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Ramos-Rodríguez M, Subirana-Granés M, Norris R, Sordi V, Fernández Á, Fuentes-Páez G, Pérez-González B, Berenguer Balaguer C, Raurell-Vila H, Chowdhury M, Corripio R, Partelli S, López-Bigas N, Pellegrini S, Montanya E, Nacher M, Falconi M, Layer R, Rovira M, González-Pérez A, Piemonti L, Pasquali L. Implications of noncoding regulatory functions in the development of insulinomas. CELL GENOMICS 2024:100604. [PMID: 38959898 DOI: 10.1016/j.xgen.2024.100604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 04/22/2024] [Accepted: 06/11/2024] [Indexed: 07/05/2024]
Abstract
Insulinomas are rare neuroendocrine tumors arising from pancreatic β cells, characterized by aberrant proliferation and altered insulin secretion, leading to glucose homeostasis failure. With the aim of uncovering the role of noncoding regulatory regions and their aberrations in the development of these tumors, we coupled epigenetic and transcriptome profiling with whole-genome sequencing. As a result, we unraveled somatic mutations associated with changes in regulatory functions. Critically, these regions impact insulin secretion, tumor development, and epigenetic modifying genes, including polycomb complex components. Chromatin remodeling is apparent in insulinoma-selective domains shared across patients, containing a specific set of regulatory sequences dominated by the SOX17 binding motif. Moreover, many of these regions are H3K27me3 repressed in β cells, suggesting that tumoral transition involves derepression of polycomb-targeted domains. Our work provides a compendium of aberrant cis-regulatory elements affecting the function and fate of β cells in their progression to insulinomas and a framework to identify coding and noncoding driver mutations.
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Affiliation(s)
- Mireia Ramos-Rodríguez
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Marc Subirana-Granés
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Richard Norris
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Valeria Sordi
- Diabetes Research Institute (DRI) - IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Ángel Fernández
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain; Department of Physiological Science, School of Medicine, Universitat de Barcelona (UB), L'Hospitalet de Llobregat, Barcelona, Spain; Pancreas Regeneration: Pancreatic Progenitors and Their Niche Group, Regenerative Medicine Program, Institut d'Investigació Biomèdica de Bellvitge - IDIBELL, L'Hospitalet de Llobregat, Barcelona, Spain; Program for Advancing the Clinical Translation of Regenerative Medicine of Catalonia, P-CMR[C], L'Hospitalet de Llobregat, Barcelona, Spain
| | - Georgina Fuentes-Páez
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Beatriz Pérez-González
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Clara Berenguer Balaguer
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Helena Raurell-Vila
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Murad Chowdhury
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA
| | - Raquel Corripio
- Paediatric Endocrinology Department, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Spain
| | - Stefano Partelli
- Pancreas Translational & Research Institute, Scientific Institute San Raffaele Hospital and University Vita-Salute, Milan, Italy
| | - Núria López-Bigas
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Research Program on Biomedical Informatics, Universitat Pompeu Fabra, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Silvia Pellegrini
- Diabetes Research Institute (DRI) - IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Eduard Montanya
- Bellvitge Hospital-IDIBELL, Barcelona, Spain; Department of Clinical Sciences, University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | - Montserrat Nacher
- Bellvitge Hospital-IDIBELL, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | - Massimo Falconi
- Pancreas Translational & Research Institute, Scientific Institute San Raffaele Hospital and University Vita-Salute, Milan, Italy
| | - Ryan Layer
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA; Department of Computer Science, University of Colorado Boulder, Boulder, CO, USA
| | - Meritxell Rovira
- Department of Physiological Science, School of Medicine, Universitat de Barcelona (UB), L'Hospitalet de Llobregat, Barcelona, Spain; Pancreas Regeneration: Pancreatic Progenitors and Their Niche Group, Regenerative Medicine Program, Institut d'Investigació Biomèdica de Bellvitge - IDIBELL, L'Hospitalet de Llobregat, Barcelona, Spain; Program for Advancing the Clinical Translation of Regenerative Medicine of Catalonia, P-CMR[C], L'Hospitalet de Llobregat, Barcelona, Spain
| | - Abel González-Pérez
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Research Program on Biomedical Informatics, Universitat Pompeu Fabra, Barcelona, Spain
| | - Lorenzo Piemonti
- Diabetes Research Institute (DRI) - IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Lorenzo Pasquali
- Endocrine Regulatory Genomics, Department of Medicine and Life Sciences, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain.
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Haberman N, Cheung R, Pizza G, Cvetesic N, Nagy D, Maude H, Blazquez L, Lenhard B, Cebola I, Rutter GA, Martinez-Sanchez A. Liver kinase B1 (LKB1) regulates the epigenetic landscape of mouse pancreatic beta cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.593867. [PMID: 38798508 PMCID: PMC11118353 DOI: 10.1101/2024.05.13.593867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Liver kinase B1 (LKB1/STK11) is an important regulator of pancreatic β-cell identity and function. Elimination of Lkb1 from the β-cell results in improved glucose-stimulated insulin secretion and is accompanied by profound changes in gene expression, including the upregulation of several neuronal genes. The mechanisms through which LKB1 controls gene expression are, at present, poorly understood. Here, we explore the impact of β cell- selective deletion of Lkb1 on chromatin accessibility in mouse pancreatic islets. To characterize the role of LKB1 in the regulation of gene expression at the transcriptional level, we combine these data with a map of islet active transcription start sites and histone marks. We demonstrate that LKB1 elimination from β-cells results in widespread changes in chromatin accessibility, correlating with changes in transcript levels. Changes occurred in hundreds of promoter and enhancer regions, many of which were close to neuronal genes. We reveal that dysregulated enhancers are enriched in binding motifs for transcription factors important for β-cell identity, such as FOXA, MAFA or RFX6 and we identify microRNAs (miRNAs) that are regulated by LKB1 at the transcriptional level. Overall, our study provides important new insights into the epigenetic mechanisms by which LKB1 regulates β-cell identity and function.
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Rath S, Hawsawi YM, Alzahrani F, Khan MI. Epigenetic regulation of inflammation: The metabolomics connection. Semin Cell Dev Biol 2024; 154:355-363. [PMID: 36127262 DOI: 10.1016/j.semcdb.2022.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 10/14/2022]
Abstract
Epigenetic factors are considered the regulator of complex machinery behind inflammatory disorders and significantly contributed to the expression of inflammation-associated genes. Epigenetic modifications modulate variation in the expression pattern of target genes without affecting the DNA sequence. The current knowledge of epigenetic research focused on their role in the pathogenesis of various inflammatory diseases that causes morbidity and mortality worldwide. Inflammatory diseases are categorized as acute and chronic based on the disease severity and are regulated by the expression pattern of various genes. Hence, understanding the role of epigenetic modifications during inflammation progression will contribute to the disease outcomes and therapeutic approaches. This review also focuses on the metabolomics approach associated with the study of inflammatory disorders. Inflammatory responses and metabolic regulation are highly integrated and various advanced techniques are adopted to study the metabolic signature molecules. Here we discuss several metabolomics approaches used to link inflammatory disorders and epigenetic changes. We proposed that deciphering the mechanism behind the inflammation-metabolism loop may have immense importance in biomarkers research and may act as a principal component in drug discovery as well as therapeutic applications.
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Affiliation(s)
- Suvasmita Rath
- Center of Environment, Climate Change and Public Health, Utkal University, Vani Vihar, Bhubaneswar 751004, Odisha, India
| | - Yousef M Hawsawi
- Research Center, King Faisal Specialist Hospital and Research Center, P.O. Box 40047, Jeddah 21499, Saudi Arabia; College of Medicine, Al-Faisal University, P.O. Box 50927, Riyadh 11533, Saudi Arabia.
| | - Faisal Alzahrani
- Department of Biochemistry, King Abdulaziz University (KAU), Jeddah 21577, Saudi Arabia; Embryonic Stem Cells Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Mohammad Imran Khan
- Department of Biochemistry, King Abdulaziz University (KAU), Jeddah 21577, Saudi Arabia; Centre of Artificial Intelligence for Precision Medicines, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
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Mawla AM, van der Meulen T, Huising MO. Chromatin accessibility differences between alpha, beta, and delta cells identifies common and cell type-specific enhancers. BMC Genomics 2023; 24:202. [PMID: 37069576 PMCID: PMC10108528 DOI: 10.1186/s12864-023-09293-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 04/03/2023] [Indexed: 04/19/2023] Open
Abstract
BACKGROUND High throughput sequencing has enabled the interrogation of the transcriptomic landscape of glucagon-secreting alpha cells, insulin-secreting beta cells, and somatostatin-secreting delta cells. These approaches have furthered our understanding of expression patterns that define healthy or diseased islet cell types and helped explicate some of the intricacies between major islet cell crosstalk and glucose regulation. All three endocrine cell types derive from a common pancreatic progenitor, yet alpha and beta cells have partially opposing functions, and delta cells modulate and control insulin and glucagon release. While gene expression signatures that define and maintain cellular identity have been widely explored, the underlying epigenetic components are incompletely characterized and understood. However, chromatin accessibility and remodeling is a dynamic attribute that plays a critical role to determine and maintain cellular identity. RESULTS Here, we compare and contrast the chromatin landscape between mouse alpha, beta, and delta cells using ATAC-Seq to evaluate the significant differences in chromatin accessibility. The similarities and differences in chromatin accessibility between these related islet endocrine cells help define their fate in support of their distinct functional roles. We identify patterns that suggest that both alpha and delta cells are poised, but repressed, from becoming beta-like. We also identify patterns in differentially enriched chromatin that have transcription factor motifs preferentially associated with different regions of the genome. Finally, we not only confirm and visualize previously discovered common endocrine- and cell specific- enhancer regions across differentially enriched chromatin, but identify novel regions as well. We compiled our chromatin accessibility data in a freely accessible database of common endocrine- and cell specific-enhancer regions that can be navigated with minimal bioinformatics expertise. CONCLUSIONS Both alpha and delta cells appear poised, but repressed, from becoming beta cells in murine pancreatic islets. These data broadly support earlier findings on the plasticity in identity of non-beta cells under certain circumstances. Furthermore, differential chromatin accessibility shows preferentially enriched distal-intergenic regions in beta cells, when compared to either alpha or delta cells.
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Affiliation(s)
- Alex M Mawla
- Department of Neurobiology, Physiology & Behavior, College of Biological Sciences, University of California, One Shields Avenue, Davis, CA, 95616, USA
| | - Talitha van der Meulen
- Department of Neurobiology, Physiology & Behavior, College of Biological Sciences, University of California, One Shields Avenue, Davis, CA, 95616, USA
| | - Mark O Huising
- Department of Neurobiology, Physiology & Behavior, College of Biological Sciences, University of California, One Shields Avenue, Davis, CA, 95616, USA.
- Department of Physiology and Membrane Biology, School of Medicine, University of California, One Shields Avenue, Davis, CA, 95616, USA.
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Jiang C, Hu Y, Wang S, Chen C. Emerging trends in DNA and RNA methylation modifications in type 2 diabetes mellitus: a bibliometric and visual analysis from 1992 to 2022. Front Endocrinol (Lausanne) 2023; 14:1145067. [PMID: 37201099 PMCID: PMC10187586 DOI: 10.3389/fendo.2023.1145067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 03/30/2023] [Indexed: 05/20/2023] Open
Abstract
Background Type 2 diabetes mellitus (T2DM) is a pathological metabolic disorder induced by the interaction of genetic and environmental factors. Epigenetic modifications, especially DNA and RNA methylation, might be the bridge between hereditary and environmental factors. This study aimed to comprehensively analyze the status and prospective trends of the association between T2DM and DNA/RNA methylation modifications by using bibliometric software. Methods All the publications in the Web of Science database for the research of T2DM with DNA and RNA methylation modifications were obtained from the earliest mention to December 2022. CiteSpace software was used to analyze countries, institutions, journals/cited-references, authors/cited-authors, and keywords. Results of the comprehensive visualization and bibliometric analysis were displayed relative to the research hotspots and knowledge structure. Results A total of 1,233 publications related to DNA and RNA methylation modifications and T2DM were collected. The number of publications per year and the overall trend consistently and significantly increased during the investigation period. Based on the highest publication counts, the most influential country was the USA, while Lund University was the most productive institution. DIABETES was considered the most popular journal. The most frequent keywords identified in the field of methylation and T2DM were mainly involved in developmental origin, insulin resistance, and metabolism. The study suggested that the study of methylation modifications had an increasingly significant role in understanding the progression of T2DM. Conclusion CiteSpace visualization software was utilized to investigate the status and trends of DNA and RNA methylation modifications in the pathology of T2DM over the past 30 years. Findings from the study provide a guiding perspective for researchers regarding future research directions in this field.
