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MeCP2 and transcriptional control of eukaryotic gene expression. Eur J Cell Biol 2022; 101:151237. [DOI: 10.1016/j.ejcb.2022.151237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 04/30/2022] [Accepted: 05/09/2022] [Indexed: 11/19/2022] Open
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Differential Sensitivity of the Protein Translation Initiation Machinery and mTOR Signaling to MECP2 Gain- and Loss-of-Function Involves MeCP2 Isoform-Specific Homeostasis in the Brain. Cells 2022; 11:cells11091442. [PMID: 35563748 PMCID: PMC9105805 DOI: 10.3390/cells11091442] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/15/2022] [Accepted: 04/19/2022] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic gene expression is controlled at multiple levels, including gene transcription and protein translation initiation. One molecule with key roles in both regulatory mechanisms is methyl CpG binding protein 2 (MeCP2). MECP2 gain- and loss-of-function mutations lead to Rett Syndrome and MECP2 Duplication Syndrome, respectively. To study MECP2 gain-of-function, we generated stably transduced human brain cells using lentiviral vectors for both MECP2E1 and MECP2E2 isoforms. Stable overexpression was confirmed by Western blot and immunofluorescence. We assessed the impact of MeCP2E1-E2 gain-of-function on the MeCP2 homeostasis regulatory network (MECP2E1/E2-BDNF/BDNF-miR-132), mTOR-AKT signaling, ribosome biogenesis, markers of chromatin structure, and protein translation initiation. We observed that combined co-transduction of MeCP2 isoforms led to protein degradation of MeCP2E1. Proteosome inhibition by MG132 treatment recovered MeCP2E1 protein within an hour, suggesting its induced degradation through the proteosome pathway. No significant change was detected for translation initiation factors as a result of MeCP2E1, MeCP2E2, or combined overexpression of both isoforms. In contrast, analysis of human Rett Syndrome brains tissues compared with controls indicated impaired protein translation initiation, suggesting that such mechanisms may have differential sensitivity to MECP2 gain- and loss-of-function. Collectively, our results provide further insight towards the dose-dependent functional role of MeCP2 isoforms in the human brain.
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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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Abstract
Objectives Rett syndrome is a rare disorder characterised by severe scoliosis in 80% of cases. In this retrospective case series, we analysed the radiographic, clinical, and functional outcomes of consecutive patients treated for scoliosis associated with Rett syndrome. We sought to understand the results of the treatment of scoliosis in Rett syndrome and evaluate the need to fuse to the pelvis. Methods A retrospective case series was used to analyse the radiographic, clinical, and functional outcomes of consecutive patients treated for Rett syndrome scoliosis between the ages of 10 and 8 years in a single tertiary paediatric spinal unit. Cases were identified through departmental and neurophysiological records, and patients were excluded if the diagnosis of Rett syndrome was not confirmed. Results Seven eligible cases were identified. At presentation, the mean coronal Cobb angle was 90.9°, mean sagittal Cobb 72.0°, and pelvic obliquity 24.5°. The mean post-operative improvement in coronal Cobb was 53.2° and pelvic obliquity reduced to 5.8°. These did not change during a mean follow up of 3.5 years. None showed any post-operative complications. Three patients with a mean 16.1° pelvic obliquity underwent a fusion to L5. The postoperative result in those cases remained stable at 3.5 years mean follow-up and full skeletal maturity. Conclusion Our data suggests that with modern technology, severe curves can be safely treated. Fusion to the pelvis is not necessary in patients with mild, flexible pelvic obliquity.
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Affiliation(s)
- Brett Rocos
- Department of Orthopaedic Surgery, Hospital for Sick Children, Toronto, CAN
| | - Reinhard Zeller
- Department of Orthopaedic Surgery, Hospital for Sick Children, Toronto, CAN
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D'Mello SR. MECP2 and the Biology of MECP2 Duplication Syndrome. J Neurochem 2021; 159:29-60. [PMID: 33638179 DOI: 10.1111/jnc.15331] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/21/2021] [Accepted: 02/18/2021] [Indexed: 11/27/2022]
Abstract
MECP2 duplication syndrome (MDS), a rare X-linked genomic disorder affecting predominantly males, is caused by duplication of the chromosomal region containing the methyl CpG binding protein-2 (MECP2) gene, which encodes methyl-CpG-binding protein 2 (MECP2), a multi-functional protein required for proper brain development and maintenance of brain function during adulthood. Disease symptoms include severe motor and cognitive impairment, delayed or absent speech development, autistic features, seizures, ataxia, recurrent respiratory infections and shortened lifespan. The cellular and molecular mechanisms by which a relatively modest increase in MECP2 protein causes such severe disease symptoms are poorly understood and consequently there are no treatments available for this fatal disorder. This review summarizes what is known to date about the structure and complex regulation of MECP2 and its many functions in the developing and adult brain. Additionally, recent experimental findings on the cellular and molecular underpinnings of MDS based on cell culture and mouse models of the disorder are reviewed. The emerging picture from these studies is that MDS is a neurodegenerative disorder in which neurons die in specific parts of the central nervous system, including the cortex, hippocampus, cerebellum and spinal cord. Neuronal death likely results from astrocytic dysfunction, including a breakdown of glutamate homeostatic mechanisms. The role of elevations in the expression of glial acidic fibrillary protein (GFAP) in astrocytes and the microtubule-associated protein, Tau, in neurons to the pathogenesis of MDS is discussed. Lastly, potential therapeutic strategies to potentially treat MDS are discussed.
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Abstract
Elucidating the functions of a particular gene is paramount to the understanding of how its dysfunction contributes to disease. This is especially important when the gene is implicated in multiple different disorders. One such gene is methyl-CpG-binding protein 2 (MECP2), which has been most prominently associated with the neurodevelopmental disorder Rett syndrome, as well as major neuropsychiatric disorders such as autism and schizophrenia. Being initially identified as a transcriptional regulator that modulates gene expression and subsequently also shown to be involved in other molecular events, dysfunction of the MeCP2 protein has the potential to affect many cellular processes. In this chapter, we will briefly review the functions of the MeCP2 protein and how its mutations are implicated in Rett syndrome and other neuropsychiatric disorders. We will further discuss about the mouse models that have been generated to specifically dissect the function of MeCP2 in different cell types and brain regions. It is envisioned that such thorough and targeted examination of MeCP2 functions can aid in enlightening the role that it plays in normal and dysfunctional physiological systems.
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Affiliation(s)
- Eunice W M Chin
- Neuroscience and Mental Health Faculty, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Eyleen L K Goh
- Neuroscience and Mental Health Faculty, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.
- Department of Research, National Neuroscience Institute, Singapore, Singapore.
