1
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Fang X, Baggett LM, Caylor RC, Percy AK, Neul JL, Lane JB, Glaze DG, Benke TA, Marsh ED, Motil KJ, Barrish JO, Annese FE, Skinner SA. Parental age effects and Rett syndrome. Am J Med Genet A 2024; 194:160-173. [PMID: 37768187 DOI: 10.1002/ajmg.a.63396] [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: 09/13/2022] [Accepted: 08/18/2023] [Indexed: 09/29/2023]
Abstract
Rett syndrome (RTT) is a progressive neurodevelopmental disorder, and pathogenic Methyl-CpG-binding Protein 2 (MECP2) variants are identified in >95% of individuals with typical RTT. Most of RTT-causing variants in MECP2 are de novo and usually on the paternally inherited X chromosome. While paternal age has been reported to be associated with increased risk of genetic disorders, it is unknown whether parental age contributes to the risk of the development of RTT. Clinical data including parental age, RTT diagnostic status, and clinical severity are collected from 1226 participants with RTT and confirmed MECP2 variants. Statistical analyses are performed using Student t-test, single factor analysis of variance (ANOVA), and multi-factor regression. No significant difference is observed in parental ages of RTT probands compared to that of the general population. A small increase in parental ages is observed in participants with missense variants compared to those with nonsense variants. When we evaluate the association between clinical severity and parental ages by multiple regression analysis, there is no clear association between clinical severity and parental ages. Advanced parental ages do not appear to be a risk factor for RTT, and do not contribute to the clinical severity in individuals with RTT.
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Affiliation(s)
- Xiaolan Fang
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | | | | | - Alan K Percy
- The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jeffrey L Neul
- Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Jane B Lane
- The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | | | - Tim A Benke
- University of Colorado School of Medicine, Children's Hospital Colorado-Aurora, Denver, Colorado, USA
| | - Eric D Marsh
- Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kathleen J Motil
- Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | | | - Fran E Annese
- Greenwood Genetic Center, Greenwood, South Carolina, USA
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2
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Fang X, Butler KM, Abidi F, Gass J, Beisang A, Feyma T, Ryther RC, Standridge S, Heydemann P, Jones M, Haas R, Lieberman DN, Marsh E, Benke TA, Skinner S, Neul JL, Percy AK, Friez MJ, Caylor RC. Analysis of X-inactivation status in a Rett syndrome natural history study cohort. Mol Genet Genomic Med 2022; 10:e1917. [PMID: 35318820 PMCID: PMC9034674 DOI: 10.1002/mgg3.1917] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/15/2022] [Accepted: 02/17/2022] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Rett syndrome (RTT) is a rare neurodevelopmental disorder associated with pathogenic MECP2 variants. Because the MECP2 gene is subject to X-chromosome inactivation (XCI), factors including MECP2 genotypic variation, tissue differences in XCI, and skewing of XCI all likely contribute to the clinical severity of individuals with RTT. METHODS We analyzed the XCI patterns from blood samples of 320 individuals and their mothers. It includes individuals with RTT (n = 287) and other syndromes sharing overlapping phenotypes with RTT (such as CDKL5 Deficiency Disorder [CDD, n = 16]). XCI status in each proband/mother duo and the parental origin of the preferentially inactivated X chromosome were analyzed. RESULTS The average XCI ratio in probands was slightly increased compared to their unaffected mothers (73% vs. 69%, p = .0006). Among the duos with informative XCI data, the majority of individuals with classic RTT had their paternal allele preferentially inactivated (n = 180/220, 82%). In sharp contrast, individuals with CDD had their maternal allele preferentially inactivated (n = 10/12, 83%). Our data indicate a weak positive correlation between XCI skewing ratio and clinical severity scale (CSS) scores in classic RTT patients with maternal allele preferentially inactivated XCI (rs = 0.35, n = 40), but not in those with paternal allele preferentially inactivated XCI (rs = -0.06, n = 180). The most frequent MECP2 pathogenic variants were enriched in individuals with highly/moderately skewed XCI patterns, suggesting an association with higher levels of XCI skewing. CONCLUSION These results extend our understanding of the pathogenesis of RTT and other syndromes with overlapping clinical features by providing insight into the both XCI and the preferential XCI of parental alleles.
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Affiliation(s)
- Xiaolan Fang
- Greenwood Genetic CenterGreenwoodSouth CarolinaUSA
| | | | - Fatima Abidi
- Greenwood Genetic CenterGreenwoodSouth CarolinaUSA
| | - Jennifer Gass
- Florida Cancer Specialists & Research InstituteFort MyersFLUSA,Present address:
Florida Cancer Specialists & Research InstituteFort MyersFloridaUSA
| | - Arthur Beisang
- Gillette Children’s Specialty HealthcareSt. PaulMinnesotaUSA
| | - Timothy Feyma
- Gillette Children’s Specialty HealthcareSt. PaulMinnesotaUSA
| | - Robin C. Ryther
- Department of NeurologyWashington University School of MedicineSt. LouisMissouriUSA
| | - Shannon Standridge
- Division of NeurologyCincinnati Children’s Hospital Medical CenterCincinnatiOhioUSA,Department of Pediatrics, College of MedicineUniversity of CincinnatiCincinnatiOhioUSA
| | | | - Mary Jones
- Oakland Children’s Hospital, UCSFOaklandCaliforniaUSA
| | - Richard Haas
- University of California San DiegoSan DiegoCaliforniaUSA
| | - David N Lieberman
- Department of NeurologyBoston Children’s HospitalBostonMassachusettsUSA
| | - Eric D. Marsh
- Children’s Hospital of Philadelphia and University of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Tim A. Benke
- University of Colorado School of Medicine, Children’s Hospital Colorado‐AuroraDenverColoradoUSA
| | | | - Jeffrey L. Neul
- Vanderbilt Kennedy CenterVanderbilt University Medical CenterNashville TN
| | - Alan K. Percy
- The University of Alabama at BirminghamBirminghamAlabamaUSA
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3
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Collins BE, Neul JL. Rett Syndrome and MECP2 Duplication Syndrome: Disorders of MeCP2 Dosage. Neuropsychiatr Dis Treat 2022; 18:2813-2835. [PMID: 36471747 PMCID: PMC9719276 DOI: 10.2147/ndt.s371483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 11/14/2022] [Indexed: 11/30/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused predominantly by loss-of-function mutations in the gene Methyl-CpG-binding protein 2 (MECP2), which encodes the MeCP2 protein. RTT is a MECP2-related disorder, along with MECP2 duplication syndrome (MDS), caused by gain-of-function duplications of MECP2. Nearly two decades of research have advanced our knowledge of MeCP2 function in health and disease. The following review will discuss MeCP2 protein function and its dysregulation in the MECP2-related disorders RTT and MDS. This will include a discussion of the genetic underpinnings of these disorders, specifically how sporadic X-chromosome mutations arise and manifest in specific populations. We will then review current diagnostic guidelines and clinical manifestations of RTT and MDS. Next, we will delve into MeCP2 biology, describing the dual landscapes of methylated DNA and its reader MeCP2 across the neuronal genome as well as the function of MeCP2 as a transcriptional modulator. Following this, we will outline common MECP2 mutations and genotype-phenotype correlations in both diseases, with particular focus on mutations associated with relatively mild disease in RTT. We will also summarize decades of disease modeling and resulting molecular, synaptic, and behavioral phenotypes associated with RTT and MDS. Finally, we list several therapeutics in the development pipeline for RTT and MDS and available evidence of their safety and efficacy.
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Affiliation(s)
- Bridget E Collins
- Medical Scientist Training Program, Vanderbilt University, Nashville, TN, USA
| | - Jeffrey L Neul
- Vanderbilt Kennedy Center, Departments of Pediatrics, Pharmacology, and Special Education, Vanderbilt University Medical Center and Vanderbilt University, Nashville, TN, USA
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4
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Zhytnik L, Peters M, Tilk K, Simm K, Tõnisson N, Reimand T, Maasalu K, Acharya G, Krjutškov K, Salumets A. From late fatherhood to prenatal screening of monogenic disorders: evidence and ethical concerns. Hum Reprod Update 2021; 27:1056-1085. [PMID: 34329448 DOI: 10.1093/humupd/dmab023] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/27/2021] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND With the help of ART, an advanced parental age is not considered to be a serious obstacle for reproduction anymore. However, significant health risks for future offspring hide behind the success of reproductive medicine for the treatment of reduced fertility associated with late parenthood. Although an advanced maternal age is a well-known risk factor for poor reproductive outcomes, understanding the impact of an advanced paternal age on offspring is yet to be elucidated. De novo monogenic disorders (MDs) are highly associated with late fatherhood. MDs are one of the major sources of paediatric morbidity and mortality, causing significant socioeconomic and psychological burdens to society. Although individually rare, the combined prevalence of these disorders is as high as that of chromosomal aneuploidies, indicating the increasing need for prenatal screening. With the help of advanced reproductive technologies, families with late paternity have the option of non-invasive prenatal testing (NIPT) for multiple MDs (MD-NIPT), which has a sensitivity and specificity of almost 100%. OBJECTIVE AND RATIONALE The main aims of the current review were to examine the effect of late paternity on the origin and nature of MDs, to highlight the role of NIPT for the detection of a variety of paternal age-associated MDs, to describe clinical experiences and to reflect on the ethical concerns surrounding the topic of late paternity and MD-NIPT. SEARCH METHODS An extensive search of peer-reviewed publications (1980-2021) in English from the PubMed and Google Scholar databases was based on key words in different combinations: late paternity, paternal age, spermatogenesis, selfish spermatogonial selection, paternal age effect, de novo mutations (DNMs), MDs, NIPT, ethics of late fatherhood, prenatal testing and paternal rights. OUTCOMES An advanced paternal age provokes the accumulation of DNMs, which arise in continuously dividing germline cells. A subset of DNMs, owing to their effect on the rat sarcoma virus protein-mitogen-activated protein kinase signalling pathway, becomes beneficial for spermatogonia, causing selfish spermatogonial selection and outgrowth, and in some rare cases may lead to spermatocytic seminoma later in life. In the offspring, these selfish DNMs cause paternal age effect (PAE) disorders with a severe and even life-threatening phenotype. The increasing tendency for late paternity and the subsequent high risk of PAE disorders indicate an increased need for a safe and reliable detection procedure, such as MD-NIPT. The MD-NIPT approach has the capacity to provide safe screening for pregnancies at risk of PAE disorders and MDs, which constitute up to 20% of all pregnancies. The primary risks include pregnancies with a paternal age over 40 years, a previous history of an affected pregnancy/child, and/or congenital anomalies detected by routine ultrasonography. The implementation of NIPT-based screening would support the early diagnosis and management needed in cases of affected pregnancy. However, the benefits of MD-NIPT need to be balanced with the ethical challenges associated with the introduction of such an approach into routine clinical practice, namely concerns regarding reproductive autonomy, informed consent, potential disability discrimination, paternal rights and PAE-associated issues, equity and justice in accessing services, and counselling. WIDER IMPLICATIONS Considering the increasing parental age and risks of MDs, combined NIPT for chromosomal aneuploidies and microdeletion syndromes as well as tests for MDs might become a part of routine pregnancy management in the near future. Moreover, the ethical challenges associated with the introduction of MD-NIPT into routine clinical practice need to be carefully evaluated. Furthermore, more focus and attention should be directed towards the ethics of late paternity, paternal rights and paternal genetic guilt associated with pregnancies affected with PAE MDs.
