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Sun MX, Jing M, Hua Y, Wang JB, Wang SQ, Chen LL, Ju L, Liu YS. A female patient carrying a novel DMD mutation with non-random X-chromosome inactivation from a DMD family. BMC Med Genomics 2024; 17:46. [PMID: 38303044 PMCID: PMC10832127 DOI: 10.1186/s12920-024-01794-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 01/01/2024] [Indexed: 02/03/2024] Open
Abstract
OBJECTIVE To analyze the clinical phenotype and genetic characteristics of a female proband carrying a novel mutation in the DMD gene with non-random X-chromosome inactivation in a large pedigree with pseudohypertrophic muscular dystrophy. METHODS Clinical information of the female proband, her monozygotic twin sister, and other family members were collected. Potential pathogenic variants were detected with Multiplex Ligation-dependent Probe Amplification (MLPA) and whole-exome sequencing (WES). Methylation-sensitive restriction enzyme (HhaI) was employed for X-chromosome inactivation analysis. RESULTS The proband was a female over 5 years old, displayed clinical manifestations such as elevated creatine kinase (CK) levels and mild calf muscle hypertrophy. Her monozygotic twin sister exhibited normal CK levels and motor ability. Her uncle and cousin had a history of DMD. WES revealed that the proband carried a novel variant in the DMD (OMIM: 300,377) gene: NM_004006.3: c.3051_3053dup; NP_003997.2: p.Tyr1018*. In this pedigree, five out of six female members were carriers of this variant, while the cousin and uncle were hemizygous for this variant. X-chromosome inactivation analysis suggested non-random inactivation in the proband. CONCLUSION The c.3051_3053dup (p.Tyr1018*) variant in the DMD gene is considered to be the pathogenic variant significantly associated with the clinical phenotype of the proband, her cousin, and her uncle within this family. Integrating genetic testing with clinical phenotype assessment can be a valuable tool for physicians in the diagnosis of progressive muscular dystrophies, such as Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD).
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Affiliation(s)
- Ming-Xia Sun
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Miao Jing
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Ying Hua
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China.
| | - Jian-Biao Wang
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Sheng-Quan Wang
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Li-Lan Chen
- Department of Neurology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Liang Ju
- Department of Cardiology, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China
| | - Yan-Shan Liu
- Department of Pediatric Laboratory, Affiliated Children's Hospital of Jiangnan University (Wuxi Children's Hospital), Wuxi, China.
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2
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Gaina G, Vossen RHAM, Manole E, Plesca DA, Ionica E. Combining Protein Expression and Molecular Data Improves Mutation Characterization of Dystrophinopathies. Front Neurol 2021; 12:718396. [PMID: 34950096 PMCID: PMC8689184 DOI: 10.3389/fneur.2021.718396] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Duchenne and Becker muscular dystrophy are X-linked recessive inherited disorders characterized by progressive weakness due to skeletal muscle degeneration. Different mutations in the DMD gene, which encodes for dystrophin protein, are responsible for these disorders. The aim of our study was to investigate the relationship between type, size, and location of the mutation that occurs in the DMD gene and their effect on dystrophin protein expression in a cohort of 40 male dystrophinopathy patients and nine females, possible carriers. We evaluated the expression of dystrophin by immunofluorescence and immunoblotting. The mutational spectrum of the DMD gene was established by MLPA for large copy number variants, followed by HRM analysis for point mutations and sequencing of samples with an abnormal melting profile. MLPA revealed 30 deletions (75%) and three duplications (7.5%). HRM analysis accounted for seven-point mutations (17.5%). We also report four novel small mutations (c. 8507G>T, c.3021delG, c.9563_9563+1insAGCATGTTTATGATACAGCA, c.7661-60T>A) in DMD gene. Our work shows that the DNA translational open reading frame and the location of the mutation both influence the expression of dystrophin and disease severity phenotype. The proposed algorithm used in this study demonstrates its accuracy for the characterization of dystrophinopathy patients.
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Affiliation(s)
- Gisela Gaina
- Department of Biochemistry and Molecular Biology, University of Bucharest, Bucharest, Romania
- Laboratory of Cell Biology, Neuroscience and Experimental Myology, Victor Babes National Institute of Pathology, Bucharest, Romania
- *Correspondence: Gisela Gaina ;
| | - Rolf H. A. M. Vossen
- Center for Human and Clinical Genetics, Leiden Genome Technology Center, Leiden, Netherlands
| | - Emilia Manole
- Laboratory of Cell Biology, Neuroscience and Experimental Myology, Victor Babes National Institute of Pathology, Bucharest, Romania
- Colentina Clinical Hospital, Bucharest, Romania
| | - Doina Anca Plesca
- Department of Pediatrics, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
- Department of Clinical Pediatrics, Victor Gomoiu Children Clinical Hospital, Bucharest, Romania
| | - Elena Ionica
- Department of Biochemistry and Molecular Biology, University of Bucharest, Bucharest, Romania
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3
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Shi D, Motamed M, Mejía-Benítez A, Li L, Lin E, Budhram D, Kaur Y, Meyre D. Genetic syndromes with diabetes: A systematic review. Obes Rev 2021; 22:e13303. [PMID: 34268868 DOI: 10.1111/obr.13303] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 05/19/2021] [Accepted: 05/20/2021] [Indexed: 01/19/2023]
Abstract
Previous reviews and clinical guidelines have identified 10-20 genetic syndromes associated with diabetes, but no systematic review has been conducted to date. We provide the first comprehensive catalog for syndromes with diabetes mellitus. We conducted a systematic review of MEDLINE, Embase, CENTRAL, PubMed, OMIM, and Orphanet databases for case reports, case series, and observational studies published between 1946 and January 15, 2020, that described diabetes mellitus in adults and children with monogenic or chromosomal syndromes. Our literature search identified 7,122 studies, of which 160 fulfilled inclusion criteria. Our analysis of these studies found 69 distinct diabetes syndromes. Thirty (43.5%) syndromes included diabetes mellitus as a cardinal clinical feature, and 56 (81.2%) were fully genetically elucidated. Sixty-three syndromes (91.3%) were described more than once in independent case reports, of which 59 (93.7%) demonstrated clinical heterogeneity. Syndromes associated with diabetes mellitus are more numerous and diverse than previously anticipated. While knowledge of the syndromes is limited by their low prevalence, future reviews will be needed as more cases are identified. The genetic etiologies of these syndromes are well elucidated and provide potential avenues for future gene identification efforts, aid in diagnosis and management, gene therapy research, and developing personalized medicine treatments.
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Affiliation(s)
- Daniel Shi
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.,Faculty of Medicine, Queen's University, Kingston, Ontario, Canada
| | - Mehras Motamed
- Faculty of Medicine, Queen's University, Kingston, Ontario, Canada
| | - Aurora Mejía-Benítez
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada
| | - Leon Li
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada
| | - Ethan Lin
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.,Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Dalton Budhram
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.,Faculty of Medicine, Queen's University, Kingston, Ontario, Canada
| | - Yuvreet Kaur
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.,Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - David Meyre
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.,Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, and Nutrition, University Hospital of Nancy, Nancy, France.,Faculty of Medicine of Nancy INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure, University of Lorraine, Nancy, France
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4
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Barnes‐Davis ME, Cortezzo DE. Two cases of atypical twinning: Phenotypically discordant monozygotic and conjoined twins. Clin Case Rep 2019; 7:920-925. [PMID: 31110715 PMCID: PMC6509934 DOI: 10.1002/ccr3.2113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 03/01/2019] [Accepted: 03/03/2019] [Indexed: 12/13/2022] Open
Abstract
Atypical twinning highlights that complex mechanisms responsible for twinning are not fully understood and may give further insight into the mechanisms involved. To assume that phenotypic difference is the result of dizygotic twinning would be erroneous and could have significant implications in the care and counseling provided to these patients.