- Neuroscience Academic Clinical Programme, Singhealth Duke-NUS Academic Medical Center, Singapore, Singapore.
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NASIRI J, SALEHI M, HOSSEINZADEH M, ZAMANI M, FATTAHPOUR S, ARYANI O, FAZEL NAJAFABADI E, JABARZADEH M, ASADI S, GHOLAMREZAPOUR T, SEDGHI M, GHORBANI F. Genetic Analysis of MECP2 Gene in Iranian Patients with Rett Syndrome. IRANIAN JOURNAL OF CHILD NEUROLOGY 2019; 13:25-34. [PMID: 31327966 PMCID: PMC6586453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 11/29/2017] [Accepted: 12/19/2017] [Indexed: 11/06/2022]
Abstract
OBJECTIVES Rett syndrome is an X linked dominant neurodevelopmental disorder which almost exclusively affects females. The syndrome is usually caused by mutations in MECP2 gene, which is a nuclear protein that selectively binds CpG dinucleotides in the genome. MATERIALS & METHODS To provide further insights into the distribution of mutations in MECP2 gene, we investigated 24 females with clinical characters of Rett syndrome referred to Alzahra University Hospital in Isfahan, Iran during 2015-2017. We sequenced the entire MECP2 coding region and splice sites for detection of point mutations in this gene. Freely available programs including JALVIEW, SIFT, and PolyPhen were used to find out the damaging effects of unknown mutations. RESULTS Direct sequencing revealed MECP2 mutations in 13 of the 24 patients. We identified in 13 patients, 10 different mutations in MECP2 gene. Three of these mutations have not been reported elsewhere and are most likely pathogenic. CONCLUSION Defects in MECP2 gene play an important role in pathogenesis of Rett syndrome. Mutations in MECP2 gene can be found in the majority of Iranian RTT patients. We failed to identify mutations in MECP2 gene in 46% of our patients. For these patients, further molecular analysis might be necessary.
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Affiliation(s)
- Jafar NASIRI
- Department of Paediatric Neurology, Faculty of Medicine, Child Growth and Development Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mansoor SALEHI
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Majid HOSSEINZADEH
- Department of Medical Genetics, School of Medicine, International Campus, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahdi ZAMANI
- Department of Medical Genetics, School of Medicine, International Campus, Tehran University of Medical Sciences, Tehran, Iran
| | - Shirin FATTAHPOUR
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Omid ARYANI
- Department of Neuroscience, Iran University of Medical Sciences, Tehran, Iran
| | - Esmat FAZEL NAJAFABADI
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Maryam JABARZADEH
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Sara ASADI
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Tahereh GHOLAMREZAPOUR
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Maryam SEDGHI
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Fatemeh GHORBANI
- Medical Genetics Laboratory, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
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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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Tsuchiya Y, Minami Y, Umemura Y, Watanabe H, Ono D, Nakamura W, Takahashi T, Honma S, Kondoh G, Matsuishi T, Yagita K. Disruption of MeCP2 attenuates circadian rhythm in CRISPR/Cas9-based Rett syndrome model mouse. Genes Cells 2015; 20:992-1005. [DOI: 10.1111/gtc.12305] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 08/23/2015] [Indexed: 02/01/2023]
Affiliation(s)
- Yoshiki Tsuchiya
- Department of Physiology and Systems Bioscience; Kyoto Prefectural University of Medicine; Kyoto 602-8566 Japan
| | - Yoichi Minami
- Department of Physiology and Systems Bioscience; Kyoto Prefectural University of Medicine; Kyoto 602-8566 Japan
| | - Yasuhiro Umemura
- Department of Physiology and Systems Bioscience; Kyoto Prefectural University of Medicine; Kyoto 602-8566 Japan
| | - Hitomi Watanabe
- Laboratory of Animal Experiments for Regeneration; Institute for Frontier Medical Sciences; Kyoto University; Kyoto 606-8507 Japan
| | - Daisuke Ono
- Department of Chronomedicine; Hokkaido University Graduate School of Medicine; Sapporo 060-8638 Japan
| | - Wataru Nakamura
- Laboratory of Oral Chronobiology; Graduate School of Dentistry; Osaka University; Suita Osaka 565-0871 Japan
| | - Tomoyuki Takahashi
- Department of Pediatrics and Child Health; Kurume University School of Medicine; Kurume 830-0011 Japan
| | - Sato Honma
- Department of Chronomedicine; Hokkaido University Graduate School of Medicine; Sapporo 060-8638 Japan
| | - Gen Kondoh
- Laboratory of Animal Experiments for Regeneration; Institute for Frontier Medical Sciences; Kyoto University; Kyoto 606-8507 Japan
| | - Toyojiro Matsuishi
- Department of Pediatrics and Child Health; Kurume University School of Medicine; Kurume 830-0011 Japan
| | - Kazuhiro Yagita
- Department of Physiology and Systems Bioscience; Kyoto Prefectural University of Medicine; Kyoto 602-8566 Japan
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Gold WA, Christodoulou J. The Utility of Next-Generation Sequencing in Gene Discovery for Mutation-Negative Patients with Rett Syndrome. Front Cell Neurosci 2015; 9:266. [PMID: 26236194 PMCID: PMC4500929 DOI: 10.3389/fncel.2015.00266] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 06/29/2015] [Indexed: 01/13/2023] Open
Abstract
Rett syndrome (RTT) is a rare, severe disorder of neuronal plasticity that predominantly affects girls. Girls with RTT usually appear asymptomatic in the first 6–18 months of life, but gradually develop severe motor, cognitive, and behavioral abnormalities that persist for life. A predominance of neuronal and synaptic dysfunction, with altered excitatory–inhibitory neuronal synaptic transmission and synaptic plasticity, are overarching features of RTT in children and in mouse models. Over 90% of patients with classical RTT have mutations in the X-linked methyl-CpG-binding (MECP2) gene, while other genes, including cyclin-dependent kinase-like 5 (CDKL5), Forkhead box protein G1 (FOXG1), myocyte-specific enhancer factor 2C (MEF2C), and transcription factor 4 (TCF4), have been associated with phenotypes overlapping with RTT. However, there remain a proportion of patients who carry a clinical diagnosis of RTT, but who are mutation negative. In recent years, next-generation sequencing technologies have revolutionized approaches to genetic studies, making whole-exome and even whole-genome sequencing possible strategies for the detection of rare and de novo mutations, aiding the discovery of novel disease genes. Here, we review the recent progress that is emerging in identifying pathogenic variations, specifically from exome sequencing in RTT patients, and emphasize the need for the use of this technology to identify known and new disease genes in RTT patients.