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Affiliation(s)
- Lidiia Zhytnik
- Competence Centre on Health Technologies, Tartu, Estonia
| | - Maire Peters
- Competence Centre on Health Technologies, Tartu, Estonia.,Department of Obstetrics and Gynaecology, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia
| | - Kadi Tilk
- Competence Centre on Health Technologies, Tartu, Estonia
| | - Kadri Simm
- Institute of Philosophy and Semiotics, Faculty of Arts and Humanities, University of Tartu, Tartu, Estonia.,Centre of Ethics, University of Tartu, Tartu, Estonia
| | - Neeme Tõnisson
- Institute of Genomics, University of Tartu, Tartu, Estonia.,Department of Clinical Genetics, United Laboratories, Tartu University Hospital, Tartu, Estonia.,Department of Reproductive Medicine, West Tallinn Central Hospital, Tallinn, Estonia
| | - Tiia Reimand
- Department of Clinical Genetics, United Laboratories, Tartu University Hospital, Tartu, Estonia.,Department of Clinical Genetics, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia
| | - Katre Maasalu
- Clinic of Traumatology and Orthopaedics, Tartu University Hospital, Tartu, Estonia.,Department of Traumatology and Orthopaedics, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia
| | - Ganesh Acharya
- Division of Obstetrics and Gynaecology, Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - Kaarel Krjutškov
- Competence Centre on Health Technologies, Tartu, Estonia.,Department of Obstetrics and Gynaecology, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia
| | - Andres Salumets
- Competence Centre on Health Technologies, Tartu, Estonia.,Department of Obstetrics and Gynaecology, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia.,Institute of Genomics, University of Tartu, Tartu, Estonia.,Division of Obstetrics and Gynaecology, Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
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5
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Pejhan S, Rastegar M. Role of DNA Methyl-CpG-Binding Protein MeCP2 in Rett Syndrome Pathobiology and Mechanism of Disease. Biomolecules 2021; 11:75. [PMID: 33429932 PMCID: PMC7827577 DOI: 10.3390/biom11010075] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/01/2021] [Accepted: 01/03/2021] [Indexed: 12/16/2022] Open
Abstract
Rett Syndrome (RTT) is a severe, rare, and progressive developmental disorder with patients displaying neurological regression and autism spectrum features. The affected individuals are primarily young females, and more than 95% of patients carry de novo mutation(s) in the Methyl-CpG-Binding Protein 2 (MECP2) gene. While the majority of RTT patients have MECP2 mutations (classical RTT), a small fraction of the patients (atypical RTT) may carry genetic mutations in other genes such as the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1. Due to the neurological basis of RTT symptoms, MeCP2 function was originally studied in nerve cells (neurons). However, later research highlighted its importance in other cell types of the brain including glia. In this regard, scientists benefitted from modeling the disease using many different cellular systems and transgenic mice with loss- or gain-of-function mutations. Additionally, limited research in human postmortem brain tissues provided invaluable findings in RTT pathobiology and disease mechanism. MeCP2 expression in the brain is tightly regulated, and its altered expression leads to abnormal brain function, implicating MeCP2 in some cases of autism spectrum disorders. In certain disease conditions, MeCP2 homeostasis control is impaired, the regulation of which in rodents involves a regulatory microRNA (miR132) and brain-derived neurotrophic factor (BDNF). Here, we will provide an overview of recent advances in understanding the underlying mechanism of disease in RTT and the associated genetic mutations in the MECP2 gene along with the pathobiology of the disease, the role of the two most studied protein variants (MeCP2E1 and MeCP2E2 isoforms), and the regulatory mechanisms that control MeCP2 homeostasis network in the brain, including BDNF and miR132.
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Affiliation(s)
| | - Mojgan Rastegar
- Regenerative Medicine Program, and Department of Biochemistry and Medical Genetics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada;
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6
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Stamberger H, Hammer TB, Gardella E, Vlaskamp DRM, Bertelsen B, Mandelstam S, de Lange I, Zhang J, Myers CT, Fenger C, Afawi Z, Almanza Fuerte EP, Andrade DM, Balcik Y, Ben Zeev B, Bennett MF, Berkovic SF, Isidor B, Bouman A, Brilstra E, Busk ØL, Cairns A, Caumes R, Chatron N, Dale RC, de Geus C, Edery P, Gill D, Granild-Jensen JB, Gunderson L, Gunning B, Heimer G, Helle JR, Hildebrand MS, Hollingsworth G, Kharytonov V, Klee EW, Koeleman BPC, Koolen DA, Korff C, Küry S, Lesca G, Lev D, Leventer RJ, Mackay MT, Macke EL, McEntagart M, Mohammad SS, Monin P, Montomoli M, Morava E, Moutton S, Muir AM, Parrini E, Procopis P, Ranza E, Reed L, Reif PS, Rosenow F, Rossi M, Sadleir LG, Sadoway T, Schelhaas HJ, Schneider AL, Shah K, Shalev R, Sisodiya SM, Smol T, Stumpel CTRM, Stuurman K, Symonds JD, Mau-Them FT, Verbeek N, Verhoeven JS, Wallace G, Yosovich K, Zarate YA, Zerem A, Zuberi SM, Guerrini R, Mefford HC, Patel C, Zhang YH, Møller RS, Scheffer IE. NEXMIF encephalopathy: an X-linked disorder with male and female phenotypic patterns. Genet Med 2020; 23:363-373. [PMID: 33144681 DOI: 10.1038/s41436-020-00988-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 09/21/2020] [Accepted: 09/21/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Pathogenic variants in the X-linked gene NEXMIF (previously KIAA2022) are associated with intellectual disability (ID), autism spectrum disorder, and epilepsy. We aimed to delineate the female and male phenotypic spectrum of NEXMIF encephalopathy. METHODS Through an international collaboration, we analyzed the phenotypes and genotypes of 87 patients with NEXMIF encephalopathy. RESULTS Sixty-three females and 24 males (46 new patients) with NEXMIF encephalopathy were studied, with 30 novel variants. Phenotypic features included developmental delay/ID in 86/87 (99%), seizures in 71/86 (83%) and multiple comorbidities. Generalized seizures predominated including myoclonic seizures and absence seizures (both 46/70, 66%), absence with eyelid myoclonia (17/70, 24%), and atonic seizures (30/70, 43%). Males had more severe developmental impairment; females had epilepsy more frequently, and varied from unaffected to severely affected. All NEXMIF pathogenic variants led to a premature stop codon or were deleterious structural variants. Most arose de novo, although X-linked segregation occurred for both sexes. Somatic mosaicism occurred in two males and a family with suspected parental mosaicism. CONCLUSION NEXMIF encephalopathy is an X-linked, generalized developmental and epileptic encephalopathy characterized by myoclonic-atonic epilepsy overlapping with eyelid myoclonia with absence. Some patients have developmental encephalopathy without epilepsy. Males have more severe developmental impairment. NEXMIF encephalopathy arises due to loss-of-function variants.
