealed that expression of miR-9 was inversely correlated with UHRF1 expression. Collectively, our results offer in vitro validation of the concept that miR-9 could repress the expression of UHRF1, and function as a tumor-suppressive microRNA in CRC. It may serve as a prognostic and therapeutic marker for CRC.

Analyses of methylation status of CpG islands in promoters of miR-9 genes family in human gastric adenocarcinoma

In the recent years deregulation for microRNAs expression pattern have emerged as a possible molecular factor for carcinogenesis. It has been reported that the expression of miR-9 was down-regulated in human gastric adenocarcinoma. To figure out the molecular mechanism of this down regulation, the methylation status in promoters of miR-9 family loci were compared in the human gastric adenocarcinoma samples with their normal margins. Using a methylation specific PCR technique the methylation status of miR-9 family loci were compared between 30 pairs of primary human gastric adenocarcinoma samples with their normal margins. The methylation of miR 9-1 status showed no specific difference in promoter methylation pattern in tumor and normal specimens, while in the miR-9-2 locus were unmethylated in both types of tissues. The promoter of miR-9-3 locus seems to be specifically methylated in tumor and their normal margin tissues. Our data revealed methylation of these CpG islands were not meaningfully different between normal and tumor gastric adenocarcinoma specimens and the methylation status of promoter may not be able to account for alteration of miR-9 expression in this type of gastric cancer.

Temozolomide resistance and tumor recurrence: Halting the Hedgehog

Chemotherapy with Temozolomide (TMZ), radiation and surgery are the primary methods to treat Glioblastoma Multiforme (GBM), the most common adult intracranial tumor with dismal outcome. GBM resistance to therapy is the main reason of poor patient outcomes. Thus, methods to overcome the resistance are an area of extensive research. This highlight focuses on three recently published articles on the mechanism of resistance and possible therapeutic intervention, including RNA treatment with stem cells. We showed a crucial role of the developmental Sonic Hedgehog (SHH) pathway in the acquisition and maintenance of TMZ resistance. SHH signaling caused TMZ resistance in GBM cells through an increase in the multiple drug resistance gene (MDR1). The SHH receptor, Patched-1 (PTCH1), negatively regulate SHH signaling. In GBM, miR-9 suppressed PTCH1 levels, resulting in the activation of SHH pathway. Thus, SHH signaling is independent of the ligand in resistant GBM cells. MiR-9 was also increased in chemoresistance CD133+ GBM cells. A potential method to reverse resistance was tested by delivering the anti-miR in bone marrow-derived Mesenchymal Stem Cells (MSCs). The anti-miR-9 was transferred into the resistant GBM cells through exosomes and gap junctional intercellular communication. We also review on-going clinical trials with inhibitor of SHH signaling, and also discuss drug delivery by cell therapy for GBM. While GBM treatment has proven to be a challenge, there are a number of novel approaches we are currently developing to manage this malignancy.

miR-9 enhances the transactivation of nuclear factor of activated T cells by targeting KPNB1 and DYRK1B

The fast response to stimuli and subsequent activation of the nuclear factor of activated T cells (NFAT) signaling pathway play an essential role in human T cell functions. MicroRNAs (miRNAs) are increasingly implicated in regulation of numerous biological and pathological processes. In this study we demonstrate a novel function of miRNA-9 (miR-9) in regulation of the NFAT signaling pathway. Upon PMA-ionomycin stimulation, miR-9 was markedly increased, consistent with NFAT activation. Overexpression of miR-9 significantly enhanced NFAT activity and accelerated NFAT dephosphorylation and its nuclear translocation in response to PMA-ionomycin. Karyopherin-β1 (KPNB1, a nucleocytoplasmic transporter) and dual-specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B) were identified as direct targets of miR-9. Functionally, miR-9 promoted IL-2 production in stimulated human lymphocyte Jurkat T cells. Collectively, our data reveal a novel role for miR-9 in regulation of the NFAT pathway by targeting KPNB1 and DYRK1B.

