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Sun W, Wang Z, Wen S, Huang A, Li H, Jiang L, Feng Q, Fan D, Tian Q, Han D, Liu X. Technical strategy for monozygotic twin discrimination by single-nucleotide variants. Int J Legal Med 2024; 138:767-779. [PMID: 38197923 DOI: 10.1007/s00414-023-03150-7] [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: 03/08/2023] [Accepted: 12/11/2023] [Indexed: 01/11/2024]
Abstract
Monozygotic (MZ) twins are theoretically genetically identical. Although they are revealed to accumulate mutations after the zygote splits, discriminating between twin genomes remains a formidable challenge in the field of forensic genetics. Single-nucleotide variants (SNVs) are responsible for a substantial portion of genetic variation, thus potentially serving as promising biomarkers for the identification of MZ twins. In this study, we sequenced the whole genome of a pair of female MZ twins when they were 27 and 33 years old to approximately 30 × coverage using peripheral blood on an Illumina NovaSeq 6000 Sequencing System. Potentially discordant SNVs supported by whole-genome sequencing were validated extensively by amplicon-based targeted deep sequencing and Sanger sequencing. In total, we found nine bona fide post-twinning SNVs, all of which were identified in the younger genomes and found in the older genomes. None of the SNVs occurred within coding exons, three of which were observed in introns, supported by whole-exome sequencing results. A double-blind test was employed, and the reliability of MZ twin discrimination by discordant SNVs was endorsed. All SNVs were successfully detected when input DNA amounts decreased to 0.25 ng, and reliable detection was limited to seven SNVs below 0.075 ng input. This comprehensive analysis confirms that SNVs could serve as cost-effective biomarkers for MZ twin discrimination.
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Affiliation(s)
- Weifen Sun
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Ziwei Wang
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
- Department of Forensic Science, Medical School of Soochow University, Suzhou, 215123, China
| | - Shubo Wen
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
- Department of Forensic Science, Medical School of Soochow University, Suzhou, 215123, China
| | - Ao Huang
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
- Department of Forensic Science, Medical School of Soochow University, Suzhou, 215123, China
| | - Hui Li
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
| | - Lei Jiang
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China
| | - Qi Feng
- National Center for Gene Research, State Key Laboratory of Plant Molecular Genetics, Center of Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200233, China
| | - Danlin Fan
- National Center for Gene Research, State Key Laboratory of Plant Molecular Genetics, Center of Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200233, China
| | - Qilin Tian
- National Center for Gene Research, State Key Laboratory of Plant Molecular Genetics, Center of Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200233, China
| | - Dingding Han
- Department of Clinical Laboratory, Shanghai Children's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200062, China
| | - Xiling Liu
- Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Ministry of Justice, Shanghai, 200063, China.
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Imamura A, Morimoto Y, Ono S, Kurotaki N, Kanegae S, Yamamoto N, Kinoshita H, Tsujita T, Okazaki Y, Ozawa H. Genetic and environmental factors of schizophrenia and autism spectrum disorder: insights from twin studies. J Neural Transm (Vienna) 2020; 127:1501-1515. [PMID: 32285255 PMCID: PMC7578126 DOI: 10.1007/s00702-020-02188-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/05/2020] [Indexed: 02/06/2023]
Abstract
Twin studies of psychiatric disorders such as schizophrenia and autism spectrum disorder have employed epidemiological approaches that determine heritability by comparing the concordance rate between monozygotic twins (MZs) and dizygotic twins. The basis for these studies is that MZs share 100% of their genetic information. Recently, biological studies based on molecular methods are now being increasingly applied to examine the differences between MZs discordance for psychiatric disorders to unravel their possible causes. Although recent advances in next-generation sequencing have increased the accuracy of this line of research, there has been greater emphasis placed on epigenetic changes versus DNA sequence changes as the probable cause of discordant psychiatric disorders in MZs. Since the epigenetic status differs in each tissue type, in addition to the DNA from the peripheral blood, studies using DNA from nerve cells induced from postmortem brains or induced pluripotent stem cells are being carried out. Although it was originally thought that epigenetic changes occurred as a result of environmental factors, and thus were not transmittable, it is now known that such changes might possibly be transmitted between generations. Therefore, the potential possible effects of intestinal flora inside the body are currently being investigated as a cause of discordance in MZs. As a result, twin studies of psychiatric disorders are greatly contributing to the elucidation of genetic and environmental factors in the etiology of psychiatric conditions.
