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González J, Bosch-Presegué L, Marazuela-Duque A, Guitart-Solanes A, Espinosa-Alcantud M, Fernandez AF, Brown JP, Ausió J, Vazquez BN, Singh PB, Fraga MF, Vaquero A. A complex interplay between H2A.Z and HP1 isoforms regulates pericentric heterochromatin. Front Cell Dev Biol 2023; 11:1293122. [PMID: 38020886 PMCID: PMC10665487 DOI: 10.3389/fcell.2023.1293122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 10/27/2023] [Indexed: 12/01/2023] Open
Abstract
Pericentric heterochromatin (PCH) plays an essential role in the maintenance of genome integrity and alterations in PCH have been linked to cancer and aging. HP1 α, β, and γ, are hallmarks of constitutive heterochromatin that are thought to promote PCH structure through binding to heterochromatin-specific histone modifications and interaction with a wide range of factors. Among the less understood components of PCH is the histone H2A variant H2A.Z, whose role in the organization and maintenance of PCH is poorly defined. Here we show that there is a complex interplay between H2A.Z and HP1 isoforms in PCH. While the loss of HP1α results in the accumulation of H2A.Z.1 in PCH, which is associated with a significant decrease in its mobile fraction, H2A.Z.1 binds preferentially to HP1β in these regions. Of note, H2A.Z.1 downregulation results in increased heterochromatinization and instability of PCH, reflected by accumulation of the major epigenetic hallmarks of heterochromatin in these regions and increased frequency of chromosome aberrations related to centromeric/pericentromeric defects. Our studies support a role for H2A.Z in genome stability and unveil a key role of H2A.Z in the regulation of heterochromatin-specific epigenetic modifications through a complex interplay with the HP1 isoforms.
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Affiliation(s)
- Jessica González
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
| | - Laia Bosch-Presegué
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
- Tissue Repair and Regeneration Laboratory (TR2Lab), Institut de Recerca I Innovació en Ciències de La Vida i de La Salut a La Catalunya Central (IrisCC), Barcelona, Spain
| | - Anna Marazuela-Duque
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
| | - Anna Guitart-Solanes
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
| | - María Espinosa-Alcantud
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
| | - Agustín F. Fernandez
- Nanomaterials and Nanotechnology Research Center (CINN), Spanish National Research Council (CSIC), El Entrego, Spain
- Institute of Oncology of Asturias (IUOPA), University of Oviedo, Oviedo, Spain
- Health Research Institute of the Principality of Asturias (ISPA), Oviedo, Spain
- Spanish Biomedical Research Network in Rare Diseases (CIBERER), Madrid, Spain
| | - Jeremy P. Brown
- Department of Immunology and Inflammation, Imperial College London, Commonwealth Building, The Hammersmith Hospital, London, United Kingdom
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - Berta N. Vazquez
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
- Cytology and Histology Unit. Department of Cell Biology, Physiology, and Immunology, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
| | - Prim B. Singh
- Nazarbayev University School of Medicine, Astana, Kazakhstan
| | - Mario F. Fraga
- Nanomaterials and Nanotechnology Research Center (CINN), Spanish National Research Council (CSIC), El Entrego, Spain
- Institute of Oncology of Asturias (IUOPA), University of Oviedo, Oviedo, Spain
- Health Research Institute of the Principality of Asturias (ISPA), Oviedo, Spain
- Spanish Biomedical Research Network in Rare Diseases (CIBERER), Madrid, Spain
| | - Alejandro Vaquero
- Chromatin Biology Laboratory, Josep Carreras Leukaemia Research Institute (IJC), Barcelona, Spain
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Osipov YA, Posukh OV, Kalashnikova DA, Antoshina PA, Laktionov PP, Skrypnik PA, Belyakin SN, Singh PB. H3K9 and H4K20 methyltransferases are directly involved in the heterochromatinization of the paternal chromosomes in male Planococcus citri embryos. Chromosoma 2023; 132:317-328. [PMID: 37700063 DOI: 10.1007/s00412-023-00809-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/11/2023] [Accepted: 08/30/2023] [Indexed: 09/14/2023]
Abstract
Using a new method for bulk preparation of early stage embryos, we have investigated the role played by putative Planococcus citri H3K9 and H4K20 histone methyl transferases (HMTases) in regulating heterochromatinization of the imprinted paternal chromosomal set in male embryos. We found that H3K9 and H420 HMTases are required for heterochromatinization of the paternal chromosomes. We present evidence that both HMTases maintain the paternal "imprint" during the cleavage divisions when both parental chromosome sets are euchromatic. A testable model that accommodates our findings is proposed.
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Affiliation(s)
- Yakov A Osipov
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Olga V Posukh
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Darya A Kalashnikova
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Polina A Antoshina
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Petr P Laktionov
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Polina A Skrypnik
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation
- Institute of Molecular and Cellular Biology SD RAS, Lavrentyev Ave., 8/2, 630090, Novosibirsk, Russian Federation
| | - Stepan N Belyakin
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation.
| | - Prim B Singh
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation.
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, 010000, Nur-Sultan, Kazakhstan.
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3
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Abstract
'Age reprogramming' refers to the process by which the molecular and cellular pathways of a cell that are subject to age-related decline are rejuvenated without passage through an embryonic stage. This process differs from the rejuvenation observed in differentiated derivatives of induced pluripotent stem cells, which involves passage through an embryonic stage and loss of cellular identity. Accordingly, the study of age reprogramming can provide an understanding of how ageing can be reversed while retaining cellular identity and the specialised function(s) of a cell, which will be of benefit to regenerative medicine. Here, we highlight recent work that has provided a more nuanced understanding of age reprogramming and point to some open questions in the field that might be explored in the future.
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Affiliation(s)
- Prim B. Singh
- Department of Medicine, Nazarbayev University School of Medicine, 5/1 Kerei Zhanibek Khandar Street, Astana 010000, Republic of Kazakhstan,Author for correspondence ()
| | - Assem Zhakupova
- Department of Medicine, Nazarbayev University School of Medicine, 5/1 Kerei Zhanibek Khandar Street, Astana 010000, Republic of Kazakhstan
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Singh PB, Newman AG. HP1-Driven Micro-Phase Separation of Heterochromatin-Like Domains/Complexes. Epigenet Insights 2022; 15:25168657221109766. [PMID: 35813402 PMCID: PMC9260563 DOI: 10.1177/25168657221109766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 06/08/2022] [Indexed: 11/18/2022] Open
Affiliation(s)
- Prim B Singh
- Department of Medicine, Nazarbayev University School of Medicine, Nur-Sultan, Kazakhstan
| | - Andrew G Newman
- Institute of Cell and Neurobiology, Humboldt-Universität zu Berlin and Berlin Institute of Health, Berlin, Germany
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Le PT, Ha N, Tran NK, Newman AG, Esselen KM, Dalrymple JL, Schmelz EM, Bhandoola A, Xue HH, Singh PB, Thai TH. Targeting Cbx3/HP1γ Induces LEF-1 and IL-21R to Promote Tumor-Infiltrating CD8 T-Cell Persistence. Front Immunol 2021; 12:738958. [PMID: 34721405 PMCID: PMC8549513 DOI: 10.3389/fimmu.2021.738958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 09/08/2021] [Indexed: 11/13/2022] Open
Abstract
Immune checkpoint blockade (ICB) relieves CD8+ T-cell exhaustion in most mutated tumors, and TCF-1 is implicated in converting progenitor exhausted cells to functional effector cells. However, identifying mechanisms that can prevent functional senescence and potentiate CD8+ T-cell persistence for ICB non-responsive and resistant tumors remains elusive. We demonstrate that targeting Cbx3/HP1γ in CD8+ T cells augments transcription initiation and chromatin remodeling leading to increased transcriptional activity at Lef1 and Il21r. LEF-1 and IL-21R are necessary for Cbx3/HP1γ-deficient CD8+ effector T cells to persist and control ovarian cancer, melanoma, and neuroblastoma in preclinical models. The enhanced persistence of Cbx3/HP1γ-deficient CD8+ T cells facilitates remodeling of the tumor chemokine/receptor landscape ensuring their optimal invasion at the expense of CD4+ Tregs. Thus, CD8+ T cells heightened effector function consequent to Cbx3/HP1γ deficiency may be distinct from functional reactivation by ICB, implicating Cbx3/HP1γ as a viable cancer T-cell-based therapy target for ICB resistant, non-responsive solid tumors.
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Affiliation(s)
- Phuong T Le
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Ngoc Ha
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Ngan K Tran
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Andrew G Newman
- Institute of Cell and Neurobiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, Berlin, Germany
| | - Katharine M Esselen
- Division of Gynecologic Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - John L Dalrymple
- Division of Gynecologic Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Eva M Schmelz
- Department of Human Nutrition, Food, and Exercise, Virginia Tech, Blacksburg, VA, United States
| | - Avinash Bhandoola
- Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States
| | - Hai-Hui Xue
- Center for Discovery and Innovation, Hackensack University Medical Center, Nutley, NJ, United States
| | - Prim B Singh
- Nazarbayev University School of Medicine, Nur-Sultan, Kazakhstan
| | - To-Ha Thai
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States.,Cancer Research Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
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Abstract
The hallmarks of constitutive heterochromatin, HP1 and H3K9me2/3, assemble heterochromatin-like domains/complexes outside canonical constitutively heterochromatic territories where they regulate chromatin template-dependent processes. Domains are more than 100 kb in size; complexes less than 100 kb. They are present in the genomes of organisms ranging from fission yeast to human, with an expansion in size and number in mammals. Some of the likely functions of domains/complexes include silencing of the donor mating type region in fission yeast, preservation of DNA methylation at imprinted germline differentially methylated regions (gDMRs) and regulation of the phylotypic progression during vertebrate development. Far cis- and trans-contacts between micro-phase separated domains/complexes in mammalian nuclei contribute to the emergence of epigenetic compartmental domains (ECDs) detected in Hi-C maps. A thermodynamic description of micro-phase separation of heterochromatin-like domains/complexes may require a gestalt shift away from the monomer as the "unit of incompatibility" that determines the sign and magnitude of the Flory-Huggins parameter, χ. Instead, a more dynamic structure, the oligo-nucleosomal "clutch", consisting of between 2 and 10 nucleosomes is both the long sought-after secondary structure of chromatin and its unit of incompatibility. Based on this assumption we present a simple theoretical framework that enables an estimation of χ for domains/complexes flanked by euchromatin and thereby an indication of their tendency to phase separate. The degree of phase separation is specified by χN, where N is the number of "clutches" in a domain/complex. Our approach could provide an additional tool for understanding the biophysics of the 3D genome.
