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Wanigasuriya I, Kinkel SA, Beck T, Roper EA, Breslin K, Lee HJ, Keniry A, Ritchie ME, Blewitt ME, Gouil Q. Maternal SMCHD1 controls both imprinted Xist expression and imprinted X chromosome inactivation. Epigenetics Chromatin 2022; 15:26. [PMID: 35843975 PMCID: PMC9290310 DOI: 10.1186/s13072-022-00458-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 06/21/2022] [Indexed: 12/13/2022] Open
Abstract
Embryonic development is dependent on the maternal supply of proteins through the oocyte, including factors setting up the adequate epigenetic patterning of the zygotic genome. We previously reported that one such factor is the epigenetic repressor SMCHD1, whose maternal supply controls autosomal imprinted expression in mouse preimplantation embryos and mid-gestation placenta. In mouse preimplantation embryos, X chromosome inactivation is also an imprinted process. Combining genomics and imaging, we show that maternal SMCHD1 is required not only for the imprinted expression of Xist in preimplantation embryos, but also for the efficient silencing of the inactive X in both the preimplantation embryo and mid-gestation placenta. These results expand the role of SMCHD1 in enforcing the silencing of Polycomb targets. The inability of zygotic SMCHD1 to fully restore imprinted X inactivation further points to maternal SMCHD1’s role in setting up the appropriate chromatin environment during preimplantation development, a critical window of epigenetic remodelling.
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Affiliation(s)
- Iromi Wanigasuriya
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Sarah A Kinkel
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Tamara Beck
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Ellise A Roper
- The School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, Australia
| | - Kelsey Breslin
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Heather J Lee
- The School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, Australia
| | - Andrew Keniry
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Matthew E Ritchie
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia.,The Department of Mathematics and Statistics, The University of Melbourne, Parkville, Australia
| | - Marnie E Blewitt
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia. .,The Department of Medical Biology, The University of Melbourne, Parkville, Australia.
| | - Quentin Gouil
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia. .,The Department of Medical Biology, The University of Melbourne, Parkville, Australia.
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2
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Wanigasuriya I, Gouil Q, Kinkel SA, Tapia Del Fierro A, Beck T, Roper EA, Breslin K, Stringer J, Hutt K, Lee HJ, Keniry A, Ritchie ME, Blewitt ME. Smchd1 is a maternal effect gene required for genomic imprinting. eLife 2020; 9:55529. [PMID: 33186096 PMCID: PMC7665889 DOI: 10.7554/elife.55529] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 10/26/2020] [Indexed: 12/17/2022] Open
Abstract
Genomic imprinting establishes parental allele-biased expression of a suite of mammalian genes based on parent-of-origin specific epigenetic marks. These marks are under the control of maternal effect proteins supplied in the oocyte. Here we report epigenetic repressor Smchd1 as a novel maternal effect gene that regulates the imprinted expression of ten genes in mice. We also found zygotic SMCHD1 had a dose-dependent effect on the imprinted expression of seven genes. Together, zygotic and maternal SMCHD1 regulate three classic imprinted clusters and eight other genes, including non-canonical imprinted genes. Interestingly, the loss of maternal SMCHD1 does not alter germline DNA methylation imprints pre-implantation or later in gestation. Instead, what appears to unite most imprinted genes sensitive to SMCHD1 is their reliance on polycomb-mediated methylation as germline or secondary imprints, therefore we propose that SMCHD1 acts downstream of polycomb imprints to mediate its function.