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Affiliation(s)
- Akira Imamura
- Child and Adolescent Psychiatry Community Partnership Unit, Nagasaki University Hospital, Nagasaki, Japan.
| | - Yoshiro Morimoto
- Unit of Translation Medicine, Department of Neuropsychiatry, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Human Genetics, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Shinji Ono
- Department of Human Genetics, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Naohiro Kurotaki
- Department of Clinical Psychiatry, Graduate School of Medicine, Kagawa University, Kita-gun, Japan
| | - Shinji Kanegae
- Child and Adolescent Psychiatry Community Partnership Unit, Nagasaki University Hospital, Nagasaki, Japan
| | - Naoki Yamamoto
- Child and Adolescent Psychiatry Community Partnership Unit, Nagasaki University Hospital, Nagasaki, Japan
- Unit of Translation Medicine, Department of Neuropsychiatry, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Hirohisa Kinoshita
- Unit of Translation Medicine, Department of Neuropsychiatry, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | | | - Yuji Okazaki
- Koseikai Michinoo Hospital, Nagasaki, Japan
- Tokyo Metropolitan Matsuzawa Hospital, Tokyo, Japan
| | - Hiroki Ozawa
- Child and Adolescent Psychiatry Community Partnership Unit, Nagasaki University Hospital, Nagasaki, Japan
- Unit of Translation Medicine, Department of Neuropsychiatry, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
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3
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Sawada T, Chater TE, Sasagawa Y, Yoshimura M, Fujimori-Tonou N, Tanaka K, Benjamin KJM, Paquola ACM, Erwin JA, Goda Y, Nikaido I, Kato T. Developmental excitation-inhibition imbalance underlying psychoses revealed by single-cell analyses of discordant twins-derived cerebral organoids. Mol Psychiatry 2020; 25:2695-2711. [PMID: 32764691 PMCID: PMC7577852 DOI: 10.1038/s41380-020-0844-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 06/23/2020] [Accepted: 07/10/2020] [Indexed: 02/06/2023]
Abstract
Despite extensive genetic and neuroimaging studies, detailed cellular mechanisms underlying schizophrenia and bipolar disorder remain poorly understood. Recent progress in single-cell RNA sequencing (scRNA-seq) technologies enables identification of cell-type-specific pathophysiology. However, its application to psychiatric disorders is challenging because of methodological difficulties in analyzing human brains and the confounds due to a lifetime of illness. Brain organoids derived from induced pluripotent stem cells (iPSCs) of the patients are a powerful avenue to investigate the pathophysiological processes. Here, we generated iPSC-derived cerebral organoids from monozygotic twins discordant for psychosis. scRNA-seq analysis of the organoids revealed enhanced GABAergic specification and reduced cell proliferation following diminished Wnt signaling in the patient, which was confirmed in iPSC-derived forebrain neuronal cells. Two additional monozygotic twin pairs discordant for schizophrenia also confirmed the excess GABAergic specification of the patients' neural progenitor cells. With a well-controlled genetic background, our data suggest that unbalanced specification of excitatory and inhibitory neurons during cortical development underlies psychoses.
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Affiliation(s)
- Tomoyo Sawada
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Center for Brain Science, Wako, Saitama, Japan. .,Lieber Institute for Brain Development, Baltimore, MD, USA. .,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Thomas E. Chater
- grid.474690.8Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako, Saitama Japan
| | - Yohei Sasagawa
- grid.508743.dLaboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama Japan
| | - Mika Yoshimura
- grid.508743.dLaboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama Japan
| | - Noriko Fujimori-Tonou
- grid.474690.8Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Center for Brain Science, Wako, Saitama Japan
| | - Kaori Tanaka
- grid.508743.dLaboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama Japan
| | - Kynon J. M. Benjamin
- grid.429552.dLieber Institute for Brain Development, Baltimore, MD USA ,grid.21107.350000 0001 2171 9311Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD USA
| | - Apuã C. M. Paquola
- grid.429552.dLieber Institute for Brain Development, Baltimore, MD USA ,grid.21107.350000 0001 2171 9311Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD USA
| | - Jennifer A. Erwin
- grid.429552.dLieber Institute for Brain Development, Baltimore, MD USA ,grid.21107.350000 0001 2171 9311Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD USA ,grid.21107.350000 0001 2171 9311Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD USA
| | - Yukiko Goda
- grid.474690.8Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako, Saitama Japan
| | - Itoshi Nikaido
- grid.508743.dLaboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama Japan ,grid.265073.50000 0001 1014 9130Functional Genome Informatics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo Japan ,grid.20515.330000 0001 2369 4728Master’s/Doctoral Program in Life Science Innovation (Bioinformatics), Degree Programs in Systems and Information Engineering, Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Ibaraki Japan
| | - Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Center for Brain Science, Wako, Saitama, Japan. .,Department of Psychiatry and Behavioral Science, Juntendo University Graduate School of Medicine, Bunkyo, Tokyo, Japan.