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Affiliation(s)
- Prim B. Singh
- Nazarbayev University School of Medicine, Nur-Sultan City 010000, Kazakhstan
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia
| | - Stepan N. Belyakin
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia
- Genomics laboratory, Institute of molecular and cellular biology SD RAS, Lavrentyev ave, 8/2, 630090 Novosibirsk, Russia; (S.N.B.); (P.P.L.)
| | - Petr P. Laktionov
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia
- Genomics laboratory, Institute of molecular and cellular biology SD RAS, Lavrentyev ave, 8/2, 630090 Novosibirsk, Russia; (S.N.B.); (P.P.L.)
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Singh PB, Newman AG. On the relations of phase separation and Hi-C maps to epigenetics. R Soc Open Sci 2020; 7:191976. [PMID: 32257349 PMCID: PMC7062049 DOI: 10.1098/rsos.191976] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 02/03/2020] [Indexed: 05/10/2023]
Abstract
The relationship between compartmentalization of the genome and epigenetics is long and hoary. In 1928, Heitz defined heterochromatin as the largest differentiated chromatin compartment in eukaryotic nuclei. Müller's discovery of position-effect variegation in 1930 went on to show that heterochromatin is a cytologically visible state of heritable (epigenetic) gene repression. Current insights into compartmentalization have come from a high-throughput top-down approach where contact frequency (Hi-C) maps revealed the presence of compartmental domains that segregate the genome into heterochromatin and euchromatin. It has been argued that the compartmentalization seen in Hi-C maps is owing to the physiochemical process of phase separation. Oddly, the insights provided by these experimental and conceptual advances have remained largely silent on how Hi-C maps and phase separation relate to epigenetics. Addressing this issue directly in mammals, we have made use of a bottom-up approach starting with the hallmarks of constitutive heterochromatin, heterochromatin protein 1 (HP1) and its binding partner the H3K9me2/3 determinant of the histone code. They are key epigenetic regulators in eukaryotes. Both hallmarks are also found outside mammalian constitutive heterochromatin as constituents of larger (0.1-5 Mb) heterochromatin-like domains and smaller (less than 100 kb) complexes. The well-documented ability of HP1 proteins to function as bridges between H3K9me2/3-marked nucleosomes contributes to polymer-polymer phase separation that packages epigenetically heritable chromatin states during interphase. Contacts mediated by HP1 'bridging' are likely to have been detected in Hi-C maps, as evidenced by the B4 heterochromatic subcompartment that emerges from contacts between large KRAB-ZNF heterochromatin-like domains. Further, mutational analyses have revealed a finer, innate, compartmentalization in Hi-C experiments that probably reflect contacts involving smaller domains/complexes. Proteins that bridge (modified) DNA and histones in nucleosomal fibres-where the HP1-H3K9me2/3 interaction represents the most evolutionarily conserved paradigm-could drive and generate the fundamental compartmentalization of the interphase nucleus. This has implications for the mechanism(s) that maintains cellular identity, be it a terminally differentiated fibroblast or a pluripotent embryonic stem cell.
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Affiliation(s)
- Prim B. Singh
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, Nur-Sultan Z05K4F4, Kazakhstan
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Street 2, Novosibirsk 630090, Russian Federation
| | - Andrew G. Newman
- Institute of Cell and Neurobiology, Charité—Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, Berlin, Germany
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Singh PB, Laktionov PP, Newman AG. Deconstructing age reprogramming. J Biosci 2019; 44:106. [PMID: 31502583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It has been proposed that age reprogramming enables old cells to be rejuvenated without passage through an embryonic stage (Singh and Zacouto in J. Biosci. 35 315-319, 2010). As such, age reprogramming stands apart from the induced pluripotent stem (iPS) and nuclear transfer-embryonic stem (NT-ES) cell therapies where histo-compatible cells are produced only after passage through an embryonic stage. It avoids many of the disadvantages associated with iPS and NT-ES cell therapies. Experimental evidence in support of age reprogramming is burgeoning. Here, we discuss possible new approaches to enhance age reprogramming, which will have considerable benefits for regenerative therapies.
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Affiliation(s)
- Prim B Singh
- Nazarbayev University School of Medicine, Z05K4F4 Astana, Kazakhstan
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9
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Abstract
Chromosomal imprinting requires an epigenetic system that "imprints" one of the two parental chromosomes such that it results in a heritable (cell-to-cell) change in behavior of the "imprinted" chromosome. Imprinting takes place when the parental genomes are separate, which occurs during gamete formation in the respective germ-lines and post-fertilization during the period when the parental pro-nuclei lie separately within the ooplasm of the zygote. In the mouse, chromosomal imprinting is regulated by germ-line specific DNA methylation. But the methylation machinery in the respective germ-lines does not discriminate between imprinted and non-imprinted regions. As a consequence, the mouse oocyte nucleus contains over a thousand oocyte-specific germ-line differentially methylated regions (gDMRs). Upon fertilization, the sperm provides a few hundred sperm-specific gDMRs of its own. Combined, there are around 1600 imprinted and non-imprinted gDMRs in the pro-nuclei of the newly fertilized zygote. It is a remarkable fact that beginning in the maternal ooplasm, there are mechanisms that manage to preserve DNA methylation at ~ 26 known imprinted gDMRs in the face of the ongoing genome-wide DNA de-methylation that characterizes pre-implantation development. Specificity is achieved through the binding of KRAB-zinc finger proteins to their cognate recognition sequences within the gDMRs of imprinted genes. This in turn nucleates the assembly of localized heterochromatin-like complexes that preserve methylation at imprinted gDMRs through recruitment of the maintenance methyl transferase Dnmt1. These studies have shown that a germ-line imprint may cause parent-of-origin-specific behavior only if "licensed" by mechanisms that operate post-fertilization. Study of the germ-line and post-fertilization contributions to the imprinting of chromosomes in classical insect systems (Coccidae and Sciaridae) show that the ooplasm is the likely site where imprinting takes place. By comparing molecular and genetic studies across these three species, we suggest that mechanisms which operate post-fertilization play a key role in chromosomal imprinting phenomena in animals and conserved components of heterochromatin are shared by these mechanisms.
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Affiliation(s)
- Prim B Singh
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, Astana, Z05K4F4, Kazakhstan.
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov str. 2, Novosibirsk, 630090, Russian Federation.
| | - Victor V Shloma
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov str. 2, Novosibirsk, 630090, Russian Federation
- Genomics Laboratory, Institute of Molecular and Cellular Biology SD RAS, Lavrentyev ave, 8/2, Novosibirsk, 630090, Russian Federation
| | - Stepan N Belyakin
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov str. 2, Novosibirsk, 630090, Russian Federation
- Genomics Laboratory, Institute of Molecular and Cellular Biology SD RAS, Lavrentyev ave, 8/2, Novosibirsk, 630090, Russian Federation
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10
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Abstract
Age reprogramming represents a novel method for generating patient-specific tissues for transplantation. It bypasses the de-differentiation/redifferentiation cycle that is characteristic of the induced pluripotent stem (iPS) and nuclear transfer-embryonic stem (NT-ES) cell technologies that drive current interest in regenerative medicine. Despite the obvious potential of iPS and NT-ES cell-based therapies, there are several problems that must be overcome before these therapies are safe and routine. As an alternative, age reprogramming aims to rejuvenate the specialized functions of an old cell without de-differentiation; age reprogramming does not require developmental reprogramming through an embryonic stage, unlike the iPS and NT-ES cell-based therapies. Tests of age reprogramming have largely focused on one aspect, the epigenome. Epigenetic rejuvenation has been achieved in vitro in the absence of de-differentiation using iPS cell reprogramming factors. Studies on the dynamics of epigenetic age (eAge) reprogramming have demonstrated that the separation of eAge from developmental reprogramming can be explained largely by their different kinetics. Age reprogramming has also been achieved in vivo and shown to increase lifespan in a premature ageing mouse model. We conclude that age and developmental reprogramming can be disentangled and regulated independently in vitro and in vivo.
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Affiliation(s)
- Prim B Singh
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, Astana, Kazakhstan, Z05K4F4. .,Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Str. 2, Novosibirsk, 630090, Russian Federation. .,Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Cell and Neurobiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
| | - Andrew G Newman
- Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Cell and Neurobiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
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11
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Singh J, Shakya S, Shrestha B, Subedi B, Singh PB. Awake Fiberoptic Intubation in Cervical Spine Injury: A Comparison between Atomized Local Anesthesia versus Airway Nerve Blocks. Kathmandu Univ Med J (KUMJ) 2018; 16:323-327. [PMID: 31729347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Background In cooperative patients with cervical spine injury, awake fiberoptic intubation is an excellent option for elective and semi urgent situations. It allows documentation of neurologic examination before and after intubation and surgical positioning. We have compared anesthesia of airway by nerve block and the local anesthesia atomizer undergoing awake fiberoptic intubation in cervical spine injury patients, in terms of the intubation time and discomfort. Objective To compare the intubation time and discomfort in patient with cervical spine injury with anticipated difficult airway potential to aggravate pre-existing injury undergoing awake fiberoptic intubation, based on cough and gag scores, between anesthesia of airway by (transtracheal and bilateral superior laryngeal) nerve block with local anesthetic agent and the local anesthesia atomizer. Method After institutional ethical approval and having informed written consent, 30 patients scheduled for elective surgery who require awake fiberoptic intubation, were included in the study. Patients were allotted by computer-generated random series into two groups; Group N received nerve block (transtracheal and bilateral recurrent laryngeal nerve block) and Group A received atomized lignocaine. Result The time taken for awake fiberoptic intubation was significantly lower in nerve blocks group as compared with the atomizer group [Group N: 90.2±11.7secs and Group A: 210.4±10.6 secs (p=0.041)]. Atomizer group had an increased coughing and gagging episodes than nerve block group [Group N: one patient, Group A: 11 patients (p=0.006)]. Ease of intubation and patient comfort were significantly better in nerve block group. Demographic and hemodynamic parameters were comparable in the two groups. Conclusion The nerve blocks (bilateral superior laryngeal and transtracheal recurrent laryngeal) provides adequate airway anesthesia, lesser patient discomfort, and faster intubation to aid in awake fiberoptic intubation in patients with anticipated difficult airway as compared to topical anesthesia using atomizer.
