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Réthelyi JM, Vincze K, Schall D, Glennon J, Berkel S. The role of insulin/IGF1 signalling in neurodevelopmental and neuropsychiatric disorders - Evidence from human neuronal cell models. Neurosci Biobehav Rev 2023; 153:105330. [PMID: 37516219 DOI: 10.1016/j.neubiorev.2023.105330] [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: 09/30/2022] [Revised: 07/15/2023] [Accepted: 07/26/2023] [Indexed: 07/31/2023]
Abstract
Insulin and insulin-like growth factor 1 (IGF1) signalling play a central role in the development and maintenance of neurons in the brain, and human neurodevelopmental as well as neuropsychiatric disorders have been linked to impaired insulin and IGF1 signalling. This review focuses on the impairments of the insulin and IGF1 signalling cascade in the context of neurodevelopmental and neuropsychiatric disorders, based on evidence from human neuronal cell models. Clear evidence was obtained for impaired insulin and IGF1 receptor downstream signalling in neurodevelopmental disorders, while the evidence for its role in neuropsychiatric disorders was less substantial. Human neuronal model systems can greatly add to our knowledge about insulin/IGF1 signalling in the brain, its role in restoring dendritic maturity, and complement results from clinical studies and animal models. Moreover, they represent a useful model for the development of new therapeutic strategies. Further research is needed to systematically investigate the exact role of the insulin/IGF1 signalling cascades in neurodevelopmental and neuropsychiatric disorders, and to elucidate the respective therapeutic implications.
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Affiliation(s)
- János M Réthelyi
- Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary
| | - Katalin Vincze
- Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary; Doctoral School of Mental Health Sciences, Semmelweis University, Budapest, Hungary
| | - Dorothea Schall
- Institute of Human Genetics, Heidelberg University, Heidelberg, Germany
| | - Jeffrey Glennon
- Conway Institute of Biomedical and Biomolecular Research, School of Medicine, University College Dublin, Dublin, Ireland
| | - Simone Berkel
- Institute of Human Genetics, Heidelberg University, Heidelberg, Germany; Interdisciplinary Centre of Neurosciences (IZN), Heidelberg University, Germany.
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2
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Shah J, Patel H, Jain D, Sheth F, Sheth H. A rare case of a male child with post-zygotic de novo mosaic variant c.538C > T in MECP2 gene: a case report of Rett syndrome. BMC Neurol 2021; 21:469. [PMID: 34856927 PMCID: PMC8638266 DOI: 10.1186/s12883-021-02500-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 11/21/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rett syndrome (RTT) is characterized by a normal perinatal period with a normal head size at birth followed by normal development for the first 6 months of life followed by gradual deceleration of head growth, loss of acquired purposeful hand skills, severe expressive and receptive language impairment, severe intellectual disability and gait and truncal apraxia/ ataxia. It is caused due to mutations in the MECP2 gene and follows an X-linked dominant mode of inheritance. It was observed exclusively in females and was believed to be lethal in males. In contrast to this belief, several males were identified with RTT upon genetic analysis, however, most males expired by the age of 2 years due to neonatal encephalopathy. The ones that survived beyond the age of 2 years, were attributed to the presence of an extra X chromosome (co-occurrence of Klinefelter and RTT) or the ones having mosaic cell lines. Only 11 males with somatic mosaicism are known till date. CASE PRESENTATION This case reports an ultra-rare case of a male affected with RTT surviving beyond the age of 2 years due to post-zygotic de novo somatic mosaicism. He was identified with a known pathogenic variant c.538C > T (p.R180*), which to the best of our knowledge is exclusively seen in females and has never been reported in a male before. CONCLUSION The present case is the first report of a mosaic male affected with RTT from India. The present report also carried out genotype-phenotype correlations across surviving mosaic males with RTT. We also postulate the effect of variant type, position along the gene and the variant allele fraction in different tissue types to be correlated with disease severity.
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Affiliation(s)
- Jhanvi Shah
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, 380015, Ahmedabad, India
| | | | - Deepika Jain
- Shishu Child Development and Early Intervention Centre, Ahmedabad, India
| | - Frenny Sheth
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, 380015, Ahmedabad, India.
| | - Harsh Sheth
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, 380015, Ahmedabad, India.
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Sabitha KR, Shetty AK, Upadhya D. Patient-derived iPSC modeling of rare neurodevelopmental disorders: Molecular pathophysiology and prospective therapies. Neurosci Biobehav Rev 2020; 121:201-219. [PMID: 33370574 DOI: 10.1016/j.neubiorev.2020.12.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 12/12/2022]
Abstract
The pathological alterations that manifest during the early embryonic development due to inherited and acquired factors trigger various neurodevelopmental disorders (NDDs). Besides major NDDs, there are several rare NDDs, exhibiting specific characteristics and varying levels of severity triggered due to genetic and epigenetic anomalies. The rarity of subjects, paucity of neural tissues for detailed analysis, and the unavailability of disease-specific animal models have hampered detailed comprehension of rare NDDs, imposing heightened challenge to the medical and scientific community until a decade ago. The generation of functional neurons and glia through directed differentiation protocols for patient-derived iPSCs, CRISPR/Cas9 technology, and 3D brain organoid models have provided an excellent opportunity and vibrant resource for decoding the etiology of brain development for rare NDDs caused due to monogenic as well as polygenic disorders. The present review identifies cellular and molecular phenotypes demonstrated from patient-derived iPSCs and possible therapeutic opportunities identified for these disorders. New insights to reinforce the existing knowledge of the pathophysiology of these disorders and prospective therapeutic applications are discussed.