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Chen YC, Sudre G, Sharp W, Donovan F, Chandrasekharappa SC, Hansen N, Elnitski L, Shaw P. Neuroanatomic, epigenetic and genetic differences in monozygotic twins discordant for attention deficit hyperactivity disorder. Mol Psychiatry 2018; 23:683-690. [PMID: 28322272 PMCID: PMC5914518 DOI: 10.1038/mp.2017.45] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 01/10/2017] [Accepted: 01/17/2017] [Indexed: 12/18/2022]
Abstract
The study of monozygotic twins discordant for attention deficit hyperactivity disorder can elucidate mechanisms that contribute to the disorder, which affects ~7% of children. First, using in vivo neuroanatomic imaging on 14 pairs of monozygotic twins (mean age 9.7, s.d. 1.9 years), we found that discordance for the disorder is mirrored by differing dimensions of deep brain structures (the striatum and cerebellum), but not the cerebral cortex. Next, using whole-blood DNA from the same twins, we found a significant enrichment of epigenetic differences in genes expressed in these 'discordant' brain structures. Specifically, there is differential methylation of probes lying in the shore and shelf and enhancer regions of striatal and cerebellar genes. Notably, gene sets pertaining to the cerebral cortex (which did not differ in volume between affected and unaffected twins) were not enriched by differentially methylated probes. Genotypic differences between the twin pairs-such as copy number and rare, single-nucleotide variants-did not contribute to phenotypic discordance. Pathway analyses of the genes implicated by the most differentially methylated probes implicated γ-aminobutyric acid (GABA), dopamine and serotonin neurotransmitter systems. The study illustrates how neuroimaging can help guide the search for epigenomic mechanisms in neurodevelopmental disorders.
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Affiliation(s)
- Yun-Ching Chen
- Genomic Functional Analysis Section, Translational and Functional Genomics Branch, NHGRI/NIH, Bethesda
| | - Gustavo Sudre
- Neurobehavioral Clinical Research Section, Social and Behavioral Research Branch, NHGRI/NIH, Bethesda
| | - Wendy Sharp
- Neurobehavioral Clinical Research Section, Social and Behavioral Research Branch, NHGRI/NIH, Bethesda
| | - Frank Donovan
- Genomics Core and Cancer Genomics Unit, Cancer Genetics and Comparative Genomics Branch, NHGRI/NIH, Bethesda
| | | | | | - Laura Elnitski
- Genomic Functional Analysis Section, Translational and Functional Genomics Branch, NHGRI/NIH, Bethesda
| | - Philip Shaw
- Neurobehavioral Clinical Research Section, Social and Behavioral Research Branch, NHGRI/NIH, Bethesda
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Morimoto Y, Ono S, Imamura A, Okazaki Y, Kinoshita A, Mishima H, Nakane H, Ozawa H, Yoshiura KI, Kurotaki N. Deep sequencing reveals variations in somatic cell mosaic mutations between monozygotic twins with discordant psychiatric disease. Hum Genome Var 2017; 4:17032. [PMID: 28765789 PMCID: PMC5529667 DOI: 10.1038/hgv.2017.32] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/23/2017] [Accepted: 06/20/2017] [Indexed: 01/09/2023] Open
Abstract
Monozygotic (MZ) twins have been thought to be genetically identical. However, recent studies have shown discordant variants between them. We performed whole-exome sequencing (WES) in five MZ twin pairs with discordant neurodevelopmental disorders and one healthy control MZ twin to detect discordant variants. We identified three discordant variants confirmed by deep sequencing after analysis by personalized next-generation sequencing (NGS). Three mutations in FBXO38 (chr5:147774428;T>G), SMOC2 (chr6:169051385;A>G) and TDRP (chr8:442616;A>G), were detected with low allele frequency of mutant alleles on deep sequencing, suggesting that these loci are mosaic due to somatic mutations in a developmental stage. Our results suggest that deep sequencing analysis would be an adequate method to detect discordant mutations in candidate genes responsible for heritable diseases.
