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Resumen El carcinoma tipo-linfoepitelioma pulmonar es una variante rara de carcinoma de células no pequeñas de pulmón, representa aproximadamente 0.7% de todos los casos. Está usualmente asociado con la infección por el virus de Epstein-Barr y es más prevalente en el Sureste de Asia; sin embargo, es extremadamente raro en Améri ca Latina. Informamos el caso de un hombre de 65 años de edad con un carcinoma tipo-linfoepitelioma pulmo nar, que se presentó con tos, disnea y pérdida de peso. La TAC de tórax mostró nódulo mal definido localizado en el pulmón derecho. Se realizó biopsia transtorácica de la lesión, y el estudio microscópico reveló células gran des poligonales dispuestas en mantos, infiltrados por abundantes linfocitos y células plasmáticas, alrededor del intersticio. Las células neoplásicas fueron positivas para citoqueratina 5/6 y p63, y negativas para Napsina A y el factor de transcripción tiroideo 1 (TTF-1). La expre sión de PD-L1 fue positivo (aproximadamente 100%) por inmunohistoquímica; así como el núcleo de las células neoplásicas mediante hibridación in situ para el RNA codificado por el virus de Epstein-Barr (EBER-ISH). El paciente recibió seis ciclos de un esquema combinado de quimioterapia basado en platino (gencitabina/cisplatino) más durvalumab. Presentó progresión de la enfermedad y finalmente murió 9 meses después del diagnóstico.
Abstract Pulmonary lymphoepithelioma-like carcinoma is a rare type of non-small cell lung cancer, it accounts for approximately 0.7% of all cases. It is usually associated with Epstein-Barr virus infection and is more prevalent in Southeast Asia; however, it is extremely rare in Latin America. We present a 65-year-old man with a primary pulmonary lymphoepithelioma-like carcinoma, who presented with cough, dyspnoea and weight loss. Com puter tomographic scan of the thorax showed a nodule localized in the right lung. A transthoracic biopsy of the lung lesion was made and the microscopic obser vation revealed large polygonal cells that proliferated in a nest pattern with infiltration by lymphocytes and plasma cells around the interstitium. The tumour cells were positive for citokeratin 5/6 and p63, and negative for Napsin A and thyroid transcription factor 1 (TTF-1). PD-L1 expression was positive (approximately 100%) in the immunohistochemical study, and the nuclei of the tumour cells were positive for EBV-encoded small RNA in-situ hybridization (EBER-ISH). The patient underwent six cycles of platinum-based combination (gencitabine/ carboplatin) chemotherapy plus durvalumab. He pre sented progression of the disease and finally he died 9 months after diagnosis.
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tRNA-derived small RNAs (tsRNAs) are novel non-coding RNAs that are involved in the occurrence and progression of diverse diseases. However, their exact presence and function in hepatocellular carcinoma (HCC) remain unclear. Here, differentially expressed tsRNAs in HCC were profiled. A novel tsRNA, tRNAGln-TTG derived 5'-tiRNA-Gln, is significantly downregulated, and its expression level is correlated with progression in patients. In HCC cells, 5'-tiRNA-Gln overexpression impaired the proliferation, migration, and invasion in vitro and in vivo, while 5'-tiRNA-Gln knockdown yielded opposite results. 5'-tiRNA-Gln exerted its function by binding eukaryotic initiation factor 4A-I (EIF4A1), which unwinds complex RNA secondary structures during translation initiation, causing the partial inhibition of translation. The suppressed downregulated proteins include ARAF, MEK1/2 and STAT3, causing the impaired signaling pathway related to HCC progression. Furthermore, based on the construction of a mutant 5'-tiRNA-Gln, the sequence of forming intramolecular G-quadruplex structure is crucial for 5'-tiRNA-Gln to strongly bind EIF4A1 and repress translation. Clinically, 5'-tiRNA-Gln expression level is negatively correlated with ARAF, MEK1/2, and STAT3 in HCC tissues. Collectively, these findings reveal that 5'-tiRJNA-Gln interacts with EIF4A1 to reduce related mRNA binding through the intramolecular G-quadruplex structure, and this process partially inhibits translation and HCC progression.
