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Gurung C, Fendereski M, Sapkota K, Guo J, Huang F, Guo YL. Dicer represses the interferon response and the double-stranded RNA-activated protein kinase pathway in mouse embryonic stem cells. J Biol Chem 2021; 296:100264. [PMID: 33837743 PMCID: PMC7948645 DOI: 10.1016/j.jbc.2021.100264] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 01/04/2021] [Accepted: 01/05/2021] [Indexed: 02/07/2023] Open
Abstract
Recent studies have demonstrated that embryonic stem cells (ESCs) are deficient in expressing type I interferons (IFN), the cytokines that play key roles in antiviral responses. However, the underlying molecular mechanisms and biological implications of this finding are poorly understood. In this study, we developed a synthetic RNA-based assay that can simultaneously assess multiple forms of antiviral responses. Dicer is an enzyme essential for RNA interference (RNAi), which is used as a major antiviral mechanism in invertebrates. RNAi activity is detected in wild-type ESCs but is abolished in Dicer knockout ESCs (D−/−ESCs) as expected. Surprisingly, D−/−ESCs have gained the ability to express IFN, which is otherwise deficient in wild-type ESCs. Furthermore, D−/−ESCs have constitutively active double-stranded RNA (dsRNA)-activated protein kinase (PKR), an enzyme that is also involved in antiviral response. D−/−ESCs show increased sensitivity to the cytotoxicity resulting from RNA transfection. The effects of dsRNA can be partly replicated with a synthetic B2RNA corresponding to the retrotransposon B2 short interspersed nuclear element. B2RNA has secondary structure features of dsRNA and accumulates in D−/−ESCs, suggesting that B2RNA could be a cellular RNA that activates PKR and contributes to the decreased cell proliferation and viability of D−/−ESCs. Treatment of D−/−ESCs with a PKR inhibitor and IFNβ-neutralizing antibodies increased cell proliferation rate and cell viability. Based on these findings, we propose that, in ESCs, Dicer acts as a repressor of antiviral responses and plays a key role in the maintenance of proliferation, viability, and pluripotency of ESCs.
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Affiliation(s)
- Chandan Gurung
- Department of Cell and Molecular Biology, The University of Southern Mississippi, Hattiesburg, Mississippi, USA
| | - Mona Fendereski
- Department of Cell and Molecular Biology, The University of Southern Mississippi, Hattiesburg, Mississippi, USA
| | - Krishna Sapkota
- Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi, USA
| | - Jason Guo
- Department of Cell and Molecular Biology, The University of Southern Mississippi, Hattiesburg, Mississippi, USA
| | - Faqing Huang
- Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi, USA
| | - Yan-Lin Guo
- Department of Cell and Molecular Biology, The University of Southern Mississippi, Hattiesburg, Mississippi, USA.
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2
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Ma Q, Mo G, Tan Y. Micro RNAs and the biological clock: a target for diseases associated with a loss of circadian regulation. Afr Health Sci 2020; 20:1887-1894. [PMID: 34394254 PMCID: PMC8351835 DOI: 10.4314/ahs.v20i4.46] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Background Circadian clocks are self-sustaining oscillators that coordinate behavior and physiology over a 24 hour period, achieving time-dependent homeostasis with the external environment. The molecular clocks driving circadian rhythmic changes are based on intertwined transcriptional/translational feedback loops that combine with a range of environmental and metabolic stimuli to generate daily internal programing. Understanding how biological rhythms are generated throughout the body and the reasons for their dysregulation can provide avenues for temporally directed therapeutics. Summary In recent years, microRNAs have been shown to play important roles in the regulation of the circadian clock, particularly in Drosophila, but also in some small animal and human studies. This review will summarize our current understanding of the role of miRNAs during clock regulation, with a particular focus on the control of clock regulated gene expression.
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Affiliation(s)
- Qianwen Ma
- Gynecology department, Zhenjiang Hospital Affiliated to Nanjing University of Chinese Medicine (Zhenjiang Hospital of Traditional Chinese Medicine), Zhenjiang, China
- Reproductive medicine department, Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, China
| | - Genlin Mo
- Advanced manufacturing institution, Jiangsu University, Zhenjiang, China
| | - Yong Tan
- Reproductive medicine department, Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, China
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3
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Borgohain MP, Haridhasapavalan KK, Dey C, Adhikari P, Thummer RP. An Insight into DNA-free Reprogramming Approaches to Generate Integration-free Induced Pluripotent Stem Cells for Prospective Biomedical Applications. Stem Cell Rev Rep 2020; 15:286-313. [PMID: 30417242 DOI: 10.1007/s12015-018-9861-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
More than a decade ago, a pioneering study reported generation of induced Pluripotent Stem Cells (iPSCs) by ectopic expression of a cocktail of reprogramming factors in fibroblasts. This study has revolutionized stem cell research and has garnered immense interest from the scientific community globally. iPSCs hold tremendous potential for understanding human developmental biology, disease modeling, drug screening and discovery, and personalized cell-based therapeutic applications. The seminal study identified Oct4, Sox2, Klf4 and c-Myc as a potent combination of genes to induce reprogramming. Subsequently, various reprogramming factors were identified by numerous groups. Most of these studies have used integrating viral vectors to overexpress reprogramming factors in somatic cells to derive iPSCs. However, these techniques restrict the clinical applicability of these cells as they may alter the genome due to random viral integration resulting in insertional mutagenesis and tumorigenicity. To circumvent this issue, alternative integration-free reprogramming approaches are continuously developed that eliminate the risk of genomic modifications and improve the prospects of iPSCs from lab to clinic. These methods establish that integration of transgenes into the genome is not essential to induce pluripotency in somatic cells. This review provides a comprehensive overview of the most promising DNA-free reprogramming techniques that have the potential to derive integration-free iPSCs without genomic manipulation, such as sendai virus, recombinant proteins, microRNAs, synthetic messenger RNA and small molecules. The understanding of these approaches shall pave a way for the generation of clinical-grade iPSCs. Subsequently, these iPSCs can be differentiated into desired cell type(s) for various biomedical applications.