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Affiliation(s)
- J Singh
- Department of Anesthesia, Kathmandu University School of Medical Sciences, Dhulikhel, Kavre, Nepal
| | - S Shakya
- Department of Anesthesia, Kathmandu University School of Medical Sciences, Dhulikhel, Kavre, Nepal
| | - B Shrestha
- Department of Anesthesia, Kathmandu University School of Medical Sciences, Dhulikhel, Kavre, Nepal
| | - B Subedi
- Department of Anesthesia, Kathmandu University School of Medical Sciences, Dhulikhel, Kavre, Nepal
| | - P B Singh
- Department of Anesthesia, Kathmandu University School of Medical Sciences, Dhulikhel, Kavre, Nepal
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12
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Singh PB, Belyakin SN. L Chromosome Behaviour and Chromosomal Imprinting in Sciara Coprophila. Genes (Basel) 2018; 9:genes9090440. [PMID: 30177635 PMCID: PMC6162386 DOI: 10.3390/genes9090440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 08/29/2018] [Accepted: 08/29/2018] [Indexed: 12/31/2022] Open
Abstract
The retention of supernumerary chromosomes in the germ-line of Sciara coprophila is part of a highly-intricate pattern of chromosome behaviours that have fascinated cytogeneticists for over 80 years. Germ-line limited (termed L or "limited") chromosomes are cytologically heterochromatic and late-replicating, with more recent studies confirming they possess epigenetic hallmarks characteristic of constitutive heterochromatin. Little is known about their genetic constitution although they have been found to undergo cycles of condensation and de-condensation at different stages of development. Unlike most supernumeraries, the L chromosomes in S. coprophila are thought to be indispensable, although in two closely related species Sciara ocellaris and Sciara reynoldsi the L chromosomes, have been lost during evolution. Here, we review what we know about L chromosomes in Sciara coprophila. We end by discussing how study of the L chromosome condensation cycle has provided insight into the site and timing of both the erasure of parental "imprints" and also the placement of a putative "imprint" that might be carried by the sperm into the egg.
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Affiliation(s)
- Prim B Singh
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, Astana Z05K4F4, Kazakhstan.
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov str. 2, Novosibirsk 630090, Russia.
| | - Stepan N Belyakin
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov str. 2, Novosibirsk 630090, Russia.
- Genomics laboratory, Institute of Molecular and Cellular Biology SB RAS, Lavrentyev ave, 8/2, Novosibirsk 630090, Russia.
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Oyama K, El-Nachef D, Fang C, Kajimoto H, Brown JP, Singh PB, MacLellan WR. Deletion of HP1γ in cardiac myocytes affects H4K20me3 levels but does not impact cardiac growth. Epigenetics Chromatin 2018; 11:18. [PMID: 29665845 PMCID: PMC5905015 DOI: 10.1186/s13072-018-0187-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 04/01/2018] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Heterochromatin, which is formed when tri-methyl lysine 9 of histone H3 (H3K9me3) is bound by heterochromatin 1 proteins (HP1s), plays an important role in differentiation and senescence by silencing cell cycle genes. Cardiac myocytes (CMs) accumulate heterochromatin during differentiation and demethylation of H3K9me3 inhibits cell cycle gene silencing and cell cycle exit in CMs; however, it is unclear if this process is mediated by HP1s. In this study, we created a conditional CM-specific HP1 gamma (HP1γ) knockout (KO) mouse model and tested whether HP1γ is required for cell cycle gene silencing and cardiac growth. RESULTS HP1γ KO mice were generated by crossing HP1γ floxed mice (fl) with mice expressing Cre recombinase driven by the Nkx2.5 (cardiac progenitor gene) promoter (Cre). We confirmed that deletion of critical exons of HP1γ led to undetectable levels of HP1γ protein in HP1γ KO (Cre;fl/fl) CMs. Analysis of cardiac size and function by echo revealed no significant differences between HP1γ KO and control (WT, Cre, fl/fl) mice. No significant difference in expression of cell cycle genes or cardiac-specific genes was observed. Global transcriptome analysis demonstrated a very moderate effect of HP1γ deletion on global gene expression, with only 51 genes differentially expressed in HP1γ KO CMs. We found that HP1β protein, but not HP1α, was significantly upregulated and that subnuclear localization of HP1β to perinuclear heterochromatin was increased in HP1γ KO CMs. Although HP1γ KO had no effect on H3K9me3 levels, we found a significant reduction in another major heterochromatin mark, tri-methylated lysine 20 of histone H4 (H4K20me3). CONCLUSIONS These data indicate that HP1γ is dispensable for cell cycle exit and normal cardiac growth but has a significant role in maintaining H4K20me3 and regulating a limited number of genes in CMs.
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Affiliation(s)
- Kyohei Oyama
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Biology and Institute for Stem Cell and Regenerative Medicine, University of Washington, 1959 NE Pacific St, Box 356422, Seattle, WA, 98195-6422, USA
| | - Danny El-Nachef
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Biology and Institute for Stem Cell and Regenerative Medicine, University of Washington, 1959 NE Pacific St, Box 356422, Seattle, WA, 98195-6422, USA
| | - Chen Fang
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Biology and Institute for Stem Cell and Regenerative Medicine, University of Washington, 1959 NE Pacific St, Box 356422, Seattle, WA, 98195-6422, USA
| | - Hidemi Kajimoto
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Biology and Institute for Stem Cell and Regenerative Medicine, University of Washington, 1959 NE Pacific St, Box 356422, Seattle, WA, 98195-6422, USA
| | - Jeremy P Brown
- Fächerverbund Anatomie, Institut für Zell-und Neurobiologie, Charite-Universitätsmedizin, 10117, Berlin, Germany
| | - Prim B Singh
- Fächerverbund Anatomie, Institut für Zell-und Neurobiologie, Charite-Universitätsmedizin, 10117, Berlin, Germany.,Department of Biomedical Sciences, Nazarbayev University School of Medicine, Astana, Kazakhstan, 010000.,Department of Natural Sciences, Laboratory of epigenetics, Novosibirsk State University, Pirogova str. 1, Novosibirsk, 630090, Russian Federation
| | - W Robb MacLellan
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Biology and Institute for Stem Cell and Regenerative Medicine, University of Washington, 1959 NE Pacific St, Box 356422, Seattle, WA, 98195-6422, USA.
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14
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Affiliation(s)
- Andrew G Newman
- Institute for Cell and Neurobiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Paraskevi Bessa
- Institute for Cell and Neurobiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Victor Tarabykin
- Institute for Cell and Neurobiology, Charité Universitätsmedizin Berlin, Berlin, Germany.,Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
| | - Prim B Singh
- Institute for Cell and Neurobiology, Charité Universitätsmedizin Berlin, Berlin, Germany.,Department of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, UK
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15
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Raurell-Vila H, Bosch-Presegue L, Gonzalez J, Kane-Goldsmith N, Casal C, Brown JP, Marazuela-Duque A, Singh PB, Serrano L, Vaquero A. An HP1 isoform-specific feedback mechanism regulates Suv39h1 activity under stress conditions. Epigenetics 2017; 12:166-175. [PMID: 28059589 DOI: 10.1080/15592294.2016.1278096] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
The presence of H3K9me3 and heterochromatin protein 1 (HP1) are hallmarks of heterochromatin conserved in eukaryotes. The spreading and maintenance of H3K9me3 is effected by the functional interplay between the H3K9me3-specific histone methyltransferase Suv39h1 and HP1. This interplay is complex in mammals because the three HP1 isoforms, HP1α, β, and γ, are thought to play a redundant role in Suv39h1-dependent deposition of H3K9me3 in pericentric heterochromatin (PCH). Here, we demonstrate that despite this redundancy, HP1α and, to a lesser extent, HP1γ have a closer functional link to Suv39h1, compared to HP1β. HP1α and γ preferentially interact in vivo with Suv39h1, regulate its dynamics in heterochromatin, and increase Suv39h1 protein stability through an inhibition of MDM2-dependent Suv39h1-K87 polyubiquitination. The reverse is also observed, where Suv39h1 increases HP1α stability compared HP1β and γ. The interplay between Suv39h1 and HP1 isoforms appears to be relevant under genotoxic stress. Specifically, loss of HP1α and γ isoforms inhibits the upregulation of Suv39h1 and H3K9me3 that is observed under stress conditions. Reciprocally, Suv39h1 deficiency abrogates stress-dependent upregulation of HP1α and γ, and enhances HP1β levels. Our work defines a specific role for HP1 isoforms in regulating Suv39h1 function under stress via a feedback mechanism that likely regulates heterochromatin formation.
