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Xiang Z, Yang Y, Chang C, Lu Q. The epigenetic mechanism for discordance of autoimmunity in monozygotic twins. J Autoimmun 2017; 83:43-50. [PMID: 28412046 DOI: 10.1016/j.jaut.2017.04.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Accepted: 04/05/2017] [Indexed: 12/12/2022]
Abstract
Monozygotic twins share an identical DNA sequence but are not truly "identical". In fact, when it comes to health and disease, they may often display some level of phenotypic discordance. The cause of this discordance is often unknown. Epigenetic modifications such as DNA methylation, histone modification, and microRNAs-mediated regulation regulate gene expression and are sensitive to external stimuli. These modifications may be seen to bridge the gap between genetics and the environment. Over the years, the importance of epigenetics as a primary mechanism for the role that the environment plays in defining phenotype has been increasingly appreciated. Mechanisms of epigenetics include DNA methylation, histone modifications and microRNAs. Discordance rates in monozygotic twins vary depending on the specific condition, from 11% in SLE to 64% in psoriasis and 77% in PBC. Other autoimmune diseases in which discordance is found among monozygotic twins has also been studied include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, dermatomyositis and systemic sclerosis. In some cases, the differences in various epigenetic modifications is slight, even though the concordance rate is low, suggesting that epigenetics is not the only factor that needs to be considered. Nonetheless, the study of phenotypic discordance in monozygotic twins may shed light on the pathogenesis of autoimmune diseases and contribute to the development of new methodologies for the diagnosis and treatment of these diseases.
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Affiliation(s)
- Zhongyuan Xiang
- Department of Laboratory Medicine, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Yuanqing Yang
- Department of Laboratory Medicine, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Christopher Chang
- Division of Rheumatology, Allergy and Clinical Immunology, University of California at Davis, 451 Health Sciences Drive, Suite 6510, Davis, CA 95616, United States
| | - Qianjin Lu
- Department of Dermatology, Second Xiangya Hospital, Central South University, Hunan Key Laboratory of Medical Epigenomics, Changsha, Hunan, China.
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Bogdanos DP, Smyk DS, Rigopoulou EI, Mytilinaiou MG, Heneghan MA, Selmi C, Gershwin ME. Twin studies in autoimmune disease: genetics, gender and environment. J Autoimmun 2011; 38:J156-69. [PMID: 22177232 DOI: 10.1016/j.jaut.2011.11.003] [Citation(s) in RCA: 198] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 11/12/2011] [Indexed: 02/08/2023]
Abstract
Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. High concordance rates among monozygotic (MZ) twins support genetic factors being predominantly involved, whilst low rates are suggestive of environmental factors. Twin studies have often been utilised in the study of systemic and organ specific autoimmune diseases. As an example, type I diabetes mellitus has been investigated to establish that that disease is largely affected by genetic factors, compared to rheumatoid arthritis or scleroderma, which have a weaker genetic association. However, large twin studies are scarce or virtually non-existent in other autoimmune diseases which have been limited to few sets of twins and individual case reports. In addition to the study of the genetic and environmental contributions to disease, it is likely that twin studies will also provide data in regards to the clinical course of disease, as well as risk for development in related individuals. More importantly, genome-wide association studies have thus far reported genomic variants that only account for a minority of autoimmunity cases, and cannot explain disease discordance in MZ twins. Future research is therefore encouraged not only in the analysis of twins with autoimmune disease, but also in regards to epigenetic factors or rare variants that may be discovered with next-generation sequencing. This review will examine the literature surrounding twin studies in autoimmune disease including discussions of genetics and gender.
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Affiliation(s)
- Dimitrios P Bogdanos
- Institute of Liver Studies, Liver Immunopathology, King's College London School of Medicine at King's College Hospital, London, UK.
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Abstract
Multiple sclerosis (MS) is probably aetiologically heterogeneous. Systematic genetic epidemiological and molecular genetic studies have provided important insights. Both genetic and non-genetic (environment, stochastic) factors may be involved in susceptibility as well as outcome, but we have yet to understand their relative roles. Any environmental factor is likely to be ubiquitous and act on a population-basis rather than within the family microenvironment. Taken together, the results of genome screening studies provide strong evidence for exclusion of a major locus in MS. There are, however, many genes that seem to be associated with MS. These include, but are in no way limited to, HLA classes I and II, T-cell receptor beta, CTLA4, ICAM1, and SH2D2A. The future of MS genetics, as for most common complex disorders, will be dependent on the resources available, ranging from biological samples and comprehensive databases of clinical and epidemiological information to the development of new technologies and statistical methods.
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Affiliation(s)
- David A Dyment
- The Wellcome Trust Center for Human Genetics, University of Oxford, Oxford, UK
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Willer CJ, Dyment DA, Risch NJ, Sadovnick AD, Ebers GC. Twin concordance and sibling recurrence rates in multiple sclerosis. Proc Natl Acad Sci U S A 2003; 100:12877-82. [PMID: 14569025 PMCID: PMC240712 DOI: 10.1073/pnas.1932604100] [Citation(s) in RCA: 317] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Size and ascertainment constraints often limit twin studies to concordance comparisons between identical and fraternal twins. Here we report the final results of a longitudinal, population-based study of twins with multiple sclerosis (MS) in Canada. Bias was demonstrably minimized, and an estimated 75% of all Canadian MS twin pairs were ascertained, giving a sample sufficiently large (n = 370) to permit additional informative comparisons. Twinning was not found to affect prevalence, and twins with MS did not differ from nontwins for DR15 allele frequency nor for MS risk to their siblings. Probandwise concordance rates of 25.3% (SE +/- 4.4) for monozygotic (MZ), 5.4% (+/-2.8) for dizygotic (DZ), and 2.9% (+/-0.6) for their nontwin siblings were found. MZ twin concordance was in excess of DZ twin concordance. The excess concordance in MZ was derived primarily from like-sexed female pairs with a probandwise concordance rate of 34 of 100 (34 +/- 5.7%) compared with 3 of 79 (3.8 +/- 2.8%) for female DZ pairs. We did not demonstrate an MZ/DZ difference in males, although the sample size was small. We observed a 2-fold increase in risk to DZ twins over nontwin siblings of twins, but the difference was not significant.
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Affiliation(s)
- C. J. Willer
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; Department of Genetics, Stanford University, M-335A, Stanford, CA 94305-5120; Department of Medical Genetics, and Faculty of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada V6T 2B5; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford University, Woodstock Road, Oxford OX2 6HE, United Kingdom
| | - D. A. Dyment
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; Department of Genetics, Stanford University, M-335A, Stanford, CA 94305-5120; Department of Medical Genetics, and Faculty of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada V6T 2B5; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford University, Woodstock Road, Oxford OX2 6HE, United Kingdom
| | - N. J. Risch
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; Department of Genetics, Stanford University, M-335A, Stanford, CA 94305-5120; Department of Medical Genetics, and Faculty of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada V6T 2B5; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford University, Woodstock Road, Oxford OX2 6HE, United Kingdom
| | - A. D. Sadovnick
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; Department of Genetics, Stanford University, M-335A, Stanford, CA 94305-5120; Department of Medical Genetics, and Faculty of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada V6T 2B5; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford University, Woodstock Road, Oxford OX2 6HE, United Kingdom
| | - G. C. Ebers
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; Department of Genetics, Stanford University, M-335A, Stanford, CA 94305-5120; Department of Medical Genetics, and Faculty of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada V6T 2B5; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford University, Woodstock Road, Oxford OX2 6HE, United Kingdom
- To whom correspondence should be sent at the †† address. E-mail:
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