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Affiliation(s)
- Cai Jiang
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, China
| | - Yue Hu
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, China
| | - Sinuo Wang
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, China
| | - Cong Chen
- Rehabilitation Industry Institute, Fujian University of Traditional Chinese Medicine, Fuzhou, China
- National-Local Joint Engineering Research Center of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, China
- *Correspondence: Cong Chen,
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Liu J, Liu S, Yu Z, Qiu X, Jiang R, Li W. Uncovering the gene regulatory network of type 2 diabetes through multi-omic data integration. J Transl Med 2022; 20:604. [PMID: 36527108 PMCID: PMC9756634 DOI: 10.1186/s12967-022-03826-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Type 2 diabetes (T2D) onset is a complex, organized biological process with multilevel regulation, and its physiopathological mechanisms are yet to be elucidated. This study aims to find out the key drivers and pathways involved in the pathogenesis of T2D through multi-omics analysis. METHODS The datasets used in the experiments comprise three groups: (1) genomic (2) transcriptomic, and (3) epigenomic categories. Then, a series of bioinformatics technologies including Marker set enrichment analysis (MSEA), weighted key driver analysis (wKDA) was performed to identify key drivers. The hub genes were further verified by the Receiver Operator Characteristic (ROC) Curve analysis, proteomic analysis, and Real-time quantitative polymerase chain reaction (RT-qPCR). The multi-omics network was applied to the Pharmomics pipeline in Mergeomics to identify drug candidates for T2D treatment. Then, we used the drug-gene interaction network to conduct network pharmacological analysis. Besides, molecular docking was performed using AutoDock/Vina, a computational docking program. RESULTS Module-gene interaction network was constructed using MSEA, which revealed a significant enrichment of immune-related activities and glucose metabolism. Top 10 key drivers (PSMB9, COL1A1, COL4A1, HLA-DQB1, COL3A1, IRF7, COL5A1, CD74, HLA-DQA1, and HLA-DRB1) were selected by wKDA analysis. Among these, COL5A1, IRF7, CD74, and HLA-DRB1 were verified to have the capability to diagnose T2D, and expression levels of PSMB9 and CD74 had significantly higher in T2D patients. We further predict the co-expression network and transcription factor (TF) binding specificity of the key driver. Besides, based on module interaction networks and key driver networks, 17 compounds are considered to possess T2D-control potential, such as sunitinib. CONCLUSIONS We identified signature genes, biomolecular processes, and pathways using multi-omics networks. Moreover, our computational network analysis revealed potential novel strategies for pharmacologic interventions of T2D.
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Affiliation(s)
- Jiachen Liu
- Department of General Surgery, Third Xiangya Hospital Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
- Xiangya Medical College, Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
- The Center of Systems Biology and Data science, School of Basic Medical Science, Central South University, Changsha, Hunan, People's Republic of China
| | - Shenghua Liu
- Department of General Surgery, Third Xiangya Hospital Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
- Xiangya Medical College, Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
| | - Zhaomei Yu
- Department of Thyroid and Breast Surgery, The Frist Afflicted Hospital of Fujian Medical University, No. 20 Chayzhong Road, Taijiang District, Fuzhou, 350005, Fujian, People's Republic of China
| | - Xiaorui Qiu
- Xiangya Medical College, Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
| | - Rundong Jiang
- Department of General Surgery, Third Xiangya Hospital Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China
| | - Weizheng Li
- Department of General Surgery, Third Xiangya Hospital Central South University, No. 138 Tongzipo Road Yuelu District, Changsha, 410013, Hunan, People's Republic of China.
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Ni Q, Sun J, Wang Y, Wang Y, Liu J, Ning G, Wang W, Wang Q. mTORC1 is required for epigenetic silencing during β-cell functional maturation. Mol Metab 2022; 64:101559. [PMID: 35940555 PMCID: PMC9418906 DOI: 10.1016/j.molmet.2022.101559] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 11/06/2022] Open
Abstract
Objective The mechanistic target of rapamycin complex 1 (mTORC1) is a key molecule that links nutrients, hormones, and growth factors to cell growth/function. Our previous studies have shown that mTORC1 is required for β-cell functional maturation and identity maintenance; however, the underlying mechanism is not fully understood. This work aimed to understand the underlying epigenetic mechanisms of mTORC1 in regulating β-cell functional maturation. Methods We performed Microarray, MeDIP-seq and ATAC-seq analysis to explore the abnormal epigenetic regulation in 8-week-old immature βRapKO islets. Moreover, DNMT3A was overexpressed in βRapKO islets by lentivirus, and the transcriptome changes and GSIS function were analyzed. Results We identified two major epigenetic silencing mechanisms, DNMT3A-dependent DNA methylation and PRC2-dependent H3K27me3 modification, which are responsible for functional immaturity of Raptor-deficient β-cell. Overexpression of DNMT3A partially reversed the immature transcriptome pattern and restored the impaired GSIS in Raptor-deficient β-cells. Moreover, we found that Raptor directly regulated PRC2/EED and H3K27me3 expression levels, as well as a group of immature genes marked with H3K27me3. Combined with ATAC-seq, MeDIP-seq and ChIP-seq, we identified β-cell immature genes with either DNA methylation and/or H3K27me3 modification. Conclusion The present study advances our understanding of the nutrient sensor mTORC1, by integrating environmental nutrient supply and epigenetic modification, i.e., DNMT3A-mediated DNA methylation and PRC2-mediated histone methylation in regulating β-cell identity and functional maturation, and therefore may impact the disease risk of type 2 diabetes. Rescued DNMT3A expression in Raptor-deficient islets partially reversed the abnormal induction of immature genes. EED/H3K27me3 were impaired in Raptor-ablated β-cell. DNA methylation and H3K27me3 are required for mTORC1-dependent epigenetic silencing of immature genes in β-cell.
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Ling C, Bacos K, Rönn T. Epigenetics of type 2 diabetes mellitus and weight change - a tool for precision medicine? Nat Rev Endocrinol 2022; 18:433-448. [PMID: 35513492 DOI: 10.1038/s41574-022-00671-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/29/2022] [Indexed: 12/12/2022]
Abstract
Pioneering studies performed over the past few decades demonstrate links between epigenetics and type 2 diabetes mellitus (T2DM), the metabolic disorder with the most rapidly increasing prevalence in the world. Importantly, these studies identified epigenetic modifications, including altered DNA methylation, in pancreatic islets, adipose tissue, skeletal muscle and the liver from individuals with T2DM. As non-genetic factors that affect the risk of T2DM, such as obesity, unhealthy diet, physical inactivity, ageing and the intrauterine environment, have been associated with epigenetic modifications in healthy individuals, epigenetics probably also contributes to T2DM development. In addition, genetic factors associated with T2DM and obesity affect the epigenome in human tissues. Notably, causal mediation analyses found DNA methylation to be a potential mediator of genetic associations with metabolic traits and disease. In the past few years, translational studies have identified blood-based epigenetic markers that might be further developed and used for precision medicine to help patients with T2DM receive optimal therapy and to identify patients at risk of complications. This Review focuses on epigenetic mechanisms in the development of T2DM and the regulation of body weight in humans, with a special focus on precision medicine.
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Affiliation(s)
- Charlotte Ling
- Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, Malmö, Sweden.
| | - Karl Bacos
- Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, Malmö, Sweden
| | - Tina Rönn
- Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, Malmö, Sweden
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Kaimala S, Kumar CA, Allouh MZ, Ansari SA, Emerald BS. Epigenetic modifications in pancreas development, diabetes, and therapeutics. Med Res Rev 2022; 42:1343-1371. [PMID: 34984701 PMCID: PMC9306699 DOI: 10.1002/med.21878] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 11/24/2021] [Accepted: 12/18/2021] [Indexed: 12/26/2022]
Abstract
A recent International Diabetes Federation report suggests that more than 463 million people between 20 and 79 years have diabetes. Of the 20 million women affected by hyperglycemia during pregnancy, 84% have gestational diabetes. In addition, more than 1.1 million children or adolescents are affected by type 1 diabetes. Factors contributing to the increase in diabetes prevalence are complex and include contributions from genetic, environmental, and epigenetic factors. However, molecular regulatory mechanisms influencing the progression of an individual towards increased susceptibility to metabolic diseases such as diabetes are not fully understood. Recent studies suggest that the pathogenesis of diabetes involves epigenetic changes, resulting in a persistently dysregulated metabolic phenotype. This review summarizes the role of epigenetic mechanisms, mainly DNA methylation and histone modifications, in the development of the pancreas, their contribution to the development of diabetes, and the potential employment of epigenetic modulators in diabetes treatment.
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Affiliation(s)
- Suneesh Kaimala
- Department of Anatomy, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
| | - Challagandla Anil Kumar
- Department of Anatomy, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
| | - Mohammed Z Allouh
- Department of Anatomy, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
| | - Suraiya Anjum Ansari
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE.,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
| | - Bright Starling Emerald
- Department of Anatomy, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE.,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
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Sun X, Wang L, Obayomi SMB, Wei Z. Epigenetic Regulation of β Cell Identity and Dysfunction. Front Endocrinol (Lausanne) 2021; 12:725131. [PMID: 34630329 PMCID: PMC8498190 DOI: 10.3389/fendo.2021.725131] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 09/08/2021] [Indexed: 01/07/2023] Open
Abstract
β cell dysfunction and failure are driving forces of type 2 diabetes mellitus (T2DM) pathogenesis. Investigating the underlying mechanisms of β cell dysfunction may provide novel targets for the development of next generation therapy for T2DM. Epigenetics is the study of gene expression changes that do not involve DNA sequence changes, including DNA methylation, histone modification, and non-coding RNAs. Specific epigenetic signatures at all levels, including DNA methylation, chromatin accessibility, histone modification, and non-coding RNA, define β cell identity during embryonic development, postnatal maturation, and maintain β cell function at homeostatic states. During progression of T2DM, overnutrition, inflammation, and other types of stress collaboratively disrupt the homeostatic epigenetic signatures in β cells. Dysregulated epigenetic signatures, and the associating transcriptional outputs, lead to the dysfunction and eventual loss of β cells. In this review, we will summarize recent discoveries of the establishment and disruption of β cell-specific epigenetic signatures, and discuss the potential implication in therapeutic development.