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Affiliation(s)
- Helena Raurell-Vila
- a Chromatin Biology Laboratory, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain
| | - Laia Bosch-Presegue
- a Chromatin Biology Laboratory, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain.,b Tissue Repair and Regeneration Group , Department of Systems Biology , Universitat de Vic, Universitat Central de Catalunya , Vic , Spain
| | - Jessica Gonzalez
- a Chromatin Biology Laboratory, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain
| | - Noriko Kane-Goldsmith
- c Department of Genetics , Human Genetics Institute, Rutgers University , Piscataway , NJ , USA
| | - Carmen Casal
- d Microcopy Unit, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain
| | - Jeremy P Brown
- e Fächerverbund Anatomie, Institut für Zell- und Neurobiologie, Charite - Universitätsmedizin , Berlin , Germany
| | - Anna Marazuela-Duque
- a Chromatin Biology Laboratory, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain
| | - Prim B Singh
- e Fächerverbund Anatomie, Institut für Zell- und Neurobiologie, Charite - Universitätsmedizin , Berlin , Germany.,f Natural Sciences and Psychology, John Moores University , Liverpool , UK
| | - Lourdes Serrano
- c Department of Genetics , Human Genetics Institute, Rutgers University , Piscataway , NJ , USA
| | - Alejandro Vaquero
- a Chromatin Biology Laboratory, Cancer Epigenetics and Biology Program (PEBC), Institut d'Investigació Biomèdica de Bellvitge (IDIBELL) , L'Hospitalet de Llobregat, Barcelona , Spain
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16
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Muramatsu D, Singh PB, Kimura H, Tachibana M, Shinkai Y. Pericentric heterochromatin generated by HP1 protein interaction-defective histone methyltransferase Suv39h1. J Biol Chem 2016; 291:14393. [DOI: 10.1074/jbc.a113.470724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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17
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Valerio M, Anele C, Bott SRJ, Charman SC, van der Meulen J, El-Mahallawi H, Emara AM, Freeman A, Jameson C, Hindley RG, Montgomery BSI, Singh PB, Ahmed HU, Emberton M. The Prevalence of Clinically Significant Prostate Cancer According to Commonly Used Histological Thresholds in Men Undergoing Template Prostate Mapping Biopsies. J Urol 2015; 195:1403-1408. [PMID: 26626221 DOI: 10.1016/j.juro.2015.11.047] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2015] [Indexed: 12/14/2022]
Abstract
PURPOSE Transrectal prostate biopsies are inaccurate and, thus, the prevalence of clinically significant prostate cancer in men undergoing biopsy is unknown. We determined the ability of different histological thresholds to denote clinically significant cancer in men undergoing a more accurate biopsy, that of transperineal template prostate mapping. MATERIALS AND METHODS In this multicenter, cross-sectional cohort of men who underwent template prostate mapping biopsies between May 2006 and January 2012, 4 different thresholds of significance combining tumor grade and burden were used to measure the consequent variation with respect to the prevalence of clinically significant disease. RESULTS Of 1,203 men 17% (199) had no previous biopsy, 38% (455) had a prior negative transrectal ultrasound biopsy, 24% (289) were on active surveillance and 21% (260) were seeking risk stratification. Mean patient age was 63.5 years (SD 7.6) and median prostate specific antigen was 7.4 ng/ml (IQR 5.3-10.5). Overall 35% of the patients (424) had no cancer detected. The prevalence of clinically significant cancer varied between 14% and 83% according to the histological threshold used, in particular between 30% and 51% among men who had no previous biopsy, between 14% and 27% among men who had a prior negative biopsy, between 36% and 74% among men on active surveillance, and between 47% and 83% among men seeking risk stratification. CONCLUSIONS According to template prostate mapping biopsy between 1 in 2 and 1 in 3 men have prostate cancer that is histologically defined as clinically significant. This suggests that the commonly used thresholds may be set too low.
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Affiliation(s)
- M Valerio
- Division of Surgery and Interventional Science, University College London, London, United Kingdom; Department of Urology, University College Hospitals NHS Foundation Trust, London, United Kingdom; Department of Urology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
| | - C Anele
- Division of Surgery and Interventional Science, University College London, London, United Kingdom; Department of Urology, University College Hospitals NHS Foundation Trust, London, United Kingdom
| | - S R J Bott
- Department of Urology, Frimley Park Hospital NHS Foundation Trust, Frimley, United Kingdom
| | - S C Charman
- Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - J van der Meulen
- Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - H El-Mahallawi
- Department of Histopathology, Basingstoke and North Hampshire NHS Foundation Trust, Basingstoke, Hampshire, United Kingdom
| | - A M Emara
- Department of Urology, Basingstoke and North Hampshire NHS Foundation Trust, Basingstoke, Hampshire, United Kingdom; Department of Urology, Ain Shams University, Cairo, Egypt
| | - A Freeman
- Department of Histopathology, University College Hospital London, London, United Kingdom
| | - C Jameson
- Department of Histopathology, University College Hospital London, London, United Kingdom
| | - R G Hindley
- Department of Urology, Basingstoke and North Hampshire NHS Foundation Trust, Basingstoke, Hampshire, United Kingdom
| | - B S I Montgomery
- Department of Urology, Frimley Park Hospital NHS Foundation Trust, Frimley, United Kingdom
| | - P B Singh
- Department of Urology, Royal Free London NHS Foundation Trust, London, United Kingdom
| | - H U Ahmed
- Division of Surgery and Interventional Science, University College London, London, United Kingdom; Department of Urology, University College Hospitals NHS Foundation Trust, London, United Kingdom
| | - M Emberton
- Division of Surgery and Interventional Science, University College London, London, United Kingdom; Department of Urology, University College Hospitals NHS Foundation Trust, London, United Kingdom
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18
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Cardinale A, Filesi I, Singh PB, Biocca S. Intrabody-mediated diverting of HP1β to the cytoplasm induces co-aggregation of H3-H4 histones and lamin-B receptor. Exp Cell Res 2015; 338:70-81. [PMID: 26364738 DOI: 10.1016/j.yexcr.2015.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 09/07/2015] [Accepted: 09/08/2015] [Indexed: 12/12/2022]
Abstract
Diverting a protein from its intracellular location is a unique property of intrabodies. To interfere with the intracellular traffic of heterochromatin protein 1β (HP1β) in living cells, we have generated a cytoplasmic targeted anti-HP1β intrabody, specifically directed against the C-terminal portion of the molecule. HP1β is a conserved component of mouse and human constitutive heterochromatin involved in diverse nuclear functions including gene silencing, DNA repair and nuclear membrane assembly. We found that the anti-HP1β intrabody sequesters HP1β into cytoplasmic aggregates, inhibiting its traffic to the nucleus. Lamin B receptor (LBR) and a subset of core histones (H3/H4) are also specifically co-sequestered in the cytoplasm of anti-HP1β intrabody-expressing cells. Methylated histone H3 at K9 (Me9H3), a marker of constitutive heterochromatin, is not affected by the anti-HP1β intrabody expression. Hyper-acetylating conditions completely dislodge H3 from HP1β:LBR containing aggregates. The expression of anti-HP1β scFv fragments induces apoptosis, associated with an alteration of nuclear morphology. Both these phenotypes are specifically rescued either by overexpression of recombinant full length HP1β or by HP1β mutant containing the chromoshadow domain, but not by recombinant LBR protein. The HP1β-chromodomain mutant, on the other hand, does not rescue the phenotypes, but does compete with LBR for binding to HP1β. These findings provide new insights into the mode of action of cytoplasmic-targeted intrabodies and the interaction between HP1β and its binding partners involved in peripheral heterochromatin organisation.
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Affiliation(s)
- Alessio Cardinale
- Laboratory of Molecular and Cellular Neurobiology, IRCCS San Raffaele Pisana, Via di Val Cannuta 247, 00166 Rome, Italy
| | - Ilaria Filesi
- Department of Systems Medicine, University of Roma Tor Vergata, Via Montpellier 1, 00133 Roma, Italy
| | - Prim B Singh
- Department of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, United Kingdom
| | - Silvia Biocca
- Department of Systems Medicine, University of Roma Tor Vergata, Via Montpellier 1, 00133 Roma, Italy.
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Aydin E, Kloos DP, Gay E, Jonker W, Hu L, Bullwinkel J, Brown JP, Manukyan M, Giera M, Singh PB, Fundele R. A hypomorphic Cbx3 allele causes prenatal growth restriction and perinatal energy homeostasis defects. J Biosci 2015; 40:325-38. [DOI: 10.1007/s12038-015-9520-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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20
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Manukyan M, Singh PB. Epigenome rejuvenation: HP1β mobility as a measure of pluripotent and senescent chromatin ground states. Sci Rep 2014; 4:4789. [PMID: 24763337 PMCID: PMC3999444 DOI: 10.1038/srep04789] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 03/17/2014] [Indexed: 01/08/2023] Open
Abstract
We measured the dynamics of an essential epigenetic modifier, HP1β, in human cells at different stages of differentiation using Fluorescence Recovery After Photobleaching (FRAP). We found that HP1β mobility is similar in human embryonic stem cells (hES) and iPS cells where it is more mobile compared to fibroblasts; HP1β is less mobile in senescent fibroblasts than in young (dividing) fibroblasts. Introduction of "reprogramming factors", Oct4, Sox2, Klf4, cMyc and Lin28, into senescent fibroblasts and measuring the changes in HP1β mobility as reprogramming proceeds shows that the mobility of HP1β in senescent cells increases and by day 9 is the same as that found in young fibroblasts. Thus the dynamics of a key epigenetic modifier can be rejuvenated without de-differentiation through an embryonic stage. Future work will test whether other aspects of cellular physiology that age can be so rejuvenated without de-differentiation.
