Role Of miRNAs In Development Research Articles

The Role of Exogenous microRNAs on Human Health: The Plant-Human Trans-Kingdom Hypothesis.

MicroRNAs (miRNAs) are small, endogenous, single-stranded RNAs that act on gene silencing at the post-transcriptional level by binding to a target messenger RNA (mRNA), leading to its degradation or inhibiting translation into functional proteins. The key role of miRNAs in development, proliferation, differentiation andapoptosis has been deeply investigated, revealing that deregulation in their expression is critical in various diseases, such as metabolic disorders and cancer. Since these small molecules initially evolved as a mechanism of protection against viruses and transposable elements, the fascinating hypothesis that they can move between organisms both of the same or different species has been postulated. Trans-kingdom is the term used to define the migration that occurs between species. This mechanism has been well analyzed between plants and their pests, in order to boost defense and increase pathogenicity, respectively. Intriguingly, in the last decades, the plant-human trans-kingdom migration via food intake hypothesis arose. In particular, various studies highlighted the ability of exogenous miRNAs, abundant in the mainly consumed plant-derived food, to enter the human body affecting gene expression. Notably, plant miRNAs can resist the strict conditions of the gastrointestinal tract through a methylation step that occurs during miRNA maturation, conferring high stability to these small molecules. Recent studies observed the anti-tumoral, immune modulator and anti-inflammatory abilities of trans-kingdom interaction between plant and human. Here, we depict the existing knowledge and discuss the fascinating plant-human trans-kingdom interaction, highlighting first the eventual role of plant miRNAs from foods on our somatic gene identity card and then the potential impact of using plant miRNAs as novel therapeutic avenues.

Insights into role of microRNAs in cardiac development, cardiac diseases, and developing novel therapies.

MicroRNAs (miRNAs) are a subfamily of small noncoding RNAs that play a variety of roles in regulating gene expression in nearly all organisms. They affect different biological pathways by post-transcriptionally regulating mRNAs. Aside from miRNAs’ role in maintaining cellular homeostasis, their perturbation is related to several pathologic states and diseases. Cardiovascular disorders are considered some of the most mortal multifactorial diseases that are caused by the deregulation of network of genes and effects of environmental factors. In this review, we discuss the role of miRNAs in cardiac homeostasis and malfunctions. We reviewed published research on association and role of miRNAs in cardiac development and diseases and investigated the possible links between regulatory miRNAs and different cardiac disorders. Research shows that manipulating miRNAs expression affects the integrity and functionality of the cardiovascular system. Moreover, deregulation of miRNAs, is observed in many cardiac diseases. These findings intensify the pivotal role of miRNAs in the development and specific pathological disorders of the cardiovascular system. In this review, we summarized the latest findings on the involvement of miRNAs in cardiac development, and continued by their role in congenital heart diseases and rheumatic heart disease, which are some of the leading causes of infant death and cardiovascular morbidity and mortality. Considering the significance of miRNAs in cardiac homeostasis and malfunctions, they are considered as promising therapeutic targets in cardiovascular diseases.

Transcriptome-wide identification and profiling of miRNAs in a stress-tolerant conifer Sabina chinensis

miRNAs are important regulatory components involving in many biological processes, including plant development, vegetative and reproductive growth, and stress response. However, identification and characterization of miRNAs still remain limited for conifer species. In this study, with deep sequencing, we obtained 1,314,450 unique reads with 18-30 nt length from a stress-tolerant conifer, Sabina chinensis. We identified 37 conserved and 103 novel miRNAs, their unique characteristics were further analyzed, and 10 randomly selected were validated by qRT-PCR. Through miRNA target predictions and annotations, we found miRNA may have several targets as well a target could be regulated by several miRNAs, and a total of 2,397 mRNAs were predicted to be targets of the 140 miRNAs. These targets included not only important transcription factors such as auxin response factors, but also indispensable non-transcriptional factor proteins. Pathway-based analysis showed that S. chinensis miRNAs are involved in 172 metabolic pathways, of which 3 were discovered in adaptation-related pathways, indicating their possible relevance to the species' stress-tolerance characteristics. This study is expected to lay the foundation for exploring the regulative roles of miRNAs in development, growth, and response to environmental stresses of S. chinensis.