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Affiliation(s)
- Iromi Wanigasuriya
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Quentin Gouil
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Sarah A Kinkel
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Andrés Tapia Del Fierro
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Tamara Beck
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
| | - Ellise A Roper
- Faculty of Health and Medicine, The University of Newcastle, Newcastle, Australia
| | - Kelsey Breslin
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
| | - Jessica Stringer
- Monash Biomedicine Discovery institute, Monash University, Clayton, Australia
| | - Karla Hutt
- Monash Biomedicine Discovery institute, Monash University, Clayton, Australia
| | - Heather J Lee
- Faculty of Health and Medicine, The University of Newcastle, Newcastle, Australia
| | - Andrew Keniry
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Matthew E Ritchie
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia.,The Department of Mathematics and Statistics, The University of Melbourne, Parkville, Australia
| | - Marnie E Blewitt
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,The Department of Medical Biology, The University of Melbourne, Parkville, Australia
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3
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Keniry A, Gearing LJ, Jansz N, Liu J, Holik AZ, Hickey PF, Kinkel SA, Moore DL, Breslin K, Chen K, Liu R, Phillips C, Pakusch M, Biben C, Sheridan JM, Kile BT, Carmichael C, Ritchie ME, Hilton DJ, Blewitt ME. Setdb1-mediated H3K9 methylation is enriched on the inactive X and plays a role in its epigenetic silencing. Epigenetics Chromatin 2016; 9:16. [PMID: 27195021 PMCID: PMC4870784 DOI: 10.1186/s13072-016-0064-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/31/2016] [Indexed: 11/16/2022] Open
Abstract
Background
The presence of histone 3 lysine 9 (H3K9) methylation on the mouse inactive X chromosome has been controversial over the last 15 years, and the functional role of H3K9 methylation in X chromosome inactivation in any species has remained largely unexplored. Results Here we report the first genomic analysis of H3K9 di- and tri-methylation on the inactive X: we find they are enriched at the intergenic, gene poor regions of the inactive X, interspersed between H3K27 tri-methylation domains found in the gene dense regions. Although H3K9 methylation is predominantly non-genic, we find that depletion of H3K9 methylation via depletion of H3K9 methyltransferase Set domain bifurcated 1 (Setdb1) during the establishment of X inactivation, results in failure of silencing for around 150 genes on the inactive X. By contrast, we find a very minor role for Setdb1-mediated H3K9 methylation once X inactivation is fully established. In addition to failed gene silencing, we observed a specific failure to silence X-linked long-terminal repeat class repetitive elements. Conclusions Here we have shown that H3K9 methylation clearly marks the murine inactive X chromosome. The role of this mark is most apparent during the establishment phase of gene silencing, with a more muted effect on maintenance of the silent state. Based on our data, we hypothesise that Setdb1-mediated H3K9 methylation plays a role in epigenetic silencing of the inactive X via silencing of the repeats, which itself facilitates gene silencing through alterations to the conformation of the whole inactive X chromosome. Electronic supplementary material The online version of this article (doi:10.1186/s13072-016-0064-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Andrew Keniry
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Linden J Gearing
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Natasha Jansz
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Joy Liu
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia
| | - Aliaksei Z Holik
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Peter F Hickey
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Mathematics and Statistics, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Sarah A Kinkel
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Darcy L Moore
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Kelsey Breslin
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia
| | - Kelan Chen
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Ruijie Liu
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia
| | - Catherine Phillips
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia
| | - Miha Pakusch
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia
| | - Christine Biben
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Julie M Sheridan
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Benjamin T Kile
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Catherine Carmichael
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Matthew E Ritchie
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia.,Department of Mathematics and Statistics, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Douglas J Hilton
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia
| | - Marnie E Blewitt
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052 Australia.,Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010 Australia.,Department of Genetics, University of Melbourne, Melbourne, VIC 3010 Australia
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4
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Flensburg C, Kinkel SA, Keniry A, Blewitt ME, Oshlack A. A comparison of control samples for ChIP-seq of histone modifications. Front Genet 2014; 5:329. [PMID: 25309581 PMCID: PMC4174756 DOI: 10.3389/fgene.2014.00329] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/03/2014] [Indexed: 11/13/2022] Open
Abstract
The advent of high-throughput sequencing has allowed genome wide profiling of histone modifications by Chromatin ImmunoPrecipitation (ChIP) followed by sequencing (ChIP-seq). In this assay the histone mark of interest is enriched through a chromatin pull-down assay using an antibody for the mark. Due to imperfect antibodies and other factors, many of the sequenced fragments do not originate from the histone mark of interest, and are referred to as background reads. Background reads are not uniformly distributed and therefore control samples are usually used to estimate the background distribution at any given genomic position. The Encyclopedia of DNA Elements (ENCODE) Consortium guidelines suggest sequencing a whole cell extract (WCE, or “input”) sample, or a mock ChIP reaction such as an IgG control, as a background sample. However, for a histone modification ChIP-seq investigation it is also possible to use a Histone H3 (H3) pull-down to map the underlying distribution of histones. In this paper we generated data from a hematopoietic stem and progenitor cell population isolated from mouse fetal liver to compare WCE and H3 ChIP-seq as control samples. The quality of the control samples is estimated by a comparison to pull-downs of histone modifications and to expression data. We find minor differences between WCE and H3 ChIP-seq, such as coverage in mitochondria and behavior close to transcription start sites. Where the two controls differ, the H3 pull-down is generally more similar to the ChIP-seq of histone modifications. However, the differences between H3 and WCE have a negligible impact on the quality of a standard analysis.
