Deep sequencing of small RNA facilitates tissue and sex associated microRNA discovery in zebrafish
ABSTRACT: The role of microRNAs in gene regulation has been well established. The extent of miRNA regulation also increases with increasing genome complexity. Though the number of genes appear to be equal between human and zebrafish, substantially less microRNAs have been discovered in zebrafish compared to human (Release 19). It appears that most of the miRNAs in zebrafish are yet to be discovered. We sequenced small RNAs from brain, gut, liver, ovary, testis, eye, heart and embryo of zebrafish. In brain, gut and liver sequencing was done in male and female separately. Majority of the sequenced reads (16-62%) mapped to known miRNAs, with the exception of ovary (5.7%) and testis (7.8%). Using the miRNA discovery tool (miRDeep2), we discovered novel miRNAs from the un-annotated reads that ranged from 7.6 to 23.0%, with exceptions of ovary (51.4%) and testis (55.2%). The prediction tool identified a total of 459 novel pre-miRNAs. We compared expression of miRNAs between different tissues and between males and females to identify tissue associated and sex associated miRNAs respectively. These miRNAs could serve as putative biomarkers for these tissues. The brain and liver had highest number of tissue associated (22) and sex associated (34) miRNAs, respectively. This study comprehensively identifies tissue and sex associated miRNAs in zebrafish. Further, we have discovered 459 novel pre-miRNAs (~30% seed homology to human miRNA) as a genomic resource which can facilitate further investigations to understand miRNA-mRNA gene regulatory networks in zebrafish which will have implications in understanding the function of human homologs. Known miRNA profiling, novel miRNA discovery and identification of tissue associated and sex associated miRNAs from sRNA deep sequencing data of different tissues and embryo of zebrafish (in triplicate) was carried out using the Illumina HiSeq 2000 platform.
Project description:MicroRNAs (miRNAs) are involved in nearly every biological process examined to date. Mounting evidence show that some spermatozoa specific miRNAs play important roles in the regulation of spermatogenesis and germ cells development, but little is known of the exact identity and function of miRNA in sperm cells or their potential involvement in spermatogenesis and germ cells development. Here, we investigated the spermatozoa miRNA profiles using illumina deep sequencing combined with bioinformatic analysis using zebrafish as a model system. Deep sequencing of small RNAs yielded 12 million raw reads from zebrafish spermatozoa. Analysis showed that the noncoding RNA of the spermatozoa included tRNA, rRNA, snRNA, snoRNA and miRNA. By mapping to the zebrafish genome, we identified 400 novel and 204 conserved miRNAs which could be grouped into 104 families, including zebrafish specific families, such as mir-731, mir-724, mir-725, mir-729 and mir-2185. We report the first characterization of the miRNAs profiling in zebrafish spermatozoa. The obtained spermatozoa miRNAs profiling will serve as valuable resources to systematically study spermatogenesis in fish and vertebrate. Examination of small RNA populations in zebrafish spermatozoa
Project description:Here we identify a Dicer-independent miRNA biogenesis pathway that employs the slicer catalytic activity of Argonaute2 (Ago2). To uncover Dicer-independent miRNAs, we sequenced small RNAs in wild type, maternal-zygotic dicer (MZdicer) and MZago2 mutants, using zebrafish as a model system. We find that, in contrast to other miRNAs, miR-451 levels were increased in MZdicer but drastically reduced in the MZago2 mutants. We show that pre-miR-451 processing requires Ago2 catalytic activity in vivo. MZago2 mutant embryos display delayed erythrocyte maturation that can be rescued by wild type Ago2 or miR-451 duplex but not catalytically dead Ago2. We propose that Ago2-mediated cleavage of a subset of pre-miRNAs, followed by uridylation and trimming, generates functional miRNAs in a Dicer-independent manner. Examination of small RNAs (18 to 35 nucleotides) in 3 different zebrafish genotypes (wild type, MZago2, MZdicer) at 48 hours post-fertilization.
