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Balasooriya GI, Wee TL, Spector DL. A sub-set of guanine- and cytosine-rich genes are actively transcribed at the nuclear Lamin B1 region. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.28.564411. [PMID: 37961255 PMCID: PMC10634887 DOI: 10.1101/2023.10.28.564411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Chromatin organization in the mammalian cell nucleus plays a vital role in the regulation of gene expression. The lamina-associated domain at the inner nuclear membrane has been proposed to harbor heterochromatin, while the nuclear interior has been shown to contain most of the euchromatin. Here, we show that a sub-set of actively transcribing genes, marked by RNA Pol II pSer2, are associated with Lamin B1 at the inner nuclear envelop in mESCs and the number of genes proportionally increases upon in vitro differentiation of mESC to olfactory precursor cells. These nuclear periphery-associated actively transcribing genes primarily represent housekeeping genes, and their gene bodies are significantly enriched with guanine and cytosine compared to genes actively transcribed at the nuclear interior. We found the promoters of these genes to also be significantly enriched with guanine and to be predominantly regulated by zinc finger protein transcription factors. We provide evidence supporting the emerging notion that the Lamin B1 region is not solely transcriptionally silent.
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Lu J, Li XQ, Chen PP, Zhang JX, Liu L, Wang GH, Liu XQ, Jiang TT, Wang MY, Liu WT, Ruan XZ, Ma KL. Activation of acetyl-CoA synthetase 2 mediates kidney injury in diabetic nephropathy. JCI Insight 2023; 8:e165817. [PMID: 37870960 PMCID: PMC10619493 DOI: 10.1172/jci.insight.165817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 09/05/2023] [Indexed: 10/25/2023] Open
Abstract
Albuminuria and podocyte injury are the key cellular events in the progression of diabetic nephropathy (DN). Acetyl-CoA synthetase 2 (ACSS2) is a nucleocytosolic enzyme responsible for the regulation of metabolic homeostasis in mammalian cells. This study aimed to investigate the possible roles of ACSS2 in kidney injury in DN. We constructed an ACSS2-deleted mouse model to investigate the role of ACSS2 in podocyte dysfunction and kidney injury in diabetic mouse models. In vitro, podocytes were chosen and transfected with ACSS2 siRNA and ACSS2 inhibitor and treated with high glucose. We found that ACSS2 expression was significantly elevated in the podocytes of patients with DN and diabetic mice. ACSS2 upregulation promoted phenotype transformation and inflammatory cytokine expression while inhibiting podocytes' autophagy. Conversely, ACSS2 inhibition improved autophagy and alleviated podocyte injury. Furthermore, ACSS2 epigenetically activated raptor expression by histone H3K9 acetylation, promoting activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway. Pharmacological inhibition or genetic depletion of ACSS2 in the streptozotocin-induced diabetic mouse model greatly ameliorated kidney injury and podocyte dysfunction. To conclude, ACSS2 activation promoted podocyte injury in DN by raptor/mTORC1-mediated autophagy inhibition.
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Affiliation(s)
- Jian Lu
- Department of Nephrology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Xue Qi Li
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Pei Pei Chen
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Jia Xiu Zhang
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Liang Liu
- Department of Intensive Care Unit, People’s Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Gui Hua Wang
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Xiao Qi Liu
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Ting Ting Jiang
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Meng Ying Wang
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Wen Tao Liu
- Institute of Nephrology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, China
| | - Xiong Zhong Ruan
- John Moorhead Research Laboratory, Department of Renal Medicine, University College London Medical School, Royal Free Campus, London, United Kingdom
| | - Kun Ling Ma
- Department of Nephrology, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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Prakhar P, Bhatt B, Lohia GK, Shah A, Mukherjee T, Kolthur-Seetharam U, Sundaresan NR, Rajmani RS, Balaji KN. G9a and Sirtuin6 epigenetically modulate host cholesterol accumulation to facilitate mycobacterial survival. PLoS Pathog 2023; 19:e1011731. [PMID: 37871034 PMCID: PMC10621959 DOI: 10.1371/journal.ppat.1011731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/02/2023] [Accepted: 10/02/2023] [Indexed: 10/25/2023] Open
Abstract
Cholesterol derived from the host milieu forms a critical factor for mycobacterial pathogenesis. However, the molecular circuitry co-opted by Mycobacterium tuberculosis (Mtb) to accumulate cholesterol in host cells remains obscure. Here, we report that the coordinated action of WNT-responsive histone modifiers G9a (H3K9 methyltransferase) and SIRT6 (H3K9 deacetylase) orchestrate cholesterol build-up in in vitro and in vivo mouse models of Mtb infection. Mechanistically, G9a, along with SREBP2, drives the expression of cholesterol biosynthesis and uptake genes; while SIRT6 along with G9a represses the genes involved in cholesterol efflux. The accumulated cholesterol in Mtb infected macrophages promotes the expression of antioxidant genes leading to reduced oxidative stress, thereby supporting Mtb survival. In corroboration, loss-of-function of G9a in vitro and pharmacological inhibition in vivo; or utilization of BMDMs derived from Sirt6-/- mice or in vivo infection in haplo-insufficient Sirt6-/+ mice; hampered host cholesterol accumulation and restricted Mtb burden. These findings shed light on the novel roles of G9a and SIRT6 during Mtb infection and highlight the previously unknown contribution of host cholesterol in potentiating anti-oxidative responses for aiding Mtb survival.