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Affiliation(s)
- Maria Manukyan
- Albert-Ludwigs-Universität Freiburg, BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 18, 79104 Freiburg, Germany
| | - Prim B. Singh
- Fächerverbund Anatomie, Institut für Zell- und Neurobiologie, Charite – Universitätsmedizin, 10117 Berlin, Germany
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21
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Muramatsu D, Singh PB, Kimura H, Tachibana M, Shinkai Y. Pericentric heterochromatin generated by HP1 protein interaction-defective histone methyltransferase Suv39h1. J Biol Chem 2013; 288:25285-25296. [PMID: 23836914 PMCID: PMC3757193 DOI: 10.1074/jbc.m113.470724] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 06/23/2013] [Indexed: 02/02/2023] Open
Abstract
Pericentric regions form epigenetically organized silent heterochromatin structures that accumulate histone H3 lysine 9 trimethylation (H3K9me3) and HP1. At pericentric regions, Suv39h is the major enzyme that generates H3K9me3. Suv39h also interacts directly with HP1, a methylated H3K9-binding protein. However, it is not well characterized how HP1 interaction is important for Suv39h accumulation and Suv39h-mediated H3K9me3 formation at the pericentromere. To address this, we introduced the HP1 binding-defective N-terminally truncated mouse Suv39h1 (ΔN) into Suv39h-deficient embryonic stem cells. Interestingly, pericentric accumulation of ΔN and ΔN-mediated H3K9me3 was observed to recover, but HP1 accumulation was only marginally restored. ΔN also rescued DNA methyltransferase Dnmt3a and -3b accumulation and DNA methylation of the pericentromere. In contrast, other pericentric heterochromatin features, such as ATRX protein association and H4K20me3, were not recovered. Finally, derepressed major satellite repeats were partially silenced by ΔN expression. These findings clearly showed that the Suv39h-HP1 binding is dispensable for pericentric H3K9me3 and DNA methylation, but this interaction and HP1 recruitment/accumulation seem to be crucial for complete formation of heterochromatin.
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Affiliation(s)
- Daisuke Muramatsu
- From the Graduate School of Biostudies, Kyoto University, 53 Shogoin, Kawara-cho, Sakyo-ku, Kyoto 606-8507, Japan,; the Cellular Memory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Prim B Singh
- the Fächereverband Anatomie, Institut für Zell and Neurobiologie, Charite-Universitätmedizin, 10117 Berlin, Germany
| | - Hiroshi Kimura
- the Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Makoto Tachibana
- From the Graduate School of Biostudies, Kyoto University, 53 Shogoin, Kawara-cho, Sakyo-ku, Kyoto 606-8507, Japan,; the Institute for Virus Research, Kyoto University, 53 Shogoin, Kawara-cho, Sakyo-ku, Kyoto 606-8507, Japan, and
| | - Yoichi Shinkai
- the Cellular Memory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan,; CREST (Core Research for Evolutional Science and Technology), Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
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22
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Maksakova IA, Thompson PJ, Goyal P, Jones SJ, Singh PB, Karimi MM, Lorincz MC. Distinct roles of KAP1, HP1 and G9a/GLP in silencing of the two-cell-specific retrotransposon MERVL in mouse ES cells. Epigenetics Chromatin 2013; 6:15. [PMID: 23735015 PMCID: PMC3682905 DOI: 10.1186/1756-8935-6-15] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 05/08/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In mouse embryonic stem cells (mESCs), transcriptional silencing of numerous class I and II endogenous retroviruses (ERVs), including IAP, ETn and MMERVK10C, is dependent upon the H3K9 methyltransferase (KMTase) SETDB1/ESET and its binding partner KAP1/TRIM28. In contrast, the H3K9 KMTases G9a and GLP and HP1 proteins are dispensable for this process. Intriguingly, MERVL retroelements are actively transcribed exclusively in the two-cell (2C) embryo, but the molecular basis of silencing of these class III ERVs at later developmental stages has not been systematically addressed. RESULTS Here, we characterized the roles of these chromatin factors in MERVL silencing in mESCs. While MMERVK10C and IAP ERVs are bound by SETDB1 and KAP1 and are induced following their deletion, MERVL ERVs show relatively low levels of SETDB1 and KAP1 binding and are upregulated exclusively following KAP1 depletion, indicating that KAP1 influences MERVL expression independent of SETDB1. In contrast to class I and class II ERVs, MERVL and MERVL LTR-driven genic transcripts are also upregulated following depletion of G9a or GLP, and G9a binds directly to these ERVs. Consistent with a direct role for H3K9me2 in MERVL repression, these elements are highly enriched for G9a-dependent H3K9me2, and catalytically active G9a is required for silencing of MERVL LTR-driven transcripts. MERVL is also derepressed in HP1α and HP1β KO ESCs. However, like KAP1, HP1α and HP1β are only modestly enriched at MERVL relative to IAP LTRs. Intriguingly, as recently shown for KAP1, RYBP, LSD1 and G9a-deficient mESCs, many genes normally expressed in the 2C embryo are also induced in HP1 KO mESCs, revealing that aberrant expression of a subset of 2C-specific genes is a common feature in each of these KO lines. CONCLUSIONS Our results indicate that G9a and GLP, which are not required for silencing of class I and II ERVs, are recruited to MERVL elements and play a direct role in silencing of these class III ERVs, dependent upon G9a catalytic activity. In contrast, induction of MERVL expression in KAP1, HP1α and HP1β KO ESCs may occur predominantly as a consequence of indirect effects, in association with activation of a subset of 2C-specific genes.
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Affiliation(s)
- Irina A Maksakova
- Department of Medical Genetics, Life Sciences Institute, 2350 Health Sciences Mall, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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Brown JP, Bullwinkel J, Baron-Lühr B, Billur M, Schneider P, Winking H, Singh PB. Correction: HP1gamma function is required for male germ cell survival and spermatogenesis. Epigenetics Chromatin 2012; 5:18. [PMID: 23171735 PMCID: PMC3562198 DOI: 10.1186/1756-8935-5-18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 11/16/2012] [Indexed: 11/10/2022] Open
Affiliation(s)
- Jeremy P Brown
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, D-23845, Borstel, Germany.
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Abstract
Induced pluripotent stem (iPS) cells have provided a rational means of obtaining histo-compatible tissues for ‘patient-specific’ regenerative therapies (Hanna et al. 2010; Yamanaka & Blau 2010). Despite the obvious potential of iPS cell-based therapies, there are certain problems that must be overcome before these therapies can become safe and routine (Ohi et al. 2011; Pera 2011). As an alternative, we have recently explored the possibility of using ‘epigenetic rejuvenation’, where the specialized functions of an old cell are rejuvenated in the absence of any change in its differentiated state (Singh & Zacouto 2010). The mechanism(s) that underpin ‘epigenetic rejuvenation’ are unknown and here we discuss model systems, using key epigenetic modifiers, which might shed light on the processes involved. Epigenetic rejuvenation has advantages over iPS cell techniques that are currently being pursued. First, the genetic and epigenetic abnormalities that arise through the cycle of dedifferentiation of somatic cells to iPS cells followed by redifferentiation of iPS cells into the desired cell type are avoided (Gore et al. 2011; Hussein et al. 2011; Pera 2011): epigenetic rejuvenation does not require passage through the de-/redifferentiation cycle. Second, because the aim of epigenetic rejuvenation is to ensure that the differentiated cell type retains its specialized function it makes redundant the question of transcriptional memory that is inimical to iPS cell-based therapies (Ohi et al. 2011). Third, to produce unrelated cell types using the iPS technology takes a long time, around three weeks, whereas epigenetic rejuvenation of old cells will take only a matter of days. Epigenetic rejuvenation provides the most safe, rapid and cheap route to successful regenerative medicine.
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Affiliation(s)
- Maria Manukyan
- Albert-Ludwigs-Universität Freiburg, BIOSS Centre for Biological Signalling Studies, Zentrum für Biosystemanalyse - ZBSA, Habsburgerstrasse 49, 79104 Freiburg, Germany
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Maksakova IA, Goyal P, Bullwinkel J, Brown JP, Bilenky M, Mager DL, Singh PB, Lorincz MC. H3K9me3-binding proteins are dispensable for SETDB1/H3K9me3-dependent retroviral silencing. Epigenetics Chromatin 2011; 4:12. [PMID: 21774827 PMCID: PMC3169442 DOI: 10.1186/1756-8935-4-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 07/20/2011] [Indexed: 02/01/2023] Open
Abstract
Background Endogenous retroviruses (ERVs) are parasitic sequences whose derepression is associated with cancer and genomic instability. Many ERV families are silenced in mouse embryonic stem cells (mESCs) via SETDB1-deposited trimethylated lysine 9 of histone 3 (H3K9me3), but the mechanism of H3K9me3-dependent repression remains unknown. Multiple proteins, including members of the heterochromatin protein 1 (HP1) family, bind H3K9me2/3 and are involved in transcriptional silencing in model organisms. In this work, we address the role of such H3K9me2/3 "readers" in the silencing of ERVs in mESCs. Results We demonstrate that despite the reported function of HP1 proteins in H3K9me-dependent gene repression and the critical role of H3K9me3 in transcriptional silencing of class I and class II ERVs, the depletion of HP1α, HP1β and HP1γ, alone or in combination, is not sufficient for derepression of these elements in mESCs. While loss of HP1α or HP1β leads to modest defects in DNA methylation of ERVs or spreading of H4K20me3 into flanking genomic sequence, respectively, neither protein affects H3K9me3 or H4K20me3 in ERV bodies. Furthermore, using novel ERV reporter constructs targeted to a specific genomic site, we demonstrate that, relative to Setdb1, knockdown of the remaining known H3K9me3 readers expressed in mESCs, including Cdyl, Cdyl2, Cbx2, Cbx7, Mpp8, Uhrf1 and Jarid1a-c, leads to only modest proviral reactivation. Conclusion Taken together, these results reveal that each of the known H3K9me3-binding proteins is dispensable for SETDB1-mediated ERV silencing. We speculate that H3K9me3 might maintain ERVs in a silent state in mESCs by directly inhibiting deposition of active covalent histone marks.
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Affiliation(s)
- Irina A Maksakova
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3.
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Affiliation(s)
- Prim B Singh
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, D-23845 Borstel, Germany.