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Affiliation(s)
- Maria E. Barnes‐Davis
- Department of PediatricsUniversity of Cincinnati College of MedicineCincinnatiOhio
- Division of Neonatal and Pulmonary BiologyCincinnati Children’s Hospital Medical CenterCincinnatiOhio
| | - DonnaMaria E. Cortezzo
- Department of PediatricsUniversity of Cincinnati College of MedicineCincinnatiOhio
- Division of Neonatal and Pulmonary BiologyCincinnati Children’s Hospital Medical CenterCincinnatiOhio
- Department of AnesthesiologyUniversity of Cincinnati College of MedicineCincinnatiOhio
- Division of Pain and Palliative MedicineCincinnati Children’s Hospital Medical CenterCincinnatiOhio
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5
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Reyngoudt H, Turk S, Carlier PG. 1 H NMRS of carnosine combined with 31 P NMRS to better characterize skeletal muscle pH dysregulation in Duchenne muscular dystrophy. NMR IN BIOMEDICINE 2018; 31:e3839. [PMID: 29130550 DOI: 10.1002/nbm.3839] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 05/18/2023]
Abstract
In recent years, quantitative nuclear magnetic resonance imaging and spectroscopy (NMRI and NMRS) have been used more systematically as outcome measures in natural history and clinical trial studies for Duchenne muscular dystrophy (DMD). Whereas most of these studies have emphasized the evaluation of the fat fraction as an assessment for disease severity, less focus has been placed on metabolic indices measured by NMRS. 31 P NMRS in DMD reveals an alkaline inorganic phosphate (Pi ) pool, originating from either leaky dystrophic myocytes or an increased interstitial space. 1 H NMRS, exploiting the pH-sensitive proton resonances of carnosine, an intracellular dipeptide, was used to distinguish between these two hypotheses. NMR data were obtained in 23 patients with DMD and 14 healthy subjects on a 3-T clinical NMR system. Both 31 P and 1 H NMRS data were acquired at the level of the gastrocnemius medialis muscle. A multi-slice multi-echo imaging acquisition was performed for the determination of water T2 and fat fraction in the same region of interest. Whereas nearly all patients with DMD showed an elevated pH compared with healthy controls when using 31 P NMRS, 1 H NMRS-determined pH was not systematically increased. As expected, the carnosine-based intracellular pH was never found to be alkaline in the absence of a concurrent Pi -based pH elevation. In addition, abnormal intracellular pH, based on carnosine, was never associated with normal water T2 values. We conclude that, in one group of patients, both 1 H and 31 P NMRS showed an alkaline pH, originating from the intracellular compartment and reflecting ionic dysregulation in dystrophic myocytes. In the other patients with DMD, intracellular pH was normal, but an alkaline Pi pool was still present, suggesting an extracellular origin, probably revealing an expanded interstitial volume fraction, often associated with fibrotic changes. The data demonstrate that 1 H NMRS could serve as a biomarker to assess the normalization of intramyocytic pH and sarcolemmal permeability following therapy inducing dystrophin expression in patients with DMD.
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Affiliation(s)
- Harmen Reyngoudt
- NMR Laboratory, Institute of Myology, Paris, France
- CEA, DRF, IBFJ, MIRCen, Paris, France
| | - Suna Turk
- NMR Laboratory, Institute of Myology, Paris, France
- CEA, DRF, IBFJ, MIRCen, Paris, France
| | - Pierre G Carlier
- NMR Laboratory, Institute of Myology, Paris, France
- CEA, DRF, IBFJ, MIRCen, Paris, France
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6
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Burgemeister AL, Zirn B, Oeffner F, Kaler SG, Lemm G, Rossier E, Büttel HM. Menkes disease with discordant phenotype in female monozygotic twins. Am J Med Genet A 2015; 167A:2826-9. [PMID: 26239182 DOI: 10.1002/ajmg.a.37276] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 07/15/2015] [Indexed: 12/22/2022]
Abstract
Menkes disease (MD) is a rare X-linked recessive disorder caused by mutations in the ATP7A gene. This neurodegenerative disorder typically affects males and is characterized by impaired copper distribution and the malfunction of several copper-dependent enzymes. We report clinically discordant female monozygotic twins (MZT) with a heterozygous ATP7A mutation. One twin girl is healthy at the current age of 4 years, whereas the other twin girl developed classical MD, showed disease stabilization under copper histidine treatment but died at the age of 3 years. Presumably, the affected girl developed MD due to skewed X inactivation, although this could not be demonstrated in two tissues (blood, buccal mucosa). This case is a rare example of an affected girl with MD and shows the possibility of a discordant phenotype in MZT girls. As speculated in other X-linked diseases, the process of monozygotic twinning may be associated with skewed X inactivation leading to a discordant phenotype.
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Affiliation(s)
| | - Birgit Zirn
- Genetikum, Genetic Counseling and Diagnostic, Stuttgart and Neu-Ulm, Germany.,Department of Pediatrics and Neuropediatrics, University Medicine, Göttingen, Germany
| | - Frank Oeffner
- Genetikum, Genetic Counseling and Diagnostic, Stuttgart and Neu-Ulm, Germany
| | - Stephen G Kaler
- Section on Translational Neuroscience, Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Gunther Lemm
- Department of Radiology, SLK-Klinikum, Heilbronn, Germany
| | - Eva Rossier
- Genetikum, Genetic Counseling and Diagnostic, Stuttgart and Neu-Ulm, Germany
| | - Hans-Martin Büttel
- Department of Pediatrics and Neuropediatrics, SLK-Klinikum, Heilbronn, Germany
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7
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Manoukian S, Verderio P, Tabano S, Colapietro P, Pizzamiglio S, Grati FR, Calvello M, Peissel B, Burn J, Pensotti V, Allemani C, Sirchia SM, Radice P, Miozzo M. X chromosome inactivation pattern in BRCA gene mutation carriers. Eur J Cancer 2013; 49:1136-41. [PMID: 23146957 DOI: 10.1016/j.ejca.2012.10.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/12/2012] [Accepted: 10/08/2012] [Indexed: 10/27/2022]
Abstract
An association of preferential X chromosome inactivation (XCI) with BRCA gene status and breast/ovarian cancer risk has been reported. We evaluated XCI in a large group of BRCA mutation carriers compared to non-carriers and investigated associations between preferential XCI (⩾90:10) and age, mutated gene, cancer development and chemotherapy. XCI was analysed by human androgen receptor (HUMARA) assay and pyrosequencing in 437 BRCA1 or BRCA2 mutation carriers and 445 age-matched controls. The distribution of XCI patterns in the two groups was compared by logistic regression analysis. The association between preferential XCI and selected variables was investigated in both univariate and multivariate fashion. In univariate analyses preferential XCI was not significantly associated with the probability of being a BRCA mutation carrier, nor with cancer status, whereas chemotherapeutic regime and age both showed a significant association. In multivariate analysis only age maintained significance (odds ratio, 1.056; 95% confidence interval, 1.016-1.096). Our findings do not support the usefulness of XCI analysis for the identification of BRCA mutation carriers and cancer risk assessment. The increasing preferential XCI frequency with ageing and the association with chemotherapy justify extending the investigation to other categories of female cancer patients to identify possible X-linked loci implicated in cell survival.
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Affiliation(s)
- Siranoush Manoukian
- Unit of Medical Genetics, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
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8
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Abstract
AbstractFellman and Eriksson (2010) cited my suggestion that the sex ratio (proportion male) of monozygotic (MZ) twins is lower than that of dizygotic (DZ) twins (James 1975). Here I offer elaborations on and potential explanations for this.
