Project description:We investigated functions of miRNAs at the level of the whole transcriptome of primary neurons. We transfected mouse E17.5 forebrain primary neuronal cultures (at four to six days of in vitro development) with miRNA mimics and inhibitors. After approximately 48 h post transfection we profiled the effect of these transfections on gene expression with Illumina mRNA microarrays. Cultures were transfected with mimics and inhibitors of five mouse miRNAs (mmu-miR-124, mmu-miR-434-3p, mmu-miR-143, mmu-miR-145 and mmu-miR-25) and with a mimic of a non-mouse miRNA (cel-miR-67). Direct widespread inhibition of gene expression by the perturbed miRNAs was evident when gene expression in cultures transfected with miRNA mimics was compared to those transfected with the inhibitors (or to matched mock transfected cultures): 3-prime UTRs of downregulated transcripts were significantly enriched in seed matching sites for the perturbed miRNAs. Interestingly, analysis of differential gene expression in mock transfected cells (identified through comparison of mock transfected cultures with matched untreated cultures) revealed that genes inhibited by miRNAs were enriched in genes upregulated in mock transfected cultures. This inhibition was the most efficient by the two neuronal miRNAs under investigation (mmu-miR-124 and mmu-miR-434-3p). To investigate if miRNA mediated inhibition of stress induced genes (i.e. stress associated with transfections) was also the case in other stresses, we profiled gene expression changes triggered by chronic neuronal depolarisation. For this, we treated the cultures with KCl (15 mM, 48 h) and compared them to matched untreated cultures. We found that genes upregulated by KCl had a significant intersection with those upregulated by the mock transfection. Moreover, we also found that genes upregulated by KCl had a significant intersection with genes inhibited by mmu-miR-124 and mmu-miR-434-3p. Therefore we concluded that neuronal miRNAs stabilise the neuronal transcriptome by inhibiting stress inducible genes.

Project description:Liver is uniquely capable to repair itself after injury. Multiple molecular and biochemical processes initiated after partial hepatectomy, lead to proliferation of all cells within the liver. MicroRNAs (miRNAs) are a class of highly abundant non-coding RNA molecules that cause post-transcriptional gene repression and are involved in several biological processes including cell cycle regulation and differentiation. We examined the expression levels of miRNAs in liver tissue received from control mice (L0) and compared them with the corresponding levels in liver tissue 12 hours after liver regeneration induced by 2/3 partial hepatectomy (L12). MicroRNA expression was investigated using microRNA profiling. Further qPCR analysis was used for validation of the differentially expressed microRNAs at an early stage of liver regeneration, induced by 2/3 partial hepatectomy. TargetScan and Gene Ontology (GO) analysis was performed in order to identify the possible miRNA target genes and their ontology, respectively. A subset of miRNAs were found to be differentially expressed during liver regeneration. Mmu-miR-21 and mmu-miR-30b* showed the higher levels of up-regulation in liver tissue from the hepatectomized mice at the end of the experiment (L12) compared to the sham operated mice (L0). Mmu-miR-21 up-regulation was further confirmed by qPCR. In situ hybridization (ISH) revealed that mmu-miR-21 exhibited the higher levels of expression at 12 hours post hepatectomy. On the contrary, mmu-miR-34c*, mmu-miR-144, mmu-miR-207, mmu-miR-207, mmu-miR-451, mmu-miR-582-3p and mmu-miR-290-5p exhibited <0.5 down-regulation in liver tissue after partial hepatectomy in L12 vs. L0 mice. Microarrays and qPCR results were in good agreement (Pearson correlation = 0.881). Our results provide important information regarding how microRNAs are deferentially expressed in murine liver tissue before and after partial hepatectomy. The early up-regulation of mmu-miR-21 during the process of liver regeneration suggests a regulatory role in liver regeneration in vivo.

Project description:Liver is uniquely capable to repair itself after injury. Multiple molecular and biochemical processes initiated after partial hepatectomy, lead to proliferation of all cells within the liver. MicroRNAs (miRNAs) are a class of highly abundant non-coding RNA molecules that cause post-transcriptional gene repression and are involved in several biological processes including cell cycle regulation and differentiation. We examined the expression levels of miRNAs in liver tissue received from control mice (L0) and compared them with the corresponding levels in liver tissue 12 hours after liver regeneration induced by 2/3 partial hepatectomy (L12). MicroRNA expression was investigated using microRNA profiling. Further qPCR analysis was used for validation of the differentially expressed microRNAs at an early stage of liver regeneration, induced by 2/3 partial hepatectomy. TargetScan and Gene Ontology (GO) analysis was performed in order to identify the possible miRNA target genes and their ontology, respectively. A subset of miRNAs were found to be differentially expressed during liver regeneration. Mmu-miR-21 and mmu-miR-30b* showed the higher levels of up-regulation in liver tissue from the hepatectomized mice at the end of the experiment (L12) compared to the sham operated mice (L0). Mmu-miR-21 up-regulation was further confirmed by qPCR. In situ hybridization (ISH) revealed that mmu-miR-21 exhibited the higher levels of expression at 12 hours post hepatectomy. On the contrary, mmu-miR-34c*, mmu-miR-144, mmu-miR-207, mmu-miR-207, mmu-miR-451, mmu-miR-582-3p and mmu-miR-290-5p exhibited <0.5 down-regulation in liver tissue after partial hepatectomy in L12 vs. L0 mice. Microarrays and qPCR results were in good agreement (Pearson correlation = 0.881). Our results provide important information regarding how microRNAs are deferentially expressed in murine liver tissue before and after partial hepatectomy. The early up-regulation of mmu-miR-21 during the process of liver regeneration suggests a regulatory role in liver regeneration in vivo. Twenty male wild type mice C57BL6J (8 weeks old) fed a standard diet were used for the liver regeneration experiment. Mice were housed in the animal facility of the University of Patras Medical School in temperature-, light- and humidity-controlled rooms with a 12-h light/dark cycle. All animal procedures were approved by the institutional review board of the University of Patras Medical School and were in accordance with EC Directive 86/609/EEC. A 2/3 partial hepatectomy (PH) was performed on 10 mice according to a recently published standardized protocol whereby the median and left lobes of the liver were removed and another 10 sham operated mice were used as the control group. The liver was allowed to regenerate and mice were sacrificed 12 hours after operation. Liver samples were collected from the sham operated mice (L0) and the hepatectomized mice at the end of the experiment (L12).

Dataset Information

SiRNA of mouse undifferentiated Dicer -/- (27H10) embryonic stem cells

Publications

MicroRNAs control de novo DNA methylation through regulation of transcriptional repressors in mouse embryonic stem cells.

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