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Affiliation(s)
- Yoshiro Morimoto
- Department of Neuropsychiatry, Unit of Translation Medicine Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.,Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Shinji Ono
- Department of Neuropsychiatry, Unit of Translation Medicine Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.,Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Akira Imamura
- Department of Neuropsychiatry, Unit of Translation Medicine Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Yuji Okazaki
- Department of Psychiatry, Koseikai Michino-o Hospital, Nagasaki, Japan
| | - Akira Kinoshita
- Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Hiroyuki Mishima
- Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Hideyuki Nakane
- Unit of Rehabilitation Science, Department of Psychiatric Rehabilitation Science, University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Hiroki Ozawa
- Department of Neuropsychiatry, Unit of Translation Medicine Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Koh-Ichiro Yoshiura
- Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Naohiro Kurotaki
- Department of Neuropsychiatry, Unit of Translation Medicine Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
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Lyu N, Guan LL, Ma H, Wang XJ, Wu BM, Shang FH, Wang D, Wen H, Yu X. Failure to Identify Somatic Mutations in Monozygotic Twins Discordant for Schizophrenia by Whole Exome Sequencing. Chin Med J (Engl) 2016; 129:690-5. [PMID: 26960372 PMCID: PMC4804415 DOI: 10.4103/0366-6999.178009] [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] [Indexed: 11/17/2022] Open
Abstract
Background: Schizophrenia (SCZ) is a severe, debilitating, and complex psychiatric disorder with multiple causative factors. An increasing number of studies have determined that rare variations play an important role in its etiology. A somatic mutation is a rare form of genetic variation that occurs at an early stage of embryonic development and is thought to contribute substantially to the development of SCZ. The aim of the study was to explore the novel pathogenic somatic single nucleotide variations (SNVs) and somatic insertions and deletions (indels) of SCZ. Methods: One Chinese family with a monozygotic (MZ) twin pair discordant for SCZ was included. Whole exome sequencing was performed in the co-twin and their parents. Rigorous filtering processes were conducted to prioritize pathogenic somatic variations, and all identified SNVs and indels were further confirmed by Sanger sequencing. Results: One somatic SNV and two somatic indels were identified after rigorous selection processes. However, none was validated by Sanger sequencing. Conclusions: This study is not alone in the failure to identify pathogenic somatic variations in MZ twins, suggesting that exonic somatic variations are extremely rare. Further efforts are warranted to explore the potential genetic mechanism of SCZ.
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Affiliation(s)
| | - Li-Li Guan
- Peking University Sixth Hospital, Peking University Institute of Mental Health, Key Laboratory of Mental Health, Ministry of Health (Peking University), Beijing 100191, China
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Abstract
By definition, monozygotic (MZ) twins carry an identical set of genetic information. The observation of early post-twinning mutational events was shown to cause phenotypic discordance among MZ twin pairs. These mutational events comprise genomic alterations at different scales, ranging from single nucleotide changes to larger copy-number variations (CNVs) of varying sizes, as well as epigenetic changes. Here, we performed whole-exome sequencing (WES) in nine discordant MZ twins to identify somatic mutational events in the affected twin that might exert a dominant negative effect. Five of these MZ twin pairs were discordant for congenital heart defects (CHD), two for endocrine disorders, one for omphalocele, and one for congenital diaphragmatic hernia (CDH). Analysis of WES data from all nine MZ twin pairs using the de novo probability tool DeNovoGear detected only one apparent de novo variation in TMPRSS13 in one of the CHD-affected twins. Analysis of WES data from all nine MZ twin pairs by using standard filter criteria without the de novo probability tool DeNovoGear revealed a total of 6,657 variations in which both the twin pairs differed. After filtering for variations only present in the affected twins and absent in in-house controls, 722 variations remained. Visual inspection for read quality decreased this number to 12, present only in the affected twin. However, Sanger sequencing of the overall 13 variations failed to confirm the variation in the affected twin. These results suggest that somatic mutational events in coding regions do not seem to play a major role in the phenotypic expression of MZ discordant twin pairs.