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Affiliation(s)
- Praveen Prakhar
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Bharat Bhatt
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Gaurav Kumar Lohia
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Awantika Shah
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Tanushree Mukherjee
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Ullas Kolthur-Seetharam
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra, India
| | - Nagalingam R. Sundaresan
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Raju S. Rajmani
- Centre for Infectious Disease Research, Indian Institute of Science, Bangalore–, Karnataka, India
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4
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Mukherjee T, Bhatt B, Prakhar P, Lohia GK, Rajmani R, Balaji KN. Epigenetic reader BRD4 supports mycobacterial pathogenesis by co-modulating host lipophagy and angiogenesis. Autophagy 2022; 18:391-408. [PMID: 34074211 PMCID: PMC8942508 DOI: 10.1080/15548627.2021.1936355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 05/23/2021] [Accepted: 05/26/2021] [Indexed: 10/21/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb)-driven lipid accumulation is intricately associated with the progression of tuberculosis (TB) disease. Although several studies elucidating the mechanisms for lipid droplet (LD) biosynthesis exist, we provide evidence for the significance of their regulated turnover via macroautophagy/autophagy during Mtb infection. We demonstrate that Mtb utilizes EGFR (epidermal growth factor receptor) signaling to induce the expression of the histone acetylation reader, BRD4 (bromodomain containing 4). The EGFR-BRD4 axis suppresses lipid-specific autophagy, and hence favors cellular lipid accumulation. Specifically, we found that pharmacological inhibition or knockdown of Egfr or Brd4 enhances autophagic flux and concomitantly decreases cellular LDs that is otherwise maintained at a significant level in chloroquine-treated or Atg5 knocked down autophagy-compromised host cells. In line with the enhanced lipophagy, we found that loss of EGFR or BRD4 function restricts mycobacterial burden that is rescued by external replenishment with oleic acid. We also report that the EGFR-BRD4 axis exerts additional effects by modulating pro-angiogenic gene expression and consequently aberrant angiogenesis during mycobacterial infection. This is important in the context of systemic Mtb dissemination as well as for the efficient delivery of anti-mycobacterial therapeutics to the Mtb-rich core of TB granuloma. Finally, utilizing an in vivo mouse model of TB, we show that pharmacological inhibition of EGFR and BRD4 compromises LD buildup via enhanced lipophagy and normalizes angiogenesis, thereby restricting Mtb burden and rescuing mice from severe TB-like pathology. These findings shed light on the novel roles of BRD4 during Mtb infection, and its possible implication in potentiating anti-TB responses.Abbreviations: ATG5: autophagy related 5; BRDs: bromodomain containing; COL18A1: collagen type XVIII alpha 1 chain; EGFR: epidermal growth factor receptor; EP300: E1A binding protein p300; KDR: kinase insert domain receptor; KLF5: Kruppel like factor 5; LDs: lipid droplets; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; Mtb: Mycobacterium tuberculosis; PECAM1: platelet and endothelial cell adhesion molecule 1; SQSTM1/p62: sequestosome 1; TB: tuberculosis; THBS1: thrombospondin 1; VEGF: vascular endothelial growth factor.