MicroRNA-9 promotes tumorigenesis and mediates sensitivity to cisplatin in primary epithelial ovarian cancer cells

MicroRNAs play critical roles in regulating tumor occurrence and drug sensitivity in ovarian cancers. This study aimed to investigate the key members of MicroRNAs (miRNAs) involved in modulating tumor initiation and drug resistance in primary ovarian cancer cells. An in vitro assay based on tumor clonal formation was established to evaluate tumorigenicity and cisplatin sensitivity. By performing real-time polymerase chain reaction, we examined the expression of nine microRNAs associated with the pathology of ovarian cancers in primary ovarian tumor cells, which were surgically resected from 46 patients with distinct sensitivity to platinum-based chemotherapy. MiR-9, miR-145, and miR-429 were expressed significantly higher in drug-sensitive patients (n = 26) than in drug-resistant ones (n = 20), while higher miR-26a expression was found in resistant patients (p < 0.05). In addition, tumor cells from drug sensitive patients were more tumorigenic than those of drug resistance (p = 0.0013). Cisplatin treatment led to a sharp decrease of clonal formation of drug-sensitive cells but showed slight effects on drug resistant cells. Specific anti-miRs were then employed to downregulate the expression of microRNAs in primary tumor cells. Inhibition of miR-9 resulted in decreased clonal formation and sensitivity to cisplatin, while the knockdown of other three microRNAs did not show any influence in tumorigenesis and drug sensitivity. In conclusion, this study showed that in primary ovarian tumor cells, high expression of miR-9 was associated with enhanced tumorigenesis and increased sensitivity of the tumor cells to cisplatin treatment.

Identification of new microRNAs targeting genes regulating the Pi/PPi balance in chondrocytes

Osteoarthritis (OA) is a whole-joint disease characterized by cartilage degradation and mineralization associated with chondrocyte phenotype changes, subchondral bone sclerosis and mild synovial inflammation. The extracellular levels of inorganic phosphate (ePi) and pyrophosphate (ePPi) are major regulators of the mineralization process but also play a role in the maintenance of the differentiated chondrocyte phenotype. Four membrane proteins control the balance between ePi and ePPi: the transporters ANK (exporting PPi outside the cells) and PiT-1 (importing ePi into the cells), and the enzymes PC-1 (generating ePPi from nucleotides) and Tissue Non-specific Alkaline Phosphatase (TNAP, hydrolyzing ePPi into ePi). In the present work, we investigated the ability of specific microRNAs (miR) to modulate activity and level of the mRNA coding for the regulatory proteins of the ePi/ePPi balance in chondrocytes. The 4 following microRNAs, let7e, miR-9, miR-188 and miR-219, were selected by bioinformatics for their ability to putatively target the mRNA 3'UTRs of these regulators. In IL-1β-stimulated human chondrocytes, chosen as a model of differentiated phenotype loss implicating the PPi transporter ANK, miR-9, miR-188 and let7e levels increased. However, luciferase reporter assays and transient miR overexpression in the ATDC5 chondrogenic cell line only support that miR-9 was a negative post-transcriptional regulator of PC-1, Pit-1 and TNAP mRNAs. This suggests that miR-9 could contribute to the acquirement of an altered chondrocyte phenotype by disrupting the ePi/ePPi balance.

MicroRNAs that target RGS5

OBJECTIVES

An earlier meta-analysis on gene expression data derived from four microarray, two cDNA library, and one SAGE experiment had identified RGS5 as one of only ten non-housekeeping genes that were reported to be expressed in human trabecular meshwork (TM) cells by all studies. RGS5 encodes regulator of G-protein signaling-5. The TM tissue is the route of aqueous fluid outflow, and is relevant to the pathology of glaucoma. MicroRNAs constitute the most recently identified components of the cellular machinery for gene regulation in eukaryotic cells. Given our long standing interest in glaucoma, we aimed to identify miRNAs that may target RGS5.

MATERIALS AND METHODS

Eight miRNAs were selected for study using bioinformatics tools and available data on miRNAs expressed in the eye. Their effects were assessed using the dual luciferase assay. 3'-UTR segments of RGS5 mRNA were cloned downstream of a luciferase coding gene in psiCHECK2 vectors, and these were co-transfected with each of the miRNAs into HEK293 cells.

RESULTS

The outcomes evidenced that one or more of the segments are in fact targeted by miR-7, miR-9, miR-96, miR-23a, miR-23b, miR-204, and miR-211. Down regulations by the miRNAs were statistically significant. The effect of miR-204 is considered particularly important as this miRNA is well known to regulate eye development and to affect multiple ocular functions.

CONCLUSION

Our results justify further studies on regulation of RGS5 expression and RGS5 downstream functions by these miRNAs.

Non Coding RNA Molecules as Potential Biomarkers in Breast Cancer

The pursuit of minimally invasive biomarkers is a challenging but exciting area of research. Clearly, such markers would need to be sensitive and specific enough to aid in the detection of breast cancer at an early stage, would monitor progression of the disease, and could predict the individual patient's response to treatment. Unfortunately, to date, markers with such characteristics have not made it to the clinic for breast cancer. Past years, many studies indicated that the non-coding part of our genome (the so called 'junk' DNA), may be an ideal source for these biomarkers. In this chapter, the potential use of microRNAs and long non-coding RNAs as biomarkers will be discussed.