The role of endogenous miRNAs in the development of cerebral aneurysms

Cerebral aneurysms are characterized by pathological expansion and thinning of the wall of vessels on the brain base, which may lead to rupture and subarachnoid hemorrhage (SAH) that is a life-threatening condition. This dictates the need for identification of new biological markers that predict the presence of aneurysms and the risk of their rupture. In the last decade, the role of microRNAs (miRNAs), which are considered to be key regulators of biological processes, has been investigated. miRNAs have been shown to play a role in the development of aneurysms, but today there is little similar data. In this literature review, we analyze the existing data on the role of miRNAs in development, progression, and rupture of cerebral aneurysms. We describe the relationship between miRNA expression profiles and specific molecular and cellular processes leading to the development of aneurysms. Also, we discuss the potential clinical significance of miRNAs for predicting the risk of aneurysm rupture.

Analysis of microRNA functions.

MicroRNAs (miRNAs) are small non-coding RNAs that repress the translation and reduce the stability of target mRNAs in animal cells. Post-transcriptional regulation mediated by miRNAs is a highly conserved mechanism utilized by organisms throughout phylogeny to fine tune gene expression. We document the approaches used to study the function of a single miRNA and miRNA regulation of biological pathways in the sea urchin embryo. The protocols that are described include selection of miRNA inhibitors, test of miRNA direct targets, and the use of target protector morpholinos to evaluate the impact of miRNA inhibition on its targets. Using the described techniques and strategies, the sea urchin researcher will be able to validate a miRNA's direct targets and evaluate how inhibition of the miRNA affects developmental processes. These results will contribute to our understanding of the regulatory roles of miRNAs in development.

Loss of miR-199b Impairs Active Cycling of Hematopoietic Stem Cells during Steady-State Hematopoiesis

Several recent studies have showed that dysregulation of microRNA (miRNA) expression in hematopoietic stem cells (HSC) can affect self-renewal of HSCs, and indicated a role for miRNAs in development of acute myeloid leukemia (AML). We and others have reported a significant down-regulation of miR-199b in AML patients. Recently we found that miR-199b is enriched in long-term hematopoietic stem cells (LT-HSC), suggesting that miR199-b may regulate HSCs function. Therefore, to understand the physiologic role of miR-199 in hematopoiesis during homeostasis, we evaluated various hematopoietic stem and progenitor cells (HSPC) populations in mice harboring genetic deletion of miR199b-5p using CRISPR/Cas method. We found that ablation of miR199b resulted in markedly increased frequencies of primitive HSC and MPPs, and analyses of distribution pattern in myeloid progenitor populations showed reduced numbers of common myeloid progenitors (CMPs) biased toward granulocyte-monocyte (GMPs) linage with no changes in megakaryocytic-erythroid progenitors (MEPs). The elevated numbers of HSC and MPPs may indicate that increased proportion of HSC population is actively cycling, thus we analyzed LSK populations for expression of proliferation marker Ki67 along with DNA staining. We found that miR-199b deletion reduces proportion of primitive HSC and MPPs in cell-cycle, which may affect HSC cell self-renewal. Futher cell-cycle analyses revealed that miR-199b null HSCs leave G0 faster to accumulate in G1, but rather do not progress into mitosis, which was recovered upon 5-fluorouracil-induced cytokine burst. These results indicate that loss of miR-199b increases cell cycle duration. To verify that the absence of miR-199b influences proliferation of HSCs we pulsed miR-199b KO and WT mice with BrdU for 16 hours. We found the difference in the cell cycle distribution between HSCs and progenitors, namely reduction of BrdU-positive HSC and MPPs and progression of GMP compartment. These results show that miR-199b deletion decreases HSC active cell cycle by prolonging cell cycle transition during steady-state hematopoiesis and promotes proliferation of myeloid cells. Because quiescent cells only become susceptible to 5-FU during hematopoietic stress, driving them into cycle, we injected 5-FU into miR-199 KO and WT mice once per week until hematopoietic failure occurred. We found that miR199-b KO mice died soon after two subsequent injections, most likely due to the faster HSC exhaust as compared to WT mice. These results show that loss of miR199b produces HSC with reduced quiescence and prolonged cell cycle, however upon stress these cells progress into cell cycle, making them more susceptible for 5-FU treatment. These results demonstrate that miR-199b intrinsically regulates active cycling of HSCs. CFU-S assays showed that miR-199b KO donors showed decreased colonies in spleen, suggesting that miR-199b deletion affects short-term repopulation. In long-term repopulation assay, we observed a significant reduction of HSCs compartment, but elevated numbers of MPPs in host mice transplanted with BM from miR-199 KO mice. This data indicates that loss of miR-199b causes defects in HSC self-renewal and alters HSCs reconstitution potential. To identify potential miR-199b targets in HSCs under steady-state hematopoiesis, we performed a gene profiling in SLAM-HSCs. mRNA levels of several putative miR-199b targets were markedly elevated in miR-199b KO HSCs. These genes are known to be involved in cell adhesion, cell cycle, transcription regulation and chromatin remodeling including Klf12, Tox3 and Cdk18. Our findings reveal a novel functional role for miR-199b in governing HSC maintenance. DisclosuresNo relevant conflicts of interest to declare.

