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Shen Z, Naveed M, Bao J. Untacking small RNA profiling and RNA fragment footprinting: Approaches and challenges in library construction. WILEY INTERDISCIPLINARY REVIEWS. RNA 2024; 15:e1852. [PMID: 38715192 DOI: 10.1002/wrna.1852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/09/2024] [Accepted: 04/10/2024] [Indexed: 06/06/2024]
Abstract
Small RNAs (sRNAs) with sizes ranging from 15 to 50 nucleotides (nt) are critical regulators of gene expression control. Prior studies have shown that sRNAs are involved in a broad range of biological processes, such as organ development, tumorigenesis, and epigenomic regulation; however, emerging evidence unveils a hidden layer of diversity and complexity of endogenously encoded sRNAs profile in eukaryotic organisms, including novel types of sRNAs and the previously unknown post-transcriptional RNA modifications. This underscores the importance for accurate, unbiased detection of sRNAs in various cellular contexts. A multitude of high-throughput methods based on next-generation sequencing (NGS) are developed to decipher the sRNA expression and their modifications. Nonetheless, distinct from mRNA sequencing, the data from sRNA sequencing suffer frequent inconsistencies and high variations emanating from the adapter contaminations and RNA modifications, which overall skew the sRNA libraries. Here, we summarize the sRNA-sequencing approaches, and discuss the considerations and challenges for the strategies and methods of sRNA library construction. The pros and cons of sRNA sequencing have significant implications for implementing RNA fragment footprinting approaches, including CLIP-seq and Ribo-seq. We envision that this review can inspire novel improvements in small RNA sequencing and RNA fragment footprinting in future. This article is categorized under: RNA Evolution and Genomics > Computational Analyses of RNA RNA Processing > Processing of Small RNAs Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs.
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Affiliation(s)
- Zhaokang Shen
- Department of Obstetrics and Gynecology, Center for Reproduction and Genetics, The First Affiliated Hospital of USTC, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
- Hefei National Laboratory for Physical Sciences at Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China (USTC), Hefei, Anhui, China
| | - Muhammad Naveed
- Hefei National Laboratory for Physical Sciences at Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China (USTC), Hefei, Anhui, China
- Department of Obstetrics and Gynecology, Center for Reproduction and Genetics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Jianqiang Bao
- Department of Obstetrics and Gynecology, Center for Reproduction and Genetics, The First Affiliated Hospital of USTC, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
- Hefei National Laboratory for Physical Sciences at Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China (USTC), Hefei, Anhui, China
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2
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Kim IV, Demtröder T, Kuhn CD. Isolation and Library Preparation of Planarian piRNAs. Methods Mol Biol 2023; 2680:29-54. [PMID: 37428369 DOI: 10.1007/978-1-0716-3275-8_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
In planarian flatworms, piRNAs and SMEDWI (Schmidtea mediterranea PIWI) proteins are both essential for the animals' impressive regenerative ability and for their survival. A knockdown of SMEDWI proteins disrupts the specification of the planarian germline and impairs stem cell differentiation, resulting in lethal phenotypes. As the molecular targets of PIWI proteins and thus their biological function are determined by PIWI-bound small RNAs, termed piRNAs (for PIWI-interacting RNAs), it is imperative to study the wealth of PIWI-bound piRNAs using next-generation sequencing-based techniques. Prior to sequencing, piRNAs bound to individual SMEDWI proteins must be isolated. To that end, we established an immunoprecipitation protocol that can be applied to all planarian SMEDWI proteins. Co-immunoprecipitated piRNAs are visualized by using qualitative radioactive 5'-end labeling, which detects even trace amounts of small RNAs. Next, isolated piRNAs are subjected to a library preparation protocol that has been optimized for the efficient capture of piRNAs, whose 3'-ends carry a 2'-O-methyl modification. Successfully prepared piRNA libraries are subjected to Illumina-based next-generation sequencing. Obtained data are analyzed as presented in the accompanying manuscript.
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Affiliation(s)
- Iana V Kim
- RNA Biochemistry, University of Bayreuth, Bayreuth, Germany
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Tim Demtröder
- RNA Biochemistry, University of Bayreuth, Bayreuth, Germany
| | - Claus-D Kuhn
- RNA Biochemistry, University of Bayreuth, Bayreuth, Germany.
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3
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Kuo MC, Liu SCH, Hsu YF, Wu RM. The role of noncoding RNAs in Parkinson's disease: biomarkers and associations with pathogenic pathways. J Biomed Sci 2021; 28:78. [PMID: 34794432 PMCID: PMC8603508 DOI: 10.1186/s12929-021-00775-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 11/04/2021] [Indexed: 02/08/2023] Open
Abstract
The discovery of various noncoding RNAs (ncRNAs) and their biological implications is a growing area in cell biology. Increasing evidence has revealed canonical and noncanonical functions of long and small ncRNAs, including microRNAs, long ncRNAs (lncRNAs), circular RNAs, PIWI-interacting RNAs, and tRNA-derived fragments. These ncRNAs have the ability to regulate gene expression and modify metabolic pathways. Thus, they may have important roles as diagnostic biomarkers or therapeutic targets in various diseases, including neurodegenerative disorders, especially Parkinson's disease. Recently, through diverse sequencing technologies and a wide variety of bioinformatic analytical tools, such as reverse transcriptase quantitative PCR, microarrays, next-generation sequencing and long-read sequencing, numerous ncRNAs have been shown to be associated with neurodegenerative disorders, including Parkinson's disease. In this review article, we will first introduce the biogenesis of different ncRNAs, including microRNAs, PIWI-interacting RNAs, circular RNAs, long noncoding RNAs, and tRNA-derived fragments. The pros and cons of the detection platforms of ncRNAs and the reproducibility of bioinformatic analytical tools will be discussed in the second part. Finally, the recent discovery of numerous PD-associated ncRNAs and their association with the diagnosis and pathophysiology of PD are reviewed, and microRNAs and long ncRNAs that are transported by exosomes in biofluids are particularly emphasized.
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Affiliation(s)
- Ming-Che Kuo
- Department of Medicine, Section of Neurology, Cancer Center, National Taiwan University Hospital, Taipei, Taiwan
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Sam Chi-Hao Liu
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ya-Fang Hsu
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ruey-Meei Wu
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan.
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4
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Olzog VJ, Gärtner C, Stadler PF, Fallmann J, Weinberg CE. cyPhyRNA-seq: a genome-scale RNA-seq method to detect active self-cleaving ribozymes by capturing RNAs with 2',3' cyclic phosphates and 5' hydroxyl ends. RNA Biol 2021; 18:818-831. [PMID: 34906034 PMCID: PMC8782182 DOI: 10.1080/15476286.2021.1999105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Self-cleaving ribozymes are catalytically active RNAs that cleave themselves into a 5′-fragment with a 2′,3′-cyclic phosphate and a 3′-fragment with a 5′-hydroxyl. They are widely applied for the construction of synthetic RNA devices and RNA-based therapeutics. However, the targeted discovery of self-cleaving ribozymes remains a major challenge. We developed a transcriptome-wide method, called cyPhyRNA-seq, to screen for ribozyme cleavage fragments in total RNA extract. This approach employs the specific ligation-based capture of ribozyme 5′-fragments using a variant of the Arabidopsis thaliana tRNA ligase we engineered. To capture ribozyme 3′-fragments, they are enriched from total RNA by enzymatic treatments. We optimized and enhanced the individual steps of cyPhyRNA-seq in vitro and in spike-in experiments. Then, we applied cyPhyRNA-seq to total RNA isolated from the bacterium Desulfovibrio vulgaris and detected self-cleavage of the three predicted type II hammerhead ribozymes, whose activity had not been examined to date. cyPhyRNA-seq can be used for the global analysis of active self-cleaving ribozymes with the advantage to capture both ribozyme cleavage fragments from total RNA. Especially in organisms harbouring many self-cleaving RNAs, cyPhyRNA-seq facilitates the investigation of cleavage activity. Moreover, this method has the potential to be used to discover novel self-cleaving ribozymes in different organisms.