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Affiliation(s)
- Manash P Borgohain
- Laboratory for Stem Cell Engineering and Regenerative Medicine, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Krishna Kumar Haridhasapavalan
- Laboratory for Stem Cell Engineering and Regenerative Medicine, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Chandrima Dey
- Laboratory for Stem Cell Engineering and Regenerative Medicine, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Poulomi Adhikari
- Laboratory for Stem Cell Engineering and Regenerative Medicine, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Rajkumar P Thummer
- Laboratory for Stem Cell Engineering and Regenerative Medicine, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India.
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4
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Erharter A, Rizzi S, Mertens J, Edenhofer F. Take the shortcut - direct conversion of somatic cells into induced neural stem cells and their biomedical applications. FEBS Lett 2019; 593:3353-3369. [PMID: 31663609 PMCID: PMC6916337 DOI: 10.1002/1873-3468.13656] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 10/12/2019] [Accepted: 10/14/2019] [Indexed: 12/20/2022]
Abstract
Second-generation reprogramming of somatic cells directly into the cell type of interest avoids induction of pluripotency and subsequent cumbersome differentiation procedures. Several recent studies have reported direct conversion of human somatic cells into stably proliferating induced neural stem cells (iNSCs). Importantly, iNSCs are easier, faster, and more cost-efficient to generate than induced pluripotent stem cells (iPSCs), and also have a higher level of clinical safety. Stably, self-renewing iNSCs can be derived from different cellular sources, such as skin fibroblasts and peripheral blood mononuclear cells, and readily differentiate into neuronal and glial lineages that are indistinguishable from their iPSC-derived counterparts or from NSCs isolated from primary tissues. This review focuses on the derivation and characterization of iNSCs and their biomedical applications. We first outline different approaches to generate iNSCs and then discuss the underlying molecular mechanisms. Finally, we summarize the preclinical validation of iNSCs to highlight that these cells are promising targets for disease modeling, autologous cell therapy, and precision medicine.
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Affiliation(s)
- Anita Erharter
- Department of Molecular Biology & CMBIGenomics, Stem Cell Biology & Regenerative MedicineLeopold‐Franzens‐University InnsbruckAustria
| | - Sandra Rizzi
- Department of Molecular Biology & CMBIGenomics, Stem Cell Biology & Regenerative MedicineLeopold‐Franzens‐University InnsbruckAustria
- Institute of PharmacologyMedical University InnsbruckAustria
| | - Jerome Mertens
- Department of Molecular Biology & CMBIGenomics, Stem Cell Biology & Regenerative MedicineLeopold‐Franzens‐University InnsbruckAustria
| | - Frank Edenhofer
- Department of Molecular Biology & CMBIGenomics, Stem Cell Biology & Regenerative MedicineLeopold‐Franzens‐University InnsbruckAustria
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5
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Fragkos M, Barra V, Egger T, Bordignon B, Lemacon D, Naim V, Coquelle A. Dicer prevents genome instability in response to replication stress. Oncotarget 2019; 10:4407-4423. [PMID: 31320994 PMCID: PMC6633883 DOI: 10.18632/oncotarget.27034] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 06/05/2019] [Indexed: 11/25/2022] Open
Abstract
Dicer, an endoribonuclease best-known for its role in microRNA biogenesis and RNA interference pathway, has been shown to play a role in the DNA damage response and repair of double-stranded DNA breaks (DSBs) in mammalian cells. However, it remains unknown whether Dicer is also important to preserve genome integrity upon replication stress. To address this question, we focused our study on common fragile sites (CFSs), which are susceptible to breakage after replication stress. We show that inhibition of the Dicer pathway leads to an increase in CFS expression upon induction of replication stress and to an accumulation of 53BP1 nuclear bodies, indicating transmission of replication-associated damage. We also show that in absence of a functional Dicer or Drosha, the assembly into nuclear foci of the Fanconi anemia (FA) protein FANCD2 and of the replication and checkpoint factor TopBP1 in response to replication stress is impaired, and the activation of the S-phase checkpoint is defective. Based on these results, we propose that Dicer pre-vents genomic instability after replication stress, by allowing the proper recruitment to stalled forks of proteins that are necessary to maintain replication fork stability and activate the S-phase checkpoint, thus limiting cells from proceeding into mitosis with under-replicated DNA.
