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Larsen HL, Grapin-Botton A. The molecular and morphogenetic basis of pancreas organogenesis. Semin Cell Dev Biol 2017; 66:51-68. [PMID: 28089869 DOI: 10.1016/j.semcdb.2017.01.005] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 01/08/2023]
Abstract
The pancreas is an essential endoderm-derived organ that ensures nutrient metabolism via its endocrine and exocrine functions. Here we review the essential processes governing the embryonic and early postnatal development of the pancreas discussing both the mechanisms and molecules controlling progenitor specification, expansion and differentiation. We elaborate on how these processes are orchestrated in space and coordinated with morphogenesis. We draw mainly from experiments conducted in the mouse model but also from investigations in other model organisms, complementing a recent comprehensive review of human pancreas development (Jennings et al., 2015) [1]. The understanding of pancreas development in model organisms provides a framework to interpret how human mutations lead to neonatal diabetes and may contribute to other forms of diabetes and to guide the production of desired pancreatic cell types from pluripotent stem cells for therapeutic purposes.
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Affiliation(s)
- Hjalte List Larsen
- DanStem, University of Copenhagen, 3 B Blegdamsvej, DK-2200 Copenhagen N, Denmark
| | - Anne Grapin-Botton
- DanStem, University of Copenhagen, 3 B Blegdamsvej, DK-2200 Copenhagen N, Denmark.
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2
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Prasadan K, Shiota C, Xiangwei X, Ricks D, Fusco J, Gittes G. A synopsis of factors regulating beta cell development and beta cell mass. Cell Mol Life Sci 2016; 73:3623-37. [PMID: 27105622 PMCID: PMC5002366 DOI: 10.1007/s00018-016-2231-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 03/24/2016] [Accepted: 04/14/2016] [Indexed: 12/29/2022]
Abstract
The insulin-secreting beta cells in the endocrine pancreas regulate blood glucose levels, and loss of functional beta cells leads to insulin deficiency, hyperglycemia (high blood glucose) and diabetes mellitus. Current treatment strategies for type-1 (autoimmune) diabetes are islet transplantation, which has significant risks and limitations, or normalization of blood glucose with insulin injections, which is clearly not ideal. The type-1 patients can lack insulin counter-regulatory mechanism; therefore, hypoglycemia is a potential risk. Hence, a cell-based therapy offers a better alternative for the treatment of diabetes. Past research was focused on attempting to generate replacement beta cells from stem cells; however, recently there has been an increasing interest in identifying mechanisms that will lead to the conversion of pre-existing differentiated endocrine cells into beta cells. The goal of this review is to provide an overview of several of the key factors that regulate new beta cell formation (neogenesis) and beta cell proliferation.
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Affiliation(s)
- Krishna Prasadan
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA
| | - Chiyo Shiota
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA
| | - Xiao Xiangwei
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA
| | - David Ricks
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA
| | - Joseph Fusco
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA
| | - George Gittes
- Rangos Research Center, Children's Hospital of University of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, 15224, USA.
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3
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Kaneto H, Matsuoka TA. Role of pancreatic transcription factors in maintenance of mature β-cell function. Int J Mol Sci 2015; 16:6281-97. [PMID: 25794287 PMCID: PMC4394532 DOI: 10.3390/ijms16036281] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 02/10/2015] [Accepted: 02/16/2015] [Indexed: 12/12/2022] Open
Abstract
A variety of pancreatic transcription factors including PDX-1 and MafA play crucial roles in the pancreas and function for the maintenance of mature β-cell function. However, when β-cells are chronically exposed to hyperglycemia, expression and/or activities of such transcription factors are reduced, which leads to deterioration of β-cell function. These phenomena are well known as β-cell glucose toxicity in practical medicine as well as in the islet biology research area. Here we describe the possible mechanism for β-cell glucose toxicity found in type 2 diabetes. It is likely that reduced expression levels of PDX-1 and MafA lead to suppression of insulin biosynthesis and secretion. In addition, expression levels of incretin receptors (GLP-1 and GIP receptors) in β-cells are decreased, which likely contributes to the impaired incretin effects found in diabetes. Taken together, down-regulation of insulin gene transcription factors and incretin receptors explains, at least in part, the molecular mechanism for β-cell glucose toxicity.
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Affiliation(s)
- Hideaki Kaneto
- Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, 577, Matsushima, Kurashiki 701-0192, Japan.
| | - Taka-aki Matsuoka
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan.
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Kumar SS, Alarfaj AA, Munusamy MA, Singh AJAR, Peng IC, Priya SP, Hamat RA, Higuchi A. Recent developments in β-cell differentiation of pluripotent stem cells induced by small and large molecules. Int J Mol Sci 2014; 15:23418-47. [PMID: 25526563 PMCID: PMC4284775 DOI: 10.3390/ijms151223418] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/03/2014] [Accepted: 12/08/2014] [Indexed: 12/21/2022] Open
Abstract
Human pluripotent stem cells, including human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), hold promise as novel therapeutic tools for diabetes treatment because of their self-renewal capacity and ability to differentiate into beta (β)-cells. Small and large molecules play important roles in each stage of β-cell differentiation from both hESCs and hiPSCs. The small and large molecules that are described in this review have significantly advanced efforts to cure diabetic disease. Lately, effective protocols have been implemented to induce hESCs and human mesenchymal stem cells (hMSCs) to differentiate into functional β-cells. Several small molecules, proteins, and growth factors promote pancreatic differentiation from hESCs and hMSCs. These small molecules (e.g., cyclopamine, wortmannin, retinoic acid, and sodium butyrate) and large molecules (e.g. activin A, betacellulin, bone morphogentic protein (BMP4), epidermal growth factor (EGF), fibroblast growth factor (FGF), keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), noggin, transforming growth factor (TGF-α), and WNT3A) are thought to contribute from the initial stages of definitive endoderm formation to the final stages of maturation of functional endocrine cells. We discuss the importance of such small and large molecules in uniquely optimized protocols of β-cell differentiation from stem cells. A global understanding of various small and large molecules and their functions will help to establish an efficient protocol for β-cell differentiation.