Subject(s)
Humans , Carcinoma, Hepatocellular/pathology , Liver Neoplasms/pathology , Eukaryotic Initiation Factor-4A/genetics , Cell Line , RNA, Transfer/metabolism , RNA , Cell ProliferationABSTRACT
With the development of sequencing technology and in-depth research on tRNA-derived small molecules (tsRNAs)‚ more and more tRNAs and their functions have been identified in various species. tsRNAs can be divided into tRNA-derived fragment (tRF) and tRNA-derived stress-induced RNA (tiRNA) according to different cleavage sites. And we will focus on tRF‚ which is a kind of non-coding RNA with regulatory function. To deepen the research of tRF‚ a large number of tRF identification methods based on sequencing data and corresponding databases are being constructed in recent years. The former mainly includes the method of Telonis et al. and tDRmapper‚ while the latter mainly includes tRFdb‚ tRF2Cancer and MINTbase. At the same time‚ both provide a more effective tool for the in-depth research of tRF. The regulation mechanisms of tRF are also being illustrated in many studies. tRF mainly regulates the expression of RNA‚ DNA and proteins in a miRNA-like manner. With further investigations‚ researchers have found that tRF also plays a specific regulatory role in various biological processes of human diseases‚ suggesting its role as a potential biomarker. Herein we mainly summarize the identification methods‚ databases‚ regulation mechanisms of tRF and its role in human diseases.
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【Objective】 To investigate the changes of platelet microRNA (miRNA) expression profiles of storage in vitro, and to explore the molecular mechanism of miRNAs involved in the regulation of platelet storage lesion (PSL). 【Methods】 20 platelet samples (5 mL / sample) were collected from apheresis platelet donors, fully mixed and stored in a shaker with (22±2) ℃ horizontal agitation, sampled on day 1 and day 5, and sequenced by DNA nanoball (DNB) sequencing technology. The miRNAs with more than 2 times expressions (P<0.01) were considered as significantly differences between d5 and d1 groups. The miRanda and TargetScan softwares were used to predict the target genes. Gene Ontology (GO) function enrichment analysis and Kyoto Encyclopedia of genes and genomes (KEGG) pathway enrichment analysis were performed on the target genes of significant differentially expressed miRNAs. The expression of miRNAs was verified by real-time fluorescence quantitative PCR (qRT-PCR). 【Results】 Compared with d1 group, 315 miRNAs with significantly different expression (P<0.01) were screened in d5 group, including 146 up-regulated miRNAs (such as miR-146a, let-7b), and 169 down-regulated miRNAs (such as mir-30d, mir-142). Among 126 known miRNAs, 43 were up-regulated and 83 were down-regulated. There are 189 new miRNA sequences. The enriched GO terms of target genes of differentially expressed miRNAs in d5 and d1 groups included cell components, organelles, cell membrane and other cell structures, molecular functions such as adhesion, catalysis and activity, and biological processes such as cell processing, metabolism, biological regulation and stress. The corresponding pathways in the top 10 of KEGG enrichment were mainly signal transduction, secretion, membrane transport, amino acid metabolism, polysaccharide metabolism, protein synthesis and environmental adaptation. The 6 randomly selected differentially expressed miRNAs verified by qRT-PCR were consistent with those of DNB sequencing. 【Conclusion】 The expression profiles of platelets miRNAs have changed significantly between the d1 and d5 of storage in vitro. Functional prediction suggested that these miRNAs might be involved in the regulation of platelet PSL.
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RNA interference (RNAi) is one of the important mechanisms to regulate gene expression in eukaryotes. One of the original functions of RNAi is to facilitate the antiviral strategy of host. Early studies reveal that invertebrates can use RNAi to resist viruses. However, if this mechanism exists in mammals is still controversial. The latest studies confirm that mammals do have the RNAi-based immunity, and researchers believe that RNAi-based antiviral immunity is a brand-new immunological mechanism that was neglected in the past. It is worthy to note that virus can also use RNAi to enhance its infectivity and immune escape in host cells. This review introduces the research history of RNAi-based antiviral immunity in animals and summarizes the main findings in this field. Last but not least, we indicate a series of unresolved questions about RNAi-based antiviral immunity, and explore the relationship between RNAi-based antiviral immunity and other innate immunological pathways. The virus-mediated RNAi pathway in animal is not only an interesting basic biology question, but also has important guiding roles in the development of antiviral drugs.