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Large Autosomal Copy-Number Differences within Unselected Monozygotic Twin Pairs are Rare. Twin Res Hum Genet 2015; 18:13-8. [PMID: 25578400 DOI: 10.1017/thg.2014.85] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Monozygotic (MZ) twins form an important system for the study of biological plasticity in humans. While MZ twins are generally considered to be genetically identical, a number of studies have emerged that have demonstrated copy-number differences within a twin pair, particularly in those discordant for disease. The rate of autosomal copy-number variation (CNV) discordance within MZ twin pairs was investigated using a population sample of 376 twin pairs genotyped on Illumina Human610-Quad arrays. After CNV calling using both QuantiSNP and PennCNV followed by manual annotation, only a single CNV difference was observed within the MZ twin pairs, being a 130 KB duplication of chromosome 5. Five other potential discordant CNV were called by the software, but excluded based on manual annotation of the regions. It is concluded that large CNV discordance is rare within MZ twin pairs, indicating that any CNV difference found within phenotypically discordant MZ twin pairs has a high probability of containing the causal gene(s) involved.
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Abstract
Monozygotic (MZ) twins are genetically identical at conception, making them informative subjects for studies on somatic mutations. Copy number variants (CNVs) are responsible for a substantial part of genetic variation, have relatively high mutation rates, and are likely to be involved in phenotypic variation. We conducted a genome-wide survey for post-twinning de novo CNVs in 1,097 MZ twin pairs. Comparisons between MZ twins were made by CNVs measured in DNA from blood or buccal epithelium with the Affymetrix 6.0 microarray and two calling algorithms. In addition, CNV concordance rates were compared between the different sources of DNA, and gene-enrichment association analyses were conducted for thought problems (TP) and attention problems (AP) using CNVs concordant within MZ pairs. We found a total of 153 putative post-twinning de novo CNVs >100 kb, of which the majority resided in 15q11.2. Based on the discordance of raw intensity signals a selection was made of 20 de novo CNVs for a qPCR validation experiments. Two out of 20 post-twinning de novo CNVs were validated with qPCR in the same twin pair. The 13-year-old MZ twin pair that showed two discordances in CN in 15q11.2 in their buccal DNA did not show large phenotypic differences. From the remaining 18 putative de novo CNVs, 17 were deletions or duplications that were concordant within MZ twin pairs. Concordance rates within twin pairs of CNV calls with CN ≠ 2 were ~80%. Buccal epithelium-derived DNA showed a slightly but significantly higher concordance rate, and blood-derived DNA showed significantly more concordant CNVs per twin pair. The gene-enrichment analyses on concordant CNVs showed no significant associations between CNVs overlapping with genes involved in neuronal processes and TP or AP after accounting for the source of DNA.
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Abstract
Chromosome 17q21.31 microdeletion syndrome is a genomic disorder caused by a recurrent 600 kb long deletion. The deletion affects the region of a common inversion present in about 20% of Europeans. The inversion is associated with the H2 haplotype carrying additional low-copy repeats susceptible to non-allelic homologous recombination, and this haplotype is prone to deletion. No instances of 17q21.31 deletions inherited from an affected parent have been reported, and the deletions always affected a parental chromosome with the H2 haplotype. The syndrome is characterized clinically by intellectual disability, hypotonia, friendly behavior and specific facial dysmorphism with long face, large tubular or pear-shaped nose and bulbous nasal tip. We present monozygotic twin sisters showing the typical clinical picture of the syndrome. The phenotype of the sisters was very similar, with a slightly more severe presentation in Twin B. The 17q21.31 microdeletion was confirmed in both patients but in neither of their parents. Potential copy number differences between the genomes of the twins were subsequently searched using high-resolution single nucleotide polymorphism (SNP) and comparative genome hybridisation (CGH) arrays. However, these analyses identified no additional aberrations or genomic differences that could potentially be responsible for the subtle phenotypic differences. These could possibly be related to the more severe perinatal history of Twin B, or to the variable expressivity of the disorder. In accord with the expectations, one of the parents (the mother) was shown to carry the H2 haplotype, and the maternal allele of chromosome 17q21.31 was missing in the twins.