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9
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Derom C, Vlietinck R, Derom R. Timing of Twinning, X-Inactivation and Sex Proportion at Birth. Twin Res Hum Genet 2012. [DOI: 10.1375/twin.10.supp.8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractTwins are not a homogeneous group. According to zygosity and chorionicity essential differences exist. The lower sex proportion at birth is due to the monozygotic twins, especially the monoamnionic variety. X-inactivation patterns in monozygotic twin girls are totally symmetrical in monoamnionic pairs, almost symmetrical in monochorionic diamnionic pairs and can be very asymmetrical in the dichorionic variety.
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10
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Blickstein I, Keith LG. On the Possible Cause of Monozygotic Twinning: Lessons From the 9-Banded Armadillo and From Assisted Reproduction. Twin Res Hum Genet 2012; 10:394-9. [PMID: 17564530 DOI: 10.1375/twin.10.2.394] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractAvailable hypotheses proposed to explain the mechanism of zygotic splitting fail to explain why monozygotic twins are more prevalent after all methods of assisted reproduction and which structure is likely to control this phenomenon. Arguably, a small proportion of oocytes might have an inborn propensity to undergo splitting upon fertilization leading to the constant prevalence of spontaneous monozygotic conceptions among different populations. Ovarian stimulation would then predictably increase the number of available splitting-prone oocytes and consequently would increase the chance for such oocytes to develop into monozygotic twins, leading to a ‘dose’-dependent relationship between monozygosity rates and the combined effect of infertility treatment. Embryonic division into 2 distinct cell lines begins and accommodates within an intact zona pellucida that controls the process by preventing ill-timed hatching. Human fertilized oocytes are able to undergo 2 binary fissions, just as is the case for the 9-banded armadillo (the only other mammal that produces monozygotic quadruplets) and to give rise to a variety of combinations of monozygotic pregnancies. This hypothetical explanation does not negate the already existing and genetically sound hypotheses, but places them into a broader perspective that respects recent observations from modern infertility treatment.
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Affiliation(s)
- Isaac Blickstein
- Department of Obstetrics and Gynecology, Kaplan Medical Center, Rehovot and the Hadassah-Hebrew University School of Medicine, Jerusalem, Israel.
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11
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Zhou JY, Pu JL, Chen S, Hong Y, Ling CH, Zhang JM. Mirror-image arachnoid cysts in a pair of monozygotic twins: a case report and review of the literature. Int J Med Sci 2011; 8:402-5. [PMID: 21750644 PMCID: PMC3133845 DOI: 10.7150/ijms.8.402] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Accepted: 05/23/2011] [Indexed: 11/12/2022] Open
Abstract
Mirror-imaging of arachnoid cysts (ACs) in monozygotic twins (MZ) is extremely rare. We describe a pair of MZ who developed mirror-imaging of ACs in the temporal fossas, and we also review the literature. Brain computer tomography (CT) and Magnetic Resonance Imaging (MRI) of the MZ revealed mirror-imaging of vast lesions of cerebrospinal fluid intensity in their temporal fossas. This is the second ever report of such a case according to the available literature. Unlike the prior case, our patients were 14 months, which is a much younger age than the patients of the previous report. Consequently, our case is better in supporting a genetic origin in the pathogenesis of AC. The findings in our case indicate that early neuroimaging is mandatory in the counterpart of the symptomatic patient with AC, irrespective of the absence of symptoms.
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Affiliation(s)
- Jing-Yi Zhou
- 1. Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Jia-Li Pu
- 2. Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Sheng Chen
- 1. Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yuan Hong
- 1. Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Chen-Han Ling
- 1. Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Jian-Min Zhang
- 1. Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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12
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Zwijnenburg PJG, Meijers-Heijboer H, Boomsma DI. Identical but not the same: the value of discordant monozygotic twins in genetic research. Am J Med Genet B Neuropsychiatr Genet 2010; 153B:1134-49. [PMID: 20468073 DOI: 10.1002/ajmg.b.31091] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called "genetically identical"; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post-zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders.
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Affiliation(s)
- Petra J G Zwijnenburg
- Department of Clinical Genetics, VU University Medical Center, de Boelelaan 1117, Amsterdam, the Netherlands.
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13
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Pinto LLC, Vieira TA, Giugliani R, Schwartz IVD. Expression of the disease on female carriers of X-linked lysosomal disorders: a brief review. Orphanet J Rare Dis 2010; 5:14. [PMID: 20509947 PMCID: PMC2889886 DOI: 10.1186/1750-1172-5-14] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 05/28/2010] [Indexed: 01/01/2023] Open
Abstract
Most lysosomal diseases (LD) are inherited as autosomal recessive traits, but two important conditions have X-linked inheritance: Fabry disease and Mucopolysaccharidosis II (MPS II). These two diseases show a very different pattern regarding expression on heterozygotes, which does not seem to be explained by the X-inactivation mechanism only. While MPS II heterozygotes are asymptomatic in most instances, in Fabry disease most of female carriers show some disease manifestation, which is sometimes severe. It is known that there is a major difference among X-linked diseases depending on the cell autonomy of the gene product involved and, therefore, on the occurrence of cross-correction. Since lysosomal enzymes are usually secreted and uptaken by neighbor cells, the different findings between MPS II and Fabry disease heterozygotes can also be due to different efficiency of cross-correction (higher in MPS II and lower in Fabry disease). In this paper, we review these two X-linked LD in order to discuss the mechanisms that could explain the different rates of penetrance and expressivity observed in the heterozygotes; this could be helpful to better understand the expression of X-linked traits.
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Affiliation(s)
- Louise L C Pinto
- Postgraduate Program in Child and Adolescent Health, UFRGS, Porto Alegre, Brazil.
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14
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Martínez-Frías ML. Epidemiology of acephalus/acardius monozygotic twins: new insights into an epigenetic causal hypothesis. Am J Med Genet A 2009; 149A:640-9. [PMID: 19291778 DOI: 10.1002/ajmg.a.32741] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Apart from a series of 10 acephalus/acardius (Ac/Ac) cases described from a pathological point of view, and the analysis of a review of published cases, we have been unable to find any epidemiological studies on Ac/Ac. Using data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), we present here what seems to be the first epidemiological analysis of a consecutive series of the Ac/Ac type of monozygotic twins (MZT). Among a total of 2,281,604 consecutive births, 11 cases of Ac/Ac MZT were detected, giving a frequency of 0.48 per 100,000 births. However, we consider the period 1980-1985 as the baseline for our data, as in this period voluntary termination of pregnancy was not possible in Spain, and the frequency of Ac/Ac MZT was 0.49 per 100,000 births. Nonetheless, this frequency should be considered as a minimal estimation. The characteristics of these Ac/Ac cases indicate that they are more frequent in males (sex ratio 2.67). In addition, gestational age in Ac/Ac cases was 2.41 and 3.12 weeks lower than in malformed and control twins, respectively. Similarly, their mothers are 4.54 and 4.68 years younger than mothers of separate malformed and control twins, respectively. To understand the biological basis behind the occurrence of MZT in the context of recent observations, we evaluate the hypothesis that the epigenetic processes involved in the early cleavage of the embryo, and in blastocyst formation during development, may be implicated in twinning.
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MESH Headings
- Abnormalities, Multiple/embryology
- Abnormalities, Multiple/epidemiology
- Abnormalities, Multiple/genetics
- Anencephaly/embryology
- Anencephaly/epidemiology
- Anencephaly/genetics
- Case-Control Studies
- Databases, Genetic
- Epigenesis, Genetic
- Female
- Heart Defects, Congenital/embryology
- Heart Defects, Congenital/epidemiology
- Heart Defects, Congenital/genetics
- Humans
- Infant, Newborn
- Male
- Models, Genetic
- Pregnancy
- Sex Ratio
- Spain/epidemiology
- Twins, Monozygotic
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Affiliation(s)
- María Luisa Martínez-Frías
- ECEMC, Centro de Investigación sobre Anomalías Congénitas, Instituto de Salud Carlos III, Madrid, Spain.