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Affiliation(s)
- V Janett Olzog
- Department of Life Science, Institute for Biochemistry, Leipzig, Germany
| | - Christiane Gärtner
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, Leipzig University, Leipzig, Germany
| | - Peter F Stadler
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, Leipzig University, Leipzig, Germany.,Max Planck Institute for Mathematics in the Sciences, Leipzig, Germany.,Department of Theoretical Chemistry, Vienna, Austria.,Facultad de Ciencias, Universidad National de Colombia, Sede Bogotá, Colombia.,Santa Fe Institute, University of Vienna, Santa Fe, New Mexico, USA
| | - Jörg Fallmann
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, Leipzig University, Leipzig, Germany
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5
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Shtratnikova V, Naumov V, Bezuglov V, Zheludkevich A, Smigulina L, Dikov Y, Denisova T, Suvorov A, Pilsner JR, Hauser R, Krawetz SA, Sergeyev O. Optimization of small RNA extraction and comparative study of NGS library preparation from low count sperm samples. Syst Biol Reprod Med 2021; 67:230-243. [PMID: 34082629 DOI: 10.1080/19396368.2021.1912851] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Recent studies demonstrate that sperm epigenome is a vehicle that conveys paternal experiences to offspring phenotype. That evidence triggers interest of both experimental and epidemiological studies of epigenetic markers in sperm. Since samples are often unique in epidemiological studies, a careful and efficient use of the material is a critical requirement. The goal of this study was to provide optimization of methods for the isolation of small RNAs from spermatozoa and library preparation for sequencing. A total 67 fractionated sperm samples from the Russian Children's Study biobank prospectively collected at 18-20 years of age were used to isolate small RNAs with median (IQR) input total sperm count 17.0 (7.4-35.9) million. Twenty-four pairs of libraries were prepared using the NEBNext and NEXTFlex kits, 19 libraries using NEBNext and 6 using NEXTFlex. All libraries were sequenced on NextSeq 500, and the results were evaluated as a function of the number of small non-coding RNA (sncRNA) detected, quality parameters of sequencing libraries, as well as technical features of sample preparation. Although the same amount of miRNA input was used for NEBNext and NEXTFlex libraries, the concentration of DNA in NEBNext libraries was significantly higher in comparison with NEXTFlex libraries. In high input (sperm count >28 million and more than 25 ng miRNA in library) NEXTFlex Small RNA-Seq kit detected more microRNAs. In low input, the NEBNext proved more effective. The tricks and traps to protocol optimization are presented, including an efficient and effector gel-based system for the removal of sequencing library adaptors.
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Affiliation(s)
- Victoria Shtratnikova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Vladimir Naumov
- Kulakov National Medical Research Center of Obstetrics, Gynecology & Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
| | - Vitaly Bezuglov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | | | - Luidmila Smigulina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Chapaevsk Medical Association, Chapaevsk, Russia
| | - Yury Dikov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Chapaevsk Medical Association, Chapaevsk, Russia
| | - Tatiana Denisova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Chapaevsk Medical Association, Chapaevsk, Russia
| | - Alexander Suvorov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Department of Environmental Health Sciences, University of Massachusetts, Amherst, Massachusetts, USA
| | - J Richard Pilsner
- Department of Environmental Health Sciences, University of Massachusetts, Amherst, Massachusetts, USA
| | - Russ Hauser
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Stephen A Krawetz
- Department of Obstetrics and Gynecology, Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Oleg Sergeyev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Chapaevsk Medical Association, Chapaevsk, Russia
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6
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Benesova S, Kubista M, Valihrach L. Small RNA-Sequencing: Approaches and Considerations for miRNA Analysis. Diagnostics (Basel) 2021; 11:964. [PMID: 34071824 PMCID: PMC8229417 DOI: 10.3390/diagnostics11060964] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/21/2021] [Accepted: 05/24/2021] [Indexed: 01/15/2023] Open
Abstract
MicroRNAs (miRNAs) are a class of small RNA molecules that have an important regulatory role in multiple physiological and pathological processes. Their disease-specific profiles and presence in biofluids are properties that enable miRNAs to be employed as non-invasive biomarkers. In the past decades, several methods have been developed for miRNA analysis, including small RNA sequencing (RNA-seq). Small RNA-seq enables genome-wide profiling and analysis of known, as well as novel, miRNA variants. Moreover, its high sensitivity allows for profiling of low input samples such as liquid biopsies, which have now found applications in diagnostics and prognostics. Still, due to technical bias and the limited ability to capture the true miRNA representation, its potential remains unfulfilled. The introduction of many new small RNA-seq approaches that tried to minimize this bias, has led to the existence of the many small RNA-seq protocols seen today. Here, we review all current approaches to cDNA library construction used during the small RNA-seq workflow, with particular focus on their implementation in commercially available protocols. We provide an overview of each protocol and discuss their applicability. We also review recent benchmarking studies comparing each protocol's performance and summarize the major conclusions that can be gathered from their usage. The result documents variable performance of the protocols and highlights their different applications in miRNA research. Taken together, our review provides a comprehensive overview of all the current small RNA-seq approaches, summarizes their strengths and weaknesses, and provides guidelines for their applications in miRNA research.
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Affiliation(s)
- Sarka Benesova
- Laboratory of Gene Expression, Institute of Biotechnology, CAS, BIOCEV, 252 50 Vestec, Czech Republic; (S.B.); (M.K.)
- Laboratory of Informatics and Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology, 166 28 Prague, Czech Republic
| | - Mikael Kubista
- Laboratory of Gene Expression, Institute of Biotechnology, CAS, BIOCEV, 252 50 Vestec, Czech Republic; (S.B.); (M.K.)
- TATAA Biocenter AB, 411 03 Gothenburg, Sweden
| | - Lukas Valihrach
- Laboratory of Gene Expression, Institute of Biotechnology, CAS, BIOCEV, 252 50 Vestec, Czech Republic; (S.B.); (M.K.)