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Affiliation(s)
- S Suresh Kumar
- Department of Medical Microbiology and Parasitology, Universities Putra Malaysia, Serdang 43400, Selangor, Malaysia.
| | - Abdullah A Alarfaj
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Murugan A Munusamy
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
| | - A J A Ranjith Singh
- Department of Bioscience, Jacintha Peter College of Arts and Sciences, Ayakudi, Tenkasi, Tamilnadu 627852, India.
| | - I-Chia Peng
- Department of Chemical and Materials Engineering, National Central University, No. 300, Jhongda RD., Jhongli, Taoyuan 32001, Taiwan.
| | - Sivan Padma Priya
- Department of Basic Science and Department of Surgical Sciences, Ajman University of Science and Technology-Fujairah Campus, P.O. Box 9520, Al Fujairah, United Arab Emirates.
| | - Rukman Awang Hamat
- Department of Medical Microbiology and Parasitology, Universities Putra Malaysia, Serdang 43400, Selangor, Malaysia.
| | - Akon Higuchi
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
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Kanherkar RR, Bhatia-Dey N, Csoka AB. Epigenetics across the human lifespan. Front Cell Dev Biol 2014; 2:49. [PMID: 25364756 PMCID: PMC4207041 DOI: 10.3389/fcell.2014.00049] [Citation(s) in RCA: 209] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 08/22/2014] [Indexed: 12/17/2022] Open
Abstract
Epigenetics has the potential to explain various biological phenomena that have heretofore defied complete explication. This review describes the various types of endogenous human developmental milestones such as birth, puberty, and menopause, as well as the diverse exogenous environmental factors that influence human health, in a chronological epigenetic context. We describe the entire course of human life from periconception to death and chronologically note all of the potential internal timepoints and external factors that influence the human epigenome. Ultimately, the environment presents these various factors to the individual that influence the epigenome, and the unique epigenetic and genetic profile of each individual also modulates the specific response to these factors. During the course of human life, we are exposed to an environment that abounds with a potent and dynamic milieu capable of triggering chemical changes that activate or silence genes. There is constant interaction between the external and internal environments that is required for normal development and health maintenance as well as for influencing disease load and resistance. For example, exposure to pharmaceutical and toxic chemicals, diet, stress, exercise, and other environmental factors are capable of eliciting positive or negative epigenetic modifications with lasting effects on development, metabolism and health. These can impact the body so profoundly as to permanently alter the epigenetic profile of an individual. We also present a comprehensive new hypothesis of how these diverse environmental factors cause both direct and indirect epigenetic changes and how this knowledge can ultimately be used to improve personalized medicine.
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Affiliation(s)
- Riya R Kanherkar
- Epigenetics Laboratory, Department of Anatomy, Howard University Washington, DC, USA
| | - Naina Bhatia-Dey
- Epigenetics Laboratory, Department of Anatomy, Howard University Washington, DC, USA
| | - Antonei B Csoka
- Epigenetics Laboratory, Department of Anatomy, Howard University Washington, DC, USA
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Ishkitiev N, Yaegaki K, Kozhuharova A, Tanaka T, Okada M, Mitev V, Fukuda M, Imai T. Pancreatic differentiation of human dental pulp CD117⁺ stem cells. Regen Med 2014; 8:597-612. [PMID: 23998753 DOI: 10.2217/rme.13.42] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
AIM Adult stem cells cannot proliferate to produce enough cells for human transplantation with keeping stem cell characteristics shown in the primary culture. We established a novel culture protocol using human dental pulp stem cells (DPSCs) that can produce quantities sufficient for human transplantation. The present study assessed differentiation of DPSCs toward a pancreatic lineage in serum-free conditions, which is essential for safe transplantation. MATERIALS & METHODS CD117⁺ stem cells were separated from human exfoliated deciduous teeth (stem cells from human exfoliated deciduous teeth; SHED) and adult DPSCs. The cells were characterized with real-time reverse-transcription PCR for a panel of embryonal lineage markers. RESULTS 82 out of 84 markers were expressed in different levels in SHED or DPSCs. After pancreatic differentiation in vitro, we found expression of pancreatic-specific endocrine markers insulin, glucagon, somatostatin and pancreatic polypeptide, and exocrine marker amylase-2a in both cultures. We also found reprogramming in both cell cultures mimicking the embryonal stages of development of the pancreas. Transcription factors PDX1, HHEX, MNX1, NEUROG3, PAX4, PAX6 and NKX6-1, crucial markers for the pancreatic development, were all activated. Expression of these factors strongly implies that the cells differentiated toward a distinguished pancreatic lineage. CONCLUSION Our results show that CD117⁺ SHED and DPSCs are capable of differentiation toward all functional endocrine and exocrine subsets of pancreatic cells in serum-free conditions. SHED and DPSCs may therefore have great potential for future cell therapy of pancreatic disorders.
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Affiliation(s)
- Nikolay Ishkitiev
- Nippon Dental University, School of Life Dentistry at Tokyo, Department of Oral Health, 1-9-20 Chiyoda-ku, 102-8159 Tokyo, Japan
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Shi K, Parekh VI, Roy S, Desai SS, Agarwal SK. The embryonic transcription factor Hlxb9 is a menin interacting partner that controls pancreatic β-cell proliferation and the expression of insulin regulators. Endocr Relat Cancer 2013; 20:111-22. [PMID: 23419452 PMCID: PMC6250975 DOI: 10.1530/erc-12-0077] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The multiple endocrine neoplasia type 1 (MEN1) syndrome is caused by germline mutations in the MEN1 gene encoding menin, with tissue-specific tumors of the parathyroids, anterior pituitary, and enteropancreatic endocrine tissues. Also, 30-40% of sporadic pancreatic endocrine tumors show somatic MEN1 gene inactivation. Although menin is expressed in all cell types of the pancreas, mouse models with loss of menin in either pancreatic α-cells, or β-cells, or total pancreas develop β-cell-specific endocrine tumors (insulinomas). Loss of widely expressed tumor suppressor genes may produce tissue-specific tumors by reactivating one or more embryonic-specific differentiation factors. Therefore, we determined the effect of menin overexpression or knockdown on the expression of β-cell differentiation factors in a mouse β-cell line (MIN6). We show that the β-cell differentiation factor Hlxb9 is posttranscriptionally upregulated upon menin knockdown, and it interacts with menin. Hlxb9 reduces cell proliferation and causes apoptosis in the presence of menin, and it regulates genes that modulate insulin level. Thus, upon menin loss or from other causes, dysregulation of Hlxb9 predicts a possible combined mechanism for β-cell proliferation and insulin production in insulinomas. These observations help to understand how a ubiquitously expressed protein such as menin might control tissue-specific tumorigenesis. Also, our findings identify Hlxb9 as an important factor for β-cell proliferation and insulin regulation.