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Affiliation(s)
- Hannah Stamberger
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia.,Applied and Translational Neurogenomics group, Center for Molecular Neurology, VIB, and Department of Neurology, University Hospital of Antwerp, University of Antwerp, Antwerpen, Belgium
| | - Trine B Hammer
- Department of Epilepsy Genetics, Danish Epilepsy Centre Filadelfia, Dianalund, Denmark.,Clinical Genetic Department, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Elena Gardella
- Department of Epilepsy Genetics, Danish Epilepsy Centre Filadelfia, Dianalund, Denmark.,Institute for Regional Health Services Research, University of Southern Denmark, Odense, Denmark
| | - Danique R M Vlaskamp
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia.,University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, the Netherlands.,University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Birgitte Bertelsen
- Center for Genomic Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Simone Mandelstam
- Royal Children's Hospital, Melbourne, VIC, Australia.,Murdoch Children's Research Institute, Melbourne, VIC, Australia.,Department of Pediatrics, University of Melbourne, Melbourne, VIC, Australia.,Department of Radiology, University of Melbourne, Melbourne, VIC, Australia.,Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia
| | - Iris de Lange
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jing Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Candace T Myers
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - Christina Fenger
- Department of Epilepsy Genetics, Danish Epilepsy Centre Filadelfia, Dianalund, Denmark
| | - Zaid Afawi
- Tel Aviv University Medical School, Tel Aviv, Israel
| | - Edith P Almanza Fuerte
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - Danielle M Andrade
- Division of Neurology, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada
| | - Yunus Balcik
- Epilepsy Center Frankfurt Rhine-Main, Center of Neurology and Neurosurgery, University Hospital Frankfurt, and Center for Personalized Translational Epilepsy Research (CePTER), Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Bruria Ben Zeev
- Edmond and Lily Safra Children's Hospital, Pediatric Neurology Unit, Tel-Hashomer, Israel.,Tel Aviv University, Sackler School of Medicine, Tel Aviv, Israel
| | - Mark F Bennett
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia.,The Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia.,Department of Medical Biology University of Melbourne, Melbourne, VIC, Australia
| | - Samuel F Berkovic
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia
| | | | - Arjan Bouman
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Eva Brilstra
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Øyvind L Busk
- Section for Medical Genetics, Telemark Hospital, Skien, Norway
| | - Anita Cairns
- Department of Neurosciences, Queensland Children's Hospital, Brisbane, QLD, Australia
| | - Roseline Caumes
- Service de Neuropédiatrie, Pôle de Médecine et Spécialités Médicales, CHRU de Lille, Lille, France
| | - Nicolas Chatron
- Lyon University Hospitals, Departments of Genetics, Lyon, France
| | - Russell C Dale
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Christa de Geus
- University Medical Centre Groningen, Department of Genetics, Groningen, The Netherlands
| | - Patrick Edery
- Lyon University Hospitals, Departments of Genetics, Lyon, France.,INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Bron, France
| | - Deepak Gill
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | | | - Lauren Gunderson
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | | | - Gali Heimer
- Edmond and Lily Safra Children's Hospital, Pediatric Neurology Unit, Tel-Hashomer, Israel.,Tel Aviv University, Sackler School of Medicine, Tel Aviv, Israel
| | - Johan R Helle
- Section for Medical Genetics, Telemark Hospital, Skien, Norway
| | - Michael S Hildebrand
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia.,Murdoch Children's Research Institute, Melbourne, VIC, Australia
| | - Georgie Hollingsworth
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia
| | | | - Eric W Klee
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.,Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | - Bobby P C Koeleman
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - David A Koolen
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Christian Korff
- Pediatric Neurology Unit, University Hospitals, Geneva, Switzerland
| | - Sébastien Küry
- Service de génétique médicale, CHU Nantes, Nantes, France
| | - Gaetan Lesca
- Lyon University Hospitals, Departments of Genetics, Lyon, France
| | - Dorit Lev
- Tel Aviv University, Sackler School of Medicine, Tel Aviv, Israel.,Institute of Medical Genetics, Wolfson Medical Center, Holon, Israel
| | - Richard J Leventer
- Royal Children's Hospital, Melbourne, VIC, Australia.,Murdoch Children's Research Institute, Melbourne, VIC, Australia.,Department of Pediatrics, University of Melbourne, Melbourne, VIC, Australia
| | - Mark T Mackay
- Royal Children's Hospital, Melbourne, VIC, Australia.,Murdoch Children's Research Institute, Melbourne, VIC, Australia.,Department of Pediatrics, University of Melbourne, Melbourne, VIC, Australia
| | - Erica L Macke
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | - Meriel McEntagart
- Medical Genetics, St George's University Hospitals NHS FT, Cranmer Tce, London, United Kingdom
| | - Shekeeb S Mohammad
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Pauline Monin
- Lyon University Hospitals, Departments of Genetics, Lyon, France
| | - Martino Montomoli
- Department of Neuroscience, Pharmacology and Child Health, Children's Hospital A. Meyer and University of Florence, Florence, Italy
| | - Eva Morava
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.,Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | - Sebastien Moutton
- CPDPN, Pôle mère enfant, Maison de Santé Protestante Bordeaux Bagatelle, Talence, France.,INSERM UMR1231 GAD, FHU-TRANSLAD, Université de Bourgogne, Dijon, France
| | - Alison M Muir
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - Elena Parrini
- Department of Neuroscience, Pharmacology and Child Health, Children's Hospital A. Meyer and University of Florence, Florence, Italy
| | - Peter Procopis
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Faculty of Medicine and Health, University of Sydney, Sydney, Australia.,Discipline of Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Emmanuelle Ranza
- Medigenome, Swiss Institute of Genomic Medicine, Geneva, Switzerland
| | - Laura Reed
- Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Philipp S Reif
- Epilepsy Center Frankfurt Rhine-Main, Center of Neurology and Neurosurgery, University Hospital Frankfurt, and Center for Personalized Translational Epilepsy Research (CePTER), Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Felix Rosenow
- Epilepsy Center Frankfurt Rhine-Main, Center of Neurology and Neurosurgery, University Hospital Frankfurt, and Center for Personalized Translational Epilepsy Research (CePTER), Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Massimiliano Rossi
- Lyon University Hospitals, Departments of Genetics, Lyon, France.,INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Bron, France
| | - Lynette G Sadleir
- Department of Paediatrics and Child Health, University of Otago Wellington, Wellington, New Zealand
| | - Tara Sadoway
- Division of Neurology, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada
| | | | - Amy L Schneider
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia
| | | | - Ruth Shalev
- Neuropaediatric Unit, Shaare Zedek Medical Centre, Hebrew University School of Medicine, Jerusalem, Israel
| | - Sanjay M Sisodiya
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom and Chalfont Centre for Epilepsy, Bucks, UK
| | - Thomas Smol
- Institut de Génétique Médicale, Hopital Jeanne de Flandre, Lille University Hospital, Lille, France
| | - Connie T R M Stumpel
- Department of Clinical Genetics and GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Kyra Stuurman
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Joseph D Symonds
- Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow, UK.,College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Frederic Tran Mau-Them
- UF Innovation en diagnostic genomique des maladies rares, CHU Dijon Bourgogne, Dijon, France.,INSERM UMR1231 GAD, Dijon, France
| | - Nienke Verbeek
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Judith S Verhoeven
- Academic Center for Epileptology, Kempenhaege, Department of Neurology, Heeze, The Netherlands
| | - Geoffrey Wallace
- Department of Neurosciences, Queensland Children's Hospital, Brisbane, QLD, Australia.,School of Medicine, University of Queensland, Brisbane, QLD, Australia
| | - Keren Yosovich
- Molecular Genetics Lab, Wolfson Medical Center, Holon, Israel
| | - Yuri A Zarate
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Arkansas Children's Hospital, Little Rock, AR, USA
| | - Ayelet Zerem
- Tel Aviv University, Sackler School of Medicine, Tel Aviv, Israel.,White Matter Disease Care, Pediatric Neurology Unit, Dana-Dwak Children's Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Sameer M Zuberi
- Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow, UK.,College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Renzo Guerrini
- Department of Neuroscience, Pharmacology and Child Health, Children's Hospital A. Meyer and University of Florence, Florence, Italy
| | - Heather C Mefford
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - Chirag Patel
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia
| | - Yue-Hua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Rikke S Møller
- Department of Epilepsy Genetics, Danish Epilepsy Centre Filadelfia, Dianalund, Denmark.,Institute for Regional Health Services Research, University of Southern Denmark, Odense, Denmark
| | - Ingrid E Scheffer
- Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, VIC, Australia. .,Royal Children's Hospital, Melbourne, VIC, Australia. .,Murdoch Children's Research Institute, Melbourne, VIC, Australia. .,Department of Pediatrics, University of Melbourne, Melbourne, VIC, Australia. .,Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia.
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7
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Pejhan S, Del Bigio MR, Rastegar M. The MeCP2E1/E2-BDNF- miR132 Homeostasis Regulatory Network Is Region-Dependent in the Human Brain and Is Impaired in Rett Syndrome Patients. Front Cell Dev Biol 2020; 8:763. [PMID: 32974336 PMCID: PMC7471663 DOI: 10.3389/fcell.2020.00763] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/21/2020] [Indexed: 11/13/2022] Open
Abstract
Rett Syndrome (RTT) is a rare and progressive neurodevelopmental disorder that is caused by de novo mutations in the X-linked Methyl CpG binding protein 2 (MECP2) gene and is subjected to X-chromosome inactivation. RTT is commonly associated with neurological regression, autistic features, motor control impairment, seizures, loss of speech and purposeful hand movements, mainly affecting females. Different animal and cellular model systems have tremendously contributed to our current knowledge about MeCP2 and RTT. However, the majority of these findings remain unexamined in the brain of RTT patients. Based on previous studies in rodent brains, the highly conserved neuronal microRNA “miR132” was suggested to be an inhibitor of MeCP2 expression. The neuronal miR132 itself is induced by Brain Derived Neurotrophic Factor (BDNF), a neurotransmitter modulator, which in turn is controlled by MeCP2. This makes the basis of the MECP2-BDNF-miR132 feedback regulatory loop in the brain. Here, we studied the components of this feedback regulatory network in humans, and its possible impairment in the brain of RTT patients. In this regard, we evaluated the transcript and protein levels of MECP2/MeCP2E1 and E2 isoforms, BDNF/BDNF, and miR132 (both 3p and 5p strands) by real time RT-PCR, Western blot, and ELISA in four different regions of the human RTT brains and their age-, post-mortem delay-, and sex-matched controls. The transcript level of the studied elements was significantly compromised in RTT patients, even though the change was not identical in different parts of the brain. Our data indicates that MeCP2E1/E2-BDNF protein levels did not follow their corresponding transcript trends. Correlational studies suggested that the MECP2E1/E2-BDNF-miR132 homeostasis regulation might not be similarly controlled in different parts of the human brain. Despite challenges in evaluating autopsy samples in rare diseases, our findings would help to shed some light on RTT pathobiology, and obscurities caused by limited studies on MeCP2 regulation in the human brain.
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Affiliation(s)
- Shervin Pejhan
- Regenerative Medicine Program, Department of Biochemistry and Medical Genetics, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Marc R Del Bigio
- Department of Pathology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Mojgan Rastegar
- Regenerative Medicine Program, Department of Biochemistry and Medical Genetics, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
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8
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Helle OMB, Pedersen TH, Ousager LB, Thomassen M, Hertz JM. Low frequency of parental mosaicism in de novo COL4A5 mutations in X-linked Alport syndrome. Mol Genet Genomic Med 2020; 8:e1452. [PMID: 32812400 PMCID: PMC7549549 DOI: 10.1002/mgg3.1452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/07/2020] [Accepted: 07/01/2020] [Indexed: 12/19/2022] Open
Abstract
Background Alport syndrome is a progressive hereditary kidney disease clinically presenting with haematuria, proteinuria, and early onset end‐stage renal disease, and often accompanied by hearing loss and ocular abnormalities. The inheritance is X‐linked in the majority of families and caused by sequence variants in the COL4A5 gene encoding the α5‐chain of type‐IV collagen. The proportion of de novo COL4A5 sequence variants in X‐linked Alport syndrome has been reported between 12 and 15% in previous studies. Methods In the present study we have systematically investigated the mosaic status of asymptomatic parents of six patients with X‐linked Alport syndrome using next‐generation sequencing of DNA extracted from different tissues. The deleterious COL4A5 sequence variants in these patients were previously assumed to be de novo, based on Sanger sequencing of the parents. Results A low‐grade (1%) parental mosaicism was detected in only one out of six families (17%). In addition, in one out of six families (17%), we found that the mutational event probably occurred postzygotic. Conclusion These findings highlight the importance of testing for mosaicism in unaffected parents of patients with sequence variants considered to be de novo, as it may have implications for the recurrence risk and thereby for the genetic counseling of the family.