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Affiliation(s)
- K R Sabitha
- Centre for Molecular Neurosciences, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India
| | - Ashok K Shetty
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M University College of Medicine, College Station, TX, USA.
| | - Dinesh Upadhya
- Centre for Molecular Neurosciences, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India.
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Kubota T, Miyake K, Hariya N, Mochizuki K. Epigenomic-basis of Preemptive Medicine for Neurodevelopmental Disorders. Curr Genomics 2015; 16:175-82. [PMID: 26069457 PMCID: PMC4460221 DOI: 10.2174/1389202916666150216221312] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 11/24/2022] Open
Abstract
Neurodevelopmental disorders (NDs) are currently thought to be caused by either genetic
defects or various environmental factors. Recent studies have demonstrated that congenital NDs can
result not only from changes in DNA sequence in neuronal genes but also from changes to the secondary
epigenomic modifications of DNA and histone proteins. Thus, epigenomic assays, as well as genomic
assays, are currently performed for diagnosis of the congenital NDs. It is recently known that
the epigenomic modifications can be altered by various environmental factors, which potentially cause
acquired NDs. Furthermore these alterations can potentially be restored taking advantage of use of reversibility in epigenomics.
Therefore, epigenome-based early diagnosis and subsequent intervention, by using drugs that restore epigenomic
alterations, will open up a new era of preemptive medicine for congenital and acquired NDs.
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Affiliation(s)
- Takeo Kubota
- Department of Epigenetic Medicine, Faculty of Medicine, University of Yamanashi, Japan
| | - Kunio Miyake
- Department of Epigenetic Medicine, Faculty of Medicine, University of Yamanashi, Japan
| | - Natsuyo Hariya
- Department of Epigenetic Medicine, Faculty of Medicine, University of Yamanashi, Japan
| | - Kazuki Mochizuki
- Department of Local Produce and Food Sciences, Faculty of Life and Environmental Sciences, University of Yamanashi, Japan
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Andoh-Noda T, Akamatsu W, Miyake K, Matsumoto T, Yamaguchi R, Sanosaka T, Okada Y, Kobayashi T, Ohyama M, Nakashima K, Kurosawa H, Kubota T, Okano H. Differentiation of multipotent neural stem cells derived from Rett syndrome patients is biased toward the astrocytic lineage. Mol Brain 2015; 8:31. [PMID: 26012557 PMCID: PMC4446051 DOI: 10.1186/s13041-015-0121-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 04/30/2015] [Indexed: 12/23/2022] Open
Abstract
Background Rett syndrome (RTT) is one of the most prevalent neurodevelopmental disorders in females, caused by de novo mutations in the X-linked methyl CpG-binding protein 2 gene, MECP2. Although abnormal regulation of neuronal genes due to mutant MeCP2 is thought to induce autistic behavior and impaired development in RTT patients, precise cellular mechanisms underlying the aberrant neural progression remain unclear. Results Two sets of isogenic pairs of either wild-type or mutant MECP2-expressing human induced pluripotent stem cell (hiPSC) lines were generated from a single pair of 10-year-old RTT-monozygotic (MZ) female twins. Mutant MeCP2-expressing hiPSC lines did not express detectable MeCP2 protein during any stage of differentiation. The lack of MeCP2 reflected altered gene expression patterns in differentiated neural cells rather than in undifferentiated hiPSCs, as assessed by microarray analysis. Furthermore, MeCP2 deficiency in the neural cell lineage increased astrocyte-specific differentiation from multipotent neural stem cells. Additionally, chromatin immunoprecipitation (ChIP) and bisulfite sequencing assays indicated that anomalous glial fibrillary acidic protein gene (GFAP) expression in the MeCP2-negative, differentiated neural cells resulted from the absence of MeCP2 binding to the GFAP gene. Conclusions An isogenic RTT-hiPSC model demonstrated that MeCP2 participates in the differentiation of neural cells. Moreover, MeCP2 deficiency triggers perturbation of astrocytic gene expression, yielding accelerated astrocyte formation from RTT-hiPSC-derived neural stem cells. These findings are likely to shed new light on astrocytic abnormalities in RTT, and suggest that astrocytes, which are required for neuronal homeostasis and function, might be a new target of RTT therapy. Electronic supplementary material The online version of this article (doi:10.1186/s13041-015-0121-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tomoko Andoh-Noda
- Division of Medicine and Engineering Science, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Yamanashi, Kofu, 400-8510, Japan. .,Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Wado Akamatsu
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan. .,Center for Genomic and Regenerative Medicine, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
| | - Kunio Miyake
- Department of Epigenetic Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan.
| | - Takuya Matsumoto
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Ryo Yamaguchi
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan. .,Sumitomo Dainipponn Pharma Co. Ltd., Osaka, Osaka, 541-0045, Japan.
| | - Tsukasa Sanosaka
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Yohei Okada
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan. .,Department of Neurology,School of Meidicine, Aichi Medical University, 1-1 Yazakokarimata, Nagakute, Aichi, 480-1195, Japan.
| | - Tetsuro Kobayashi
- Department of Dermatology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Manabu Ohyama
- Department of Dermatology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Kinichi Nakashima
- Department of Stem Cell Biology and Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
| | - Hiroshi Kurosawa
- Division of Medicine and Engineering Science, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Yamanashi, Kofu, 400-8510, Japan.
| | - Takeo Kubota
- Department of Epigenetic Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan.