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MESH Headings
- Animals
- Apoptosis
- Biomarkers, Tumor/genetics
- Biomarkers, Tumor/metabolism
- Blotting, Western
- Cell Differentiation
- Cell Proliferation
- Cells, Cultured
- Chromatin Immunoprecipitation
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Fibroblasts/cytology
- Fibroblasts/metabolism
- Gene Expression Profiling
- Gene Expression Regulation, Neoplastic
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Humans
- Immunoenzyme Techniques
- Immunoprecipitation
- Insulin/genetics
- Insulin/metabolism
- Insulin-Secreting Cells/metabolism
- Insulin-Secreting Cells/pathology
- Insulinoma/genetics
- Insulinoma/metabolism
- Insulinoma/pathology
- Kidney/cytology
- Kidney/metabolism
- Mice
- Mice, Knockout
- Oligonucleotide Array Sequence Analysis
- Promoter Regions, Genetic
- Proto-Oncogene Proteins/physiology
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Two-Hybrid System Techniques
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Affiliation(s)
- Kerong Shi
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Mastracci TL, Sussel L. The endocrine pancreas: insights into development, differentiation, and diabetes. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2012; 1:609-28. [PMID: 23799564 PMCID: PMC3420142 DOI: 10.1002/wdev.44] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In the developing embryo, appropriate patterning of the endoderm fated to become pancreas requires the spatial and temporal coordination of soluble factors secreted by the surrounding tissues. Once pancreatic progenitor cells are specified in the developing gut tube epithelium, epithelial-mesenchymal interactions, as well as a cascade of transcription factors, subsequently delineate three distinct lineages, including endocrine, exocrine, and ductal cells. Simultaneous morphological changes, including branching, vascularization, and proximal organ development, also influence the process of specification and differentiation. Decades of research using mouse genetics have uncovered many of the key factors involved in pancreatic cell fate decisions. When pancreas development or islet cell functions go awry, due to mutations in genes important for proper organogenesis and development, the result can lead to a common pancreatic affliction, diabetes mellitus. Current treatments for diabetes are adequate but not curative. Therefore, researchers are utilizing the current understanding of normal embryonic pancreas development in vivo, to direct embryonic stem cells toward a pancreatic fate with the goal of transplanting these in vitro generated 'islets' into patients. Mimicking development in vitro has proven difficult; however, significant progress has been made and the current differentiation protocols are becoming more efficient. The continued partnership between developmental biologists and stem cell researchers will guarantee that the in vitro generation of insulin-producing β cells is a possible therapeutic option for the treatment of diabetes.
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Affiliation(s)
| | - Lori Sussel
- Department of Genetics and Development, Columbia University
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9
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Chen X, Fan Y, Long X, Sun X. Similar DNA methylation and histone H3 lysine 9 dimethylation patterns in tripronuclear and corrected bipronuclear human zygotes. J Reprod Dev 2010; 56:324-9. [PMID: 20197641 DOI: 10.1262/jrd.09-170a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
After fertilization, male and female gametes undergo extensive reprogramming to restore totipotency. Both DNA methylation and histone modification are important epigenetic reprogramming events. Previous studies have reported that the paternal pronucleus of the human zygote is actively demethylated to some extent, while the maternal pronucleus remains methylated. However, to our knowledge, the relationship between DNA methylation and H3K9 dimethylation patterns in human embryos has not been reported. In this study, we examined the dynamic DNA methylation and H3K9 dimethylation patterns in triploid and bipronucleated zygotes and early developing embryos. We sought to gain further insight into the relationship between DNA methylation and H3K9 dimethylation and to investigate whether removing a pronucleus from triploid zygotes affects DNA methylation and H3K9 dimethylation patterns. We found that active DNA demethylation of the two male pronuclei occurred in tripronuclear human zygotes while the female pronucleus remained methylated at 20 h post-insemination. In tripronuclear human zygotes, H3K9 was hypomethylated in the two paternal pronuclei relative to the maternal pronucleus. Our data show that there are no differences in the DNA methylation and H3K9 dimethylation patterns between tripronuclear and corrected bipronuclear human zygotes. However, correction of 3PN human zygotes dispermic in origin could not improve subsequent embryo development. In conclusion, DNA methylation and H3K9 dimethylation patterns are well correlated in tripronuclear zygotes and embryos; early embryo development is not affected by removal of a male pronucleus. Our results imply that limited developmental potential of either 3PN or corrected 2PN embryos may not be caused by the abnormalities in DNA methylation or H3K9 dimethylation modification.
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Affiliation(s)
- Xinjie Chen
- Guangzhou Key Laboratory of Reproduction and Genetics, Institute of Gynecology and Obstetrics, The Third Affiliated Hospital of Guangzhou Medical College, Guangdong, China
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10
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Pillich RT, Scarsella G, Risuleo G. Overexpression of the Pdx-1 homeodomain transcription factor impairs glucose metabolism in cultured rat hepatocytes. Molecules 2008; 13:2659-73. [PMID: 18971862 PMCID: PMC6245418 DOI: 10.3390/molecules13102659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 10/20/2008] [Accepted: 10/24/2008] [Indexed: 11/16/2022] Open
Abstract
The Pdx-1 transcription factor plays crucial functions both during pancreas development and in the adult β cells. Previous studies have indicated that ectopic Pdx-1 expression in liver or intestinal primary and immortalized cells is sufficient to promote activation of insulin gene expression. This work is focused on the molecular and physiological consequences of Pdx-1 overexpression in liver cells. We present evidence that Pdx-1 affects the level of expression of one of the four mammalian hexokinase isozymes. These are glucose phosphorylating enzymes involved in essential cellular functions such as glucose sensing, metabolic energy production and apoptosis. Specifically, our data show that over-expression of Pdx-1 in cultured hepatocytes is able to repress the expression of hexokinase 2 (Hxk 2) and the phenomenon is mediated via binding of Pdx-1 to a specific sequence on the Hxk 2 gene promoter. As a consequence, liver cells over-expressing Pdx-1 present interesting alterations concerning glucose metabolism.