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Affiliation(s)
- Michalis Fragkos
- IRCM, Institut de Recherche en Cancérologie de Montpellier, INSERM U1194, Université de Montpellier, Institut Régional du Cancer de Montpellier, Montpellier, France.,Laboratory of Genetic Instability and Oncogenesis, UMR 8200 CNRS, University Paris-Sud, Gustave Roussy, Villejuif, France.,These authors contributed equally to this work
| | - Viviana Barra
- Laboratory of Genetic Instability and Oncogenesis, UMR 8200 CNRS, University Paris-Sud, Gustave Roussy, Villejuif, France.,These authors contributed equally to this work
| | - Tom Egger
- IRCM, Institut de Recherche en Cancérologie de Montpellier, INSERM U1194, Université de Montpellier, Institut Régional du Cancer de Montpellier, Montpellier, France
| | - Benoit Bordignon
- IRCM, Institut de Recherche en Cancérologie de Montpellier, INSERM U1194, Université de Montpellier, Institut Régional du Cancer de Montpellier, Montpellier, France
| | - Delphine Lemacon
- IRCM, Institut de Recherche en Cancérologie de Montpellier, INSERM U1194, Université de Montpellier, Institut Régional du Cancer de Montpellier, Montpellier, France.,Present address: Department of Biochemistry and Molecular Biology, Doisy Research Center, St. Louis, MO, USA
| | - Valeria Naim
- Laboratory of Genetic Instability and Oncogenesis, UMR 8200 CNRS, University Paris-Sud, Gustave Roussy, Villejuif, France.,These authors contributed equally to this work
| | - Arnaud Coquelle
- IRCM, Institut de Recherche en Cancérologie de Montpellier, INSERM U1194, Université de Montpellier, Institut Régional du Cancer de Montpellier, Montpellier, France
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6
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Mahabadi JA, Sabzalipoor H, Nikzad H, Seyedhosseini E, Enderami SE, Gheibi Hayat SM, Sahebkar A. The role of microRNAs in embryonic stem cell and induced pluripotent stem cell differentiation in male germ cells. J Cell Physiol 2018; 234:12278-12289. [PMID: 30536380 DOI: 10.1002/jcp.27990] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/21/2018] [Indexed: 12/12/2022]
Abstract
New perspectives have been opened by advances in stem cell research for reproductive and regenerative medicine. Several different cell types can be differentiated from stem cells (SCs) under suitable in vitro and in vivo conditions. The differentiation of SCs into male germ cells has been reported by many groups. Due to their unlimited pluripotency and self-renewal, embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can be used as valuable tools for drug delivery, disease modeling, developmental studies, and cell-based therapies in regenerative medicine. The unique features of SCs are controlled by a dynamic interplay between extrinsic signaling pathways, and regulations at epigenetic, transcriptional and posttranscriptional levels. In recent years, significant progress has been made toward better understanding of the functions and expression of specific microRNAs (miRNAs) in the maintenance of SC pluripotency. miRNAs are short noncoding molecules, which play a functional role in the regulation of gene expression. In addition, the important regulatory role of miRNAs in differentiation and dedifferentiation has been recently demonstrated. A balance between differentiation and pluripotency is maintained by miRNAs in the embryo and stem cells. This review summarizes the recent findings about the role of miRNAs in the regulation of self-renewal and pluripotency of iPSCs and ESCs, as well as their impact on cellular reprogramming and stem cell differentiation into male germ cells.
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Affiliation(s)
- Javad Amini Mahabadi
- Gametogenesis Research Center, Kashan University of Medical Sciences, Kashan, Iran
| | - Hamed Sabzalipoor
- Department of Nanobiotechnology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Hossein Nikzad
- Gametogenesis Research Center, Kashan University of Medical Sciences, Kashan, Iran
| | - Elahe Seyedhosseini
- Gametogenesis Research Center, Kashan University of Medical Sciences, Kashan, Iran
| | - Seyed Ehsan Enderami
- Department of Medical Biotechnology and Nanotechnology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
| | - Seyed Mohammad Gheibi Hayat
- Department of Medical Genetics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Amirhosein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran.,Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
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7
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Nourse J, Braun J, Lackner K, Hüttelmaier S, Danckwardt S. Large-scale identification of functional microRNA targeting reveals cooperative regulation of the hemostatic system. J Thromb Haemost 2018; 16:2233-2245. [PMID: 30207063 DOI: 10.1111/jth.14290] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Indexed: 12/22/2022]
Abstract
Essentials MicroRNAs (miRNAs) regulate the molecular networks controlling biological functions such as hemostasis. We utilized novel methods to analyze miRNA-mediated regulation of the hemostatic system. 52 specific miRNA interactions with 11 key hemostatic associated genes were identified. Functionality and drugability of miRNA-19b-3p against antithrombin were demonstrated in vivo. SUMMARY: Background microRNAs (miRNAs) confer robustness to complex molecular networks regulating biological functions. However, despite the involvement of miRNAs in almost all biological processes, and the importance of the hemostatic system for a multitude of actions in and beyond blood coagulation, the role of miRNAs in hemostasis is poorly defined. Objectives Here we comprehensively illuminate miRNA-mediated regulation of the hemostatic system in an unbiased manner. Methods In contrast to widely applied association studies, we used an integrative screening approach that combines functional aspects of miRNA silencing with biophysical miRNA interaction based on RNA pull-downs (miTRAP) coupled to next-generation sequencing. Results Examination of a panel of 27 hemostasis-associated gene 3'UTRs revealed the majority to possess substantial Dicer-dependent silencing capability, suggesting functional miRNA targeting. miTRAP revealed 150 specific miRNA interactions with 14 3'UTRs, of which 52, involving 40 miRNAs, were functionally confirmed. This includes cooperative miRNA regulation of key hemostatic genes comprising procoagulant (F7, F8, F11, FGA, FGG and KLKB1) and anticoagulant (SERPINA10, PROZ, SERPIND1 and SERPINC1) as well as fibrinolytic (PLG) components. Bioinformatic analysis of miRNA functionality reveals established and potential novel links between the hemostatic system and other pathologies, such as cancer, bone metabolism and renal function. Conclusions Our findings provide, along with an in-vivo proof of concept, deep insights into the network of miRNAs regulating the hemostatic system and present a foundation for biomarker discovery and novel targeted therapeutics for correction of de-regulated hemostasis and associated processes in the future. A repository of the miRNA targetome covering 14 hemostatic components is provided.