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Animals , Antiviral Agents , Immunity, Innate/genetics , Mammals , RNA Interference , RNA, Small Interfering/genetics , RNA, ViralABSTRACT
BACKGROUND: MicroRNAs (miR) is an important endogenous non-coding small RNA that regulates the expression of genes by regulating the translation of mRNA. In recent years, it has been found that miR-214 plays an important role in related bone metabolic signaling pathways, which can regulate bone resorption and bone formation by targeting related genes. OBJECTIVE: To review the new progress in the regulatory mechanism and possible application of miR-214 in bone metabolism. METHODS: The first author searched PubMed, Web of Science, and Medline with the keywords of “miRNA, miR-214, osteogenesis, osteoblast,” “miR-214, bone remodeling,” and “miR-214, osteoclast, tissue engineering” respectively for relevant literature published from 2005 to 2020. A total of 761 articles were preliminarily searched, and 63 articles that were related to the research purpose were selected and analyzed. RESULTS AND CONCLUSION: MiR-214 can promote osteoclast differentiation by targeting phosphatase-tensin homolog and tumor necrosis factor receptor associated factor 3, and inhibit osteoblast differentiation by targeting transforming growth factor β activated kinase 1 binding protein 2, cadherin protein β1, Osterix, activating transcription factor 4, α1 type IV collagen, baculovirus IAP repeat containing 7, fibroblast growth factor receptor 1, TAFA chemokine-like family member 5, and bone morphogenetic protein 2. Many studies have proved that silencing or overexpression of miR-214 can regulate bone metabolism. It is also found that miR-214 in serum or extracellular vesicles may be a marker for the diagnosis and prognosis of some diseases. It is the focus of its application research to combine miR-214 antagonists with bioscaffold materials to form a stable, efficient and safe sustained release system. Therefore, miR-214 may have great potential in the treatment of bone metabolic diseases in the future.
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OBJECTIVE@#To investigate the changes in the exosomes secreted by mouse dendritic cell line DC2.4 after infection with and to analyze the possible regulatory mechanisms underlying such changes.@*METHODS@#The exosomes were extracted by ultracentrifugation from DC2.4 cells at 28 h after infection with . The morphology of the exosomes was examined with transmission electron microscopy, and the exosome size and density were determined using a nanoparticle tracker. High-throughput sequencing was carried out to identify the differentially expressed small RNAs in the exosomes derived from the infected cells.@*RESULTS@# infection resulted in a significantly increased density of exosomes secreted by DC2.4 cells. Small RNA sequencing revealed that infection caused an increase in the number of miRNAs and piRNAs in the exosomes. The significantly up-regulated piRNAs after the infection included piR-mmu-159, piR-mmu-1526, piR-mmu-9082, piR-mmu-17405, and piR-mmu-25576.@*CONCLUSIONS@# infection causes accumulation and enrichment of exosomes secreted by DC2.4 cells with increased miRNAs and piRNAs in the exosomes.
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Animals , Mice , Cell Line , Dendritic Cells , Exosomes , MicroRNAs , RNA, Small Interfering , ToxoplasmaABSTRACT
Domestication of rice involved incorporation of specific yield-related changes in wild species of rice. This agriculturalprocess has been of significant interest for plant biologists. The recent advance in genomics has provided new tools toinvestigate the genetic basis and consequences of domestication. Several genes involved in domestication and diversification process have been characterized, and as expected, this list is over-represented by transcription factors and their cofactors. Most often the modification orchestrated expression levels of genes such as those coding for transcription factors. Ithas been proposed that transcriptional regulators and their regulation is likely a major theme controlling morphologicaldifferences between crops and their progenitors. However, recent data indicate that single amino acid changes in genescoding for key proteins as well as epigenetic and small RNA-mediated pathways also contributed towards domesticationassociated phenotypes.
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@#AIM: To investigate the protective effect of small interfering RNA targeting HIF-1α in retina of diabetic retinopathy mice and its mechanism. <p>METHODS: Totally 40 C57BL/6 male mice were randomly divided into the normal group, diabetes group, siRNA-HIF-1α group and siRNA-NC group. The diabetic models were constructed. The histopathological change of the retina of the mice was observed in each group. The microvessel density(MVD)was detected by immunohistochemistry. The expressions of HIF-1α, VEGF,NF-κB, IL-1, IL-6 and TNF-α mRNA in the retina in each group were detected by real-time quantitative PCR. The expressions of HIF-1α, ET-1 and vWF proteins in the retina in each group were detected by Western blot. <p>RESULTS: The body weights of diabetes group, siRNA-NC group and siRNA-HIF-1α group were lower than the normal group, while the blood glucose levels were higher than the normal group(All <i>P</i><0.05). The MVD in the diabetic group and siRNA-NC group were significantly higher than those in the normal group, while the siRNA-HIF-1α group were significantly lower than the diabetes group and siRNA-NC group(All <i>P</i><0.05). Compared with the diabetes group and siRNA-NC group, the relative expression levels of HIF-1α, VEGF, NF-κB, IL-1, IL-6 and TNF-α mRNA in the retina in the siRNA-HIF-1α group were decreased(All <i>P</i><0.05). Compared with the diabetes group and siRNA-NC group, the relative expression levels of HIF-1α,ET-1 and vWF proteins in the retina in the siRNA-HIF-1α group were decreased(All <i>P</i><0.05).<p>CONCLUSION: Specific silencing of HIF-1α gene could protect the retina of DR. The mechanism may be related to the reduction of angiogenesis and vascular endothelial injury.