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7
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Small RNAs Are Implicated in Regulation of Gene and Transposable Element Expression in the Protist Trichomonas vaginalis. mSphere 2021; 6:6/1/e01061-20. [PMID: 33408230 PMCID: PMC7845603 DOI: 10.1128/msphere.01061-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Trichomoniasis, caused by the protozoan Trichomonas vaginalis, is the most common nonviral sexually transmitted infection in humans. The millions of cases each year have sequelae that may include complications during pregnancy and increased risk of HIV infection. Trichomonas vaginalis is the causative agent of trichomoniasis, the most prevalent nonviral sexually transmitted infection worldwide. Repetitive elements, including transposable elements (TEs) and virally derived repeats, comprise more than half of the ∼160-Mb T. vaginalis genome. An intriguing question is how the parasite controls its potentially lethal complement of mobile elements, which can disrupt transcription of protein-coding genes and genome functions. In this study, we generated high-throughput RNA sequencing (RNA-Seq) and small RNA-Seq data sets in triplicate for the T. vaginalis G3 reference strain and characterized the mRNA and small RNA populations and their mapping patterns along all six chromosomes. Mapping the RNA-Seq transcripts to the genome revealed that the majority of genes predicted within repetitive elements are not expressed. Interestingly, we identified a novel species of small RNA that maps bidirectionally along the chromosomes and is correlated with reduced protein-coding gene expression and reduced RNA-Seq coverage in repetitive elements. This novel small RNA family may play a regulatory role in gene and repetitive element expression. Our results identify a possible small RNA pathway mechanism by which the parasite regulates expression of genes and TEs and raise intriguing questions as to the role repeats may play in shaping T. vaginalis genome evolution and the diversity of small RNA pathways in general. IMPORTANCE Trichomoniasis, caused by the protozoan Trichomonas vaginalis, is the most common nonviral sexually transmitted infection in humans. The millions of cases each year have sequelae that may include complications during pregnancy and increased risk of HIV infection. Given its evident success in this niche, it is paradoxical that T. vaginalis harbors in its genome thousands of transposable elements that have the potential to be extremely detrimental to normal genomic function. In many organisms, transposon expression is regulated by the activity of endogenously expressed short (∼21 to 35 nucleotides [nt]) small RNA molecules that effect gene silencing by targeting mRNAs for degradation or by recruiting epigenetic silencing machinery to locations in the genome. Our research has identified small RNA molecules correlated with reduced expression of T. vaginalis genes and transposons. This suggests that a small RNA pathway is a major contributor to gene expression patterns in the parasite and opens up new avenues for investigation into small RNA biogenesis, function, and diversity.
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8
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van Dijk EL, Thermes C. A Small RNA-Seq Protocol with Less Bias and Improved Capture of 2'-O-Methyl RNAs. Methods Mol Biol 2021; 2298:153-167. [PMID: 34085244 DOI: 10.1007/978-1-0716-1374-0_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The study of small RNAs (sRNAs) by next-generation sequencing (NGS) is challenged by bias issues during library preparation. Several types of sRNAs such as plant microRNAs (miRNAs) carry a 2'-O-methyl (2'-OMe) modification at their 3' terminal nucleotide. This modification adds another level of difficulty as it inhibits 3' adapter ligation. We previously demonstrated that modified versions of the "TruSeq (TS)" protocol have less bias and an improved detection of 2'-OMe RNAs. Here we describe in detail protocol "TS5," which showed the best overall performance. We also provide guidelines for bioinformatics analysis of the sequencing data.
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Affiliation(s)
- Erwin L van Dijk
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, Gif sur Yvette Cedex, France.
| | - Claude Thermes
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, Gif sur Yvette Cedex, France
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9
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Emerging isothermal amplification technologies for microRNA biosensing: Applications to liquid biopsies. Mol Aspects Med 2020; 72:100832. [DOI: 10.1016/j.mam.2019.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/06/2019] [Accepted: 11/10/2019] [Indexed: 02/07/2023]
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10
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Zhao J, Feng H, Zhu D, Zhang C, Xu Y. DTA-SiST: de novo transcriptome assembly by using simplified suffix trees. BMC Bioinformatics 2019; 20:698. [PMID: 31874618 PMCID: PMC6929406 DOI: 10.1186/s12859-019-3272-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Alternative splicing allows the pre-mRNAs of a gene to be spliced into various mRNAs, which greatly increases the diversity of proteins. High-throughput sequencing of mRNAs has revolutionized our ability for transcripts reconstruction. However, the massive size of short reads makes de novo transcripts assembly an algorithmic challenge. Results We develop a novel radical framework, called DTA-SiST, for de novo transcriptome assembly based on suffix trees. DTA-SiST first extends contigs by reads that have the longest overlaps with the contigs’ terminuses. These reads can be found in linear time of the lengths of the reads through a well-designed suffix tree structure. Then, DTA-SiST constructs splicing graphs based on contigs for each gene locus. Finally, DTA-SiST proposes two strategies to extract transcript-representing paths: a depth-first enumeration strategy and a hybrid strategy based on length and coverage. We implemented the above two strategies and compared them with the state-of-the-art de novo assemblers on both simulated and real datasets. Experimental results showed that the depth-first enumeration strategy performs always better with recall and also better with precision for smaller datasets while the hybrid strategy leads with precision for big datasets. Conclusions DTA-SiST performs more competitive than the other compared de novo assemblers especially with precision measure, due to the read-based contig extension strategy and the elegant transcripts extraction rules.
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Affiliation(s)
- Jin Zhao
- School of Computer Science and Technology, Shandong University, Binhai Road, Qingdao, Shandong, People's Republic of China
| | - Haodi Feng
- School of Computer Science and Technology, Shandong University, Binhai Road, Qingdao, Shandong, People's Republic of China.
| | - Daming Zhu
- School of Computer Science and Technology, Shandong University, Binhai Road, Qingdao, Shandong, People's Republic of China
| | - Chi Zhang
- Department of Medical and Molecular Genetics and Center for Computational Biology and Bioinformatics, Indiana University, Indianapolis, IN, USA
| | - Ying Xu
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
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11
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Mori MA, Ludwig RG, Garcia-Martin R, Brandão BB, Kahn CR. Extracellular miRNAs: From Biomarkers to Mediators of Physiology and Disease. Cell Metab 2019; 30:656-673. [PMID: 31447320 PMCID: PMC6774861 DOI: 10.1016/j.cmet.2019.07.011] [Citation(s) in RCA: 471] [Impact Index Per Article: 94.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 05/25/2019] [Accepted: 07/24/2019] [Indexed: 02/07/2023]
Abstract
miRNAs can be found in serum and other body fluids and serve as biomarkers for disease. More importantly, secreted miRNAs, especially those in extracellular vesicles (EVs) such as exosomes, may mediate paracrine and endocrine communication between different tissues and thus modulate gene expression and the function of distal cells. When impaired, these processes can lead to tissue dysfunction, aging, and disease. Adipose tissue is an especially important contributor to the pool of circulating exosomal miRNAs. As a result, alterations in adipose tissue mass or function, which occur in many metabolic conditions, can lead to changes in circulating miRNAs, which then function systemically. Here we review the findings that led to these conclusions and discuss how this sets the stage for new lines of investigation in which extracellular miRNAs are recognized as important mediators of intercellular communication and potential candidates for therapy of disease.
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Affiliation(s)
- Marcelo A Mori
- Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, SP, Brazil.
| | - Raissa G Ludwig
- Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, SP, Brazil
| | - Ruben Garcia-Martin
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Bruna B Brandão
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - C Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA.
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12
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Barberán-Soler S, Vo JM, Hogans RE, Dallas A, Johnston BH, Kazakov SA. Decreasing miRNA sequencing bias using a single adapter and circularization approach. Genome Biol 2018; 19:105. [PMID: 30173660 PMCID: PMC6120088 DOI: 10.1186/s13059-018-1488-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 07/18/2018] [Indexed: 12/22/2022] Open
Abstract
The ability to accurately quantify all the microRNAs (miRNAs) in a sample is important for understanding miRNA biology and for development of new biomarkers and therapeutic targets. We develop a new method for preparing miRNA sequencing libraries, RealSeq®-AC, that involves ligating the miRNAs with a single adapter and circularizing the ligation products. When compared to other methods, RealSeq®-AC provides greatly reduced miRNA sequencing bias and allows the identification of the largest variety of miRNAs in biological samples. This reduced bias also allows robust quantification of miRNAs present in samples across a wide range of RNA input levels.
