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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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2
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MECP2-related conditions in males: A systematic literature review and 8 additional cases. Eur J Paediatr Neurol 2021; 34:7-13. [PMID: 34271245 DOI: 10.1016/j.ejpn.2021.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 02/25/2021] [Accepted: 05/25/2021] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To present a cohort of 8 males and perform a systematic review of all published cases with a single copy of MECP2 carrying a pathogenic variant. METHODS We reviewed medical records of males with a single copy of MECP2 carrying a pathogenic variant. We searched in Medline (Pubmed) and Embase to collect all articles which included well-characterized males with a single copy of MECP2 carrying a pathogenic or likely pathogenic variant in MECP2 (1999-2020). RESULTS The literature search yielded a total of 3,185 publications, of which 58 were included in our systematic review. We were able to collect information on 27 published patients with severe neonatal encephalopathy, 47 individuals with isolated or familial mental retardation X-linked 13 (XLMR13), as well as 24 individuals with isolated or familial Pyramidal signs, parkinsonism, and macroorchidism (PPM-X). In our cohort, we met eight individuals aged 4 to 19-year-old at the last evaluation. Three MECP2-associated phenotypes were seen in male carriers of a single copy of the gene: severe neonatal encephalopathy (n = 5); X-linked intellectual deficiency 13 (n = 2); and pyramidal signs, parkinsonism, and macroorchidism (PPM-X) (n = 1). Two novel de novo variants [p.(Gly252Argfs∗7) and p.(Tyr132Cys)] were detected. CONCLUSION In males, the MECP2 pathogenic variants can be associated with different phenotypes, including neonatal severe encephalopathy, intellectual deficiency, or late-onset parkinsonism and spasticity. The typical RS phenotype is not expected in males, except in those with Klinefelter syndrome or somatic mosaicism for MECP2.
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De Luca C, Race V, Keldermans L, Bauters M, Van Esch H. Challenges in molecular diagnosis of X-linked Intellectual disability. Br Med Bull 2020; 133:36-48. [PMID: 32043524 DOI: 10.1093/bmb/ldz039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 11/25/2019] [Accepted: 11/26/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Intellectual disability (ID) affects 1-3% of the Western population and is heterogeneous in origin. Mutations in X-linked genes represent 5-10% of ID in males. Fragile X syndrome, due to the silencing of the FMR1 gene, is the most common form of ID, with a prevalence of around 1:5000 males. Females are usually non- or mildly affected carriers, and in a few rare cases, the only gender affected. Array comparative genome hybridization (aCGH) and next-generation sequencing (NGS) have dramatically changed the nature of human genome analysis leading to the identification of new X-linked intellectual disability syndromes and disease-causing genes. SOURCES OF DATA Original papers, reviews, guidelines and experiences of the diagnostic laboratories. AREAS OF AGREEMENT Family history and clinical examination still are essential to choose the appropriate diagnostic tests, including, a disease-specific genetic test, aCGH or FMR1 molecular analysis. If negative, NGS approaches like well-defined gene panels, whole exome, or even whole genome sequencing, are increasingly being used, improving diagnostics and leading to the identification of novel disease mechanisms. AREAS OF CONTROVERSY The main challenge in the era of NGS is filtering and interpretation of the data generated by the analysis of a single individual. In X-linked cases, assessing pathogenicity is particularly challenging, even more when the variant is found to be inherited from a healthy carrier mother or when a heterozygous X-linked mutation is found in an impaired female. GROWING POINTS At present, variant interpretation remains a challenging task, especially in X-linked disorders. We review the main difficulties and propose a comprehensive overview that might aid in variant interpretation. Establishing a genetic diagnosis facilitates counseling and allows better delineation of clinical phenotypes. AREAS TIMELY FOR DEVELOPING RESEARCH To improve variant interpretation, there is need to refine in silico predictions with specific criteria for each gene, and to develop cost-effective functional tools, which can be easily transferred to diagnostics.