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Affiliation(s)
- J Nourse
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - J Braun
- Institute of Molecular Medicine, Martin Luther University Halle (Saale), Halle, Germany
| | - K Lackner
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - S Hüttelmaier
- Institute of Molecular Medicine, Martin Luther University Halle (Saale), Halle, Germany
| | - S Danckwardt
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
- German Center for Cardiovascular Research (DZHK), Rhine-Main, University Medical Center, Mainz, Germany
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8
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Kanellopoulou C, Muljo SA. Posttranscriptional (Re)programming of Cell Fate: Examples in Stem Cells, Progenitor, and Differentiated Cells. Front Immunol 2018; 9:715. [PMID: 29686685 PMCID: PMC5900001 DOI: 10.3389/fimmu.2018.00715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 03/22/2018] [Indexed: 01/21/2023] Open
Abstract
How a single genome can give rise to many different transcriptomes and thus all the different cell lineages in the human body is a fundamental question in biology. While signaling pathways, transcription factors, and chromatin architecture, to name a few determinants, have been established to play critical roles, recently, there is a growing appreciation of the roles of non-coding RNAs and RNA-binding proteins in controlling cell fates posttranscriptionally. Thus, it is vital that these emerging players are also integrated into models of gene regulatory networks that underlie programs of cellular differentiation. Sometimes, we can leverage knowledge about such posttranscriptional circuits to reprogram patterns of gene expression in meaningful ways. Here, we review three examples from our work.
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Affiliation(s)
- Chrysi Kanellopoulou
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Stefan A Muljo
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
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9
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Ferreira AF, Calin GA, Picanço-Castro V, Kashima S, Covas DT, de Castro FA. Hematopoietic stem cells from induced pluripotent stem cells - considering the role of microRNA as a cell differentiation regulator. J Cell Sci 2018; 131:131/4/jcs203018. [PMID: 29467236 DOI: 10.1242/jcs.203018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Although hematopoietic stem cell (HSC) therapy for hematological diseases can lead to a good outcome from the clinical point of view, the limited number of ideal donors, the comorbidity of patients and the increasing number of elderly patients may limit the application of this therapy. HSCs can be generated from induced pluripotent stem cells (iPSCs), which requires the understanding of the bone marrow and liver niches components and function in vivo iPSCs have been extensively applied in several studies involving disease models, drug screening and cellular replacement therapies. However, the somatic reprogramming by transcription factors is a low-efficiency process. Moreover, the reprogramming process is also regulated by microRNAs (miRNAs), which modulate the expression of the transcription factors OCT-4 (also known as POU5F1), SOX-2, KLF-4 and MYC, leading somatic cells to a pluripotent state. In this Review, we present an overview of the challenges of cell reprogramming protocols with regard to HSC generation from iPSCs, and highlight the potential role of miRNAs in cell reprogramming and in the differentiation of induced pluripotent stem cells.
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Affiliation(s)
- Aline F Ferreira
- Department of Clinical Analysis, Toxicology and Food Science, School of Pharmaceutical Sciences, University of São Paulo (USP), Ribeirão Preto, São Paulo 14040-903, Brazil
| | - George A Calin
- Department of Experimental Therapeutics, MD Anderson Cancer Center, Houston, TX 77054, USA
| | - Virgínia Picanço-Castro
- Center of Cell Therapy, Regional Blood Center of Ribeirão Preto, Ribeirão Preto, São Paulo 14051-140, Brazil
| | - Simone Kashima
- Center of Cell Therapy, Regional Blood Center of Ribeirão Preto, Ribeirão Preto, São Paulo 14051-140, Brazil
| | - Dimas T Covas
- Center of Cell Therapy, Regional Blood Center of Ribeirão Preto, Ribeirão Preto, São Paulo 14051-140, Brazil.,Department of Internal Medicine, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, São Paulo 14049-900, Brazil
| | - Fabiola A de Castro
- Department of Clinical Analysis, Toxicology and Food Science, School of Pharmaceutical Sciences, University of São Paulo (USP), Ribeirão Preto, São Paulo 14040-903, Brazil
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10
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Gadd45a opens up the promoter regions of miR-295 facilitating pluripotency induction. Cell Death Dis 2017; 8:e3107. [PMID: 29022923 PMCID: PMC5682663 DOI: 10.1038/cddis.2017.497] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 08/13/2017] [Accepted: 08/31/2017] [Indexed: 12/13/2022]
Abstract
MicroRNAs (miRNAs) play crucial roles in the establishment of pluripotent state by controlling pluripotent network. However, the molecular mechanisms controlling miRNAs during somatic cell reprogramming remain obscure. In this study, we show Gadd45a (growth arrest and DNA-damage-inducible protein 45a) enhances reprogramming by activating miR-295. Furthermore, we show that Gadd45a binds the promoter regions of miR-295. Nuclease accessibility assay indicates that Gadd45a opens the promoter regions of miR-295. Levels of H3K9Ac and H3K27Ac on the promoter regions of miR-295 were also increased. In conclusion, our results indicate that Gadd45a relaxes the promoter regions of miR-295 and promotes the expression of miR-295 during reprogramming, implying a concise mechanism of Gadd45a and miR-290 cluster cooperation in cell-fate determination.
