MicroRNA - Volume 3, Issue 1, 2014

Impact of mRNA processing and/or modifications has long been associated with gene expression regulation. Accumulating evidence shows alternative polyadenylation (APA), as an mRNA related process, to emerge as a widespread mechanism in gene expression regulation. Through selecting alternate (proximal or distal) polyadenylation signals on the 3’-UTR of pre-mRNAs, APA generates multiple transcript isoforms which may even create proteomic diversity. Depending on the use of proximal or distal polyadenylation sites, 3’-UTR lengths can vary in a tightly controlled manner in a spatial and temporal mode. Therefore, APA and its deregulation with potential consequences are highly relevant to normal and disease states. In this review, in light of recent findings in the literature, mechanism and types of APA and roles of APA in biological processes (i.e. proliferation, development, differentiation, and transformation) are discussed.

The majority of human protein-coding genes are predicted to be targets of miRNA-mediated posttranscriptional regulation. The widespread influence of miRNAs is illustrated by their essential roles in all biological processes. Regulated miRNA expression is essential for maintaining cellular differentiation; therefore alterations in miRNA expression patterns are associated with several diseases, including various cancers. High-throughput sequencing technologies revealed low level expressing miRNA isoforms, termed isomiRs. IsomiRs may differ in sequence, length, target preference and expression patterns from their parental miRNA and can arise from differences in miRNA biosynthesis, RNA editing, or SNPs inherent to the miRNA gene. The association between isomiR expression and disease progression is largely unknown. Misregulated miRNA expression is thought to contribute to the formation and/or progression of cancer. However, due to the diversity of targeted transcripts, miRNAs can function as both tumor-suppressor genes and oncogenes as defined by cellular context. Despite this, miRNA profiling studies concluded that the differential expression of particular miRNAs in diseased tissue could aid the diagnosis and treatment of some cancers.

MicroRNAs are small RNAs that are deregulated under disease conditions. This allows them to be used as biomarkers for disease diagnosis. Recently, such microRNAs are serving as non- invasive blood based biomarkers due to ease of detection, and high stability at room temperature in biofluids. In view of these advancements in biomarker research, efficient miRNA detection at the femtomolar level is important. MiRNA detection techniques to date include Northern blotting, real time PCR and microarray technology. While these are efficient techniques, they cannot detect very low miRNA levels, and have questionable specificity. This review describes nanotechnology, microfluidics and liquid phase miRNA detection techniques that are highly sensitive and specific. With some sophistication, some of these techniques can be used as point of care devices to rapidly detect low level miRNA in patient clinical samples to aid disease diagnosis and prognosis.

Our study aimed to examine the role of micro RNA Mir15a in control of basic ovarian cell functions: proliferation, apoptosis, and secretory activity. In the first series of experiments, primary human ovarian granulosa cells were transfected with antisense construct blocking Mir15a (anti-Mir15a) and cultured without hormonal treatments. Accumulation of markers of proliferation (MAPK/ERK1,2 and PCNA) and apoptosis (caspase 3 and bax), and release of steroid hormones (progesterone, testosterone, and estradiol) were evaluated by immunocytochemical analysis and by enzyme immunoassay. In the second series of experiments, granulosa cells were transfected with gene construct encoding Mir15a precursor (pre-Mir15a) and cultured with and without follicle-stimulating hormone (FSH; 0, 1, 10, and 100 ng/ml). Expression of markers of proliferation (MAPK/ERK1,2) apoptosis (caspase 3), and steroidogenesis (release of progesterone, testosterone, and estradiol) were evaluated. Transfection of cells with anti-Mir15a resulted in a significant increase in accumulation of both proliferation and apoptosis markers, a reduction in progesterone and testosterone release, and an increase in estradiol release. Transfection of cells with pre-Mir15a had an opposite effect: it reduced accumulation of proliferation- and apoptosis-related proteins MAPK/ERK1,2 and caspase 3, and promoted release of progesterone and testosterone, but not estradiol. Moreover, pre-Mir15a reversed the effect of FSH on caspase 3, progesterone, and testosterone, but not on MAPK/ERK1,2 and estradiol. Our observations demonstrate involvement of Mir15a in control of multiple ovarian functions: proliferation, apoptosis, release of progesterone, androgen, and estrogen, and response to gonadotropin. Moreover, this is the first demonstration that miRNAs can affect response of cells to hormonal regulators. We propose that Mir15 could potentially be used for control of different reproductive processes.