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Affiliation(s)
- Wendy Anne Gold
- Western Sydney Genetics Program, New South Wales Centre for Rett Syndrome Research, Children's Hospital at Westmead , Sydney, NSW , Australia ; Discipline of Paediatrics and Child Health, University of Sydney , Sydney, NSW , Australia
| | - John Christodoulou
- Western Sydney Genetics Program, New South Wales Centre for Rett Syndrome Research, Children's Hospital at Westmead , Sydney, NSW , Australia ; Discipline of Paediatrics and Child Health, University of Sydney , Sydney, NSW , Australia ; Discipline of Genetic Medicine, Sydney Medical School, University of Sydney , Sydney, NSW , Australia
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Abstract
Rett syndrome (RTT) is a severe and progressive neurological disorder, which mainly affects young females. Mutations of the methyl-CpG binding protein 2 (MECP2) gene are the most prevalent cause of classical RTT cases. MECP2 mutations or altered expression are also associated with a spectrum of neurodevelopmental disorders such as autism spectrum disorders with recent links to fetal alcohol spectrum disorders. Collectively, MeCP2 relation to these neurodevelopmental disorders highlights the importance of understanding the molecular mechanisms by which MeCP2 impacts brain development, mental conditions, and compromised brain function. Since MECP2 mutations were discovered to be the primary cause of RTT, a significant progress has been made in the MeCP2 research, with respect to the expression, function and regulation of MeCP2 in the brain and its contribution in RTT pathogenesis. To date, there have been intensive efforts in designing effective therapeutic strategies for RTT benefiting from mouse models and cells collected from RTT patients. Despite significant progress in MeCP2 research over the last few decades, there is still a knowledge gap between the in vitro and in vivo research findings and translating these findings into effective therapeutic interventions in human RTT patients. In this review, we will provide a synopsis of Rett syndrome as a severe neurological disorder and will discuss the role of MeCP2 in RTT pathophysiology.
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Yasui DH, Gonzales ML, Aflatooni JO, Crary FK, Hu DJ, Gavino BJ, Golub MS, Vincent JB, Carolyn Schanen N, Olson CO, Rastegar M, Lasalle JM. Mice with an isoform-ablating Mecp2 exon 1 mutation recapitulate the neurologic deficits of Rett syndrome. Hum Mol Genet 2013; 23:2447-58. [PMID: 24352790 DOI: 10.1093/hmg/ddt640] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutations in MECP2 cause the neurodevelopmental disorder Rett syndrome (RTT OMIM 312750). Alternative inclusion of MECP2/Mecp2 exon 1 with exons 3 and 4 encodes MeCP2-e1 or MeCP2-e2 protein isoforms with unique amino termini. While most MECP2 mutations are located in exons 3 and 4 thus affecting both isoforms, MECP2 exon 1 mutations but not exon 2 mutations have been identified in RTT patients, suggesting that MeCP2-e1 deficiency is sufficient to cause RTT. As expected, genetic deletion of Mecp2 exons 3 and/or 4 recapitulates RTT-like neurologic defects in mice. However, Mecp2 exon 2 knockout mice have normal neurologic function. Here, a naturally occurring MECP2 exon 1 mutation is recapitulated in a mouse model by genetic engineering. A point mutation in the translational start codon of Mecp2 exon 1, transmitted through the germline, ablates MeCP2-e1 translation while preserving MeCP2-e2 production in mouse brain. The resulting MeCP2-e1 deficient mice developed forelimb stereotypy, hindlimb clasping, excessive grooming and hypo-activity prior to death between 7 and 31 weeks. MeCP2-e1 deficient mice also exhibited abnormal anxiety, sociability and ambulation. Despite MeCP2-e1 and MeCP2-e2 sharing, 96% amino acid identity, differences were identified. A fraction of phosphorylated MeCP2-e1 differed from the bulk of MeCP2 in subnuclear localization and co-factor interaction. Furthermore, MeCP2-e1 exhibited enhanced stability compared with MeCP2-e2 in neurons. Therefore, MeCP2-e1 deficient mice implicate MeCP2-e1 as the sole contributor to RTT with non-redundant functions.
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Affiliation(s)
- Dag H Yasui
- Department of Medical Microbiology and Immunology, UC Davis, Davis, CA, USA
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Ellaway CJ, Ho G, Bettella E, Knapman A, Collins F, Hackett A, McKenzie F, Darmanian A, Peters GB, Fagan K, Christodoulou J. 14q12 microdeletions excluding FOXG1 give rise to a congenital variant Rett syndrome-like phenotype. Eur J Hum Genet 2012; 21:522-7. [PMID: 22968132 DOI: 10.1038/ejhg.2012.208] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Rett syndrome is a clinically defined neurodevelopmental disorder almost exclusively affecting females. Usually sporadic, Rett syndrome is caused by mutations in the X-linked MECP2 gene in ∼90-95% of classic cases and 40-60% of individuals with atypical Rett syndrome. Mutations in the CDKL5 gene have been associated with the early-onset seizure variant of Rett syndrome and mutations in FOXG1 have been associated with the congenital Rett syndrome variant. We report the clinical features and array CGH findings of three atypical Rett syndrome patients who had severe intellectual impairment, early-onset developmental delay, postnatal microcephaly and hypotonia. In addition, the females had a seizure disorder, agenesis of the corpus callosum and subtle dysmorphism. All three were found to have an interstitial deletion of 14q12. The deleted region in common included the PRKD1 gene but not the FOXG1 gene. Gene expression analysis suggested a decrease in FOXG1 levels in two of the patients. Screening of 32 atypical Rett syndrome patients did not identify any pathogenic mutations in the PRKD1 gene, although a previously reported frameshift mutation affecting FOXG1 (c.256dupC, p.Gln86ProfsX35) was identified in a patient with the congenital Rett syndrome variant. There is phenotypic overlap between congenital Rett syndrome variants with FOXG1 mutations and the clinical presentation of our three patients with this 14q12 microdeletion, not encompassing the FOXG1 gene. We propose that the primary defect in these patients is misregulation of the FOXG1 gene rather than a primary abnormality of PRKD1.
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Affiliation(s)
- Carolyn J Ellaway
- Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia.