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Affiliation(s)
- Xiaoqiang Sun
- Department of Physiology and Biomedical Engineering, Mayo Clinic Arizona, Scottsdale, AZ, United States
- Tianjin Fourth Central Hospital, Tianjin, China
- The Fourth Central Hospital Affiliated to Nankai University, Tianjin, China
- The Fourth Central Hospital Clinical College, Tianjin Medical University, Tianjin, China
| | - Liu Wang
- Department of Physiology and Biomedical Engineering, Mayo Clinic Arizona, Scottsdale, AZ, United States
| | - S M Bukola Obayomi
- Department of Physiology and Biomedical Engineering, Mayo Clinic Arizona, Scottsdale, AZ, United States
| | - Zong Wei
- Department of Physiology and Biomedical Engineering, Mayo Clinic Arizona, Scottsdale, AZ, United States
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Davison GW, Irwin RE, Walsh CP. The metabolic-epigenetic nexus in type 2 diabetes mellitus. Free Radic Biol Med 2021; 170:194-206. [PMID: 33429021 DOI: 10.1016/j.freeradbiomed.2020.12.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/03/2020] [Accepted: 12/04/2020] [Indexed: 02/06/2023]
Abstract
The prevalence of type 2 diabetes mellitus (T2DM) continues to rise globally. Yet the aetiology and pathophysiology of this noncommunicable, polygenic disease, is poorly understood. Lifestyle factors, such as poor dietary intake, lack of exercise, and abnormal glycaemia, are purported to play a role in disease onset and progression, and these environmental factors may disrupt specific epigenetic mechanisms, leading to a reprogramming of gene transcription. The hyperglycaemic cell per se, alters epigenetics through chemical modifications to DNA and histones via metabolic intermediates such as succinate, α-ketoglutarate and O-GlcNAc. To illustrate, α-ketoglutarate is considered a salient co-factor in the activation of the ten-eleven translocation (TET) dioxygenases, which drives DNA demethylation. On the contrary, succinate and other mitochondrial tricarboxylic acid cycle intermediates, inhibit TET activity predisposing to a state of hypermethylation. Hyperglycaemia depletes intracellular ascorbic acid, and damages DNA by enhancing the production of reactive oxygen species (ROS); this compromised cell milieu exacerbates the oxidation of 5-methylcytosine alongside a destabilisation of TET. These metabolic connections may regulate DNA methylation, affecting gene transcription and pancreatic islet β-cell function in T2DM. This complex interrelationship between metabolism and epigenetic alterations may provide a conceptual foundation for understanding how pathologic stimuli modify and control the intricacies of T2DM. As such, this narrative review will comprehensively evaluate and detail the interplay between metabolism and epigenetic modifications in T2DM.
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Affiliation(s)
- Gareth W Davison
- Ulster University, Sport and Exercise Sciences Research Institute, Newtownabbey, Northern Ireland, UK.
| | - Rachelle E Irwin
- Ulster University, Genomic Medicine Research Group, Biomedical Sciences Research Institute, Coleraine, Northern Ireland, UK
| | - Colum P Walsh
- Ulster University, Genomic Medicine Research Group, Biomedical Sciences Research Institute, Coleraine, Northern Ireland, UK
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12
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Abstract
Epigenetic modifications have been implicated to mediate several complications of diabetes mellitus (DM), especially nephropathy and retinopathy. Our aim was to ascertain whether epigenetic alterations in whole blood discriminate among patients with DM with normal, delayed, and rapid gastric emptying (GE).
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13
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Liang X, Duan H, Mao Y, Koestner U, Wei Y, Deng F, Zhuang J, Li H, Wang C, Hernandez-Miranda LR, Tao W, Jia S. The SNAG Domain of Insm1 Regulates Pancreatic Endocrine Cell Differentiation and Represses β- to δ-Cell Transdifferentiation. Diabetes 2021; 70:1084-1097. [PMID: 33547047 DOI: 10.2337/db20-0883] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 01/29/2021] [Indexed: 11/13/2022]
Abstract
The allocation and specification of pancreatic endocrine lineages are tightly regulated by transcription factors. Disturbances in differentiation of these lineages contribute to the development of various metabolic diseases, including diabetes. The insulinoma-associated protein 1 (Insm1), which encodes a protein containing one SNAG domain and five zinc fingers, plays essential roles in pancreatic endocrine cell differentiation and in mature β-cell function. In the current study, we compared the differentiation of pancreatic endocrine cells between Insm1 null and Insm1 SNAG domain mutants (Insm1delSNAG) to explore the specific function of the SNAG domain of Insm1. We show that the δ-cell number is increased in Insm1delSNAG but not in Insm1 null mutants as compared with the control mice. We also show a less severe reduction of the β-cell number in Insm1delSNAG as that in Insm1 null mutants. In addition, similar deficits are observed in α-, PP, and ε-cells in Insm1delSNAG and Insm1 null mutants. We further identified that the increased δ-cell number is due to β- to δ-cell transdifferentiation. Mechanistically, the SNAG domain of Insm1 interacts with Lsd1, the demethylase of H3K4me1/2. Mutation in the SNAG domain of Insm1 results in impaired recruitment of Lsd1 and increased H3K4me1/2 levels at hematopoietically expressed homeobox (Hhex) loci that are bound by Insm1, thereby promoting the transcriptional activity of the δ-cell-specific gene Hhex Our study has identified a novel function of the SNAG domain of Insm1 in the regulation of pancreatic endocrine cell differentiation, particularly in the repression of β- to δ-cell transdifferentiation.
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Affiliation(s)
- Xuehua Liang
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Hualin Duan
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Yahui Mao
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Ulrich Koestner
- Max Delbrück Center for Molecular Medicine, Berlin-Buch, Berlin, Germany
| | - Yiqiu Wei
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Feng Deng
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Jingshen Zhuang
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Huimin Li
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Cunchuan Wang
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Luis R Hernandez-Miranda
- Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Weihua Tao
- The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Shiqi Jia
- The First Affiliated Hospital of Jinan University, Guangzhou, China
- The Institute of Clinical Medicine, Jinan University, Guangzhou, China
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14
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van der Velde A, Fan K, Tsuji J, Moore JE, Purcaro MJ, Pratt HE, Weng Z. Annotation of chromatin states in 66 complete mouse epigenomes during development. Commun Biol 2021; 4:239. [PMID: 33619351 PMCID: PMC7900196 DOI: 10.1038/s42003-021-01756-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 01/26/2021] [Indexed: 01/31/2023] Open
Abstract
The morphologically and functionally distinct cell types of a multicellular organism are maintained by their unique epigenomes and gene expression programs. Phase III of the ENCODE Project profiled 66 mouse epigenomes across twelve tissues at daily intervals from embryonic day 11.5 to birth. Applying the ChromHMM algorithm to these epigenomes, we annotated eighteen chromatin states with characteristics of promoters, enhancers, transcribed regions, repressed regions, and quiescent regions. Our integrative analyses delineate the tissue specificity and developmental trajectory of the loci in these chromatin states. Approximately 0.3% of each epigenome is assigned to a bivalent chromatin state, which harbors both active marks and the repressive mark H3K27me3. Highly evolutionarily conserved, these loci are enriched in silencers bound by polycomb repressive complex proteins, and the transcription start sites of their silenced target genes. This collection of chromatin state assignments provides a useful resource for studying mammalian development.
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Affiliation(s)
- Arjan van der Velde
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
- Bioinformatics Program, Boston University, Boston, MA, 02215, USA
| | - Kaili Fan
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Junko Tsuji
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jill E Moore
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Michael J Purcaro
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Henry E Pratt
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA.
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15
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Geusz RJ, Wang A, Chiou J, Lancman JJ, Wetton N, Kefalopoulou S, Wang J, Qiu Y, Yan J, Aylward A, Ren B, Dong PDS, Gaulton KJ, Sander M. Pancreatic progenitor epigenome maps prioritize type 2 diabetes risk genes with roles in development. eLife 2021; 10:e59067. [PMID: 33544077 PMCID: PMC7864636 DOI: 10.7554/elife.59067] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 01/18/2021] [Indexed: 12/13/2022] Open
Abstract
Genetic variants associated with type 2 diabetes (T2D) risk affect gene regulation in metabolically relevant tissues, such as pancreatic islets. Here, we investigated contributions of regulatory programs active during pancreatic development to T2D risk. Generation of chromatin maps from developmental precursors throughout pancreatic differentiation of human embryonic stem cells (hESCs) identifies enrichment of T2D variants in pancreatic progenitor-specific stretch enhancers that are not active in islets. Genes associated with progenitor-specific stretch enhancers are predicted to regulate developmental processes, most notably tissue morphogenesis. Through gene editing in hESCs, we demonstrate that progenitor-specific enhancers harboring T2D-associated variants regulate cell polarity genes LAMA1 and CRB2. Knockdown of lama1 or crb2 in zebrafish embryos causes a defect in pancreas morphogenesis and impairs islet cell development. Together, our findings reveal that a subset of T2D risk variants specifically affects pancreatic developmental programs, suggesting that dysregulation of developmental processes can predispose to T2D.
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Affiliation(s)
- Ryan J Geusz
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
- Biomedical Graduate Studies Program, University of California, San DiegoSan DiegoUnited States
| | - Allen Wang
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
| | - Joshua Chiou
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Biomedical Graduate Studies Program, University of California, San DiegoSan DiegoUnited States
| | - Joseph J Lancman
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery InstituteSan DiegoUnited States
- Graduate School of Biomedical Sciences, Sanford Burnham Prebys Medical Discovery InstituteSan DiegoUnited States
| | - Nichole Wetton
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
| | - Samy Kefalopoulou
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
| | - Jinzhao Wang
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
| | - Yunjiang Qiu
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
| | - Jian Yan
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
| | - Anthony Aylward
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
| | - Bing Ren
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Ludwig Institute for Cancer ResearchSan DiegoUnited States
| | - P Duc Si Dong
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery InstituteSan DiegoUnited States
- Graduate School of Biomedical Sciences, Sanford Burnham Prebys Medical Discovery InstituteSan DiegoUnited States
| | - Kyle J Gaulton
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
| | - Maike Sander
- Department of Pediatrics, Pediatric Diabetes Research Center, University of California, San DiegoSan DiegoUnited States
- Department of Cellular & Molecular Medicine, University of California, San DiegoSan DiegoUnited States
- Sanford Consortium for Regenerative MedicineSan DiegoUnited States
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16
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Eufrásio A, Perrod C, Ferreira FJ, Duque M, Galhardo M, Bessa J. In Vivo Reporter Assays Uncover Changes in Enhancer Activity Caused by Type 2 Diabetes-Associated Single Nucleotide Polymorphisms. Diabetes 2020; 69:2794-2805. [PMID: 32912862 PMCID: PMC7679775 DOI: 10.2337/db19-1049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 09/02/2020] [Indexed: 12/11/2022]
Abstract
Many single nucleotide polymorphisms (SNPs) associated with type 2 diabetes overlap with putative endocrine pancreatic enhancers, suggesting that these SNPs modulate enhancer activity and, consequently, gene expression. We performed in vivo mosaic transgenesis assays in zebrafish to quantitatively test the enhancer activity of type 2 diabetes-associated loci. Six out of 10 tested sequences are endocrine pancreatic enhancers. The risk variant of two sequences decreased enhancer activity, while in another two incremented it. One of the latter (rs13266634) locates in an SLC30A8 exon, encoding a tryptophan-to-arginine substitution that decreases SLC30A8 function, which is the canonical explanation for type 2 diabetes risk association. However, other type 2 diabetes-associated SNPs that truncate SLC30A8 confer protection from this disease, contradicting this explanation. Here, we clarify this incongruence, showing that rs13266634 boosts the activity of an overlapping enhancer and suggesting an SLC30A8 gain of function as the cause for the increased risk for the disease. We further dissected the functionality of this enhancer, finding a single nucleotide mutation sufficient to impair its activity. Overall, this work assesses in vivo the importance of disease-associated SNPs in the activity of endocrine pancreatic enhancers, including a poorly explored case where a coding SNP modulates the activity of an enhancer.
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Affiliation(s)
- Ana Eufrásio
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
| | - Chiara Perrod
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
| | - Fábio J Ferreira
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
| | - Marta Duque
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
| | - Mafalda Galhardo
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
| | - José Bessa
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, and IBMC-Instituto de Biologia Celular e Molecular, Porto, Portugal
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17
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Kim H, Kulkarni RN. Epigenetics in β-cell adaptation and type 2 diabetes. Curr Opin Pharmacol 2020; 55:125-131. [PMID: 33232934 DOI: 10.1016/j.coph.2020.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/29/2020] [Accepted: 10/09/2020] [Indexed: 02/06/2023]
Abstract
Healthy pancreatic β-cells adapt to systemic insulin resistance to maintain normal blood glucose levels, and a failure of this adaptation leads to type 2 diabetes in humans. While genome-wide association studies have uncovered genetic variants that are associated with type 2 diabetes, it is still insufficient to explain the high prevalence of this disease. Epigenetics is the study of gene expression changes that do not involve DNA sequence alterations such as DNA methylation, histone modification, and non-coding RNAs. Over the last decade, a large number of studies have reported on the role of epigenetics in β-cell biology. In this review, we summarize the epigenetic mechanisms in β-cell adaptation and type 2 diabetes, including alterations in three-dimensional chromatin structure and RNA modifications.