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15
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Orstavik KH. X chromosome inactivation in clinical practice. Hum Genet 2009; 126:363-73. [PMID: 19396465 DOI: 10.1007/s00439-009-0670-5] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 04/07/2009] [Indexed: 01/19/2023]
Abstract
X chromosome inactivation (XCI) is the transcriptional silencing of the majority of genes on one of the two X chromosomes in mammalian females. Females are, therefore, mosaics for two cell lines, one with the maternal X and one with the paternal X as the active chromosome. The relative proportion of the two cell lines, the X inactivation pattern, may be analyzed by simple assays in DNA from available tissues. This review focuses on medical issues related to XCI in X-linked disorders, and on the value of X inactivation analysis in clinical practice.
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Affiliation(s)
- Karen Helene Orstavik
- Department of Medical Genetics, Oslo University Hospital, Rikshospitalet and Faculty Division Rikshospitalet, University of Oslo, Forskningsveien 2B, 0027, Oslo, Norway.
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De Gregorio L, Jinnah HA, Harris JC, Nyhan WL, Schretlen DJ, Trombley LM, O'Neill JP. Lesch-Nyhan disease in a female with a clinically normal monozygotic twin. Mol Genet Metab 2005; 85:70-7. [PMID: 15862283 DOI: 10.1016/j.ymgme.2004.11.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 11/20/2004] [Accepted: 11/22/2004] [Indexed: 11/18/2022]
Abstract
Lesch-Nyhan disease (LND) is an inborn error of purine metabolism caused by defective activity of the enzyme hypoxanthine guanine phosphoribosyl transferase (HPRT, EC 2.4.2.8), resulting from mutation in the corresponding gene on the long arm of the X chromosome (Xq26). The classic phenotype occurs almost exclusively in males and is characterized by hyperuricemia, mental retardation, severe dystonia, and self-injurious behavior. Heterozygous carrier females are usually clinically normal. However, a small number of clinically affected females have been described. In all previous cases there was a mutation in one HPRT allele and non-random inactivation of the X chromosome carrying the normal HPRT gene. We have analyzed a female MZ twin pair discordant for Lesch-Nyhan disease. The mother and both twins are heterozygous carriers of a HPRT splicing mutation (IVS8 + 4A > G; c.609 + 4A > G) and all three express the mutant allele at similar frequencies in peripheral blood T cells. The mother and one sister are clinically normal. In the affected twin, the clinical phenotype is classical for Lesch-Nyhan disease, despite the fact that HPRT activity in the blood was also normal. X inactivation analysis showed a skewed pattern in the fibroblasts of the affected twin sister, with the X chromosome carrying the normal HPRT allele preferentially inactivated. As in many other reported cases of X-linked diseases, the discordant phenotype of the two monozygous twin sisters suggests that the process responsible for monozygotic twinning can trigger skewed X inactivation.
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Craig IW, Harper E, Loat CS. The genetic basis for sex differences in human behaviour: role of the sex chromosomes. Ann Hum Genet 2004; 68:269-84. [PMID: 15180708 DOI: 10.1046/j.1529-8817.2004.00098.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The nature of the mechanisms underlying observed sex differences in human behaviour continues to be debated. This review concentrates on the thesis that genes on the sex chromosomes other than those directly controlling sex determination, and whose functions are, at least in part, independent from hormonal influences, play a significant role in determining gender differences in behaviour. To provide an adequate basis for examining this issue, the current understanding of the nature of sex determination, differences in behaviour and the influences of sex hormones are evaluated. The possible contribution to behavioural differences of those X-linked genes which escape inactivation, or which may be subjected to imprinting, is discussed. The review concludes with a summary of the genetic basis for two sexually disparate types of behaviour.
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Affiliation(s)
- Ian W Craig
- SGDP Centre, Box PO 82, Institute of Psychiatry, Denmark Hill, London SE5, UK.
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Resendes BL, Sohn SH, Stelling JR, Tineo R, Davis AJ, Gray MR, Reindollar RH. Role for anti-Müllerian hormone in congenital absence of the uterus and vagina. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 98:129-36. [PMID: 11223848 DOI: 10.1002/1096-8628(20010115)98:2<129::aid-ajmg1021>3.0.co;2-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Molecular genetic techniques were used to determine if mutations in the genes encoding anti-Müllerian hormone (AMH) (also known as Müllerian inhibiting substance (MIS)) and its receptor (AMHR) are commonly present in patients with congenital absence of the uterus and vagina (CAUV). Twenty-two CAUV patients and 96 control subjects from diverse ethnic groups were studied after obtaining informed consent. Genomic DNA samples prepared from leukocytes were digested separately with several different restriction enzymes, and the resultant fragments were analyzed for restriction fragment melting polymorphisms (RFMPs) by denaturing gradient gel electrophoresis (DGGE). Electrophoretic mobility of DNA fragments which were 200-700 base pairs in length was compared using polyacrylamide gels that included linear gradients of denaturing solvents designed to separate DNA fragments according to sequence-dependent variation in thermal stability. Two RFMPs were found in the AMH gene in both patients and normal control subjects. One RFMP in the AMHR gene was present at low frequencies in both patients and normal control subjects. No RFMPs specific to CAUV patients were found in either gene. Because no mutations or rare DNA sequence polymorphisms were detected in the AMH and the AMHR genes in this group of CAUV patients, it is unlikely that either gene commonly has an etiologic role in CAUV.
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Affiliation(s)
- B L Resendes
- Department of Obstetrics and Gynecology, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA
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Kriplani A, Banerjee N, Takkar D. Etiology and management of monoamniotic twin discordant for anencephaly. ACTA GENETICAE MEDICAE ET GEMELLOLOGIAE 1999; 47:51-5. [PMID: 10335354 DOI: 10.1017/s0001566000000374] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A case of monoamniotic monochorionic (MAMC) female twins, with one twin being anencephalic, and the co-twin being normal, is reported. Twin to twin transfusion syndrome was also noted. The reasons for anencephaly in association with monozygotic (MZ) twinning are discussed. The management of such a case is presented.
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Affiliation(s)
- A Kriplani
- Department of Obstetrics and Gynaecology, All India Institute of Medical Sciences, New Delhi, India
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Sebire NJ, Sepulveda W, Hughes KS, Noble P, Nicolaides KH. Management of twin pregnancies discordant for anencephaly. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1997; 104:216-9. [PMID: 9070142 DOI: 10.1111/j.1471-0528.1997.tb11048.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To examine options of management and outcome of twin pregnancies discordant for anencephaly. DESIGN Retrospective study. SETTING Research Centre for Fetal Medicine. POPULATION Twenty-four twin pregnancies discordant for anencephaly. METHODS A computer search was made of our database for twin pregnancies discordant for anencephaly. The data were reviewed for gestation at presentation, chorionicity, management and pregnancy outcome. MAIN OUTCOME MEASURES Pregnancy outcome in relation to chorionicity and management. RESULTS There were 13 dichorionic and 11 monochorionic twin pregnancies discordant for anencephaly. In the dichorionic group five pregnancies had selective fetocide at 17 to 21 weeks; one pregnancy resulted in spontaneous abortion but in the others a healthy infant was born at a median gestation of 37 weeks. The other eight dichorionic pregnancies were managed expectantly, but three developed polyhydramios at 26 to 30 weeks; in one case amniodrainage was performed and in another selective fetocide was carried out. In this group the median gestation at delivery was 35 weeks. All 11 monochorionic pregnancies were managed expectantly and in three there was intrauterine death of both fetuses. In the other eight cases the normal twin was liveborn at a median gestation of 34 weeks; in four of these pregnancies polyhydramnios developed and two were managed by amniodrainage. CONCLUSIONS In monochorionic pregnancies, expectant management is associated with a high rate of intrauterine lethality of the normal twin. In dichorionic pregnancies selective fetocide in the second trimester prevents the development of polyhydramnios and is associated with a lower risk of preterm delivery but can cause miscarriage.