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11
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Adlakha YK, Seth P. The expanding horizon of MicroRNAs in cellular reprogramming. Prog Neurobiol 2016; 148:21-39. [PMID: 27979736 DOI: 10.1016/j.pneurobio.2016.11.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 08/07/2016] [Accepted: 11/27/2016] [Indexed: 12/21/2022]
Abstract
Research over the last few years in cellular reprogramming has enlightened the magical potential of microRNAs (miRNAs) in changing the cell fate from somatic to pluripotent. Recent investigations on exploring the role(s) of miRNAs in somatic cell reprogramming revealed that they target a wide range of molecules and refine their protein output. This leads to fine tuning of distinct cellular processes including cell cycle, signalling pathways, transcriptional activation/silencing and epigenetic modelling. The concerted actions of miRNA on different pathways simultaneously strengthen the transition from a differentiated to de-differentiated state. Despite the well characterized transcriptional and epigenetic machinery underlying somatic cell reprogramming, the molecular circuitry for miRNA mediated cellular reprogramming is rather fragmented. This review summarizes recent findings addressing the role of miRNAs in inducing or suppressing reprogramming thus uncovering novel potentials of miRNAs as regulators of induced pluripotency maintenance, establishment and associated signalling pathways. Our bioinformatic analysis sheds light on various unexplored biological processes and pathways associated with reprogramming inducing miRNAs, thus helps in identifying roadblocks to full reprogramming. Specifically, the biological significance of highly conserved and most studied miRNA cluster, i.e. miR-302-367, in reprogramming is also highlighted. Further, roles of miRNAs in the differentiation of neurons from iPSCs are discussed. A recent approach of direct conversion or transdifferentiation of differentiated cells into neurons by miRNAs is also elaborated. This approach is now widely gaining impetus for the generation of neurological patient's brain cells directly from his/her somatic cells in an efficient and safe manner. Thus, decoding the intricate circuitry between miRNAs and other gene regulatory networks will not only uncover novel pathways in the direct reprogramming of somatic cells but will also open new avenues in stem cell biology.
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Affiliation(s)
- Yogita K Adlakha
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, 122051, India.
| | - Pankaj Seth
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, 122051, India
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12
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Liu Z, Skamagki M, Kim K, Zhao R. Canonical MicroRNA Activity Facilitates but May Be Dispensable for Transcription Factor-Mediated Reprogramming. Stem Cell Reports 2016; 5:1119-1127. [PMID: 26651605 PMCID: PMC4682342 DOI: 10.1016/j.stemcr.2015.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 11/03/2015] [Accepted: 11/12/2015] [Indexed: 12/13/2022] Open
Abstract
MicroRNAs (miRNAs) are important regulators of reprogramming of somatic cells into induced pluripotent stem cells (iPSCs); however, it is unclear whether miRNAs are required for reprogramming and whether miRNA activity as a whole facilitates reprogramming. Here we report on successful reprogramming of mouse fibroblasts and neural stem cells (NSCs) lacking Dgcr8, a factor required for the biogenesis of canonical miRNAs, by Yamanaka factors, albeit at decreased efficiencies. Though iPSCs derived from Dgcr8-deficient mouse fibroblasts or NSCs were able to self-renew and expressed pluripotency-associated markers, they exhibited poor differentiation potential into mature somatic tissues, similar to Dgcr8−/− embryonic stem cells. The differentiation defects could be rescued with expression of DGCR8 cDNA. Our data demonstrate that while miRNA activity as a whole facilitates reprogramming, canonical miRNA may be dispensable in the derivation of iPSCs. Reprogramming may be initiated and maintained solely by transcription factors miRNA activity as a whole facilitates reprogramming Canonical miRNAs may be dispensable for reprogramming
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Affiliation(s)
- Zhong Liu
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Maria Skamagki
- Cancer Biology and Genetics Program, Center for Cell Engineering, Center for Stem Cell Biology, Sloan-Kettering Institute, Cell and Developmental Biology Program, Weill Medical College of Cornell University, New York, NY 10065, USA
| | - Kitai Kim
- Cancer Biology and Genetics Program, Center for Cell Engineering, Center for Stem Cell Biology, Sloan-Kettering Institute, Cell and Developmental Biology Program, Weill Medical College of Cornell University, New York, NY 10065, USA.