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Fendri-Kriaa N, Rouissi A, Ghorbel R, Mkaouar-Rebai E, Belguith N, Gouider-Khouja N, Fakhfakh F. Novel double deletions in the MECP2 gene in Tunisian Rett patient. Gene 2012; 502:163-7. [PMID: 22561697 DOI: 10.1016/j.gene.2012.04.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 03/29/2012] [Accepted: 04/09/2012] [Indexed: 11/26/2022]
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder affecting almost exclusively girls. Rett patients present an apparently normal psychomotor development during the first 6-18 months of life. Thereafter, they show a short period of developmental stagnation followed by a rapid regression in language and motor development. RTT is currently considered as monogenic X-linked dominant disorder due to mutations in the MECP2 gene, encoding the methyl-CpG binding protein 2. The aim of this study was to perform a mutational analysis of the MECP2 gene in a classical Rett patient.The results showed the presence of a novel point mutation c.C1142T (p.P381L) and two deletions at the heterozygous state: a novel deletion c.1075delTTC (p.S359) and a known one c.1157del44 (p.L386Q fs X2) in the C-terminal region of MeCP2.
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Affiliation(s)
- Nourhene Fendri-Kriaa
- Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax, Tunisia.
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Fendri-Kriaa N, Rouissi A, Ghorbel R, Mkaouar-Rebai E, Belguith N, Gouider-Khouja N, Fakhfakh F. Novel mutations in the C-terminal region of the MECP2 gene in Tunisian Rett syndrome patients. J Child Neurol 2012; 27:564-8. [PMID: 21940684 DOI: 10.1177/0883073811420496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Rett syndrome (RTT), an X-linked dominant neurodevelopmental disorder in females, is caused mainly by de novo mutations in the methyl-CpG-binding protein 2 gene (MECP2). Rett patients present an apparently normal psychomotor development during the first 6 to 18 months of life. Thereafter, they show a short period of developmental stagnation followed by a rapid regression in language and motor development. In the present study, we performed a mutational analysis of the MECP2 gene in 2 typical Rett syndrome patients and in 1 atypical Rett syndrome girl. The results showed the presence of 3 de novo point mutations in the C-terminal region: 2 novel mutations: c.1065C>A (p.S355R) and c.1030C>G (p.R344G) in the 2 typical Rett syndrome girls, but also the c.996C>T (p.S332S) mutation first described in the atypical Rett syndrome patient.
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Affiliation(s)
- Nourhene Fendri-Kriaa
- Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax, Tunisia.
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Corbani S, Chouery E, Fayyad J, Fawaz A, El Tourjuman O, Badens C, Lacoste C, Delague V, Megarbane A. Molecular screening of MECP2 gene in a cohort of Lebanese patients suspected with Rett syndrome: report on a mild case with a novel indel mutation. JOURNAL OF INTELLECTUAL DISABILITY RESEARCH : JIDR 2012; 56:415-420. [PMID: 21954873 DOI: 10.1111/j.1365-2788.2011.01479.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND Rett syndrome (RTT), an X-linked, dominant, neurodevelopment disorder represents 10% of female subjects with profound intellectual disability. Mutations in the MECP2 gene are responsible for up to 95% of the classical RTT cases, and nearly 500 different mutations distributed throughout the gene have been reported. METHODS We report here the molecular study of two isoforms, MECP2_e1 and MECP2_e2, in 45 Lebanese girls presenting developmental delay and at least one of the following features: microcephaly, neurodegeneration, abnormal behaviour, stereotypical hand movements, teeth grinding and difficulty in walking. Mutation screening was performed by denaturating high-performance liquid chromatography combined with direct sequencing. RESULTS Sixteen variants were noted, of which 14 have been previously reported: five suspected polymorphisms and nine mutations. Two variants were novel mutations in exon 4: c.1093_1095delGAG (p.E365del) and c.1164_1184delACCTCCACCTGAGCCCGAGAGinsCTGAGCCCCAGGACTTGAGCA (p.P388PfsX389). The deletion was found in an 8-year-old girl with typical clinical features of RTT. The indel was found in a 6-year-old girl with a very mild phenotype. CONCLUSION Genotype/phenotype correlation is discussed and the importance of a molecular study of MECP2 gene in patients with very mild features or a regression after the age of 2 is raised.
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Affiliation(s)
- S Corbani
- Unité de Génétique Médicale et laboratoire associé INSERM à l'Unité UMR_S910, Université Saint-Joseph, Beirut, Lebanon
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17
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Tsai KN, Chen GW, Chen CYC. A Novel Algorithm for Identification of Activated Cryptic 5′ Splice Sites. J Biomol Struct Dyn 2012; 29:1089-99. [DOI: 10.1080/073911012010525033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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18
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Armani R, Archer H, Clarke A, Vasudevan P, Zweier C, Ho G, Williamson S, Cloosterman D, Yang N, Christodoulou J. Transcription factor 4 and myocyte enhancer factor 2C mutations are not common causes of Rett syndrome. Am J Med Genet A 2012; 158A:713-9. [PMID: 22383159 DOI: 10.1002/ajmg.a.34206] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/22/2011] [Indexed: 01/04/2023]
Abstract
The systematic screening of Rett syndrome (RTT) patients for pathogenetic sequence variations has focused on three genes that have been associated with RTT or related clinical phenotypes, namely MECP2, CDKL5, and FOXG1. More recently, it has been suggested that phenotypes associated with TCF4 and MEF2C mutations may represent a form of RTT. Here we report on the screening of the TCF4 and MEF2C genes in a cohort of 81 classical, atypical, and incomplete atypical RTT patients harboring no known mutations in MECP2, CDKL5, and FOXG1 genes. No pathogenetic sequence variations were identified in the MEF2C gene in our cohort. However, a frameshift mutation in TCF4 was identified in a patient with a clinical diagnosis of "variant" RTT, in whom the clinical evolution later raised the possibility of Pitt-Hopkins syndrome. Although our results suggest that these genes are not commonly associated with RTT, we note the clinical similarity between RTT and Pitt-Hopkins syndrome, and suggest that RTT patients with no mutation identified in MECP2 be considered for molecular screening of the TCF4 gene.