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Affiliation(s)
- Ole Magnus Bjorgaas Helle
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.,Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Torkild Høieggen Pedersen
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.,Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Lilian Bomme Ousager
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.,Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Mads Thomassen
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.,Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Jens Michael Hertz
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.,Department of Clinical Research, University of Southern Denmark, Odense, Denmark
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9
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Ribeiro MC, MacDonald JL. Sex differences in Mecp2-mutant Rett syndrome model mice and the impact of cellular mosaicism in phenotype development. Brain Res 2020; 1729:146644. [PMID: 31904347 DOI: 10.1016/j.brainres.2019.146644] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 12/08/2019] [Accepted: 12/31/2019] [Indexed: 12/29/2022]
Abstract
There is currently no effective treatment for Rett syndrome (RTT), a severe X-linked progressive neurodevelopmental disorder caused by mutations in the transcriptional regulator MECP2. Because MECP2 is subjected to X-inactivation, most affected individuals are female heterozygotes who display cellular mosaicism for normal and mutant MECP2. Males who are hemizygous for mutant MECP2 are more severely affected than heterozygous females and rarely survive. Mecp2 loss-of-function is less severe in mice, however, and male hemizygous null mice not only survive until adulthood, they have been the most commonly studied model system. Although heterozygous female mice better recapitulate human RTT, they have not been as thoroughly characterized. This is likely because of the added experimental challenges that they present, including delayed and more variable phenotypic progression and cellular mosaicism due to X-inactivation. In this review, we compare phenotypes of Mecp2 heterozygous female mice and male hemizygous null mouse models. Further, we discuss the complexities that arise from the many cell-type and tissue-type specific roles of MeCP2, as well as the combination of cell-autonomous and non-cell-autonomous disruptions that result from Mecp2 loss-of-function. This is of particular importance in the context of the female heterozygous brain, composed of a mixture of MeCP2+ and MeCP2- cells, the ratio of which can alter RTT phenotypes in the case of skewed X-inactivation. The goal of this review is to provide a clearer understanding of the pathophysiological differences between the mouse models, which is an essential consideration in the design of future pre-clinical studies.
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Affiliation(s)
- Mayara C Ribeiro
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, NY, United States
| | - Jessica L MacDonald
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, NY, United States.
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10
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Inui T, Iwama K, Miyabayashi T, Sato R, Okubo Y, Endo W, Togashi N, Kakisaka Y, Kikuchi A, Mizuguchi T, Kure S, Matsumoto N, Haginoya K. Two males with sick sinus syndrome in a family with 0.6 kb deletions involving major domains in MECP2. Eur J Med Genet 2019; 63:103769. [PMID: 31536832 DOI: 10.1016/j.ejmg.2019.103769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 09/05/2019] [Accepted: 09/15/2019] [Indexed: 10/26/2022]
Abstract
Mutations in methyl-CpG-binding protein 2 (MECP2) in males can lead to various phenotypes, ranging from neonatal encephalopathy to intellectual disability. In this study, using Nord's method of next-generation sequencing in three siblings, we identified a 0.6 kb deletion involving the transcriptional repression domain (TRD). Two males and one female had intellectual disability and apnea, but none met the criteria of Rett syndrome. Both males had sick sinus syndrome and severe tracheomalacia that resulted in early death. The mother, with skewed X-inactivation, had no symptoms. Therefore, this mutation is pathological for both males and females, resulting in sick sinus syndrome and severe tracheomalacia with strong reproducibility in males. Deletions involving major domains in MECP2 can result in a severe phenotype, and deletion of the TRD domain can cause severe autonomic nervous system dysregulation in males in these cases.
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Affiliation(s)
- Takehiko Inui
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan.
| | - Kazuhiro Iwama
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, Yokohama, Japan; Department of Pediatrics, Graduate School of Medicine, Yokohama City University, Yokohama, Japan
| | - Takuya Miyabayashi
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan
| | - Ryo Sato
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan
| | - Yukimune Okubo
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan
| | - Wakaba Endo
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Noriko Togashi
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan
| | - Yosuke Kakisaka
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Atsuo Kikuchi
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Takeshi Mizuguchi
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, Yokohama, Japan
| | - Shigeo Kure
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, Yokohama, Japan
| | - Kazuhiro Haginoya
- Department of Pediatric Neurology, Miyagi Children's Hospital, 4-3-17 Ochiai, Aoba-ku, Sendai-shi, Miyagi, 989-3126, Japan; Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
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11
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Hettiarachchi D, Neththikumara NF, Pathirana BAPS, Dissanayake VHW. Variant Profile of MECP2 Gene in Sri Lankan Patients with Rett Syndrome. J Autism Dev Disord 2019; 50:118-126. [DOI: 10.1007/s10803-019-04230-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Neul JL, Benke TA, Marsh ED, Skinner SA, Merritt J, Lieberman DN, Standridge S, Feyma T, Heydemann P, Peters S, Ryther R, Jones M, Suter B, Kaufmann WE, Glaze DG, Percy AK. The array of clinical phenotypes of males with mutations in Methyl-CpG binding protein 2. Am J Med Genet B Neuropsychiatr Genet 2019; 180:55-67. [PMID: 30536762 PMCID: PMC6488031 DOI: 10.1002/ajmg.b.32707] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 11/19/2018] [Indexed: 01/09/2023]
Abstract
Mutations in the X-linked gene MECP2 are associated with a severe neurodevelopmental disorder, Rett syndrome (RTT), primarily in girls. It had been suspected that mutations in Methyl-CpG-binding protein 2 (MECP2) led to embryonic lethality in males, however such males have been reported. To enhance understanding of the phenotypic spectrum present in these individuals, we identified 30 males with MECP2 mutations in the RTT Natural History Study databases. A wide phenotypic spectrum was observed, ranging from severe neonatal encephalopathy to cognitive impairment. Two males with a somatic mutation in MECP2 had classic RTT. Of the remaining 28 subjects, 16 had RTT-causing MECP2 mutations, 9 with mutations that are not seen in females with RTT but are likely pathogenic, and 3 with uncertain variants. Two subjects with RTT-causing mutations were previously diagnosed as having atypical RTT; however, careful review of the clinical history determined that an additional 12/28 subjects met criteria for atypical RTT, but with more severe clinical presentation and course, and less distinctive RTT features, than females with RTT, leading to the designation of a new diagnostic entity, male RTT encephalopathy. Increased awareness of the clinical spectrum and widespread comprehensive genomic testing in boys with neurodevelopmental problems will lead to improved identification.
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Affiliation(s)
- Jeffrey L. Neul
- Vanderbilt University Medical Center,University of California, San Diego,Co-corresponding authors: Jeffrey Neul, PMB 40, 230 Appleton Place, Vanderbilt University Medical Center, Nashville, TN 37203-5721, Telephone: 615-322-8242, Facsimile: , Alan Percy, 1720 2 Avenue South, CIRC 320E, University of Alabama at Birmingham, Birmingham, AL 35294-0021, Telephone: 205-996-4927, Facsimile: 205-975-6330,
| | | | - Eric D. Marsh
- Children’s Hospital of Philadelphia, University of Pennsylvania
| | | | - Jonathan Merritt
- Vanderbilt University Medical Center,University of California, San Diego
| | | | | | | | | | | | | | - Mary Jones
- University of California, San Francisco Benioff Children’s Hospital Oakland
| | | | | | - Daniel G. Glaze
- Vanderbilt University Medical Center,University of California, San Diego
| | - Alan K. Percy
- University of Alabama at Birmingham,Co-corresponding authors: Jeffrey Neul, PMB 40, 230 Appleton Place, Vanderbilt University Medical Center, Nashville, TN 37203-5721, Telephone: 615-322-8242, Facsimile: , Alan Percy, 1720 2 Avenue South, CIRC 320E, University of Alabama at Birmingham, Birmingham, AL 35294-0021, Telephone: 205-996-4927, Facsimile: 205-975-6330,
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13
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Clarke AJ, Abdala Sheikh AP. A perspective on "cure" for Rett syndrome. Orphanet J Rare Dis 2018; 13:44. [PMID: 29609636 PMCID: PMC5879810 DOI: 10.1186/s13023-018-0786-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 03/16/2018] [Indexed: 01/08/2023] Open
Abstract
The reversal of the Rett syndrome disease process in the Mecp2 mouse model of Guy et al. (2007) has motivated families and researchers to work on this condition. The reversibility in adult mice suggests that there is potentially much to be gained from rational treatments applied to patients of any age. However, it may be difficult to strike the right balance between enthusiasm on the one hand and realism on the other. One effect of this has been a fragmentation of the "Rett syndrome community" with some groups giving priority to work aimed at a cure while fewer resources are devoted to medical or therapy-based interventions to enhance the quality of life of affected patients or provide support for their families.Several possible therapeutic approaches are under development that, it is claimed and hoped, may lead to a "cure" for patients with Rett syndrome. While all have a rationale, there are potential obstacles to each being both safe and effective. Furthermore, any strategy that succeeded in restoring normal levels of MECP2 gene expression throughout the brain carries potential pitfalls, so that it will be of crucial importance to introduce any clinical trials of such therapies with great care.Expectations of families for a radical, rational treatment should not be inflated beyond a cautious optimism. This is particularly because affected patients with us now may not be able to reap the full benefits of a "cure". Thus, interventions aimed at enhancing the quality of life of affected patients should not be forgone and their importance should not be minimised.
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Affiliation(s)
- Angus John Clarke
- Institute of Medical Genetics, Division of Cancer & Genetics, School of Medicine, Cardiff University, Cardiff, Wales, UK
- Institute of Medical Genetics, University Hospital of Wales, Heath Park, Cardiff, CF14 4XN Wales, UK
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14
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Vogelgesang S, Niebert S, Renner U, Möbius W, Hülsmann S, Manzke T, Niebert M. Analysis of the Serotonergic System in a Mouse Model of Rett Syndrome Reveals Unusual Upregulation of Serotonin Receptor 5b. Front Mol Neurosci 2017; 10:61. [PMID: 28337123 PMCID: PMC5340760 DOI: 10.3389/fnmol.2017.00061] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/23/2017] [Indexed: 12/03/2022] Open
Abstract
Mutations in the transcription factor methyl-CpG-binding-protein 2 (MeCP2) cause a delayed-onset neurodevelopmental disorder known as Rett syndrome (RTT). Although alteration in serotonin levels have been reported in RTT patients, the molecular mechanisms underlying these defects are not well understood. Therefore, we chose to investigate the serotonergic system in hippocampus and brainstem of male Mecp2-/y knock-out mice in the B6.129P2(C)-Mecp2(tm1.1Bird) mouse model of RTT. The serotonergic system in mouse is comprised of 16 genes, whose mRNA expression profile was analyzed by quantitative RT-PCR. Mecp2-/y mice are an established animal model for RTT displaying most of the cognitive and physical impairments of human patients and the selected areas receive significant modulation through serotonin. Using anatomically and functional characterized areas, we found region-specific differential expression between wild type and Mecp2-/y mice at post-natal day 40. In brainstem, we found five genes to be dysregulated, while in hippocampus, two genes were dysregulated. The one gene dysregulated in both brain regions was dopamine decarboxylase, but of special interest is the serotonin receptor 5b (5-ht5b), which showed 75-fold dysregulation in brainstem of Mecp2-/y mice. This dysregulation was not due to upregulation, but due to failure of down-regulation in Mecp2-/y mice during development. Detailed analysis of 5-ht5b revealed a receptor that localizes to endosomes and interacts with Gαi proteins.