Differences in Relative Levels of 88 microRNAs in Various Regions of the Normal Adult Human Brain.

Since the discovery of microRNAs (miRNAs) in the 1990s, our knowledge about their biology has grown considerably. The increasing number of studies addressing the role of miRNAs in development and in various diseases emphasizes the need for a comprehensive catalogue of accurate sequence, expression and conservation information regarding the large number of miRNAs proposed recently in all organs and tissues. The objective of this study was to provide data on the levels of miRNA expression in 15 tissues of the normal human brain. We conducted an analysis of the relative levels of 88 of the most abundantly expressed and best characterized miRNA derived postmortem from well-characterized samples of various regions of the brains from five normal individuals. The cluster analysis revealed some differences in the relative levels of these miRNAs among the brain regions studied. Such diversity can be explained by different functioning of these brain regions. We hope that the data from the current study are a resource that will be useful to our colleagues in this exciting field, as more hypotheses will be generated and tested with regard to small noncoding RNA in the human brain in healthy and disease states.

MiR miR on the wall, who's the most malignant medulloblastoma miR of them all?

microRNAs (miRNAs) have wide-ranging effects on large-scale gene regulation. As such, they play a vital role in dictating normal development, and their aberrant expression has been implicated in cancer. There has been a large body of research on the role of miRNAs in medulloblastoma, the most common malignant brain tumor of childhood. The identification of the 4 molecular subgroups with distinct biological, genetic, and transcriptional features has revolutionized the field of medulloblastoma research over the past 5 years. Despite this, the growing body of research on miRNAs in medulloblastoma has largely focused on the clinical entity of a single disease rather than the molecular subgroups. This review begins by highlighting the role of miRNAs in development and progresses to explore their myriad of implications in cancer. Medulloblastoma is characterized by increased proliferation, inhibition of apoptosis, and maintenance of stemness programs-features that are inadvertently regulated by altered expression patterns in miRNAs. This review aims to contextualize the large body of work on miRNAs within the framework of medulloblastoma subgroups. The goal of this review is to stimulate new areas of research, including potential therapeutics, within a rapidly growing field.

MicroRNA therapeutics: towards a new era for the management of cancer and other diseases.

In just over two decades since the discovery of the first microRNA (miRNA), the field of miRNA biology has expanded considerably. Insights into the roles of miRNAs in development and disease, particularly in cancer, have made miRNAs attractive tools and targets for novel therapeutic approaches. Functional studies have confirmed that miRNA dysregulation is causal in many cases of cancer, with miRNAs acting as tumour suppressors or oncogenes (oncomiRs), and miRNA mimics and molecules targeted at miRNAs (antimiRs) have shown promise in preclinical development. Several miRNA-targeted therapeutics have reached clinical development, including a mimic of the tumour suppressor miRNA miR-34, which reached phase I clinical trials for treating cancer, and antimiRs targeted at miR-122, which reached phase II trials for treating hepatitis. In this article, we describe recent advances in our understanding of miRNAs in cancer and in other diseases and provide an overview of current miRNA therapeutics in the clinic. We also discuss the challenge of identifying the most efficacious therapeutic candidates and provide a perspective on achieving safe and targeted delivery of miRNA therapeutics.