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Affiliation(s)
- Hyunki Kim
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Boston, MA, USA; Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Rohit N Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Boston, MA, USA; Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA.
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18
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Eizirik DL, Pasquali L, Cnop M. Pancreatic β-cells in type 1 and type 2 diabetes mellitus: different pathways to failure. Nat Rev Endocrinol 2020; 16:349-362. [PMID: 32398822 DOI: 10.1038/s41574-020-0355-7] [Citation(s) in RCA: 373] [Impact Index Per Article: 93.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/24/2020] [Indexed: 12/12/2022]
Abstract
Loss of functional β-cell mass is the key mechanism leading to the two main forms of diabetes mellitus - type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Understanding the mechanisms behind β-cell failure is critical to prevent or revert disease. Basic pathogenic differences exist in the two forms of diabetes mellitus; T1DM is immune mediated and T2DM is mediated by metabolic mechanisms. These mechanisms differentially affect early β-cell dysfunction and eventual fate. Over the past decade, major advances have been made in the field, mostly delivered by studies on β-cells in human disease. These advances include studies of islet morphology and human β-cell gene expression in T1DM and T2DM, the identification and characterization of the role of T1DM and T2DM candidate genes at the β-cell level and the endoplasmic reticulum stress signalling that contributes to β-cell failure in T1DM (mostly IRE1 driven) and T2DM (mostly PERK-eIF2α dependent). Here, we review these new findings, focusing on studies performed on human β-cells or on samples obtained from patients with diabetes mellitus.
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Affiliation(s)
- Décio L Eizirik
- ULB Center for Diabetes Research, Welbio Investigator, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium.
- Indiana Biosciences Research Institute (IBRI), Indianapolis, IN, USA.
| | - Lorenzo Pasquali
- Endocrine Regulatory Genomics, Department of Experimental & Health Sciences, University Pompeu Fabra, Barcelona, Spain.
- Germans Trias i Pujol University Hospital and Research Institute, Badalona, Spain.
- Josep Carreras Leukaemia Research Institute, Barcelona, Spain.
| | - Miriam Cnop
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium.
- Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium.
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19
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Abstract
BACKGROUND Pancreatic β-cells adapt to high metabolic demand by expanding their β-cell mass and/or enhancing insulin secretion to maintain glucose homeostasis. Type 2 diabetes (T2D) is typically characterized by β-cell decompensation. SCOPE OF THE REVIEW The current review focuses on summarizing the "omics" and "epi-omics" approaches that particularly focus on addressing the β-cell adaptation to insulin resistance and T2D. MAJOR CONCLUSIONS The molecular mechanisms underlying successful versus compromised β-cell adaptation to insulin resistance are not entirely understood. The last decade has seen an exponential increase in the use of "omics" and "epi-omics" approaches to dissect pathophysiology of metabolic diseases. One recent example is the emergence of m6A mRNA methylation as a new layer of regulation of gene expression with the potential to impact diverse physiological processes in metabolic cells.
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Affiliation(s)
- Dario F De Jesus
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Medical School, Boston, USA; Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, USA; Harvard Stem Cell Institute, Boston, USA
| | - Rohit N Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Medical School, Boston, USA; Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, USA; Harvard Stem Cell Institute, Boston, USA.
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20
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Symmank J, Bayer C, Reichard J, Pensold D, Zimmer-Bensch G. Neuronal Lhx1 expression is regulated by DNMT1-dependent modulation of histone marks. Epigenetics 2020; 15:1259-1274. [PMID: 32441560 PMCID: PMC7595593 DOI: 10.1080/15592294.2020.1767372] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Apart from the conventional view of repressive promoter methylation, the DNA methyltransferase 1 (DNMT1) was recently described to modulate gene expression through a variety of interactions with diverse epigenetic key players. We here investigated the DNMT1-dependent transcriptional control of the homeobox transcription factor LHX1, which we previously identified as an important regulator in cortical interneuron development. We found that LHX1 expression in embryonic interneurons originating in the embryonic pre-optic area (POA) is regulated by non-canonic DNMT1 function. Analysis of histone methylation and acetylation revealed that both epigenetic modifications seem to be implicated in the control of Lhx1 gene activity and that DNMT1 contributes to their proper establishment. This study sheds further light on the regulatory network of cortical interneuron development including the complex interplay of epigenetic mechanisms.
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Affiliation(s)
- Judit Symmank
- Institute for Human Genetics, Am Klinikum 1, University Hospital Jena , Jena, Germany.,Polyclinic for Orthodontics, Leutragraben 3, University Hospital Jena , Jena, Germany
| | - Cathrin Bayer
- Institute for Human Genetics, Am Klinikum 1, University Hospital Jena , Jena, Germany.,Department of Functional Epigenetics in the Animal Model, Institute for Biology II, Worringerweg 3, RWTH Aachen University , Aachen, Germany
| | - Julia Reichard
- Institute for Human Genetics, Am Klinikum 1, University Hospital Jena , Jena, Germany.,Department of Functional Epigenetics in the Animal Model, Institute for Biology II, Worringerweg 3, RWTH Aachen University , Aachen, Germany.,Research Training Group 2416 MultiSenses, MultiScales, RWTH Aachen University , Aachen, Germany
| | - Daniel Pensold
- Institute for Human Genetics, Am Klinikum 1, University Hospital Jena , Jena, Germany.,Department of Functional Epigenetics in the Animal Model, Institute for Biology II, Worringerweg 3, RWTH Aachen University , Aachen, Germany
| | - Geraldine Zimmer-Bensch
- Institute for Human Genetics, Am Klinikum 1, University Hospital Jena , Jena, Germany.,Polyclinic for Orthodontics, Leutragraben 3, University Hospital Jena , Jena, Germany.,Department of Functional Epigenetics in the Animal Model, Institute for Biology II, Worringerweg 3, RWTH Aachen University , Aachen, Germany
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21
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Hossan T, Kundu S, Alam SS, Nagarajan S. Epigenetic Modifications Associated with the Pathogenesis of Type 2 Diabetes Mellitus. Endocr Metab Immune Disord Drug Targets 2020; 19:775-786. [PMID: 30827271 DOI: 10.2174/1871530319666190301145545] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 12/10/2018] [Accepted: 12/28/2018] [Indexed: 12/26/2022]
Abstract
BACKGROUND AND OBJECTIVE Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder. Pancreatic β-cell dysfunction and insulin resistance are the most common and crucial events of T2DM. Increasing evidence suggests the association of epigenetic modifications with the pathogenesis of T2DM through the changes in important biological processes including pancreatic β- cell differentiation, development and maintenance of normal β-cell function. Insulin sensitivity by the peripheral glucose uptake tissues is also changed by the altered epigenetic mechanisms. In this review, we discussed the major epigenetic alterations and their effects on β-cell function, insulin secretion and insulin resistance in context of T2DM. METHODS We investigated the presently available epigenetic modifications including DNA methylation, posttranslational histone modifications, ATP-dependent chromatin remodeling and non-coding RNAs related to the pathogenesis of T2DM. Published literatures on this topic were searched both on Google Scholar and Pubmed with related keywords and investigated for relevant information. RESULTS The epigenetic modifications introduce changes in gene expression which are essential for appropriate β-cell development and functions, insulin secretion and sensitivity resulting in the pathogenesis of T2DM. Interestingly, T2DM could also be a prominent reason for the mentioned epigenetic alterations. CONCLUSION This review article emphasized on the epigenetic modifications associated with T2DM and discussed the consequences in deterioration of the disease condition.
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Affiliation(s)
- Tareq Hossan
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
| | - Shoumik Kundu
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
| | - Sayeda Sadia Alam
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
| | - Sankari Nagarajan
- Cancer Research UK Cambridge Institute (CRUK-CI), University of Cambridge, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, United Kingdom
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22
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Wesolowska-Andersen A, Zhuo Yu G, Nylander V, Abaitua F, Thurner M, Torres JM, Mahajan A, Gloyn AL, McCarthy MI. Deep learning models predict regulatory variants in pancreatic islets and refine type 2 diabetes association signals. eLife 2020; 9:e51503. [PMID: 31985400 PMCID: PMC7007221 DOI: 10.7554/elife.51503] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 01/27/2020] [Indexed: 12/30/2022] Open
Abstract
Genome-wide association analyses have uncovered multiple genomic regions associated with T2D, but identification of the causal variants at these remains a challenge. There is growing interest in the potential of deep learning models - which predict epigenome features from DNA sequence - to support inference concerning the regulatory effects of disease-associated variants. Here, we evaluate the advantages of training convolutional neural network (CNN) models on a broad set of epigenomic features collected in a single disease-relevant tissue - pancreatic islets in the case of type 2 diabetes (T2D) - as opposed to models trained on multiple human tissues. We report convergence of CNN-based metrics of regulatory function with conventional approaches to variant prioritization - genetic fine-mapping and regulatory annotation enrichment. We demonstrate that CNN-based analyses can refine association signals at T2D-associated loci and provide experimental validation for one such signal. We anticipate that these approaches will become routine in downstream analyses of GWAS.
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Affiliation(s)
| | - Grace Zhuo Yu
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUnited Kingdom
| | - Vibe Nylander
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUnited Kingdom
| | | | - Matthias Thurner
- Wellcome Centre for Human GeneticsOxfordUnited Kingdom
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUnited Kingdom
| | | | | | - Anna L Gloyn
- Wellcome Centre for Human GeneticsOxfordUnited Kingdom
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUnited Kingdom
- Oxford NIHR Biomedical CentreChurchill HospitalOxfordUnited Kingdom
| | - Mark I McCarthy
- Wellcome Centre for Human GeneticsOxfordUnited Kingdom
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUnited Kingdom
- Oxford NIHR Biomedical CentreChurchill HospitalOxfordUnited Kingdom
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23
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Kuo T, Damle M, González BJ, Egli D, Lazar MA, Accili D. Induction of α cell-restricted Gc in dedifferentiating β cells contributes to stress-induced β-cell dysfunction. JCI Insight 2019; 5:128351. [PMID: 31120862 DOI: 10.1172/jci.insight.128351] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Diabetic β cell failure is associated with β cell dedifferentiation. To identify effector genes of dedifferentiation, we integrated analyses of histone methylation as a surrogate of gene activation status and RNA expression in β cells sorted from mice with multiparity-induced diabetes. Interestingly, only a narrow subset of genes demonstrated concordant changes to histone methylation and RNA levels in dedifferentiating β cells. Notable among them was the α cell signature gene Gc, encoding a vitamin D-binding protein. While diabetes was associated with Gc induction, Gc-deficient islets did not induce β cell dedifferentiation markers and maintained normal ex vivo insulin secretion in the face of metabolic challenge. Moreover, Gc-deficient mice exhibited a more robust insulin secretory response than normal controls during hyperglycemic clamps. The data are consistent with a functional role of Gc activation in β cell dysfunction, and indicate that multiparity-induced diabetes is associated with altered β cell fate.