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Affiliation(s)
- Steffen Vogelgesang
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the Brain Göttingen, Germany
| | - Sabine Niebert
- Department of Maxillofacial Surgery, University Medical Center Göttingen, Germany
| | - Ute Renner
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the Brain Göttingen, Germany
| | - Wiebke Möbius
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the BrainGöttingen, Germany; Department of Neurogenetics, Max Planck Institute of Experimental MedicineGöttingen, Germany
| | - Swen Hülsmann
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the BrainGöttingen, Germany; Clinic for Anesthesiology, University Medical CenterGöttingen, Germany
| | - Till Manzke
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the Brain Göttingen, Germany
| | - Marcus Niebert
- DFG Research Center and Excellence Cluster Microscopy at the Nanometer Range and Molecular Physiology of the BrainGöttingen, Germany; Institute of Neuro- and Sensory Physiology, University Medical CenterGöttingen, Germany
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15
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Hülsmann S, Mesuret G, Dannenberg J, Arnoldt M, Niebert M. GlyT2-Dependent Preservation of MECP2-Expression in Inhibitory Neurons Improves Early Respiratory Symptoms but Does Not Rescue Survival in a Mouse Model of Rett Syndrome. Front Physiol 2016; 7:385. [PMID: 27672368 PMCID: PMC5018520 DOI: 10.3389/fphys.2016.00385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/22/2016] [Indexed: 11/25/2022] Open
Abstract
Mutations in methyl-CpG-binding protein 2 (MECP2) gene have been shown to manifest in a neurodevelopmental disorder that is called Rett syndrome. A typical problem that occurs during development is a disturbance of breathing. To address the role of inhibitory neurons, we generated a mouse line that restores MECP2 in inhibitory neurons in the brainstem by crossbreeding a mouse line that expresses the Cre-recombinase (Cre) in inhibitory neurons under the control of the glycine transporter 2 (GlyT2, slc6a5) promotor (GlyT2-Cre) with a mouse line that has a floxed-stop mutation of the Mecp2 gene (Mecp2stop/y). Unrestrained whole-body-plethysmography at postnatal day P60 revealed a low respiratory rate and prolonged respiratory pauses in Mecp2stop/y mice. In contrast, GlyT2-Cre positive Mecp2stop/y mice (Cre+; Mecp2stop/y) showed greatly improved respiration and were indistinguishable from wild type littermates. These data support the concept that alterations in inhibitory neurons are important for the development of the respiratory phenotype in Rett syndrome.
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Affiliation(s)
- Swen Hülsmann
- Clinic for Anesthesiology, University Medical CenterGöttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany
| | - Guillaume Mesuret
- Clinic for Anesthesiology, University Medical CenterGöttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany
| | - Julia Dannenberg
- Clinic for Anesthesiology, University Medical Center Göttingen, Germany
| | - Mauricio Arnoldt
- Clinic for Anesthesiology, University Medical Center Göttingen, Germany
| | - Marcus Niebert
- Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany; Institute of Neuro- and Sensory Physiology, University Medical Center GöttingenGöttingen, Germany
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16
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Vacca M, Della Ragione F, Scalabrì F, D'Esposito M. X inactivation and reactivation in X-linked diseases. Semin Cell Dev Biol 2016; 56:78-87. [PMID: 26994527 DOI: 10.1016/j.semcdb.2016.03.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/10/2016] [Accepted: 03/11/2016] [Indexed: 12/22/2022]
Abstract
X chromosome inactivation (XCI) is the phenomenon by which mammals compensate for dosage of X-linked genes in females (XX) versus males (XY). XCI patterns can be random or show extreme skewing, and can modify the mode of inheritance of X-driven phenotypes, which contributes to the variability of human pathologies. Recent findings have shown reversibility of the XCI process, which has opened new avenues in the approaches used for the treatment of X-linked diseases.
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Affiliation(s)
- Marcella Vacca
- Institute of Genetics and Biophysics "A. Buzzati Traverso", CNR, via Pietro Castellino, 111, 80131, Naples, Italy.
| | - Floriana Della Ragione
- Institute of Genetics and Biophysics "A. Buzzati Traverso", CNR, via Pietro Castellino, 111, 80131, Naples, Italy; IRCCS Neuromed, Pozzilli, Isernia, Italy
| | | | - Maurizio D'Esposito
- Institute of Genetics and Biophysics "A. Buzzati Traverso", CNR, via Pietro Castellino, 111, 80131, Naples, Italy; IRCCS Neuromed, Pozzilli, Isernia, Italy
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17
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MECP2 mutations in Czech patients with Rett syndrome and Rett-like phenotypes: novel mutations, genotype–phenotype correlations and validation of high-resolution melting analysis for mutation scanning. J Hum Genet 2016; 61:617-25. [DOI: 10.1038/jhg.2016.19] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/06/2016] [Accepted: 02/15/2016] [Indexed: 02/04/2023]
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18
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Abstract
Rett syndrome (RTT) is a syndromic autism spectrum disorder caused by loss-of-function mutations in MECP2. The methyl CpG binding protein 2 binds methylcytosine and 5-hydroxymethycytosine at CpG sites in promoter regions of target genes, controlling their transcription by recruiting co-repressors and co-activators. Several preclinical studies in mouse models have identified rational molecular targets for drug therapies aimed at correcting the underlying neural dysfunction. These targeted therapies are increasingly translating into human clinical trials. In this review, we present an overview of RTT and describe the current state of preclinical studies in methyl CpG binding protein 2-based mouse models, as well as current clinical trials in individuals with RTT.
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Affiliation(s)
- Lucas Pozzo-Miller
- />Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL USA
| | - Sandipan Pati
- />Department of Neurology, Epilepsy Division, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL USA
| | - Alan K. Percy
- />Department of Pediatrics, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL USA
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Wang H, Pati S, Pozzo-Miller L, Doering LC. Targeted pharmacological treatment of autism spectrum disorders: fragile X and Rett syndromes. Front Cell Neurosci 2015; 9:55. [PMID: 25767435 PMCID: PMC4341567 DOI: 10.3389/fncel.2015.00055] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 02/05/2015] [Indexed: 12/27/2022] Open
Abstract
Autism spectrum disorders (ASDs) are genetically and clinically heterogeneous and lack effective medications to treat their core symptoms. Studies of syndromic ASDs caused by single gene mutations have provided insights into the pathophysiology of autism. Fragile X and Rett syndromes belong to the syndromic ASDs in which preclinical studies have identified rational targets for drug therapies focused on correcting underlying neural dysfunction. These preclinical discoveries are increasingly translating into exciting human clinical trials. Since there are significant molecular and neurobiological overlaps among ASDs, targeted treatments developed for fragile X and Rett syndromes may be helpful for autism of different etiologies. Here, we review the targeted pharmacological treatment of fragile X and Rett syndromes and discuss related issues in both preclinical studies and clinical trials of potential therapies for the diseases.
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Affiliation(s)
- Hansen Wang
- Faculty of Medicine, University of Toronto, 1 King's College Circle Toronto, ON, Canada
| | - Sandipan Pati
- Department of Neurology, Epilepsy Division, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Laurie C Doering
- Faculty of Health Sciences, Department of Pathology and Molecular Medicine, McMaster University Hamilton, ON, Canada
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Lin DS, Chuang TP, Chiang MF, Ho CS, Hsiao CD, Huang YW, Wu TY, Wu JY, Chen YT, Chen TC, Li LH. De novo MECP2 duplication derived from paternal germ line result in dysmorphism and developmental delay. Gene 2014; 533:78-85. [DOI: 10.1016/j.gene.2013.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 09/26/2013] [Accepted: 10/01/2013] [Indexed: 02/02/2023]
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21
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Deng H, Zheng W, Song Z. Genetics, Molecular Biology, and Phenotypes of X-Linked Epilepsy. Mol Neurobiol 2013; 49:1166-80. [DOI: 10.1007/s12035-013-8589-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Accepted: 11/05/2013] [Indexed: 11/25/2022]
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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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Follow-up study of 22 Chinese children with Alexander disease and analysis of parental origin of de novo GFAP mutations. J Hum Genet 2013; 58:183-8. [DOI: 10.1038/jhg.2012.152] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zhang X, Bao X, Zhang J, Zhao Y, Cao G, Pan H, Zhang J, Wei L, Wu X. Molecular characteristics of Chinese patients with Rett syndrome. Eur J Med Genet 2012; 55:677-81. [DOI: 10.1016/j.ejmg.2012.08.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/20/2012] [Indexed: 10/27/2022]
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Gauthier J, Rouleau GA. De novo mutations in neurological and psychiatric disorders: effects, diagnosis and prevention. Genome Med 2012; 4:71. [PMID: 23009675 PMCID: PMC3580441 DOI: 10.1186/gm372] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Neurological and psychiatric disorders account for a considerable proportion of the global disease burden. Although there is a high heritability and a significant genetic component in these disorders, the genetic cause of most cases has yet to be identified. Advances in DNA sequencing allowing the analysis of the whole human genome in a single experiment have led to an acceleration of the discovery of the genetic factors associated with human disease. Recent studies using these platforms have highlighted the important role of de novo mutations in neurological and psychiatric disorders. These findings have opened new avenues into the understanding of genetic disease mechanisms. These discoveries, combined with the increasing ease with which we can sequence the human genome, have important implications for diagnosis, prevention and treatment. Here, we present an overview of the recent discovery of de novo mutations using key examples of neurological and psychiatric disorders. We also discuss the impact of technological developments on diagnosis and prevention.
