Twenty years of RNA: the discovery of microRNAs

MiR-107 inhibits the sprouting of intersegmental vessels of zebrafish embryos

MicroRNAs (miRNAs) play important roles in various biological processes. Our previous study showed that inhibition of MTOR with rapamycin treatment suppressed human endothelial cell tube formation, concomitant with the down-regulation of miR-107. Similarly, inhibition of Ztor by rapamycin also suppressed vascular development in zebrafish embryos. To gain a better understanding of the role of miR-107 and MTOR in vascular development, the present study sought to validate its function by over-expressing miR-107 in zebrafish embryos via microinjection with mimic miR-107 duplexes. Alkaline phosphatase (ALP) staining was used to visualise blood vessels in the zebrafish embryo, and expressions of Pten, Ztor and Rap1 were investigated by immunoblotting. Over-expression of miR-107 in zebrafish embryos inhibited the sprouting of intersegmental vessels (ISVs) with concomitant down-regulation of phosphorylated Rps6 expression, which confirmed the inhibition of Ztor signalling. As expected, pten, which is the target of miR-107, was down-regulated. Interestingly, Rap1, a small GTPase protein that is involved in intersomitic vessels sprouting during angiogenesis, was also down-regulated when miR-107 was over-expressed. Overall, our findings suggest that miR-107 and Ztor-mediated suppression of vascular development in zebrafish embryo involves Rap1.

Ox-LDL Aggravates the Oxidative Stress and Inflammatory Responses of THP-1 Macrophages by Reducing the Inhibition Effect of miR-491-5p on MMP-9

Background: Oxidized low-density lipoprotein (ox-LDL) can induce oxidative stress and inflammatory responses in macrophages to facilitate the genesis and development of atherosclerosis. However, the intermediate links remain unclear. MiR-491-5P can inhibit matrix metalloproteinase 9 (MMP-9); however, it remains unclear whether ox-LDL enhances MMP-9 expression and aggravates the oxidative stress and inflammatory responses under the mediating effect of miR-491-5P.

Method: THP-1 macrophages were divided into 10 groups: blank (control), model (ox-LDL), miR-491-5P high-expression (miR-491-5P mimic), miR-491-5P control (mimic-NC), MMP-9 high-expression (MMP-9-plasmid), MMP-9 control (plasmid-NC), miR-491-5P+plasmid-NC, miR-491-5P+ MMP-9-plasmid, MMP-9 gene silencing (MMP-9-siRNA), and gene silencing control (siRNA-NC). The cells were transfected for 48 h and then treated with 50 μg/mL of ox-LDL for 24 h. MMP-9 mRNA and miR-491-5P expression levels in the cells were detected using reverse transcription-quantitative polymerase chain reaction, and the MMP-9 levels were detected with western blotting. The levels of oxidative stress factors (malondialdehyde [MDA]), reactive oxygen species (ROS), and antioxidant factors (superoxide dismutase [SOD]), and the expression levels of inflammatory factors (tumor necrosis factor [TNF-α] and interleukin-1β and−6 [IL-1β and IL-6]) in the supernatant were detected with enzyme-linked immunosorbent assay.

Results: MDA, ROS, TNF-α, IL-1β, IL-6, and MMP-9 levels were increased, SOD activity was reduced, and miR-491-5P expression was downregulated in the ox-LDL group compared to the control group. In the miR-491-5P mimic group, the MDA, ROS, TNF-α, IL-1β, IL-6, MMP-9 mRNA and protein levels were downregulated, and SOD activity was enhanced compared to the ox-LDL group. MMP-9-plasmid elevated the MDA, ROS, TNF-α, IL-1β, IL-6, MMP-9 mRNA and protein levels, and downregulated SOD activity and miR-491-5P expression. Following transfection with MMP-9-siRNA, the MMP-9-plasmid outcomes were nullified, and the resulting trends were similar to the miR-491-5p simulation group. Oxidative stress and inflammatory responses were higher in the miR-491-5P mimic+MMP-9-plasmid co-transfection group than in the miR-491-5P mimic group.

Conclusion: Ox-LDL aggravates the oxidative stress and inflammatory responses of THP-1 macrophages by reducing the inhibition effect of miR-491-5p on MMP-9.