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Absence of substantial copy number differences in a pair of monozygotic twins discordant for features of autism spectrum disorder. Case Rep Genet 2014; 2014:516529. [PMID: 24563798 PMCID: PMC3915920 DOI: 10.1155/2014/516529] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 10/20/2013] [Indexed: 01/12/2023] Open
Abstract
Autism spectrum disorder (ASD) is a highly heritable disease (~0.9) with a complex genetic etiology. It is initially characterized by altered cognitive ability which commonly includes impaired language and communication skills as well as fundamental deficits in social interaction. Despite the large amount of studies described so far, the high clinical diversity affecting the autism phenotype remains poorly explained. Recent studies suggest that rare genomic variations, in particular copy number variation (CNV), may account for a significant proportion of the genetic basis of ASD. The use of disease-discordant monozygotic twins represents a powerful strategy to identify de novo and inherited CNV in the disorder. Here we present the results of a comparative genome hybridization (CGH) analysis with a pair of monozygotic twins affected of ASD with significant differences in their clinical manifestations that specially affect speech language impairment and communication skills. Array CGH was performed in three different tissues: blood, saliva, and hair follicle, in an attempt to identify germinal and somatic CNV regions that may explain these differences. Our results argue against a role of large CNV rearrangements as a molecular etiology of the observed differences. This forwards future research to explore de novo point mutation and epigenomic alterations as potential explanations of the observed clinical differences.
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Kunio M, Yang C, Minakuchi Y, Ohori K, Soutome M, Hirasawa T, Kazuki Y, Adachi N, Suzuki S, Itoh M, Goto YI, Andoh T, Kurosawa H, Akamatsu W, Ohyama M, Okano H, Oshimura M, Sasaki M, Toyoda A, Kubota T. Comparison of Genomic and Epigenomic Expression in Monozygotic Twins Discordant for Rett Syndrome. PLoS One 2013; 8:e66729. [PMID: 23805272 PMCID: PMC3689680 DOI: 10.1371/journal.pone.0066729] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/10/2013] [Indexed: 12/12/2022] Open
Abstract
Monozygotic (identical) twins have been widely used in genetic studies to determine the relative contributions of heredity and the environment in human diseases. Discordance in disease manifestation between affected monozygotic twins has been attributed to either environmental factors or different patterns of X chromosome inactivation (XCI). However, recent studies have identified genetic and epigenetic differences between monozygotic twins, thereby challenging the accepted experimental model for distinguishing the effects of nature and nurture. Here, we report the genomic and epigenomic sequences in skin fibroblasts of a discordant monozygotic twin pair with Rett syndrome, an X-linked neurodevelopmental disorder characterized by autistic features, epileptic seizures, gait ataxia and stereotypical hand movements. The twins shared the same de novo mutation in exon 4 of the MECP2 gene (G269AfsX288), which was paternal in origin and occurred during spermatogenesis. The XCI patterns in the twins did not differ in lymphocytes, skin fibroblasts, and hair cells (which originate from ectoderm as does neuronal tissue). No reproducible differences were detected between the twins in single nucleotide polymorphisms (SNPs), insertion-deletion polymorphisms (indels), or copy number variations. Differences in DNA methylation between the twins were detected in fibroblasts in the upstream regions of genes involved in brain function and skeletal tissues such as Mohawk Homeobox (MKX), Brain-type Creatine Kinase (CKB), and FYN Tyrosine Kinase Protooncogene (FYN). The level of methylation in these upstream regions was inversely correlated with the level of gene expression. Thus, differences in DNA methylation patterns likely underlie the discordance in Rett phenotypes between the twins.
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Affiliation(s)
- Miyake Kunio
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Chunshu Yang
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Yohei Minakuchi
- Comparative Genomics Laboratory, Center for Information Biology, National Institute of Genetics, Mishima, Japan
| | - Kenta Ohori
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Masaki Soutome
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Takae Hirasawa
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Yasuhiro Kazuki
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, Yonago, Japan
| | - Noboru Adachi
- Department of Legal Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
| | - Seiko Suzuki
- Department of Child Neurology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Masayuki Itoh
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Yu-ichi Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Tomoko Andoh
- Department of Biotechnology, Faculty of Life and Environmental Sciences, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Kofu, Japan
| | - Hiroshi Kurosawa
- Department of Biotechnology, Faculty of Life and Environmental Sciences, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Kofu, Japan
| | - Wado Akamatsu
- Department of Physiology, Keio University School of Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Manabu Ohyama
- Department of Dermatology, Keio University School of Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Mitsuo Oshimura
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, Yonago, Japan
| | - Masayuki Sasaki
- Department of Child Neurology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Atsushi Toyoda
- Comparative Genomics Laboratory, Center for Information Biology, National Institute of Genetics, Mishima, Japan
| | - Takeo Kubota
- Department of Epigenetic Medicine, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Japan
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13
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Comprehensive analysis of copy number variation in monozygotic twins discordant for bipolar disorder or schizophrenia. Schizophr Res 2013; 146:289-90. [PMID: 23507357 PMCID: PMC3650833 DOI: 10.1016/j.schres.2013.02.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 02/13/2013] [Accepted: 02/19/2013] [Indexed: 12/20/2022]
Abstract
Copy number variation plays a clear role in the etiology of many psychiatric disorders, particularly schizophrenia. We performed array-CGH to look for copy number variants between five pairs of monozygotic twins discordant for bipolar disorder or schizophrenia. Our study found no differences in copy number variants between the sets of twins. Although alluring, realistic accounting for heterogeneity and chimerism highlights the technological limitations in studying monozygotic twins discordant for psychiatric disorders.