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The efficacy of antineoplastic drugs in cancer treatment is often hampered by drug resistance of tumor cells, which is usually caused by abnormal gene expression. The formation mechanism of multidrug resistance is very complex. Conventional drugs or gene therapy usually only aim at a specific drug target, so it is difficult to effectively control the complex signaling pathways of drug-resistant cells. The co-delivery of small RNA (siRNA ormiRNA) and anti-tumor drugs with nanocarriers can maximize the synergistic effect, and reverse the multidrug resistance of tumor cells by silencing some related proteins. This review summarizes the mechanisms and advantages of the combination therapies involving RNA and antineoplastic drugs, in vitro and in vivo evaluation, as well as the recent advances in the co-delivery nanocarriers for these agents.
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High-throughput RNA-seq has revolutionized the process of small RNA (sRNA) discovery, leading to a rapid expansion of sRNA categories. In addition to the previously well-characterized sRNAs such as microRNAs (miRNAs), piwi-interacting RNAs (piRNAs), and small nucleolar RNA (snoRNAs), recent emerging studies have spotlighted on tRNA-derived sRNAs (tsRNAs) and rRNA-derived sRNAs (rsRNAs) as new categories of sRNAs that bear versatile functions. Since existing software and pipelines for sRNA annotation are mostly focused on analyzing miRNAs or piRNAs, here we developed the sRNA annotation pipelineoptimized for rRNA- and tRNA-derived sRNAs (SPORTS1.0). SPORTS1.0 is optimized for analyzing tsRNAs and rsRNAs from sRNA-seq data, in addition to its capacity to annotate canonical sRNAs such as miRNAs and piRNAs. Moreover, SPORTS1.0 can predict potential RNA modification sites based on nucleotide mismatches within sRNAs. SPORTS1.0 is precompiled to annotate sRNAs for a wide range of 68 species across bacteria, yeast, plant, and animal kingdoms, while additional species for analyses could be readily expanded upon end users' input. For demonstration, by analyzing sRNA datasets using SPORTS1.0, we reveal that distinct signatures are present in tsRNAs and rsRNAs from different mouse cell types. We also find that compared to other sRNA species, tsRNAs bear the highest mismatch rate, which is consistent with their highly modified nature. SPORTS1.0 is an open-source software and can be publically accessed at https://github.com/junchaoshi/sports1.0.
Subject(s)
Animals , Mice , Gene Expression Profiling , High-Throughput Nucleotide Sequencing , MicroRNAs , Chemistry , Metabolism , Molecular Sequence Annotation , RNA, Ribosomal , Chemistry , Metabolism , RNA, Small Interfering , Chemistry , Metabolism , RNA, Small Untranslated , Chemistry , Metabolism , RNA, Transfer , Chemistry , Metabolism , Sequence Analysis, RNA , Methods , SoftwareABSTRACT
Objective: To investigate the effects of DNAJ homolog subfamily B member 11 (DNAJB 11) gene-silencing on proliferation, cell cycle and apoptosis of human hepatocellular carcinoma cell line SMMC7721. Methods: The recombinant lentiviral vector pCDH-Puro/DNAJB11-shRNA carrying the specific shRNA targeting DNAJB 11 gene was established. The SMMC7721 cells were infected with high infective lentivirus pCDH-Puro/DNAJB11-shRNA. Then the proliferation of SMMC7721 cells was detected by CCK-8 method. The expression levels of DNAJB11, proliferating cell nuclear antigen (PCNA) and caspase-3 mRNAs and proteins in SMMC7721 cells were detected by real-time fluorescent quantitative PCR and Western blotting, respectively. The cell cycle distribution and the apoptosis rate of SMMC7721 cells were analyzed by FCM. Results: The pCDH-Puro/DNAJB11-shRNA was constructed successfully. The proliferation of SMMC7721 cells was significantly inhibited after infection with pCDH-Puro/DNAJB11- shRNA (P<0.05). In SMMC7721 cells infected with pCDH-Puro/DNAJB11-shRNA, the expressions of DNAJB11 mRNA and protein were silenced effectively (both P<0.05). After DNAJB 11 gene-silencing, the expressions of caspase-3 mRNA and protein in SMMC7721 cells were up-regulated (both P<0.05), while the expressions of PCNA mRNA and protein were down-regulated (both P<0.05). Furthermore, the cell cycle was arrested in G1 phase (P<0.01), and the apoptosis rate was significantly increased (P<0.01). Conclusion: The DNAJB 11 gene-silencing can effectively suppress the proliferation of SMMC7721 cells, and promote their apoptosis. These effects may be related to downregulation of PCNA expression and upregulation of caspase-3 expression in SMMC7721 cells.