Inhibition of microRNA-299-5p sensitizes glioblastoma cells to temozolomide via the MAPK/ERK signaling pathway

Glioblastomas (GBMs) are a lethal class of brain cancer, with a median survival <15 months in spite of therapeutic advances. The poor prognosis of GBM is largely attributed to acquired chemotherapy resistance, and new strategies are urgently needed to target resistant glioma cells. Here we report a role for miR-299-5p in GBM. The level of miR-299-5p expression was detected in glioma specimens and cell lines by qRT-PCR. Luciferase reporter assays and Western blots were performed to verify GOLPH3 as a direct target of miR-299-5p. In vitro cell proliferation, invasion, cell cycle distribution, and apoptosis were assessed to determine whether or not miR-299-5p knockdown sensitized GBM cells to temozolomide (TMZ). We demonstrated that miR-299-5p levels were up-regulated in the GBM groups compared with the normal control group. The highest expression of miR-129-5p occurred in the highest GBM stage. miR-299-5p knockdown significantly inhibited the MAPK/extracellular signal-regulated kinase (ERK) signaling pathway. We also showed that miR-299-5p knockdown enhanced sensitivity of GBM cells to TMZ both in vitro and in vivo by inhibiting cell proliferation and invasion and promoting apoptosis. In addition, we demonstrated that GOLPH3 is a novel functional target of miR-299-5p GOLPH3 regulates the MAPK/ERK axis under miR-299-5p regulation. In conclusion, we identified a link between miR-299-5p expression and the GOLPH3/MAPK/ERK axis, thus illustrating a novel role for miR-299-5p in GBM.

Discovering Structural Motifs in miRNA Precursors from the Viridiplantae Kingdom

A small non-coding molecule of microRNA (19–24 nt) controls almost every biological process, including cellular and physiological, of various organisms’ lives. The amount of microRNA (miRNA) produced within an organism is highly correlated to the organism’s key processes, and determines whether the system works properly or not. A crucial factor in plant biogenesis of miRNA is the Dicer Like 1 (DCL1) enzyme. Its responsibility is to perform the cleavages in the miRNA maturation process. Despite everything we already know about the last phase of plant miRNA creation, recognition of miRNA by DCL1 in pre-miRNA structures of plants remains an enigma. Herein, we present a bioinformatic procedure we have followed to discover structure patterns that could guide DCL1 to perform a cleavage in front of or behind an miRNA:miRNA* duplex. The patterns in the closest vicinity of microRNA are searched, within pre-miRNA sequences, as well as secondary and tertiary structures. The dataset consists of structures of plant pre-miRNA from the Viridiplantae kingdom. The results confirm our previous observations based on Arabidopsis thaliana precursor analysis. Hereby, our hypothesis was tested on pre-miRNAs, collected from the miRBase database to show secondary structure patterns of small symmetric internal loops 1-1 and 2-2 at a 1–10 nt distance from the miRNA:miRNA* duplex.

A microRNA cluster (let-7c, miRNA-99a, miRNA-125b, miRNA-155 and miRNA-802) encoded at chr21q21.1-chr21q21.3 and the phenotypic diversity of Down's syndrome (DS; trisomy 21)

Down's syndrome (DS) is the most common genetic cause of intellectual disability and cognitive deficit attributable to a naturally-occurring abnormality of gene dosage. DS is caused by a triplication of all or part of human chromosome 21 (chr21) and currently there are no effective treatments for this incapacitating disorder of neurodevelopment. First described by the English physician John Langdon Down in 1862, propelled by the invention of karyotype analytical techniques in the early 1950s and the discovery in 1959 by the French geneticist Jerome Lejune that DS resulted from an extra copy of chr21, DS was the first neurological disorder linking a chromosome dosage imbalance to a defect in intellectual development with ensuing cognitive disruption. Especially over the last 60 years, it has been repeatedly demonstrated that DS is not an easily defined disease entity but rather possesses a remarkably wide variability in the 'phenotypic spectrum' associated with this trisomic disorder. This commentary describes the presence of a 5 member cluster of chr21-encoded microRNAs (miRNAs) that includes let-7c, miRNA-99a, miRNA-125b, miRNA-155 and miRNA-802 located on the long arm of human chr21, spanning the chr21q21.1-chr21q21.3 region and flanking the beta amyloid precursor (βAPP) gene, and reviews the potential contribution of these 5 miRNAs to the remarkably diverse DS phenotype.