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14
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DNA methylation signatures of peripheral leukocytes in schizophrenia. Neuromolecular Med 2012; 15:95-101. [PMID: 22961555 DOI: 10.1007/s12017-012-8198-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/24/2012] [Indexed: 01/13/2023]
Abstract
Schizophrenia (SCZ) is a complex psychiatric disease with a lifetime morbidity rate of 0.5-1.0 %. To date, aberrant DNA methylation in SCZ has been reported in several studies. However, no comprehensive studies using medication-free subjects with SCZ have been conducted. In addition, most of these studies have been limited to the analysis of the CpG sites in CpG islands (CGIs) in the gene promoter regions, so little is known about the DNA methylation signatures across the whole genome in SCZ. Genome-wide DNA methylation profiling (485,764 CpG sites) of peripheral leukocytes was conducted in the first set of samples (24 medication-free patients with SCZ and 23 non-psychiatric controls) using Infinium HumanMethylation450 Beadchips. Second, a monozygotic twin study was performed using three pairs of monozygotic twins that were discordant for SCZ. Finally, the data from these two independent cohorts were compared. A total of 234 differentially methylated CpG sites that were common between these two cohorts were identified. Of the 234 CpG sites, 153 sites (65.4 %) were located in the CGIs and in the regions flanking CGIs (CGI: 40.6 %; CGI shore: 13.3 %; CGI shelf: 11.5 %). Of the 95 differently methylated CpG sites in the CGIs, most of them were located in the promoter regions (promoter: 75.8 %; gene body: 14.7 %; 3'-UTR: 2.1 %). Aberrant DNA methylation in SCZ was identified at numerous loci across the whole genome in peripheral leukocytes using two independent sets of samples. These findings support the notion that altered DNA methylation could be involved in the pathophysiology of SCZ.
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15
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Czyz W, Morahan JM, Ebers GC, Ramagopalan SV. Genetic, environmental and stochastic factors in monozygotic twin discordance with a focus on epigenetic differences. BMC Med 2012; 10:93. [PMID: 22898292 PMCID: PMC3566971 DOI: 10.1186/1741-7015-10-93] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 08/17/2012] [Indexed: 03/16/2023] Open
Abstract
Genetic-epidemiological studies on monozygotic (MZ) twins have been used for decades to tease out the relative contributions of genes and the environment to a trait. Phenotypic discordance in MZ twins has traditionally been ascribed to non-shared environmental factors acting after birth, however recent data indicate that this explanation is far too simple. In this paper, we review other reasons for discordance, including differences in the in utero environment, genetic mosaicism, and stochastic factors, focusing particularly on epigenetic discordance. Epigenetic differences are gaining increasing recognition. Although it is clear that in specific cases epigenetic alterations provide a causal factor in disease etiology, the overall significance of epigenetics in twin discordance remains unclear. It is also challenging to determine the causality and relative contributions of environmental, genetic, and stochastic factors to epigenetic variability. Epigenomic profiling studies have recently shed more light on the dynamics of temporal methylation change and methylome heritability, yet have not given a definite answer regarding their relevance to disease, because of limitations in establishing causality. Here, we explore the subject of epigenetics as another component in human phenotypic variability and its links to disease focusing particularly on evidence from MZ twin studies.