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Affiliation(s)
- N J Sebire
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, Medical School, London, UK
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22
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Abstract
A case of identical (monozygotic) triplets, two of whom have agenesis of the corpus callosum, is presented. Prenatal ultrasonography and magnetic resonance imaging revealed two of the triplets to have agenesis of the corpus callosum and the third triplet to have an intact corpus callosum. No such case has been reported in the literature. Theories of the etiology and pathogenesis of corpus callosum agenesis are discussed. In this case, unequal X-inactivation as related to the twinning process is implicated as the cause of the agenesis.
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Affiliation(s)
- J R Ruge
- Division of Neurosurgery, Lutheran General Hospital, Park Ridge, Illinois, USA
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Hall JG, Lopez-Rangel E. Embryologic development and monozygotic twinning. ACTA GENETICAE MEDICAE ET GEMELLOLOGIAE 1996; 45:53-7. [PMID: 8872010 DOI: 10.1017/s0001566000001094] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In 1875, Sir Francis Galton was the first to propose that by comparing the concordance of a specific trait or disorder in monozygotic (MZ) twins (assumed to be genetically identical) and dizygotic (DZ) twins (which were assumed to be as similar or as different as any other pair of sibs), it would be possible to distinguish between environmental and heritable effects. DZ twins are derived from the fertilization of two eggs by two sperm. MZ twins are the result of the fertilization of one egg by one sperm that then divides to form two embryos.Genetic research has made amazing progress since 1875. Advances in molecular DNA techniques and developmental genetics have made it possible to differentiate unequivocally between MZ and DZ twins [1, 14]. It is in this new light that this manuscript will review the recent knowledge about twins and the twinning process.The incidence of DZ twins differs between population [11, 18]. A DZ twin birth in North America is estimated to occur 9–11 times in every 1000 live births or 1 in 100 births; i.e. 1 in every 50 people is a DZ twin.The DZ twinning rate is closely related to maternal age, parity, height, weight and gonadotropin levels. An increased DZ twinning rate is seen with increasing maternal age and peaks around 35–39 years; higher parity is also associated with a higher DZ twinning rate [19]. Tall heavy women are more likely to give birth to DZ twins than short thin women. A higher incidence of DZ twins has also been reported with the use of new reproductive techniques.
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Affiliation(s)
- J G Hall
- Department of Pediatrics, University of British Columbia, Vancouver, Canada
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Goodship J, Carter J, Burn J. X-inactivation patterns in monozygotic and dizygotic female twins. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 61:205-8. [PMID: 8741864 DOI: 10.1002/(sici)1096-8628(19960122)61:3<205::aid-ajmg3>3.0.co;2-t] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We have tested the hypothesis that contrasting X-inactivation patterns could be a trigger for monozygotic twinning in females. X-inactivation patterns were studied in umbilical cord tissue in 43 monozygotic twin pairs and 24 dizygotic twin pairs. Very skewed or non-random X-inactivation patterns were observed in both twins in six of the monozygotic twin pairs and in one of the dizygotic twin pairs. Contrasting X-inactivation patterns occurred in only one of the six monozygotic twin pairs. This does not support the original hypothesis. There is a trend to extreme skewing of X-inactivation pattern occurring more frequently in monozygotic twins.
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Affiliation(s)
- J Goodship
- Department of Human Genetics, University of Newcastle Upon Tyne, United Kingdom
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Bamforth F, Machin G, Innes M. X-chromosome inactivation is mostly random in placental tissues of female monozygotic twins and triplets. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 61:209-15. [PMID: 8741865 DOI: 10.1002/(sici)1096-8628(19960122)61:3<209::aid-ajmg4>3.0.co;2-p] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Patterns of X-chromosome inactivation in chorion, amnion, and cord from 79 pairs of twins were examined. Seven sets of triplets were included in the analysis, both as twin pairs and triplets. Twins were stratified as dizygotic (DZ), monozygotic (MZ), monochorionic, and dichorionic and were selected for birth weight discordance, discordance for congenital anomalies, twin-twin transfusion syndrome, and various patterns of vascular anastomosis. X-inactivation was predominantly symmetric. Chorion was the most likely tissue to show asymmetric X-inactivation and was found most frequently in MZ dichorionic twins. There was no correlation of X-inactivation pattern with the selected clinical criteria. This study does not confirm that asymmetric X-inactivation in embryonic tissues is a common phenomenon in female twins, including monozygotic twins.
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Affiliation(s)
- F Bamforth
- Department of Laboratory Medicine and Pathology, University of Alberta Hospitals, Edmonton, Canada
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Abstract
The use of the adjective "identical" rather than monozygotic leads to misunderstandings about the biology of monozygotic twinning. Most monozygotic twin pairs are not identical; there may be major discordance for birth weight, genetic disease, and congenital anomalies. These indicate that postzygotic events may lead to the formation of two or more cell clones in the inner cell mass and early embryo that actually stimulate the monozygotic twinning event. There is also evidence that there may be unequal allocation of numbers of cells to the monozygotic twins; this may have widespread implications for the cascade of developmental events during embryogenesis, formation, and vascularization of the placenta. Large-scale zygosity testing at birth could be the template for analysis of twin outcomes and their biologic causes.
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Affiliation(s)
- G A Machin
- Department of Laboratory Medicine and Pathology, University of Alberta Hospitals, Edmonton, Canada
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Migeon BR, Dunn MA, Thomas G, Schmeckpeper BJ, Naidu S. Studies of X inactivation and isodisomy in twins provide further evidence that the X chromosome is not involved in Rett syndrome. Am J Hum Genet 1995; 56:647-53. [PMID: 7887418 PMCID: PMC1801188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Rett syndrome (RS), a progressive encephalopathy with onset in infancy, has been attributed to an X-linked mutation, mainly on the basis of its occurrence almost exclusively in females and its concordance in female MZ twins. The underlying mechanisms proposed are an X-linked dominant mutation with male lethality, uniparental disomy of the X chromosome, and/or some disturbance in the process of X inactivation leading to unequal distributions of cells expressing maternal or paternal alleles (referred to as a "nonrandom" or "skewed" pattern of X inactivation). To determine if the X chromosome is in fact involved in RS, we studied a group of affected females including three pairs of MZ twins, two concordant for RS and one uniquely discordant for RS. Analysis of X-inactivation patterns confirms the frequent nonrandom X inactivation previously observed in MZ twins but indicates that this is independent of RS. Analysis of 29 RS females reveals not one instance of uniparental X disomy, extending the observations previously reported. Therefore, our findings contribute no support for the hypothesis that RS is an X-linked disorder. Furthermore, the concordant phenotype in most MZ female twins with RS, which has not been observed in female twins with known X-linked mutations, argues against an X mutation.
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Affiliation(s)
- B R Migeon
- Center for Medical Genetics, Johns Hopkins University, Baltimore, MD
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30
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Tiberio G. MZ female twins discordant for X-linked diseases: a review. ACTA GENETICAE MEDICAE ET GEMELLOLOGIAE 1994; 43:207-14. [PMID: 8588495 DOI: 10.1017/s0001566000001963] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The 20 reported cases of MZ female twins discordant for X-linked diseases are reviewed. In such twins the X-inactivation pattern is opposite skewing (abnormal allele inactivated in most cells of the normal twin, and normal allele inactivated in most cells of the affected twin) or skewing in one twin and random in the cotwin. The diseases involved map in two specific regions: Xq27-28 and Xp21. The only exceptions are Fabry's disease and Aicardi's syndrome, which map in Xq22 and Xp22 respectively. No concordant MZ female carrier twins, either normal or affected, have been described. Three main hypotheses have been proposed to explain such characteristics [2, 5, 14], but none is completely satisfactory. The constant discordance for X-linked diseases in MZ female twins has important consequences for genetic counselling.