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Affiliation(s)
- Chiara De Luca
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Valérie Race
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Liesbeth Keldermans
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Marijke Bauters
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Hilde Van Esch
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium.,Laboratory for the Genetics of Cognition, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
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Turner H, Jackson L. Evidence for penetrance in patients without a family history of disease: a systematic review. Eur J Hum Genet 2020; 28:539-550. [PMID: 31937893 PMCID: PMC7170932 DOI: 10.1038/s41431-019-0556-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/08/2019] [Accepted: 11/26/2019] [Indexed: 01/21/2023] Open
Abstract
Family-based penetrance is frequently cited as a major challenge for translating penetrance estimates from familial populations to asymptomatic populations. A systematic review was performed to assess the literature evidencing penetrance estimates in patients without a family history of disease, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework. Initially 1592 papers were identified, which were filtered to a final nine, through application of inclusion and exclusion criteria. Fundamental differences in the identified papers prevented combination of papers using meta-analysis, so thematic analysis to produce a narrative synthesis was performed. Key themes included disease risk modifiers, evidence, study limitations and bias. A methodological appraisal too was used to assess quality of included studies. It is evident from the findings that the evidence base for penetrance estimates in individuals without a family history of disease is limited. Future work is needed to refine design of penetrance studies and the impact of incorrect estimates.
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Affiliation(s)
- Heather Turner
- University of Exeter Medical School, 4.07 RILD, Royal Devon & Exeter Hospital, Barrack Road, Exeter, EX2 5DW, UK
| | - Leigh Jackson
- University of Exeter Medical School, 4.07 RILD, Royal Devon & Exeter Hospital, Barrack Road, Exeter, EX2 5DW, UK.
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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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Zhang Q, Zhao Y, Bao X, Luo J, Zhang X, Li J, Wei L, Wu X. Familial cases and male cases with MECP2 mutations. Am J Med Genet B Neuropsychiatr Genet 2017; 174:451-457. [PMID: 28394482 PMCID: PMC5485058 DOI: 10.1002/ajmg.b.32534] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/06/2017] [Indexed: 12/03/2022]
Abstract
This is the first report of Chinese familial cases with Rett syndrome (RTT) or X-linked mental retardation (XLMR). RTT is a neurodevelopmental disorder that almost exclusively affects females. Most RTT cases are sporadic. We have studied eight cases with MECP2 mutations in six Chinese families, including three females and five males with RTT or XLMR. All shared identical MECP2 mutations with their mothers. The three females fulfilled the diagnostic criteria for RTT, while the five males were XLMR. A random X-chromosome inactive (XCI) pattern was seen in all the three female patients and two mothers while a skewed XCI in the rest four mothers. The clinical manifestations and pathogenic gene spectrum between male and female patients were different. The different MECP2 mutations and different XCI pattern may be the determinants of the phenotypic heterogeneity between the family members.
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Affiliation(s)
- Qingping Zhang
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Ying Zhao
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Xinhua Bao
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Jinjun Luo
- Departments of Neurology and PharmacologyLewis Katz School of Medicine at Temple UniversityPhiladelphiaPennsylvania
| | - Xiaoying Zhang
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Jiarui Li
- State Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking University, Center for BioinformaticsBeijingChina
| | - Liping Wei
- State Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking University, Center for BioinformaticsBeijingChina
| | - Xiru Wu
- Department of PediatricsPeking University First HospitalBeijingChina
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Reichow B, George-Puskar A, Lutz T, Smith IC, Volkmar FR. Brief report: systematic review of Rett syndrome in males. J Autism Dev Disord 2016; 45:3377-83. [PMID: 26254891 DOI: 10.1007/s10803-015-2519-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Rett syndrome (RTT) is a neurogenetic disorder in which a period of typical development is followed by loss of previously acquired skills. Once thought to occur exclusively in females, increasing numbers of male cases of RTT have been reported. This systematic review included 36 articles describing 57 cases of RTT in males. Mutations of the MECP2 gene were present in 56 % of cases, and 68 % of cases reported other genetic abnormalities. This is the first review of published reports of RTT in male patients.