MicroRNA-9 as a novel prognostic biomarker in human laryngeal squamous cell carcinoma

In the present study, we aimed to detect microRNA-9 (miR-9) expression level and its clinical significance in laryngeal squamous cell carcinomas (LSCC). 103 patients who were diagnosed with LSCC and treated between March 2010 and June 2013 were enrolled in this study. Expression levels of miR-9 were detected by real-time quantitative RT-PCR assay. Survival curves were estimated using the Kaplan-Meier method, and differences between them were evaluated by the log-rank test. Cox proportional hazard regression test was used to estimate univariate and multivariate hazard ratios for prognosis. We found that miR-9 levels were significantly higher in LSCC tissues compared with matched non-cancerous tissues [4.55 (164-6.75) vs. 2.07 (0.89-2.65), P < 0.05]. The level of miR-9 in LSCC was strongly correlated with tumor differentiation (P = 0.031), thyroid cartilage invasion (P = 0.024), lymph node metastasis (P = 0.009) and clinical TNM stage (P = 0.011). The log-rank test showed that the survival time was significantly different between groups with high and low expression of miR-9 (Log Rank test, P = 0.014). Furthermore, Cox regression multivariate analysis demonstrated that miR-9 expression was an independent prognostic factor of outcomes in patients with LSCC after tumour resection (HR = 3.18, 95% CI = 2.19-11.91, P = 0.012). In conclusion, miR-9 expression was up-regulated in LSCC and was significantly associated with the progression and poorer prognosis of LSCC. Therefore, it might be utilized as a useful prognostic biomarker for LSCC.

MicroRNA-9 controls dendritic development by targeting REST

MicroRNAs (miRNAs) are conserved noncoding RNAs that function as posttranscriptional regulators of gene expression. miR-9 is one of the most abundant miRNAs in the brain. Although the function of miR-9 has been well characterized in neural progenitors, its role in dendritic and synaptic development remains largely unknown. In order to target miR-9 in vivo, we developed a transgenic miRNA sponge mouse line allowing conditional inactivation of the miR-9 family in a spatio-temporal-controlled manner. Using this novel approach, we found that miR-9 controls dendritic growth and synaptic transmission in vivo. Furthermore, we demonstrate that miR-9-mediated downregulation of the transcriptional repressor REST is essential for proper dendritic growth.

DOI:http://dx.doi.org/10.7554/eLife.02755.001

Messages are sent back and forth in our brains by cells called neurons that connect to each other in complex networks. Neurons develop from stem cells in a complicated process that involves a number of different stages. In one of the final stages, tree-like structures called dendrites emerge from the neurons and connect with neighboring neurons via special junctions called synapses.

A group of small RNA molecules called microRNAs have roles in controlling the development of neurons. One microRNA, called miR-9, is abundant in the brain and is known to be involved in the early stages of neuron development. However, its role in the formation of dendrites and synapses remains unclear.

Giusti et al. studied this microRNA in mice. A length of DNA, coding for an RNA molecule that binds to miR-9 molecules and stops them performing their normal function, was inserted into the mice. These experiments showed that miR-9 is involved in controlling dendrite growth and synaptic function.

To enable a neuron to produce dendrites, miR-9 binds to and interferes with the RNA molecules that are needed to make a protein called REST. This protein is a transcription factor that switches off the expression of other genes so, in effect, miR-9 allows a set of genes that are needed for dendrite growth to be switched on.

The methodology developed by Giusti et al. could be used to study the functions of other microRNAs.

DOI:http://dx.doi.org/10.7554/eLife.02755.002

Curcumin inhibits oral squamous cell carcinoma SCC-9 cells proliferation by regulating miR-9 expression

Curcumin, a phytochemical derived from the rhizome of Curcuma longa, has shown anticancer effects against a variety of tumors. In the present study, we investigated the effects of curcumin on the miR-9 expression in oral squamous cell carcinoma (OSCC) and explored the potential relationships between miR-9 and Wnt/β-catenin pathway in curcumin-mediated OSCC inhibition in vitro. As the results shown, the expression levels of miR-9 were significantly lower in clinical OSCC specimens than those in the adjacent non-tumor tissues. Furthermore, our results indicated that curcumin inhibited OSCC cells (SCC-9 cells) proliferation through up-regulating miR-9 expression, and suppressing Wnt/β-catenin signaling by increasing the expression levels of the GSK-3β, phosphorylated GSK-3β and β-catenin, and decreasing the cyclin D1 level. Additionally, the up-regulation of miR-9 by curcumin in SCC-9 cells was significantly inhibited by delivering anti-miR-9 but not control oligonucleotides. Downregulation of miR-9 by anti-miR-9 not only attenuated the growth-suppressive effects of curcumin on SCC-9 cells, but also re-activated Wnt/β-catenin signaling that was inhibited by curcumin. Therefore, our findings would provide a new insight into the use of curcumin against OSCC in future.