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Affiliation(s)
- G Tiberio
- Centro Pediatrico Internazionale Luigi Gedda, Gregor Mendel Institute, Rome
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31
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Watkiss E, Webb T, Rysiecki G, Girdler N, Hewett E, Bundey S. X inactivation patterns in female monozygotic twins and their families. J Med Genet 1994; 31:754-7. [PMID: 7837250 PMCID: PMC1050120 DOI: 10.1136/jmg.31.10.754] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
X inactivation studies have been carried out on 22 pairs of female monozygotic twins, one set of female monozygotic triplets, and their mothers and singleton sisters, using the probe M27 beta. Forty-eight per cent of the twins, 55% of their mothers, and 42% of their singleton sisters showed skewed X inactivation. Two of the triplets and their mother had random X inactivation, while the third triplet showed skewed X inactivation. Their singleton sister was homozygous with M27 beta. Of the twins, six pairs showed skewed X inactivation in favour of the same X chromosome, one pair showed skewed X inactivation favouring opposite X chromosomes, in seven pairs one twin showed skewed X inactivation while her co-twin showed random X inactivation, and in eight pairs both twins were random. A higher frequency of skewed pattern of X inactivation was not observed in the monozygotic twins when compared to a series of non-twin females (mothers and singleton sisters) and, so, the results in this study do not lend support to the theory that skewed X inactivation predisposes to the twinning process.
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Affiliation(s)
- E Watkiss
- Department of Clinical Genetics, Birmingham Maternity Hospital, Edgbaston, UK
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Abbadi N, Philippe C, Chery M, Gilgenkrantz H, Tome F, Collin H, Theau D, Recan D, Broux O, Fardeau M. Additional case of female monozygotic twins discordant for the clinical manifestations of Duchenne muscular dystrophy due to opposite X-chromosome inactivation. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 52:198-206. [PMID: 7802009 DOI: 10.1002/ajmg.1320520215] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A pair of female monozygotic (MZ) twins, heterozygous carriers for a deletion in the DMD gene and discordant for the clinical manifestations of Duchenne muscular dystrophy, were analyzed by molecular studies, in situ hybridization, and methylation pattern of X chromosomes to search for opposite X inactivation as an explanation of their clinical discordance. Results in lymphocytes and skin fibroblast cell lines suggest a partial mirror inactivation with the normal X chromosome preferentially active in the unaffected twin, and the maternal deleted X chromosome preferentially active in the affected twin. A review shows that MZ female twins discordant for X-linked diseases are not uncommon. Twinning and X inactivation may be interrelated and could explain the female twins discordant for X-linked traits.
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Affiliation(s)
- N Abbadi
- Laboratoire de Génétique Université de Nancy, France
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Sperber GH, Machin GA, Bamforth FJ. Mirror-image dental fusion and discordance in monozygotic twins. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:41-5. [PMID: 8030668 DOI: 10.1002/ajmg.1320510110] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A pair of monozygotic twins had similar but not identical dental anomalies. One twin had fusion of deciduous mandibular lateral incisor and canine on the left, with normal dentition on the right; the co-twin had right mandibular incisor/canine fusion, with aplasia of the lateral incisor on the left. These findings are discussed in the context of the related phenomena of situs inversus, mirror-imaging in twins, and gradients of severity of anomalies in the four copies of the mandibular developmental dental field.
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Affiliation(s)
- G H Sperber
- Department of Oral Biology, University of Alberta, Edmonton, Canada
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Tihy F, Vogt N, Recan D, Malfoy B, Leturcq F, Coquet M, Serville F, Fontan D, Guillard JM, Kaplan JC. Skewed inactivation of an X chromosome deleted at the dystrophin gene in an asymptomatic mother and her affected daughter. Hum Genet 1994; 93:563-7. [PMID: 8168835 DOI: 10.1007/bf00202824] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A girl with severe Becker muscular dystrophy and apparently normal chromosomes had a heterozygous deletion for exons 51, 52, and 53 of the dystrophin gene. This deletion was transmitted by her mother, who was unaffected. To differentiate the normal and the deleted X chromosomes, fluorescence in situ hybridization (FISH) was applied to metaphase chromosomes, using probes for both exons 51 and 52, which are only 388 and 113 base pairs long, respectively. FISH signals were observed in one or both chromatids of one chromosome, but never on both chromosomes, suggesting the lack of hybridization on the deleted X chromosome. Using 5-bromodeoxyuridine incorporation to differentiate the late (inactive) and the early replicating (active) X chromosomes, 77% of the signals were observed on the active X chromosomes in the mother. This percentage was only 18% in the daughter, suggesting that skewed inactivation of the X chromosomes was responsible for the phenotypic differences.
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Affiliation(s)
- F Tihy
- Université de Montréal, Département de Pathologie, Faculté de Médecine, Canada
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Nicholson LV, Johnson MA, Bushby KM, Gardner-Medwin D, Curtis A, Ginjaar IB, den Dunnen JT, Welch JL, Butler TJ, Bakker E. Integrated study of 100 patients with Xp21 linked muscular dystrophy using clinical, genetic, immunochemical, and histopathological data. Part 1. Trends across the clinical groups. J Med Genet 1993; 30:728-36. [PMID: 8411067 PMCID: PMC1016529 DOI: 10.1136/jmg.30.9.728] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
This multidisciplinary study was undertaken to record the variation in gene and protein expression in a large cohort of patients with well defined clinical phenotypes. The patients, whose ages ranged from 4 years to 66 years, spanned a wide range of disease severity. They represented the first 100 patients who had been examined in Newcastle, had undergone a muscle biopsy, and provided a blood sample for DNA analysis. The study had three aims: to observe any trends in the analyses across the clinical groups, to correlate gene and protein expression in individual patients, and to use the data collected to assess the relative usefulness of different techniques in the diagnosis and prognosis of patients with Duchenne and Becker dystrophy (DMD/BMD). In part 1, we describe the clinical assessment of the patients and the trends that were observed across the cohort. The patients were divided into seven groups. Group 1 had severe DMD (n = 21), group 2 had milder DMD (n = 20), group 3 were intermediate D/BMD patients (n = 9), group 4 had severe BMD (n = 5), and group 5 were more typical BMD patients (n = 31). Some patients were too young to be classified (n = 7) and a group of all the female patients were also classified separately (n = 7). The number of DMD and BMD patients was about equal, in accord with disease prevalence in the north of England, but an unusually high proportion were sporadic cases. Dystrophin labelling (performed with up to three antibodies) on both blots and sections increased gradually across the clinical groups. All histopathological indices, except the proportion of fat in biopsy sections, showed clear trends across the groups.
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Affiliation(s)
- L V Nicholson
- Muscular Dystrophy Group Research Laboratories, Newcastle General Hospital, Newcastle upon Tyne, UK
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36
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Nance WE. 1992 American Society of Human Genetics presidential address: back to the future. Am J Hum Genet 1993; 53:6-15. [PMID: 8317499 PMCID: PMC1682233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Affiliation(s)
- W E Nance
- Department of Human Genetics, Medical College of Virginia, Richmond 23298
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Zneimer SM, Schneider NR, Richards CS. In situ hybridization shows direct evidence of skewed X inactivation in one of monozygotic twin females manifesting Duchenne muscular dystrophy. AMERICAN JOURNAL OF MEDICAL GENETICS 1993; 45:601-5. [PMID: 8456832 DOI: 10.1002/ajmg.1320450517] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A novel combination of conventional and molecular cytogenetic techniques was used to investigate the expression of an X-linked recessive disorder in one of monozygotic (MZ) twin females. These twins carry a deletion, approximately 300 kb in length, in one of their X chromosomes within the dystrophin gene, which is responsible for Duchenne muscular dystrophy (DMD) in one twin [Richards et al.: Am J Hum Genet 46:672-681, 1990]. A unique DNA fragment generated from an exon within this gene deletion was hybridized in situ to both twins' metaphase chromosomes, a probe which would presumably hybridize only to the normal X chromosome and not to the X chromosome carrying the gene deletion. Chromosomes were identified by reverse-banding (R-banding) and by the addition of 5-bromodeoxyuridine (BrdU) in culture to distinguish early and late replicating X chromosomes, corresponding to active and inactive X chromosomes, respectively. Hybridization experiments showed predominant inactivation of the normal X chromosome in the twin with DMD. This is the first report showing direct evidence at the chromosome level of unequal inactivation of cytogenetically normal X chromosomes resulting in the manifestation of an X-linked recessive disorder in one of monozygotic twin females. This study may now facilitate other research of unequal X inactivation and of females manifesting X-linked recessive disorders.