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Affiliation(s)
- Brian Reichow
- AJ Pappanikou Center for Excellence in Developmental Disabilities, University of Connecticut Health Center, Farmington, CT, USA.
- University of Florida, 1345Q Norman Hall, PO Box 117050, Gainesville, FL, 32661-7050, USA.
| | | | - Tara Lutz
- University of Connecticut, Storrs, CT, USA
| | - Isaac C Smith
- AJ Pappanikou Center for Excellence in Developmental Disabilities, University of Connecticut Health Center, Farmington, CT, USA
- Yale Child Study Center, New Haven, CT, USA
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Soffer OD, Sidlow R. A rare MeCP2_e1 mutation first described in a male patient with severe neonatal encephalopathy. Am J Med Genet A 2016; 170:1881-3. [PMID: 27090848 DOI: 10.1002/ajmg.a.37665] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 04/03/2016] [Indexed: 11/11/2022]
Abstract
Specific mutations in MECP2 cause Rett syndrome (RTT) in females whereas other mutations in the same gene cause several other syndromes in males, including X-linked intellectual disability (with and without spasticity) (OMIM 300055) and X-linked intellectual disability due to increased dosage of MECP2 (OMIM 300260). Males can also manifest an entity known as MECP2-related severe neonatal encephalopathy whose mutations are identical to those in females with RTT. We describe here the first case of MECP2-related severe neonatal encephalopathy caused by a mutation in exon one of MECP2, a mutation rarely identified in females with RTT. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Omri David Soffer
- Department of Pediatrics, Staten Island University Hospital, Staten Island, New York, New York
| | - Richard Sidlow
- Department of Pediatrics, Staten Island University Hospital, Staten Island, New York, New York.,Department of Pediatrics and Internal Medicine, State University of New York Health Science Center at Brooklyn, Brooklyn, New York
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Abstract
The role of epigenetics in human disease has become an area of increased research interest. Collaborative efforts from scientists and clinicians have led to a better understanding of the molecular mechanisms by which epigenetic regulation is involved in the pathogenesis of many human diseases. Several neurological and non-neurological disorders are associated with mutations in genes that encode for epigenetic factors. One of the most studied proteins that impacts human disease and is associated with deregulation of epigenetic processes is Methyl CpG binding protein 2 (MeCP2). MeCP2 is an epigenetic regulator that modulates gene expression by translating epigenetic DNA methylation marks into appropriate cellular responses. In order to highlight the importance of epigenetics to development and disease, we will discuss how MeCP2 emerges as a key epigenetic player in human neurodevelopmental, neurological, and non-neurological disorders. We will review our current knowledge on MeCP2-related diseases, including Rett Syndrome, Angelman Syndrome, Fetal Alcohol Spectrum Disorder, Hirschsprung disease, and Cancer. Additionally, we will briefly discuss about the existing MeCP2 animal models that have been generated for a better understanding of how MeCP2 impacts certain human diseases.
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Affiliation(s)
| | - Mojgan Rastegar
- Author to whom correspondence should be addressed; ; Tel.: +204-272-3108; Fax: +204-789-3900
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10
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Abstract
This chapter focuses on neurodevelopmental diseases that are tightly linked to abnormal function of the striatum and connected structures. We begin with an overview of three representative diseases in which striatal dysfunction plays a key role--Tourette syndrome and obsessive-compulsive disorder, Rett's syndrome, and primary dystonia. These diseases highlight distinct etiologies that disrupt striatal integrity and function during development, and showcase the varied clinical manifestations of striatal dysfunction. We then review striatal organization and function, including evidence for striatal roles in online motor control/action selection, reinforcement learning, habit formation, and action sequencing. A key barrier to progress has been the relative lack of animal models of these diseases, though recently there has been considerable progress. We review these efforts, including their relative merits providing insight into disease pathogenesis, disease symptomatology, and basal ganglia function.