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Affiliation(s)
| | - Jenny M. Vo
- SomaGenics, Inc., Santa Cruz, California, USA
| | | | - Anne Dallas
- SomaGenics, Inc., Santa Cruz, California, USA
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13
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Chang KW, Tseng YT, Chen YC, Yu CY, Liao HF, Chen YC, Tu YFE, Wu SC, Liu IH, Pinskaya M, Morillon A, Pain B, Lin SP. Stage-dependent piRNAs in chicken implicated roles in modulating male germ cell development. BMC Genomics 2018; 19:425. [PMID: 29859049 PMCID: PMC5984780 DOI: 10.1186/s12864-018-4820-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023] Open
Abstract
Background The PIWI/piRNA pathway is a conserved machinery important for germ cell development and fertility. This piRNA-guided molecular machinery is best known for repressing derepressed transposable elements (TE) during epigenomic reprogramming. The extent to which piRNAs are involved in modulating transcripts beyond TEs still need to be clarified, and it may be a stage-dependent event. We chose chicken germline as a study model because of the significantly lower TE complexity in the chicken genome compared to mammalian species. Results We generated high-confidence piRNA candidates in various stages across chicken germline development by 3′-end-methylation-enriched small RNA sequencing and in-house bioinformatics analysis. We observed a significant developmental stage-dependent loss of TE association and a shifting of the ping-pong cycle signatures. Moreover, the stage-dependent reciprocal abundance of LINE retrotransposons, CR1-C, and its associated piRNAs implicated the developmental stage-dependent role of piRNA machinery. The stage dependency of piRNA expression and its potential functions can be better addressed by analyzing the piRNA precursors/clusters. Interestingly, the new piRNA clusters identified from embryonic chicken testes revealed evolutionary conservation between chickens and mammals, which was previously thought to not exist. Conclusions In this report, we provided an original chicken RNA resource and proposed an analytical methodology that can be used to investigate stage-dependent changes in piRNA compositions and their potential roles in TE regulation and beyond, and also revealed possible conserved functions of piRNAs in developing germ cells. Electronic supplementary material The online version of this article (10.1186/s12864-018-4820-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kai-Wei Chang
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, 106, Taiwan.,Present Address: Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan
| | - Yen-Tzu Tseng
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan.,Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan
| | - Yi-Chen Chen
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan.,Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan.,Univ Lyon, Université Lyon 1, INSERM, INRA, Stem Cell and Brain Research Institute, U1208, USC1361, F-69500, Bron, France
| | - Chih-Yun Yu
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan
| | - Hung-Fu Liao
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan
| | - Yi-Chun Chen
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan
| | - Yu-Fan Evan Tu
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan
| | - Shinn-Chih Wu
- Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan
| | - I-Hsuan Liu
- Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan
| | - Marina Pinskaya
- ncRNA, epigenetic and genome fluidity, Institut Curie, Centre de Recherche, CNRS UMR 3244, PSL Research University, Université Pierre et Marie Curie, F-75005, Paris, France
| | - Antonin Morillon
- ncRNA, epigenetic and genome fluidity, Institut Curie, Centre de Recherche, CNRS UMR 3244, PSL Research University, Université Pierre et Marie Curie, F-75005, Paris, France
| | - Bertrand Pain
- Univ Lyon, Université Lyon 1, INSERM, INRA, Stem Cell and Brain Research Institute, U1208, USC1361, F-69500, Bron, France
| | - Shau-Ping Lin
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, 106, Taiwan. .,Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan. .,Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, 106, Taiwan. .,Agricultural Biotechnology Research Centre, Academia Sinica, Taipei, 106, Taiwan. .,Center for Systems Biology, National Taiwan University, Taipei, 106, Taiwan.
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14
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Boone M, De Koker A, Callewaert N. Capturing the 'ome': the expanding molecular toolbox for RNA and DNA library construction. Nucleic Acids Res 2018; 46:2701-2721. [PMID: 29514322 PMCID: PMC5888575 DOI: 10.1093/nar/gky167] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 02/05/2018] [Accepted: 02/23/2018] [Indexed: 12/14/2022] Open
Abstract
All sequencing experiments and most functional genomics screens rely on the generation of libraries to comprehensively capture pools of targeted sequences. In the past decade especially, driven by the progress in the field of massively parallel sequencing, numerous studies have comprehensively assessed the impact of particular manipulations on library complexity and quality, and characterized the activities and specificities of several key enzymes used in library construction. Fortunately, careful protocol design and reagent choice can substantially mitigate many of these biases, and enable reliable representation of sequences in libraries. This review aims to guide the reader through the vast expanse of literature on the subject to promote informed library generation, independent of the application.
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Affiliation(s)
- Morgane Boone
- Center for Medical Biotechnology, VIB, Zwijnaarde 9052, Belgium
- Department of Biochemistry and Microbiology, Ghent University, Ghent 9000, Belgium
| | - Andries De Koker
- Center for Medical Biotechnology, VIB, Zwijnaarde 9052, Belgium
- Department of Biochemistry and Microbiology, Ghent University, Ghent 9000, Belgium
| | - Nico Callewaert
- Center for Medical Biotechnology, VIB, Zwijnaarde 9052, Belgium
- Department of Biochemistry and Microbiology, Ghent University, Ghent 9000, Belgium
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15
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Dard-Dascot C, Naquin D, d'Aubenton-Carafa Y, Alix K, Thermes C, van Dijk E. Systematic comparison of small RNA library preparation protocols for next-generation sequencing. BMC Genomics 2018; 19:118. [PMID: 29402217 PMCID: PMC5799908 DOI: 10.1186/s12864-018-4491-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 01/22/2018] [Indexed: 01/19/2023] Open
Abstract
Background Next-generation sequencing technologies have revolutionized the study of small RNAs (sRNAs) on a genome-wide scale. However, classical sRNA library preparation methods introduce serious bias, mainly during adapter ligation steps. Several types of sRNA including plant microRNAs (miRNA), piwi-interacting RNAs (piRNA) in insects, nematodes and mammals, and small interfering RNAs (siRNA) in insects and plants contain a 2’-O-methyl (2’-OMe) modification at their 3′ terminal nucleotide. This inhibits 3′ adapter ligation and makes library preparation particularly challenging. To reduce bias, the NEBNext kit (New England Biolabs) uses polyethylene glycol (PEG), the NEXTflex V2 kit (BIOO Scientific) uses both randomised adapters and PEG, and the novel SMARTer (Clontech) and CATS (Diagenode) kits avoid ligation altogether. Here we compared these methods with Illumina’s classical TruSeq protocol regarding the detection of normal and 2’ OMe RNAs. In addition, we modified the TruSeq and NEXTflex protocols to identify conditions that improve performance. Results Among the five kits tested with their respective standard protocols, the SMARTer and CATS kits had the lowest levels of bias but also had a strong formation of side products, and as a result performed relatively poorly with biological samples; NEXTflex detected the largest numbers of different miRNAs. The use of a novel type of randomised adapters called MidRand-Like (MRL) adapters and PEG improved the detection of 2’ OMe RNAs both in the TruSeq as well as in the NEXTflex protocol. Conclusions While it is commonly accepted that biases in sRNA library preparation protocols are mainly due to adapter ligation steps, the ligation-free protocols were not the best performing methods. Our modified versions of the TruSeq and NEXTflex protocols provide an improved tool for the study of 2’ OMe RNAs. Electronic supplementary material The online version of this article (10.1186/s12864-018-4491-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Cloelia Dard-Dascot
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, 9198, Gif sur Yvette Cedex, France
| | - Delphine Naquin
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, 9198, Gif sur Yvette Cedex, France
| | - Yves d'Aubenton-Carafa
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, 9198, Gif sur Yvette Cedex, France
| | - Karine Alix
- GQE - Le Moulon, INRA, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Claude Thermes
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, 9198, Gif sur Yvette Cedex, France
| | - Erwin van Dijk
- Institute for Integrative Biology of the Cell, UMR9198, CNRS CEA Univ Paris-Sud, Université Paris-Saclay, 9198, Gif sur Yvette Cedex, France.