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Affiliation(s)
- Rudolf Tito Pillich
- Dipartimento di Biologia Cellulare e dello Sviluppo, Sapienza Università di Roma, P.le Aldo Moro, 5 – 00185 Roma, Italy; E-mail: (R-T. P.), (G. S.)
| | - Gianfranco Scarsella
- Dipartimento di Biologia Cellulare e dello Sviluppo, Sapienza Università di Roma, P.le Aldo Moro, 5 – 00185 Roma, Italy; E-mail: (R-T. P.), (G. S.)
| | - Gianfranco Risuleo
- Dipartimento di Genetica e Biologia Molecolare, Sapienza Università di Roma, P.le Aldo Moro, 5 – 00185 Roma, Italy
- Author to whom correspondence should be addressed; E-mails: or ; Tel.: +39 0649912234; Fax: +39 064440812
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12
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Gannon M, Ables ET, Crawford L, Lowe D, Offield MF, Magnuson MA, Wright CVE. pdx-1 function is specifically required in embryonic beta cells to generate appropriate numbers of endocrine cell types and maintain glucose homeostasis. Dev Biol 2007; 314:406-17. [PMID: 18155690 DOI: 10.1016/j.ydbio.2007.10.038] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 10/16/2007] [Indexed: 10/22/2022]
Abstract
The pdx1 gene is essential for pancreatic organogenesis in humans and mice; pdx1 mutations have been identified in human diabetic patients. Specific inactivation of pdx1 in adult beta cells revealed that this gene is required for maintenance of mature beta cell function. In the following study, a Cre-lox strategy was used to remove pdx1 function specifically from embryonic beta cells beginning at late-gestation, prior to islet formation. Animals in which pdx1 is lost in insulin-producing cells during embryogenesis had elevated blood glucose levels at birth and were overtly diabetic by weaning. Neonatal and adult mutant islets showed a dramatic reduction in the number of insulin(+) cells and an increase in both glucagon(+) and somatostatin(+) cells. Lineage tracing revealed that excess glucagon(+) and somatostatin(+) cells did not arise by interconversion of endocrine cell types. Examination of mutant islets revealed a decrease in proliferation of insulin-producing cells just before birth and a concomitant increase in proliferation of glucagon-producing cells. We propose that pdx1 is required for proliferation and function of the beta cells generated at late gestation, and that one function of normal beta cells is to inhibit the proliferation of other islet cell types, resulting in the appropriate numbers of the different endocrine cell types.
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Affiliation(s)
- Maureen Gannon
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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13
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Lees JG, Tuch BE. Conversion of embryonic stem cells into pancreatic beta-cell surrogates guided by ontogeny. Regen Med 2007; 1:327-36. [PMID: 17465786 DOI: 10.2217/17460751.1.3.327] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cellular therapies to treat Type 1 diabetes are being devised and the use of human embryonic stem cells (hESCs) offers a solution to the issue of supply, because hESCs can be maintained in a pluripotent state indefinitely. Furthermore, hESCs have advantages in terms of their plasticity and reduced immunogenicity. Several strategies that have so far been investigated indicate that hESCs are capable of differentiating into insulin producing beta-cell surrogates. However the efficiency of the differentiation procedures used is generally quite low and the cell populations derived are often highly heterogenous. A strategy that appears to have long term potential is to design differentiation procedures based on the ontogeny of the beta-cell. The focus of this strategy is to replicate signaling processes that are known to be involved in the maturation of a beta-cell. The earliest pancreatic progenitors found in the developing vertebrate fetus are produced via a process known as gastrulation and form part of the definitive endoderm germ layer. hESCs have recently been differentiated into definitive endoderm with high efficiency using a differentiation procedure that mimics the signaling that occurs during gastrulation and the formation of the definitive endoderm. Subsequent events during pancreas development involve a section of the definitive endoderm forming into pancreatic epithelium, which then branches into the pancreatic mesenchyme to form islet clusters of endocrine cells. A proportion of the endocrine precursor cells within islets develop into insulin producing beta-cells. The challenge currently is to design hESC differentiation procedures that mimic the combined events of these stages of beta-cell development.
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Affiliation(s)
- Justin G Lees
- Diabetes Transplant Unit, Prince of Wales Hospital/University of New South Wales, Randwick, New South Wales, Australia
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14
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Chen PW, Uno T, Ksander BR. Tumor escape mutants develop within an immune-privileged environment in the absence of T cell selection. THE JOURNAL OF IMMUNOLOGY 2006; 177:162-8. [PMID: 16785511 DOI: 10.4049/jimmunol.177.1.162] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The establishment of tumor escape mutants, which can be driven by innate and/or adaptive immune effector cells, presents a significant obstacle in the development of successful tumor immunotherapies. Our study documents that tumors growing within an immune-privileged site within the eye develop a tumor escape phenotype in the absence of selective T cell pressure. P815 tumor cells that are recovered from progressively growing tumors within the anterior chamber of the eye escape elimination when injected into the flanks of a second group of syngeneic DBA/2 mice that were previously immunized against P815 tumor cells. The escape phenotype of eye-derived P815 tumors was stable and permanent when the tumor cells were cultured in vitro. Eye-derived tumor cells recovered from the anterior chamber of CB-17 SCID mice also escaped elimination when injected into the flanks of immunized mice, demonstrating that selective pressure by tumor Ag-specific T cells did not contribute to the development of the escape phenotype. In vitro studies demonstrated that eye-derived tumor cells were not lysed by specific CTL and were unable to restimulate primed Ag-specific T cells. Immune escape of eye-derived tumor cells was not due to down-regulation of either MHC class I or ICAM-1. Our data demonstrate that the immune-privileged environment within the eye induces a tumor escape phenotype that is not driven by selective T cell pressure. We predict that immune escape within the eye is driven by the unique ocular environment that permanently alters gene expression in eye-derived tumor cells.
