ABSTRACT: MicroRNAs (miRNAs) are a class of regulatory RNAs that control the expression of genes critical to cell function. Ectopic expression of miRNAs has been shown to result in genome-wide changes in patterns of gene expression. While the reasons for these global alterations in gene expression patterns have been attributed to the ability of miRNAs to target multiple genes, and/or to induce indirect effects downstream of target genes, the molecular basis of indirect effects of miRNA regulation remains poorly understood. In this study, we demonstrate the potential of miRNAs to regulate other miRNAs. Using miRNA microarray analysis, we show that over 70 different miRNAs are differentially expressed ( M-bM-^IM-%1.4 fold, FDR M-bM-^IM-$ 5%) in human ovarian cancer cells after transfection with a single miRNA (miR-7). We present evidence that a major component of miR-7-induced changes in levels of miRNAs is the indirect consequence of miR-7-mediated alterations in levels of protein-coding genes (e.g., transcription and splicing factors) that exert trans-regulatory control on miRNAs. HEY cells were transfected with either hsa-miR-7 (2 biological replicates) or a negative control miRNA, miR-NC (2 biological replicates), and then grown in 6-well plates for ~48 hours. The difference in miRNA expression pattern between the miR-7-transfected cells and the miR-NC-transfected cells was determined using an Affymetrix GeneChip miRNA Array.
Project description:MicroRNAs (miRNAs) are short (~22 nucleotides) regulatory RNAs that can modulate gene expression and are aberrantly expressed in many diseases including cancer. Previous studies have shown that miRNAs inhibit the translation and facilitate the degradation of their targeted mRNAs making them attractive candidates for use in cancer therapy. However, the potential clinical utility of miRNAs in cancer therapy rests heavily upon our ability to understand and accurately predict the consequences of fluctuations in levels of miRNAs within the context of complex tumor cells. To evaluate the predictive power of current models, levels of miRNAs and their targeted messenger RNAs (mRNAs) were measured in laser captured micro-dissected (LCM) ovarian cancer epithelial cells (CEPI) and compared with levels present in ovarian surface epithelial cells (OSE). We found that the predicted inverse correlation between changes in levels of miRNAs and levels of their mRNA targets held for only ~6-11% of predicted target mRNAs. Our results underscore the complexities of miRNA-mediated regulation in vivo and caution against the widespread clinical application of miRNAs and miRNA inhibitors until the basis of these complexities is more fully understood. mRNAs were collected from 3 miR-7 treated, 2 miR-128 treated , and 3 negative control miRNA treated HEY ovarian cancer cell samples. The mRNA expression pattern was compared between the miR-7 treated cells and the negative control treated cells, and separately between the miR-128 treated cells and the negative control treated cells using the Affymetrix U133 Plus 2.0 3' expression array.
Project description:Clear cell renal cell carcinomas (ccRCC) are characterized by arm-wide chromosomal alterations. Loss at 14q is associated with disease aggressiveness in ccRCC, which responds poorly to chemotherapeutics. The 14q locus contains one of the largest miRNA clusters in the human genome; however, little is known about the contribution of these miRNAs to ccRCC pathogenesis. In this regard, we investigated the expression pattern of selected miRNAs at the 14q32 locus in TCGA kidney tumors and in ccRCC cell lines. We validated that the miRNA cluster is downregulated in ccRCC (and cell lines) as well as in papillary kidney tumors relative to normal kidney tissues and primary renal proximal tubule epithelial (RPTEC) cells. We demonstrated that agents modulating expression of DNMT1 (e.g., 5-Aza-deoxycytidine) could modulate miRNA expression in ccRCC cell lines. Lysophosphatidic acid (LPA, a Lysophospholipid mediator elevated in ccRCC) not only increased labile iron content but also modulated expression of 14q32 miRNAs. Through an overexpression approach targeting a subset of 14q32 miRNAs (specifically at subcluster A: miR-431, miR-432, miR-127, and miR-433) in 769-P cells, we uncovered changes in cellular viability and claudin-1, a tight junction marker. A global proteomic approach was implemented using these miRNA overexpressing cell lines which uncovered ATXN2 as a highly downregulated target, which has a role in chronic kidney disease pathogenesis. Collectively, these findings support a contribution of miRNAs at 14q32 in ccRCC pathogenesis.