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi,Shinjuku-ku, Tokyo, 160-8582, Japan.
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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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Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disease caused by MECP2 mutations. The MeCP2 protein was originally thought to function as a transcription repressor by binding to methylated CpG dinucleotides, but is now also thought to be a transcription activator. Recent studies suggest that MeCP2 is not only being expressed in neurons, but also in glial cells, which suggests a new paradigm for understanding the pathogenesis of RTT. It has also been demonstrated that reintroduction of MeCP2 into behaviorally affected Mecp2-null mice after birth rescues neurological symptoms, which indicates that epigenetic failures in RTT are reversible. Therefore, RTT may well be seen as a model disease that can be potentially treated by taking advantage of the reversibility of epigenetic phenomena in various congenital neurodevelopmental diseases that were previously thought to be untreatable.
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Affiliation(s)
- Takeo Kubota
- Department of Epigenetics Medicine, Interdisciplinary Graduate School of Medicine & Engineering, University of Yamanashi, Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Kunio Miyake
- Department of Epigenetics Medicine, Interdisciplinary Graduate School of Medicine & Engineering, University of Yamanashi, Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Takae Hirasawa
- Department of Epigenetics Medicine, Interdisciplinary Graduate School of Medicine & Engineering, University of Yamanashi, Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
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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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Abstract
Although genes have long been appreciated to play a critical role in determining the risk for pervasive developmental disorders, the specific transcripts contributing to autism spectrum disorders (ASD) have been quite difficult to characterize. However, recent findings are now providing the first insights into the molecular mechanisms underlying these syndromes and have begun to shed light on the allelic architecture of ASD. In this article, we address what is known about the relative contributions of various types of genetic variation to ASD, consider the obstacles facing gene discovery in this complex disorder, and evaluate the common methodologies employed to address these issues, including linkage, molecular and array-based cytogenetics, and association strategies. We review the current literature, highlighting recent findings implicating both rare mutations and common genetic polymorphisms in the etiology of autism. Finally, we describe key advances in genomic technologies that are transforming all areas of human genetics and consider both the opportunities and challenges for autism research posed by these rapid changes.
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Affiliation(s)
- Brian J O'Roak
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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10
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Abstract
The past decade has seen tremendous advances in our understanding of the molecular and genetic basis of many neuropsychiatric disorders. Although the genetic aberrations that lead to these syndromes have been identified in many cases, not much is known about specific gene products and their function. This article reviews the molecular basis of well-known neurogenetic disorders. The syndromes discussed here follow a Mendelian pattern of inheritance and are predominantly single-gene disorders; however, most childhood and adolescent psychiatric disorders are polygenic in nature. This genetic complexity and heterogeneity has made it difficult to identify the genes involved in their etiology. Identification of genetic and environmental risk factors involved in the etiology of complex disorders, such as autism, will help in the discovery of medications that can ameliorate the symptoms.
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Thorey F, Jäger M, Seller K, Wild A, Adam RA, Krauspe R. How to prevent small stature in Rett syndrome-associated collapsing spine syndrome. J Child Neurol 2007; 22:443-6. [PMID: 17621526 DOI: 10.1177/0883073807301927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Severe scoliosis in Rett syndrome is an important orthopedic, neurologic, and pediatric problem. The curve in Rett syndrome is of a neurologic type, has its highest incidence during early childhood, and shows rapid progression. In this study, the authors report the results of a 4-year follow-up of a 10-year-old Rett syndrome female patient with early onset and severe rapid progressive thoracolumbar scoliosis. The first signs of spinal deformity were documented at age 3 years. During adolescence, the patient developed a 115-degree thoracolumbal scoliosis with reduced respiratory volume due to a collapsing spine syndrome. To stop this life-threatening progression of the curve, the patient was treated by a 2-stage surgical procedure. The combination of an anterior release, halo traction, and posterior instrumented fusion from Th3 to L5 using a computer-assisted technique was performed. An excellent reduction of the deformity was achieved (postoperative 24-degree Cobb angle). After 4 years, the authors found a radiologically solid spinal fusion and no progression of the deformity. Operative treatment regimes and etiology of severe spinal deformities in Rett syndrome were discussed. The high perioperative risks in Rett syndrome patients who underwent spinal surgery may be reduced by an early cooperation between orthopedic and pediatric specialists. When considering recent data from literature, it can be concluded that an early correction of spine deformities in Rett syndrome patients may prevent a life-threatening collapsing spine syndrome.
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Affiliation(s)
- Fritz Thorey
- Department of Orthopedic Surgery, Hannover Medical School, Germany.
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Bienvenu T, Villard L, De Roux N, Bourdon V, Fontes M, Beldjord C, Tardieu M, Jonveaux P, Chelly J. Spectrum of MECP2 mutations in Rett syndrome. GENETIC TESTING 2002; 6:1-6. [PMID: 12180070 DOI: 10.1089/109065702760093843] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in the MECP2 (Methyl-CpG-binding protein) gene recently have been reported to cause Rett syndrome (RTT), an X-linked progressive encephalopathy. We have collected the results of MECP2 analysis conducted in four laboratories in France. A total of 301 RTT alleles have been analyzed, demonstrating a total of 69 different mutations so far observed and accounting for 64% of MECP2 genes in RTT patients living in France. R168X (11.5%) is the most common of MECP2 mutations, followed by R255X (10.9%), R270X (10.5%), T158M (7.8%), and R306C (6.8%). Only 10 mutations had a relative frequency > 2%. A total of 59 mutations were found in a small number of RTT alleles (from 1 to 2). These data demonstrate the high allelic heterogeneity of RTT in France and provide information relevant to the development of strategies for molecular diagnosis and genetic counseling in RTT families.