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12
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Sanmann JN, Schaefer GB, Buehler BA, Sanger WG. Algorithmic approach for methyl-CpG binding protein 2 (MECP2) gene testing in patients with neurodevelopmental disabilities. J Child Neurol 2012; 27:346-54. [PMID: 22123427 DOI: 10.1177/0883073811424796] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Methyl-CpG binding protein 2 gene (MECP2) testing is indicated for patients with numerous clinical presentations, including Rett syndrome (classic and atypical), unexplained neonatal encephalopathy, Angelman syndrome, nonspecific mental retardation, autism (females), and an X-linked family history of developmental delay. Because of this complexity, a gender-specific approach for comprehensive MECP2 gene testing is described. Briefly, sequencing of exons 1 to 4 of MECP2 is recommended for patients with a Rett syndrome phenotype, unexplained neonatal encephalopathy, an Angelman syndrome phenotype (with negative 15q11-13 analysis), nonspecific mental retardation, or autism (females). Additional testing for large-scale MECP2 deletions is recommended for patients with Rett syndrome or Angelman syndrome phenotypes (with negative 15q11-13 analysis) following negative sequencing. Alternatively, testing for large-scale MECP2 duplications is recommended for males presenting with mental retardation, an X-linked family history of developmental delay, and a significant proportion of previously described clinical features (particularly a history of recurrent respiratory infections).
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Affiliation(s)
- Jennifer N Sanmann
- Human Genetics Laboratories, University of Nebraska Medical Center and the Munroe-Meyer Institute for Genetics and Rehabilitation, Omaha, NE 68198-5440, USA.
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Khajuria R, Gupta N, Sapra S, Gulati S, Ghosh M, Kalra V, Kabra M. Novel non-identical MECP2 mutations in Rett syndrome family: a rare presentation. Brain Dev 2012; 34:28-31. [PMID: 21300488 DOI: 10.1016/j.braindev.2011.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/26/2010] [Accepted: 01/12/2011] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Rett syndrome (RS), an X-linked neurodevelopmental disorder and the common cause of mental retardation in females, is caused by methyl CpG binding protein 2 (MECP2) gene mutations with a frequency of more than 95% in classical Rett patients. Majority of RS cases are sporadic but few familial cases caused by either skewed X-chromosome inactivation in healthy female carriers or mosaicism in male carriers are also reported. Most of the times, the mutation carried in a family is the same as found in affected child. METHODS AND RESULTS Here we report a unique family carrying non-identical MECP2 mutations in exon 2 wherein the proband with classical RS was carrying a de-novo early truncating frameshift mutation while her asymptomatic mother was carrying a missense mutation, both predicted as pathogenic mutations. CONCLUSIONS These findings further validate the importance of MECP2 mutation screening in parents of all mutation positive patients and careful evaluation of the pathogenicity of the mutation found in asymptomatic carriers before providing genetic counseling to the family. The results also propose the role of other factors including other gene mutations, environmental and epigenetics factors in modifying the expression of MECP2 mutations.
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Affiliation(s)
- Rajni Khajuria
- Genetics Unit, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi 110029, India
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Mittal K, Gupta N, Kabra M, Juyal R, Thelma BK. Distinct de novo deletions in a brother-sister pair with RTT: a case report. Am J Med Genet B Neuropsychiatr Genet 2011; 156B:859-63. [PMID: 21812101 DOI: 10.1002/ajmg.b.31222] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 05/31/2011] [Indexed: 11/10/2022]
Abstract
Rett syndrome (RTT), a neurodevelopmental disorder caused by mutations in the X-linked gene encoding methyl-CpG-binding protein2 (MeCP2), is a leading cause of mental retardation in females. Majority of cases are sporadic (99%) but some familial cases have also been observed. We describe a familial study with a brother-sister pair with symptoms of RTT and exhibiting distinct deletions in the MECP2. The non-shared de novo deletion in the two sibs provides important insights into the disease etiology, especially for male sibs showing varied phenotypes as compared to the classical ones seen in the females.