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Affiliation(s)
- Taiyi Kuo
- Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Manashree Damle
- The Institute for Diabetes, Obesity, and Metabolism, and Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Bryan J González
- Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA.,Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Dieter Egli
- Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA.,Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Mitchell A Lazar
- The Institute for Diabetes, Obesity, and Metabolism, and Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Domenico Accili
- Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA
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24
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Ling C, Rönn T. Epigenetics in Human Obesity and Type 2 Diabetes. Cell Metab 2019; 29:1028-1044. [PMID: 30982733 PMCID: PMC6509280 DOI: 10.1016/j.cmet.2019.03.009] [Citation(s) in RCA: 452] [Impact Index Per Article: 90.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 03/05/2019] [Accepted: 03/18/2019] [Indexed: 12/16/2022]
Abstract
Epigenetic mechanisms control gene activity and the development of an organism. The epigenome includes DNA methylation, histone modifications, and RNA-mediated processes, and disruption of this balance may cause several pathologies and contribute to obesity and type 2 diabetes (T2D). This Review summarizes epigenetic signatures obtained from human tissues of relevance for metabolism-i.e., adipose tissue, skeletal muscle, pancreatic islets, liver, and blood-in relation to obesity and T2D. Although this research field is still young, these comprehensive data support not only a role for epigenetics in disease development, but also epigenetic alterations as a response to disease. Genetic predisposition, as well as aging, contribute to epigenetic variability, and several environmental factors, including exercise and diet, further interact with the human epigenome. The reversible nature of epigenetic modifications holds promise for future therapeutic strategies in obesity and T2D.
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Affiliation(s)
- Charlotte Ling
- Epigenetics and Diabetes Unit, Department of Clinical Sciences Malmö, Lund University Diabetes Centre, Scania University Hospital, Malmö, Sweden.
| | - Tina Rönn
- Epigenetics and Diabetes Unit, Department of Clinical Sciences Malmö, Lund University Diabetes Centre, Scania University Hospital, Malmö, Sweden
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25
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Abstract
Chronic, noncommunicable, and inflammation-associated diseases remain the largest cause of morbidity and mortality globally and within the United States. This is mainly due to our limited understanding of the molecular mechanisms that underlie these complex pathologies. The available evidence indicates that studies of epigenetics (traditionally defined as the heritable changes to gene expression that are independent of changes to DNA) are significantly advancing our knowledge of these inflammatory conditions. This review will focus on epigenetic studies of three diseases, that are among the most burdensome globally: cardiovascular disease, the number one cause of deaths worldwide, type 2 diabetes and, Alzheimer’s disease. The current status of epigenetic research, including the ability to predict disease risk, and key pathophysiological defects are discussed. The significance of defining the contribution of epigenetic defects to nonresolving inflammation and aging, each associated with these diseases, is highlighted, as these are likely to provide new insights into inflammatory disease pathogenesis.
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Affiliation(s)
- Eleni Stylianou
- Consultant Biomedical Scientist and Bioinformaticist, North Royalton, OH, USA,
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26
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Symmank J, Bayer C, Schmidt C, Hahn A, Pensold D, Zimmer-Bensch G. DNMT1 modulates interneuron morphology by regulating Pak6 expression through crosstalk with histone modifications. Epigenetics 2018; 13:536-556. [PMID: 29912614 DOI: 10.1080/15592294.2018.1475980] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Epigenetic mechanisms of gene regulation, including DNA methylation and histone modifications, call increasing attention in the context of development and human health. Thereby, interactions between DNA methylating enzymes and histone modifications tremendously multiply the spectrum of potential regulatory functions. Epigenetic networks are critically involved in the establishment and functionality of neuronal circuits that are composed of gamma-aminobutyric acid (GABA)-positive inhibitory interneurons and excitatory principal neurons in the cerebral cortex. We recently reported a crucial role of the DNA methyltransferase 1 (DNMT1) during the migration of immature POA-derived cortical interneurons by promoting the migratory morphology through repression of Pak6. However, the DNMT1-dependent regulation of Pak6 expression appeared to occur independently of direct DNA methylation. Here, we show that in addition to its DNA methylating activity, DNMT1 can act on gene transcription by modulating permissive H3K4 and repressive H3K27 trimethylation in developing inhibitory interneurons, similar to what was found in other cell types. In particular, the transcriptional control of Pak6, interactions of DNMT1 with the Polycomb-repressor complex 2 (PCR2) core enzyme EZH2, mediating repressive H3K27 trimethylations at regulatory regions of the Pak6 gene locus. Similar to what was observed upon Dnmt1 depletion, inhibition of EZH2 caused elevated Pak6 expression levels accompanied by increased morphological complexity, which was rescued by siRNA-mediated downregulation of Pak6 expression. Together, our data emphasise the relevance of DNMT1-dependent crosstalk with histone tail methylation for transcriptional control of genes like Pak6 required for proper cortical interneuron migration.
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Affiliation(s)
- Judit Symmank
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany
| | - Cathrin Bayer
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany
| | - Christiane Schmidt
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany
| | - Anne Hahn
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany
| | - Daniel Pensold
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany
| | - Geraldine Zimmer-Bensch
- a Institute of Human Genetics , University Hospital Jena , Jena , Germany.,b Institute for Biology II , Division of Functional Epigenetics in the Animal Model, RWTH Aachen University , Aachen , Germany
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27
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An Assessment of Fixed and Native Chromatin Preparation Methods to Study Histone Post-Translational Modifications at a Whole Genome Scale in Skeletal Muscle Tissue. Biol Proced Online 2017; 19:10. [PMID: 28855851 PMCID: PMC5576305 DOI: 10.1186/s12575-017-0059-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 07/31/2017] [Indexed: 11/10/2022] Open
Abstract
Background Genomic loci associated with histone marks are typically analyzed by immunoprecipitation of the chromatin followed by quantitative-PCR (ChIP-qPCR) or high throughput sequencing (ChIP-seq). Chromatin can be either cross-linked (X-ChIP) or used in the native state (N-ChIP). Cross-linking of DNA and proteins helps stabilizing their interactions before analysis. Despite X-ChIP is the most commonly used method, muscle tissue fixation is known to be relatively inefficient. Moreover, no protocol described a simple and reliable preparation of skeletal muscle chromatin of sufficient quality for subsequent high-throughput sequencing. Here we aimed to set-up and compare both chromatin preparation methods for a genome-wide analysis of H3K27me3, a broad-peak histone mark, using chicken P. major muscle tissue. Results Fixed and unfixed chromatin were prepared from chicken muscle tissues (Pectoralis major). Chromatin fixation, shearing by sonication or digestion and immunoprecipitation performed equivalently. High-quality Illumina reads were obtained (q30 > 93%). The bioinformatic analysis of the data was performed using epic, a tool based on SICER, and MACS2. Forty millions of reads were analyzed for both X-ChIP-seq and N-ChIP-seq experiments. Surprisingly, H3K27me3 X-ChIP-seq analysis led to the identification of only 2000 enriched regions compared to about 15,000 regions identified in the case of N-ChIP-seq. N-ChIP-seq peaks were more consistent between replicates compared to X-ChIP-seq. Higher N-ChIP-seq enrichments were confirmed by ChIP-qPCR at the PAX5 and SOX2 loci known to be enriched for H3K27me3 in myotubes and at the loci of common regions of enrichment identified in this study. Conclusions Our findings suggest that the preparation of muscle chromatin for ChIP-seq in cross-linked conditions can compromise the systematic analysis of broad histone marks. Therefore, native chromatin preparation should be preferred to cross-linking when a ChIP experiment has to be performed on skeletal muscle tissue, particularly when a broad source signal is considered. Electronic supplementary material The online version of this article (doi:10.1186/s12575-017-0059-0) contains supplementary material, which is available to authorized users.
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28
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Dajani R, Li J, Wei Z, March ME, Xia Q, Khader Y, Hakooz N, Fatahallah R, El-Khateeb M, Arafat A, Saleh T, Dajani AR, Al-Abbadi Z, Abdul Qader M, Shiyab AH, Bateiha A, Ajlouni K, Hakonarson H. Genome-wide association study identifies novel type II diabetes risk loci in Jordan subpopulations. PeerJ 2017; 5:e3618. [PMID: 28828242 PMCID: PMC5563445 DOI: 10.7717/peerj.3618] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 07/06/2017] [Indexed: 12/14/2022] Open
Abstract
The prevalence of Type II Diabetes (T2D) has been increasing and has become a disease of significant public health burden in Jordan. None of the previous genome-wide association studies (GWAS) have specifically investigated the Middle East populations. The Circassian and Chechen communities in Jordan represent unique populations that are genetically distinct from the Arab population and other populations in the Caucasus. Prevalence of T2D is very high in both the Circassian and Chechen communities in Jordan despite low obesity prevalence. We conducted GWAS on T2D in these two populations and further performed meta-analysis of the results. We identified a novel T2D locus at chr20p12.2 at genome-wide significance (rs6134031, P = 1.12 × 10−8) and we replicated the results in the Wellcome Trust Case Control Consortium (WTCCC) dataset. Another locus at chr12q24.31 is associated with T2D at suggestive significance level (top SNP rs4758690, P = 4.20 × 10−5) and it is a robust eQTL for the gene, MLXIP (P = 1.10 × 10−14), and is significantly associated with methylation level in MLXIP, the functions of which involves cellular glucose response. Therefore, in this first GWAS of T2D in Jordan subpopulations, we identified novel and unique susceptibility loci which may help inform the genetic underpinnings of T2D in other populations.
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Affiliation(s)
- Rana Dajani
- Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan
| | - Jin Li
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States of America.,Department of Cell Biology, Tianjin Medical University, Tianjin, China
| | - Zhi Wei
- Department of Computer Science, New Jersey Institute of Technology, Newark, NJ, United States of America
| | - Michael E March
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States of America
| | - Qianghua Xia
- Department of Cell Biology, Tianjin Medical University, Tianjin, China.,Divisions of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States of America
| | - Yousef Khader
- Department of Community Medicine, Public Health and Family Medicine, Faculty of Medicine, Jordan University for Science and Technology, Irbid, Jordan
| | - Nancy Hakooz
- Department of Biopharmaceutics and Clinical Pharmacy, School of Pharmacy, University of Jordan, Amman, Jordan
| | - Raja Fatahallah
- National Center for Diabetes, Endocrinology and Genetics, Amman, Jordan
| | | | - Ala Arafat
- National Center for Diabetes, Endocrinology and Genetics, Amman, Jordan
| | - Tareq Saleh
- Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan
| | - Abdel Rahman Dajani
- Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan
| | - Zaid Al-Abbadi
- Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan
| | - Mohamed Abdul Qader
- Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan
| | | | - Anwar Bateiha
- Department of Community Medicine, Public Health and Family Medicine, Faculty of Medicine, Jordan University for Science and Technology, Irbid, Jordan
| | - Kamel Ajlouni
- National Center for Diabetes, Endocrinology and Genetics, Amman, Jordan
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States of America.,Divisions of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States of America.,The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
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29
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Al-Khawaga S, Memon B, Butler AE, Taheri S, Abou-Samra AB, Abdelalim EM. Pathways governing development of stem cell-derived pancreatic β cells: lessons from embryogenesis. Biol Rev Camb Philos Soc 2017. [DOI: 10.1111/brv.12349] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Sara Al-Khawaga
- Diabetes Research Center, Qatar Biomedical Research Institute; Hamad Bin Khalifa University, Qatar Foundation, Education City; Doha Qatar
| | - Bushra Memon
- Diabetes Research Center, Qatar Biomedical Research Institute; Hamad Bin Khalifa University, Qatar Foundation, Education City; Doha Qatar
| | - Alexandra E. Butler
- Larry L. Hillblom Islet Research Center, David Geffen School of Medicine; University of California; Los Angeles CA 90095 U.S.A
| | - Shahrad Taheri
- Department of Medicine; Weill Cornell Medicine in Qatar, Qatar Foundation, Education City, PO BOX 24144; Doha Qatar
- Department of Medicine; Qatar Metabolic Institute, Hamad Medical Corporation; Doha Qatar
| | - Abdul B. Abou-Samra
- Department of Medicine; Weill Cornell Medicine in Qatar, Qatar Foundation, Education City, PO BOX 24144; Doha Qatar
- Department of Medicine; Qatar Metabolic Institute, Hamad Medical Corporation; Doha Qatar
| | - Essam M. Abdelalim
- Diabetes Research Center, Qatar Biomedical Research Institute; Hamad Bin Khalifa University, Qatar Foundation, Education City; Doha Qatar
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30
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Weisbeck A, Jansen RJ. Nutrients and the Pancreas: An Epigenetic Perspective. Nutrients 2017; 9:nu9030283. [PMID: 28294968 PMCID: PMC5372946 DOI: 10.3390/nu9030283] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/07/2017] [Accepted: 03/06/2017] [Indexed: 12/15/2022] Open
Abstract
Pancreatic cancer is the fourth most common cause of cancer-related deaths with a dismal average five-year survival rate of six percent. Substitutional progress has been made in understanding how pancreatic cancer develops and progresses. Evidence is mounting which demonstrates that diet and nutrition are key factors in carcinogenesis. In particular, diets low in folate and high in fruits, vegetables, red/processed meat, and saturated fat have been identified as pancreatic cancer risk factors with a proposed mechanism involving epigenetic modifications or gene regulation. We review the current literature assessing the correlation between diet, epigenetics, and pancreatic cancer.