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Affiliation(s)
- Christoffer Flensburg
- Bioinformatics Group, Murdoch Childrens Research Institute Melbourne, VIC, Australia
| | - Sarah A Kinkel
- Division of Molecular Medicine, Department of Medical Biology, Walter and Eliza Hall Institute, University of Melbourne Melbourne, VIC, Australia
| | - Andrew Keniry
- Division of Molecular Medicine, Department of Medical Biology, Walter and Eliza Hall Institute, University of Melbourne Melbourne, VIC, Australia
| | - Marnie E Blewitt
- Division of Molecular Medicine, Department of Medical Biology, Walter and Eliza Hall Institute, University of Melbourne Melbourne, VIC, Australia ; Department of Genetics, University of Melbourne Melbourne, VIC, Australia
| | - Alicia Oshlack
- Bioinformatics Group, Murdoch Childrens Research Institute Melbourne, VIC, Australia ; Department of Genetics, University of Melbourne Melbourne, VIC, Australia
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5
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Leong DW, Komen JC, Hewitt CA, Arnaud E, McKenzie M, Phipson B, Bahlo M, Laskowski A, Kinkel SA, Davey GM, Heath WR, Voss AK, Zahedi RP, Pitt JJ, Chrast R, Sickmann A, Ryan MT, Smyth GK, Thorburn DR, Scott HS. Proteomic and metabolomic analyses of mitochondrial complex I-deficient mouse model generated by spontaneous B2 short interspersed nuclear element (SINE) insertion into NADH dehydrogenase (ubiquinone) Fe-S protein 4 (Ndufs4) gene. J Biol Chem 2012; 287:20652-63. [PMID: 22535952 PMCID: PMC3370248 DOI: 10.1074/jbc.m111.327601] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 04/05/2012] [Indexed: 01/11/2023] Open
Abstract
Eukaryotic cells generate energy in the form of ATP, through a network of mitochondrial complexes and electron carriers known as the oxidative phosphorylation system. In mammals, mitochondrial complex I (CI) is the largest component of this system, comprising 45 different subunits encoded by mitochondrial and nuclear DNA. Humans diagnosed with mutations in the gene NDUFS4, encoding a nuclear DNA-encoded subunit of CI (NADH dehydrogenase ubiquinone Fe-S protein 4), typically suffer from Leigh syndrome, a neurodegenerative disease with onset in infancy or early childhood. Mitochondria from NDUFS4 patients usually lack detectable NDUFS4 protein and show a CI stability/assembly defect. Here, we describe a recessive mouse phenotype caused by the insertion of a transposable element into Ndufs4, identified by a novel combined linkage and expression analysis. Designated Ndufs4(fky), the mutation leads to aberrant transcript splicing and absence of NDUFS4 protein in all tissues tested of homozygous mice. Physical and behavioral symptoms displayed by Ndufs4(fky/fky) mice include temporary fur loss, growth retardation, unsteady gait, and abnormal body posture when suspended by the tail. Analysis of CI in Ndufs4(fky/fky) mice using blue native PAGE revealed the presence of a faster migrating crippled complex. This crippled CI was shown to lack subunits of the "N assembly module", which contains the NADH binding site, but contained two assembly factors not present in intact CI. Metabolomic analysis of the blood by tandem mass spectrometry showed increased hydroxyacylcarnitine species, implying that the CI defect leads to an imbalanced NADH/NAD(+) ratio that inhibits mitochondrial fatty acid β-oxidation.