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Affiliation(s)
- Roksana Armani
- NSW Centre for Rett Syndrome Research, Kids Research Institute, The Children's Hospital at Westmead, Sydney, NSW, Australia
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19
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Gianakopoulos PJ, Zhang Y, Pencea N, Orlic-Milacic M, Mittal K, Windpassinger C, White SJ, Kroisel PM, Chow EWC, Saunders CJ, Minassian BA, Vincent JB. Mutations in MECP2 exon 1 in classical Rett patients disrupt MECP2_e1 transcription, but not transcription of MECP2_e2. Am J Med Genet B Neuropsychiatr Genet 2012; 159B:210-6. [PMID: 22213695 DOI: 10.1002/ajmg.b.32015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 12/05/2011] [Indexed: 11/07/2022]
Abstract
The overwhelming majority of Rett syndrome cases are caused by mutations in the gene MECP2. MECP2 has two isoforms, termed MECP2_e1 and MECP2_e2, which differ in their N-terminal amino acid sequences. A growing body of evidence has indicated that MECP2_e1 may be the etiologically relevant isoform in Rett Syndrome based on its expression profile in the brain and because, strikingly, no mutations have been discovered that affect MECP2_e2 exclusively. In this study we sought to characterize four classical Rett patients with mutations that putatively affect only the MECP2_e1 isoform. Our hypothesis was that the classical Rett phenotype seen here is the result of disrupted MECP2_e1 expression, but with MECP2_e2 expression unaltered. We used quantitative reverse transcriptase PCR to assay mRNA expression for each isoform independently, and used cytospinning methods to assay total MECP2 in peripheral blood lymphocytes (PBL). In the two Rett patients with identical 11 bp deletions within the coding portion of exon 1, MECP2_e2 levels were unaffected, whilst a significant reduction of MECP2_e1 levels was detected. In two Rett patients harboring mutations in the exon 1 start codon, MECP2_e1 and MECP2_e2 mRNA amounts were unaffected. In summary, we have shown that patients with exon 1 mutations transcribe normal levels of MECP2_e2 mRNA, and most PBL are positive for MeCP2 protein, despite them theoretically being unable to produce the MECP2_e1 isoform, and yet still exhibit the classical RTT phenotype. Altogether, our work further supports our hypothesis that MECP2_e1 is the predominant isoform involved in the neuropathology of Rett syndrome.
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Affiliation(s)
- Peter J Gianakopoulos
- Molecular Neuropsychiatry and Development Lab, Neurogenetics Section, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
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20
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Fehr S, Bebbington A, Nassar N, Downs J, Ronen GM, DE Klerk N, Leonard H. Trends in the diagnosis of Rett syndrome in Australia. Pediatr Res 2011; 70:313-9. [PMID: 21587099 PMCID: PMC3152673 DOI: 10.1203/pdr.0b013e3182242461] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Modifications to diagnostic criteria and introduction of genetic testing have likely affected the pattern and timing of Rett syndrome diagnosis. The trends in incidence and prevalence of Rett syndrome in Australia were examined; the cumulative risk of a female being diagnosed was determined; and the impact of changes to diagnostic criteria and availability of genetic testing on these frequencies was investigated. The population-based Australian Rett Syndrome Database was used to identify a total of 349 verified Rett syndrome females born 1976-2006 and diagnosed 1982-2008. The proportion of female cases born and diagnosed per year and the cumulative risk of a diagnosis were determined. The median age of Rett syndrome diagnosis decreased from 4.5 y if diagnosed before 2000 to 3.5 y if diagnosed after 1999. The cumulative risk of diagnosis had almost doubled by 32 y of age [1/8,905 or 11.23 per 100,000 person-years (95% CI, 10.03-12.45)] in comparison with 5 y of age [1/15,361 or 6.51 per 100,000 person-years (95% CI, 5.65-7.39)]. Earlier age of diagnosis may result in families experiencing less stress and emotional strain compared with those with delayed diagnosis.
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Affiliation(s)
- Stephanie Fehr
- Centre for Child Health Research, The University of Western Australia, Perth, Western Australia 6008, Australia
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21
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Kerr B, Soto C J, Saez M, Abrams A, Walz K, Young JI. Transgenic complementation of MeCP2 deficiency: phenotypic rescue of Mecp2-null mice by isoform-specific transgenes. Eur J Hum Genet 2011; 20:69-76. [PMID: 21829232 DOI: 10.1038/ejhg.2011.145] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rett syndrome (RTT) is a disorder that affects patients' ability to communicate, move and behave. RTT patients are characterized by impaired language, stereotypic behaviors, frequent seizures, ataxia and sleep disturbances, with the onset of symptoms occurring after a period of seemingly normal development. RTT is caused by mutations in methyl-CpG binding protein 2 (MECP2), an X-chromosome gene encoding for MeCP2, a protein that regulates gene expression. MECP2 generates two alternative splice variants encoding two protein isoforms that differ only in the N-terminus. Although no functional differences have been identified for these splice variants, it has been suggested that the RTT phenotype may occur in the presence of a functional MeCP2-e2 protein. This suggests that the two isoforms might be functionally distinct. Supporting this notion, the two variants show regional and age-related differences in transcript abundance. Here, we show that transgenic expression of either the MeCP2-e1 or MeCP2-e2 splice variant results in prevention of development of RTT-like phenotypic manifestations in a mouse model lacking Mecp2. Our results indicate that the two MeCP2 splice variants can substitute for each other and fulfill the basic functions of MeCP2 in the mouse brain.
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Affiliation(s)
- Bredford Kerr
- Department of Biology, Centro de Estudios Científicos, Valdivia, Chile
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22
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Colak D, Al-Dhalaan H, Nester M, Albakheet A, Al-Younes B, Al-Hassnan Z, Al-Dosari M, Chedrawi A, Al-Owain M, Abudheim N, Al-Alwan L, Al-Odaib A, Ozand P, Inan MS, Kaya N. Genomic and transcriptomic analyses distinguish classic Rett and Rett-like syndrome and reveals shared altered pathways. Genomics 2010; 97:19-28. [PMID: 20934504 DOI: 10.1016/j.ygeno.2010.09.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 09/20/2010] [Accepted: 09/24/2010] [Indexed: 11/24/2022]
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder characterized by derangements in nervous system especially in cognition and behavior. The present study aims to understand the molecular underpinnings of two subtypes of RTT, classic RTT and Rett-like, and to elucidate common pathways giving rise to common RTT phenotype using genomic and transcriptomic approaches. Mutation screening on selected nuclear genes revealed only MECP2 mutations in a subset of classic RTT patients. MLPA assays and mtDNA screenings were all negative. Genome-wide copy number analysis indicated a novel duplication on X chromosome. Transcriptional profiling revealed blood gene signatures that clearly distinguish classic RTT and RTT-like patients, as well as shared altered pathways in interleukin-4 and NF-κB signaling pathways in both subtypes of the syndrome. To our knowledge, this is the first report on investigating common regulatory mechanisms/signaling pathways that may be relevant to the pathobiology of the "common RTT" phenotype.