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Affiliation(s)
- Witold Czyz
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Nuffield Department of Clinical Neurosciences (Clinical Neurology), University of Oxford, Oxford, UK
| | - Julia M Morahan
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Nuffield Department of Clinical Neurosciences (Clinical Neurology), University of Oxford, Oxford, UK
| | - George C Ebers
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Nuffield Department of Clinical Neurosciences (Clinical Neurology), University of Oxford, Oxford, UK
| | - Sreeram V Ramagopalan
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Nuffield Department of Clinical Neurosciences (Clinical Neurology), University of Oxford, Oxford, UK
- Blizard Institute, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, London, UK
- London School of Hygiene and Tropical Medicine, London, UK
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16
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Ollikainen M, Craig JM. Epigenetic discordance at imprinting control regions in twins. Epigenomics 2012; 3:295-306. [PMID: 22122339 DOI: 10.2217/epi.11.18] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Imprinting control regions are differentially methylated in a parent-of-origin-dependent manner and this methylation state is inherited through the germline. These regions control parent-specific monoallelic expression of their target genes. Genetically identical organisms show considerable variation in their epigenomes owing to environmental and stochastic influences creating fluctuations in phenotype. Monozygotic twin pairs discordant for imprinting disorders due to epigenetic changes at imprinting control regions are an example of phenotypic variation caused by extreme variations of the epigenome. Here, we discuss the within-pair epigenetic discordance at imprinted loci, both in phenotypically concordant and discordant monozygotic twin pairs.
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Affiliation(s)
- Miina Ollikainen
- Murdoch Childrens Research Institute & Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia.
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17
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De novo and inherited CNVs in MZ twin pairs selected for discordance and concordance on Attention Problems. Eur J Hum Genet 2012; 20:1037-43. [PMID: 22490988 PMCID: PMC3449078 DOI: 10.1038/ejhg.2012.49] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Copy number variations (CNVs) have been reported to be causal suspects in a variety of psychopathologic traits. We investigate whether de novo and/or inherited CNVs contribute to the risk for Attention Problems (APs) in children. Based on longitudinal phenotyping, 50 concordant and discordant monozygotic (MZ) twin pairs were selected from a sample of ∼3200 MZ pairs. Two types of de novo CNVs were investigated: (1) CNVs shared by both MZ twins, but not inherited (pre-twinning de novo CNVs), which were detected by comparing copy number (CN) calls between parents and twins and (2) CNVs not shared by co-twins (post-twinning de novo CNVs), which were investigated by comparing the CN calls within MZ pairs. The association between the overall CNV burden and AP was also investigated for CNVs genome-wide, CNVs within genes and CNVs outside of genes. Two de novo CNVs were identified and validated using quantitative PCR: a pre-twinning de novo duplication in a concordant-unaffected twin pair and a post-twinning deletion in the higher scoring twin from a concordant-affected pair. For the overall CNV burden analyses, affected individuals had significantly larger CNVs that overlapped with genes than unaffected individuals (P=0.008). This study suggests that the presence of larger CNVs may increase the risk for AP, because they are more likely to affect genes, and confirms that MZ twins are not always genetically identical.
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18
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Breckpot J, Thienpont B, Gewillig M, Allegaert K, Vermeesch JR, Devriendt K. Differences in Copy Number Variation between Discordant Monozygotic Twins as a Model for Exploring Chromosomal Mosaicism in Congenital Heart Defects. Mol Syndromol 2012; 2:81-87. [PMID: 22511896 DOI: 10.1159/000335284] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/14/2011] [Indexed: 12/21/2022] Open
Abstract
Studies addressing the role of somatic copy number variation (CNV) in the genesis of congenital heart defects (CHDs) are scarce, as cardiac tissue is difficult to obtain, especially in non-affected individuals. We explored the occurrence of copy number differences in monozygotic (MZ) twins discordant for the presence of a CHD, as an illustrative model for chromosomal mosaicism in CHDs. Array comparative genomic hybridization was performed on peripheral blood-derived DNA obtained from 6 discordant MZ twin pairs and on sex-matched reference samples. To identify CNV differences between both twin members as well as potential CNVs in both twins contributing to the phenotype, DNA from each twin was hybridized against its co-twin, and against a normal control. Three copy number differences in 1 out of 6 MZ twin pairs were detected, confirming the occurrence of somatic CNV events in MZ twins. Further investigation by copy number and (epi)genome sequencing analyses in MZ twins, discordant for the presence of CHDs, is required to improve our knowledge on how postzygotic genetic, environmental and stochastic factors can affect human heart development.
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Affiliation(s)
- J Breckpot
- Center for Human Genetics, University Hospitals Leuven, Leuven, Belgium
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19
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On parameters of the human genome. J Theor Biol 2011; 288:92-104. [DOI: 10.1016/j.jtbi.2011.07.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 06/28/2011] [Accepted: 07/21/2011] [Indexed: 02/06/2023]
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