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Affiliation(s)
- S M Zneimer
- University of Texas Southwestern Medical Center, Department of Pathology, Dallas
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Bushby KM, Goodship JA, Nicholson LV, Johnson MA, Haggerty ID, Gardner-Medwin D. Variability in clinical, genetic and protein abnormalities in manifesting carriers of Duchenne and Becker muscular dystrophy. Neuromuscul Disord 1993; 3:57-64. [PMID: 8329890 DOI: 10.1016/0960-8966(93)90042-i] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have analysed the results of clinical assessment, X-inactivation status, deletion screening and dystrophin analysis in eight manifesting carriers of Duchenne and Becker muscular dystrophy (DMD and BMD). Only two had a prior family history of X-linked muscle disease, all had normal karyotypes and none were twins. Presentation varied from 2 to 25 yr and progression varied from a DMD-like severity to a very mild BMD-like course. In one girl the initial symptoms were restricted to learning difficulties. Where methods for assessing X-inactivation were informative, three patients showed an abnormal pattern. However, in one patient, the obligate carrier daughter of a BMD patient who had presented at the age of 2 yr, X-inactivation appeared normal in lymphocytes and muscle. While dystrophin analysis seems to be reliable in identifying manifesting carriers of DMD and BMD, the relationship between X-inactivation status, dystrophin analysis and phenotype is not simple.
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Affiliation(s)
- K M Bushby
- Department of Human Genetics, University of Newcastle upon Tyne, U.K
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39
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Winchester B, Young E, Geddes S, Genet S, Hurst J, Middleton-Price H, Williams N, Webb M, Habel A, Malcolm S. Female twin with Hunter disease due to nonrandom inactivation of the X-chromosome: a consequence of twinning. AMERICAN JOURNAL OF MEDICAL GENETICS 1992; 44:834-8. [PMID: 1481858 DOI: 10.1002/ajmg.1320440625] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We report the occurrence of Hunter disease (mucopolysaccharidosis type II) in a karyotypically normal girl who was one of identical twins. Molecular studies showed nonrandom X-inactivation in both her fibroblasts and lymphocytes, while her normal twin showed equal usage of both X chromosomes. In view of previous reports of 7 pairs of identical female twins in which one had Duchenne muscular dystrophy, it seems that twinning may be strongly associated with nonrandom X-inactivation, and is not specific to the properties of the disease causing gene.
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Affiliation(s)
- B Winchester
- Division of Biochemistry and Metabolism, Institute of Child Health, London, U.K
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40
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Abstract
An important assumption underlying the twin method of comparing MZ and DZ twins is that results from twin samples can be generalized to the larger singleton population. This study uses Item Sheet data on child psychiatric patients to compare twins and singletons on demographic, diagnostic and symptomatic variables. Although little difference was found between the two groups, conduct disorders were significantly over-represented in the twin population. The significance of this finding is discussed. This study lends overall support for the use of the twin method in child psychiatric samples.
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Affiliation(s)
- E Simonoff
- Department of Child and Adolescent Psychiatry, Institute of Psychiatry, London, U.K
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41
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Glass IA, Nicholson LV, Watkiss E, Johnson MA, Roberts RG, Abbs S, Brittain-Jones S, Boddie HG. Investigation of a female manifesting Becker muscular dystrophy. J Med Genet 1992; 29:578-82. [PMID: 1518025 PMCID: PMC1016067 DOI: 10.1136/jmg.29.8.578] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Females manifesting Becker muscular dystrophy (BMD) are even more rarely observed than for the allelic condition Duchenne muscular dystrophy. The male proband has typical BMD with greatly raised CK activity and a myopathic muscle biopsy. His mother experienced walking difficulties from 35 years of age and has a myopathy with marked calf hypertrophy, a raised CK, and a myopathic muscle biopsy. Dystrophin analysis was undertaken on both the proband and his mother. Immunoblotting showed a protein of normal size but of reduced abundance in both. Immunocytochemical analysis in the proband indicated that the majority of the fibres showed weak dystrophin labelling and in his mother both dystrophin positive and dystrophin negative fibres were present. Non-random X inactivation at locus DXS255, was observed in DNA isolated from peripheral lymphocytes of the mother. Neither extended multiplex PCR performed on DNA from the proband nor analysis of lymphocyte derived mRNA showed a structural alteration in the dystrophin gene suggesting that an unusual mutation was responsible for BMD in this family.
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Affiliation(s)
- I A Glass
- West Midlands Regional Genetics Service, Birmingham Maternity Hospital
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42
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Jørgensen AL, Philip J, Raskind WH, Matsushita M, Christensen B, Dreyer V, Motulsky AG. Different patterns of X inactivation in MZ twins discordant for red-green color-vision deficiency. Am J Hum Genet 1992; 51:291-8. [PMID: 1642230 PMCID: PMC1682669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Two female identical twins who were clinically normal were obligatory heterozygotes for X-linked deuteranomaly associated with a green-red fusion gene derived from their deuteranomalous father. On anomaloscopy, one of the twins was phenotypically deuteranomalous while the other had normal color vision. The color vision-defective twin had two sons with normal color vision and one deuteranomalous son. X-inactivation analysis was done with the highly informative probe M27 beta. This probe detects a locus (DXS255) which contains a VNTR and which is somewhat differentially methylated on the active and inactive X chromosomes. In skin cells of the color vision-defective twin, almost all paternal X chromosomes with the abnormal color-vision genes were active, thereby explaining her color-vision defect. In contrast, a different pattern was observed in skin cells from the woman with normal color vision; her maternal X chromosome was mostly active. However, in blood lymphocytes, both twins showed identical patterns with mixtures of inactivated maternal and paternal X chromosomes. Deuteranomaly in one of the twins is explained by extremely skewed X inactivation, as shown in skin cells. Failure to find this skewed pattern in blood cells is explained by the sharing of fetal circulation and exchange of hematopoietic precursor cells between twins. These data give evidence for X inactivation of the color-vision locus and add another MZ twin pair with markedly different X-inactivation patterns for X-linked traits.
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Affiliation(s)
- A L Jørgensen
- Cytogenetic Laboratory, University of Aarhus, Risskov, Denmark
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43
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Wenger SL, Steele MW, Hoffman EP, Barmada MA, Wessel HB. X inactivation and dystrophin studies in a t(X;12) female: evidence for biochemical normalization in Duchenne muscular dystrophy carriers. AMERICAN JOURNAL OF MEDICAL GENETICS 1992; 43:1012-5. [PMID: 1415326 DOI: 10.1002/ajmg.1320430619] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A 4-year-old girl was identified with high creatine kinase (CK) values, and mild muscle weakness in a limb-girdle distribution. Results of dystrophin analysis of the muscle biopsy were consistent with a manifesting heterozygote for Duchenne muscular dystrophy. In peripheral lymphocytes she had a t(X;12) (p21.2;q24.33). Late DNA replication studies demonstrated inactivation of the normal X chromosome in 99.4% of cells. Dystrophin immunofluorescence showed 64% dystrophin-negative muscle fibers. Dystrophin content of muscle by immunoblot was approximately 5% of normal. The discordance between the percent of normal X inactivation and percent of dystrophin-negative cells may be explained by compensatory protection of dystrophin by rare nuclei with the normal X active in multi-nucleated muscle fibers with shared cytoplasm.