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16
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Wei Z, Batagov AO, Schinelli S, Wang J, Wang Y, El Fatimy R, Rabinovsky R, Balaj L, Chen CC, Hochberg F, Carter B, Breakefield XO, Krichevsky AM. Coding and noncoding landscape of extracellular RNA released by human glioma stem cells. Nat Commun 2017; 8:1145. [PMID: 29074968 PMCID: PMC5658400 DOI: 10.1038/s41467-017-01196-x] [Citation(s) in RCA: 334] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 08/25/2017] [Indexed: 02/07/2023] Open
Abstract
Tumor-released RNA may mediate intercellular communication and serve as biomarkers. Here we develop a protocol enabling quantitative, minimally biased analysis of extracellular RNAs (exRNAs) associated with microvesicles, exosomes (collectively called EVs), and ribonucleoproteins (RNPs). The exRNA complexes isolated from patient-derived glioma stem-like cultures exhibit distinct compositions, with microvesicles most closely reflecting cellular transcriptome. exRNA is enriched in small ncRNAs, such as miRNAs in exosomes, and precisely processed tRNA and Y RNA fragments in EVs and exRNPs. EV-enclosed mRNAs are mostly fragmented, and UTRs enriched; nevertheless, some full-length mRNAs are present. Overall, there is less than one copy of non-rRNA per EV. Our results suggest that massive EV/exRNA uptake would be required to ensure functional impact of transferred RNA on brain recipient cells and predict the most impactful miRNAs in such conditions. This study also provides a catalog of diverse exRNAs useful for biomarker discovery and validates its feasibility on cerebrospinal fluid. While circulating DNA has been extensively explored as a potential cancer biomarker, RNA potential has been overlooked so far. Here the authors present a comprehensive analysis of extracellular RNA secreted by glioblastoma cells that could prove a valuable resource for biomarker discovery and a means of intercellular communication.
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Affiliation(s)
- Zhiyun Wei
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, HMS Initiative for RNA Medicine, Boston, MA, 02115, USA
| | - Arsen O Batagov
- Vishuo Biomedical, #3-33 Teletech Park, 20 Science Park Road, Singapore, 117674, Singapore
| | - Sergio Schinelli
- Department of Drug Sciences, University of Pavia, Pavia, 27100, Italy
| | - Jintu Wang
- Beijing Genomics Institute, Shenzhen, 518083, China
| | - Yang Wang
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, HMS Initiative for RNA Medicine, Boston, MA, 02115, USA
| | - Rachid El Fatimy
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, HMS Initiative for RNA Medicine, Boston, MA, 02115, USA
| | - Rosalia Rabinovsky
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, HMS Initiative for RNA Medicine, Boston, MA, 02115, USA
| | - Leonora Balaj
- Department of Neurology and Radiology, Massachusetts General Hospital and Program in Neuroscience, Harvard Medical School, Charlestown, MA, 02129, USA
| | - Clark C Chen
- Neurosurgery Department, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Fred Hochberg
- Department of Neurosurgery, University of California, La Jolla, San Diego, CA, 92093, USA.,Scintillon Institute, San Diego, CA, 92121, USA
| | - Bob Carter
- Department of Neurosurgery, University of California, La Jolla, San Diego, CA, 92093, USA
| | - Xandra O Breakefield
- Department of Neurology and Radiology, Massachusetts General Hospital and Program in Neuroscience, Harvard Medical School, Charlestown, MA, 02129, USA
| | - Anna M Krichevsky
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, HMS Initiative for RNA Medicine, Boston, MA, 02115, USA.
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17
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Bae MG, Kim JY, Choi JK. Frequent hypermethylation of orphan CpG islands with enhancer activity in cancer. BMC Med Genomics 2016; 9 Suppl 1:38. [PMID: 27534853 PMCID: PMC4989897 DOI: 10.1186/s12920-016-0198-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND CpG islands (CGIs) are interspersed DNA sequences that have unusually high CpG ratios and GC contents. CGIs are typically located in the promoter of protein-coding genes. They normally lack DNA methylation but become hypermethylated and induce repression of associated genes in cancer. However, the biological functions of non-promoter CGIs (orphan CGIs) largely remain unclear. RESULTS Here, we identify orphan CGIs that do not map to the promoter of any protein-coding or non-coding transcripts but possess chromatin and transcriptional marks that reflect enhancer activity (termed eCGIs). They exhibit three-dimensional chromatin looping toward multiple target genes with high affinity. Intriguingly, transcription regulators were frequently associated with such CGI-containing enhancers. Remarkably, our analyses in cell lines and clinical tissues showed that eCGIs have more dynamic DNA methylation changes in cancer relative to promoter CGIs. The observed eCGI hypermethylation was accompanied by a loss of enhancer marks and transcriptional inactivation of the target genes. CONCLUSION Our results suggest that eCGIs may constitute a distinct class of enhancers and perform a more instrumental role in tumorigenesis than typical CGIs in gene promoters.
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Affiliation(s)
- Min Gyun Bae
- Department of Bio and Brain Engineering, KAIST, Daejeon, 305-701, Republic of Korea
| | - Jeong Yeon Kim
- Department of Bio and Brain Engineering, KAIST, Daejeon, 305-701, Republic of Korea
| | - Jung Kyoon Choi
- Department of Bio and Brain Engineering, KAIST, Daejeon, 305-701, Republic of Korea.
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18
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Fritz JV, Heintz-Buschart A, Ghosal A, Wampach L, Etheridge A, Galas D, Wilmes P. Sources and Functions of Extracellular Small RNAs in Human Circulation. Annu Rev Nutr 2016; 36:301-36. [PMID: 27215587 PMCID: PMC5479634 DOI: 10.1146/annurev-nutr-071715-050711] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Various biotypes of endogenous small RNAs (sRNAs) have been detected in human circulation, including microRNAs, transfer RNAs, ribosomal RNA, and yRNA fragments. These extracellular sRNAs (ex-sRNAs) are packaged and secreted by many different cell types. Ex-sRNAs exhibit differences in abundance in several disease states and have, therefore, been proposed for use as effective biomarkers. Furthermore, exosome-borne ex-sRNAs have been reported to elicit physiological responses in acceptor cells. Exogenous ex-sRNAs derived from diet (most prominently from plants) and microorganisms have also been reported in human blood. Essential issues that remain to be conclusively addressed concern the (a) presence and sources of exogenous ex-sRNAs in human bodily fluids, (b) detection and measurement of ex-sRNAs in human circulation, (c) selectivity of ex-sRNA export and import, (d) sensitivity and specificity of ex-sRNA delivery to cellular targets, and (e) cell-, tissue-, organ-, and organism-wide impacts of ex-sRNA-mediated cell-to-cell communication. We survey the present state of knowledge of most of these issues in this review.