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Affiliation(s)
| | - Jasper C. Komen
- the Murdoch Childrens Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia
| | | | - Estelle Arnaud
- the Département de Génétique Médicale, Université de Lausanne, 1005 Lausanne, Switzerland
| | - Matthew McKenzie
- the Centre for Reproduction and Development, Monash Institute of Medical Research, Clayton, Victoria 3168, Australia
| | - Belinda Phipson
- Bioinformatics Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Melanie Bahlo
- Bioinformatics Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- Department of Mathematics and Statistics, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Adrienne Laskowski
- the Murdoch Childrens Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Sarah A. Kinkel
- From the Molecular Medicine Division
- Immunology Division, and
- the Department of Medical Biology and
| | | | | | - Anne K. Voss
- From the Molecular Medicine Division
- the Department of Medical Biology and
| | - René P. Zahedi
- the Leibniz-Institut für Analytische Wissenschaften e.V., 44227 Dortmund, Germany
| | - James J. Pitt
- VCGS Pathology, Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia
| | - Roman Chrast
- the Département de Génétique Médicale, Université de Lausanne, 1005 Lausanne, Switzerland
| | - Albert Sickmann
- the Leibniz-Institut für Analytische Wissenschaften e.V., 44227 Dortmund, Germany
- the Medizinisches Proteom Center, Ruhr-Universität-Bochum, 44780 Bochum, Germany
| | - Michael T. Ryan
- the Department of Biochemistry, La Trobe University, Bundoora, Victoria 3086, Australia, and
| | - Gordon K. Smyth
- Bioinformatics Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- the Department of Medical Biology and
- Department of Mathematics and Statistics, University of Melbourne, Parkville, Victoria 3052, Australia
| | - David R. Thorburn
- the Murdoch Childrens Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Hamish S. Scott
- From the Molecular Medicine Division
- the Department of Medical Biology and
- the Department of Molecular Pathology, Centre for Cancer Biology, SA Pathology, Box 14 Rundle Mall Post Office, Adelaide, South Australia 5000, Australia, and
- the Schools of Medicine and Molecular and Biomedical Science, University of Adelaide, South Australia 5005, Australia
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6
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Kont V, Murumägi A, Tykocinski LO, Kinkel SA, Webster KE, Kisand K, Tserel L, Pihlap M, Ströbel P, Scott HS, Marx A, Kyewski B, Peterson P. DNA methylation signatures of the AIRE promoter in thymic epithelial cells, thymomas and normal tissues. Mol Immunol 2011; 49:518-26. [PMID: 22036612 DOI: 10.1016/j.molimm.2011.09.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 09/11/2011] [Accepted: 09/29/2011] [Indexed: 11/30/2022]
Abstract
Mutations in the AIRE gene cause autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), which is associated with autoimmunity towards several peripheral organs. The AIRE protein is almost exclusively expressed in medullary thymic epithelial cells (mTEC) and CpG methylation in the promoter of the AIRE gene has been suggested to control its tissue-specific expression pattern. We found that in human AIRE-positive medullary and AIRE-negative cortical epithelium, the AIRE promoter is hypomethylated, whereas in thymocytes, the promoter had high level of CpG methylation. Likewise, in mouse mTECs the AIRE promoter was uniformly hypomethylated. In the same vein, the AIRE promoter was hypomethylated in AIRE-negative thymic epithelial tumors (thymomas) and in several peripheral tissues. Our data are compatible with the notion that promoter hypomethylation is necessary but not sufficient for tissue-specific regulation of the AIRE gene. In contrast, a positive correlation between AIRE expression and histone H3 lysine 4 trimethylation, an active chromatin mark, was found in the AIRE promoter in human and mouse TECs.
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Affiliation(s)
- Vivian Kont
- Molecular Pathology Group, Tartu University, 50411 Tartu, Estonia
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7
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Hubert FX, Kinkel SA, Davey GM, Phipson B, Mueller SN, Liston A, Proietto AI, Cannon PZF, Forehan S, Smyth GK, Wu L, Goodnow CC, Carbone FR, Scott HS, Heath WR. Aire regulates the transfer of antigen from mTECs to dendritic cells for induction of thymic tolerance. Blood 2011; 118:2462-72. [PMID: 21505196 DOI: 10.1182/blood-2010-06-286393] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
To investigate the role of Aire in thymic selection, we examined the cellular requirements for generation of ovalbumin (OVA)-specific CD4 and CD8 T cells in mice expressing OVA under the control of the rat insulin promoter. Aire deficiency reduced the number of mature single-positive OVA-specific CD4(+) or CD8(+) T cells in the thymus, independent of OVA expression. Importantly, it also contributed in 2 ways to OVA-dependent negative selection depending on the T-cell type. Aire-dependent negative selection of OVA-specific CD8 T cells correlated with Aire-regulated expression of OVA. By contrast, for OVA-specific CD4 T cells, Aire affected tolerance induction by a mechanism that operated independent of the level of OVA expression, controlling access of antigen presenting cells to medullary thymic epithelial cell (mTEC)-expressed OVA. This study supports the view that one mechanism by which Aire controls thymic negative selection is by regulating the indirect presentation of mTEC-derived antigens by thymic dendritic cells. It also indicates that mTECs can mediate tolerance by direct presentation of Aire-regulated antigens to both CD4 and CD8 T cells.