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Affiliation(s)
- Thierry Bienvenu
- INSERM U129-ICGM, Faculté de Médecine Cochin, 75014 Paris, France.
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Shahbazian MD, Zoghbi HY. Rett syndrome and MeCP2: linking epigenetics and neuronal function. Am J Hum Genet 2002; 71:1259-72. [PMID: 12442230 PMCID: PMC378559 DOI: 10.1086/345360] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2002] [Accepted: 10/01/2002] [Indexed: 11/03/2022] Open
Affiliation(s)
- Mona D. Shahbazian
- Departments of Molecular and Human Genetics, Pediatrics, Neurology, and Neuroscience and Howard Hughes Medical Institute, Baylor College of Medicine, Houston
| | - Huda Y. Zoghbi
- Departments of Molecular and Human Genetics, Pediatrics, Neurology, and Neuroscience and Howard Hughes Medical Institute, Baylor College of Medicine, Houston
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Dunn HG, Stoessl AJ, Ho HH, MacLeod PM, Poskitt KJ, Doudet DJ, Schulzer M, Blackstock D, Dobko T, Koop B, de Amorim GV. Rett syndrome: investigation of nine patients, including PET scan. Can J Neurol Sci 2002; 29:345-57. [PMID: 12463490 DOI: 10.1017/s0317167100002213] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND We describe nine females with Rett Syndrome (RS), aged 14 to 26 years. All had had developmental delay before the end of their first year and had subsequently regressed to profound dementia with apraxia, ataxia, irregular respirations and often also seizures. METHODS The Revised Gesell developmental assessment and Alpern-Boll Developmental Profile were used in modified form. Volumetric measurements of basal ganglia using MRI were compared with the findings in nine age-matched volunteer females. Positron emission scans with [18F]-6-fluorodopa and [11C]-raclopride were performed under light anesthesia with intravenous Propofol, and the findings were compared with those in healthy control girls. Bidirectional sequencing of the coding regions of the MECP2 gene was investigated in blood samples for mutational analyses. RESULTS The RS females functioned at a mental age level ranging from about 4 to 15 months. The scores correlated with height, weight and head circumference. Magnetic resonance scans of basal ganglia showed a significant reduction in the size of the caudate heads and thalami in the Rett cases. Positron emission scans demonstrated that the mean uptake of fluorodopa in RS was reduced by 13.1% in caudate and by 12.5% in putamen as compared to the controls, while dopamine D2 receptor binding was increased significantly by 9.7% in caudate and 9.6% in putamen. Mutations in the coding regions of the MECP2 gene were present in all nine patients. No significant correlation between type and location of mutation and volumetric changes or isotope uptake was demonstrable. CONCLUSIONS Our findings suggest a mild presynaptic deficit of nigrostriatal activity in Rett syndrome.
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Affiliation(s)
- Henry G Dunn
- Division of Neurology, Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada
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15
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Van den Veyver IB, Zoghbi HY. Genetic basis of Rett syndrome. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2002; 8:82-6. [PMID: 12112732 DOI: 10.1002/mrdd.10025] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The origin of Rett syndrome has long been debated, but several observations have suggested an X-linked dominant inheritance pattern. We and others have pursued an exclusion-mapping strategy using DNA from a small number of familial Rett syndrome cases. This work resulted in the narrowing of the region likely to harbor the mutated gene to Xq27.3-Xqter. After systematic exclusion of several candidate genes, we discovered mutations in MECP2, the gene that encodes the transcriptional repressor, methyl-CpG-binding protein 2. Since then, nonsense, missense, or frameshift mutations have been found in at least 80% of girls affected with classic Rett syndrome. Sixty-four percent of mutations are recurrent C > T transitions at eight CpG dinucleotides mutation hotspots, while the C-terminal region of the gene is prone to recurrent multinucleotide deletions (11%). Most mutations are predicted to result in total or partial loss of function of MeCP2. There is no clear correlation between the type and position of the mutation and the phenotypic features of classic and variant Rett syndrome patients, and XCI appears to be a major determinant of phenotypic severity. Further research focuses on the pathogenic consequences of these mutations along the hypothesis of loss of transcriptional repression of a small number of genes that are essential for neuronal function in the maturing brain.
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Hoffbuhr KC, Moses LM, Jerdonek MA, Naidu S, Hoffman EP. Associations between MeCP2 mutations, X-chromosome inactivation, and phenotype. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2002; 8:99-105. [PMID: 12112735 DOI: 10.1002/mrdd.10026] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rett syndrome is a neurodevelopmental disorder of early postnatal brain growth in girls. Patients show a normal neonatal period with subsequent developmental regression and a loss of acquired skills (communication and motor skills), deceleration of head growth, and development of typical hand stereotypies. Recent studies have shown that mutations in the X-linked methyl CpG binding protein 2 gene (MeCP2) cause most typical cases of Rett syndrome. The MeCP2 gene encodes a protein that binds methylated cytosine residues of CpG dinucleotides and mediates, with histone deacetylases and transcriptional repressors, the transcription "silencing" of other genes. Girls with Rett syndrome exhibit mosaic expression for the MeCP2 defect at the cellular level, with most patients showing random X-inactivation and approximately equal numbers of cells expressing the normal MeCP2 gene and the mutated MeCP2 gene. In rare cases, females with a MeCP2 mutation escape phenotypic expression of the disorder because of nonrandom X-inactivation and the preferential inactivation of the mutated MeCP2 allele. Nonrandom patterns of X-inactivation may also contribute to the clinical variability often seen in girls with Rett syndrome. The spectrum of clinical phenotype caused by MeCP2 mutations is wide, including milder "preserved speech" variants, the severe congenital Rett variant, and a subset of X-linked recessive mental retardation in boys. Studies have shown that atypical and classical Rett syndrome can caused by the same MeCP2 mutations, indicating clinical phenotype is variable even among girls with the same MeCP2 mutation. The relationship between type of MeCP2 mutation, X-inactivation status, and clinical phenotype of Rett syndrome is complex and likely involves other environmental and polygenic modifiers.