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Affiliation(s)
- Peter W Chen
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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15
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Xu Y, Zhang JJ, Grifo JA, Krey LC. DNA methylation patterns in human tripronucleate zygotes. Mol Hum Reprod 2005; 11:167-71. [PMID: 15695773 DOI: 10.1093/molehr/gah145] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In mammals, the dynamic reprogramming of DNA methylation begins during gametogenesis and continues through embryogenesis. Recently, immunofluorescence staining with an antibody against 5-methylcytosine (anti-5-MeC) has revealed active demethylation of the male pronucleus in zygotes beginning at 4-6 h after fertilization. In this study, we characterized the DNA methylation patterns in mouse zygotes and in human tripronucleate (3 PN) zygotes discarded after conventional fertilization or following ICSI. Pronuclei were subjected to fluorescence in-situ hybridization to identify the X and/or Y chromosomes and then stained with anti-5-MeC. In diandric 3 PN zygotes from conventional IVF, we consistently observed one strongly and two weakly stained pronuclei. In contrast, the majority of 3 PN ICSI zygotes, mainly digynic zygotes, displayed two strongly and one weakly stained pronuclei. Two zygotes from ICSI failed to show any staining difference among the three pronuclei. Our results indicate that the active demethylation of male pronuclei occurs in both mouse and human zygotes. It is possible that the abnormal methylation patterns resulting from a dysfunctional cytoplasm may occur in a small number of oocytes and may affect embryonic viability.
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MESH Headings
- Animals
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Cell Nucleus/ultrastructure
- Chromosomes, Human, X/chemistry
- Chromosomes, Human, X/genetics
- Chromosomes, Human, X/metabolism
- Chromosomes, Human, Y/chemistry
- Chromosomes, Human, Y/genetics
- Chromosomes, Human, Y/metabolism
- DNA/analysis
- DNA/genetics
- DNA/metabolism
- DNA Methylation
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Female
- Fertilization/genetics
- Humans
- In Situ Hybridization, Fluorescence
- Male
- Mice
- Mice, Inbred Strains
- Sperm Injections, Intracytoplasmic
- Zygote/chemistry
- Zygote/cytology
- Zygote/metabolism
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Affiliation(s)
- Yanwen Xu
- Program for In Vitro Fertilization, Reproductive Surgery and Infertility, New York University School of Medicine, New York, NY 10016, USA
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16
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Abstract
Type 1 diabetes is one of the more costly chronic diseases of children and adolescents throughout North America and Europe, exhibiting an average estimated prevalence rate of nearly 0.2%. It occurs in genetically predisposed individuals when the immune system attacks and destroys specifically the insulin-producing beta cells of the pancreatic islets of Langerhans. While routine insulin therapy can provide diabetic patients with their daily insulin requirements, non-compliance and undetected hyperglycemic excursions often lead to subsequent long-term microvascular and macrovascular complications. The only real cure for type 1 diabetes is replacement of the beta cell mass, currently being accomplished through ecto-pancreatic transplantation and islet implantation. Both of these procedures suffer from a chronic shortage of available donor tissue in comparison to the number of potential recipients. To circumvent this need, three alternative approaches are being intensively investigated: (1) the production of surrogate cells by genetically modifying non-endocrine cells to secrete insulin in response to glucose challenge; (2) the trans-differentiation of non-endocrine stem/progenitor cells or mature cells to glucose-responsive adult tissue; and (3) the regulated differentiation of islet stem/progenitor cells to produce large numbers of mature, functional islets. In recent years, each of these approaches has made impressive advances, leading to the most important question, 'how soon will this new science be available to the patient?' In the present review, we discuss some of the recent advances, focusing primarily on the differentiation of islet stem cells to functional endocrine pancreas that may form the basis for future treatment.
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Affiliation(s)
- Ammon B Peck
- Department of Pathology, Immumology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville 32610, USA.
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17
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Abstract
The intensity of research on pancreatic development has increased markedly in the past 5 years, primarily for two reasons: we now know that the insulin-producing beta-cells normally arise from an endodermally derived, pancreas-specified precursor cell, and successful transplants of islet cells have been performed, relieving patients with type I diabetes of symptoms for extended periods after transplantation. Combining in vitro beta-cell formation from a pancreatic biopsy of a diabetic patient or from other stem-cell sources followed by endocrine cell transplantation may be the most beneficial route for a future diabetes therapy. However, to achieve this, a thorough understanding of the genetic components regulating the development of beta-cells is required. The following review discusses our current understanding of the transcription factor networks necessary for pancreatic development and how several genetic interactions coming into play at the earliest stages of endodermal development gradually help to build the pancreatic organ. Developmental Dynamics 229:176-200, 2004.
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Affiliation(s)
- Jan Jensen
- Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, Denver, Colorado, USA.
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18
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Doyle MJ, Sussel L. Engineering islets: lessons from stem cells and embryonic development. Endocrinol Metab Clin North Am 2004; 33:149-62, x. [PMID: 15053900 DOI: 10.1016/s0889-8529(03)00100-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Michelle J Doyle
- Departments of Pediatrics and Cellular and Developmental Biology, Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, 4200 East 9th Avenue, Box B140, Denver, CO 80262, USA
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19
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Cross M, Kieft R, Sabatini R, Dirks-Mulder A, Chaves I, Borst P. J-binding protein increases the level and retention of the unusual base J in trypanosome DNA. Mol Microbiol 2002; 46:37-47. [PMID: 12366829 DOI: 10.1046/j.1365-2958.2002.03144.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nuclear DNA of Trypanosoma brucei and other kinetoplastid flagellates contains the unusual base beta-d-glucosyl-hydroxymethyluracil, called J, replacing part of the thymine in repetitive sequences. We have described a 100 kDa protein that specifically binds to J in duplex DNA. We have now disrupted the genes for this J-binding protein (JBP) in T. brucei. The disruption does not affect growth, gene expression or the stability of some repetitive DNA sequences. Unexpectedly, however, the JBP KO trypanosomes contain only about 5% of the wild-type level of J in their DNA. Excess J, randomly introduced into T. brucei DNA by growing the cells in the presence of the J precursor 5-hydroxymethyldeoxyuridine, is lost by simple dilution as the KO trypanosomes multiply, showing that JBP does not protect J against removal. In contrast, cells containing JBP lose excess J only sluggishly. We conclude that JBP is able to activate the thymine modification enzymes to introduce additional J in regions of DNA already containing a basal level of J. We propose that JBP is a novel DNA modification maintenance protein.