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MESH Headings
- Animals
- Biological Transport
- Biomarkers/blood
- Cell Communication
- Diet
- Gastrointestinal Microbiome/immunology
- Gene Expression Regulation
- Host-Parasite Interactions
- Host-Pathogen Interactions
- Humans
- Immunity, Innate
- MicroRNAs/blood
- MicroRNAs/metabolism
- Models, Biological
- RNA, Bacterial/blood
- RNA, Bacterial/metabolism
- RNA, Plant/blood
- RNA, Plant/metabolism
- RNA, Ribosomal/blood
- RNA, Ribosomal/metabolism
- RNA, Small Interfering/blood
- RNA, Small Interfering/metabolism
- RNA, Small Untranslated/blood
- RNA, Small Untranslated/metabolism
- RNA, Transfer/blood
- RNA, Transfer/metabolism
- RNA, Viral/blood
- RNA, Viral/metabolism
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Affiliation(s)
- Joëlle V Fritz
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Campus Belval, L-4367 Belvaux, Luxembourg; ,
| | - Anna Heintz-Buschart
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Campus Belval, L-4367 Belvaux, Luxembourg; ,
| | - Anubrata Ghosal
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Linda Wampach
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Campus Belval, L-4367 Belvaux, Luxembourg; ,
| | - Alton Etheridge
- Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122
| | - David Galas
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Campus Belval, L-4367 Belvaux, Luxembourg; ,
- Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122
| | - Paul Wilmes
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Campus Belval, L-4367 Belvaux, Luxembourg; ,
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19
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Buschmann D, Haberberger A, Kirchner B, Spornraft M, Riedmaier I, Schelling G, Pfaffl MW. Toward reliable biomarker signatures in the age of liquid biopsies - how to standardize the small RNA-Seq workflow. Nucleic Acids Res 2016; 44:5995-6018. [PMID: 27317696 PMCID: PMC5291277 DOI: 10.1093/nar/gkw545] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 06/03/2016] [Indexed: 12/21/2022] Open
Abstract
Small RNA-Seq has emerged as a powerful tool in transcriptomics, gene expression profiling and biomarker discovery. Sequencing cell-free nucleic acids, particularly microRNA (miRNA), from liquid biopsies additionally provides exciting possibilities for molecular diagnostics, and might help establish disease-specific biomarker signatures. The complexity of the small RNA-Seq workflow, however, bears challenges and biases that researchers need to be aware of in order to generate high-quality data. Rigorous standardization and extensive validation are required to guarantee reliability, reproducibility and comparability of research findings. Hypotheses based on flawed experimental conditions can be inconsistent and even misleading. Comparable to the well-established MIQE guidelines for qPCR experiments, this work aims at establishing guidelines for experimental design and pre-analytical sample processing, standardization of library preparation and sequencing reactions, as well as facilitating data analysis. We highlight bottlenecks in small RNA-Seq experiments, point out the importance of stringent quality control and validation, and provide a primer for differential expression analysis and biomarker discovery. Following our recommendations will encourage better sequencing practice, increase experimental transparency and lead to more reproducible small RNA-Seq results. This will ultimately enhance the validity of biomarker signatures, and allow reliable and robust clinical predictions.
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Affiliation(s)
- Dominik Buschmann
- Department of Animal Physiology and Immunology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany Institute of Human Genetics, University Hospital, Ludwig-Maximilians-University Munich, Goethestraße 29, 80336 München, Germany
| | - Anna Haberberger
- Department of Animal Physiology and Immunology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany
| | - Benedikt Kirchner
- Department of Animal Physiology and Immunology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany
| | - Melanie Spornraft
- Department of Animal Physiology and Immunology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany
| | - Irmgard Riedmaier
- Eurofins Medigenomix Forensik GmbH, Anzinger Straße 7a, 85560 Ebersberg, Germany Department of Anesthesiology, University Hospital, Ludwig-Maximilians-University Munich, Marchioninistraße 15, 81377 München, Germany
| | - Gustav Schelling
- Department of Physiology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany
| | - Michael W Pfaffl
- Department of Animal Physiology and Immunology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Weihenstephaner Berg 3, 85354 Freising, Germany
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20
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Leenen FAD, Vernocchi S, Hunewald OE, Schmitz S, Molitor AM, Muller CP, Turner JD. Where does transcription start? 5'-RACE adapted to next-generation sequencing. Nucleic Acids Res 2016; 44:2628-45. [PMID: 26615195 PMCID: PMC4824077 DOI: 10.1093/nar/gkv1328] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 11/11/2015] [Accepted: 11/13/2015] [Indexed: 01/27/2023] Open
Abstract
The variability and complexity of the transcription initiation process was examined by adapting RNA ligase-mediated rapid amplification of 5' cDNA ends (5'-RACE) to Next-Generation Sequencing (NGS). We oligo-labelled 5'-m(7)G-capped mRNA from two genes, the simple mono-exonic Beta-2-Adrenoceptor (ADRB2R)and the complex multi-exonic Glucocorticoid Receptor (GR, NR3C1), and detected a variability in TSS location that has received little attention up to now. Transcription was not initiated at a fixed TSS, but from loci of 4 to 10 adjacent nucleotides. Individual TSSs had frequencies from <0.001% to 38.5% of the total gene-specific 5' m(7)G-capped transcripts. ADRB2R used a single locus consisting of 4 adjacent TSSs. Unstimulated, the GR used a total of 358 TSSs distributed throughout 38 loci, that were principally in the 5' UTRs and were spliced using established donor and acceptor sites. Complete demethylation of the epigenetically sensitive GR promoter with 5-azacytidine induced one new locus and 127 TSSs, 12 of which were unique. We induced GR transcription with dexamethasone and Interferon-γ, adding one new locus and 185 additional TSSs distributed throughout the promoter region. In-vitro the TSS microvariability regulated mRNA translation efficiency and the relative abundance of the different GRN-terminal protein isoform levels.