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Affiliation(s)
- Tanushree Mukherjee
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - Bharat Bhatt
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - Praveen Prakhar
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - Gaurav Kumar Lohia
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - R.S. Rajmani
- Centre for Infectious Disease Research, Indian Institute of Science, Bengaluru, India
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5
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Abstract
Chromatin immunoprecipitation, commonly referred to as ChIP, is a powerful technique for the evaluation of in vivo interactions of proteins with specific regions of genomic DNA. Formaldehyde is used in this technique to cross-link proteins to DNA in vivo, followed by the extraction of chromatin from cross-linked cells and tissues. Harvested chromatin is sheared and subsequently used in an immunoprecipitation incorporating antibodies specific to protein(s) of interest and thus coprecipitating and enriching the cross-linked, protein-associated DNA. The cross-linking process can be reversed, and protein-bound DNA fragments of optimal length ranging from 200 to 1000 base pairs (bp) can subsequently be purified and measured or sequenced by numerous analytical methods. In this protocol, two different fixation methods are described in detail. The first involves the standard fixation of cells and tissue by formaldehyde if the target antigen is highly abundant. The dual cross-linking procedure presented at the end includes an additional preformaldehyde cross-linking step and can be especially useful when the target protein is in low abundance or if it is indirectly associated with chromatin DNA through another protein.
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Abstract
Hundreds of distinct chemical modifications to DNA and histone amino acids have been described. Regulation exerted by these so-called epigenetic marks is vital to normal development, stability of cell identity through mitosis, and nongenetic transmission of traits between generations through meiosis. Loss of this regulation contributes to many diseases. Evidence indicates epigenetic marks function in combinations, whereby a given modification has distinct effects on local genome control, depending on which additional modifications are locally present. This review summarizes emerging methods for assessing combinatorial epigenomic states, as well as challenges and opportunities for their refinement.
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Affiliation(s)
- Paul D. Soloway
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, United States
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7
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Schmid M, Smith J, Burt DW, Aken BL, Antin PB, Archibald AL, Ashwell C, Blackshear PJ, Boschiero C, Brown CT, Burgess SC, Cheng HH, Chow W, Coble DJ, Cooksey A, Crooijmans RPMA, Damas J, Davis RVN, de Koning DJ, Delany ME, Derrien T, Desta TT, Dunn IC, Dunn M, Ellegren H, Eöry L, Erb I, Farré M, Fasold M, Fleming D, Flicek P, Fowler KE, Frésard L, Froman DP, Garceau V, Gardner PP, Gheyas AA, Griffin DK, Groenen MAM, Haaf T, Hanotte O, Hart A, Häsler J, Hedges SB, Hertel J, Howe K, Hubbard A, Hume DA, Kaiser P, Kedra D, Kemp SJ, Klopp C, Kniel KE, Kuo R, Lagarrigue S, Lamont SJ, Larkin DM, Lawal RA, Markland SM, McCarthy F, McCormack HA, McPherson MC, Motegi A, Muljo SA, Münsterberg A, Nag R, Nanda I, Neuberger M, Nitsche A, Notredame C, Noyes H, O'Connor R, O'Hare EA, Oler AJ, Ommeh SC, Pais H, Persia M, Pitel F, Preeyanon L, Prieto Barja P, Pritchett EM, Rhoads DD, Robinson CM, Romanov MN, Rothschild M, Roux PF, Schmidt CJ, Schneider AS, Schwartz MG, Searle SM, Skinner MA, Smith CA, Stadler PF, Steeves TE, Steinlein C, Sun L, Takata M, Ulitsky I, Wang Q, Wang Y, Warren WC, Wood JMD, Wragg D, Zhou H. Third Report on Chicken Genes and Chromosomes 2015. Cytogenet Genome Res 2015; 145:78-179. [PMID: 26282327 PMCID: PMC5120589 DOI: 10.1159/000430927] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Michael Schmid
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
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Pillai S, Dasgupta P, Chellappan SP. Chromatin immunoprecipitation assays: analyzing transcription factor binding and histone modifications in vivo. Methods Mol Biol 2015; 1288:429-46. [PMID: 25827895 DOI: 10.1007/978-1-4939-2474-5_25] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Studies in the past decade have shown that differential gene expression depends not only on the binding of specific transcription factors to discrete promoter elements but also on the epigenetic modification of the DNA as well as histones associated with the promoter. While techniques like electrophoretic mobility shift assays could detect and characterize the binding of specific transcription factors present in cell lysates to DNA sequences in in vitro binding conditions, they were not effective in assessing the binding in intact cells. Development of chromatin immunoprecipitation technique in the past decade enabled the analysis of the association of regulatory molecules with specific promoters or changes in histone modifications in vivo, without overexpressing any component. ChIP assays can provide a snapshot of how a regulatory transcription factor affects the expression of a single gene, or a variety of genes at the same time. Availability of high quality antibodies that recognizes histones modified in a specific fashion further expanded the use of ChIP assays to analyze even minute changes in histone modification and nucleosomes structure. This chapter outlines the general strategies and protocols used to carry out ChIP assays to study the differential recruitment of transcription factors as well as histone modifications.