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Affiliation(s)
- François-Xavier Hubert
- Immunology Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
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8
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Zamudio NM, Scott HS, Wolski K, Lo CY, Law C, Leong D, Kinkel SA, Chong S, Jolley D, Smyth GK, de Kretser D, Whitelaw E, O'Bryan MK. DNMT3L is a regulator of X chromosome compaction and post-meiotic gene transcription. PLoS One 2011; 6:e18276. [PMID: 21483837 PMCID: PMC3069080 DOI: 10.1371/journal.pone.0018276] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2010] [Accepted: 03/01/2011] [Indexed: 01/14/2023] Open
Abstract
Previous studies on the epigenetic regulator DNA methyltransferase 3-Like (DNMT3L), have demonstrated it is an essential regulator of paternal imprinting and early male meiosis. Dnmt3L is also a paternal effect gene, i.e., wild type offspring of heterozygous mutant sires display abnormal phenotypes suggesting the inheritance of aberrant epigenetic marks on the paternal chromosomes. In order to reveal the mechanisms underlying these paternal effects, we have assessed X chromosome meiotic compaction, XY chromosome aneuploidy rates and global transcription in meiotic and haploid germ cells from male mice heterozygous for Dnmt3L. XY bodies from Dnmt3L heterozygous males were significantly longer than those from wild types, and were associated with a three-fold increase in XY bearing sperm. Loss of a Dnmt3L allele resulted in deregulated expression of a large number of both X-linked and autosomal genes within meiotic cells, but more prominently in haploid germ cells. Data demonstrate that similar to embryonic stem cells, DNMT3L is involved in an auto-regulatory loop in germ cells wherein the loss of a Dnmt3L allele resulted in increased transcription from the remaining wild type allele. In contrast, however, within round spermatids, this auto-regulatory loop incorporated the alternative non-coding alternative transcripts. Consistent with the mRNA data, we have localized DNMT3L within spermatids and sperm and shown that the loss of a Dnmt3L allele results in a decreased DNMT3L content within sperm. These data demonstrate previously unrecognised roles for DNMT3L in late meiosis and in the transcriptional regulation of meiotic and post-meiotic germ cells. These data provide a potential mechanism for some cases of human Klinefelter's and Turner's syndromes.
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Affiliation(s)
- Natasha M. Zamudio
- The Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
- The Australian Research Council Centre of Excellence in Biotechnology and Development, Monash University, Victoria, Australia
| | - Hamish S. Scott
- The Institute of Medical and Veterinary Science, University of Adelaide, Adelaide, Australia
| | - Katja Wolski
- The Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
| | - Chi-Yi Lo
- The Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
| | - Charity Law
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Queensland Institute of Medical Research, Herston, Queensland, Australia
| | - Dillon Leong
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Sarah A. Kinkel
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Victoria, Australia
| | - Suyinn Chong
- Queensland Institute of Medical Research, Herston, Queensland, Australia
| | - Damien Jolley
- The Monash Institute of Health Services Research, Monash University, Victoria, Australia
| | - Gordon K. Smyth
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - David de Kretser
- The Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
| | - Emma Whitelaw
- Queensland Institute of Medical Research, Herston, Queensland, Australia
| | - Moira K. O'Bryan
- The Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
- The Australian Research Council Centre of Excellence in Biotechnology and Development, Monash University, Victoria, Australia
- * E-mail: Moira.O'
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9
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Ko HJ, Kinkel SA, Hubert FX, Nasa Z, Chan J, Siatskas C, Hirubalan P, Toh BH, Scott HS, Alderuccio F. Transplantation of autoimmune regulator-encoding bone marrow cells delays the onset of experimental autoimmune encephalomyelitis. Eur J Immunol 2010; 40:3499-509. [PMID: 21108470 DOI: 10.1002/eji.201040679] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 08/12/2010] [Accepted: 09/02/2010] [Indexed: 01/04/2023]
Abstract
The autoimmune regulator (AIRE) promotes "promiscuous" expression of tissue-restricted antigens (TRA) in thymic medullary epithelial cells to facilitate thymic deletion of autoreactive T-cells. Here, we show that AIRE-deficient mice showed an earlier development of myelin oligonucleotide glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). To determine the outcome of ectopic Aire expression, we used a retroviral transduction system to over-express Aire in vitro, in cell lines and in bone marrow (BM). In the cell lines that included those of thymic medullary and dendritic cell origin, ectopically expressed Aire variably promoted expression of TRA including Mog and Ins2 (proII) autoantigens associated, respectively, with the autoimmune diseases multiple sclerosis and type 1 diabetes. BM chimeras generated from BM transduced with a retrovirus encoding Aire displayed elevated levels of Mog and Ins2 expression in thymus and spleen. Following induction of EAE with MOG(35-55), transplanted mice displayed significant delay in the onset of EAE compared with control mice. To our knowledge, this is the first example showing that in vivo ectopic expression of AIRE can modulate TRA expression and alter autoimmune disease development.