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Affiliation(s)
- Andee Weisbeck
- Department of Public Health, North Dakota State University, Fargo, ND 58102, USA.
| | - Rick J Jansen
- Department of Public Health, North Dakota State University, Fargo, ND 58102, USA.
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31
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Functional annotation of sixty-five type-2 diabetes risk SNPs and its application in risk prediction. Sci Rep 2017; 7:43709. [PMID: 28262806 PMCID: PMC5337961 DOI: 10.1038/srep43709] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 01/26/2017] [Indexed: 01/04/2023] Open
Abstract
Genome-wide association studies (GWAS) have identified more than sixty single nucleotide polymorphisms (SNPs) associated with increased risk for type 2 diabetes (T2D). However, the identification of causal risk SNPs for T2D pathogenesis was complicated by the factor that each risk SNP is a surrogate for the hundreds of SNPs, most of which reside in non-coding regions. Here we provide a comprehensive annotation of 65 known T2D related SNPs and inspect putative functional SNPs probably causing protein dysfunction, response element disruptions of known transcription factors related to T2D genes and regulatory response element disruption of four histone marks in pancreas and pancreas islet. In new identified risk SNPs, some of them were reported as T2D related SNPs in recent studies. Further, we found that accumulation of modest effects of single sites markedly enhanced the risk prediction based on 1989 T2D samples and 3000 healthy controls. The AROC value increased from 0.58 to 0.62 by only using genotype score when putative risk SNPs were added. Besides, the net reclassification improvement is 10.03% on the addition of new risk SNPs. Taken together, functional annotation could provide a list of prioritized potential risk SNPs for the further estimation on the T2D susceptibility of individuals.
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32
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Mularoni L, Ramos-Rodríguez M, Pasquali L. The Pancreatic Islet Regulome Browser. Front Genet 2017; 8:13. [PMID: 28261261 PMCID: PMC5306130 DOI: 10.3389/fgene.2017.00013] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 01/23/2017] [Indexed: 11/14/2022] Open
Abstract
The pancreatic islet is a highly specialized tissue embedded in the exocrine pancreas whose primary function is that of controlling glucose homeostasis. Thus, understanding the transcriptional control of islet-cell may help to puzzle out the pathogenesis of glucose metabolism disorders. Integrative computational analyses of transcriptomic and epigenomic data allows predicting genomic coordinates of putative regulatory elements across the genome and, decipher tissue-specific functions of the non-coding genome. We herein present the Islet Regulome Browser, a tool that allows fast access and exploration of pancreatic islet epigenomic and transcriptomic data produced by different labs worldwide. The Islet Regulome Browser is now accessible on the internet or may be installed locally. It allows uploading custom tracks as well as providing interactive access to a wealth of information including Genome-Wide Association Studies (GWAS) variants, different classes of regulatory elements, together with enhancer clusters, stretch-enhancers and transcription factor binding sites in pancreatic progenitors and adult human pancreatic islets. Integration and visualization of such data may allow a deeper understanding of the regulatory networks driving tissue-specific transcription and guide the identification of regulatory variants. We believe that such tool will facilitate the access to pancreatic islet public genomic datasets providing a major boost to functional genomics studies in glucose metabolism related traits including diabetes.
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Affiliation(s)
- Loris Mularoni
- Research Program on Biomedical Informatics, IMIM Hospital del Mar Medical Research Institute and Universitat Pompeu FabraBarcelona, Spain; Biomedical Genomics, Institute for Research in Biomedicine, The Barcelona Institute of Science and TechnologyBarcelona, Spain
| | - Mireia Ramos-Rodríguez
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias i Pujol University Hospital and Research Institute Badalona, Spain
| | - Lorenzo Pasquali
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias i Pujol University Hospital and Research InstituteBadalona, Spain; Germans Trias i Pujol Campus, Josep Carreras Leukaemia Research InstituteBadalona, Spain; CIBER de Diabetes y Enfermedades Metabólicas AsociadasBarcelona, Spain
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33
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Bernstein D, Golson ML, Kaestner KH. Epigenetic control of β-cell function and failure. Diabetes Res Clin Pract 2017; 123:24-36. [PMID: 27918975 PMCID: PMC5250585 DOI: 10.1016/j.diabres.2016.11.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 11/15/2016] [Indexed: 12/21/2022]
Abstract
Type 2 diabetes is a highly heritable disease, but only ∼15% of this heritability can be explained by known genetic variant loci. In fact, body mass index is more predictive of diabetes than any of the common risk alleles identified by genome-wide association studies. This discrepancy may be explained by epigenetic inheritance, whereby changes in gene regulation can be passed along to offspring. Epigenetic changes throughout an organism's lifetime, based on environmental factors such as chemical exposures, diet, physical activity, and age, can also affect gene expression and susceptibility to diabetes. Recently, novel genome-wide assays of epigenetic marks have resulted in a greater understanding of how genetics, epigenetics, and the environment interact in the development and inheritance of diabetes.
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Affiliation(s)
- Diana Bernstein
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Maria L Golson
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Bermick JR, Lambrecht NJ, denDekker AD, Kunkel SL, Lukacs NW, Hogaboam CM, Schaller MA. Neonatal monocytes exhibit a unique histone modification landscape. Clin Epigenetics 2016; 8:99. [PMID: 27660665 PMCID: PMC5028999 DOI: 10.1186/s13148-016-0265-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 09/08/2016] [Indexed: 12/17/2022] Open
Abstract
Background Neonates have dampened expression of pro-inflammatory cytokines and difficulty clearing pathogens. This makes them uniquely susceptible to infections, but the factors regulating neonatal-specific immune responses are poorly understood. Epigenetics, including histone modifications, can activate or silence gene transcription by modulating chromatin structure and stability without affecting the DNA sequence itself and are potentially modifiable. Histone modifications are known to regulate immune cell differentiation and function in adults but have not been well studied in neonates. Results To elucidate the role of histone modifications in neonatal immune function, we performed chromatin immunoprecipitation on mononuclear cells from 45 healthy neonates (gestational ages 23–40 weeks). As gestation approached term, there was increased activating H3K4me3 on the pro-inflammatory IL1B, IL6, IL12B, and TNF cytokine promoters (p < 0.01) with no change in repressive H3K27me3, suggesting that these promoters in preterm neonates are less open and accessible to transcription factors than in term neonates. Chromatin immunoprecipitation with massively parallel DNA sequencing (ChIP-seq) was then performed to establish the H3K4me3, H3K9me3, H3K27me3, H3K4me1, H3K27ac, and H3K36me3 landscapes in neonatal and adult CD14+ monocytes. As development progressed from neonate to adult, monocytes lost the poised enhancer mark H3K4me1 and gained the activating mark H3K4me3, without a change in additional histone modifications. This decreased H3K4me3 abundance at immunologically important neonatal monocyte gene promoters, including CCR2, CD300C, ILF2, IL1B, and TNF was associated with reduced gene expression. Conclusions These results provide evidence that neonatal immune cells exist in an epigenetic state that is distinctly different from adults and that this state contributes to neonatal-specific immune responses that leaves them particularly vulnerable to infections. Electronic supplementary material The online version of this article (doi:10.1186/s13148-016-0265-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jennifer R Bermick
- Department of Pediatrics, Division of Neonatal-Perinatal Medicine, University of Michigan Medical Center, 1540 E. Medical Center Drive, C.S. Mott Children's Hospital Room 8-621, Ann Arbor, MI 48109 USA
| | - Nathalie J Lambrecht
- Department of Pediatrics, Division of Neonatal-Perinatal Medicine, University of Michigan Medical Center, 1540 E. Medical Center Drive, C.S. Mott Children's Hospital Room 8-621, Ann Arbor, MI 48109 USA
| | - Aaron D denDekker
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, MI 48109 USA
| | - Steven L Kunkel
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, MI 48109 USA
| | - Nicholas W Lukacs
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, MI 48109 USA
| | - Cory M Hogaboam
- Department of Medicine, Division of Pulmonary & Critical Care Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048 USA
| | - Matthew A Schaller
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, MI 48109 USA
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35
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Campbell SA, Hoffman BG. Chromatin Regulators in Pancreas Development and Diabetes. Trends Endocrinol Metab 2016; 27:142-152. [PMID: 26783078 DOI: 10.1016/j.tem.2015.12.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/21/2015] [Accepted: 12/23/2015] [Indexed: 12/17/2022]
Abstract
The chromatin landscape of a cell is dynamic and can be altered by chromatin regulators that control nucleosome placement and DNA or histone modifications. Together with transcription factors, these complexes help dictate the transcriptional output of a cell and, thus, balance cell proliferation and differentiation while restricting tissue-specific gene expression. In this review, we describe current research on chromatin regulators and their roles in pancreas development and the maintenance of mature β cell function, which, once elucidated, will help us better understand how β cell differentiation occurs and is maintained. These studies have so far implicated proteins from several complexes that regulate DNA methylation, nucleosome remodeling, and histone acetylation and methylation that could become promising targets for diabetes therapy and stem cell differentiation.
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MESH Headings
- Animals
- Cell Differentiation
- Cell Proliferation
- Chromatin Assembly and Disassembly
- Chromosomal Proteins, Non-Histone/genetics
- Chromosomal Proteins, Non-Histone/metabolism
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/pathology
- Diabetes Mellitus, Type 1/physiopathology
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Diabetes Mellitus, Type 2/physiopathology
- Epigenesis, Genetic
- Gene Expression Regulation, Developmental
- Histones/genetics
- Histones/metabolism
- Humans
- Insulin-Secreting Cells/cytology
- Insulin-Secreting Cells/metabolism
- Insulin-Secreting Cells/pathology
- Islets of Langerhans/cytology
- Islets of Langerhans/growth & development
- Islets of Langerhans/metabolism
- Islets of Langerhans/pathology
- Models, Biological
- Nucleosomes/metabolism
- Protein Processing, Post-Translational
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Affiliation(s)
- Stephanie A Campbell
- Child and Family Research Institute, British Columbia Children's Hospital and Sunny Hill Health Centre, 950 W28th Avenue, Vancouver, BC, V5Z 4H4, Canada
| | - Brad G Hoffman
- Child and Family Research Institute, British Columbia Children's Hospital and Sunny Hill Health Centre, 950 W28th Avenue, Vancouver, BC, V5Z 4H4, Canada; Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4E3, Canada.