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Affiliation(s)
- Dilek Colak
- Department of Biostatistics, Epidemiology and Scientific Computing, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
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23
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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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24
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Downs J, Bergman A, Carter P, Anderson A, Palmer GM, Roye D, van Bosse H, Bebbington A, Larsson EL, Smith BG, Baikie G, Fyfe S, Leonard H. Guidelines for management of scoliosis in Rett syndrome patients based on expert consensus and clinical evidence. Spine (Phila Pa 1976) 2009; 34:E607-17. [PMID: 19644320 DOI: 10.1097/brs.0b013e3181a95ca4] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Modified Delphi technique. OBJECTIVE To develop guidelines for the clinical management of scoliosis in Rett syndrome through evidence review and consensus expert panel opinion. SUMMARY OF BACKGROUND DATA Rett syndrome is a rare disorder and clinical expertise is thus with small case series. Scoliosis is a frequent association and the evidence base dealing with scoliosis management in this syndrome is limited. Parents of affected girls and women have expressed needs for more information about scoliosis and Rett syndrome. METHODS An initial draft of scoliosis guidelines was created based on literature review and open-ended questions where the literature was lacking. Perspectives of four parents of Rett syndrome patients informed this initial draft. Access to an online and a Microsoft Word formatted version of the draft were then sent to an international, multidisciplinary panel of clinicians via e-mail with input sought using a 2-stage modified Delphi process to reach consensus agreement. Items included clinical monitoring and intervention before the diagnosis of scoliosis; monitoring after the diagnosis of scoliosis; imaging; therapy and conservative management; bracing; and preoperative, surgical, and postoperative considerations. RESULTS The first draft contained 71 statements, 65 questions. The second draft comprised 88 items with agreement to strong agreement achieved on 85, to form the final guideline document. A comprehensive, life-span approach to the management of scoliosis in Rett syndrome is recommended that takes into account factors such as physical activity, posture, nutritional and bone health needs. Surgery should be considered when the Cobb angle is approximately 40 degrees to 50 degrees and must be supported by specialist management of anesthesia, pain control, seizures, and early mobilization. CONCLUSION Evidence- and consensus-based guidelines were successfully created and have the potential to improve care of a complex comorbidity in a rare condition and stimulate research to improve the current limited evidence base.
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Affiliation(s)
- Jenny Downs
- Centre for Child Health Research, Telethon Institute for Child Health Research, Perth, Australia
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25
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Saunders CJ, Minassian BE, Chow EWC, Zhao W, Vincent JB. Novel exon 1 mutations in MECP2 implicate isoform MeCP2_e1 in classical Rett syndrome. Am J Med Genet A 2009; 149A:1019-23. [PMID: 19365833 DOI: 10.1002/ajmg.a.32776] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene. Recently, a new MeCP2 isoform was described, MeCP2_e1, which skips exon 2 and has an alternative N-terminus, translated from exon 1, whereas MeCP2_e2 is translated from a start codon in exon 2. Since the incorporation of exon 1 into standard sequencing protocols for RTT, few exon 1 mutations have been described and are thus assumed to be only rare causes of RTT. Also, studies have suggested that the frameshift mutations identified in exon 1 affect both isoforms. Our aim in this study was to assess the frequency of mutations in exon 1, their relationship to phenotype, and the implications on the etiological role for the isoform MeCP2_e1 in RTT, versus the previously described isoform, MeCP2_e2. We sequenced MECP2 in 51 females with various clinical presentations, including developmental delay, autism, atypical and classical RTT, referred to our laboratories for testing. In patients with identified mutations, X-chromosome inactivation was analyzed. We identified four patients with exon 1 mutations; three were novel (c.1A > T; c.1A > G; c.5C > T), two of which affected the start codon, one a missense change, and one patient had a previously reported splice site mutation, c.62 + 1delGT. The four patients fit criteria for classical RTT, and thus these findings add support to previous reports that exon 1 mutations may be associated with a severe phenotype. Also, these findings add significant weight to the mounting evidence suggesting that the MeCP2_e1 isoform is the etiologically relevant form of the protein.
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Affiliation(s)
- Carol J Saunders
- Department of Pathology and Laboratory Medicine, The Children's Mercy Hospitals and Clinics, Kansas City, Missouri, USA.
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26
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Fichou Y, Nectoux J, Bahi-Buisson N, Rosas-Vargas H, Girard B, Chelly J, Bienvenu T. The first missense mutation causing Rett syndrome specifically affecting the MeCP2_e1 isoform. Neurogenetics 2008; 10:127-33. [PMID: 19034540 DOI: 10.1007/s10048-008-0161-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 10/17/2008] [Indexed: 10/21/2022]
Abstract
We report the identification of the first de novo mutation at a highly conserved residue within the polyalanine stretch in the N-terminal region of the brain-dominant protein isoform MeCP2_e1 in a girl with classical Rett syndrome. The missense mutation, p.Ala2Val, leads to severe developmental delay, microcephaly, no language, severe epilepsy, and cognitive impairment. To evaluate the pathogenic potentials of the MECP2 mutation specific to the MeCP2_e1 isoform detected in this patient, full-length wild-type and mutated cDNAs were cloned in eukaryotic expression vectors to generate a fusion protein with c-myc, and constructs were transfected in COS7 cells. In vitro studies demonstrated that, like wild-type MeCP2e_1, the N-terminal mutant is localized in the nucleus. Neither transcriptional nor translational effect on the MeCP2_e2 isoform was observed in fibroblasts from the p.Ala2Val patient, suggesting that MeCP2_e1 is involved in other functional process. These data suggest the important involvement of the N-terminus in the function of MeCP2 protein, and provide further evidence for the major impact of a specific MeCP2e_1 deficiency in the development of intellectual processing.
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Affiliation(s)
- Yann Fichou
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
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27
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Neul JL, Fang P, Barrish J, Lane J, Caeg EB, Smith EO, Zoghbi H, Percy A, Glaze DG. Specific mutations in methyl-CpG-binding protein 2 confer different severity in Rett syndrome. Neurology 2008; 70:1313-21. [PMID: 18337588 DOI: 10.1212/01.wnl.0000291011.54508.aa] [Citation(s) in RCA: 347] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To determine if a relationship exists between the clinical features of Rett syndrome, an X-linked dominant neurodevelopmental disorder, and specific mutations in MECP2. METHOD Cross-sectional study of 245 girls and women with typical Rett syndrome seen between 1990 and 2004 in tertiary academic outpatient specialty clinics and who had complete MECP2 mutation analysis. A structured clinical evaluation was completed for each participant. The results were grouped by MECP2 mutation and compared. RESULTS Participants with the R133C mutation are less severely affected than those with R168X or large DNA deletions (p < 0.05). Likewise, individuals with the R168X mutation are more severely affected than those with R294X and late carboxy-terminal truncating mutations (p < 0.05). Clinical differences are notable in ambulation, hand use, and language (p < 0.004), three cardinal features of Rett syndrome. Individuals with R168X are less likely to walk (p = 0.008), retain hand use (p = 0.002), or use words (p = 0.001). In contrast, those with carboxy-terminal truncations are more likely to walk (p = 0.007) and use words (p < 0.001). The R306C mutation, previously found to confer milder features, adversely affects only one clinical feature, language (p < 0.05). CONCLUSIONS Specific mutations in MECP2 confer different severity. These results allow the design of therapies targeted toward the amelioration of expected problems. Furthermore, the distinct effects of MECP2 mutations on clinical severity must be considered in clinical intervention trials.