| | - Rui Zhao
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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Cruz-Santos MC, Aragón-Raygoza A, Espinal-Centeno A, Arteaga-Vázquez M, Cruz-Hernández A, Bako L, Cruz-Ramírez A. The Role of microRNAs in Animal Cell Reprogramming. Stem Cells Dev 2016; 25:1035-49. [PMID: 27224014 DOI: 10.1089/scd.2015.0359] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Our concept of cell reprogramming and cell plasticity has evolved since John Gurdon transferred the nucleus of a completely differentiated cell into an enucleated Xenopus laevis egg, thereby generating embryos that developed into tadpoles. More recently, induced expression of transcription factors, oct4, sox2, klf4, and c-myc has evidenced the plasticity of the genome to change the expression program and cell phenotype by driving differentiated cells to the pluripotent state. Beyond these milestone achievements, research in artificial cell reprogramming has been focused on other molecules that are different than transcription factors. Among the candidate molecules, microRNAs (miRNAs) stand out due to their potential to control the levels of proteins that are involved in cellular processes such as self-renewal, proliferation, and differentiation. Here, we review the role of miRNAs in the maintenance and differentiation of mesenchymal stem cells, epimorphic regeneration, and somatic cell reprogramming to induced pluripotent stem cells.
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Affiliation(s)
- María Concepción Cruz-Santos
- 1 Molecular and Developmental Complexity Group, Unidad de Genómica Avanzada (U.G.A.-LANGEBIO) CINVESTAV , Irapuato, México
| | - Alejandro Aragón-Raygoza
- 1 Molecular and Developmental Complexity Group, Unidad de Genómica Avanzada (U.G.A.-LANGEBIO) CINVESTAV , Irapuato, México
| | - Annie Espinal-Centeno
- 1 Molecular and Developmental Complexity Group, Unidad de Genómica Avanzada (U.G.A.-LANGEBIO) CINVESTAV , Irapuato, México
| | - Mario Arteaga-Vázquez
- 2 Laboratory of Epigenetics and Developmental Biology, Institute for Biotechnology and Applied Ecology (INBIOTECA) , Universidad Veracruzana, Xalapa, México
| | - Andrés Cruz-Hernández
- 3 Facultad of Chemistry, Autonomous University of Querétaro, Santiago de Querétaro, México
| | - Laszlo Bako
- 4 Department of Plant Physiology, Umeå University , Umeå, Sweden
| | - Alfredo Cruz-Ramírez
- 1 Molecular and Developmental Complexity Group, Unidad de Genómica Avanzada (U.G.A.-LANGEBIO) CINVESTAV , Irapuato, México
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14
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Yao S. MicroRNA biogenesis and their functions in regulating stem cell potency and differentiation. Biol Proced Online 2016; 18:8. [PMID: 26966421 PMCID: PMC4785656 DOI: 10.1186/s12575-016-0037-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 02/22/2016] [Indexed: 01/07/2023] Open
Abstract
Stem cells are unspecialized/undifferentiated cells that exist in embryos and adult tissues or can be converted from somatic differentiated cells. Use of stem cells for tissue regeneration and tissue engineering has been a cornerstone of the regenerative medicine. Stem cells are also believed to exist in cancer tissues, namely cancer stem cells (CSCs). Growing evidence suggests that CSCs are the culprit of cancer dormancy, progression and recurrence, and thus have recently received great attention. MicroRNAs (miRNAs) are a group of short, non-coding RNAs that regulate expression of a wide range of genes at a post-transcriptional manner. They are emerging as key regulators of stem cell behaviors. This mini review summarizes the basic biogenesis and mode of actions of miRNAs, recent progress and discoveries of miRNAs in cellular reprogramming, stem cell differentiation and cellular communication, as well as miRNAs in CSCs. Some potential of miRNAs in future biomedical applications and research pertaining to stem cells are briefly discussed.
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Affiliation(s)
- Shaomian Yao
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803 USA
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15
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Abstract
During development, cells transition from a pluripotent to a differentiated state, generating all the different types of cells in the body. Development is generally considered an irreversible process, meaning that a differentiated cell is thought to be unable to return to the pluripotent state. However, it is now possible to reprogram mature cells to pluripotency. It is generally thought that reprogramming is accomplished by reversing the natural developmental differentiation process, suggesting that the two mechanisms are closely related. Therefore, a detailed study of cell reprogramming has the potential to shed light on unexplained developmental mechanisms and, conversely, a better understanding of developmental differentiation can help improve cell reprogramming. However, fundamental differences between reprogramming processes and multi-lineage specification during early embryonic development have also been uncovered. In addition, there are multiple routes by which differentiated cells can re-enter the pluripotent state. In this Review, we discuss the connections and disparities between differentiation and reprogramming, and assess the degree to which reprogramming can be considered as a simple reversal of development.