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Affiliation(s)
- Smitha Pillai
- Department of Tumor Biology, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL, 33612, USA
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9
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Hyun BR, McElwee JL, Soloway PD. Single molecule and single cell epigenomics. Methods 2014; 72:41-50. [PMID: 25204781 DOI: 10.1016/j.ymeth.2014.08.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 08/19/2014] [Accepted: 08/27/2014] [Indexed: 01/24/2023] Open
Abstract
Dynamically regulated changes in chromatin states are vital for normal development and can produce disease when they go awry. Accordingly, much effort has been devoted to characterizing these states under normal and pathological conditions. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is the most widely used method to characterize where in the genome transcription factors, modified histones, modified nucleotides and chromatin binding proteins are found; bisulfite sequencing (BS-seq) and its variants are commonly used to characterize the locations of DNA modifications. Though very powerful, these methods are not without limitations. Notably, they are best at characterizing one chromatin feature at a time, yet chromatin features arise and function in combination. Investigators commonly superimpose separate ChIP-seq or BS-seq datasets, and then infer where chromatin features are found together. While these inferences might be correct, they can be misleading when the chromatin source has distinct cell types, or when a given cell type exhibits any cell to cell variation in chromatin state. These ambiguities can be eliminated by robust methods that directly characterize the existence and genomic locations of combinations of chromatin features in very small inputs of cells or ideally, single cells. Here we review single molecule epigenomic methods under development to overcome these limitations, the technical challenges associated with single molecule methods and their potential application to single cells.
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Affiliation(s)
- Byung-Ryool Hyun
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - John L McElwee
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Paul D Soloway
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
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10
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Lin CL, Lee PH, Hsu YC, Lei CC, Ko JY, Chuang PC, Huang YT, Wang SY, Wu SL, Chen YS, Chiang WC, Reiser J, Wang FS. MicroRNA-29a promotion of nephrin acetylation ameliorates hyperglycemia-induced podocyte dysfunction. J Am Soc Nephrol 2014; 25:1698-709. [PMID: 24578127 DOI: 10.1681/asn.2013050527] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Podocyte dysfunction is a detrimental feature in diabetic nephropathy, with loss of nephrin integrity contributing to diabetic podocytopathy. MicroRNAs (miRs) reportedly modulate the hyperglycemia-induced perturbation of renal tissue homeostasis. This study investigated whether regulation of histone deacetylase (HDAC) actions and nephrin acetylation by miR-29 contributes to podocyte homeostasis and renal function in diabetic kidneys. Hyperglycemia accelerated podocyte injury and reduced nephrin, acetylated nephrin, and miR-29a levels in primary renal glomeruli from streptozotocin-induced diabetic mice. Diabetic miR-29a transgenic mice had better nephrin levels, podocyte viability, and renal function and less glomerular fibrosis and inflammation reaction compared with diabetic wild-type mice. Overexpression of miR-29a attenuated the promotion of HDAC4 signaling, nephrin ubiquitination, and urinary nephrin excretion associated with diabetes and restored nephrin acetylation. Knockdown of miR-29a by antisense oligonucleotides promoted HDAC4 action, nephrin loss, podocyte apoptosis, and proteinuria in nondiabetic mice. In vitro, interruption of HDAC4 signaling alleviated the high glucose-induced apoptosis and inhibition of nephrin acetylation in podocyte cultures. Furthermore, HDAC4 interference increased the acetylation status of histone H3 at lysine 9 (H3K9Ac), the enrichment of H3K9Ac in miR-29a proximal promoter, and miR-29a transcription in high glucose-stressed podocytes. In conclusion, hyperglycemia impairs miR-29a signaling to intensify HDAC4 actions that contribute to podocyte protein deacetylation and degradation as well as renal dysfunction. HDAC4, via epigenetic H3K9 hypoacetylation, reduces miR-29a transcription. The renoprotective effects of miR-29a in diabetes-induced loss of podocyte integrity and renal homeostasis highlights the importance of post-translational acetylation reactions in podocyte microenvironments. Increasing miR-29a action may protect against diabetic podocytopathy.