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Affiliation(s)
- Julie Gauthier
- Center of Excellence in Neuroscience of the Université de Montréal , Quebec, Canada H2L 4MI ; Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Quebec, Canada H2L 4MI
| | - Guy A Rouleau
- Center of Excellence in Neuroscience of the Université de Montréal , Quebec, Canada H2L 4MI ; Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Quebec, Canada H2L 4MI ; Department of Medicine, Université de Montréal, Quebec, Canada H2L 4MI
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Abstract
Rett syndrome is one of the most common causes of complex disability in girls. It is characterized by early neurological regression that severely affects motor, cognitive and communication skills, by autonomic dysfunction and often a seizure disorder. It is a monogenic X-linked dominant neurodevelopmental disorder related to mutation in MECP2, which encodes the methyl-CpG-binding protein MeCP2. There are several mouse models either based on conditional knocking out of the Mecp2 gene or on a truncating mutation. We discuss the clinical aspects with special emphasis on the behavioral phenotype and we review current perspectives in clinical management alongside with perspectives in altering gene expression.
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Affiliation(s)
- E E J Smeets
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
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Paternal age effect mutations and selfish spermatogonial selection: causes and consequences for human disease. Am J Hum Genet 2012; 90:175-200. [PMID: 22325359 DOI: 10.1016/j.ajhg.2011.12.017] [Citation(s) in RCA: 225] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 12/05/2011] [Accepted: 12/26/2011] [Indexed: 12/25/2022] Open
Abstract
Advanced paternal age has been associated with an increased risk for spontaneous congenital disorders and common complex diseases (such as some cancers, schizophrenia, and autism), but the mechanisms that mediate this effect have been poorly understood. A small group of disorders, including Apert syndrome (caused by FGFR2 mutations), achondroplasia, and thanatophoric dysplasia (FGFR3), and Costello syndrome (HRAS), which we collectively term "paternal age effect" (PAE) disorders, provides a good model to study the biological and molecular basis of this phenomenon. Recent evidence from direct quantification of PAE mutations in sperm and testes suggests that the common factor in the paternal age effect lies in the dysregulation of spermatogonial cell behavior, an effect mediated molecularly through the growth factor receptor-RAS signal transduction pathway. The data show that PAE mutations, although arising rarely, are positively selected and expand clonally in normal testes through a process akin to oncogenesis. This clonal expansion, which is likely to take place in the testes of all men, leads to the relative enrichment of mutant sperm over time-explaining the observed paternal age effect associated with these disorders-and in rare cases to the formation of testicular tumors. As regulation of RAS and other mediators of cellular proliferation and survival is important in many different biological contexts, for example during tumorigenesis, organ homeostasis and neurogenesis, the consequences of selfish mutations that hijack this process within the testis are likely to extend far beyond congenital skeletal disorders to include complex diseases, such as neurocognitive disorders and cancer predisposition.
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Linking epigenetics to human disease and Rett syndrome: the emerging novel and challenging concepts in MeCP2 research. Neural Plast 2012; 2012:415825. [PMID: 22474603 PMCID: PMC3306986 DOI: 10.1155/2012/415825] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 11/15/2011] [Indexed: 02/08/2023] Open
Abstract
Epigenetics refer to inheritable changes beyond DNA sequence that control cell identity and morphology. Epigenetics play key roles in development and cell fate commitments and highly impact the etiology of many human diseases. A well-known link between epigenetics and human disease is the X-linked MECP2 gene, mutations in which lead to the neurological disorder, Rett Syndrome. Despite the fact that MeCP2 was discovered about 20 years ago, our current knowledge about its molecular function is not comprehensive. While MeCP2 was originally found to bind methylated DNA and interact with repressor complexes to inhibit and silence its genomic targets, recent studies have challenged this idea. Indeed, depending on its interacting protein partners and target genes, MeCP2 can act either as an activator or as a repressor. Furthermore, it is becoming evident that although Rett Syndrome is a progressive and postnatal neurological disorder, the consequences of MeCP2 deficiencies initiate much earlier and before birth. To comprehend the novel and challenging concepts in MeCP2 research and to design effective therapeutic strategies for Rett Syndrome, a targeted collaborative effort from scientists in multiple research areas to clinicians is required.
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Zhang J, Bao X, Cao G, Jiang S, Zhu X, Lu H, Jia L, Pan H, Fehr S, Davis M, Leonard H, Ravine D, Wu X. What does the nature of the MECP2 mutation tell us about parental origin and recurrence risk in Rett syndrome? Clin Genet 2012; 82:526-33. [PMID: 22182064 DOI: 10.1111/j.1399-0004.2011.01838.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The MECP2 mutations occurring in the severe neurological disorder Rett syndrome are predominantly de novo, with rare familial cases. The aims of this study were to provide a precise estimate of the parental origin of MECP2 mutations using a large Chinese sample and to assess whether parental origin varied by mutation type. The parental origin was paternal in 84/88 [95.5%, (95% confidence interval 88.77-98.75)] of sporadic Chinese cases. However, in a pooled sample including data from the literature the spectrum of mutations occurring on maternally and paternally derived chromosomes differed significantly. The excess we found of 'single base pair gains or losses' on maternally derived MECP2 gene alleles suggests that this mutational category is associated with an elevated risk of gonadal mosaicism, which has implications for genetic counseling.
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Affiliation(s)
- J Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, PR China
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Li W, Pozzo-Miller L. Beyond Widespread Mecp2 Deletions to Model Rett Syndrome: Conditional Spatio-Temporal Knockout, Single-Point Mutations and Transgenic Rescue Mice. ACTA ACUST UNITED AC 2012; 2012:5. [PMID: 23946910 DOI: 10.4172/2165-7890.s1-005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rett syndrome (RTT) is one of the leading causes of intellectual disabilities in women. In addition to a few autistic features, characteristic symptoms that distinguish from classical autism include stereotypic hand movements, motor coordination deficits, breathing abnormalities, seizures and loss of acquired speech as well as purposeful hand use. RTT is highly associated with MECP2, the gene encoding for the transcription factor that binds methylated Cytosine in C-p-G islands in DNA, controlling gene expression and chromatin remodeling. In this review, we will briefly discuss current perspectives on MeCP2 function, and then will describe in detail novel mouse models of RTT based on loss-of-function of Mecp2 and their use for establishing rescue models, wherein we pay close attention to behavioral and morphological phenotypes.
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Affiliation(s)
- Wei Li
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
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31
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Abstract
Mutations in the X-linked gene MECP2 (methyl CpG-binding protein 2) are the primary cause of the neurodevelopmental disorder RTT (Rett syndrome), and are also implicated in other neurological conditions. The expression product of this gene, MeCP2, is a widely expressed nuclear protein, especially abundant in mature neurons of the CNS (central nervous system). The major recognized consequences of MECP2 mutation occur in the CNS, but there is growing awareness of peripheral effects contributing to the full RTT phenotype. MeCP2 is classically considered to act as a DNA methylation-dependent transcriptional repressor, but may have additional roles in regulating gene expression and chromatin structure. Knocking out Mecp2 function in mice recapitulates many of the overt neurological features seen in RTT patients, and the characteristic postnatally delayed onset of symptoms is accompanied by aberrant neuronal morphology and deficits in synaptic physiology. Evidence that reactivation of endogenous Mecp2 in mutant mice, even at adult stages, can reverse aspects of RTT-like pathology and result in apparently functionally mature neurons has provided renewed hope for patients, but has also provoked discussion about traditional boundaries between neurodevelopmental disorders and those involving dysfunction at later stages. In the present paper we review the neurobiology of MeCP2 and consider the various genetic (including gene therapy), pharmacological and environmental interventions that have been, and could be, developed to attempt phenotypic rescue in RTT. Such approaches are already providing valuable insights into the potential tractability of RTT and related conditions, and are useful pointers for the development of future therapeutic strategies.
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32
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Ravn K, Roende G, Duno M, Fuglsang K, Eiklid KL, Tümer Z, Nielsen JB, Skjeldal OH. Two new Rett syndrome families and review of the literature: expanding the knowledge of MECP2 frameshift mutations. Orphanet J Rare Dis 2011; 6:58. [PMID: 21878110 PMCID: PMC3173288 DOI: 10.1186/1750-1172-6-58] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 08/30/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder, which is usually caused by de novo mutations in the MECP2 gene. More than 70% of the disease causing MECP2 mutations are eight recurrent C to T transitions, which almost exclusively arise on the paternally derived X chromosome. About 10% of the RTT cases have a C-terminal frameshift deletion in MECP2. Only few RTT families with a segregating MECP2 mutation, which affects female carriers with a phenotype of mental retardation or RTT, have been reported in the literature. In this study we describe two new RTT families with three and four individuals, respectively, and review the literature comparing the type of mutations and phenotypes observed in RTT families with those observed in sporadic cases. Based on these observations we also investigated origin of mutation segregation to further improve genetic counselling. METHODS MECP2 mutations were identified by direct sequencing. XCI studies were performed using the X-linked androgen receptor (AR) locus. The parental origin of de novo MECP2 frameshift mutations was investigated using intronic SNPs. RESULTS In both families a C-terminal frameshift mutation segregates. Clinical features of the mutation carriers vary from classical RTT to mild mental retardation. XCI profiles of the female carriers correlate to their respective geno-/phenotypes. The majority of the de novo frameshift mutations occur on the paternally derived X chromosome (7/9 cases), without a paternal age effect. CONCLUSIONS The present study suggests a correlation between the intrafamilial phenotypic differences observed in RTT families and their respective XCI pattern in blood, in contrast to sporadic RTT cases where a similar correlation has not been demonstrated. Furthermore, we found de novo MECP2 frameshift mutations frequently to be of paternal origin, although not with the same high paternal occurrence as in sporadic cases with C to T transitions. This suggests further investigations of more families. This study emphasizes the need for thorough genetic counselling of families with a newly diagnosed RTT patient.
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Affiliation(s)
- Kirstine Ravn
- Center for Rett syndrome, Kennedy Center, Glostrup, Denmark.
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Mittal K, Kabra M, Juyal R, BK T. De novo deletion in MECP2 in a monozygotic twin pair: a case report. BMC MEDICAL GENETICS 2011; 12:113. [PMID: 21871116 PMCID: PMC3176152 DOI: 10.1186/1471-2350-12-113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 08/27/2011] [Indexed: 11/10/2022]
Abstract
BACKGROUND Rett syndrome (RTT) is a severe, progressive, neurodevelopmental disorder predominantly observed in females that leads to intellectual disability. Mutations and gross rearrangements in MECP2 account for a large proportion of cases with RTT. A limited number of twin pairs with RTT have also been reported in literature. CASE PRESENTATION We investigated 13 year old, monozygotic twin females with RTT and some noticeable differences in development using a combinatorial approach of sequencing and Taqman assay. Monozygosity status of the twins was confirmed by informative microsatellite markers. CONCLUSIONS The twins shared a de novo deletion in exon 3 in the MBD domain of MECP2. To the best of our knowledge, this is only the second report of genetic analysis of a monozygotic twin pair.