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Affiliation(s)
- Fleur A D Leenen
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg Department of Immunology, Research Institute of Psychobiology, University of Trier, Trier D-54290, Germany
| | - Sara Vernocchi
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg Department of Immunology, Research Institute of Psychobiology, University of Trier, Trier D-54290, Germany
| | - Oliver E Hunewald
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg
| | - Stephanie Schmitz
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg
| | - Anne M Molitor
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg
| | - Claude P Muller
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg Department of Immunology, Research Institute of Psychobiology, University of Trier, Trier D-54290, Germany
| | - Jonathan D Turner
- Department of Infection and Immunity, Luxembourg Institute of Health, Esch-Sur-Alzette L-4354, Grand-Duchy of Luxembourg
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21
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Pankovics P, Boros Á, Reuter G. Novel 5′/3′RACE Method for Amplification and Determination of Single-Stranded RNAs Through Double-Stranded RNA (dsRNA) Intermediates. Mol Biotechnol 2015; 57:974-81. [DOI: 10.1007/s12033-015-9889-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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Fuchs RT, Sun Z, Zhuang F, Robb GB. Bias in ligation-based small RNA sequencing library construction is determined by adaptor and RNA structure. PLoS One 2015; 10:e0126049. [PMID: 25942392 PMCID: PMC4420488 DOI: 10.1371/journal.pone.0126049] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 03/28/2015] [Indexed: 01/01/2023] Open
Abstract
High-throughput sequencing (HTS) has become a powerful tool for the detection of and sequence characterization of microRNAs (miRNA) and other small RNAs (sRNA). Unfortunately, the use of HTS data to determine the relative quantity of different miRNAs in a sample has been shown to be inconsistent with quantitative PCR and Northern Blot results. Several recent studies have concluded that the major contributor to this inconsistency is bias introduced during the construction of sRNA libraries for HTS and that the bias is primarily derived from the adaptor ligation steps, specifically where single stranded adaptors are sequentially ligated to the 3’ and 5’-end of sRNAs using T4 RNA ligases. In this study we investigated the effects of ligation bias by using a pool of randomized ligation substrates, defined mixtures of miRNA sequences and several combinations of adaptors in HTS library construction. We show that like the 3’ adaptor ligation step, the 5’ adaptor ligation is also biased, not because of primary sequence, but instead due to secondary structures of the two ligation substrates. We find that multiple secondary structural factors influence final representation in HTS results. Our results provide insight about the nature of ligation bias and allowed us to design adaptors that reduce ligation bias and produce HTS results that more accurately reflect the actual concentrations of miRNAs in the defined starting material.
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Affiliation(s)
- Ryan T. Fuchs
- RNA Research Division, New England Biolabs Incorporated, Ipswich, Massachusetts, United States of America
| | - Zhiyi Sun
- RNA Research Division, New England Biolabs Incorporated, Ipswich, Massachusetts, United States of America
| | - Fanglei Zhuang
- RNA Research Division, New England Biolabs Incorporated, Ipswich, Massachusetts, United States of America
| | - G. Brett Robb
- RNA Research Division, New England Biolabs Incorporated, Ipswich, Massachusetts, United States of America
- * E-mail:
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23
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Huang Q, Mao Z, Li S, Hu J, Zhu Y. A non-radioactive method for small RNA detection by northern blotting. RICE (NEW YORK, N.Y.) 2014; 7:26. [PMID: 26224555 PMCID: PMC4884002 DOI: 10.1186/s12284-014-0026-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
BACKGROUND Small non-coding RNAs are essential regulators of gene expression at the transcriptional and posttranscriptional levels. High-throughput sequencing has revealed thousands of predicted small RNAs; however, only a few of these have been well characterized. Northern blotting is the most convincing method for small RNA validation. FINDINGS In this study, we improved the Northern blot method by using biotin-labeled probes. miRNAs and siRNAs derived from both Arabidopsis thaliana and Oryza sativa were investigated. The results suggest that this improved method is sensitive and efficient, with approximately 5 μg of total RNA being sufficient for detection. Furthermore, long-term storage of probes labeled in this manner is more convenient, less contaminative and degradative compared with traditional probes. CONCLUSIONS This protocol is an alternative strategy for small RNA detection and represents an efficient means of researching small RNAs.
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Affiliation(s)
- Qi Huang
- />State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072 China
- />Engineering Research Center for Plant Biotechnology and Germplasm, Utilization, Ministry of Education, Wuhan University, Wuhan, 430072 China
| | - Zhinang Mao
- />State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072 China
| | - Shaoqing Li
- />State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072 China
- />Engineering Research Center for Plant Biotechnology and Germplasm, Utilization, Ministry of Education, Wuhan University, Wuhan, 430072 China
| | - Jun Hu
- />State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072 China
- />Engineering Research Center for Plant Biotechnology and Germplasm, Utilization, Ministry of Education, Wuhan University, Wuhan, 430072 China
- />Suzhou institute of Wuhan University, Wuhan, 215000 China
| | - Yingguo Zhu
- />State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072 China
- />Engineering Research Center for Plant Biotechnology and Germplasm, Utilization, Ministry of Education, Wuhan University, Wuhan, 430072 China
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24
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Jackson TJ, Spriggs RV, Burgoyne NJ, Jones C, Willis AE. Evaluating bias-reducing protocols for RNA sequencing library preparation. BMC Genomics 2014; 15:569. [PMID: 25001197 PMCID: PMC4117970 DOI: 10.1186/1471-2164-15-569] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 06/26/2014] [Indexed: 12/17/2022] Open
Abstract
Background Next-generation sequencing does not yield fully unbiased estimates for read abundance, which may impact on the conclusions that can be drawn from sequencing data. The ligation step in RNA sequencing library generation is a known source of bias, motivating developments in enzyme technology and library construction protocols. We present the first comparison of the standard duplex adaptor protocol supplied by Life Technologies for use on the Ion Torrent PGM with an alternate single adaptor approach involving CircLigase (CircLig protocol). A correlation between over-representation in sequenced libraries and degree of secondary structure has been reported previously, therefore we also investigated whether bias could be reduced by ligation with an enzyme that functions at a temperature not permissive for such structure. Results A pool of small RNA fragments of known composition was converted into a sequencing library using one of three protocols and sequenced on an Ion Torrent PGM. The CircLig protocol resulted in less over-representation of specific sequences than the standard protocol. Over-represented sequences are more likely to be predicted to have secondary structure and to co-fold with adaptor sequences. However, use of the thermostable ligase Methanobacterium thermoautotrophicum RNA ligase K97A (Mth K97A) was not sufficient to reduce bias. Conclusions The single adaptor CircLigase-based approach significantly reduces, but does not eliminate, bias in Ion Torrent data. Ligases that function at temperatures to remove the possible influence of secondary structure on library generation may be of value, although Mth K97A is not effective in this case. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-569) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Thomas J Jackson
- Medical Research Council Toxicology Unit, Lancaster Rd, Leicester LE1 9HN, UK.
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25
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Terminator oligo blocking efficiently eliminates rRNA from Drosophila small RNA sequencing libraries. Biotechniques 2014; 55:269-72. [PMID: 24215643 DOI: 10.2144/000114102] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/06/2013] [Indexed: 11/23/2022] Open
Abstract
A large number of methods are available to deplete ribosomal RNA reads from high-throughput RNA sequencing experiments. Such methods are critical for sequencing Drosophila small RNAs between 20 and 30 nucleotides because size selection is not typically sufficient to exclude the highly abundant class of 30 nucleotide 2S rRNA. Here we demonstrate that pre-annealing terminator oligos complimentary to Drosophila 2S rRNA prior to 5' adapter ligation and reverse transcription efficiently depletes 2S rRNA sequences from the sequencing reaction in a simple and inexpensive way. This depletion is highly specific and is achieved with minimal perturbation of miRNA and piRNA profiles.