Project description:Background: Adult zebrafish spontaneously regenerate their retinas after damage. Although a number of genes and signaling pathways involved in regeneration have been identified, the extent of mechanisms regulating regeneration is unclear. Small non-coding RNAs, microRNAs (miRNAs), that regulate regeneration of various tissues in lower vertebrates were examined for their potential roles in regulating zebrafish retinal regeneration. Results: To investigate the requirement of miRNAs during zebrafish retinal regeneration, we knocked down the expression of the miRNA-processing enzyme Dicer in retinas prior to light-induced damage. Dicer loss significantly reduced proliferation of Müller glia-derived neuronal progenitor cells during regeneration. To identify individual miRNAs with roles in retina regeneration, we collected retinas at different stages of light damage and performed small RNA high-throughput sequencing. We identified subsets of miRNAs that were differentially expressed during active regeneration but returned to basal levels once regeneration was completed. To validate the roles of differentially expressed miRNAs, we knocked down 6 different miRNAs that were upregulated in expression during regeneration and demonstrated that they have distinct effects on neuronal progenitor cell proliferation and migration during retina regeneration. Conclusions: miRNAs are necessary for retinal regeneration. miRNA expression is dynamic during regeneration. miRNAs function during initiation and progression of retinal regeneration. Identification of miRNAs before, during and after completion of zebrafish retinal regeneration
Project description:Although environmental trace metals, such as copper (Cu), can disrupt normal olfactory function in fish, the underlying molecular mechanisms of metal-induced olfactory injury have not been elucidated. Current research has suggested the involvement of epigenetic modifications. To address this hypothesis, we analyzed microRNA (miRNA) profiles in the olfactory tissues of Cu-exposed zebrafish. Our data revealed 2, 10, and 28 differentially expressed miRNAs in a dose response pattern to three increasing Cu concentrations. Numerous deregulated miRNAs were involved in neurogenesis (let-7, miR-7a, miR-128 and miR-138), indicating a role for Cu-mediated toxicity via interference with olfactory neurogenesis. Putative gene targets of deregulated miRNAs were identified when interrogating our previously published microarray database, including those involved in olfactory cell growth and proliferation, cell death, and cell morphology. Moreover, several miRNAs (miR-203a, miR-199*, miR-16a, miR-16c, and miR-25) were inversely correlated with the depression of key genes within olfactory signal transduction pathways, which likely contributed to the inhibition of olfactory function. Our findings provide novel insight into the epigenetic regulatory mechanisms of metal-induced neurotoxicity of fish olfactory system, and identify novel miRNA biomarkers of metal exposures. 12 one-year-old adult AB strain zebrafish were exposed to Cu concentrations of 0, 6.3, 16 and 40 ppb Cu.
Project description:During early vertebrate development, a large number of noncoding RNAs are maternally inherited or expressed upon activation of zygotic transcription. The exact identity, expression levels, and function during early vertebrate development for most of these noncoding RNAs remains largely unknown. miRNAs (microRNAs) and piRNAs (piwi-interacting RNAs) are two classes of small non-coding RNAs that play important roles in gene regulation during early embryonic development. Here, we utilized Illumina next generation sequencing technology to determine temporal expression patterns for both miRNAs and piRNAs during four distinct stages of early vertebrate development using zebrafish as a model system. For miRNAs, the expression patterns for 192 known miRNAs and 12 novel miRNAs within 123 different miRNA families were determined. Significant sequence variation was observed at the 5' and 3' ends of miRNAs with a large number of extra nucleotides added in a non-template directed manner. We also identified a large and diverse set of piRNAs expressed during early development, far beyond that expected if piRNA expression is restricted to germ cells. Our analyses represent the deepest investigation to date of small RNA expression during early vertebrate development and suggest important novel functions for small RNAs during embryogenesis. Identify the expression of small RNAs in zebrafish embryos of four different developmental stages using high through-put sequencing