Project description:The identification of miRNAs’ targets and associated regulatory networks might allow the definition of new strategies using drugs whose association might mimic a given miRNA’s effects. Based on this assumption our group devised a multi-omics approach in an attempt to precisely characterize miRNAs’ effects. We combined the analysis of miR-491-5p direct targets, and effects at the transcriptomic and proteomic levels. We thus constructed an interaction network which enlightened highly connected nodes, being either direct or indirect targets of miR-491-5p effects: the already known EGFR and BCL2L1, but also EP300, CTNNB1 and several small-GTPases. By using different combinations of specific inhibitors of these nodes, we could greatly enhance their respective cytotoxicity and mimic miR-491-5p-induced phenotype. Our methodology thus constitutes an interesting strategy to comprehensively study the effects of a given miRNA. Also, we identified targets for which pharmacological inhibitors are already available for a clinical use, or in clinical trial phases. This study might thus enable innovative therapeutic options for ovarian cancer, which remains the first cause of death from gynecological malignancies in developed countries.
Project description:These experiments were conducted as part of a study to derive the targets of miRNAs (See also E-MTAB-418). Two independent BayGenomics mouse embryonic stem cell lines (XH157 and XG058), each bearing a gene trap between exons 9 and 10 of the Dgcr8 locus (ENSMUST00000115633, Ensembl v53) were further mutagenised by the targetted insertion of a second Dgcr8 gene trap cassette. Consequently two independent heterozygous and two independent homozygous mutant Dgcr8 cells were derived (Dgcr8tm1,gt1/+, Dgcr8tm1,gt2/+, Dgcr8gt1/tm1 and Dgcr8gt2/tm1). Subsequently individual miRNA mimics were reintroduced into the Dgcr8-depleted background. In this set of experiments, cells were allowed to recover for 10 hours. The effect of the miRNA on the mRNA expression of the cells was assessed through the comparison of the expression profile of the transfected cells to that of cells transfected with a control mimic, which had recovered over the same period. This allows the roles of individual miRNAs to be investigated.
Project description:The contribution of microRNA-mediated posttranscriptional regulation on the final proteome in differentiating cells remains elusive. Here, we evaluated the impact of microRNAs (miRNAs) on the proteome of human umbilical cord blood-derived unrestricted somatic stem cells (USSC) during retinoic acid (RA) differentiation by a systemic approach using next generation sequencing analysing mRNA and miRNA expression and quantitative mass spectrometry-based proteome analyses. Interestingly, regulation of mRNAs and their dedicated proteins highly correlated during RA-incubation. Additionally, RA-induced USSC demonstrated a clear separation from native USSC thereby shifting from a proliferating to a metabolic phenotype. Bioinformatic integration of up- and downregulated miRNAs and proteins initially implied a strong impact of the miRNome on the XXL-USSC proteome. However, quantitative proteome analysis of the miRNA contribution on the final proteome after ectopic overexpression of downregulated miR-27a-5p and miR-221-5p or inhibition of upregulated miR-34a-5p, respectively, followed by RA-induction revealed only minor proportions of differentially abundant proteins. In addition, only small overlaps of these regulated proteins with inversely abundant proteins in non-transfected RA-treated USSC were observed. Hence, mRNA transcription rather than miRNA-mediated regulation is the driving force for protein regulation upon RA-incubation, strongly suggesting that miRNAs are fine-tuning regulators rather than active primary switches during RA-induction of USSC.
Project description:To identify the target of miR-4653-3p, mRNA microarray analysis was performed to compare mRNA expression between MIA PaCa-2 cells transfected with miR-4653-3p mimic and negative control cells.
