Expression of miR-15/107 Family MicroRNAs in Human Tissues and Cultured Rat Brain Cells

The miR-15/107 family comprises a group of 10 paralogous microRNAs （miRNAs）,sharing a 5＇ AGCAGC sequence.These miRNAs have overlapping targets.In order to characterize the expression of miR-15/107 family miRNAs,we employed customized TaqMan Low-Density micro-fluid PCR-array to investigate the expression of miR-15/107 family members,and other selected miRNAs,in 11 human tissues obtained at autopsy including the cerebral cortex,frontal cortex,primary visual cortex,thalamus,heart,lung,liver,kidney,spleen,stomach and skeletal muscle.miR-103,miR-195 and miR-497 were expressed at similar levels across various tissues,whereas miR-107 is enriched in brain samples.We also examined the expression patterns of evolutionarily conserved miR-15/107 miRNAs in three distinct primary rat brain cell preparations （enriched for cortical neurons,astrocytes and microglia,respectively）.In primary cultures of rat brain cells,several members of the miR-15/107 family are enriched in neurons compared to other cell types in the central nervous system （CNS）.In addition to mature miRNAs,we also examined the expression of precursors （pri-miRNAs）.Our data suggested a generally poor correlation between the expression of mature miRNAs and their precursors.In summary,we provide a detailed study of the tissue and cell type-specific expression profile of this highly expressed and phylogenetically conserved family of miRNA genes.     

The miR-15/107 Group of MicroRNA Genes: Evolutionary Biology, Cellular Functions, and Roles in Human Diseases

The miR-15/107 group of microRNA (miRNA) gene is increasingly appreciated to serve key functions in humans. These miRNAs regulate gene expression involved in cell division, metabolism, stress response, and angiogenesis in vertebrate species. The miR-15/107 group has also been implicated in human cancers, cardiovascular disease and neurodegenerative disease, including Alzheimer's disease. Here we provide an overview of the following: (1) the evolution of miR-15/107 group member genes; (2) the expression levels of miRNAs in mammalian tissues; (3) evidence for overlapping gene-regulatory functions by different miRNAs; (4) the normal biochemical pathways regulated by miR-15/107 group miRNAs; and (5) the roles played by these miRNAs in human diseases. Membership in this group is defined based on sequence similarity near the mature miRNAs' 5′ end: all include the sequence AGCAGC. Phylogeny of this group of miRNAs is incomplete; thus, a definitive taxonomic classification (e.g., designation as a “superfamily”) is currently not possible. While all vertebrates studied to date express miR-15a, miR-15b, miR-16, miR-103, and miR-107, mammals alone are known to express miR-195, miR-424, miR-497, miR-503, and miR-646. Multiple different miRNAs in the miR-15/107 group are expressed at moderate to high levels in human tissues. We present data on the expression of all known miR-15/107 group members in human cerebral cortical gray matter and white matter using new miRNA profiling microarrays. There is extensive overlap in the mRNAs targeted by miR-15/107 group members. We show new data from cultured H4 cancer cells that demonstrate similarities in mRNAs targeted by miR-16 and miR-103 and also support the importance of the mature miRNAs' 5′ seed region in mRNA target recognition. In conclusion, the miR-15/107 group of miRNA genes is a fascinating topic of study for evolutionary biologists, miRNA biochemists, and clinically oriented translational researchers alike.     

微小RNA与胃癌的关系

微小RNA（microRNA、miRNA）与胃癌的发生发展可通过调控其靶基因参与的信号传导通路,影响胃癌的发生、侵袭和转移等过程,发挥着类似于癌基因或抑癌基因的作用。目前,已发现多种microR—NA与胃癌关系密切,包括通过调节周期蛋白依赖性蛋白激酶（Cdk）表达影响胃癌细胞增殖的miR-106b-93～25家族、miR-222—221家族和抑制高迁移率族蛋白A2（HMGA2）基因表达抑制胃癌细胞转移的miR-129和let-一7miRNA家族等。另有研究表明,miR-d21和miR-31检测阳性率显著高于血清CEA,可能成为新的胃癌肿瘤标志物。miR-15b和miR-16与胃癌多药耐药的关系也说明microRNA可能成为胃癌治疗新的靶点。     