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Affiliation(s)
- Kazutoshi Takahashi
- Center for iPS Cell Research and Application, Kyoto University, Kyoto 606-8507, Japan Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
| | - Shinya Yamanaka
- Center for iPS Cell Research and Application, Kyoto University, Kyoto 606-8507, Japan Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
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16
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Abdelfattah AM, Park C, Choi MY. Update on non-canonical microRNAs. Biomol Concepts 2015; 5:275-87. [PMID: 25372759 DOI: 10.1515/bmc-2014-0012] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 07/07/2014] [Indexed: 12/14/2022] Open
Abstract
Non-canonical microRNAs are a recently-discovered subset of microRNAs. They structurally and functionally resemble canonical miRNAs, but were found to follow distinct maturation pathways, typically bypassing one or more steps of the classic canonical biogenesis pathway. Non-canonical miRNAs were found to have diverse origins, including introns, snoRNAs, endogenous shRNAs and tRNAs. Our knowledge about their functions remains relatively primitive; however, many interesting discoveries have taken place in the past few years. They have been found to take part in several cellular processes, such as immune response and stem cell proliferation. Adversely, their deregulation has pathologic effects on several different tissues, which strongly suggests an integral role for non-canonical miRNAs in disease pathogenesis. In this review, we discuss the recently-discovered functional characteristics of non-canonical miRNAs and illustrate their principal maturation pathways as well as debating their potential role in multiple cellular processes.
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17
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Moradi S, Asgari S, Baharvand H. Concise Review: Harmonies Played by MicroRNAs in Cell Fate Reprogramming. Stem Cells 2014; 32:3-15. [DOI: 10.1002/stem.1576] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 09/23/2013] [Accepted: 09/27/2013] [Indexed: 12/31/2022]
Affiliation(s)
- Sharif Moradi
- Department of Stem Cells and Developmental Biology at Cell Science Research Center; Royan Institute for Stem Cell Biology and Technology; Tehran Iran
- Department of Developmental Biology; University of Science and Culture; ACECR Tehran Iran
| | - Sassan Asgari
- Australian Infectious Disease Research Centre, School of Biological Sciences; The University of Queensland; St Lucia Queensland Australia
| | - Hossein Baharvand
- Department of Stem Cells and Developmental Biology at Cell Science Research Center; Royan Institute for Stem Cell Biology and Technology; Tehran Iran
- Department of Developmental Biology; University of Science and Culture; ACECR Tehran Iran
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18
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Greve TS, Judson RL, Blelloch R. microRNA control of mouse and human pluripotent stem cell behavior. Annu Rev Cell Dev Biol 2013; 29:213-239. [PMID: 23875649 DOI: 10.1146/annurev-cellbio-101512-122343] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the past decade, significant progress has been made in understanding both microRNA function and cellular pluripotency. Here we review the intersection of these two exciting fields. While microRNAs are not required for the establishment and maintenance of pluripotency in early development and cell culture, respectively, they are critically important in the regulation of the cell cycle structure of pluripotent stem cells as well as the silencing of the pluripotency program upon differentiation. Pluripotent cells, both in vivo and in vitro, dominantly express a single family of microRNAs, which can promote the reprogramming of a somatic cell back to a pluripotent state. Here, we review the known mechanisms by which these and other microRNAs regulate the different aspects of the pluripotent stem cell program in both mouse and human.
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Affiliation(s)
- Tobias S Greve
- Department of Urology and The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, Program in Biomedical Sciences, University of California, San Francisco, California, 94143
| | - Robert L Judson
- Department of Urology and The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, Program in Biomedical Sciences, University of California, San Francisco, California, 94143
| | - Robert Blelloch
- Department of Urology and The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, Program in Biomedical Sciences, University of California, San Francisco, California, 94143
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19
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Lüningschrör P, Hauser S, Kaltschmidt B, Kaltschmidt C. MicroRNAs in pluripotency, reprogramming and cell fate induction. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1894-903. [PMID: 23557785 DOI: 10.1016/j.bbamcr.2013.03.025] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 12/16/2022]
Abstract
Pluripotent stem cells display a unique expression pattern of microRNAs (miRNAs). These ~22 nucleotide non-coding RNAs have established a crucial role in controlling gene expression of pluripotent stem cells at the post-transcriptional level. Recent studies made important advances in identifying miRNA regulated processes like de novo DNA methylation, progression of the cell cycle and regulation of cell fate decision. miRNAs have also the ability to reprogram somatic cells to pluripotent stem cells and on the other hand, to induce differentiation of pluripotent stem cells into distinct somatic lineages. Previously it was published that miRNAs can direct reprogramming on its own. Here we provide evidence and critically discuss that the effect of miRNA depends on co-expression of the classical reprogramming factors. During transition between these different cell fates distinct miRNAs adjust the levels of specific transcriptional programs and confer robustness to differentiation processes. This results in a complex network between miRNAs and their targets. The fact that miRNAs itself can also be regulated by its targets establishes complex regulatory loops. Based on bioinformatical predictions, each miRNA theoretically has hundreds of target genes making it even more challenging to understand the complete network between miRNAs and their targets.