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36
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Lin B, Lee H, Yoon JG, Madan A, Wayner E, Tonning S, Hothi P, Schroeder B, Ulasov I, Foltz G, Hood L, Cobbs C. Global analysis of H3K4me3 and H3K27me3 profiles in glioblastoma stem cells and identification of SLC17A7 as a bivalent tumor suppressor gene. Oncotarget 2016; 6:5369-81. [PMID: 25749033 PMCID: PMC4467155 DOI: 10.18632/oncotarget.3030] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 01/01/2015] [Indexed: 01/21/2023] Open
Abstract
Epigenetic changes, including H3K4me3 and H3K27me3 histone modification, play an important role in carcinogenesis. However, no genome-wide histone modification map has been generated for gliomas. Here, we report a genome-wide map of H3K4me3 and H3K27me3 histone modifications for 8 glioma stem cell (GSC) lines, together with the associated gene activation or repression patterns. In addition, we compared the genome-wide histone modification maps of GSC lines to those of astrocytes to identify unique gene activation or repression profiles in GSCs and astrocytes. We also identified a set of bivalent genes, which are genes that are associated with both H3K4me3 and H3K27me3 marks and are poised for action in embryonic stem cells. These bivalent genes are potential targets for inducing differentiation in glioblastoma (GBM) as a therapeutic approach. Finally, we identified SLC17A7 as a bivalent tumor suppressor gene in GBM, as it is down-regulated at both the protein and RNA levels in GBM tissues compared with normal brain tissues, and it inhibits GBM cell proliferation, migration and invasion.
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Affiliation(s)
- Biaoyang Lin
- Cancer Institute (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education), The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, China.,Dept. of Urology, University of Washington, Seattle, WA 98195, USA.,System Biology Division, Zhejiang-California International Nanosystem Institute (ZCNI), Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Hwahyung Lee
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Jae-Geun Yoon
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Anup Madan
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA.,LabCorp Clinical Trials (Genomics Laboratory), Seattle, WA 98109, USA
| | - Elizabeth Wayner
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Sanja Tonning
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Parvinder Hothi
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Brett Schroeder
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Ilya Ulasov
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Gregory Foltz
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
| | - Leroy Hood
- The Institute for Systems Biology, Seattle, WA 98109, USA
| | - Charles Cobbs
- Swedish Neuroscience Institute, Swedish Medical Center, Seattle, WA 98122, USA
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37
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Warburton A, Miyajima F, Shazadi K, Crossley J, Johnson MR, Marson AG, Baker GA, Quinn JP, Sills GJ. NRSF and BDNF polymorphisms as biomarkers of cognitive dysfunction in adults with newly diagnosed epilepsy. Epilepsy Behav 2016; 54:117-27. [PMID: 26708060 PMCID: PMC4732989 DOI: 10.1016/j.yebeh.2015.11.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 11/09/2015] [Accepted: 11/14/2015] [Indexed: 12/31/2022]
Abstract
Cognitive dysfunction is a common comorbidity in people with epilepsy, but its causes remain unclear. It may be related to the etiology of the disorder, the consequences of seizures, or the effects of antiepileptic drug treatment. Genetics may also play a contributory role. We investigated the influence of variants in the genes encoding neuron-restrictive silencer factor (NRSF) and brain-derived neurotrophic factor (BDNF), proteins previously associated with cognition and epilepsy, on cognitive function in people with newly diagnosed epilepsy. A total of 82 patients who had previously undergone detailed neuropsychological assessment were genotyped for single nucleotide polymorphisms (SNPs) across the NRSF and BDNF genes. Putatively functional SNPs were included in a genetic association analysis with specific cognitive domains, including memory, psychomotor speed, and information processing. Cross-sectional and longitudinal designs were used to explore genetic influences on baseline cognition at diagnosis and change from baseline over the first year since diagnosis, respectively. We found a statistically significant association between genotypic variation and memory function at both baseline (NRSF: rs1105434, rs2227902 and BDNF: rs1491850, rs2030324, rs11030094) and in our longitudinal analysis (NRSF: rs2227902 and BDNF: rs12273363). Psychomotor speed was also associated with genotype (NRSF rs3796529) in the longitudinal assessment. In line with our previous work on general cognitive function in the healthy aging population, we observed an additive interaction between risk alleles for the NRSF rs2227902 (G) and BDNF rs6265 (A) polymorphisms which was again consistent with a significantly greater decline in delayed recall over the first year since diagnosis. These findings support a role for the NRSF-BDNF pathway in the modulation of cognitive function in patients with newly diagnosed epilepsy.
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Affiliation(s)
- Alix Warburton
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - Fabio Miyajima
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - Kanvel Shazadi
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - Joanne Crossley
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | | | - Anthony G Marson
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - Gus A Baker
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - John P Quinn
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK
| | - Graeme J Sills
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3GL, UK.
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38
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Abstract
Pancreas development is controlled by a complex interaction of signaling pathways and transcription factor networks that determine pancreatic specification and differentiation of exocrine and endocrine cells. Epigenetics adds a new layer of gene regulation. DNA methylation, histone modifications and non-coding RNAs recently appeared as important epigenetic factors regulating pancreas development. In this review, we report recent findings obtained by analyses in model organisms as well as genome-wide approaches that demonstrate the role of these epigenetic regulators in the control of exocrine and endocrine cell differentiation, identity, function, proliferation and regeneration. We also highlight how altered epigenetic processes contribute to pancreatic disorders: diabetes and pancreatic cancer. Uncovering these epigenetic events can help to better understand these diseases, provide novel therapeutical targets for their treatment, and improve cell-based therapies for diabetes.
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Affiliation(s)
- Evans Quilichini
- Centre National de la Recherche Scientifique (CNRS), UMR7622, Institut de Biologie Paris-Seine (IBPS), Paris F-75005, France; Sorbonne Universités, UPMC Université Paris 06, UMR7622-IBPS, Paris F-75005, France
| | - Cécile Haumaitre
- Centre National de la Recherche Scientifique (CNRS), UMR7622, Institut de Biologie Paris-Seine (IBPS), Paris F-75005, France; Sorbonne Universités, UPMC Université Paris 06, UMR7622-IBPS, Paris F-75005, France; Institut National de la Santé et de la Recherche Médicale (INSERM), France.
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39
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Durning SP, Flanagan-Steet H, Prasad N, Wells L. O-Linked β-N-acetylglucosamine (O-GlcNAc) Acts as a Glucose Sensor to Epigenetically Regulate the Insulin Gene in Pancreatic Beta Cells. J Biol Chem 2015; 291:2107-18. [PMID: 26598517 DOI: 10.1074/jbc.m115.693580] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Indexed: 11/06/2022] Open
Abstract
The post-translational protein modification O-linked β-N-acetylglucosamine (O-GlcNAc) is a proposed nutrient sensor that has been shown to regulate multiple biological pathways. This dynamic and inducible enzymatic modification to intracellular proteins utilizes the end product of the nutrient sensing hexosamine biosynthetic pathway, UDP-GlcNAc, as its substrate donor. Type II diabetic patients have elevated O-GlcNAc-modified proteins within pancreatic beta cells due to chronic hyperglycemia-induced glucose overload, but a molecular role for O-GlcNAc within beta cells remains unclear. Using directed pharmacological approaches in the mouse insulinoma-6 (Min6) cell line, we demonstrate that elevating nuclear O-GlcNAc increases intracellular insulin levels and preserves glucose-stimulated insulin secretion during chronic hyperglycemia. The molecular mechanism for these observed changes appears to be, at least in part, due to elevated O-GlcNAc-dependent increases in Ins1 and Ins2 mRNA levels via elevations in histone H3 transcriptional activation marks. Furthermore, RNA deep sequencing reveals that this mechanism of altered gene transcription is restricted and that the majority of genes regulated by elevated O-GlcNAc levels are similarly regulated by a shift from euglycemic to hyperglycemic conditions. These findings implicate the O-GlcNAc modification as a potential mechanism for hyperglycemic-regulated gene expression in the beta cell.
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Affiliation(s)
- Sean P Durning
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
| | - Heather Flanagan-Steet
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
| | - Nripesh Prasad
- HudsonAlpha Institute of Biotechnology, Genomic Services Laboratory, Huntsville, Alabama 35806
| | - Lance Wells
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
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40
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Abstract
Islets of Langerhans contain multiple hormone-producing endocrine cells controlling glucose homeostasis. Transcription establishes and maintains islet cellular fates and identities. Genetic and environmental disruption of islet transcription triggers cellular dysfunction and disease. Early transcriptional regulation studies of specific islet genes, including insulin (INS) and the transcription factor PDX1, identified the first cis-regulatory DNA sequences and trans-acting factors governing islet function. Here, we review how human islet "omics" studies are reshaping our understanding of transcriptional regulation in islet (dys)function and diabetes. First, we highlight the expansion of islet transcript number, form, and function and of DNA transcriptional regulatory elements controlling their production. Next, we cover islet transcriptional effects of genetic and environmental perturbation. Finally, we discuss how these studies' emerging insights should empower our diabetes research community to build mechanistic understanding of diabetes pathophysiology and to equip clinicians with tailored, precision medicine options to prevent and treat islet dysfunction and diabetes.
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Affiliation(s)
- Michael L Stitzel
- The Jackson Laboratory for Genomic Medicine (JAX-GM), Farmington, CT, USA,
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41
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Dayeh T, Ling C. Does epigenetic dysregulation of pancreatic islets contribute to impaired insulin secretion and type 2 diabetes? Biochem Cell Biol 2015; 93:511-21. [PMID: 26369706 DOI: 10.1139/bcb-2015-0057] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
β cell dysfunction is central to the development and progression of type 2 diabetes (T2D). T2D develops when β cells are not able to compensate for the increasing demand for insulin caused by insulin resistance. Epigenetic modifications play an important role in establishing and maintaining β cell identity and function in physiological conditions. On the other hand, epigenetic dysregulation can cause a loss of β cell identity, which is characterized by reduced expression of genes that are important for β cell function, ectopic expression of genes that are not supposed to be expressed in β cells, and loss of genetic imprinting. Consequently, this may lead to β cell dysfunction and impaired insulin secretion. Risk factors that can cause epigenetic dysregulation include parental obesity, an adverse intrauterine environment, hyperglycemia, lipotoxicity, aging, physical inactivity, and mitochondrial dysfunction. These risk factors can affect the epigenome at different time points throughout the lifetime of an individual and even before an individual is conceived. The plasticity of the epigenome enables it to change in response to environmental factors such as diet and exercise, and also makes the epigenome a good target for epigenetic drugs that may be used to enhance insulin secretion and potentially treat diabetes.
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Affiliation(s)
- Tasnim Dayeh
- Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Jan Waldenströms gata 35, CRC 91:12, 205 02 Malmö, Sweden.,Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Jan Waldenströms gata 35, CRC 91:12, 205 02 Malmö, Sweden
| | - Charlotte Ling
- Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Jan Waldenströms gata 35, CRC 91:12, 205 02 Malmö, Sweden.,Epigenetics and Diabetes Unit, Department of Clinical Sciences, Lund University Diabetes Centre, Jan Waldenströms gata 35, CRC 91:12, 205 02 Malmö, Sweden
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42
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Rönn T, Ling C. DNA methylation as a diagnostic and therapeutic target in the battle against Type 2 diabetes. Epigenomics 2015; 7:451-60. [DOI: 10.2217/epi.15.7] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Type 2 diabetes (T2D) develops due to insulin resistance and impaired insulin secretion, predominantly in genetically predisposed subjects exposed to nongenetic risk factors like obesity, physical inactivity and ageing. Emerging data suggest that epigenetics also play a key role in the pathogenesis of T2D. Genome-wide studies have identified altered DNA methylation patterns in pancreatic islets, skeletal muscle and adipose tissue from subjects with T2D compared with nondiabetic controls. Environmental factors known to affect T2D, including obesity, exercise and diet, have also been found to alter the human epigenome. Additionally, ageing and the intrauterine environment are associated with differential DNA methylation. Together, these data highlight a key role for epigenetics and particularly DNA methylation in the growing incidence of T2D.