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Affiliation(s)
- Hyun-Ja Ko
- Department of Immunology, Central Clinical School, Monash University, Melbourne, VIC, Australia
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10
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Shi W, de Graaf CA, Kinkel SA, Achtman AH, Baldwin T, Schofield L, Scott HS, Hilton DJ, Smyth GK. Estimating the proportion of microarray probes expressed in an RNA sample. Nucleic Acids Res 2010; 38:2168-76. [PMID: 20056656 PMCID: PMC2853118 DOI: 10.1093/nar/gkp1204] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/03/2009] [Accepted: 12/11/2009] [Indexed: 12/28/2022] Open
Abstract
A fundamental question in microarray analysis is the estimation of the number of expressed probes in different RNA samples. Negative control probes available in the latest microarray platforms, such as Illumina whole genome expression BeadChips, provide a unique opportunity to estimate the number of expressed probes without setting a threshold. A novel algorithm was proposed in this study to estimate the number of expressed probes in an RNA sample by utilizing these negative controls to measure background noise. The performance of the algorithm was demonstrated by comparing different generations of Illumina BeadChips, comparing the set of probes targeting well-characterized RefSeq NM transcripts with other probes on the array and comparing pure samples with heterogenous samples. Furthermore, hematopoietic stem cells were found to have a larger transcriptome than progenitor cells. Aire knockout medullary thymic epithelial cells were shown to have significantly less expressed probes than matched wild-type cells.
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Affiliation(s)
- Wei Shi
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Carolyn A. de Graaf
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Sarah A. Kinkel
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Ariel H. Achtman
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Tracey Baldwin
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Louis Schofield
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Hamish S. Scott
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Douglas J. Hilton
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Gordon K. Smyth
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, The Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Institute of Medical and Veterinary Science and The Hanson Institute, Box 14 Rundle Mall Post Office, Adelaide, Adelaide Cancer Research Institute, The School of Medicine, University of Adelaide, SA 5000 and The Department of Mathematics and Statistics, The University of Melbourne, Parkville, VIC 3010, Australia
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Campbell IK, Kinkel SA, Drake SF, van Nieuwenhuijze A, Hubert FX, Tarlinton DM, Heath WR, Scott HS, Wicks IP. Autoimmune regulator controls T cell help for pathogenetic autoantibody production in collagen-induced arthritis. Arthritis Rheum 2009; 60:1683-93. [PMID: 19479827 DOI: 10.1002/art.24501] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
OBJECTIVE Autoimmune regulator (Aire) promotes the ectopic expression of tissue-restricted antigens in medullary thymic epithelial cells (mTECs), leading to negative selection of autoreactive T cells. This study was undertaken to determine whether loss of central tolerance renders Aire-deficient (Aire-/-) mice more susceptible to the induction of autoimmune arthritis. METHODS Medullary TECs were isolated from Aire-/- and wild-type C57BL/6 mice for gene expression analysis. Collagen-induced arthritis (CIA) was elicited by injection of chick type II collagen (CII) in adjuvant. Cellular and humoral immune responses to CII were evaluated. Chimeric mice were created by reconstituting lymphocyte-deficient mice with either Aire-/- or wild-type CD4 T cells and wild-type B cells. RESULTS Wild-type, but not Aire-/-, mTECs expressed the CII gene Col2a1. Aire-/- mice developed more rapid and severe CIA, showing elevated serum anti-CII IgG levels, with earlier switching to arthritogenic IgG subclasses. No evidence was found of enhanced T cell responsiveness to CII in Aire-/- mice; however, Aire-/- CD4 T cells were more efficient at stimulating wild-type B cells to produce anti-CII IgG following immunization of chimeric mice with CII. CONCLUSION Our findings indicate that Aire-dependent expression of CII occurs in mTECs, implying that there is central tolerance to self antigens found in articular cartilage. Reduced central tolerance to CII in Aire-/- mice manifests as increased CD4 T cell help to B cells for cross-reactive autoantibody production and enhanced CIA. Aire and central tolerance help prevent cross-reactive autoimmune responses to CII initiated by environmental stimuli and limit spontaneous autoimmunity.