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Affiliation(s)
- S L Wenger
- Division of Medical Genetics, Children's Hospital of Pittsburgh, PA 15213-2583
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44
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Clayton-Smith J, Read AP, Donnai D. Monozygotic twinning and Wiedemann-Beckwith syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 1992; 42:633-7. [PMID: 1609846 DOI: 10.1002/ajmg.1320420440] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Monozygotic (MZ) twinning occurs with relatively high frequency in Wiedemann-Beckwith syndrome (WBS). Ten sets of MZ twins with WBS have been reported. Nine of these have been female and in each case the twins were discordant for the WBS phenotype. The tenth set was male. They were concordant for WBS and both had a duplication of chromosome 15 which they shared in common with their phenotypically normal mother. The WBS gene has been assigned to the locus 11p15 and there appear to be several different genetic mechanisms involving this locus which all give rise to WBS. An imprinting effect for the WBS gene has been proposed because of the transmission of the gene preferentially through the maternal line in some large pedigrees. We describe two further sets of female MZ twins with WBS. One pair is concordant and one discordant for the condition. The possible genetic mechanisms involved in the expression of WBS are discussed, with particular reference to twinning, genomic imprinting and X-inactivation which is thought to be associated with the occurrence of MZ twinning in females.
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Affiliation(s)
- J Clayton-Smith
- Department of Medical Genetics, St Mary's Hospital, Manchester, England
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45
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Abstract
In mammals, dosage compensation for X-linked genes between males and females is achieved by the inactivation of one of the X chromosomes in females. The inactivation event occurs early in development in all cells of the female mouse embryo and is stable and heritable in somatic cells. However, in the primordial germ cells, reactivation occurs around the time of meiosis. Owing to random inactivation in somatic cells, all female mice and humans are mosaic for X-linked gene function. Variable mosaicism can result in expression of disease in human females heterozygous for an X-linked gene defect. In the extra-embryonic lineages of female mouse embryos, and in the somatic cells of female marsupials, the paternally inherited X chromosome is preferentially inactivated. The X chromosomes in the egg and sperm must be differentially marked or imprinted, so that they are distinguished by the inactivation mechanism in these tissues. Initiation of inactivation of an entire X chromosome appears to spread from a single X-inactivation centre and may involve the recently discovered gene, XIST, which is expressed only from the inactive X chromosome. The maintenance of inactivation of certain household genes on the inactive X chromosome involves methylation of CpG islands in their 5' regions. Critical CpG sites are methylated at, or very close to, the time of inactivation in development. The mouse and the human X chromosomes carry the same genes but their arrangement is different and there are some genes in the pairing segment and elsewhere on the human X chromosome which can escape inactivation. Regions of homology between the mouse and human X chromosomes allow prediction of the map positions of homologous genes and provide mouse models of genetic disease in the human.
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Affiliation(s)
- M Monk
- MRC Mammalian Development Unit, London, UK
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46
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Malcolm S. Molecular detection of altered X-inactivation patterns in the diagnosis of genetic disease. J Inherit Metab Dis 1992; 15:514-7. [PMID: 1528011 DOI: 10.1007/bf01799609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
It is widely assumed that when a female carrier of a genetic disorder exhibits clinical signs of the disorder it is due to chance non-random X-inactivation in particular tissues. Recently molecular methods have become available for the analysis of X-chromosome inactivation status. These are based either on the methylation patterns of DNA from the active and inactive chromosomes or on the rescue of active X chromosomes in somatic cell hybrids. As a consequence of the molecular studies, it has become obvious that there are some special cases of non-random X-inactivation patterns. These include females carrying X-linked immunodeficiencies and, sometimes, one of a pair of identical female twins.
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Affiliation(s)
- S Malcolm
- Molecular Genetics Unit, Institute of Child Health, London, UK
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Kaplowitz PB, Bodurtha J, Brown J, Spence JE. Monozygotic twins discordant for Ullrich-Turner syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 1991; 41:78-82. [PMID: 1951467 DOI: 10.1002/ajmg.1320410120] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We describe 9-year-old twin girls who were thought to be monozygotic but who differed greatly in physical appearance and growth pattern. One twin had Ullrich-Turner syndrome (UTS), 45,X/46,XX mosaicism in peripheral blood, and only 45,X cells in skin fibroblasts. The phenotypically normal twin also had 45,X/46,XX mosaicism in blood but only 46,XX cells in cultured fibroblasts. Analysis of DNA marker patterns in blood lymphocytes and in skin fibroblasts confirmed monozygosity with a probability of 99.97%. This case is compared with other reported cases of discordance for UTS in twins. It is concluded that essentially all of the differences between the two twins can be explained by loss of an X chromosome early in embryogenesis with complete separation of 45,X and 46,XX cell lineages at the time of the twinning event. The presence of mosaicism in the peripheral blood of both twins is presumably due to anastomoses between the placentae resulting in a mixture of the two cell populations in the hematopoietic tissue.
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Affiliation(s)
- P B Kaplowitz
- Department of Pediatrics, Children's Medical Center-Medical College of Virginia, Virginia Commonwealth University, Richmond
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48
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Abstract
Series of twin pairs selected because one (or both) is ill are prone to biassed ascertainment, and great care has to be taken to avoid this. Such bias is absent if the primary source is a twin registry established at birth. In general, series of twin pairs have no advantage over studies on sibs in assessing the size of genetic contribution to disease. However, individual monozygotic twin pairs who are discordant for single gene or multifactorial conditions offer unique opportunities for investigating postzygotic mutations, for searching for factors that may precipitate disease or influence its course, and for assessing the effect of prophylactic measures.
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Affiliation(s)
- S Bundey
- Clinical Genetics Unit, University of Birmingham, Birmingham Maternity Hospital, Edgbaston, UK
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49
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Abstract
Data are offered on the sex ratio of 81 'new' pairs of monoamniotic (MA) twins. When pooled with data on previously collected MA pairs, the total sample has a sex ratio that is highly significantly lower than that estimated for all monozygotic (MZ) twin pairs. This adds support to the notion that the later an MZ pair is formed, the more likely it is to be female. This in turn supports the hypothesis that anomalous X-inactivation is involved in the formation of some female MZ twin pairs.
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50
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Lupski JR, Garcia CA, Zoghbi HY, Hoffman EP, Fenwick RG. Discordance of muscular dystrophy in monozygotic female twins: evidence supporting asymmetric splitting of the inner cell mass in a manifesting carrier of Duchenne dystrophy. AMERICAN JOURNAL OF MEDICAL GENETICS 1991; 40:354-64. [PMID: 1683155 DOI: 10.1002/ajmg.1320400323] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In 1990, Richards et al. reported dramatically skewed lyonization in a set of female monozygotic twins heterozygous for Duchenne muscular dystrophy (DMD). The skewed inactivation pattern was symmetrical in opposite directions, one twin being affected with DMD, the other one being normal. Here, we report an additional set of female monozygotic twins heterozygous for a mutation at the dystrophin locus. Similarly, one shows a manifesting carrier phenotype while one is normal. However, unlike the previous report, we find a skewed X inactivation pattern only in the affected twin, while the normal twin showed a random X inactivation pattern. Our results lend considerable experimental support for the models of twinning and X inactivation recently outlined by Nance in 1990, in that these twins probably represent asymmetric splitting of the inner cell mass (ICM): The affected twin likely arose when a small proportion of the ICM split off after lyonization had occurred. In this situation, the original ICM could give rise to the normal twin with random lyonization, while the newly split cells would experience catch-up growth and lead to the affected twin. Genetic studies of this family showed that the specific dystrophin gene mutation was an exon duplication that arose sporadically in the paternally derived X chromosome.
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Affiliation(s)
- J R Lupski
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030
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