Project description:For androgen-independent prostate cancer (AIPC), the current treatment is limited and the prognosis is poor. We previously found miR-200b could inhibit androgen independent proliferation ability of prostate cancer cells, but the mechanism is unclear. MiRNAs plays their role by blocking translation through base-pairing with complementary mRNA and by promoting degradation of target mRNA. Unraveling the miRNA translational silencing network remains a challenge in part because a single miRNA can inhibit multiple mRNA targets and because a single mRNA can be regulated by several distinct miRNAs that act cooperatively. However, proteomics methods provide us useful tools to unravel the target genes network. This study identified the target genes of miR-200b in AIPC. It helps us to understand the mechanism of AIPC and applies several new candidate targets of AIPC treatment.
Project description:Defects in stress responses are important contributors in many chronic conditions including cancer, cardiovascular disease, diabetes, and obesity-driven pathologies like non-alcoholic steatohepatitis (NASH). Specifically, endoplasmic reticulum (ER) stress is linked with these pathologies and control of ER stress can ameliorate tissue damage. MicroRNAs have a critical role in regulating diverse stress responses including ER stress. Here we show that miR-494-3p plays a functional role during ER stress. ER stress inducers (tunicamycin and thapsigargin) robustly increase the expression of miR-494 in vitro in an ATF6 dependent manner. Surprisingly, miR-494 pretreatment dampens the induction and magnitude of ER stress in response to tunicamycin in endothelial cells. Conversely, inhibition of miR-494 increases ER stress de novo and amplifies the effects of ER stress inducers. Using Mass Spectrometry (TMT-MS) we identified many proteins that are downregulated by both tunicamycin and miR-494 in cultured human umbilical vein endothelial cells (HUVECs). Among these, we found 6 transcripts which harbor a putative miR-494 binding site. Our data indicates that ER stress driven miR-494 may act in a feedback inhibitory loop to dampen downstream ER stress signaling. We propose that RNA-based approaches targeting miR-494 or its targets may be attractive candidates for inhibiting ER stress dependent pathologies in human disease.
Project description:These experiments were conducted as part of a study to derive the targets of miRNAs. Two independent BayGenomics mouse embryonic stem cell lines (XH157 and XG058), each bearing a gene trap between exons 9 and 10 of the Dgcr8 locus (ENSMUST00000115633, Ensembl v53) were further mutagenised by the targetted insertion of a second Dgcr8 gene trap cassette. Consequently two independent heterozygous and two independent homozygous mutant Dgcr8 cells were derived (Dgcr8tm1,gt1/+, Dgcr8tm1,gt2/+, Dgcr8gt1/tm1 and Dgcr8gt2/tm1). A comparison of the expression profiles of the heterozygous cells to the Dgcr8 depleted cells allows the investigation of the broad role of miRNAs in mouse ES cells. Subsequently individual miRNA mimics were reintroduced into the Dgcr8-depleted background. The cells were allowed to recover for 10, 20 or 44 hours. The effect of the miRNA on the mRNA expression of the cells was assessed through the comparison of the expression profile of the transfected cells to that of cells transfected with a control mimic, which had recovered over the same period. This allows the roles of individual miRNAs to be investigated.
Project description:MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by base-pairing to complementary sites in mRNAs. The primary element for site recognition is the seed region (nucleotides 2-8 in the miRNA), but for a minority of sites pairing outside the seed increases efficiency, with the supplementary region (nucleotides 13-16) typically having the greatest impact. However, the structural determinants of effective pairing outside the seed are not fully understood. Here, we use abasic modified nucleotides to disrupt pairing to residues 13 and 14 of miR-34a and measure the effect of this modification compared to wild-type miR-34a on the cellular transcriptome and proteome using RNA-seq and mass spectrometry. We find that a subset of sites with predicted supplementary pairing are affected by miRNA transfection, with up to two-fold decreases in site repression at the mRNA level, although the effect at the protein level is less pronounced. Overall, this study demonstrates a novel methodological approach for elucidating the role of specific miRNA residues in target site selection, advancing our understanding of miRNA-mediated gene regulation.