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Affiliation(s)
- Ian K Campbell
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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12
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Hubert FX, Kinkel SA, Crewther PE, Cannon PZF, Webster KE, Link M, Uibo R, O'Bryan MK, Meager A, Forehan SP, Smyth GK, Mittaz L, Antonarakis SE, Peterson P, Heath WR, Scott HS. Aire-deficient C57BL/6 mice mimicking the common human 13-base pair deletion mutation present with only a mild autoimmune phenotype. J Immunol 2009; 182:3902-18. [PMID: 19265170 DOI: 10.4049/jimmunol.0802124] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Autoimmune regulator (AIRE) is an important transcription regulator that mediates a role in central tolerance via promoting the "promiscuous" expression of tissue-specific Ags in the thymus. Although several mouse models of Aire deficiency have been described, none has analyzed the phenotype induced by a mutation that emulates the common 13-bp deletion in human APECED (autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy) by disrupting the first plant homeodomain in exon 8. Aire-deficient mice with a corresponding mutation showed some disturbance of the medullary epithelial compartment, but at the phenotypic level their T cell compartment appeared relatively normal in the thymus and periphery. An increase in the number of activated T cells was evident, and autoantibodies against several organs were detected. At the histological level, lymphocytic infiltration of several organs indicated the development of autoimmunity, although symptoms were mild and the quality of life for Aire-deficient mice appeared equivalent to wild-type littermates, with the exception of male infertility. Vbeta and CDR3 length analysis suggested that each Aire-deficient mouse developed its own polyclonal autoimmune repertoire. Finally, given the prevalence of candidiasis in APECED patients, we examined the control of infection with Candida albicans in Aire-deficient mice. No increase in disease susceptibility was found for either oral or systemic infection. These observations support the view that additional genetic and/or environmental factors contribute substantially to the overt nature of autoimmunity associated with Aire mutations, even for mutations identical to those found in humans with APECED.
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Affiliation(s)
- François-Xavier Hubert
- Division of Immunology, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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13
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Hubert FX, Kinkel SA, Webster KE, Cannon P, Crewther PE, Proeitto AI, Wu L, Heath WR, Scott HS. A specific anti-Aire antibody reveals aire expression is restricted to medullary thymic epithelial cells and not expressed in periphery. J Immunol 2008; 180:3824-32. [PMID: 18322189 DOI: 10.4049/jimmunol.180.6.3824] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy is an autoimmune disorder caused by mutations in the autoimmune regulator gene AIRE. We examined the expression of Aire in different organs (thymus, spleen, and lymph nodes) in C57BL/6 mice, using a novel rat mAb, specific for murine Aire. Using flow cytometry, directly fluorochrome-labeled mAb revealed Aire expression in a rare thymic cellular subset that was CD45(-), expressed low levels of Ly51, and was high for MHC-II and EpCam. This subset also expressed a specific pattern of costimulatory molecules, including CD40, CD80, and PD-L1. Immunohistochemical analysis revealed that Aire(+) cells were specifically localized to the thymus or, more precisely, to the cortico-medulla junction and medulla, correlating with the site of negative selection. Although in agreement with previous studies, low levels of Aire mRNA was detected in all dendritic cell subtypes however lacZ staining, immunohistochemistry and flow cytometry failed to detect Aire protein. At a cellular level, Aire was expressed in perinuclear speckles within the nucleus. This report provides the first detailed analysis of Aire protein expression, highlighting the precise location at both the tissue and cellular level.
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Affiliation(s)
- François-Xavier Hubert
- Division of Molecular and Medicine, Walter and Eliza Hall Institute of Medical Research, University of Melbourne, Parkville, Victoria, Australia.