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Affiliation(s)
- Kirti Mittal
- Department of Genetics, University of Delhi South Campus, India
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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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Abstract
We report a three generation family in which five members, three females and two males, demonstrate a 44 bp deletion (1164-1207del44) in the MECP2 gene associated with Rett syndrome, leading to a truncation of the C-terminus of the protein. Two of the three females and both males do not meet RTT criteria whereas the youngest female has classic RTT. Both males demonstrated a clear pattern of progressive involvement including dystonia. The transmitting females do not demonstrate features of RTT as a result of unbalanced X chromosome inactivation (XCI) and were only identified as carriers following the evaluation of the affected males and the girl with classic RTT. As such, accurate assessment of the precise frequency of MECP2 mutations in carrier females with mild cognitive impairment or borderline cognitive function will be under-represented unless an affected offspring is recognized. Strategies for accurate diagnosis in such instances should be considered carefully.
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Affiliation(s)
- Kimberly Augenstein
- Neuromuscular and Rehabilitation Associates of Northern Michigan, Traverse City, MI, USA
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Khajuria R, Gupta N, Sapra S, Gulati S, Ghosh M, Kalra V, Kabra M. A novel MECP2 change in an indian boy with variant rett phenotype and congenital blindness: implications for genetic counseling and prenatal diagnosis. J Child Neurol 2011; 26:209-13. [PMID: 21285040 DOI: 10.1177/0883073810378535] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mutations in MECP2 gene are the primary cause of Rett syndrome, a neurodevelopmental disorder that primarily affects girls, and affect 90% to 95% patients with classical Rett syndrome. MECP2 mutations, once thought to be lethal in males, now present a broad spectrum of clinical manifestations in males. This article reports a family with a 9-year-old boy with Rett-like phenotype and congenital blindness, who inherited a novel MECP2 variant (p.P430S) from his asymptomatic mother. The variant was also identified in the asymptomatic maternal grandfather and maternal aunts of the proband, ruling out the possibility that the p.P430S was involved in the phenotype. Findings of the study suggest that a careful evaluation of the pathogenic nature of MECP2 variants identified in males be conducted before proposing genetic counseling or prenatal diagnosis to the family and that the interference of other factors like modifier genes, environment, epigenetics, and mosaicism be taken into account.
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Affiliation(s)
- Rajni Khajuria
- Genetics Unit, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India
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Bountra C, Oppermann U, Heightman TD. Animal models of epigenetic regulation in neuropsychiatric disorders. Curr Top Behav Neurosci 2011; 7:281-322. [PMID: 21225415 DOI: 10.1007/7854_2010_104] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Epigenetics describes the phenomenon of heritable changes in gene regulation that are governed by non-Mendelian processes, primarily through biochemical modifications to chromatin structure that occur during cell development and differentiation. Numerous lines of evidence link abnormal levels of chromatin modifications (either to DNA, histones, or both) in patients with a wide variety of diseases including cancer, psychiatry, neurodegeneration, metabolic and inflammatory disorders. Drugs that target the proteins controlling chromatin modifications can modulate the expression of clusters of genes, potentially offering higher therapeutic efficacy than classical agents with single target pharmacologies that are susceptible to biochemical pathway degeneracy. Here, we summarize recent research linking epigenetic dysregulation with diseases in neurosciences, the application of relevant animal models, and the potential for small molecule modulator development to facilitate target discovery, validation and translation into clinical treatments.