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Mosch K, Franz H, Soeroes S, Singh PB, Fischle W. HP1 recruits activity-dependent neuroprotective protein to H3K9me3 marked pericentromeric heterochromatin for silencing of major satellite repeats. PLoS One 2011; 6:e15894. [PMID: 21267468 PMCID: PMC3022755 DOI: 10.1371/journal.pone.0015894] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 11/29/2010] [Indexed: 11/19/2022] Open
Abstract
H3 lysine 9 trimethylation (H3K9me3) is a histone posttranslational modification (PTM) that has emerged as hallmark of pericentromeric heterochromatin. This constitutive chromatin domain is composed of repetitive DNA elements, whose transcription is differentially regulated. Mammalian cells contain three HP1 proteins, HP1α, HP1β and HP1γ These have been shown to bind to H3K9me3 and are thought to mediate the effects of this histone PTM. However, the mechanisms of HP1 chromatin regulation and the exact functional role at pericentromeric heterochromatin are still unclear. Here, we identify activity-dependent neuroprotective protein (ADNP) as an H3K9me3 associated factor. We show that ADNP does not bind H3K9me3 directly, but that interaction is mediated by all three HP1 isoforms in vitro. However, in cells ADNP localization to areas of pericentromeric heterochromatin is only dependent on HP1α and HP1β. Besides a PGVLL sequence patch we uncovered an ARKS motif within the ADNP homeodomain involved in HP1 dependent H3K9me3 association and localization to pericentromeric heterochromatin. While knockdown of ADNP had no effect on HP1 distribution and heterochromatic histone and DNA modifications, we found ADNP silencing major satellite repeats. Our results identify a novel factor in the translation of H3K9me3 at pericentromeric heterochromatin that regulates transcription.
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Affiliation(s)
- Kerstin Mosch
- Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Henriette Franz
- Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Szabolcs Soeroes
- Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Prim B. Singh
- Division of Immunoepigenetics, Research Center Borstel, Borstel, Germany
| | - Wolfgang Fischle
- Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- * E-mail:
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Bullwinkel J, Lüdemann A, Debarry J, Singh PB. Epigenotype switching at the CD14 and CD209 genes during differentiation of human monocytes to dendritic cells. Epigenetics 2011; 6:45-51. [PMID: 20818162 DOI: 10.4161/epi.6.1.13314] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Using an in vitro model for the differentiation of human blood-derived monocytes into dendritic cells (DCs), we have undertaken an investigation of epigenetic changes that take place at CD14 and CD209 (DC-SIGN) genes that encode cell surface antigens that are crucial for the function of monocytes and DCs, respectively. Upon differentiation the cell surface expression of CD14 is lost, whilst CD209 expression is increased. These reciprocal changes are associated with the loss of epigenetic markers of "activation" at the CD14 locus, but the acquisition of the same at the CD209 locus. There is little change in "repressive" histone marks and CpG methylation at the CD14 locus. By contrast there are changes in both the "repressive" histone marks and CpG methylation at the CD209 locus. In particular, two CpG dinucleotides, designated CpG2 and CpG3, show a marked demethylation at the CD209 promoter upon differentiation. These data provide insight into the epigenetic demands that are necessary to effect the reciprocal changes in expression of the CD14 and CD209 genes upon terminal differentiation of monocytes into DCs. For repression of the active CD14 gene the loss of "activation" histone modifications is likely necessary and sufficient for silencing. By contrast the activation of the silent CD209 gene appears to require an acquisition of "active" histone modifications and concomitant loss of both "repressive" histone marks and CpG methylation.
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Affiliation(s)
- Jörn Bullwinkel
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, Borstel, Germany
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Singh PB. HP1 proteins--what is the essential interaction? Genetika 2010; 46:1424-1429. [PMID: 21250545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
There are three mammalian HP1 genes, Cbx5 (encoding HP1alpha), Cbx1 (encoding HP1beta) and Cbx3 (encoding HP1gamma). Despite their high degree of sequence homology mutational analysis has revealed different phenotypes indicating that they possess different functions. Notably, the Cbx1 mutation is lethal in its homozygous condition. The Cbx1 null phenotype is therefore more severe than the Suv(3)9h1/h2 double-mutant mouse, indicating that the essential function of the Cbx1 gene product, HP1beta, is likely to lie outside its interaction with the heterochromatic H3K9me3 determinant of the "histone code" imposed by the Suv(3)9h1/h2 HMTases. Comparisons of HPI mutants in flies and fungi with corresponding mutations in Suv(3)9 genes show that HP1 mutations are invariably more severe than mutation in Suv(3)9 genes. The implications of these data for HP1 function are discussed.
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Affiliation(s)
- P B Singh
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, D-23845 Borstel, Germany.
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Abstract
In this study, we investigated inter-individual differences in sensitivity to mono-sodium glutamate (MSG) and elucidated the familiarity to umami taste in two European populations. The study consisted of two parts: (1) a survey based on questionnaire and (2) psychophysical screening for inter-individual variation of MSG sensitivity. The psychophysical tests revealed that 3.2% of the German participants and 4.6% of the Norwegian participants were potential non-tasters of MSG. In conclusion, our study confirms inter-individual differences in sensitivity to MSG in humans.
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Affiliation(s)
- P B Singh
- Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Billur M, Bartunik HD, Singh PB. The essential function of HP1 beta: a case of the tail wagging the dog? Trends Biochem Sci 2010; 35:115-23. [PMID: 19836960 DOI: 10.1016/j.tibs.2009.09.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 08/27/2009] [Accepted: 09/03/2009] [Indexed: 12/25/2022]
Abstract
A large body of work in various organisms has shown that the presence of HP1 structural proteins and methylated lysine 9 of histone H3 (H3K9me) represent the characteristic hallmarks of heterochromatin. We propose that a more critical assessment of the physiological importance of the H3K9me-HP1 interaction is warranted in light of recent studies on the mammalian HP1 beta protein. Based on this new research, we conclude that the essential function of HP1 beta (and perhaps that of its orthologues in other species) lies outside the canonical heterochromatic H3K9me-HP1 interaction. We suggest instead that binding of a small fraction of HP1 beta to the H3 histone fold performs a critical role in heterochromatin function and organismal survival.
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Affiliation(s)
- Mustafa Billur
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Forschungszentrum Borstel, D-23845 Borstel, Germany
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Abstract
Achieving reimbursement for regenerative medicine products is potentially a greater challenge than gaining US FDA approval, making it a decisive factor in the success or failure of small businesses. However, the mechanisms by which reimbursement is achieved are still seen as something of a ‘black box’, especially to those outside of the USA. This report aims to provide insights into the mechanisms of reimbursement and variety of payers in the USA, and to act as a starting point for a successful US reimbursement strategy. Fundamental concepts such as coverage, payment and coding are explained and linked with the factors that potentially determine the successful reimbursement of regenerative medicine products, including cost of goods and clinical study design. Finally, important considerations for the design of clinical studies that satisfy both the payers and the FDA are discussed and the key elements of a successful company strategy identified.
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Affiliation(s)
| | - PB Singh
- Centre for Biological Engineering, Loughborough University, Loughborough, LE11 3TU, UK
| | - D Smith
- Pepper Hamilton Law LLP, Pittsburgh, PA 15219-2502, USA
| | - P Hourd
- Centre for Biological Engineering, Loughborough University, Loughborough, LE11 3TU, UK
| | - DJ Williams
- Centre for Biological Engineering, Loughborough University, Loughborough, LE11 3TU, UK
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Brown JP, Bullwinkel J, Baron-Lühr B, Billur M, Schneider P, Winking H, Singh PB. HP1gamma function is required for male germ cell survival and spermatogenesis. Epigenetics Chromatin 2010; 3:9. [PMID: 20423503 PMCID: PMC2877046 DOI: 10.1186/1756-8935-3-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Accepted: 04/27/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND HP1 proteins are conserved components of eukaryotic constitutive heterochromatin. In mammals, there are three genes that encode HP1-like proteins, termed HP1alpha, HP1beta and HP1gamma, which have a high degree of homology This paper describes for the first time, to our knowledge, the physiological function of HP1gamma using a gene-targeted mouse. RESULTS While targeting the Cbx3 gene (encoding the HP1gamma protein) with a conditional targeting vector, we generated a hypomorphic allele (Cbx3hypo), which resulted in much reduced (barely detectable) levels of HP1gamma protein. Homozygotes for the hypomorphic allele (Cbx3hypo/hypo) are rare, with only 1% of Cbx3hypo/hypo animals reaching adulthood. Adult males exhibit a severe hypogonadism that is associated with a loss of germ cells, with some seminiferous tubules retaining only the supporting Sertoli cells (Sertoli cell-only phenotype). The percentage of seminiferous tubules that are positive for L1 ORF1 protein (ORF1p) in Cbx3hypo/hypo testes is greater than that for wild-type testes, indicating that L1 retrotransposon silencing is reversed, leading to ectopic expression of ORF1p in Cbx3hypo/hypo germ cells. CONCLUSIONS The Cbx3 gene product (the HP1gamma protein) has a non-redundant function during spermatogenesis that cannot be compensated for by the other two HP1 isotypes. The Cbx3hypo/hypo spermatogenesis defect is similar to that found in Miwi2 and Dnmt3L mutants. The Cbx3 gene-targeted mice generated in this study provide an appropriate model for the study of HP1gamma in transposon silencing and parental imprinting.
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Affiliation(s)
- Jeremy P Brown
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, D-23845 Borstel, Germany.
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Behura SK, Sharatchandra LK, Ghosh B, Soni A, Singh S, Singh RG, Prakash J, Singh PB. 003 Urine MCP-1 to diagnose acute renal allograft rejection – a pilot study. Indian Journal of Transplantation 2010. [DOI: 10.1016/s2212-0017(11)60046-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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Mirghomizadeh F, Bullwinkel J, Orinska Z, Janssen O, Petersen A, Singh PB, Bulfone-Paus S. Transcriptional regulation of mouse mast cell protease-2 by interleukin-15. J Biol Chem 2009; 284:32635-41. [PMID: 19801677 DOI: 10.1074/jbc.m109.015446] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Mast cells (MCs) play a critical role in innate and adaptive immunity through the release of cytokines, chemokines, lipid mediators, biogenic amines, and proteases. We recently showed that the activities of MC proteases are transcriptionally regulated by intracellularly retained interleukin-15 (IL-15), and we provided evidence that this cytokine acts as a specific regulator of mouse mast cell protease-2 (mMCP-2). Here, we show that in wild-type bone marrow-derived mast cells (BMMCs) IL-15 inhibits mMCP-2 transcription indirectly by inducing differential expression and mMCP-2 promoter binding of the bifunctional transcription factors C/EBPbeta and YY1. In wild-type BMMCs, C/EBPbeta expression predominates over YY1 expression, and thus C/EBPbeta preferentially binds to the mMCP-2 promoter. In IL-15-deficient BMMCs, the opposite is found: YY1 expression predominates and binds to the mMCP-2 promoter at the expense of C/EBPbeta. Hypertranscription of the mMCP-2 gene in IL-15-deficient BMMCs is associated with histone acetylation and, intriguingly, with methylation of non-CpG dinucleotides within the MCP-2 promoter. This suggests a novel model of cytokine-controlled protease transcription: non-CpG methylation maintains a chromosomal domain in an "open" configuration that is permissive for gene expression.