Survival of motor neuron protein downregulates miR-9 expression in patients with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a lethal hereditary disease caused by homozygous absence of the survival of the motor neuron (SMN) 1 gene (SMN1), and it is the leading genetic cause of infant mortality. The severity of SMA is directly correlated with SMN protein levels in affected patients; however, the cellular regulatory mechanisms for SMN protein expression are not completely understood. In this study, we investigated the regulatory effects between SMN expression and miR-9a, a downstream noncoding small RNA. Using an inducible SMN short hairpin RNA interference (shRNAi) system in NSC 34 and human skin fibroblast cells, cellular miR-9 levels and SMN protein repression were time-dependently upregulated. Conversely, cellular miR-9 levels decreased when HeLa cells were transfected with SMN protein fused with green fluorescent protein. In SMA-like mice spinal cords and human primary skin fibroblasts isolated from patients with different degrees of SMA, human SMN exhibited a disease severity-dependent decrease, whereas cellular miR-9 levels increased. These results clearly suggested that cellular SMN proteins regulated miR-9 expression and that miR-9 expression was related to SMA severity. Thus, miR-9 may be a marker for SMA prognosis.

Molecular hydrogen regulates the expression of miR-9, miR-21 and miR-199 in LPS-activated retinal microglia cells

AIM

To explore the potential mechanism of molecular hydrogen in the regulation of miRNA expression and signal-modulating activities.

METHODS

Retinal microglia cells were activated by Lipopolysaccharides (LPS) and then treated with hydrogen-saturated medium or normal medium without hydrogen. qRT-PCR was used to detect the expression difference in miR-9, miR-21 and miR-199 between these two groups. Moreover, the expression of LPS-induced signaling proteins, including Myd88, IKK-β, NF-κB, and PDCD4, were detected by Western blotting.

RESULTS

The results demonstrated a marked down-regulation of miR-9 and miR-21 and up-regulation of miR-199 by hydrogen treatment; the expression of Myd88 and IKK-β was decreased after hydrogen treatment, whereas PDCD4 was increased, and there was no significant change in NF-κB expression.

CONCLUSION

The results in the present study indicate that miR-9, miR-199 and miR-21 play an important role in the anti-inflammatory regulation of LPS-activated microglia cells by molecular hydrogen, which will help to explain the protective mechanism of molecular hydrogen against inflammatory injury.

MicroRNAs in cancers and neurodegenerative disorders

MicroRNAs (miRNAs) are small non-coding RNAs which function as endogenous silencers of various target genes. miRNAs are expressed in a tissue-specific manner and playing important roles in cell proliferation, apoptosis, and differentiation during mammalian development. Links between miRNAs and the initiation and progression of human diseases including cancer are becoming increasingly apparent. Recent studies have revealed that some miRNAs such as miR-9, miR-29 family, and miR-34 family are differentially expressed in Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. These miRNAs are also reported to act as tumor suppressors during human carcinogenesis. In this review, we discuss about miRNAs which are important in the molecular pathogenesis of both cancer and neurodegeneration. Cancer and neurodegenerative disorder may be influenced by common miRNA pathways that regulate differentiation, proliferation, and death of cells.

Impact of aberrant methylation of microRNA-9 family members on non-small cell lung cancers

