MicroRNA - Volume 6, Issue 1, 2017

MicroRNAs (miRNAs) are short, non-coding RNAs that regulate gene expression at a posttranscriptional level. Each miRNA controls the expression of multiple messenger RNAs (mRNAs) and their dysregulation has been implicated in multiple cancer phenotypes. While some miRNAs are upregulated, global downregulation of miRNA expression is often the rule in cancer. A multitude of potential mechanisms drive aberrant miRNA expression in cancer; miRNA coding regions can harbour genomic defects including mutations, amplifications or deletions, and some miRNAs are broadly repressed by transcription factors such as Myc or have epigenetic modifications to their promoter regions such as hypermethylation of CpG islands. Additionally, the suppression of components of the miRNA processing machinery has been shown to reduce mature miRNA expression and contribute to the malignant phenotype. Understanding the mechanisms driving miRNA downregulation is important in uncovering the critical and complex role of miRNAs in cancer biology. This review will outline the multiple mechanisms by which cancer cells suppress miRNA expression.

Among the clinical spectrum of neurological diseases, migraine is often associated with cerebro-vasculopathy. Impairment of neuroimmune mediators in the central nervous system has been recognized in the pathophysiology of migraine-related stroke. Although genetic correlation was found in patients with migraine-related stroke, the epidemiology of this disease indicates a need in biomarker searching discovery and validation. In this view, small molecule, called microRNAs (miRNAs), able to regulate immune and neuronal processes has been reported in patients with migraine and ischemic stroke and unambiguous miRNAs related to these diseases could be established as new molecular indicator of precocity for clinical and/or pharmacological intervention. Therefore, further exploration of this area is necessary, as greater understanding of these biomarkers could reveal the common mechanisms involved in the pathophysiology of migraine in patients with cerebral infarct.

MicroRNAs are emerging players in plant development and response to stresses, both biotic and abiotic such as micronutrient deficiency. These small RNAs regulate cognate downstream targets either by transcript cleavage or translational inhibition. Micronutrient deficiencies lead to poor quality and yield of crops and impaired human health. Over the years several microRNAs have been identified which regulate expression of genes controlling uptake, mobilization and homeostasis of macronutrients such as nitrogen, phosphorus and sulfur to ensure sufficiency without toxicity. This review attempts to understand the roles played by micro RNAs involved in homeostasis of the micronutrients boron, manganese, zinc, copper, iron, molybdenum and nickel and the cross talk between them upon perception of nutritional stress. Notably and surprisingly, several micro RNAs are not specific for a particular micronutrient stress and the challenge remains to uncover ones (if any) that are directly relevant to the micronutrient. Current findings of this yet infant field could potentiate biotechnological applications towards biofortification, plant innate immunity and remedy heavy metal toxicity.

Background: Early and specific detection of cancer is of great importance for successful treatment of the disease. New biomarkers, such as microRNAs, could improve treatment efficiency and survival ratio. In human medicine, deregulation of microRNA profiles in circulation has shown great potential as a new type of biomarker for cancer diagnostics. There are, however, few studies of circulating microRNAs in dogs. Extracellular circulating microRNAs have shown a high level of stability in human blood and other body fluids. Nevertheless, there are still important issues to be solved before microRNAs can be applied routinely as a clinical tool, one of them being their stability over time in media commonly used for blood sampling. Objective: Evaluation of the stability of microRNA levels in plasma and serum from healthy dogs after storage at room temperature for different time points before being processed. Methods: The levels of four microRNAs (cfa-let-7a, cfa-miR-16, cfa-miR-23a and cfa-miR-26a) known to be stably expressed from other canine studies, have been measured by quantitative real-time PCR (qPCR). Results: MicroRNA levels were found sufficiently stable for gene profiling in serum- and plasma stored at room temperature for 1 hour but not for samples stored at room temperature for 24 hours. Conclusion: Storage at room temperature of serum and plasma samples intended for microRNA profiling should be kept for a minimum period of time before proceeding with RNA isolation. For the four microRNAs investigated in the present study, we did not find significant differences in microRNA levels between serum and plasma samples from the same time point.

Background: The goal of this project was to characterize the molecular and cellular roles of various gene targets regulated by miRNAs identified in differentiating and stimulating avian macrophages. Once a monocyte arrives to a site of infection, local signals induce a redistribution of resources into a macrophage phenotype. This may involve upregulating pathogen pattern recognizing receptors and increasing the efficiency of lysosomal biogenesis, while simultaneously recycling components involved in circulatory migration and leukocyte extravasation. a monocyte tooled with chemokine surface receptors and an internal cytoskeletal structure geared towards mobility may efficiently sense, react, and migrate toward a site of infection. Methods: Peripheral blood derived monocytes were purified and cultured from young chickens. RNA sequencing was performed on both peripheral blood monocytes during differentiation into macrophages and on mature macrophages following stimulation with interferon gamma. A set of microRNAs were identified and investigated using bioinformatics methods to ascertain their potential role in avian macrophage biology. Results: Among a number of miRNAs that are found to be expressed in avian macrophages, we focused on eight specific miRNAs (miR-1618, miR-1586, miR-1633, miR-1627, miR-1646, miR-1649, miR-1610, miR-1647) associated with macrophage differentiation and activation. Expression profiles of microRNAs were characterized during differentiation and activation. Candidate miRNA targets were implicated in processes including Wnt signaling, ubiquitination, PPAR mediated macrophage function, vesicle mediated cytokine trafficking, and WD40 domain protein functions. Conclusion: A global theme for macrophage function that may be modulated by microRNAs is the comprehensive redistribution of the cell’s protein repertoire. This redistribution involves two processes: 1) the degradation and recycling of unneeded cytoplasmic and membrane components and 2) the mobilization of newly synthesized cellular components via vesicular trafficking. Generally, it appears that macrophages need to closely regulate gene expression for differentiation to be able to activate successfully in response to a pathogen. This is a process in which miRNAs participate by affecting several pathways critical for both, differentiation and activation.

Background: MicroRNAs are the key regulators of gene expression and their abnormal expression in the immune system may be associated with several human diseases such as inflammation, cancer and autoimmune diseases. Elucidation of miRNA disease association through the interactome will deepen the understanding of its disease mechanisms. A specialized database for immune miRNAs is highly desirable to demonstrate the immune miRNA disease associations in the interactome. Methods: miRNAs specific to immune related diseases were retrieved from curated databases such as HMDD, miR2disease and PubMed literature based on MeSH classification of immune system diseases. The additional data such as miRNA target genes, genes coding protein-protein interaction information were compiled from related resources. Further, miRNAs were prioritized to specific immune diseases using random walk ranking algorithm. Results: In total 245 immune miRNAs associated with 92 OMIM disease categories were identified from external databases. The resultant data were compiled as ImmunemiR, a database of prioritized immune miRNA disease associations. This database provides both text based annotation information and network visualization of its interactome. Conclusion: To our knowledge, ImmunemiR is the first available database to provide a comprehensive repository of human immune disease associated miRNAs with network visualization options of its target genes, protein-protein interactions (PPI) and its disease associations. It is freely available at http://www.biominingbu.org/immunemir/