miRNAs are short non-coding RNAs which function as oncogenes or tumour suppressor gene and regulate gene expression by controlling targets that play role in cancer development and progression. Numerous recent studies have established an association of abnormal expression of miRNA with cervical cancer progression. Although the number of reported deregulated miRNA in cervical cancer is increasing, only a few associations between miRNA and their targets have been studied in cervical cancer. Therefore, we performed a systematic analysis of known dysregulated miRNAs involved in cervical cancer so as to identify critical miRNA targets that could pave way for therapeutic solutions. In this study, miRNAs reported to be dysregulated in cervical cancer were collected and their targets predicted using TargetScan, PicTar and miRanda. These targets were subsequently compared with previously curated gene dataset involved in cervical cancer to derive the putative target dataset. We then compared network properties (composed of degree, betweenness centrality, closeness centrality and clustering coefficient) of the putative, validated and human protein-protein interaction network. Based on the topological properties genes were ranked and observed that the gene targets BIRC5 (survivin), HOXA1 and RARB presenting with high Novoseek score of Genecards were enriched in cervical cancer. BIRC5 is an anti- apoptotic protein while HOXA1 and RARB are transcription factors which play critical role in altering the level of cell cycle and apoptosis associated proteins. Also, miRNA-mRNA network was constructed and it was found that miR-203 and miR-30b could target these genes. The analysis indicates that the genes BIRC5, HOXA1 and RARB are critical targets that play an important regulatory role in cervical cancer pathogenesis.

MicroRNAs post-transcriptionally regulate the expression of approximately 60% of the mammalian genes, and have an important role in maintaining the differentiated state of somatic cells through the expression of unique tissuespecific microRNA sets. Likewise, the stemness of pluripotent cells is also sustained by embryonic stem cell-enriched microRNAs, which regulate genes involved in cell cycle, cell signaling and epigenetics, among others. Thus, microRNAs work as modulator molecules that ensure the appropriate expression profile of each cell type. Manipulation of microRNA expression might determine the cell fate. Indeed, microRNA-mediated reprogramming can change the differentiated status of somatic cells towards stemness or, conversely, microRNAs can also transform stem- into differentiated-cells both in vitro and in vivo. In this Review, we outline what is currently known in this field, focusing on the applications of microRNA in tissue engineering.

The generation of β-cells in vitro is an attractive option for cell therapy treatments for type 1 diabetes and also for the development of more accurate disease models. A number of studies have demonstrated that insulin-expressing cells can be generated by the in vitro differentiation of human pluripotent stem cells. However, to date, these differentiation protocols are often inefficient, time-consuming and highly variable. In many cases, this is a result of an incomplete understanding of the regulatory processes involved in the differentiation of human pluripotent stem cells. One such process is the control of gene expression by microRNAs (miRNAs). Given that miRNAs have the potential to influence cell fate, we present in this short review the evidence that a further understanding of the role of miRNAs in pancreatic development and function may be important in the on-going quest to generate insulin-secreting cells from pluripotent stem cells.

Previous studies suggested that microRNAs (miRNAs) participate in almost all cellular processes and the continuous development of miRNA-mediated posttranscriptional regulation might have facilitated the development of complex organisms. Especially, the microRNA-22 (miR-22) family has been recently extensively reported. Here, we accessed the evolution of miR-22 structure, regulation, and targets, and this indicated that miR-22 plays key roles in more complex organisms. We demonstrated that the miR-22 family arose approximate 600 million years ago from the latest common ancestor of bilaterians. Moreover, a survey of genomic contexts and the secondary structure of the miR-22 family revealed that it originated de novo from a relatively conserved intron region, and the mature sequence of the miR-22 family evolved by seed pairing with highly conserved 3' "U" and 5' "G" boundaries. Furthermore, a complete picture of the evolution of the regulatory networks associated with miR-22 was obtained from the analysis of experimentally identified, as well as computationally predicted, functional targets of miR-22.