MicroRNAs (miRs) contribute to cancer development and progression by acting as oncogenes and tumor suppressor genes. miR-9 family members (miR-9s), including miR-9-1, 9-2 and 9-3, have been shown to be oncogenically involved through the downregulation of E-cadherin expression, which promotes the epithelial-mesenchymal transition. Tumor suppressive roles of miR-9s have also been reported to silence miR-9 through methylation, which is associated with an shortened overall survival (OS) period in several types of cancer. In this study, the impact of miR-9s methylation on non-small cell lung cancers (NSCLC) was investigated. In total, 293 resected NSCLC samples were examined and the miR-9s methylation status was determined using a combined bisulfite restriction analysis. miR-9 expression was analyzed by in situ hybridization. Methylation of miR-9-1, 9-2 and 9-3 was present in 20 (7%), 33 (11%) and 34 (12%) of the cases, respectively. Methylation of any miR-9s (miR-9s methylation) was observed in 76 of the cases (26%), and miR-9 expression was silenced in cases with miR-9s methylation. Logistic regression analysis demonstrated that male gender [odds ratio (OR), 2.0; 95% confidence interval (95% CI), 1.1-3.6; P=0.01] and pathologically negative lymph node metastasis (OR, 4.8; 95% CI, 1.4-17.2; P=0.002) were independent relative factors for miR-9s methylation. Additionally, miR-9s methylation [hazard ratio (HR), 4.2; 95% CI, 1.2-27.0; P=0.026] and early pathological stage (HR, 8.3; 95% CI, 2.1-28.6; P=0.004) were found to be independent predictive factors for prolonged OS time by the Cox proportional hazard test. miR-9s methylation which induces expression silencing is common in NSCLC cases without lymph nodal metastasis, suggesting that miR-9s are oncogenically involved in NSCLC carcinogenesis through the promotion of tumor metastasis.

MicroRNAs and Fetal Brain Development: Implications for Ethanol Teratology during the Second Trimester Period of Neurogenesis

Maternal ethanol consumption during pregnancy can lead to a stereotypic cluster of fetal craniofacial, cardiovascular, skeletal, and neurological deficits that are collectively termed the fetal alcohol spectrum disorder (FASD). Fetal ethanol exposure is a leading non-genetic cause of mental retardation. Mechanisms underlying the etiology of ethanol teratology are varied and complex. This review will focus on the developing brain as an important and vulnerable ethanol target. Near the end of the first trimester, and during the second trimester, fetal neural stem cells (NSCs) produce most of the neurons of the adult brain, and ethanol has been shown to influence NSC renewal and maturation. We will discuss the neural developmental and teratological implications of the biogenesis and function of microRNAs (miRNAs), a class of small non-protein-coding RNAs that control the expression of gene networks by translation repression. A small but growing body of research has identified ethanol-sensitive miRNAs at different stages of NSC and brain maturation. While many miRNAs appear to be vulnerable to ethanol at specific developmental stages, a few, like the miR-9 family, appear to exhibit broad vulnerability to ethanol across multiple stages of NSC differentiation. An assessment of the regulation and function of these miRNAs provides important clues about the mechanisms that underlie fetal vulnerability to alterations in the maternal-fetal environment and yields insights into the genesis of FASD.

Functional Studies of microRNAs in Neural Stem Cells: Problems and Perspectives

In adult mammals, neural stem cells (NSCs) are found in two niches of the brain; the subventricular zone by the lateral ventricles and the subgranular zone of the dentate gyrus in the hippocampus. Neurogenesis is a complex process that is tightly controlled on a molecular level. Recently, microRNAs (miRNAs) have been implicated to play a central role in the regulation of NCSs. miRNAs are small, endogenously expressed RNAs that regulate gene expression at the post-transcriptional level. However, functional studies of miRNAs are complicated due to current technical limitations. In this review we describe recent findings about miRNAs in NSCs looking closely at miR-124, miR-9, and let-7. In addition, we highlight technical strategies used to investigate miRNA function, accentuating limitations, and potentials.

An Optimized Sponge for microRNA miR-9 Affects Spinal Motor Neuron Development in vivo

The specification of motor neuron (MN) subtypes and columnar organization in developing spinal cord is controlled by multiple transcription factors. FoxP1 drives specification of lateral motor neuron (LMN) subtypes, and we demonstrated in our previous work that FoxP1 expression levels are regulated by the microRNA miR-9. Here we show that ectopic FoxP1 expression in the chick spinal cord can rescue Lhx3 and Hb9 expression in MNs altered by miR-9 over-expression, demonstrating that FoxP1 is a critical functional interaction partner for miR-9 in LMN development. Moreover, we have optimized a technique called a miRNA sponge in vitro, to permit easy discovery of the role of individual miRNA in vivo using a loss-of-function approach. We here show that narrow spacing between binding sites, inclusion of a coding gene, and optimizing the number of miRNA binding sites can significantly increase the blocking ability of a sponge. We go on to show that a miR-9 sponge reduces detectable miR-9 in the ventral horn, preventing miR-9 silencing of FoxP1 in vivo, and in turn modifies MN subtypes in the spinal cord. Our designs for optimized sponges provide a knockdown tool that is ready to be used to study the function of miRNA in vivo, and in particular for generating transgenic animal models.