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Affiliation(s)
- Kirti Mittal
- Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi 110021, India
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34
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Calfa G, Percy AK, Pozzo-Miller L. Experimental models of Rett syndrome based on Mecp2 dysfunction. Exp Biol Med (Maywood) 2011; 236:3-19. [PMID: 21239731 DOI: 10.1258/ebm.2010.010261] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder predominantly occurring in females with an incidence of 1:10,000 births and caused by sporadic mutations in the MECP2 gene, which encodes methyl-CpG-binding protein-2, an epigenetic transcription factor that binds methylated DNA. The clinical hallmarks include a period of apparently normal early development followed by a plateau and then subsequent frank regression. Impaired visual and aural contact often lead to an initial diagnosis of autism. The characterization of experimental models based on the loss-of-function of the mouse Mecp2 gene revealed that subtle changes in the morphology and function of brain cells and synapses have profound consequences on network activities that underlie critical brain functions. Furthermore, these experimental models have been used for successful reversals of RTT-like symptoms by genetic, pharmacological and environmental manipulations, raising hope for novel therapeutic strategies to improve the quality of life of RTT individuals.
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Affiliation(s)
- Gaston Calfa
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
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35
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Zhu X, Li M, Pan H, Bao X, Zhang J, Wu X. Analysis of the parental origin of de novo MECP2 mutations and X chromosome inactivation in 24 sporadic patients with Rett syndrome in China. J Child Neurol 2010; 25:842-8. [PMID: 20207612 DOI: 10.1177/0883073809350722] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Rett syndrome is an X-linked neurodevelopmental disorder that predominantly affects females. It is caused by mutations in methyl-CpG-binding protein 2 gene. Due to the sex-limited expression, it has been suggested that de novo X-linked mutations may exclusively occur in male germ cells and thus only females are affected. In this study, the authors have analyzed the parental origin of mutations and the X-chromosome inactivation status in 24 sporadic patients with identified methyl-CpG-binding protein 2 gene mutations. The results showed that 22 of 24 patients have a paternal origin. Only 2 patients have a maternal origin. Except for 2 cases which were homozygotic at the androgen receptor gene locus, of the remaining 22 cases, 16 cases have a random X-chromosome inactivation pattern; the other 6 cases have a skewed X-chromosome inactivation and they favor expression of the wild allele. The relationship between X-chromosome inactivation and phenotype may need more cases to explore.
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Affiliation(s)
- Xingwang Zhu
- Department of Pediatrics, Peking University First Hospital, Beijing, People's Republic of China
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36
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Reversibility of functional deficits in experimental models of Rett syndrome. Biochem Soc Trans 2010; 38:498-506. [DOI: 10.1042/bst0380498] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mutations in the X-linked MECP2 gene are the primary cause of the severe autism spectrum disorder RTT (Rett syndrome). Deletion of Mecp2 in mice recapitulates many of the overt neurological features seen in humans, and the delayed onset of symptoms is accompanied by deficits in neuronal morphology and synaptic physiology. Recent evidence suggests that reactivation of endogenous Mecp2 in young and adult mice can reverse aspects of RTT-like pathology. In the current perspective, we discuss these findings as well as other genetic, pharmacological and environmental interventions that attempt phenotypic rescue in RTT. We believe these studies provide valuable insights into the tractability of RTT and related conditions and are useful pointers for the development of future therapeutic strategies.
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37
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Abstract
Methyl CpG binding protein-2 (MeCP2) is an essential epigenetic regulator in human brain development. Rett syndrome, the primary disorder caused by mutations in the X-linked MECP2 gene, is characterized by a period of cognitive decline and development of hand stereotypies and seizures following an apparently normal early infancy. In addition, MECP2 mutations and duplications are observed in a spectrum of neurodevelopmental disorders, including severe neonatal encephalopathy, X-linked mental retardation, and autism, implicating MeCP2 as an essential regulator of postnatal brain development. In this review, we compare the mutation types and inheritance patterns of the human disorders associated with MECP2. In addition, we summarize the current understanding of MeCP2 as a central epigenetic regulator of activity-dependent synaptic maturation. As MeCP2 occupies a central role in the pathogenesis of multiple neurodevelopmental disorders, continued investigation into MeCP2 function and regulatory pathways may show promise for developing broad-spectrum therapies.
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Affiliation(s)
- Michael L. Gonzales
- School of Medicine, Medical Microbiology and Immunology, University of California, Davis, One Shields Avenue, Davis, CA 95616 USA
| | - Janine M. LaSalle
- School of Medicine, Medical Microbiology and Immunology, University of California, Davis, One Shields Avenue, Davis, CA 95616 USA
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38
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Seeman MV. Mechanisms of sex difference: a historical perspective. J Womens Health (Larchmt) 2009; 18:861-6. [PMID: 19514828 DOI: 10.1089/jwh.2008.1208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVE The history of the discovery of mechanisms contributing to sex difference helps to better appreciate gender factors in a variety of disease states. The objective of this article is to illustrate four mechanisms of sex differences in disease incidence: X-linkage (including inactivation, escape from inactivating, skewed inactivation), sex-specific exposure to disease-producing pathogens, fetal microchimerism, and iron depletion. METHODS This is a historic review. RESULTS An emphasis on sex difference led to the uncovering of four different mechanisms by which illness rates differ in men and women. CONCLUSIONS Research into many disease states can benefit from a focus on potential mechanisms that yield sex differences in illness susceptibility, progression, and outcome.
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Affiliation(s)
- Mary V Seeman
- Centre for Addiction and Mental Health, Psychiatry, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
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De Sario A. Clinical and molecular overview of inherited disorders resulting from epigenomic dysregulation. Eur J Med Genet 2009; 52:363-72. [PMID: 19632366 DOI: 10.1016/j.ejmg.2009.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Accepted: 07/21/2009] [Indexed: 01/23/2023]
Abstract
Epigenetics is the study of heritable changes in gene expression that occur without a change in the DNA sequence. Most constitutional defects in genes encoding components of the machinery that regulates the epigenome lead to embryonic death. Hypomorphic mutations may be compatible with life, but lead to severe developmental disorders. Their study is of great importance to our understanding of epigenetics and may clarify the interplay between different epigenetic mechanisms. This review will briefly introduce DNA methylation, post-translational histone modifications, and non-coding small RNA transcription, which are the best known epigenetic mechanisms. Then it will describe five human disorders (RETT, ATRX, ICF, Coffin-Lowry, and Rubinstein-Taybi) resulting from mutations in genes responsible for DNA methylation and in genes involved in chromatin remodeling. Finally, it will discuss how research in medical genetics can elucidate fundamental epigenetic processes.
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Affiliation(s)
- Albertina De Sario
- Institut de Génétique Humaine, CNRS UPR 1142, 141 rue de la Cardonille, 34396 Montpellier, France.
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Matarazzo MR, De Bonis ML, Vacca M, Della Ragione F, D'Esposito M. Lessons from two human chromatin diseases, ICF syndrome and Rett syndrome. Int J Biochem Cell Biol 2008; 41:117-26. [PMID: 18786650 DOI: 10.1016/j.biocel.2008.07.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 07/25/2008] [Accepted: 07/28/2008] [Indexed: 11/17/2022]
Abstract
Spatial organisation of DNA into chromatin profoundly affects gene expression and function. The recent association of genes controlling chromatin structure to human pathologies resulted in a better comprehension of the interplay between regulation and function. Among many chromatin disorders we will discuss Rett and immunodeficiency, centromeric instability and facial anomalies (ICF) syndromes. Both diseases are caused by defects related to DNA methylation machinery, with Rett syndrome affecting the transduction of the repressive signal from the methyl CpG binding protein prototype, MeCP2, and ICF syndrome affecting the genetic control of DNA methylation, by the DNA methyltransferase DNMT3B. Rather than listing survey data, our aim is to highlight how a deeper comprehension of gene regulatory web may arise from studies of such pathologies. We also maintain that fundamental studies may offer chances for a therapeutic approach focused on these syndromes, which, in turn, may become paradigmatic for this increasing class of diseases.
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Affiliation(s)
- M R Matarazzo
- Institute of Genetics and Biophysics, A.Buzzati Traverso, Consiglio Nazionale delle Ricerche, via P.Castellino 111, 80131 Naples, Italy
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41
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Schüle B, Armstrong DD, Vogel H, Oviedo A, Francke U. Severe congenital encephalopathy caused by MECP2 null mutations in males: central hypoxia and reduced neuronal dendritic structure. Clin Genet 2008; 74:116-26. [PMID: 18477000 DOI: 10.1111/j.1399-0004.2008.01005.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Non-mosaic males with a 46,XY karyotype and a MECP2 null mutation display a phenotype of severe neonatal-onset encephalopathy that is distinctly different from Rett syndrome (RTT). To increase awareness of this rare disorder, we are reporting novel findings in a sporadic case, compare them to 16 previously reported cases and establish salient criteria for clinical diagnosis. The proband suffered from general hypotonia and hypoxia caused by hypoventilation and irregular breathing. He developed abnormal movements, seizures and electroencephalogram abnormalities. He failed to thrive and to reach any motor milestones and died at 15 months from central respiratory failure without a diagnosis. In a muscle biopsy, type II fibers were reduced in diameter, indicating central hypoxia. At autopsy, the brain was small with disproportionate reduction of the frontal and temporal lobes. Synaptophysin staining of synaptic vesicles was greatly reduced in cerebellar and spinal cord sections. Analysis of Golgi-stained pyramidal neurons from cortical layers III and V of the frontal and temporal lobes revealed drastically diminished dendritic trees. Post-mortem MECP2 mutation analysis on DNA and RNA from fibroblasts revealed a novel de novo 9-nucleotide deletion including the intron 3/exon 4 splice junction. The two nucleotides flanking the deletion form a new splice site, and the aberrantly spliced transcript lacks seven nucleotides (r.378_384delTCCCCAG), causing a frameshift and premature termination codon (p.I126fsX11). Males with congenital encephalopathy, not females with RTT, represent the true human counterpart for the commonly studied Mecp2-/y mouse model and provide unique insight into the mechanisms of MeCP2 deficiency.