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Abstract Soybean, a crop known by its economic and nutritional importance, has been the subject of several studies that assess the impact and the effective plant responses to abiotic stresses. Salt stress is one of the main environmental stresses and negatively impacts crop growth and yield. In this work, the RNA editing process in the chloroplast of soybean plants was evaluated in response to a salt stress. Bioinformatics approach using sRNA and mRNA libraries were employed to detect specific sites showing differences in editing efficiency. RT-qPCR was used to measure editing efficiency at selected sites. We observed that transcripts of NDHA, NDHB, RPS14 and RPS16 genes presented differences in coverage and editing rates between control and salt-treated libraries. RT-qPCR assays demonstrated an increase in editing efficiency of selected genes. The salt stress enhanced the RNA editing process in transcripts, indicating responses to components of the electron transfer chain, photosystem and translation complexes. These increases can be a response to keep the homeostasis of chloroplast protein functions in response to salt stress.
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Non-coding small RNA mainly includes microRNA, small interfering RNA and RNA interacting with PIWI protein.Studies have shown that non-coding small RNA plays an increasingly important role in the epigenetic regulation.Non-coding small RNA is involved in the regulation of gene expression by gene transcription, post-transcription and mRNA translation.Non-coding small RNA is closely related to many human diseases, especially the diagnosis, treatment and prognosis of melanoma.
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Objective To construct small RNA deletion and overexpression strains with a length of less than 100 nt in Yersinia pestis.Methods Deletion mutants of the target sRNAs were constructed by increasing the length of homologous regions.Meanwhile, the high copy plasmid pBAD/HisA was modified into an inducible transcriptional vector as an sRNA-overexpression plasmid by using QuikChange lightning site-directed mutagenesis kit .The presence , size, and transcription-al initiation sites of the indicated sRNA were predicted by transcriptome sequencing , primer extension , and previous stud-ies.The full-length DNA fragments of target sRNAs were transformed into the transcriptional vector .The overexpressing strains of sRNAs were identified by Northern Blot .Results and Conclusion Four sRNAs deletion mutants of sR01, sR02, sR03 and HmsA and three sRNAs overexpression mutants MicF , HmsA and CpxQ were successfully constructed .A method of construction of sRNA deficient and overexpressing strains of Y.pestis has been quickly and efficiently established by λ-Red homologous recombination technology and QuikChange ? lightning site-directed mutagenesis kit.
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MicroRNAs(miRNA) are small non-coding RNAs that regulate the expression of protein coding genes by repressing translation of protein coding mRNA or enhancing mRNA degradation. Its functions have attracted more and more attention from the public. In recent years, the cross-border regulation of miRNA has become a new research direction, and provides a new perspective for people to comprehensively understand the functions of miRNA. Plant miRNA is usually methylated and not easy to degrade. According to our previous researches, there were abundant small RNAs in the decoction of dried liquorice, which provides a new way to study the mechanism of action of licorice. In this study, small RNAs extracted from Glycyrrhiza uralensis decoction and synthesized miRNA mimics were used to treat peripheral blood mononuclear cells(PBMC) isolated from healthy volunteers. The gene expression of toll-like receptors(TLRs), some transcription factors, signal molecules and cytokines were analyzed by RT-PCR. The results showed that glycyrrhiza miRNA could significantly regulate PBMC by inhibiting the expression of genes involved in T cell differentiation, inflammation and apoptosis. The study brought new ideas to us in comprehensively studying the mechanism of licorice and developing the traditional Chinese medicine.