miR-193: A new weapon against cancer

microRNAs (miRNAs) are known as a large group of short noncoding RNAs, which structurally consist of 19–22 nucleotides in length and functionally act as one of the main regulators of gene expression in important biological and physiological contexts like cell growth, apoptosis, proliferation, differentiation, movement (cell motility), and angiogenesis as well as disease formation and progression importantly in cancer cell invasion, migration, and metastasis. Among these notable tiny molecules, many studies recently presented the important role of the miR-193 family comprising miR-193a-3p, miR-193a-5p, miR-193b-3p, and miR-193b-5p in health and disease biological processes by interaction with special targeting and signaling, which mainly contribute as a tumor suppressor. Therefore, in the present paper, we review the functional role of this miRNA family in both health and disease conditions focusing on various tumor developments, diagnoses, prognoses, and treatment.     

MicroRNAs differentially expressed in postnatal aortic development downregulate elastin via 3' UTR and coding-sequence binding sites

Elastin production is characteristically turned off during the maturation of elastin-rich organs such as the aorta. MicroRNAs (miRNAs) are small regulatory RNAs that down-regulate target mRNAs by binding to miRNA regulatory elements (MREs) typically located in the 3' UTR. Here we show a striking up-regulation of miR-29 and miR-15 family miRNAs during murine aortic development with commensurate down-regulation of targets including elastin and other extracellular matrix (ECM) genes. There were a total of 14 MREs for miR-29 in the coding sequences (CDS) and 3' UTR of elastin, which was highly significant, and up to 22 miR-29 MREs were found in the CDS of multiple ECM genes including several collagens. This overrepresentation was conserved throughout mammalian evolution. Luciferase reporter assays showed synergistic effects of miR-29 and miR-15 family miRNAs on 3' UTR and coding-sequence elastin constructs. Our results demonstrate that multiple miR-29 and miR-15 family MREs are characteristic for some ECM genes and suggest that miR-29 and miR-15 family miRNAs are involved in the down-regulation of elastin in the adult aorta.     

A Functional Screen Identifies Specific MicroRNAs Capable of Inhibiting Human Melanoma Cell Viability

Malignant melanoma is an aggressive form of skin cancer with poor prognosis. Despite improvements in awareness and prevention of this disease, its incidence is rapidly increasing. MicroRNAs (miRNAs) are a class of small RNA molecules that regulate cellular processes by repressing messenger RNAs (mRNAs) with partially complementary target sites. Several miRNAs have already been shown to attenuate cancer phenotypes, by limiting proliferation, invasiveness, tumor angiogenesis, and stemness. Here, we employed a genome-scale lentiviral human miRNA expression library to systematically survey which miRNAs are able to decrease A375 melanoma cell viability. We highlight the strongest inhibitors of melanoma cell proliferation, including the miR-15/16, miR-141/200a and miR-96/182 families of miRNAs and miR-203. Ectopic expression of these miRNAs resulted in long-term inhibition of melanoma cell expansion, both in vitro and in vivo. We show specifically miR-16, miR-497, miR-96 and miR-182 are efficient effectors when introduced as synthetic miRNAs in several melanoma cell lines. Our study provides a comprehensive interrogation of miRNAs that interfere with melanoma cell proliferation and viability, and offers a selection of miRNAs that are especially promising candidates for application in melanoma therapy.     

MicroRNA in leukemia: Tumor suppressors and oncogenes with prognostic potential

Leukemia is known as a progressive malignant disease, which destroys the blood-forming organs and results in adverse effects on the proliferation and development of leukocytes and their precursors in the blood and bone marrow. There are four main classes of leukemia including acute leukemia, chronic leukemia, myelogenous leukemia, and lymphocytic leukemia. Given that a variety of internal and external factors could be associated with the initiation and progression of different types of leukemia. One of the important factors is epigenetic regulators such as microRNAs (miRNAs) and long noncoding RNAs (ncRNA). MiRNAs are short ncRNAs which act as tumor suppressor (i.e., miR-15, miR-16, let-7, and miR-127) or oncogene (i.e., miR-155, miR-17-92, miR-21, miR-125b, miR-93, miR-143-p3, miR-196b, and miR-223) in leukemia. It has been shown that deregulation of these molecules are associated with the initiation and progression of leukemia. Hence, miRNAs could be used as potential therapeutic candidates in the treatment of patients with leukemia. Moreover, increasing evidence revealed that miRNAs could be used as diagnostic and prognostic biomarkers in monitoring patients in early stages of disease or after received chemotherapy regimen. It seems that identification and development of new miRNAs could pave to the way to the development new therapeutic platforms for patients with leukemia. Here, we summarized various miRNAs as tumor suppressor and oncogene which could be introduced as therapeutic targets in treatment of leukemia.     