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14
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Alimohammadi M, Björklund P, Hallgren A, Pöntynen N, Szinnai G, Shikama N, Keller MP, Ekwall O, Kinkel SA, Husebye ES, Gustafsson J, Rorsman F, Peltonen L, Betterle C, Perheentupa J, Akerström G, Westin G, Scott HS, Holländer GA, Kämpe O. Autoimmune polyendocrine syndrome type 1 and NALP5, a parathyroid autoantigen. N Engl J Med 2008; 358:1018-28. [PMID: 18322283 DOI: 10.1056/nejmoa0706487] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disorder caused by mutations in AIRE, the autoimmune regulator gene. Though recent studies concerning AIRE deficiency have begun to elucidate the molecular pathogenesis of organ-specific autoimmunity in patients with APS-1, the autoantigen responsible for hypoparathyroidism, a hallmark of APS-1 and its most common autoimmune endocrinopathy, has not yet been identified. METHODS We performed immunoscreening of a human parathyroid complementary DNA library, using serum samples from patients with APS-1 and hypoparathyroidism, to identify patients with reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5). Subsequently, serum samples from 87 patients with APS-1 and 293 controls, including patients with other autoimmune disorders, were used to determine the frequency and specificity of autoantibodies against NALP5. In addition, the expression of NALP5 was investigated in various tissues. RESULTS NALP5-specific autoantibodies were detected in 49% of the patients with APS-1 and hypoparathyroidism but were absent in all patients with APS-1 but without hypoparathyroidism, in all patients with other autoimmune endocrine disorders, and in all healthy controls. NALP5 was predominantly expressed in the cytoplasm of parathyroid chief cells. CONCLUSIONS NALP5 appears to be a tissue-specific autoantigen involved in hypoparathyroidism in patients with APS-1. Autoantibodies against NALP5 appear to be highly specific and may be diagnostic for this prominent component of APS-1.
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Scarpino S, Di Napoli A, Stoppacciaro A, Antonelli M, Pilozzi E, Chiarle R, Palestro G, Marino M, Facciolo F, Rendina EA, Webster KE, Kinkel SA, Scott HS, Ruco L. Expression of autoimmune regulator gene (AIRE) and T regulatory cells in human thymomas. Clin Exp Immunol 2007; 149:504-12. [PMID: 17590173 PMCID: PMC2219324 DOI: 10.1111/j.1365-2249.2007.03442.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2007] [Indexed: 01/01/2023] Open
Abstract
Expression of the autoimmune regulator gene (AIRE) and the presence of CD25(+)/forkhead box p3 (FoxP3)(+) T regulatory (T(reg)) cells were investigated in histologically normal adult thymi and in thymomas using immunohistochemistry and quantitative real-time polymerase chain reaction (PCR). In the normal thymus staining for AIRE was detected in the nucleus of some epithelial-like cells located in the medulla; in thymomas AIRE-positive cells were extremely rare and could be detected only in the areas of medullary differentiation of two B1 type, organoid thymomas. RNA was extracted from 36 cases of thymoma and 21 non-neoplastic thymi obtained from 11 myasthenic (MG(+)) and 10 non-myasthenic (MG(-)) patients. It was found that AIRE is 8.5-fold more expressed in non-neoplastic thymi than in thymomas (P = 0.01), and that the amount of AIRE transcripts present in the thymoma tissue are not influenced by the association with MG, nor by the histological type. A possible involvement of AIRE in the development of MG was suggested by the observation that medullary thymic epithelial cells isolated from AIRE-deficient mice contain low levels of RNA transcripts for CHRNA 1, a gene coding for acetylcholine receptor. Expression of human CHRNA 1 RNA was investigated in 34 human thymomas obtained from 20 MG(-) patients and 14 MG(+) patients. No significant difference was found in the two groups (thymoma MG(+), CHRNA1 = 0.013 +/- 0.03; thymoma MG-, CHRNA1 = 0.01 +/- 0.03). In normal and hyperplastic thymi CD25(+)/Foxp3(+) cells were located mainly in the medulla, and their number was not influenced by the presence of MG. Foxp3(+) and CD25(+) cells were significantly less numerous in thymomas. A quantitative estimate of T(reg) cells revealed that the levels of Foxp3 RNA detected in non-neoplastic thymi were significantly higher (P = 0.02) than those observed in 31 cases of thymomas. Our findings indicate that the tissue microenvironment of thymomas is defective in the expression of relevant functions that exert a crucial role in the negative selection of autoreactive lymphocytes.
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Affiliation(s)
- S Scarpino
- Dip. di Istopatologia ed Anatomia Patologica, Ospedale Sant'Andrea, II Facoltà di Medicina e Chirurgia, Università 'La Sapienza', Rome, Italy.
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