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Affiliation(s)
- K C Hoffbuhr
- Research Center for Genetic Medicine, Children's National Medical Center, Washington D.C 20010, USA
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Abstract
The syndrome of brain atrophy in girls described by Andreas Rett in 1966 [Rett, Wien Klin Wochenschr, 1966;116:723-726] was brought to the attention of the English-speaking world by Hagberg et al. in 1983 [Hagberg et al., Ann Neurol, 1983;14:471-479]. Four clinical stages after the age of 6 months were described in classical cases of Rett syndrome (RS), namely early onset stagnation at 6 months to 1(1/2) years, the rapid destructive stage at 1-3 years, the pseudo-stationary stage from pre-school to school years, and the late motor deterioration stage at 15-30 or more years. The rapid destructive stage causes profound dementia with loss of speech and hand skills, stereotypic movements, ataxia, apraxia, irregular breathing with hyperventilation while awake, and frequently seizures. Most cases are isolated in their families, apart from identical twins. However, linkage studies in rare familial cases suggested a critical region at Xq28. In 1999 American investigators found several mutations in the X-linked gene MECP2 encoding Methyl-CpG-binding protein 2 in a proportion of Rett patients. The protein MeCP2 can bind methylated DNA and when mutated may interfere with transcriptional silencing of other genes and result in abnormal chromatin assembly. Many different mutations of the protein are being studied in humans and in mice. Neuropathological studies have shown decreased brain growth and decreased size of individual neurons, with thinned dendrites in some cortical layers, and abnormalities in substantia nigra, suggestive of deficient synaptogenic development, probably starting before birth. Electrophysiology demonstrates progressively abnormal electroencephalograms (EEG) in the first three stages of the syndrome, with some subsequent improvement and occurrence of pseudoseizures. Neurometabolic factors are discussed in detail, particularly reduced levels of dopamine, serotonin, noradrenaline and choline acetyltransferase (ChAT) in brain, also estimation of nerve growth factors, endorphin, substance P, glutamate and other amino acids and their receptor levels. Autonomic dysfunction is described, particularly reduced vagal and overactive sympathetic activity. Neuro-imaging may be required for further investigation, as shown in the differential diagnosis.
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Affiliation(s)
- H G Dunn
- Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada.
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18
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Nan X, Bird A. The biological functions of the methyl-CpG-binding protein MeCP2 and its implication in Rett syndrome. Brain Dev 2001; 23 Suppl 1:S32-7. [PMID: 11738839 DOI: 10.1016/s0387-7604(01)00333-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Methylation of DNA is essential for development in the mouse and plays an important role in inactivation of the X-chromosome, genomic imprinting and gene silencing. The properties of the methyl-CpG binding proteins (MeCPs) are being proved to be the key to interpreting the connection between DNA methylation and transcriptional repression. The founder member of the family, MeCP2, consists of a single polypeptide that contains both a methyl-CpG binding domain (MBD) and transcriptional repression domain (TRD). MBD binds to a single symmetrically methylated CpG site and is responsible for chromatin localization of the protein. NMR studies have revealed that the MBD adopts a wedge-shaped molecular structure. The TRD interacts with Sin3, which is known to form complexes with histone deacetylases. MeCP2-mediated transcriptional repression may involve two distinct mechanisms, one being dependent on chromatin modification by histone deacetylation and the other being chromatin independent. Mutations in MeCP2 gene cause the X-linked neurodevelopmental disease Rett syndrome. The spectrum of mutations reflects the importance of the MBD and TRD domains. We speculate that abnormal gene expression in Rett patients leads to dysfunction of the central nervous system. We propose a genetic therapeutic approach based on activation of the wild type copy of the MeCP2 gene located in the inactive X chromosome.
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Affiliation(s)
- X Nan
- MRC Human Genetics Unit and Medical Genetics Section, Molecular Medicine Centre, Western General Hospital, Crewe Road, EH4 2XU, Edinburgh, UK.
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19
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Bourdon V, Philippe C, Grandemenge A, Reichwald K, Jonveaux P. Deletion screening by fluorescence in situ hybridization in Rett syndrome patients. ANNALES DE GENETIQUE 2001; 44:191-4. [PMID: 11755104 DOI: 10.1016/s0003-3995(01)01088-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene have been found to be a cause of Rett syndrome (RTT). Mutation screening was based on various techniques including denaturing gradient gel electrophoresis, single-strand conformation polymorphism analysis, heteroduplex analysis, DNA sequencing and recently Southern Blot analysis. Mutation detection was achieved in 80% of typical RTT with a high prevalence of recurrent mutations. In order to provide further insights into the spectrum of MECP2 rearrangements in patients without any point mutation or small deletion/insertion in the coding region MECP2 gene, we screened 25 classical RTT females using fluorescence in situ hybridization analysis. No deletion were found in our group, suggesting that MECP2 gross rearrangements are a rare cause of Rett syndrome.