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Affiliation(s)
- B Schüle
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
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42
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Xinhua Bao, Shengling Jiang, Fuying Song, Hong Pan, Meirong Li, Wu XR. X chromosome inactivation in Rett Syndrome and its correlations with MECP2 mutations and phenotype. J Child Neurol 2008; 23:22-5. [PMID: 18184939 DOI: 10.1177/0883073807307077] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rett syndrome (RTT) is an X-linked dominant neurodevelopment disorder, which is mainly caused by gene mutation of methyl-CpG-binding protein 2 (MECP2). The correlations between genotype, X chromosome inactivation (XCI), and phenotype have been studied, but the results are conflicting. In the present study, XCI patterns in patients and their mothers, parental origin of skewed X chromosome in patients, and the correlations between XCI, genotype, and phenotype were analyzed in 52 cases of RTT with MECP2 mutations, 50 RTT mothers, and 48 normal female controls. The results showed XCI and genotype had limitations in explaining all the phenotypic manifestations of RTT. Other genomic factors have to be considered to explain the phenotypic differences.
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Affiliation(s)
- Xinhua Bao
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
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Abstract
Autism, at its most extreme, is a severe neurodevelopmental disorder, and recent studies have indicated that autism spectrum disorders are considerably more common than previously supposed. However, although one of the most heritable neuropsychiatric syndromes, autism has so far eluded attempts to discover its genetic origins in the majority of cases. Several whole-genome scans for autism-susceptibility loci have identified specific chromosomal regions, but the results have been inconclusive and fine mapping and association studies have failed to identify the underlying genes. Recent advances in knowledge from the Human Genome and HapMap Projects, and progress in technology and bioinformatic resources, have aided study design and made data generation more efficient and cost-effective. Broadening horizons about the landscape of structural genetic variation and the field of epigenetics are indicating new possible mechanisms underlying autism aetiology, while endophenotypes are being used in an attempt to break down the complexity of the syndrome and refine genetic data. Although the genetic variants underlying idiopathic autism have proven elusive so far, the future for this field looks promising.
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Affiliation(s)
- Nuala H Sykes
- Wellcome Trust Centre for Human Genetics, University of Oxford, UK
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Abstract
Rett syndrome (RS) is an X-linked neurodevelopmental disorder and the second most common cause of genetic mental retardation in females. Different mutations in MECP2 are found in up to 95% of typical cases of RS. This mainly neuronal expressed gene functions as a major transcription repressor. Extensive studies on girls who have RS and mouse models are aimed at finding main gene targets for MeCP2 protein and defining neuropathologic changes caused by its defects. Studies comparing autistic features in RS with idiopathic autism and mentally retarded patients are presented. Decreased dendritic arborization is common to RS and autism, leading to further research on similarities in pathogenesis, including MeCP2 protein levels in autistic brains and MeCP2 effects on genes connected to autism, like DLX5 and genes on 15q11-13 region. This area also is involved in Angelman syndrome, which has many similarities to RS. Despite these connections, MECP2 mutations in nonspecific autistic and mentally retarded populations are rare.
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Affiliation(s)
- Bruria Ben Zeev Ghidoni
- Pediatric Neurology Unit, Safra Pediatric Hospital, Sheba Medical Center, Ramat-Gan, Israel.
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Abstract
In this review, we give a clinical overview of Rett syndrome (RTT), and provide a framework for clinical and molecular approaches to the diagnosis of this severe neurodevelopmental disorder. We also discuss issues that need to be considered in the management of RTT patients, and raise some of the challenges associated with genetic counselling.
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Affiliation(s)
- Sarah L Williamson
- Western Sydney Genetics Program, the Royal Alexandra Hospital for Children, Sydney, Australia
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Evans JC, Archer HL, Whatley SD, Clarke A. Germline mosaicism for a MECP2 mutation in a man with two Rett daughters. Clin Genet 2006; 70:336-8. [PMID: 16965328 DOI: 10.1111/j.1399-0004.2006.00691.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rett syndrome is a severe neurodevelopmental disorder that is caused by mutations in the X-linked gene, methyl-CpG binding protein 2 (MECP2). The majority of cases are sporadic, but rarely germline mosaicism can lead to familial cases. Here, we report the first case where germline mosaicism for a MECP2 mutation has been shown in a man. He has two affected daughters who are half sisters, and both have the c.808delC mutation. We show that this mutation is present at a low level in DNA extracted from the patient's semen. This case has implications for genetic counseling, and pre-natal testing should be offered for the partners of men who have a daughter with Rett syndrome.
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Affiliation(s)
- J C Evans
- Department of Medical Genetics, Cardiff University, Heath Park, Cardiff, UK
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Archer H, Evans J, Leonard H, Colvin L, Ravine D, Christodoulou J, Williamson S, Charman T, Bailey MES, Sampson J, de Klerk N, Clarke A. Correlation between clinical severity in patients with Rett syndrome with a p.R168X or p.T158M MECP2 mutation, and the direction and degree of skewing of X-chromosome inactivation. J Med Genet 2006; 44:148-52. [PMID: 16905679 PMCID: PMC2598067 DOI: 10.1136/jmg.2006.045260] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder that is usually associated with mutations in the MECP2 gene. The most common mutations in the gene are p.R168X and p.T158M. The influence of X-chromosome inactivation (XCI) on clinical severity in patients with RTT with these mutations was investigated, taking into account the extent and direction of skewing. METHODS Female patients and their parents were recruited from the UK and Australia. Clinical severity was measured by the Pineda Severity and Kerr profile scores. The degree of XCI and its direction relative to the X chromosome parent of origin were measured in DNA prepared from peripheral blood leucocytes, and allele-specific polymerase chain reaction was used to determine the parental origin of mutation. Combining these, the percentage of cells expected to express the mutant allele was calculated. RESULTS Linear regression analysis was undertaken for fully informative cases with p.R168X (n = 23) and p.T158M (n = 20) mutations. A statistically significant increase in clinical severity with increase in the proportion of active mutated allele was shown for both the p.R168X and p.T158M mutations. CONCLUSIONS XCI may vary in neurological and haematological tissues. However, these data are the first to show a relationship between the degree and direction of XCI in leucocytes and clinical severity in RTT, although the clinical utility of this in giving a prognosis for individual patients is unclear.
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Affiliation(s)
- Hayley Archer
- Institute of Medical Genetics, Cardiff University, University Hospital of Wales, Cardiff, UK
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Knudsen GPS, Neilson TCS, Pedersen J, Kerr A, Schwartz M, Hulten M, Bailey MES, Orstavik KH. Increased skewing of X chromosome inactivation in Rett syndrome patients and their mothers. Eur J Hum Genet 2006; 14:1189-94. [PMID: 16823396 DOI: 10.1038/sj.ejhg.5201682] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Rett syndrome is a largely sporadic, X-linked neurological disorder with a characteristic phenotype, but which exhibits substantial phenotypic variability. This variability has been partly attributed to an effect of X chromosome inactivation (XCI). There have been conflicting reports regarding incidence of skewed X inactivation in Rett syndrome. In rare familial cases of Rett syndrome, favourably skewed X inactivation has been found in phenotypically normal carrier mothers. We have investigated the X inactivation pattern in DNA from blood and buccal cells of sporadic Rett patients (n=96) and their mothers (n=84). The mean degree of skewing in blood was higher in patients (70.7%) than controls (64.9%). Unexpectedly, the mothers of these patients also had a higher mean degree of skewing in blood (70.8%) than controls. In accordance with these findings, the frequency of skewed (XCI > or =80%) X inactivation in blood was also higher in both patients (25%) and mothers (30%) than in controls (11%). To test whether the Rett patients with skewed X inactivation were daughters of skewed mothers, 49 mother-daughter pairs were analysed. Of 14 patients with skewed X inactivation, only three had a mother with skewed X inactivation. Among patients, mildly affected cases were shown to be more skewed than more severely affected cases, and there was a trend towards preferential inactivation of the paternally inherited X chromosome in skewed cases. These findings, particularly the greater degree of X inactivation skewing in Rett syndrome patients, are of potential significance in the analysis of genotype-phenotype correlations in Rett syndrome.
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Affiliation(s)
- Gun Peggy S Knudsen
- Faculty Division Rikshospitalet, Department of Medical Genetics, University of Oslo, Oslo, Norway.
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Bienvenu T, Chelly J. Molecular genetics of Rett syndrome: when DNA methylation goes unrecognized. Nat Rev Genet 2006; 7:415-26. [PMID: 16708070 DOI: 10.1038/nrg1878] [Citation(s) in RCA: 206] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The discovery that Rett syndrome is caused by mutations that affect the methyl-CpG-binding protein MeCP2 provided a major breakthrough in understanding this severe neurodevelopmental disorder. Animal models and expression studies have contributed to defining the role of MeCP2 in development, highlighting its contribution to postnatal neuronal morphogenesis and function. Furthermore, in vitro assays and microrray studies have delineated the potential molecular mechanisms of MeCP2 function, and have indicated a role in the transcriptional silencing of specific target genes. As well as unravelling the mechanisms that underlie Rett syndrome, these studies provide more general insights into how DNA-methylation patterns are recognized and translated into biological outcomes.
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Affiliation(s)
- Thierry Bienvenu
- Institut Cochin, Départment de Génétique et Developpement, Paris, F-75014 France
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Weaving LS, Ellaway CJ, Gécz J, Christodoulou J. Rett syndrome: clinical review and genetic update. J Med Genet 2006; 42:1-7. [PMID: 15635068 PMCID: PMC1735910 DOI: 10.1136/jmg.2004.027730] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Rett syndrome (RS) is a severe neurodevelopmental disorder that contributes significantly to severe intellectual disability in females worldwide. It is caused by mutations in MECP2 in the majority of cases, but a proportion of atypical cases may result from mutations in CDKL5, particularly the early onset seizure variant. The relationship between MECP2 and CDKL5, and whether they cause RS through the same or different mechanisms is unknown, but is worthy of investigation. Mutations in MECP2 appear to give a growth disadvantage to both neuronal and lymphoblast cells, often resulting in skewing of X inactivation that may contribute to the large degree of phenotypic variation. MeCP2 was originally thought to be a global transcriptional repressor, but recent evidence suggests that it may have a role in regulating neuronal activity dependent expression of specific genes such as Hairy2a in Xenopus and Bdnf in mouse and rat.
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Affiliation(s)
- L S Weaving
- Program in Developmental Biology, the Hospital for Sick Children, Toronto, Canada
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