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Affiliation(s)
- Chas Bountra
- Structural Genomics Consortium, University of Oxford, Oxford, OX3 7DQ, UK,
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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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20
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Psoni S, Sofocleous C, Traeger-Synodinos J, Kitsiou-Tzeli S, Kanavakis E, Fryssira-Kanioura H. Phenotypic and genotypic variability in four males with MECP2 gene sequence aberrations including a novel deletion. Pediatr Res 2010; 67:551-6. [PMID: 20098342 DOI: 10.1203/pdr.0b013e3181d4ecf7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The MECP2 gene mutations cause Rett syndrome (RTT) (OMIM: 312750), an X-linked dominant disorder primarily affecting girls. Until RTT was considered lethal in males, although now approximately 60 cases have been reported. Males with MECP2 mutations present with a broad spectrum of phenotypes ranging from neonatal encephalopathy to nonsyndromic mental retardation (MR). Four boys (aged, 3-11 y) were evaluated for MR. Patient 1 had autistic features. Patients 2 and 3 were brothers both presenting with psychomotor delay. Patient 4 showed dysmorphic features and behavioral problems reminiscent of FXS. All patients had a normal 46, XY karyotype and three were tested for FXS with negative results. MECP2 gene analysis of exons 3 and 4 was performed using methods based on the PCR, including Enzymatic Cleavage Mismatched Analysis (ECMA) and direct sequencing. Patient 1 presented somatic mosaicism for the classic RTT p.R106W mutation and patient 4 carried the p.T203M polymorphism. Analysis of the mothers in both cases revealed normal DNA sequences. Patients 2 and 3 had a novel deletion (c.1140del86) inherited from their unaffected mother. MECP2 gene mutations may be considered a rare cause of MR in males although great phenotypic variation hinders genotype-phenotype correlation.
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Affiliation(s)
- Stavroula Psoni
- Department of Medical Genetics, University of Athens School of Medicine, Choremio Research Laboratory, Aghia Sophia Children's Hospital, Athens 11527, Greece
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Condie J, Goldstein J, Wainwright MS. Acquired microcephaly, regression of milestones, mitochondrial dysfunction, and episodic rigidity in a 46,XY male with a de novo MECP2 gene mutation. J Child Neurol 2010; 25:633-6. [PMID: 20142466 DOI: 10.1177/0883073809342004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We report a case of acquired microcephaly in a male infant. Testing for mutations in the MECP2 gene identified a de novo hemizygous c.378-3C>G mutation at a highly conserved 3' splice site, consistent with Rett syndrome. Other distinctive features included periodic hypertonicity, decreased mitochondrial complex III activity, and abnormal magnetic resonance imaging (MRI) T2 signal in the pons. Rett syndrome was originally described in females with a clinical phenotype of deceleration of head growth, abnormal hand movements, and developmental regression. The clinical diagnosis can now be supported by genetic testing for MECP2 mutations, and the phenotype of disorder has expanded. Cases of Rett syndrome in males are rare and a total of 17 such cases have been reported. This case extends the clinical phenotype of Rett syndrome in males and associates this mutation with mitochondrial dysfunction.
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Affiliation(s)
- John Condie
- Department of Pediatrics, Division of Neurology, Children's Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60614, USA
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22
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Makrythanasis P, Moix I, Gimelli S, Fluss J, Aliferis K, Antonarakis SE, Morris MA, Béna F, Bottani A. De novo duplication of MECP2 in a girl with mental retardation and no obvious dysmorphic features. Clin Genet 2010; 78:175-80. [DOI: 10.1111/j.1399-0004.2010.01371.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mantis JG, Fritz CL, Marsh J, Heinrichs SC, Seyfried TN. Improvement in motor and exploratory behavior in Rett syndrome mice with restricted ketogenic and standard diets. Epilepsy Behav 2009; 15:133-41. [PMID: 19249385 DOI: 10.1016/j.yebeh.2009.02.038] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 02/18/2009] [Accepted: 02/20/2009] [Indexed: 12/25/2022]
Abstract
Rett syndrome (RTT) is a rare X-linked autistic-spectrum neurological disorder associated with impaired energy metabolism, seizure susceptibility, progressive social behavioral regression, and motor impairment primarily in young girls. The objective of this study was to examine the influence of restricted diets, including a ketogenic diet (KD) and a standard rodent chow diet (SD), on behavior in male Mecp2(308/y) mice, a model of RTT. The KD is a high-fat, low-carbohydrate diet that has anticonvulsant efficacy in children with intractable epilepsy and may be therapeutic in children with RTT. Following an 11-day pretrial period, adult wild-type and mutant Rett mice were separated into groups that were fed either an SD in unrestricted or restricted amounts or a ketogenic diet (KetoCal) in restricted amounts for a total of 30 days. The restricted diets were administered to reduce mouse body weight by 20-23% compared to the body weight of each mouse before the initiation of the diet. All mice were subjected to a battery of behavioral tests to determine the influence of the diet on the RTT phenotype. We found that performance in tests of motor behavior and anxiety was significantly worse in male RTT mice compared to wild-type mice and that restriction of either the KD or the SD improved motor behavior and reduced anxiety. We conclude that although both restricted diets increased the tendency of Rett mice to explore a novel environment, the beneficial effects of the KD were due more to calorie restriction than to the composition of the diet. Our findings suggest that calorically restricted diets could be effective in reducing the anxiety and in improving motor behavior in girls with RTT.