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Affiliation(s)
- J L Neul
- Section of Neurology, Department of Pediatrics, Baylor College of Medicine, Room 319C, One Baylor Plaza, Houston, TX 77030, USA.
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Scala E, Longo I, Ottimo F, Speciale C, Sampieri K, Katzaki E, Artuso R, Mencarelli MA, D'Ambrogio T, Vonella G, Zappella M, Hayek G, Battaglia A, Mari F, Renieri A, Ariani F. MECP2 deletions and genotype-phenotype correlation in Rett syndrome. Am J Med Genet A 2008; 143A:2775-84. [PMID: 17968969 DOI: 10.1002/ajmg.a.32002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rett syndrome is a neurodevelopmental disorder that represents one of the most common genetic causes of mental retardation in girls. MECP2 point mutations in exons 2-4 account for about 80% of classic Rett cases and for a lower percentage of variant patients. We investigated the genetic cause in 77 mutation-negative Rett patients (33 classic, 31 variant, and 13 Rett-like cases) by searching missed MECP2 defects. DHPLC analysis of exon 1 and MLPA analysis allowed us to identify the defect in 17 Rett patients: one exon 1 point mutation (c.47_57del) in a classic case and 16 MECP2 large deletions (15/33 classic and 1/31 variant cases). One identical intragenic MECP2 deletion, probably due to gonadal mosaicism, was found in two sisters with discordant phenotype: one classic and one "highly functioning" preserved speech variant. This result indicates that other epigenetic or genetic factors, beside MECP2, may contribute to phenotype modulation. Three out of 16 MECP2 deletions extend to the adjacent centromeric IRAK1 gene. A putative involvement of the hemizygosity of this gene in the ossification process is discussed. Finally, results reported here clearly indicate that MECP2 large deletions are a common cause of classic Rett, and MLPA analysis is mandatory in MECP2-negative patients, especially in those more severely affected (P = 0.044).
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Affiliation(s)
- Elisa Scala
- Medical Genetics, Molecular Biology Department, University of Siena, Siena, Italy
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Francke U. Mechanisms of disease: neurogenetics of MeCP2 deficiency. ACTA ACUST UNITED AC 2007; 2:212-21. [PMID: 16932552 DOI: 10.1038/ncpneuro0148] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 01/24/2006] [Indexed: 02/03/2023]
Abstract
Rett syndrome (RTT) is unique among genetic, chromosomal and other developmental disorders because of its extreme female gender bias, early normal development, and subsequent developmental regression with loss of motor and language skills. RTT is caused by heterozygosity for mutations in the X-linked gene MECP2, which encodes methyl-CpG binding protein 2. MeCP2 is a multifunctional protein that can act as an architectural chromatin-binding protein, a function that is unrelated to its ability to bind methyl-CpG and to attract chromatin modification complexes. Inactivating mutations that cause RTT in females are not prenatally lethal in males, but lead to profound congenital encephalopathy. Molecular diagnoses of RTT, through demonstration of a MECP2 mutation, made at an early stage of the disorder, usually confirm the sporadic nature and very low recurrence risk of the condition. A positive DNA test result, however, also predicts the inevitable clinical course, given the lack of effective intervention. Initial hypotheses indicating that the MeCP2 protein acts as a genome-wide transcriptional repressor were not confirmed by global gene expression studies in various tissues of individuals with RTT and mouse models of MeCP2 deficiency. Rather, recent evidence points to low-magnitude effects of a small number of genes--including the brain--derived neurotrophic factor pathway and glucocorticoid response genes-that might affect formation and maturation of synapses or synaptic function in postmitotic neurons.
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Affiliation(s)
- Uta Francke
- Department of Genetics, Stanford University School of Medicine, Beckman Center for Molecular and Genetic Medicine B201, Stanford, CA 94305-5323, USA.
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30
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Campos M, Abdalla CB, Santos-Rebouças CB, dos Santos AV, Pestana CP, Domingues ML, dos Santos JM, Pimentel MMG. Low significance of MECP2 mutations as a cause of mental retardation in Brazilian males. Brain Dev 2007; 29:293-7. [PMID: 17084570 DOI: 10.1016/j.braindev.2006.09.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 08/11/2006] [Accepted: 09/26/2006] [Indexed: 11/24/2022]
Abstract
MeCP2 is a protein that selectively binds to methylated cytosines through its methyl-CpG-binding domain (MBD) and connects DNA methylation to transcriptional repression. Mutations in MECP2 gene, located in Xq28, have been reported as being the major cause of Rett syndrome and are also associated with some cases of X-linked mental retardation in both males and females. In this study, we present the first screening in the MECP2 gene in a Brazilian cohort of 239 unrelated males with idiopathic mental retardation. Eight sequence variations were observed in 10 patients: one novel putative pathogenic variant, two never described variants of unknown pathogenic value and five non-pathogenic variations. We conclude that in mentally retarded Brazilian males, non-pathogenic variants in the MECP2 gene are more common than actual pathogenic mutations, and therefore alterations in this gene have a weak relationship with mental retardation in males.
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Affiliation(s)
- Mário Campos
- Human Genetics Service, Department of Cell Biology and Genetics, State University of Rio de Janeiro, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro 20550-013, Brazil
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31
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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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Zahorakova D, Rosipal R, Hadac J, Zumrova A, Bzduch V, Misovicova N, Baxova A, Zeman J, Martasek P. Mutation analysis of the MECP2 gene in patients of Slavic origin with Rett syndrome: novel mutations and polymorphisms. J Hum Genet 2007; 52:342-348. [PMID: 17387578 DOI: 10.1007/s10038-007-0121-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Accepted: 01/19/2007] [Indexed: 01/09/2023]
Abstract
Rett syndrome (RTT), an X-linked dominant neurodevelopmental disorder in females, is caused mainly by de novo mutations in the methyl-CpG-binding protein 2 gene (MECP2). Here we report mutation analysis of the MECP2 gene in 87 patients with RTT from the Czech and Slovak Republics, and Ukraine. The patients, all girls, with classical RTT were investigated for mutations using bi-directional DNA sequencing and conformation sensitive gel electrophoresis analysis of the coding sequence and exon/intron boundaries of the MECP2 gene. Restriction fragment length polymorphism analysis was performed to confirm the mutations that cause the creation or abolition of the restriction site. Mutation-negative cases were subsequently examined by multiple ligation-dependent probe amplification (MLPA) to identify large deletions. Mutation screening revealed 31 different mutations in 68 patients and 12 non-pathogenic polymorphisms. Six mutations have not been previously published: two point mutations (323T>A, 904C>T), three deletions (189_190delGA, 816_832del17, 1069delAGC) and one deletion/inversion (1063_1236del174;1189_1231inv43). MLPA analysis revealed large deletions in two patients. The detection rate was 78.16%. Our results confirm the high frequency of MECP2 mutations in females with RTT and provide data concerning the mutation heterogeneity in the Slavic population.