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26
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Small RNA cloning and sequencing strategy affects host and viral microRNA expression signatures. J Biotechnol 2014; 181:35-44. [PMID: 24746587 DOI: 10.1016/j.jbiotec.2014.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 03/26/2014] [Accepted: 04/04/2014] [Indexed: 01/04/2023]
Abstract
The establishment of the microRNA (miRNA) expression signatures is the basic element to investigate the role played by these regulatory molecules in the biology of an organism. Marek's disease virus 1 (MDV-1) is an avian herpesvirus that naturally infects chicken and induces T cells lymphomas. During latency, MDV-1, like other herpesviruses, expresses a limited subset of transcripts. These include three miRNA clusters. Several studies identified the expression of virus and host encoded miRNAs from MDV-1 infected cell cultures and chickens. But a high discrepancy was observed when miRNA cloning frequencies obtained from different cloning and sequencing protocols were compared. Thus, we analyzed the effect of small RNA library preparation and sequencing on the miRNA frequencies obtained from the same RNA samples collected during MDV-1 infection of chicken at different steps of the oncoviral pathogenesis. Qualitative and quantitative variations were found in the data, depending on the strategy used. One of the mature miRNA derived from the latency-associated-transcript (LAT), mdv1-miR-M7-5p, showed the highest variation. Its cloning frequency was 50% of the viral miRNA counts when a small scale sequencing approach was used. Its frequency was 100 times less abundant when determined through the deep sequencing approach. Northern blot analysis showed a better correlation with the miRNA frequencies found by the small scale sequencing approach. By analyzing the cellular miRNA repertoire, we also found a gap between the two sequencing approaches. Collectively, our study indicates that next-generation sequencing data considered alone are limited for assessing the absolute copy number of transcripts. Thus, the quantification of small RNA should be addressed by compiling data obtained by using different techniques such as microarrays, qRT-PCR and NB analysis in support of high throughput sequencing data. These observations should be considered when miRNA variations are studied prior addressing functional studies.
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27
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Library preparation methods for next-generation sequencing: tone down the bias. Exp Cell Res 2014; 322:12-20. [PMID: 24440557 DOI: 10.1016/j.yexcr.2014.01.008] [Citation(s) in RCA: 243] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 01/07/2014] [Accepted: 01/08/2014] [Indexed: 11/22/2022]
Abstract
Next-generation sequencing (NGS) has caused a revolution in biology. NGS requires the preparation of libraries in which (fragments of) DNA or RNA molecules are fused with adapters followed by PCR amplification and sequencing. It is evident that robust library preparation methods that produce a representative, non-biased source of nucleic acid material from the genome under investigation are of crucial importance. Nevertheless, it has become clear that NGS libraries for all types of applications contain biases that compromise the quality of NGS datasets and can lead to their erroneous interpretation. A detailed knowledge of the nature of these biases will be essential for a careful interpretation of NGS data on the one hand and will help to find ways to improve library quality or to develop bioinformatics tools to compensate for the bias on the other hand. In this review we discuss the literature on bias in the most common NGS library preparation protocols, both for DNA sequencing (DNA-seq) as well as for RNA sequencing (RNA-seq). Strikingly, almost all steps of the various protocols have been reported to introduce bias, especially in the case of RNA-seq, which is technically more challenging than DNA-seq. For each type of bias we discuss methods for improvement with a view to providing some useful advice to the researcher who wishes to convert any kind of raw nucleic acid into an NGS library.
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28
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Abstract
Since their discovery about 20 years ago, small RNAs have been shown to play a critical role in a myriad of biological processes. The greater availability of high-throughput sequencing has been invaluable to furthering our understanding of small RNAs as regulatory molecules. In particular, these sequencing technologies have been crucial in understanding the role of small RNAs in reproductive tissues, where millions of individual sequences are generated. In this context, high-throughput sequencing provides the requisite level of resolution that other procedures, like northern blotting, would not be able to achieve. Here, we describe a protocol for the preparation of small RNA libraries for sequencing using the Solexa/Illumina technology.
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Affiliation(s)
- Jon McGinn
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
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29
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Moreno-Mateos MA, Barragán V, Torres B, Rodríguez-Mateo C, Méndez-Vidal C, Berezikov E, Mudduluru G, Allgayer H, Pintor-Toro JA. Novel small RNA expression libraries uncover hsa-miR-30b and hsa-miR-30c as important factors in anoikis resistance. RNA (NEW YORK, N.Y.) 2013; 19:1711-1725. [PMID: 24129493 PMCID: PMC3884670 DOI: 10.1261/rna.039461.113] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 08/30/2013] [Indexed: 06/02/2023]
Abstract
MicroRNAs (miRNAs) have been widely studied in order to elucidate their biological functions. MicroRNA microarrays or miRNA overexpression libraries generated by synthesis and cloning of individual miRNAs have been used to study their different roles. In this work, we have developed a novel methodology to express mature miRNAs and other small RNAs from a double convergent RNA polymerase III promoter. We show that the generated miRNAs function similarly to those processed from primary transcripts or pri-miRNAs. This system allowed us to produce a lentiviral library expressing the whole population of small RNAs present in a metastatic cell line. A functional screening using this library led to the identification of hsa-miR-30b and hsa-miR-30c as negative regulators of cell death induced by loss of attachment (anoikis). Importantly, we demonstrated that the acquisition of anoikis resistance via these miRNAs is achieved through down-regulation of caspase 3 expression. Moreover, overexpression of these miRNAs resulted in a decrease of other types of caspase 3-dependent cell death and enhanced the survival of MCF10A acinar cells in morphogenesis assays, suggesting a putative role as oncomirs. In summary, this novel methodology provides a powerful and effective way for identifying novel small RNAs involved in a particular biological process.
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Affiliation(s)
- Miguel A. Moreno-Mateos
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
| | - Verónica Barragán
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
| | - Belén Torres
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
| | - Cristina Rodríguez-Mateo
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
| | - Cristina Méndez-Vidal
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
| | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, 9713AV Groningen, The Netherlands
| | - Giridhar Mudduluru
- Department of Experimental Surgery Mannheim/Molecular Oncology of Solid Tumors, DKFZ and University of Heidelberg, 68167 Heidelberg, Germany
| | - Heike Allgayer
- Department of Experimental Surgery Mannheim/Molecular Oncology of Solid Tumors, DKFZ and University of Heidelberg, 68167 Heidelberg, Germany
| | - José A. Pintor-Toro
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, CABIMER-CSIC, 41092 Sevilla, Spain
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30
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Raabe CA, Tang TH, Brosius J, Rozhdestvensky TS. Biases in small RNA deep sequencing data. Nucleic Acids Res 2013; 42:1414-26. [PMID: 24198247 PMCID: PMC3919602 DOI: 10.1093/nar/gkt1021] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
High-throughput RNA sequencing (RNA-seq) is considered a powerful tool for novel gene discovery and fine-tuned transcriptional profiling. The digital nature of RNA-seq is also believed to simplify meta-analysis and to reduce background noise associated with hybridization-based approaches. The development of multiplex sequencing enables efficient and economic parallel analysis of gene expression. In addition, RNA-seq is of particular value when low RNA expression or modest changes between samples are monitored. However, recent data uncovered severe bias in the sequencing of small non-protein coding RNA (small RNA-seq or sRNA-seq), such that the expression levels of some RNAs appeared to be artificially enhanced and others diminished or even undetectable. The use of different adapters and barcodes during ligation as well as complex RNA structures and modifications drastically influence cDNA synthesis efficacies and exemplify sources of bias in deep sequencing. In addition, variable specific RNA G/C-content is associated with unequal polymerase chain reaction amplification efficiencies. Given the central importance of RNA-seq to molecular biology and personalized medicine, we review recent findings that challenge small non-protein coding RNA-seq data and suggest approaches and precautions to overcome or minimize bias.
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Affiliation(s)
- Carsten A Raabe
- Institute of Experimental Pathology (ZMBE), University of Muenster, Von-Esmarch-Strasse 56, 48149 Muenster, Germany and Advanced Medical and Dental Institute (AMDI), Universiti Sains Malaysia, 13200 Penang, Malaysia
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