microRNAs in the regulation of adipogenesis and obesity

Worldwide obesity is a growing health problem, associated with increased risk of chronic disease. Understanding the molecular basis of adipogenesis and fat cell development in obesity is essential to identify new biomarkers and therapeutic targets for the development of anti-obesity drugs. microRNAs (miRNAs) appear to play regulatory roles in many biological processes associated with obesity, including adipocyte differentiation, insulin action and fat metabolism. Recent studies show miRNAs are dysregulated in obese adipose tissue. During adipogenesis miRNAs can accelerate or inhibit adipocyte differentiation and hence regulate fat cell development. In addition miRNAs may regulate adipogenic lineage commitment in multipotent stem cells and hence govern fat cell numbers. Recent findings suggest miR-519d may be associated with human obesity, but larger case-control studies are needed. Few miRNA targets have been experimentally validated in adipocytes but interestingly both miR-27 and miR-519d target PPAR family members, which are well established regulators of fat cell development. In this review recent advances in our understanding of the role of miRNAs in fat cell development and obesity are discussed. The potential of miRNA based therapeutics targeting obesity is highlighted as well as recommendations for future research which could lead to a breakthrough in the treatment of obesity.     

Identifying MicroRNAs Involved in Degeneration of the Organ of Corti during Age-Related Hearing Loss

MicroRNAs (miRNAs), a class of short non-coding RNAs that regulate the expression of mRNA targets, are important regulators of cellular senescence and aging. We questioned which miRNAs are involved in age-related degeneration of the organ of Corti (OC), the auditory sensory epithelium that transduces mechanical stimuli to electrical activity in the inner ear. Degeneration of the OC is generally accepted as the main cause of age-related hearing loss (ARHL), a progressive loss of hearing in individuals as they grow older. To determine which miRNAs are involved in the onset and progression of ARHL, miRNA gene expression in the OC of two mouse strains, C57BL/6J and CBA/J, was compared at three different ages using GeneChip miRNA microarray and was validated by real-time PCR. We showed that 111 and 71 miRNAs exhibited differential expression in the C57 and CBA mice, respectively, and that downregulated miRNAs substantially outnumbered upregulated miRNAs during aging. miRNAs that had approximately 2-fold upregulation included members of miR-29 family and miR-34 family, which are known regulators of pro-apoptotic pathways. In contrast, miRNAs that were downregulated by about 2-fold were members of the miR-181 family and miR-183 family, which are known to be important for proliferation and differentiation, respectively. The shift of miRNA expression favoring apoptosis occurred earlier than detectable hearing threshold elevation and hair cell loss. Our study suggests that changes in miRNA expression precede morphological and functional changes, and that upregulation of pro-apoptotic miRNAs and downregulation of miRNAs promoting proliferation and differentiation are both involved in age-related degeneration of the OC.     

microRNA-378 与相关疾病的研究进展

microRNAs是一类内源性表达的、长度约为22个核苷酸的非蛋白编码的单链RNA分子,是重要的转录后基因表达调控因子。在多种生理和病理过程中发挥重要作用,到目前为止,在动植物以及病毒中已经发现有24521个miRNA分子,miR-378是其中的一种,miR-378通过多种机制与众多疾病的发生发展密切相关。miR-378在不同肿瘤组织中起到不同作用,在胃癌,肝癌,结直肠癌等肿瘤中起到抑癌基因的作用,在白血病,胰腺癌,卵巢癌等肿瘤中起到癌基因的作用。在心血管方面,miR-378可以通过多种机制起到保护血管,延缓心血管疾病的发展。在骨代谢方面,miR-378可通过不同机制抑制或促进成骨细胞的分化。本文就其与肿瘤、心血管、骨代谢以及其他方面的研究进行介绍,为这些疾病的治疗和预防提供一种新的思路。     

miR-26家族与肿瘤关系的研究进展

miR-26家族是由miR-26a、miR-26b、miR-1297及miR-4465等序列相似、结构相仿、种子区序列相同(UCAAGUA)的微小RNA(microRNAs,miRNAs)组成。多种组织细胞分化过程中伴有mi R-26家族表达的增加,其异常表达与特发性肺纤维化、原发性胆汁性肝硬化、多发性硬化及阿尔茨海默病等有关。近年研究报道,多种肿瘤组织亦存在mi R-26基因表达紊乱,并与肿瘤的发生发展密切相关。就miR-26家族及其调控的靶基因与肿瘤关系的研究进展进行综述。     