Role of circulating microRNA in hemodialyzed patients.

MicroRNA (miRNA) belongs to the family of non-coding RNAs, which posttranscriptionally regulate gene function. Moreover, accumulating evidence points to an essential role of miRNAs in development and monitoring of kidney disease, though the role of particular miRNAs in patients undergoing hemodialysis is still unclear. This might have consequences. It is possible that measuring a single miRNA in hemodialyzed patients may not provide adequate information about development of many pathological processes. The goal of this review is to highlight the current knowledge in the field of miRNAs, with a special emphasis on their circulation in hemodialyzed patients.

Roles of microRNAs in cancers and development.

MicroRNAs (miRNAs) are small noncoding RNA molecules thought to play an important role in regulating gene expression. Although knowledge of the biological functions of most miRNAs is still limited, miRNAs are thought to regulate the gene expression in various diseases and embryo development. In this chapter, the roles of miRNAs in human cancers are first examined from the viewpoint of up- and downregulation. Oncogenic miRNAs are involved in the overexpression/upregulation of cancers, whereas suppressive miRNAs are involved in the underexpression/downregulation of cancers. Statistical analysis of the positional nucleotide occurrence features of miRNAs revealed differences between the positional nucleotide occurrences of oncogenic and suppressive miRNAs. A miRNA gene-silencing score was then defined on the basis of the higher and lower levels of the statistical significances of positional nucleotides. Since the miRNA scores were closely related to miRNA frequencies, a method using the scores and nucleotide frequencies to distinguish whether a new miRNA is oncogenic or suppressive is proposed. This chapter also describes the roles of miRNAs in development. As miRNAs can act as cis-regulatory elements in the early embryonic development of Drosophila melanogaster, it is proposed that they mediate signal transduction between genes.

MicroRNA in teleost fish.

MicroRNAs (miRNAs) are transcriptional and posttranscriptional regulators involved in nearly all known biological processes in distant eukaryotic clades. Their discovery and functional characterization have broadened our understanding of biological regulatory mechanisms in animals and plants. They show both evolutionary conserved and unique features across Metazoa. Here, we present the current status of the knowledge about the role of miRNA in development, growth, and physiology of teleost fishes, in comparison to other vertebrates. Infraclass Teleostei is the most abundant group among vertebrate lineage. Fish are an important component of aquatic ecosystems and human life, being the prolific source of animal proteins worldwide and a vertebrate model for biomedical research. We review miRNA biogenesis, regulation, modifications, and mechanisms of action. Specific sections are devoted to the role of miRNA in teleost development, organogenesis, tissue differentiation, growth, regeneration, reproduction, endocrine system, and responses to environmental stimuli. Each section discusses gaps in the current knowledge and pinpoints the future directions of research on miRNA in teleosts.

In silico identification and characterization of conserved miRNAs and their target genes in sweet potato (Ipomoea batatas L.) Expressed Sequence Tags (ESTs)