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Affiliation(s)
- V Bourdon
- Laboratoire de génétique médicale, EA 3441, CHU Brabois, rue du Morvan, 54511 Vandoeuvre-les-Nancy cedex, France
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20
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Nicolao P, Carella M, Giometto B, Tavolato B, Cattin R, Giovannucci-Uzielli ML, Vacca M, Della Regione F, Piva S, Bortoluzzi S, Gasparini P. DHPLC analysis of the MECP2 gene in Italian Rett patients. Hum Mutat 2001; 18:132-40. [PMID: 11462237 DOI: 10.1002/humu.1162] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rett Syndrome (RTT) is an X-linked dominant neurodevelopmental disorder, which almost exclusively affects girls, with an estimated prevalence of one in 10,000-15,000 female births. Mutations in the methyl CpG binding protein 2 gene (MECP2) have been identified in roughly 75% of classical Rett girls. The vast majority of Rett cases (99%) are sporadic in origin, and are due to de novo mutations. We collected DNA samples from 50 Italian classical Rett girls, and screened the MECP2 coding region for mutations by denaturing high-performance liquid chromatography (DHPLC) and subsequent direct sequencing. DHPLC is a recently developed method for mutation screening which identifies heteroduplexes formed in DNA samples containing mismatches between wild type and mutant DNA strands, combining high sensitivity, reduced cost per run, and high throughput. In our series, 19 different de novo MECP2 mutations, eight of which were previously unreported, were found in 35 out of 50 Rett girls (70%). Seven recurrent mutations were characterized in a total of 22 unrelated cases. Initial DHPLC screening allowed the identification of 17 out of 19 different mutations (90%); after optimal conditions were established, this figure increased to 100%, with all recurrent MECP2 mutations generating a characteristic chromatographic profile. Detailed clinical data were available for 27 out of 35 mutation carrying Rett girls. Milder disease was detectable in patients carrying nonsense mutation as compared to patients carrying missense mutations, although this difference was not statistically significant (P = 0.077).
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Affiliation(s)
- P Nicolao
- Department of Neurological and Psychiatric Sciences, Second Neurological Clinic, Padua University, Padua, Italy.
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21
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Villard L, Lévy N, Xiang F, Kpebe A, Labelle V, Chevillard C, Zhang Z, Schwartz CE, Tardieu M, Chelly J, Anvret M, Fontès M. Segregation of a totally skewed pattern of X chromosome inactivation in four familial cases of Rett syndrome without MECP2 mutation: implications for the disease. J Med Genet 2001; 38:435-42. [PMID: 11432961 PMCID: PMC1757181 DOI: 10.1136/jmg.38.7.435] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Rett syndrome is a neurodevelopmental disorder affecting only girls; 99.5% of Rett syndrome cases are sporadic, although several familial cases have been reported. Mutations in the MECP2 gene were identified in approximately 70-80% of sporadic Rett syndrome cases. METHODS We have screened the MECP2 gene coding region for mutations in five familial cases of Rett syndrome and studied the patterns of X chromosome inactivation (XCI) in each girl. RESULTS We found a mutation in MECP2 in only one family. In the four families without mutation in MECP2, we found that (1) all mothers exhibit a totally skewed pattern of XCI; (2) six out of eight affected girls also have a totally skewed pattern of XCI; and (3) it is the paternally inherited X chromosome which is active in the patients with a skewed pattern of XCI. Given that the skewing of XCI is inherited in our families, we genotyped the whole X chromosome using 32 polymorphic markers and we show that a locus potentially responsible for the skewed XCI in these families could be located on the short arm of the X chromosome. CONCLUSION These data led us to propose a model for familial Rett syndrome transmission in which two traits are inherited, an X linked locus abnormally escaping X chromosome inactivation and the presence of a skewed XCI in carrier women.
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Affiliation(s)
- L Villard
- INSERM U491, Faculté de Médecine, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France
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22
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Amir RE, Zoghbi HY. Rett syndrome: methyl-CpG-binding protein 2 mutations and phenotype-genotype correlations. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 97:147-52. [PMID: 11180222 DOI: 10.1002/1096-8628(200022)97:2<147::aid-ajmg6>3.0.co;2-o] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder that manifests in females, typically after the first year of life. It is a leading cause of mental retardation and autistic behavior in girls and women; a hallmark of the disease is incessant hand movements in the form of wringing, twisting, or clapping. It was recently discovered that RTT is caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. MECP2 assists in the transcriptional silencing process via DNA methylation; we hypothesize that disruption of this gene alters the normal developmental expression of various other genes, some of which must account for the peculiar neurologic phenotype of RTT. Molecular studies have identified MECP2 mutations in up to 80% of classic RTT patients; mutation type has some effect on the phenotypic manifestation of RTT, but the pattern of X inactivation seems to determine phenotypic severity. Favorable (skewed) X inactivation can so spare a patient from the effects of mutant MECP2 that they display only the mildest learning disability or no phenotype at all. The unmitigated impact of mutant MECP2 can be inferred from the few males who have been born into RTT kindreds with such severe neonatal encephalopathy that they did not survive their second year. MECP2 mutations thus manifest in a far broader array of phenotypes than classic RTT. This discovery should prove helpful in diagnosing cases of mild learning disability or severe neonatal encephalopathies of unknown cause and also should provide insight into the pathogenesis of RTT.