Tumor-Suppressing Effects of miR-141 in Human Osteosarcoma

Osteosarcoma is the most common primary malignancy to arise from bone. The pathogenesis of osteosarcoma is unclear, and new therapy molecular target is needed. The miRNAs researched suggested that miRNAs are involved in the pathogenesis of osteosarcoma. MiR-141, which belong to miR-200 family, take a part in tumorigenesis. However, the role of miR-141 in the pathogenesis of osteosarcoma remained unclear. In this study, we focused on the miR-141 in osteosarcoma and found that the expression of miR-141 is lower in osteosarcoma. Overexpression of miR-141 not only inhibits osteosarcoma cell proliferation but also induces cell apoptosis. It is estimated that miR-141 played its role via ZEB1 and ZEB2. In all, miR-141 played a osteosarcoma-suppressing role via ZEB1 and ZEB2. Our finding may elucidate the miRNAs mechanism in osteosarcoma and provide a new molecule target for osteosarcoma therapy.     

A miRNA signature of prion induced neurodegeneration

MicroRNAs (miRNAs) are small, non-coding RNA molecules which are emerging as key regulators of numerous cellular processes. Compelling evidence links miRNAs to the control of neuronal development and differentiation, however, little is known about their role in neurodegeneration. We used microarrays and RT-PCR to profile miRNA expression changes in the brains of mice infected with mouse-adapted scrapie. We determined 15 miRNAs were de-regulated during the disease processes; miR-342-3p, miR-320, let-7b, miR-328, miR-128, miR-139-5p and miR-146a were over 2.5 fold up-regulated and miR-338-3p and miR-337-3p over 2.5 fold down-regulated. Only one of these miRNAs, miR-128, has previously been shown to be de-regulated in neurodegenerative disease. De-regulation of a unique subset of miRNAs suggests a conserved, disease-specific pattern of differentially expressed miRNAs is associated with prion-induced neurodegeneration. Computational analysis predicted numerous potential gene targets of these miRNAs, including 119 genes previously determined to be also de-regulated in mouse scrapie. We used a co-ordinated approach to integrate miRNA and mRNA profiling, bioinformatic predictions and biochemical validation to determine miRNA regulated processes and genes potentially involved in disease progression. In particular, a correlation between miRNA expression and putative gene targets involved in intracellular protein-degradation pathways and signaling pathways related to cell death, synapse function and neurogenesis was identified.     

miR-21: a small multi-faceted RNA

More than 1000 microRNAs (miRNAs) are expressed in human cells, some tissue or cell type specific, others considered as house-keeping molecules. Functions and direct mRNA targets for some miRNAs have been relatively well studied over the last years. Every miRNA potentially regulates the expression of numerous protein-coding genes (tens to hundreds), but it has become increasingly clear that not all miRNAs are equally important; diverse high-throughput screenings of various systems have identified a limited number of key functional miRNAs over and over again. Particular miRNAs emerge as principal regulators that control major cell functions in various physiological and pathophysiological settings. Since its identification 3 years ago as the miRNA most commonly and strongly up-regulated in human brain tumour glioblastoma [ 1 ], miR-21 has attracted the attention of researchers in various fields, such as development, oncology, stem cell biology and aging, becoming one of the most studied miRNAs, along with let-7, miR-17–92 cluster ('oncomir-1'), miR-155 and a few others. However, an miR-21 knockout mouse has not yet been generated, and the data about miR-21 functions in normal cells are still very limited. In this review, we summarise the current knowledge of miR-21 functions in human disease, with an emphasis on its regulation, oncogenic role, targets in human cancers, potential as a disease biomarker and novel therapeutic target in oncology.     