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Affiliation(s)
- Farhad Mirghomizadeh
- Division of Immunobiology, Department of Immunology and Cell Biology, Research Center Borstel, 23845 Borstel, Germany
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Aucott R, Bullwinkel J, Yu Y, Shi W, Billur M, Brown JP, Menzel U, Kioussis D, Wang G, Reisert I, Weimer J, Pandita RK, Sharma GG, Pandita TK, Fundele R, Singh PB. HP1-beta is required for development of the cerebral neocortex and neuromuscular junctions. ACTA ACUST UNITED AC 2008; 183:597-606. [PMID: 19015315 PMCID: PMC2582898 DOI: 10.1083/jcb.200804041] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
HP1 proteins are thought to be modulators of chromatin organization in all mammals, yet their exact physiological function remains unknown. In a first attempt to elucidate the function of these proteins in vivo, we disrupted the murine Cbx1 gene, which encodes the HP1-β isotype, and show that the Cbx1−/−-null mutation leads to perinatal lethality. The newborn mice succumbed to acute respiratory failure, whose likely cause is the defective development of neuromuscular junctions within the endplate of the diaphragm. We also observe aberrant cerebral cortex development in Cbx1−/− mutant brains, which have reduced proliferation of neuronal precursors, widespread cell death, and edema. In vitro cultures of neurospheres from Cbx1−/− mutant brains reveal a dramatic genomic instability. Our results demonstrate that HP1 proteins are not functionally redundant and that they are likely to regulate lineage-specific changes in heterochromatin organization.
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Affiliation(s)
- Rebecca Aucott
- Division of Immunoepigenetics, Department of Immunology and Cell Biology, Research Center Borstel, Borstel, Germany
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Goyal NK, Kumar A, Das SK, Pandey AK, Sharma GK, Trivedi S, Dwivedi US, Singh PB. Experience with plaque excision and dermal grafting in the surgical treatment of Peyronie's disease. Singapore Med J 2008; 49:805-808. [PMID: 18946615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
INTRODUCTION Peyronie's disease is a common cause of sexual dysfunction. We assess the technique of plaque excision and dermal grafting for the treatment of Peyronie's disease. METHODS A total of 11 patients, aged 38-55 years, were operated for Peyronie's disease. All patients had stable plaque on the dorsum or dorsolateral aspect of the penile shaft. All patients had penile curvature, nine (81.8 percent) had painful erections, six (54.5 percent) had penile pain and three (27.3 percent) had erectile dysfunction. All suffered difficulty in intercourse. We performed plaque excision and dermal grafting. Main outcome measures were relief of penile pain, relief of painful erection, performance of satisfactory coitus and straight penis while erection. RESULTS All patients had relief of penile pain and painful erection. Nine (81.8 percent) patients had straight penis and had satisfactory coitus. Two (18.2 percent) patients suffered postoperative erectile dysfunction which was mild and responded to Sildenafil tabs. CONCLUSION Although experience with this technique is limited, the initial results are encouraging. We found this technique feasible with satisfactory results.
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Affiliation(s)
- N K Goyal
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India
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Singh PB, Saw NK, Haq A, Blades RA, Martin FL, Matanhelia SS, Nicholson CM. Use of tissue ink to maintain identification of individual cores on needle biopsies of the prostate. J Clin Pathol 2008; 61:1055-7. [PMID: 18641411 DOI: 10.1136/jcp.2008.058545] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND There is an increasing necessity to extract the maximum amount of information, beyond even a cancer diagnosis, from prostate biopsies. Thus, maintaining site-specific information regarding individual biopsy cores might be critical. AIM To evaluate the applicability of employing tissue ink to maintain the identity of individual prostatic biopsy cores. METHOD In this ongoing study, 12 core prostate biopsy specimens are sent to the laboratory in individual pots labelled according to anatomical site. The specimens are placed in two separate multi-compartment cassettes. They are inked with different colours to identify the site of origin from each lobe. The cassettes are then processed with a single paraffin block for each side; the six cores from each side can be mounted on a single slide. RESULTS The different colours used adhere well to the biopsy cores, thus maintaining the identity of each core. Six cores from each side are embedded in a single paraffin block and examined on a single slide, making it cost-effective, while maintaining high quality, accurate histopathological information. CONCLUSION Differential inking of prostate biopsy cores is an easily applicable method that is cost-effective and provides tumour location information. Prostate biopsy data archived to maintain individual core information might be used to determine applicability of such information to predict extra-capsular extension by correlating with imaging and radical prostatectomy findings, and for treatment planning.
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Affiliation(s)
- P B Singh
- Lancashire Teaching Hospitals NHS Foundation Trust, Fulwood, Preston, UK.
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Abstract
Bilateral single system ureteral ectopia (BSSEU) is one of the rarest entities in urology, with less than 80 cases reported so far. Incontinence resulting from the underlying anomaly can be devastating to the child. It is generally agreed that suitable urinary continence and long dry intervals are seldom obtainable because of poorly developed trigone and bladder neck area. We herein report a case of BSSEU managed by bilateral ureteric reimplantation, achieving satisfactory continence and bladder capacity without the need for urinary diversion or bladder neck reconstruction.
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Affiliation(s)
- A Kumar
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi - 221 005, India
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Kumar A, Goyal NK, Trivedi S, Dwivedi US, Singh PB. Primary cavernous hemangioma of the glans penis: rare case report with a review of the literature. Aesthetic Plast Surg 2008; 32:386-8. [PMID: 18176821 DOI: 10.1007/s00266-007-9076-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Hemangiomas of the urinary tract are rare lesions, and those of the glans penis are even rarer. A 23-year-old man with a hemangioma of the glans penis treated successfully with intralesional sclerotherapy is presented. Other options for the management of this disorder are discussed.
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Affiliation(s)
- A Kumar
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, (UP) 221005, India
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Cowell IG, Sunter NJ, Singh PB, Austin CA, Durkacz BW, Tilby MJ. gammaH2AX foci form preferentially in euchromatin after ionising-radiation. PLoS One 2007; 2:e1057. [PMID: 17957241 PMCID: PMC2020439 DOI: 10.1371/journal.pone.0001057] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Accepted: 10/02/2007] [Indexed: 12/29/2022] Open
Abstract
Background The histone variant histone H2A.X comprises up to 25% of the H2A complement in mammalian cells. It is rapidly phosphorylated following exposure of cells to double-strand break (DSB) inducing agents such as ionising radiation. Within minutes of DSB generation, H2AX molecules are phosphorylated in large chromatin domains flanking DNA double-strand breaks (DSBs); these domains can be observed by immunofluorescence microscopy and are termed γH2AX foci. H2AX phosphorylation is believed to have a role mounting an efficient cellular response to DNA damage. Theoretical considerations suggest an essentially random chromosomal distribution of X-ray induced DSBs, and experimental evidence does not consistently indicate otherwise. However, we observed an apparently uneven distribution of γH2AX foci following X-irradiation with regions of the nucleus devoid of foci. Methodology/Principle Findings Using immunofluorescence microscopy, we show that focal phosphorylation of histone H2AX occurs preferentially in euchromatic regions of the genome following X-irradiation. H2AX phosphorylation has also been demonstrated previously to occur at stalled replication forks induced by UV radiation or exposure to agents such as hydroxyurea. In this study, treatment of S-phase cells with hydroxyurea lead to efficient H2AX phosphorylation in both euchromatin and heterochromatin at times when these chromatin compartments were undergoing replication. This suggests a block to H2AX phosphorylation in heterochromatin that is at least partially relieved by ongoing DNA replication. Conclusions/Significance We discus a number of possible mechanisms that could account for the observed pattern of H2AX phosphorylation. Since γH2AX is regarded as forming a platform for the recruitment or retention of other DNA repair and signaling molecules, these findings imply that the processing of DSBs in heterochromatin differs from that in euchromatic regions. The differential responses of heterochromatic and euchromatic compartments of the genome to DSBs will have implications for understanding the processes of DNA repair in relation to nuclear and chromatin organization.
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Affiliation(s)
- Ian G Cowell
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
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Singh PB, Singh V, Srivastava S, Pandey S. Effects of estradiol-17beta and 17alpha, 20beta-dihydroxy-4-pregnen-3-one on different phospholipids metabolism and histological changes in ovary during reproductive growth in the catfish, Heteropneustes fossilis (Bloch). J Environ Biol 2007; 28:771-778. [PMID: 18405111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Effect of cumulative doses of estradiol -17beta (E2-7, 14 and 28 mg/kg body weight) and 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17alpha,20betaP-7, 14 and 28 mg/kg body weight) on total phospholipids (TP) and various phospholipids- phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI) and phosphatidylethanolamine (PE) on liver plasma and ovary were investigated during the reproductively active preparatory and prespawning phases of the annual reproductive cycle in the freshwater female catfish, H. fossilis. The effect of E2 on TP was generally stimulatory and has pronounced effect than 17alpha,20betaP during both the phases. The levels of PC was promoted high during prespawning phase by E2 comparatively very less than by 17alpha, 20betaP in studied tissues during both the phases. The levels of PS after E2 treatments was maximum in all tissues during prespawning phase whereas 17alpha,20betaP was effective only in liver during this phase. The PI was elevated in liver during preparatory phase but its elevation was in all studied tissues during prespawning phase after E2 treatments. The levels of PI was most effective in ovary during preparatory phase in response to 17alpha,20betaP. The levels of PE was declined in liver but elevated in ovary after E2 treatments during both the phases. Treatments of E2 during preparatory phase showed greater number of vitellogenic oocytes as compared to 17alpha,20betaP treatments. The present finding has demonstrated that estradiol-17beta has more pronounced effects than the 17alpha,20beta P in regulation of different phospholipids and ovarian recrudescence during reproductively active phases and among the phospholipids the PC is the main phospholipids of vitellogenin/ovarian lipids in H. fossilis.