The endogenous small non-coding micro RNAs (miRNAs), which are typically ~21–24 nt nucleotides, play a crucial role in regulating the intrinsic normal growth of cells and development of the plants as well as in maintaining the integrity of genomes. These small non-coding RNAs function as the universal specificity factors in post-transcriptional gene silencing. Discovering miRNAs, identifying their targets, and further inferring miRNA functions is a routine process to understand normal biological processes of miRNAs and their roles in the development of plants. Comparative genomics based approach using expressed sequence tags (EST) and genome survey sequences (GSS) offer a cost-effective platform for identification and characterization of miRNAs and their target genes in plants. Despite the fact that sweet potato (Ipomoea batatas L.) is an important staple food source for poor small farmers throughout the world, the role of miRNA in various developmental processes remains largely unknown. In this paper, we report the computational identification of miRNAs and their target genes in sweet potato from their ESTs. Using comparative genomics-based approach, 8 potential miRNA candidates belonging to miR168, miR2911, and miR156 families were identified from 23 406 ESTs in sweet potato. A total of 42 target genes were predicted and their probable functions were illustrated. Most of the newly identified miRNAs target transcription factors as well as genes involved in plant growth and development, signal transduction, metabolism, defense, and stress response. The identification of miRNAs and their targets is expected to accelerate the pace of miRNA discovery, leading to an improved understanding of the role of miRNA in development and physiology of sweet potato, as well as stress response.

MicroRNAs: history, biogenesis, and their evolving role in animal development and disease.

The discovery of microRNAs (miRNAs) in 1993 followed by developments and discoveries in small RNA biology have redefined the biological landscape by significantly altering the longstanding dogmas that defined gene regulation. These small RNAs play a significant role in modulation of an array of physiological and pathological processes ranging from embryonic development to neoplastic progression. Unique miRNA signatures of various inherited, metabolic, infectious, and neoplastic diseases have added a new dimension to the studies that look at their pathogenesis and highlight their potential to be reliable biomarkers. Also, altering miRNA functionality and the development of novel in vivo delivery systems to achieve targeted modulation of specific miRNA function are being actively pursued as novel approaches for therapeutic intervention in many diseases. Here we review the current body of knowledge on the role of miRNAs in development and disease and discuss future implications.

MiRNAs in development and pathogenesis of the nervous system

The human nervous system expresses approximately 70% of all miRNAs (microRNAs). Changing levels of certain ubiquitous and brain-specific miRNAs shape the development and function of the nervous system. It is becoming clear that misexpression of some miRNAs can contribute towards neurodevelopmental disorders. In the present article, we review the current knowledge of the role of miRNAs in development and pathogenesis of the nervous system.

MicroRNAs as Diagnostic and Therapeutic Targets in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic devastating disease of the central nervous system (CNS), which is reported to be the most common neuroinflammatory disorder of the young adults. Although the underlying etiology of MS is not completely elucidated, the number of patients and burden to societies increases worldwide. There are several CNS disorders that might have overlapping phenotypic manifestations with MS; therefore, reliable and accessible diagnostic test is highly desirable for differential diagnosis. MicroRNAs (miRNAs) are small regulatory RNAs that are proven to be master regulators of gene expression. Recently, several studies have shown potential roles for miRNAs in development, hemostasis and maturation of immune system, suggesting possible involvement of these regulatory elements in autoimmune diseases, such as MS. We reviewed recent literature to explore miRNAs that are reported to be involved in pathogenesis of MS and found some miRNAs that might have potentials as being diagnostic biomarkers.

The role of noncoding RNA in thyroid cancer.

Increasing noncoding RNAs (ncRNAs) were found to show abnormal expression patterns in various human cancers. Based on size, ncRNAs are generally grouped into two categories, short noncoding RNAs and long noncoding RNAs (lncRNAs) of greater than 200 nt. Small noncoding RNAs include microRNAs, piRNAs, snoRNAs, and endogenous siRNAs, out of the role of miRNAs in development and cancer biology has been extensively studied. In contrast to small noncoding RNAs like miRNAs, long noncoding RNAs are much less known concerning their functions in human cancers especially in thyroid cancer. The present review highlighted the roles of miRNAs and newly discovered lncRNAs in thyroid development, tumorigenesis, metastasis, and their clinical implication.

P1.27 Lung Tumors to Brain Metastases: Do Micrornas Play a Prognostic Role?