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Affiliation(s)
- John G Mantis
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
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24
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Orstavik KH. X chromosome inactivation in clinical practice. Hum Genet 2009; 126:363-73. [PMID: 19396465 DOI: 10.1007/s00439-009-0670-5] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 04/07/2009] [Indexed: 01/19/2023]
Abstract
X chromosome inactivation (XCI) is the transcriptional silencing of the majority of genes on one of the two X chromosomes in mammalian females. Females are, therefore, mosaics for two cell lines, one with the maternal X and one with the paternal X as the active chromosome. The relative proportion of the two cell lines, the X inactivation pattern, may be analyzed by simple assays in DNA from available tissues. This review focuses on medical issues related to XCI in X-linked disorders, and on the value of X inactivation analysis in clinical practice.
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Affiliation(s)
- Karen Helene Orstavik
- Department of Medical Genetics, Oslo University Hospital, Rikshospitalet and Faculty Division Rikshospitalet, University of Oslo, Forskningsveien 2B, 0027, Oslo, Norway.
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Tao J, Wu H, Sun YE. Deciphering Rett syndrome with mouse genetics, epigenomics, and human neurons. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2009; 89:147-60. [PMID: 19900619 DOI: 10.1016/s0074-7742(09)89007-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mutations of MECP2 (methyl-CpG binding protein 2) cause Rett syndrome (RTT). Mouse genetics studies have demonstrated that the lack of functional MeCP2 in the central nervous system leads to RTT-like symptoms, which could be reversed upon MeCP2 restoration. MeCP2 recognizes methylated CpG dinucleotides and may interact with other chromatin remodeling proteins. Although traditionally thought to be a transcription repressor, MeCP2 may also be involved in transcription activation. With the development of new technologies, deciphering the role of MeCP2 on a genome-wide scale is important for understanding of the RTT disease mechanisms.
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Affiliation(s)
- Jifang Tao
- Department of Molecular & Medical Pharmacology and Psychiatry & Behavioral Sciences, University of California, Los Angeles, CA, USA
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26
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Rosser LG, McKee S, Millar DS, Archer H, Hughes J, Butler R, Chuzhanova N, Cooper DN, Lazarou LP. Two sisters with Rett syndrome and non-identical paternally-derived microdeletions in the MECP2 gene. Genomic Med 2008; 2:77-81. [PMID: 18810657 DOI: 10.1007/s11568-008-9026-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 08/26/2008] [Accepted: 08/27/2008] [Indexed: 11/29/2022] Open
Abstract
The unique case of two sisters with symptoms of RTT and two quite distinct, novel, and apparently de novo microdeletions of the MECP2 gene is described. One sister possessed an 18 base-pair (bp) deletion (c.1155_1172del18) within the deletion hotspot region of exon 4, whereas the other sister exhibited a 43 bp deletion at a different location in the same exon (c.1448_1461del14+29). Although these lesions occurred on the same paternally-derived X chromosome, this is probably due to chance co-occurrence owing to the relatively high mutation rate of the MECP2 gene rather than to a constitutional mutator phenotype.