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23
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Shahbazian MD, Zoghbi HY. Molecular genetics of Rett syndrome and clinical spectrum of MECP2 mutations. Curr Opin Neurol 2001; 14:171-6. [PMID: 11262731 DOI: 10.1097/00019052-200104000-00006] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rett syndrome, a neurodevelopmental disorder that is a leading cause of mental retardation in females, is caused by mutations in the X-linked gene encoding methyl-CpG-binding protein 2 (MeCP2). MECP2 mutations have subsequently been identified in patients with a variety of clinical syndromes ranging from mild learning disability in females to severe mental retardation, seizures, ataxia, and sometimes neonatal encephalopathy in males. In classic Rett syndrome, genotype-phenotype correlation studies suggest that X chromosome inactivation patterns have a more prominent effect on clinical severity than the type of mutation. When the full range of phenotypes associated with MECP2 mutations is considered, however, the mutation type strongly affects disease severity. MeCP2 is a transcriptional repressor that binds to methylated CpG dinucleotides throughout the genome, and mutations in Rett syndrome patients are thought to result in at least a partial loss of function. Abnormal gene expression may thus underlie the phenotype. Discovering which genes are misregulated in the absence of functional MeCP2 is crucial for understanding the pathogenesis of this disorder and related syndromes.
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Affiliation(s)
- M D Shahbazian
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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24
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Affiliation(s)
- T Webb
- Section of Medical and Molecular Genetics, Division of Reproductive and Child Health, University of Birmingham, Birmingham, UK
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25
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Rosenberg C, Wouters CH, Szuhai K, Dorland R, Pearson P, Poll-The BT, Colombijn RM, Breuning M, Lindhout D. A Rett syndrome patient with a ring X chromosome: further evidence for skewing of X inactivation and heterogeneity in the aetiology of the disease. Eur J Hum Genet 2001; 9:171-7. [PMID: 11313755 DOI: 10.1038/sj.ejhg.5200604] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/1999] [Revised: 11/06/2000] [Accepted: 11/14/2000] [Indexed: 11/09/2022] Open
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder, characterised by regression of development in young females. Recently, mutations in the MECP2 gene were found to be present in 80% of sporadic cases, but in much lower frequency (< 30%) among familial cases. Several reports claim that the pattern of X chromosome inactivation (XCI) relates to the penetrance of RTT; in some cases skewed XCI is seen in Rett patients, and in others it is observed among normal carriers. We present here a case of RTT with a 46,X,r(X) in which complete skewed inactivation of the ring was demonstrated. Further, no mutations were found in the MECP2 gene present on the intact X. Our data, in conjunction with two previously published cases of X chromosome abnormalities in RTT, indicate that X chromosome rearrangements are sporadically associated with RTT in conjunction with extreme skewing of X inactivation. Based on our case and reported data, we discuss the evidence for a second X-linked locus for RTT associated with lower penetrance, and a different pattern of XCI, than for MECP2. This would result in a larger proportion of phenotypically normal carrier women transmitting the mutation for this putative second locus, and account for the minority of sporadic and majority of familial cases that are negative for MECP2 mutations.
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Affiliation(s)
- C Rosenberg
- Laboratory of Cytochemistry and Cytometry, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands.
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26
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Abstract
The Rett syndrome (RS) is a peculiar, sporadic, atrophic disorder, almost entirely confined to females. After the first six months of life there is developmental slowing with reduced communication and head growth for about one year. This is followed by a rapid destructive stage with severe dementia and loss of hand skills (with frequent hand wringing), apraxia and ataxia, autistic features and irregular breathing with hyperventilation. Seizures often supervene. Subsequently there is some stabilization in a pseudo-stationary stage during the preschool to school years, associated with more emotional contact but also abnormalities of the autonomic and skeletal systems. After the age of 15-20 years, a late motor deterioration occurs with dystonia and frequent spasticity but seizures become milder. RS has generally been considered an X-linked disorder in which affected females represent a new mutation, with male lethality. Linkage studies suggested a critical region at Xq28. In 1999, mutations in the gene MECP2 encoding X-linked methyl cytosine-binding protein 2 (MeCP2) were found in a proportion of Rett girls. This protein can bind methylated DNA. Analyses are leading to much further investigation of mutants and their effects on genes. Neuropathological and electrophysiological studies of RS are described. Description of neurometabolic factors includes reduced levels of dopamine, serotonin, noradrenaline and choline acetyltransferase (ChAT) in brain, also estimation of nerve growth factors, endorphin, substance P, glutamate and other amino acids and their receptor levels. The results of neuroimaging are surveyed, including volumetric magnetic resonance imaging (MRI) and positron emission tomography (PET).
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Affiliation(s)
- H G Dunn
- Division of Neurology, British Columbia's Children's Hospital, Vancouver, BC, Canada
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27
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Leonard H, Fyfe S, Dye D, Hockey A, Christodoulou J. Family data in Rett syndrome: association with other genetic disorders. J Paediatr Child Health 2000; 36:336-9. [PMID: 10940166 DOI: 10.1046/j.1440-1754.2000.00531.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Rett syndrome is a neurological disorder, almost exclusively affecting girls. METHODOLOGY Between 1993 and 1995 pedigree data were obtained from families of girls registered with the Australian Rett syndrome database. RESULTS Although 21 individual disorders were reported to be present in family members of affected girls, there was no apparent clustering of the same disorder in different families. However it was certain that a geneticist had been involved in only 10.9% of cases. CONCLUSIONS Mutations in the MECP2 gene have now been reported in a proportion of sporadic cases. Thus, it will be important to examine this phenotype-genotype correlation in the Australian cohort. Where a mutation is found, prenatal diagnosis in a subsequent pregnancy will be a possibility. Using the Australian population database and in conjunction with the clinical genetic services in each state it is planned to contact families with an affected girl to offer testing and counselling.