ABSTRACT More than 50% of cerebral tumors are metastatic in origin. Lung cancer is the most frequently diagnosed malignant tumor and the leading cause of cancer related mortality around the world. Non-small-cell lung cancer (NSCLC), account for 85% of all lung cancer and cerebral metastases from NSCLC are diagnosed in 30-50% of patients, significantly affecting the morbility and mortality. Both the molecular characteristics of the metastatic cells and the microenvironment of the Central Nervous System (CNS) seem to play a relevant role to favor their survival, their growth and their resistance to systemic therapies. The appearance of secondary brain lesions is a complex multi-step process genetically mediated through the inactivation of tumor suppressor genes and activation of oncogens. Currently few instruments are available to identify patients who potentially present major risks to develop brain metastases. Certain miRNAs have been involved as promoters or suppressors of oncogenes and there is growing evidence that their activity may also play a crucial role in developing tumor metastasis possibly influencing multiple aspects of the “metastatic cascade”like cell migration, invasion and extravasation. Therefore, characterization and identification of differences between molecular signature of expression of miRNAs in normal tissue, tumoral and metastatic cells may be important to elucidate the specific role of different miRNAs in development of tumors and to identify the gene and the signal sequences which they control. The aim of our study was to analyze and compare, in a matched series of FFPE tissues from patients affected by NSCLC, the miRNAs expression profiles of primitive tumors and their matched brain metastases. The goals were: a) to select miRNAs whose expression could be correlated to an increased risk to develop cerebral metastases; b) to identify differences between primitive and metastatic tumor tissues which may explain this secondary diffusion and therefore display a prognostic significance. The results obtained from these analysis will be discussed.

Noncoding RNAs Involved in Mammary Gland Development and Tumorigenesis: There’s a Long Way to Go

The mammalian genome encodes thousands of noncoding RNAs. These noncoding transcripts are broadly categorized into short noncoding RNAs, such as microRNAs (miRNAs), and long noncoding RNAs (lncRNAs) of greater than 200 nt. While the role of miRNAs in development and cancer biology has been extensively studied, much less is known about the vast majority of noncoding transcripts represented by lncRNAs. LncRNAs are emerging as key regulators of developmental processes and as such, their frequent misregulation in tumorigenesis and disease in not unexpected. The role of lncRNAs in mammary gland development and breast cancer is just beginning to be elucidated. This review will discuss the role of lncRNAs in mammalian and mammary gland development. In addition, we will review the contributions of lncRNAs to the stepwise progression of tumorigenesis, highlighting the role of lncRNAs in breast cancer.

MicroRNA gene expression signatures in the developing neural tube

Neurulation requires precise, spatio-temporal expression of numerous genes and coordinated interaction of signal transduction and gene regulatory networks, disruption of which may contribute to the etiology of neural tube defects (NTDs). MicroRNAs (miRNAs) are key modulators of cell and tissue differentiation. To define potential roles of miRNAs in development of the murine neural tube (NT), miRNA microarray analysis was conducted to establish expression profiles, and identify miRNA target genes and functional gene networks. The miRNA expression profiles in murine embryonic NTs derived from gestational days 8.5, 9.0, and 9.5 were defined and compared utilizing miRXplore microarrays from Miltenyi Biotec GmbH, Bergisch Gladbach, Germany. Gene expression changes were verified by TaqMan quantitative Real-Time PCR. The clValid R package and the UPGMA (hierarchical) clustering method were utilized for cluster analysis of the microarray data. Functional associations among selected miRNAs were examined via Ingenuity Pathway Analysis. The miRXplore chips enabled examination of 609 murine miRNAs. Expression of approximately 12% of these was detected in murine embryonic NTs. Clustering analysis revealed several developmentally regulated expression clusters among these expressed genes. Target analysis of differentially expressed miRNAs enabled identification of numerous target genes associated with cellular processes essential for normal NT development. Utilization of Ingenuity Pathway Analysis revealed interactive biologic networks which connected differentially expressed miRNAs with their target genes, and highlighted functional relationships. The present study defined unique gene expression signatures of a range of miRNAs in the developing NT during the critical period of NT morphogenesis. Analysis of miRNA target genes and gene interaction pathways revealed that specific miRNAs might direct expression of numerous genes encoding proteins, which have been shown to be indispensable for normal neurulation. This study is the first to identify miRNA expression profiles and their potential regulatory networks in the developing mammalian NT.