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Non-coding small RNA in bacteria is usually not translated and comprise a size range between 50 and 500 nucleotides.With the development of high-density tiling arrays and RNA deep sequencing,studies of non-coding small RNAs attracts more and more attention,and meanwhile it is evident that non-coding small RNAs play a crucial role in many biological processes such as environmental sensing and stress adaptation, virulence and infectivity of intracellular bacteria, as well as development and metabolism.This article expound non-coding small RNA from following aspects:the concept and structure, the characteristics and the classification,its regulatory mechanism and its effect on the biology of bacteria, thus providing a more comprehensive and clear understanding.
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Background and purpose:Extranodal natural killer/T-cell lymphoma (ENKTL) is a form of non-Hodgkin’s lymphoma. The ENKTL incidence in China is much higher than that in the Western countries. The disease is highly malignant, not sensitive to chemotherapy, has short survival period and poor prognosis. Epstein-Barr virus (EBV) infection has close relationship with the development of the disease. However, there are still a few patients without EBV infection. This study aimed to discuss the clinical features and prognosis of EBV-encoded small RNA (EBER) in situ hybridization negative ENKTL.Methods:From Aug. 2011 to Oct. 2015, 326 cases were diagnosed with ENKTL from the First Affliated Hospital of Zhengzhou University. The expression of EBER was detected by in situ hy-bridization technique. The clinical pathological characteristics and prognosis of EBER-negative patients were analyzed. Results:In 326 patients with ENKTL, the negative rate of EBER was 2.45% (8/326). In 8 EBER-negative patients, the median survival time was 17 months. The log-rank test revealed that there was a signiifcant difference between EBER-negative and EBER-positive curves (χ2=6.407,P=0.011). Multivariate Cox proportional hazards regression analysis showed that in EBER-negative ENKTL, only lactate dehydrogenase (LDH) predicted survival time (P=0.008). EBV-DNA copy number in plasma was not signiifcantly correlated with survival time (P>0.05).Conclusion:The inci-dence of EBER-negative ENKTL is low. Patients with EBER-negative ENKTL have poorer prognosis than EBER-posi-tive patients. Elevated LDH may be a factor indicating poor prognosis.
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Objective To study the profiles and function of small RNA (sRNA)gene during chondrogenesis in rats so as to clarify the mechanisms of chondrocytes proliferation and differentiation.Methods All the sRNAs were identified from the female SD rats femoral head cartilages at three time points:at birth,ablactation and maturation,and three sRNA libraries were constructed.The Solexa sequencing and the bioinformatics analysis were employed to be blasted with the genomes of SD rats.Results The perfect match reads in the three libraries were screened out,which were correspondent to the 21 7 921 (41.23%),1 96 650 (38.74%)and 245 436 (41.54%)unique sRNA sequence,respectively.The percentages of 20-24 nt sRNA were 71.94% (d0),72.85% (d21),and 86.39%(d42).Half of clean sequences were 22 nt sRNA.The distribution characteristics of the reads were in line with the high-quality sRNA.More than 62% clean reads were from mature miRNA while the ratios in the three libraries were only 0.69%,0.78% and 0.63%.About 60% of the unique sRNA could not be matched with miRBase20.0 or Rfam9.1.Conclusion The distribution model of miRNA in the three libraries indicates that the miRNAs with different functions or from different sources are involved in the regulation of chondrocytes proliferation and differentiation in bone development and formation.
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Chemically synthetic siRNA and miRNA have become powerful tools to study gene function in the past decade. Fluorescent dyes covalently attached to the 5′ or 3′ ends of synthetic small RNAs are widely used for fluorescently imaging and detection of these RNAs. However, the reliability of fluorescent tags as small RNA markers in different conditions has not attracted enough attention. We used Cy3-labelled small RNAs to explore the reliability of fluorescent tags as small RNA markers in cell cultures involving serum. A strong Cy3-fluorescence signal was observed in the cytoplasm of the cells transfected with Cy3-miR24 in the culture medium containing fetal bovine serum (FBS), but qRT-PCR results showed that little miR24 were detected in these cells. Further study demonstrated that small RNAs were degraded in the presence of FBS, suggesting that it was Cy3-RNA fragments, rather than the original Cy3-miR24, diffused into cells. These phenomena disappeared when FBS was replaced by boiled-FBS, further supporting that the Cy3-fluorescence we observed in cells in the presence of FBS could not represent the presence of intact small RNAs. These findings addressed that fluorescent tags are not reliable for small RNA transfection in the presence of serum in culture.