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Affiliation(s)
- P B Singh
- Department of Zoology, Tilak Dhari (PG) College, Jaunpur-222 002, India.
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Abstract
We have compared the distribution of endogenous heterochromatin protein 1 (HP1) proteins (α, β and γ) in different epithelial lines, pluripotent stem cells and embryonic fibroblasts. In parallel, we have interrogated assembly and dynamics of newly expressed HP1-GFP proteins in cells lacking both HP1α and HP1β alleles, blocked at the G1-S boundary, or cultured in the presence of HDAC and HAT inhibitors. The results reveal a range of cell type and differentiation state-specific patterns that do not correlate with `fast' or `slow' subunit exchange in heterochromatin. Furthermore, our observations show that targeting of HP1γ to heterochromatic sites depends on HP1α and H1β and that, on an architectural level, HP1α is the most polymorphic variant of the HP1 family. These data provide evidence for HP1 plasticity under shifting microenvironmental conditions and offer a new conceptual framework for understanding chromatin dynamics at the molecular level.
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Affiliation(s)
- George K Dialynas
- The Stem Cell and Chromatin Group, Laboratory of Biology, The University of Ioannina, School of Medicine and The Institute of Biomedical Research (FORTH/BRI), 45 110 Ioannina, Greece
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44
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Abstract
Interleukin-21 is the most recently discovered member of the type-I cytokine family. Structurally, IL-21 shows homology to IL-2, IL-4, and IL-15 proteins. IL-21 shares the common gamma-chain with the other three cytokines but, in addition, binds to a unique IL-21Ralpha chain, and activates the JAK/STAT pathway. IL-21 is mainly produced by activated T-cells but targets a broad range of lymphoid and myeloid cells of the immune system and therefore is able to regulate innate and acquired immune responses. This review intends to give the reader an overview of the recent findings concerning the biology of IL-21 and its physiological role in immunity, infection, and cancer.
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Affiliation(s)
- Katja Brandt
- Research Center Borstel, Department of Immunology and Cell Biology, Parkallee 22, Borstel, Germany
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45
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Takada Y, Isono KI, Shinga J, Turner JMA, Kitamura H, Ohara O, Watanabe G, Singh PB, Kamijo T, Jenuwein T, Burgoyne PS, Koseki H. Mammalian Polycomb Scmh1 mediates exclusion of Polycomb complexes from the XY body in the pachytene spermatocytes. Development 2007; 134:579-90. [PMID: 17215307 DOI: 10.1242/dev.02747] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The product of the Scmh1 gene, a mammalian homolog of Drosophila Sex comb on midleg, is a constituent of the mammalian Polycomb repressive complexes 1 (Prc1). We have identified Scmh1 as an indispensable component of the Prc1. During progression through pachytene, Scmh1 was shown to be excluded from the XY body at late pachytene, together with other Prc1 components such as Phc1, Phc2, Rnf110 (Pcgf2), Bmi1 and Cbx2. We have identified the role of Scmh1 in mediating the survival of late pachytene spermatocytes. Apoptotic elimination of Scmh1(-/-) spermatocytes is accompanied by the preceding failure of several specific chromatin modifications at the XY body, whereas synapsis of homologous autosomes is not affected. It is therefore suggested that Scmh1 is involved in regulating the sequential changes in chromatin modifications at the XY chromatin domain of the pachytene spermatocytes. Restoration of defects in Scmh1(-/-) spermatocytes by Phc2 mutation indicates that Scmh1 exerts its molecular functions via its interaction with Prc1. Therefore, for the first time, we are able to indicate a functional involvement of Prc1 during the meiotic prophase of male germ cells and a regulatory role of Scmh1 for Prc1, which involves sex chromosomes.
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Affiliation(s)
- Yuki Takada
- RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro, Yokohama, Japan
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46
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Datta B, Rao MP, Acharya RL, Goel N, Saxena V, Trivedi S, Dwivedi US, Singh PB. Dorsal onlay buccal mucosal graft urethroplasty in long anterior urethral stricture. Int Braz J Urol 2007; 33:181-6; discussion 186-7. [PMID: 17488537 DOI: 10.1590/s1677-55382007000200008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2006] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE To assess the success of buccal mucosal graft (BMG) urethroplasty by the dorsal onlay technique in long anterior urethral stricture (> 2 cm long) through the midline perineal incision. MATERIALS AND METHODS From January 1998 to December 2003, 43 patients with long anterior urethral strictures were managed by dorsal onlay BMG urethroplasty. After voiding trial, they were followed up at 3 months with uroflowmetry, retrograde urethrogram (RGU) and American Urological Association symptoms score (AUA symptoms scores). Successful outcome was defined as normal voiding with a maximum one attempt of visual internal urethrotomy (VIU) after catheter removal. Patients were further followed-up with uroflowmetry at 3 months interval and RGU every 6 months interval. RESULTS Mean stricture length was 4.8 cm (range 3 to 9 cm) and mean follow up was 48 months (range 12 to 84 months). Only five patients were found to develop stricture at anastomotic site, during follow-up. Two of them voided normally after single attempt of VIU. Other three patients (6.9%) required further open surgery or repeat VIU during follow up and were considered as failure. CONCLUSION Dorsal onlay BMG urethroplasty is a simple technique with good surgical outcome.
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Affiliation(s)
- Biswajit Datta
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
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47
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Goyal NK, Trivedi S, Dwivedi US, Singh PB. Congenital mucus retention cyst of penis presenting as skin papilloma. Urology 2007; 69:381. [PMID: 17320684 DOI: 10.1016/j.urology.2006.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 08/13/2006] [Accepted: 10/04/2006] [Indexed: 11/29/2022]
Affiliation(s)
- Neeraj Kumar Goyal
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi (U.P.), India
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48
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Bongiorni S, Pasqualini B, Taranta M, Singh PB, Prantera G. Epigenetic regulation of facultative heterochromatinisation in Planococcus citri via the Me(3)K9H3-HP1-Me(3)K20H4 pathway. J Cell Sci 2007; 120:1072-80. [PMID: 17327272 DOI: 10.1242/jcs.03412] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Using RNA interference (RNAi) we have conducted a functional analysis of the HP1-like chromobox gene pchet2 during embryogenesis of the mealybug Planococcus citri. Knocking down pchet2 expression results in decondensation of the male-specific chromocenter that normally arises from the developmentally-regulated facultative heterochromatinisation of the paternal chromosome complement. Together with the disappearance of the chromocenter the staining levels of two associated histone modifications, tri-methylated lysine 9 of histone H3 [Me(3)K9H3] and tri-methylated lysine 20 of histone H4 [Me(3)K20H4], are reduced to undetectable levels. Embryos treated with double-stranded RNA (dsRNA) targeting pchet2 also exhibit chromosome abnormalities, such as aberrant chromosome condensation, and also the presence of metaphases that contain 'lagging' chromosomes. We conclude that PCHET2 regulates chromosome behavior during metaphase and is a crucial component of a Me(3)K9H3-HP1-Me(3)K20H4 pathway involved in the facultative heterochromatinisation of the (imprinted) paternal chromosome set.
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Affiliation(s)
- Silvia Bongiorni
- Department of Agrobiologia e Agrochimica, University of Tuscia, 01100 Viterbo, Italy
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49
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Goyal NK, Dwivedi US, Vyas N, Rao MP, Trivedi S, Singh PB. A decade's experience with vesicovaginal fistula in India. Int Urogynecol J 2006; 18:39-42. [PMID: 17006615 DOI: 10.1007/s00192-006-0068-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 01/13/2006] [Indexed: 10/24/2022]
Abstract
A retrospective analysis of 252 cases of vesicovaginal fistulae was done to analyse its etio-pathology and management in an Indian population. After a thorough evaluation, different techniques of fistula closure were used for repair and the results were listed. The main outcome measures were the etiology of the fistula, need for tissue interposition and cure rate per repair as well as the overall cure rate. We compared our results with literature and concluded that simple and small fistulae should be repaired with layered closure. All complicated fistulae should be repaired with tissue interposition or tissue graft. This is the first study from India compiling 10 years of experience on vesicovaginal fistula.
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Affiliation(s)
- Neeraj K Goyal
- Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, 221 005, India.
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50
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Abstract
Mouse chromocenters are clusters of late-replicating pericentric heterochromatin containing HP1 bound to trimethylated lysine 9 of histone H3 (Me3K9H3). Using a cell-free system to initiate replication within G1-phase nuclei, we demonstrate that chromocenters acquire the property of late replication coincident with their reorganization after mitosis and the establishment of a global replication timing program. HP1 dissociated during mitosis but rebound before the establishment of late replication, and removing HP1 from chromocenters by competition with Me3K9H3 peptides did not result in early replication, demonstrating that this interaction is neither necessary nor sufficient for late replication. However, in cells lacking the Suv39h1,2 methyltransferases responsible for K9H3 trimethylation and HP1 binding at chromocenters, replication of chromocenter DNA was advanced by 10–15% of the length of S phase. Reintroduction of Suv39h1 activity restored the later replication time. We conclude that Suv39 activity is required for the fine-tuning of pericentric heterochromatin replication relative to other late-replicating domains, whereas separate factors establish a global replication timing program during early G1 phase.
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Affiliation(s)
- Rong Wu
- Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, NY 13210, USA
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