Project description:MicroRNAs (miRNAs) regulate different aspects of plant development by post-transcriptional regulation of target genes. In Arabidopsis, DICER-LIKE 1 (DCL1) processes miRNA precursors (pri-miRNAs) to miRNA duplexes, which associate with ARGONAUTE 1 (AGO1). AGO1 together with the miRNA guide strand binds complementary RNA sequences within target mRNAs. Additional proteins act in concert with DCL1 (e.g. HYL1 and SERRATE) and AGO1, respectively, to facilitate efficient and precise pri-miRNA processing and loading into the effector protein. Here, we show that RECEPTOR OF ACTIVATED C KINASE 1 (RACK1) is a novel component of the Arabidopsis miRNA pathway. RACK1 is a seven-bladed WD-repeat protein that has previously been shown to act as a scaffold protein mediating multiple simultaneous protein-protein interactions. Our molecular analyses demonstrate that RACK1 function is required for controlling miRNA-mediated gene expression. rack1 mutants contain only low levels of mature miRNAs without affecting the first step of pri-miRNA processing. Physical and genetic interaction studies revealed that RACK1 acts in concert with AGO1 and also interacts with a SERRATE, a component of the miRNA processing machinery. These results suggest that RACK1 also functions as a scaffold protein in the miRNA pathway to orchestrates miRNA maturation steps after the initial events of pri-miRNA processing. sequencing of small RNAs from WT and rack1abc mutants (two biological replicates each)
Project description:Prenatal exposure to ethanol leads to a myriad of developmental disorders known as fetal alcohol spectrum disorder, often characterized by growth and mental retardation, central nervous system damage and specific craniofacial dysmorphic features. Although the exact mechanisms of ethanol toxicity are not well understood it is known that ethanol exposure during development affects the expression of several genes involved in cell cycle control, apoptosis and transcription. MicroRNAs (miRNAs) are implicated in some of these processes however it is unclear if they are involved in ethanol-induced toxicity. Here we tested whether ethanol deregulates miRNA expression in zebrafish embryos and if a miRNA deregulation signature could be inferred. For this, zebrafish embryos were exposed to two different ethanol concentrations (1% and 1.5%) from 4 hours post-fertilization (hpf) to 24hpf. MicroRNA expression profiles revealed that ethanol exposure induces deregulation of miRNA expression significantly. Seven miRNAs are commonly up-regulated after both ethanol treatments, namely miR-153a, miR-725, miR-30d, let-7k, miR-100, miR-738 and miR-732, whereas downregulation of miR-23a, miR-203, let-7c, miR-128 and miR-193b is detected after 1% ethanol exposure only. Target prediction of deregulated miRNAs shows that putative targets are involved in cell cycle control, apoptosis and transcription, which are the main processes affected by ethanol toxicity. The overall study shows that the effects of ethanol on miRNA deregulation are dose-dependent and that miRNAs are relevant in the context of alcohol toxicity. Moreover, a miRNA toxicity signature for embryonic ethanol exposure was obtained. Zebrafish embryos were obtained from spawning adults in groups of about 10 males and 10 females. Zebrafish embryos were collected and Petri dishes with approximately 250 eggs each were incubated at 28ºC to allow normal zebrafish development until 4hpf, when blastula is reached. At this stage, embryos were examined under a dissecting microscope and those that had developed normally were selected for EtOH exposure (approximately 200 eggs). Briefly, 200 embryos were randomly distributed into plastic Petri dishes containing 20 mL of EtOH test solutions (1% EtOH, 1.5% EtOH). All solutions were made by dilution of absolute EtOH in system water. Exposure was from 4hpf to 24hpf. At this stage, solutions were changed by system water and embryos were allowed to grow until 24hpf. The control group was allowed to grow in plain system water. Zebrafish embryos were collected at 24hpf for microarray analysis. Two biological replicates were performed for each assay.