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Affiliation(s)
- Lyndon G Rosser
- Institute of Medical Genetics, Cardiff and Vale NHS Trust, University Hospital of Wales, Heath Park, Cardiff, CF14 4XW, UK
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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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28
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Abstract
The postnatal neurodevelopmental disorder Rett syndrome (RTT) is caused by mutations in the gene encoding methyl-CpG binding protein 2 (MeCP2), a transcriptional repressor involved in chromatin remodeling and the modulation of RNA splicing. MECP2 aberrations result in a constellation of neuropsychiatric abnormalities, whereby both loss of function and gain in MECP2 dosage lead to similar neurological phenotypes. Recent studies demonstrate disease reversibility in RTT mouse models, suggesting that the neurological defects in MECP2 disorders are not permanent. To investigate the potential for restoring neuronal function in RTT patients, it is essential to identify MeCP2 targets or modifiers of the phenotype that can be therapeutically modulated. Moreover, deciphering the molecular underpinnings of RTT is likely to contribute to the understanding of the pathogenesis of a broader class of neuropsychiatric disorders.
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Affiliation(s)
- Maria Chahrour
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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Hardwick SA, Reuter K, Williamson SL, Vasudevan V, Donald J, Slater K, Bennetts B, Bebbington A, Leonard H, Williams SR, Smith RL, Cloosterman D, Christodoulou J. Delineation of large deletions of the MECP2 gene in Rett syndrome patients, including a familial case with a male proband. Eur J Hum Genet 2007; 15:1218-29. [PMID: 17712354 DOI: 10.1038/sj.ejhg.5201911] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Comprehensive genetic screening programs have led to the identification of pathogenic methyl-CpG-binding protein 2 (MECP2) mutations in up to 95% of classical Rett syndrome (RTT) patients. This high rate of mutation detection can partly be attributed to specialised techniques that have enabled the detection of large deletions in a substantial fraction of otherwise mutation-negative patients. These cases would normally be missed by the routine PCR-based screening strategies. Here, we have identified large multi-exonic deletions in 12/149 apparently mutation-negative RTT patients using multiplex ligation-dependent probe amplification (MLPA). These deletions were subsequently characterised using real-time quantitative PCR (qPCR) and long-range PCR with the ultimate aim of defining the exact nucleotide positions of the breakpoints and rearrangements. We detected an apparent deletion in one further patient using MLPA; however, this finding was contradicted by subsequent qPCR and long-range PCR results. The patient group includes an affected brother and sister with a large MECP2 deletion also present in their carrier mother. The X chromosome inactivation pattern of all female patients in this study was determined, which, coupled with detailed clinical information, allowed meaningful genotype-phenotype correlations to be drawn. This study reaffirms the view that large MECP2 deletions are an important cause of both classical and atypical RTT syndrome, and cautions that apparent deletions detected using high-throughput diagnostic techniques require further characterisation.
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Affiliation(s)
- Simon A Hardwick
- Department of Biological Sciences, Macquarie University, Sydney, Australia
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Abstract
Rett syndrome (RS; MIM 312750) is a severe neurological disorder affecting exclusively females. Its prevalence is about 1 in 10,000 female births, and it is a prominent cause of profound mental handicap in women. RS is caused by mutations in the X-linked methyl CpG-binding protein 2 (MECP2) gene. These mutations were initially thought to be lethal in males. However, MECP2 mutations are now frequently identified in mentally retarded male patients. The frequency of disease-causing MECP2 mutations in this population is between 1.3% and 1.7%. Surprisingly, MECP2 mutations in males are responsible for a wide spectrum of neurological disorders, ranging from mild mental retardation to severe neonatal encephalopathy. The aim of this review is to describe the nature of the MECP2 mutations identified in male patients to date and their associated phenotypes.
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Affiliation(s)
- Laurent Villard
- INSERM, U491, Faculté de Médecine de La Timone, 27 boulevard Jean Moulin, 13385 Marseille cedex 5, France.
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