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Affiliation(s)
- Chun-Liang Lin
- Department of Nephrology and Kidney and Diabetic Complications Research Team, Chang Gung Memorial Hospital, Chiayi, Taiwan; Kidney Research Center, Chang Gung Memorial Hospital, Taipei, Taiwan; School of Traditional Chinese Medicine and
| | - Pei-Hsien Lee
- Department of Nephrology and Kidney and Diabetic Complications Research Team, Chang Gung Memorial Hospital, Chiayi, Taiwan
| | - Yung-Chien Hsu
- Department of Nephrology and Kidney and Diabetic Complications Research Team, Chang Gung Memorial Hospital, Chiayi, Taiwan
| | - Chen-Chou Lei
- Department of Nephrology and Kidney and Diabetic Complications Research Team, Chang Gung Memorial Hospital, Chiayi, Taiwan
| | - Jih-Yang Ko
- Departments of Orthopedic Surgery and Center for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan
| | | | | | | | | | | | - Wen-Chih Chiang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, Illinois; and
| | - Feng-Sheng Wang
- Center for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Medical Research and Graduate Institute of Clinical Medical Science, Chang Gung University College of Medicine, TaoYuan, Taiwan
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11
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Ko JY, Chuang PC, Chen MW, Ke HC, Wu SL, Chang YH, Chen YS, Wang FS. MicroRNA-29a ameliorates glucocorticoid-induced suppression of osteoblast differentiation by regulating β-catenin acetylation. Bone 2013; 57:468-75. [PMID: 24096265 DOI: 10.1016/j.bone.2013.09.019] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/20/2013] [Accepted: 09/24/2013] [Indexed: 02/07/2023]
Abstract
Excess glucocorticoid treatment induces loss of osteoblast differentiation. Post-translational modification of β-catenin reportedly regulates osteogenic activities in bone cells. This study was undertaken to test whether miR-29a signaling regulates the acetylation status of β-catenin in the glucocorticoid-mediated osteoblast dysfunction. Murine osteoblast cultures were incubated under osteogenic conditions with or without supraphysiological glucocorticoid, miR-29a precursor, antisense oligonucleotides or histone deacetylase 4 (HDAC4) RNA interferences. Osteoblast differentiation was determined by alkaline phosphatase activity, calcium deposition, and von Kossa stain. β-Catenin acetylation and miR-29a transcription were detected by immunoblotting, chromatin immunoprecipitation and quantitative PCR. Protein interaction was detected by fluorescence protein ligation assay. Supraphysiological glucocorticoid treatment repressed osteoblast differentiation and induced loss of miR-29a expression and acetylated β-catenin levels in osteoblast cultures. Gain of miR-29a function attenuated the deleterious effects of glucocorticoid on osteogenic gene expression and mineralized nodule formation, whereas knockdown of miR-29a signaling accelerated loss of osteoblast differentiation capacity. miR-29a reduced HDAC4 signaling and attenuated the glucocorticoid-mediated β-catenin deacetylation and ubiquitination and restored nuclear β-catenin levels. Glucocorticoid-induced loss of miR-29a signaling occurred through transcriptional and translational regulation. Interruption of HDAC4 signaling attenuated the glucocorticoid-induced hypoacetylation of histone H3 at lysine 9 (H3K9Ac) and restored the enrichment of H3K9Ac in miR-29a proximal promoter region and miR-29a transcription in cell cultures. Taken together, excess glucocorticoid-induced loss of miR-29a signaling accelerates β-catenin deacetylation and ubiquitination that impairs osteogenic activities of osteoblast cultures. miR-29a and HDAC4 reciprocal regulation of H3K9 acetylation contributes to the acetylation status of β-catenin and miR-29a expression. Enhancement of miR-29a signaling is an alternative strategy for protecting against the adverse actions of excess glucocorticoid on differentiation capacity of osteogenic cells.
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Affiliation(s)
- Jih-Yang Ko
- Department of Orthopedic Surgery, Kaohsiung Chang Gung Memorial Hospital, Taiwan; Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Taiwan
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