Project description:MicroRNAs are a class of small non-coding RNAs that regulate mRNA expression at the post-transcriptional level and thereby many fundamental biological processes. A number of methods, such as multiplex polymerase chain reaction, microarrays have been developed for profiling levels of known miRNAs. These methods lack ability to identify novel miRNAs and accurately determine expression at a range of concentration. Deep or massively parallel sequencing methods are providing suitable platforms for genome wide transcriptome analysis and have the ability to identify novel transcripts. The results of analysis of small RNA sequences obtained by Solexa technology of normal peripheral blood mononuclear cells, tumor cell lines K562 (chronic myelogenous leukemia) and HL60 (acute promyelogenous leukemia) are presented. Custom computation pipelines were used to generate expression profiles of known and for identification of novel miRNAs. Some of the highly expressed miRNAs in the leukocytes include several members of the let 7 family, mir-21, 103, 185, 191 and 320a. Comparison of the miRNA profiles of normal versus K562 cells or HL60 revealed a specific set of differentially expressed molecules. Correlation of the miRNA with that of mRNA expression profiles, obtained by microarray, revealed a set of target genes showing inverse correlation with miRNA levels. Our computational pipeline also predicted a number of novel miRNAs. Some of the predictions were validated by realtime RT-PCR and or RNAase protection assay. The small RNA population from four samples - Two Normal Peripheral blood mononuclear cells (PBMC) samples, K562 cell line (This cell line is used as a model to study Chronic Myelogenous Leukemia), HL60 (This cell line is used to study acute promyelogenous leukemia) was sequenced using Solexa technology.
Project description:Porcine cytomegalovirus (PCMV; genus Cytomegalovirus, subfamily Betaherpesvirinae, family Herpesviridae) is an immunosuppressive virus that mainly inhibits the immune function of T lymphocytes and macrophages, which has caused great distress to the farming industry. In this study, we obtained the miRNA expression profiles of PCMV-infected and control porcine macrophages, PCMV-infected and control porcine tissues via high-throughput sequencing. The comprehensive analysis of miRNA profiles showed that 306 miRNA database annotated and 295 novel pig-encoded miRNAs were detected. Gene Ontology (GO) analysis of the target genes of miRNAs in PCMV infected porcine macrophages showed that the differentially expressed miRNAs are mainly involved in immune and metabolic process. This is the first report of the miRNA transcriptome in PCMV infected porcine macrophages and PCMV infected tissues and the analysis of the miRNA regulatory mechanism during PCMV infection. Further research into the regulatory mechanisms of miRNAs during immunosuppressive viral infections will contribute to the treatment and prevention of immunosuppressive viruses. miRNA expression profiling of PCMV-infected and control porcine macrophages; PCMV-infected and control porcine tissues via high-throughput sequencing.
Project description:BACKGROUND: MicroRNAs (miRNAs) are a new class of small RNAs of approximately 22 nucleotides in length that control eukaryotic gene expression by fine tuning mRNA translation. They regulate a wide variety of biological processes, namely developmental timing, cell differentiation, cell proliferation, immune response and infection. For this reason, their identification is essential to understand eukaryotic biology. Their small size, low abundance and high instability complicated early identification, however cloning/Sanger sequencing and new generation genome sequencing approaches overcame most technical hurdles and are being used for rapid miRNA identification in many eukaryotes. RESULTS: We have applied 454 DNA pyrosequencing technology to miRNA discovery in zebrafish (Danio rerio). For this, a series of cDNA libraries were prepared from miRNAs isolated at different embryonic time points and from fully developed organs. Each cDNA library was tagged with specific sequences and was sequenced using the Roche FLX genome sequencer. This approach retrieved 90% of the 192 miRNAs previously identified by cloning/Sanger sequencing and bioinformatics. Twenty five novel miRNAs were predicted, 107 miRNA star sequences and also 41 candidate miRNA targets were identified. A miRNA expression profile built on the basis of pyrosequencing read numbers showed high expression of most miRNAs throughout zebrafish development and identified tissue specific miRNAs. CONCLUSION: This study increases the number of zebrafish miRNAs from 192 to 217 and demonstrates that a single DNA mini-chip pyrosequencing run is effective in miRNA identification in zebrafish. This methodology also produced sufficient information to elucidate miRNA expression patterns during development and in differentiated organs. Moreover, some zebrafish miRNA star sequences were more abundant than their corresponding miRNAs, suggesting a functional role for the former in gene expression control in this vertebrate model organism.