miRNA profiling of naïve, effector and memory CD8 T cells

microRNAs have recently emerged as master regulators of gene expression during development and cell differentiation. Although profound changes in gene expression also occur during antigen-induced T cell differentiation, the role of miRNAs in the process is not known. We compared the miRNA expression profiles between antigen-specific na?ve, effector and memory CD8+ T cells using 3 different methods--small RNA cloning, miRNA microarray analysis and real-time PCR. Although many miRNAs were expressed in all the T cell subsets, the frequency of 7 miRNAs (miR-16, miR-21, miR-142-3p, miR-142-5p, miR-150, miR-15b and let-7f) alone accounted for approximately 60% of all miRNAs, and their expression was several fold higher than the other expressed miRNAs. Global downregulation of miRNAs (including 6/7 dominantly expressed miRNAs) was observed in effector T cells compared to na?ve cells and the miRNA expression levels tended to come back up in memory T cells. However, a few miRNAs, notably miR-21 were higher in effector and memory T cells compared to na?ve T cells. These results suggest that concomitant with profound changes in gene expression, miRNA profile also changes dynamically during T cell differentiation. Sequence analysis of the cloned mature miRNAs revealed an extensive degree of end polymorphism. While 3'end polymorphisms dominated, heterogeneity at both ends, resembling drosha/dicer processing shift was also seen in miR-142, suggesting a possible novel mechanism to generate new miRNA and/or to diversify miRNA target selection. Overall, our results suggest that dynamic changes in the expression of miRNAs may be important for the regulation of gene expression during antigen-induced T cell differentiation. Our study also suggests possible novel mechanisms for miRNA biogenesis and function.     

Aberrant expression of oncogenic and tumor-suppressive microRNAs in cervical cancer is required for cancer cell growth

MicroRNAs (miRNAs) play important roles in cancer development. By cloning and sequencing of a HPV16(+) CaSki cell small RNA library, we isolated 174 miRNAs (including the novel miR-193c) which could be grouped into 46 different miRNA species, with miR-21, miR-24, miR-27a, and miR-205 being most abundant. We chose for further study 10 miRNAs according to their cloning frequency and associated their levels in 10 cervical cancer- or cervical intraepithelial neoplasia-derived cell lines. No correlation was observed between their expression with the presence or absence of an integrated or episomal HPV genome. All cell lines examined contained no detectable miR-143 and miR-145. HPV-infected cell lines expressed a different set of miRNAs when grown in organotypic raft cultured as compared to monolayer cell culture, including expression of miR-143 and miR-145. This suggests a correlation between miRNA expression and tissue differentiation. Using miRNA array analyses for age-matched normal cervix and cervical cancer tissues, in combination with northern blot verification, we identified significantly deregulated miRNAs in cervical cancer tissues, with miR-126, miR-143, and miR-145 downregulation and miR-15b, miR-16, miR-146a, and miR-155 upregulation. Functional studies showed that both miR-143 and miR-145 are suppressive to cell growth. When introduced into cell lines, miR-146a was found to promote cell proliferation. Collectively, our data indicate that downregulation of miR-143 and miR-145 and upregulation of miR-146a play a role in cervical carcinogenesis.     

Conservation of miR-15a/16-1 and miR-15b/16-2 clusters

MiR-15a/16-1 and miR-15b/16-2 clusters have been shown to play very important roles in regulating cell proliferation and apoptosis by targeting cell cycle proteins and the antiapoptotic Bcl-2 gene. However, the physiological implications of those two clusters are largely elusive. By aligning the primary miR-15a/16-1 sequence among 44 vertebrates, we found that there was a gap in the homologous region of the rat genome. To verify that there was a similar miR-15a/16-1 cluster in rats, we amplified this region from rat genomic DNA using PCR and found that a 697-bp sequence was missing in the current rat genome database, which covers the miR-15a/16-1 cluster. Subsequently, we also investigated the expression pattern of individual miRNAs spliced from miR-15a/16-1 and miR-15b/16-2 clusters, including miR-15a, miR-15a*, miR-15b, miR-15b*, miR-16-1/2, and miR-16-1/2* from various rat tissues, and found that all of those miRNAs were expressed in the investigated tissues. MiR-16 was most expressed in the heart, followed by the brain, lung, kidney, and small intestine, which indicates tissue specificity for individual miRNA expression from both clusters. Our results demonstrated that both miR-15a/16-1 and miR-15b/16-2 clusters are highly conserved among mammalian species. The investigation of the biological functions of those two clusters using transgenic or knockout/knockdown models will provide new clues to understanding their implications in human diseases and finding a new approach for miRNA-based therapy.