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Affiliation(s)
- Mike Cross
- The Netherlands Cancer Institute, Division of Molecular Biology and Center for Biomedical Genetics, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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20
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Coffee B, Zhang F, Ceman S, Warren ST, Reines D. Histone modifications depict an aberrantly heterochromatinized FMR1 gene in fragile x syndrome. Am J Hum Genet 2002; 71:923-32. [PMID: 12232854 PMCID: PMC378545 DOI: 10.1086/342931] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2002] [Accepted: 07/15/2002] [Indexed: 11/04/2022] Open
Abstract
Fragile X syndrome is caused by an expansion of a polymorphic CGG triplet repeat that results in silencing of FMR1 expression. This expansion triggers methylation of FMR1's CpG island, hypoacetylation of associated histones, and chromatin condensation, all characteristics of a transcriptionally inactive gene. Here, we show that there is a graded spectrum of histone H4 acetylation that is proportional to CGG repeat length and that correlates with responsiveness of the gene to DNA demethylation but not with chromatin condensation. We also identify alterations in patient cells of two recently identified histone H3 modifications: methylation of histone H3 at lysine 4 and methylation of histone H3 at lysine 9, which are marks for euchromatin and heterochromatin, respectively. In fragile X cells, there is a decrease in methylation of histone H3 at lysine 4 with a large increase in methylation at lysine 9, a change that is consistent with the model of FMR1's switch from euchromatin to heterochromatin in the disease state. The high level of histone H3 methylation at lysine 9 may account for the failure of H3 to be acetylated after treatment of fragile X cells with inhibitors of histone deacetylases, a treatment that fully restores acetylation to histone H4. Using 5-aza-2'-deoxycytidine, we show that DNA methylation is tightly coupled to the histone modifications associated with euchromatin but not to the heterochromatic mark of methylation of histone H3 at lysine 9, consistent with recent findings that this histone modification may direct DNA methylation. Despite the drug-induced accumulation of mRNA in patient cells to 35% of the wild-type level, FMR1 protein remained undetectable. The identification of intermediates in the heterochromatinization of FMR1 has enabled us to begin to dissect the epigenetics of silencing of a disease-related gene in its natural chromosomal context.
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Affiliation(s)
- Bradford Coffee
- Department of Biochemistry, Department of Human Genetics, and Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta
| | - Fuping Zhang
- Department of Biochemistry, Department of Human Genetics, and Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta
| | - Stephanie Ceman
- Department of Biochemistry, Department of Human Genetics, and Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta
| | - Stephen T. Warren
- Department of Biochemistry, Department of Human Genetics, and Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta
| | - Daniel Reines
- Department of Biochemistry, Department of Human Genetics, and Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta
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21
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Lee DU, Agarwal S, Rao A. Th2 lineage commitment and efficient IL-4 production involves extended demethylation of the IL-4 gene. Immunity 2002; 16:649-60. [PMID: 12049717 DOI: 10.1016/s1074-7613(02)00314-x] [Citation(s) in RCA: 239] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The relation of CpG methylation to gene silencing is well established, but the contribution of DNA demethylation to gene expression during cell differentiation remains unclear. We show that the IL-4 locus undergoes a complex series of methylation and demethylation steps during T helper cell differentiation. The 5' region of the IL-4 locus is hypermethylated in naive T cells and becomes specifically demethylated in Th2 cells, whereas a highly conserved DNase I-hypersensitive region at the 3' end shows the converse behavior, being hypomethylated in naive T cells and becoming methylated during Th1 differentiation. 5' demethylation is not required for chromatin remodeling or primary transcription of the IL-4 gene but is strongly associated with efficient, high-level induction of IL-4 transcripts by differentiated Th2 cells.
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Affiliation(s)
- Dong U Lee
- Department of Pathology, Harvard Medical School and The Center for Blood Research, Boston, MA 02115, USA
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22
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Abstract
We used cyclization kinetics experiments and Monte Carlo simulations to determine a structural model for a DNA decamer containing the EcoRI restriction site. Our findings agree well with recent crystal and NMR structures of the EcoRI dodecamer, where an overall bend of seven degrees is distributed symmetrically over the molecule. Monte Carlo simulations indicate that the sequence has a higher flexibility, assumed to be isotropic, compared to that of a "generic" DNA sequence. This model was used as a starting point for the investigation of the effect of cytosine methylation on DNA bending and flexibility. While methylation did not affect bend magnitude or direction, it resulted in a reduction in bending flexibility and under-winding of the methylated nucleotides. We demonstrate that our approach can augment the understanding of DNA structure and dynamics by adding information about the global structure and flexibility of the sequence. We also show that cyclization kinetics can be used to study the properties of modified nucleotides.
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Affiliation(s)
- Dafna Nathan
- Departments of Chemistry, Yale University, New Haven, CT 06520, USA
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23
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Takizawa T, Nakashima K, Namihira M, Ochiai W, Uemura A, Yanagisawa M, Fujita N, Nakao M, Taga T. DNA methylation is a critical cell-intrinsic determinant of astrocyte differentiation in the fetal brain. Dev Cell 2001; 1:749-58. [PMID: 11740937 DOI: 10.1016/s1534-5807(01)00101-0] [Citation(s) in RCA: 444] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Astrocyte differentiation, which occurs late in brain development, is largely dependent on the activation of a transcription factor, STAT3. We show that astrocytes, as judged by glial fibrillary acidic protein (GFAP) expression, never emerge from neuroepithelial cells on embryonic day (E) 11.5 even when STAT3 is activated, in contrast to E14.5 neuroepithelial cells. A CpG dinucleotide within a STAT3 binding element in the GFAP promoter is highly methylated in E11.5 neuroepithelial cells, but is demethylated in cells responsive to the STAT3 activation signal to express GFAP. This CpG methylation leads to inaccessibility of STAT3 to the binding element. We suggest that methylation of a cell type-specific gene promoter is a pivotal event in regulating lineage specification in the developing brain.