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20
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New advances of microRNAs in the pathogenesis of rheumatoid arthritis, with a focus on the crosstalk between DNA methylation and the microRNA machinery. Cell Signal 2013; 25:1118-25. [PMID: 23385088 DOI: 10.1016/j.cellsig.2013.01.024] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 01/25/2013] [Indexed: 12/28/2022]
Abstract
Rheumatoid arthritis (RA) is a symmetrical polyarticular disease of unknown aetiology that affects primarily the articular cartilage and bone. Characteristic features of RA pathogenesis are persistent inflammation, synovium hyperplasia and cartilage erosion accompanied by joint swelling and joint destruction. Several lines of evidence have showed a crucial role of activated fibroblast-like synoviocytes (FLS) in the pathogenesis of RA. MicroRNAs (miRNAs) are endogenous, single-stranded, non-coding RNAs with about 21 nucleotides in length and have been detected in a variety of sources, including tissues, serum, and other body fluids, such as saliva. In light of key roles of miRNAs in the regulation of gene expression, miRNAs influence a wide range of physiological and pathological processes. For example, miRNAs are evident in various malignant and nonmalignant diseases, and accumulating evidence also shows that miRNAs have important roles in the pathogenesis of RA. It has been demonstrated that miRNAs can be aberrantly expressed even in the different stages of RA progression, allowing miRNAs to help understand the pathogenesis of the disease, to act as important biomarkers, and to monitor the disease severity and the effects of drug treatment. In addition, miRNAs are emerging as potential targets for new therapeutic strategies of this kind of autoimmune disorders. The ultimate goal is the identification of miRNA targets that could be manipulated through specific therapies, aiming at activation or inhibition of specific miRNAs responsible for the RA development. In this review, the importance of miRNAs in the pathogenesis of RA is discussed systematically, with particular emphasis on the role of the crosstalk between DNA methylation and the microRNA machinery.
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Abstract
Cell fate decision is a critical step during physiological development when embryonic stem cells commit to either becoming adult stem cells or somatic cells. Recent advances in reprogramming demonstrate that a similar set of transcription factors (TFs), which are important for maintaining the pluripotent state of stem cells, can also reprogram somatic cells to induced pluripotent stem cells (iPSCs). In addition, trans-differentiation, which entails the use of different sets of defined factors, whereby one type of somatic cell can be directly converted into another and even to cell types from different germ layers has become a parallel widely used approach for switching cell fate. All these progresses have provided powerful tools to manipulate cells for basic science and therapeutic purposes. Besides protein-based factors, non-coding RNAs (ncRNAs), particularly microRNAs and long ncRNAs, are also involved in cell fate determination, including maintaining self-renewal of pluripotent stem cells and directing cell lineage. Targeting specific ncRNAs represents an alternative promising approach to optimize cell-based disease modeling and regenerative therapy. Here we focus on recent advances of ncRNAs in cell fate decision, including ncRNA-induced iPSCs and lineage conversion. We also discuss some underlying mechanisms and implications in molecular pathogenesis of human diseases.
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22
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Cardiac stem cell niche, MMP9, and culture and differentiation of embryonic stem cells. Methods Mol Biol 2013; 1035:153-63. [PMID: 23959989 DOI: 10.1007/978-1-62703-508-8_13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Embryonic stem cells (ESC) are totipotent, self-renewing, and clonogenic, having potential to differentiate into a wide variety of cell types. Due to regenerative capability, it has tremendous potential for treating myocardial infarction (death of myocardial tissue) and type 1 diabetes (death of pancreatic beta cells). Understanding the components regulating ESC differentiation is the key to unlock the regenerative potential of ESC-based therapies. Both the stiffness of extracellular matrix (ECM) and surrounding niche/microenvironment play pivotal roles in ESC differentiation. Matrix metalloproteinase-9 (MMP9) induces fibrosis that causes stiffness of the ECM and impairs differentiation of cardiac stem cells into cardiomyocytes. Here, we describe the method of ESC culture and differentiation, and the expression of MMP9 and its inhibitor, tissue inhibitor of metalloproteinase-4 (TIMP4) in differentiating ESC.
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23
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Kim BM, Choi MY. Non-canonical microRNAs miR-320 and miR-702 promote proliferation in Dgcr8-deficient embryonic stem cells. Biochem Biophys Res Commun 2012; 426:183-9. [PMID: 22925886 DOI: 10.1016/j.bbrc.2012.08.058] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 08/11/2012] [Indexed: 12/21/2022]
Abstract
MicroRNAs are known to contribute significantly to stem cell phenotype by post-transcriptionally regulating gene expression. Most of our knowledge of microRNAs comes from the study of canonical microRNAs that require two sequential cleavages by the Drosha/Dgcr8 heterodimer and Dicer to generate mature products. In contrast, non-canonical microRNAs bypass the cleavage by the Drosha/Dgcr8 heterodimer within the nucleus but still require cytoplasmic cleavage by Dicer. The function of non-canonical microRNAs in embryonic stem cells (ESCs) remains obscure. It has been hypothesized that non-canonical microRNAs have important roles in ESCs based upon the phenotypes of ESC lines that lack these specific classes of microRNAs; Dicer-deficient ESCs lacking both canonical and non-canonical microRNAs have much more severe proliferation defect than Dgcr8-deficient ESCs lacking only canonical microRNAs. Using these cell lines, we identified two non-canonical microRNAs, miR-320 and miR-702, that promote proliferation of Dgcr8-deficient ESCs by releasing them from G1 arrest. This is accomplished by targeting the 3'-untranslated regions of the cell cycle inhibitors p57 and p21 and thereby inhibiting their expression. This is the first report of the crucial role of non-canonical microRNAs in ESCs.
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Affiliation(s)
- Byeong-Moo Kim
- Department of Medicine/GI Unit, Massachusetts General Hospital, Boston, MA 02114, USA
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