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Affiliation(s)
- Tina Rönn
- Epigenetics & Diabetes, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund University, CRC, Jan Waldenströms gata 35, 205 02 Malmö, Sweden
| | - Charlotte Ling
- Epigenetics & Diabetes, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund University, CRC, Jan Waldenströms gata 35, 205 02 Malmö, Sweden
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43
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Haider SA, Faisal M. Human aging in the post-GWAS era: further insights reveal potential regulatory variants. Biogerontology 2015; 16:529-41. [PMID: 25895066 DOI: 10.1007/s10522-015-9575-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Accepted: 04/07/2015] [Indexed: 12/27/2022]
Abstract
Human aging involves a gradual decrease in cellular integrity that contributes to multiple complex disorders such as neurodegenerative disorders, cancer, diabetes, and cardiovascular diseases. Genome-wide association studies (GWAS) play a key role in discovering genetic variations that may contribute towards disease vulnerability. However, mostly disease-associated SNPs lie within non-coding part of the genome; majority of the variants are also present in linkage disequilibrium (LD) with the genome-wide significant SNPs (GWAS lead SNPs). Overall 600 SNPs were analyzed, out of which 291 returned RegulomeDB scores of 1-6. It was observed that just 4 out of those 291 SNPs show strong evidence of regulatory effects (RegulomeDB score <3), while none of them includes any GWAS lead SNP. Nevertheless, this study demonstrates that by combining ENCODE project data along with GWAS reported information will provide important insights on the impact of a genetic variant-moving from GWAS towards understanding disease pathways. It is noteworthy that both genome-wide significant SNPs as well as the SNPs in LD must be considered for future studies; this may prove to be crucial in deciphering the potential regulatory elements involved in complex disorders and aging in particular.
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Affiliation(s)
- Syed Aleem Haider
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, 45320, Pakistan
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44
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Epigenetic modifications and long noncoding RNAs influence pancreas development and function. Trends Genet 2015; 31:290-9. [PMID: 25812926 DOI: 10.1016/j.tig.2015.02.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 02/19/2015] [Accepted: 02/20/2015] [Indexed: 01/29/2023]
Abstract
Insulin-producing β cells within the pancreatic islet of Langerhans are responsible for maintaining glucose homeostasis; the loss or malfunction of β cells results in diabetes mellitus. Recent advances in cell purification strategies and sequencing technologies as well as novel molecular tools have revealed that epigenetic modifications and long noncoding RNAs (lncRNAs) represent an integral part of the transcriptional mechanisms regulating pancreas development and β cell function. Importantly, these findings have uncovered a new layer of gene regulation in the pancreas that can be exploited to enhance the restoration and/or repair of β cells to treat diabetes.
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45
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Togliatto G, Dentelli P, Brizzi MF. Skewed Epigenetics: An Alternative Therapeutic Option for Diabetes Complications. J Diabetes Res 2015; 2015:373708. [PMID: 26064979 PMCID: PMC4430641 DOI: 10.1155/2015/373708] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 04/07/2015] [Accepted: 04/22/2015] [Indexed: 12/21/2022] Open
Abstract
Vascular complications are major causes of morbidity and mortality in type 2 diabetes patients. Mitochondrial reactive oxygen species (ROS) generation and a lack of efficient antioxidant machinery, a result of hyperglycaemia, mainly contribute to this problem. Although advances in therapy have significantly reduced both morbidity and mortality in diabetic individuals, diabetes-associated vascular complications are still one of the most challenging health problems worldwide. New healing options are urgently needed as current therapeutics are failing to improve long-term outcomes. Particular effort has recently been devoted to understanding the functional relationship between chromatin structure regulation and the persistent change in gene expression which is driven by hyperglycaemia and which accounts for long-lasting diabetic complications. A detailed investigation into epigenetic chromatin modifications in type 2 diabetes is underway. This will be particularly useful in the design of mechanism-based therapeutics which interfere with long-lasting activating epigenetics and improve patient outcomes. We herein provide an overview of the most relevant mechanisms that account for hyperglycaemia-induced changes in chromatin structure; the most relevant mechanism is called "metabolic memory."
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Affiliation(s)
- Gabriele Togliatto
- Department of Medical Sciences, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy
| | - Patrizia Dentelli
- Department of Medical Sciences, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy
| | - Maria Felice Brizzi
- Department of Medical Sciences, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy
- *Maria Felice Brizzi:
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46
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Translational implications of the β-cell epigenome in diabetes mellitus. Transl Res 2015; 165:91-101. [PMID: 24686035 PMCID: PMC4162854 DOI: 10.1016/j.trsl.2014.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/04/2014] [Accepted: 03/06/2014] [Indexed: 12/12/2022]
Abstract
Diabetes mellitus is a disorder of glucose homeostasis that affects more than 24 million Americans and 382 million individuals worldwide. Dysregulated insulin secretion from the pancreatic β cells plays a central role in the pathophysiology of all forms of diabetes mellitus. Therefore, an enhanced understanding of the pathways that contribute to β-cell failure is imperative. Epigenetics refers to heritable changes in DNA transcription that occur in the absence of changes to the linear DNA nucleotide sequence. Recent evidence suggests an expanding role of the β-cell epigenome in the regulation of metabolic health. The goal of this review is to discuss maladaptive changes in β-cell DNA methylation patterns and chromatin architecture, and their contribution to diabetes pathophysiology. Efforts to modulate the β-cell epigenome as a means to prevent, diagnose, and treat diabetes are also discussed.
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47
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Thomsen SK, Gloyn AL. The pancreatic β cell: recent insights from human genetics. Trends Endocrinol Metab 2014; 25:425-34. [PMID: 24986330 PMCID: PMC4229643 DOI: 10.1016/j.tem.2014.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/02/2014] [Accepted: 05/07/2014] [Indexed: 12/14/2022]
Abstract
Diabetes mellitus is a metabolic disease characterised by relative or absolute pancreatic β cell dysfunction. Genetic variants implicated in disease risk can be identified by studying affected individuals. To understand the mechanisms driving genetic associations, variants must be translated through causative transcripts to biological insights. Studies into the genetic basis of Mendelian forms of diabetes have successfully identified genes involved in both β cell function and pancreatic development. For type 2 diabetes (T2D), genome-wide association studies (GWASs) are uncovering an ever-increasing number of susceptibility variants that exert their effect through β cell dysfunction, but translation to mechanistic understanding has in most cases been slow. Improved annotations of the islet genome and advances in whole-genome and -exome sequencing (WHS and WES) have facilitated recent progress.
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Affiliation(s)
- Soren K Thomsen
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, University of Oxford, Headington, OX3 7LE, UK
| | - Anna L Gloyn
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, University of Oxford, Headington, OX3 7LE, UK; Oxford National Institute for Health Research (NIHR) Biomedical Research Centre, Churchill Hospital, Headington, OX3 7LE, UK.
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48
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Bahar Halpern K, Vana T, Walker MD. Paradoxical role of DNA methylation in activation of FoxA2 gene expression during endoderm development. J Biol Chem 2014; 289:23882-92. [PMID: 25016019 DOI: 10.1074/jbc.m114.573469] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor FoxA2 is a master regulator of endoderm development and pancreatic beta cell gene expression. To elucidate the mechanisms underlying the activation of the FoxA2 gene during differentiation, we have compared the epigenetic status of undifferentiated human embryonic stem cells (hESCs), hESC-derived early endoderm stage cells (CXCR4+ cells), and pancreatic islet cells. Unexpectedly, a CpG island in the promoter region of the FoxA2 gene displayed paradoxically high levels of DNA methylation in expressing tissues (CXCR4+, islets) and low levels in nonexpressing tissues. This CpG island region was found to repress reporter gene expression and bind the Polycomb group protein SUZ12 and the DNA methyltransferase (DNMT)3b preferentially in undifferentiated hESCs as compared with CXCR4+ or islets cells. Consistent with this, activation of FoxA2 gene expression, but not CXCR4 or SOX17, was strongly inhibited by 5-aza-2'-deoxycytidine and by knockdown of DNMT3b. We hypothesize that in nonexpressing tissues, the lack of DNA methylation allows the binding of DNA methyltransferases and repressing proteins, such as Polycomb group proteins; upon differentiation, DNMT activation leads to CpG island methylation, causing loss of repressor protein binding. These results suggest a novel and unexpected role for DNA methylation in the activation of FoxA2 gene expression during differentiation.
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Affiliation(s)
- Keren Bahar Halpern
- From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tal Vana
- From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Michael D Walker
- From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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49
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Esguerra JLS, Eliasson L. Functional implications of long non-coding RNAs in the pancreatic islets of Langerhans. Front Genet 2014; 5:209. [PMID: 25071836 PMCID: PMC4083688 DOI: 10.3389/fgene.2014.00209] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/19/2014] [Indexed: 12/14/2022] Open
Abstract
Type-2 diabetes (T2D) is a complex disease characterized by insulin resistance in target tissues and impaired insulin release from pancreatic beta cells. As central tissue of glucose homeostasis, the pancreatic islet continues to be an important focus of research to understand the pathophysiology of the disease. The increased access to human pancreatic islets has resulted in improved knowledge of islet function, and together with advances in RNA sequencing and related technologies, revealed the transcriptional and epigenetic landscape of human islet cells. The discovery of thousands of long non-coding RNA (lncRNA) transcripts highly enriched in the pancreatic islet and/or specifically expressed in the beta-cells, points to yet another layer of gene regulation of many hitherto unknown mechanistic principles governing islet cell functions. Here we review fundamental islet physiology and propose functional implications of the lncRNAs in islet development and endocrine cell functions. We also take into account important differences between rodent and human islets in terms of morphology and function, and suggest how species-specific lncRNAs may partly influence gene regulation to define the unique phenotypic identity of an organism and the functions of its constituent cells. The implication of primate-specific lncRNAs will be far-reaching in all aspects of diabetes research, but most importantly in the identification and development of novel targets to improve pancreatic islet cell functions as a therapeutic approach to treat T2D.
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Affiliation(s)
- Jonathan L S Esguerra
- Islet Cell Exocytosis, Department of Clinical Sciences-Malmö, Lund University Diabetes Centre, Lund University Malmö, Sweden
| | - Lena Eliasson
- Islet Cell Exocytosis, Department of Clinical Sciences-Malmö, Lund University Diabetes Centre, Lund University Malmö, Sweden
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50
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Koufariotis L, Chen YPP, Bolormaa S, Hayes BJ. Regulatory and coding genome regions are enriched for trait associated variants in dairy and beef cattle. BMC Genomics 2014; 15:436. [PMID: 24903263 PMCID: PMC4070550 DOI: 10.1186/1471-2164-15-436] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 05/22/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In livestock, as in humans, the number of genetic variants that can be tested for association with complex quantitative traits, or used in genomic predictions, is increasing exponentially as whole genome sequencing becomes more common. The power to identify variants associated with traits, particularly those of small effects, could be increased if certain regions of the genome were known a priori to be enriched for associations. Here, we investigate whether twelve genomic annotation classes were enriched or depleted for significant associations in genome wide association studies for complex traits in beef and dairy cattle. We also describe a variance component approach to determine the proportion of genetic variance captured by each annotation class. RESULTS P-values from large GWAS using 700K SNP in both dairy and beef cattle were available for 11 and 10 traits respectively. We found significant enrichment for trait associated variants (SNP significant in the GWAS) in the missense class along with regions 5 kilobases upstream and downstream of coding genes. We found that the non-coding conserved regions (across mammals) were not enriched for trait associated variants. The results from the enrichment or depletion analysis were not in complete agreement with the results from variance component analysis, where the missense and synonymous classes gave the greatest increase in variance explained, while the upstream and downstream classes showed a more modest increase in the variance explained. CONCLUSION Our results indicate that functional annotations could assist in prioritization of variants to a subset more likely to be associated with complex traits; including missense variants, and upstream and downstream regions. The differences in two sets of results (GWAS enrichment depletion versus variance component approaches) might be explained by the fact that the variance component approach has greater power to capture the cumulative effect of mutations of small effect, while the enrichment or depletion approach only captures the variants that are significant in GWAS, which is restricted to a limited number of common variants of moderate effects.
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Affiliation(s)
- Lambros Koufariotis
- Faculty of Science, Technology and Engineering, La Trobe University, Melbourne, Victoria 3086, Australia.
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