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Affiliation(s)
- T Takizawa
- Department of Cell Fate Modulation, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan
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24
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Du SJ, Dienhart M. Zebrafish tiggy-winkle hedgehog promoter directs notochord and floor plate green fluorescence protein expression in transgenic zebrafish embryos. Dev Dyn 2001; 222:655-66. [PMID: 11748834 DOI: 10.1002/dvdy.1219] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Zebrafish tiggy-winkle hedgehog (twhh) is a member of the hedgehog gene family that plays an important role in patterning brain, neural tube, somites, and eyes. To better understand the regulation of its tissue-specific expression, the activity of the twhh promoter was determined in zebrafish embryos by transient and transgenic expression analysis. Transient expression studies revealed that the 5.2-kb twhh promoter drove green fluorescence protein (GFP) expression in the notochord, floor plate, and branchial arches. Deletion analysis showed that distinct regions of the twhh promoter regulated the respective notochord or floor plate specific expression. To confirm the tissue specificity of the twhh promoter, transgenic zebrafish containing the twhh-GFP transgene were generated. GFP expression was analyzed in the F1, F2, and F3 generations of the transgenic embryos. The results confirmed the tissue-specific expression of the transgene in the notochord, floor plate, and branchial arches. In addition, GFP expression was also found in the pectoral fin buds, retina, and epithelial lining cells of the Kupffer's vesicle in the transgenic fish embryos. The expression pattern of the twhh-GFP transgene mimicked the expression of the endogenous twhh mRNAs in the floor plate, fin buds, branchial arches, retina, and epithelial lining cells of the Kupffer's vesicle. The expression in the notochord, however, did not mimic the pattern of the endogenous twhh expression. To determine whether no tail (ntl) or floating head (flh) mutants that have developmental defect in the notochord or the Kupffer's vesicle may affect the GFP expression in these regions, GFP expression was analyzed in ntl or flh transgenic embryos. No GFP expression could be detected in the midline region of the ntl transgenic embryos. However, in flh transgenic embryos, although GFP expression was affected in the midline region, its expression in the Kupffer's vesicle appeared normal. Together, these data indicated that the 5.2-kb twhh promoter contains regulatory elements for tissue-specific expression of twhh in the floor plate, pectoral fin bud, branchial arches, retina, and Kupffer's vesicle.
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Affiliation(s)
- S J Du
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore 21202, USA.
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25
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Fang JY, Mikovits JA, Bagni R, Petrow-Sadowski CL, Ruscetti FW. Infection of lymphoid cells by integration-defective human immunodeficiency virus type 1 increases de novo methylation. J Virol 2001; 75:9753-61. [PMID: 11559808 PMCID: PMC114547 DOI: 10.1128/jvi.75.20.9753-9761.2001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
DNA methylation, by regulating the transcription of genes, is a major modifier of the eukaryotic genome. DNA methyltransferases (DNMTs) are responsible for both maintenance and de novo methylation. We have reported that human immunodeficiency virus type 1 (HIV-1) infection increases DNMT1 expression and de novo methylation of genes such as the gamma interferon gene in CD4(+) cells. Here, we examined the mechanism(s) by which HIV-1 infection increases the cellular capacity to methylate genes. While the RNAs and proteins of all three DNMTs (1, 3a, and 3b) were detected in Hut 78 lymphoid cells, only the expression of DNMT1 was significantly increased 3 to 5 days postinfection. This increase was observed with either wild-type HIV-1 or an integrase (IN) mutant, which renders HIV replication defective, due to the inability of the provirus to integrate into the host genome. Unintegrated viral DNA is a common feature of many retroviral infections and is thought to play a role in pathogenesis. These results indicate another mechanism by which unintegrated viral DNA affects the host. In addition to the increase in overall genomic methylation, hypermethylation and reduced expression of the p16(INK4A) gene, one of the most commonly altered genes in human cancer, were seen in cells infected with both wild-type and IN-defective HIV-1. Thus, infection of lymphoid cells with integration-defective HIV-1 can increase the methylation of CpG islands in the promoters of genes such as the p16(INK4A) gene, silencing their expression.
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Affiliation(s)
- J Y Fang
- Basic Research Laboratory, CCR, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA
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26
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Peng H, Shen N, Qian L, Sun XL, Koduru P, Goodwin LO, Issa JP, Broome JD. Hypermethylation of CpG islands in the mouse asparagine synthetase gene: relationship to asparaginase sensitivity in lymphoma cells. Partial methylation in normal cells. Br J Cancer 2001; 85:930-5. [PMID: 11556848 PMCID: PMC2375082 DOI: 10.1054/bjoc.2001.2000] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have sequenced the promoter region of the murine asparagine synthetase gene and examined its methylation profile in the CpG islands of L-asparaginase-sensitive 6C3HED cells (asparagine auxotrophs) and resistant variants (prototrophs). In the former, complete methylation of the CpG island is correlated with failure of expression of mRNA: cells of the latter possess both methylated and unmethylated alleles, as do cells of the intrinsically asparagine-independent lines L1210 and EL4. A similar phenomenon was seen in normal splenic cells of adult mice. This was age related: no methylation was found in weanlings, but up to 45% of gene copies in animals 18 weeks or older were methylated. It was also tissue related, with methylation occurring rarely in liver cells. The relationship of these changes to oncogenesis is considered.
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Affiliation(s)
- H Peng
- Department of Pathology, North Shore University Hospital, Manhasset, NY 11030, USA
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27
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Gowher H, Jeltsch A. Enzymatic properties of recombinant Dnmt3a DNA methyltransferase from mouse: the enzyme modifies DNA in a non-processive manner and also methylates non-CpG [correction of non-CpA] sites. J Mol Biol 2001; 309:1201-8. [PMID: 11399089 DOI: 10.1006/jmbi.2001.4710] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We present the first in vitro study investigating the catalytic properties of a mammalian de novo DNA methyltransferase. Dnmt3a from mouse was cloned and expressed in Escherichia coli. It was shown to be catalytically active in E. coli cells in vivo. The methylation activity of the purified protein was highest at pH 7.0 and 30 mM KCl. Our data show that recombinant Dnmt3a protein is indeed a de novo methyltransferase, as it catalyzes the transfer of methyl groups to unmethylated substrates with similar efficiency as to hemimethylated substrates. With oligonucleotide substrates, the catalytic activity of Dnmt3a is similar to that of Dnmt1: the K(m) values for the unmethylated and hemimethylated oligonucleotide substrates are 2.5 microM, and the k(cat) values are 0.05 h(-1) and 0.07 h(-1), respectively. The enzyme catalyzes the methylation of DNA in a distributive manner, suggesting that Dnmt3a and Dnmt1 may cooperate during de novo methylation of DNA. Further, we investigated the methylation activity of Dnmt3a at non-canonical sites. Even though the enzyme shows maximum activity at CpG sites, with oligonucleotide substrates, a high methylation activity was also found at CpA sites, which are modified only twofold slower than CpG sites. Therefore, the specificity of Dnmt3a is completely different from that of the maintenance methyltransferase Dnmt1, which shows a 40 to 50-fold preference for hemimethylated over unmethylated CpG sites and has almost no methylation activity at non-CpG sites.