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Affiliation(s)
- H Leonard
- TVW Telethon Institute for Child Health Research, West Perth, Australia.
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28
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Affiliation(s)
- P J Lombroso
- Child Study Center, Yale University School of Medicine, New Haven, CT 06520, USA.
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29
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Xiang F, Buervenich S, Nicolao P, Bailey ME, Zhang Z, Anvret M. Mutation screening in Rett syndrome patients. J Med Genet 2000; 37:250-5. [PMID: 10745042 PMCID: PMC1734556 DOI: 10.1136/jmg.37.4.250] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Rett syndrome (RTT) was first described in 1966. Its biological and genetic foundations were not clear until recently when Amir et al reported that mutations in the MECP2 gene were detected in around 50% of RTT patients. In this study, we have screened the MECP2 gene for mutations in our RTT material, including nine familial cases (19 Rett girls) and 59 sporadic cases. A total of 27 sporadic RTT patients were found to have mutations in the MECP2 gene, but no mutations were identified in our RTT families. In order to address the possibility of further X chromosomal or autosomal genetic factors in RTT, we evaluated six candidate genes for RTT selected on clinical, pathological, and genetic grounds: UBE1 (human ubiquitin activating enzyme E1, located in chromosome Xp11.23), UBE2I (ubiquitin conjugating enzyme E2I, homologous to yeast UBC9, chromosome 16p13.3), GdX (ubiquitin-like protein, chromosome Xq28), SOX3 (SRY related HMG box gene 3, chromosome Xq26-q27), GABRA3 (gamma-aminobutyric acid type A receptor alpha3 subunit, chromosome Xq28), and CDR2 (cerebellar degeneration related autoantigen 2, chromosome 16p12-p13.1). No mutations were detected in the coding regions of these six genes in 10 affected subjects and, therefore, alterations in the amino acid sequences of the encoded proteins can be excluded as having a causative role in RTT. Furthermore, gene expression of MECP2, GdX, GABRA3, and L1CAM (L1 cell adhesion molecule) was also investigated by in situ hybridisation. No gross differences were observed in neurones of several brain regions between normal controls and Rett patients.
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Affiliation(s)
- F Xiang
- Department of Clinical Neuroscience, Karolinska Hospital, Stockholm, Sweden.
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30
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Wan M, Lee SSJ, Zhang X, Houwink-Manville I, Song HR, Amir RE, Budden S, Naidu S, Pereira JLP, Lo IFM, Zoghbi HY, Schanen NC, Francke U. Rett syndrome and beyond: recurrent spontaneous and familial MECP2 mutations at CpG hotspots. Am J Hum Genet 1999; 65:1520-9. [PMID: 10577905 PMCID: PMC1288362 DOI: 10.1086/302690] [Citation(s) in RCA: 359] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/1999] [Accepted: 10/25/1999] [Indexed: 11/03/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder characterized by loss of acquired skills after a period of normal development in infant girls. The responsible gene, encoding methyl-CpG binding protein 2 (MeCP2), was recently discovered. Here we explore the spectrum of phenotypes resulting from MECP2 mutations. Both nonsense (R168X and R255X) and missense (R106W and R306C) mutations have been found, with multiple recurrences. R168X mutations were identified in six unrelated sporadic cases, as well as in two affected sisters and their normal mother. The missense mutations were de novo and affect conserved domains of MeCP2. All of the nucleotide substitutions involve C-->T transitions at CpG hotspots. A single nucleotide deletion, at codon 137, that creates a L138X stop codon within the methyl-binding domain was found in an individual with features of RTT and incontinentia pigmenti. An 806delG deletion causing a V288X stop in the transcription-repression domain was identified in a woman with motor-coordination problems, mild learning disability, and skewed X inactivation; in her sister and daughter, who were affected with classic RTT; and in her hemizygous son, who died from congenital encephalopathy. Thus, some males with RTT-causing MECP2 mutations may survive to birth, and female heterozygotes with favorably skewed X-inactivation patterns may have little or no involvement. Therefore, MECP2 mutations are not limited to RTT and may be implicated in a much broader phenotypic spectrum.
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Affiliation(s)
- Mimi Wan
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Stephen Sung Jae Lee
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Xianyu Zhang
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Isa Houwink-Manville
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Hae-Ri Song
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Ruthie E. Amir
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Sarojini Budden
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - SakkuBai Naidu
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Jose Luiz P. Pereira
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Ivan F. M. Lo
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Huda Y. Zoghbi
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - N. Carolyn Schanen
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
| | - Uta Francke
- Department
of Genetics and Howard Hughes Medical Institute, Stanford
University School of Medicine, Stanford, CA; Department of
Human Genetics, UCLA School of Medicine, Los Angeles; Child
Development and Rehabilitation Center, Oregon Health Science University,
Portland; Kennedy Krieger Institute, Johns Hopkins Medical
Institutions, Baltimore; Hospital General do Portao, and
Department of Psychiatry, Federal University of Parana,
Curitiba, Parana, Brazil; Clinical Genetic Service,
Department of Health, Hong Kong; and Departments of
Pediatrics and Molecular and Human Genetics
and Howard Hughes Medical Institute, Baylor College of
Medicine, Houston
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