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Affiliation(s)
- H Gowher
- Institut für Biochemie Fachbereich 8, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, Giessen, 35392, Germany
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28
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Tenenhaus C, Subramaniam K, Dunn MA, Seydoux G. PIE-1 is a bifunctional protein that regulates maternal and zygotic gene expression in the embryonic germ line of Caenorhabditis elegans. Genes Dev 2001; 15:1031-40. [PMID: 11316796 PMCID: PMC312670 DOI: 10.1101/gad.876201] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2000] [Accepted: 02/12/2001] [Indexed: 11/25/2022]
Abstract
The CCCH zinc finger protein PIE-1 is an essential regulator of germ cell fate that segregates with the germ lineage during the first cleavages of the Caenorhabditis elegans embryo. We have shown previously that one function of PIE-1 is to inhibit mRNA transcription. Here we show that PIE-1 has a second function in germ cells; it is required for efficient expression of the maternally encoded Nanos homolog NOS-2. This second function is genetically separable from PIE-1's inhibitory effect on transcription. A mutation in PIE-1's second CCCH finger reduces NOS-2 expression without affecting transcriptional repression and causes primordial germ cells to stray away from the somatic gonad, occasionally exiting the embryo entirely. Our results indicate that PIE-1 promotes germ cell fate by two independent mechanisms as follows: (1) inhibition of transcription, which blocks zygotic programs that drive somatic development, and (2) activation of protein expression from nos-2 and possibly other maternal RNAs, which promotes primordial germ cell development.
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Affiliation(s)
- C Tenenhaus
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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29
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Vilain A, Bernardino J, Gerbault-Seureau M, Vogt N, Niveleau A, Lefrançois D, Malfoy B, Dutrillaux B. DNA methylation and chromosome instability in lymphoblastoid cell lines. CYTOGENETICS AND CELL GENETICS 2001; 90:93-101. [PMID: 11060456 DOI: 10.1159/000015641] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In order to gain more insight into the relationships between DNA methylation and genome stability, chromosomal and molecular evolutions of four Epstein-Barr virus-transformed human lymphoblastoid cell lines were followed in culture for more than 2 yr. The four cell lines underwent early, strong overall demethylation of the genome. The classical satellite-rich, heterochromatic,juxtacentromeric regions of chromosomes 1, 9, and 16 and the distal part of the long arm of the Y chromosome displayed specific behavior with time in culture. In two cell lines, they underwent a strong demethylation, involving successively chromosomes Y, 9, 16, and 1, whereas in the two other cell lines, they remained heavily methylated. For classical satellite 2-rich heterochromatic regions of chromosomes 1 and 16, a direct relationship could be established between their demethylation, their undercondensation at metaphase, and their involvement in non-clonal rearrangements. Unstable sites distributed along the whole chromosomes were found only when the heterochromatic regions of chromosomes 1 and 16 were unstable. The classical satellite 3-rich heterochromatic region of chromosomes 9 and Y, despite their strong demethylation, remained condensed and stable. Genome demethylation and chromosome instability could not be related to variations in mRNA amounts of the DNA methyltransferases DNMT1, DNMT3A, and DNMT3B and DNA demethylase. These data suggest that the influence of DNA demethylation on chromosome stability is modulated by a sequence-specific chromatin structure.
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Affiliation(s)
- A Vilain
- Institut Curie-CNRS UMR 147, Cytogénétique Moléculaire et Oncologie, Paris, France
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30
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Field LM. Methylation and expression of amplified esterase genes in the aphid Myzus persicae (Sulzer). Biochem J 2000; 349 Pt 3:863-8. [PMID: 10903149 PMCID: PMC1221215 DOI: 10.1042/bj3490863] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Most populations of the aphid Myzus persicae have amplified genes (up to 80 copies) encoding the insecticide-detoxifying esterase E4. This paper reports the analysis of methylation of the E4 gene and its flanking DNA with the use of methylation-sensitive restriction enzymes, CpG profiling and bisulphite sequencing. In combination these show that E4 has 5-methylcytosine confined to CpG doublets, as previously shown for vertebrate genomes; this is the first such report for an insect gene. The methylation is present within the gene but absent from upstream regions, including the 5' CpG-rich region around the start of transcription, and from 3' flanking DNA. Methylated E4 genes are expressed; loss of the 5-methylcytosine is correlated with a loss of transcription, although this is not accompanied by a global loss of the 5-methylcytosine present in the aphid genome. These results suggest that the methylation of E4 has a positive role in expression, and call into question the widely held view that methylation in invertebrate genomes is confined to regions that do not contain genes and that methylation is always associated with gene silencing.
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Affiliation(s)
- L M Field
- IACR-Rothamsted, Harpenden, Herts. AL5 2JQ, U.K.
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31
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Rountree MR, Bachman KE, Baylin SB. DNMT1 binds HDAC2 and a new co-repressor, DMAP1, to form a complex at replication foci. Nat Genet 2000; 25:269-77. [PMID: 10888872 DOI: 10.1038/77023] [Citation(s) in RCA: 762] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
DNA methylation can contribute to transcriptional silencing through several transcriptionally repressive complexes, which include methyl-CpG binding domain proteins (MBDs) and histone deacetylases (HDACs). We show here that the chief enzyme that maintains mammalian DNA methylation, DNMT1, can also establish a repressive transcription complex. The non-catalytic amino terminus of DNMT1 binds to HDAC2 and a new protein, DMAP1 (for DNMT1 associated protein), and can mediate transcriptional repression. DMAP1 has intrinsic transcription repressive activity, and binds to the transcriptional co-repressor TSG101. DMAP1 is targeted to replication foci through interaction with the far N terminus of DNMT1 throughout S phase, whereas HDAC2 joins DNMT1 and DMAP1 only during late S phase, providing a platform for how histones may become deacetylated in heterochromatin following replication. Thus, DNMT1 not only maintains DNA methylation, but also may directly target, in a heritable manner, transcriptionally repressive chromatin to the genome during DNA replication.
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Affiliation(s)
- M R Rountree
- The Johns Hopkins Oncology Center, Tumor Biology Laboratory, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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32
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Cohen-Tannoudji M, Babinet C, Morello D. lacZ and ubiquitously expressed genes: should divorce be pronounced? Transgenic Res 2000; 9:233-5. [PMID: 11032373 DOI: 10.1023/a:1008916910392] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- M Cohen-Tannoudji
- Unité de Biologie du Développement, CNRS URA 1960, Institut Pasteur, Paris, France
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