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Affiliation(s)
- Daniela Zahorakova
- Department of Pediatrics, First School of Medicine, Charles University, Ke Karlovu 2, 128 08, Prague 2, Czech Republic
| | - Robert Rosipal
- Department of Pediatrics, First School of Medicine, Charles University, Ke Karlovu 2, 128 08, Prague 2, Czech Republic
| | - Jan Hadac
- Department of Child Neurology, Thomayer University Hospital, Prague, Czech Republic
| | - Alena Zumrova
- Department of Child Neurology, University Hospital Motol, Prague, Czech Republic
| | - Vladimir Bzduch
- First Department of Pediatrics, Commenius University Children's Hospital, Bratislava, Slovakia
| | - Nadezda Misovicova
- Department of Clinical Genetics, Martin University Hospital, Martin, Slovakia
| | - Alice Baxova
- Institute of Biology and Clinical Genetics, General University Hospital, Prague, Czech Republic
| | - Jiri Zeman
- Department of Pediatrics, First School of Medicine, Charles University, Ke Karlovu 2, 128 08, Prague 2, Czech Republic
| | - Pavel Martasek
- Department of Pediatrics, First School of Medicine, Charles University, Ke Karlovu 2, 128 08, Prague 2, Czech Republic.
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Petel-Galil Y, Benteer B, Galil YP, Zeev BB, Greenbaum I, Vecsler M, Goldman B, Lohi H, Minassian BA, Gak E. Comprehensive diagnosis of Rett's syndrome relying on genetic, epigenetic and expression evidence of deficiency of the methyl-CpG-binding protein 2 gene: study of a cohort of Israeli patients. J Med Genet 2006; 43:e56. [PMID: 17142618 PMCID: PMC2563193 DOI: 10.1136/jmg.2006.041285] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Despite advances in the characterisation of mutations in the MECP2-coding region, a small proportion of classic RTT cases remain without recognisable mutations. OBJECTIVE AND METHODS To identify previously unknown mutations, a quantitative assay was established, providing estimates of MECP2_e1 and MECP2_e2 expression levels in peripheral blood. A systematic analysis of an Israeli cohort of 82 patients with classic and atypical RTT is presented, including sequence analysis of the MECP2-coding region, MLPA, XCI and quantitative expression assays. RESULTS AND CONCLUSION A novel mis-sense mutation at ca 453C-->T (pD151E), resulting in a change of a conserved residue at the methyl-binding domain, and a rare GT deletion of intron 1 donor splice site are reported. It is shown that various MECP2 mutations had distinct effects on MECP2 expression levels in peripheral blood. The most significant (p<0.001) reduction in the expression of both MECP2 isoforms was related to the presence of the intron 1 donor splice-site mutation. Using quantitative expression assays, it was shown that several patients with classic and atypical RTT with no mutation findings had significantly lower MECP2 expression levels. Further research on these patients may disclose still elusive non-coding regulatory MECP2 mutations.
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Abstract
In this review, we give a clinical overview of Rett syndrome (RTT), and provide a framework for clinical and molecular approaches to the diagnosis of this severe neurodevelopmental disorder. We also discuss issues that need to be considered in the management of RTT patients, and raise some of the challenges associated with genetic counselling.
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Affiliation(s)
- Sarah L Williamson
- Western Sydney Genetics Program, the Royal Alexandra Hospital for Children, Sydney, Australia
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Li MR, Pan H, Bao XH, Zhang YZ, Wu XR. MECP2 and CDKL5 gene mutation analysis in Chinese patients with Rett syndrome. J Hum Genet 2006; 52:38-47. [PMID: 17089071 DOI: 10.1007/s10038-006-0079-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Accepted: 09/26/2006] [Indexed: 10/24/2022]
Abstract
Rett syndrome (RTT) is a progressive neurodevelopmental disorder that is caused by mutations in the X-linked methyl-CpG-binding protein2 (MECP2) gene. In this study, the MECP2 sequences in 121 unrelated Chinese patients with classical or atypical RTT were screened for deletions and mutations. In all, we identified 45 different MECP2 mutations in 102 of these RTT patients. The p. T158M mutation (15.7%) was the most common, followed in order of frequency by p. R168X (11.8%), p. R133C (6.9%), p. R270X (6.9%), p. G269fs (6.9%), p. R255X (4.9%), and p. R306C (3.9%). In addition, we identified five novel MECP2 mutations: three missense (p. K305E, p. V122M, p. A358T), one insertion (c.45-46insGGAGGA), and one 22 bp deletion (c.881-902del22). Large deletions represented 10.5% of all identified MECP2 mutations. Conversely, mutations in exon 1 appeared to be rare (0.9%). The remaining cases without MECP2 mutations were screened for the cyclin-dependent kinase-like 5 (CDKL5) gene using denaturing high-performance liquid chromatography (DHPLC). One synonymous mutation (p. I72I) was found in exon 5, suggesting that CDKL5 is a rare cause of RTT. The overall MECP2 mutation detection rate for this patient series was 84.3:87.9% in 107 classical RTT cases and 57.1% in 14 atypical RTT cases. Moreover, there were two patients with homozygous mutations and normal female karyotypes. However, we did not pinpoint a significant relationship between genotype and phenotype in these cases.
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Affiliation(s)
- Mei-Rong Li
- Department of Pediatrics, Peking University First Hospital, No.1 of Xi An Men Street, Xi Cheng District, Beijing, 100034, People's Republic of China
| | - Hong Pan
- Department of Pediatrics, Peking University First Hospital, No.1 of Xi An Men Street, Xi Cheng District, Beijing, 100034, People's Republic of China.
| | - Xin-Hua Bao
- Department of Pediatrics, Peking University First Hospital, No.1 of Xi An Men Street, Xi Cheng District, Beijing, 100034, People's Republic of China
| | - Yu-Zhi Zhang
- Department of Pediatrics, Peking University First Hospital, No.1 of Xi An Men Street, Xi Cheng District, Beijing, 100034, People's Republic of China
| | - Xi-Ru Wu
- Department of Pediatrics, Peking University First Hospital, No.1 of Xi An Men Street, Xi Cheng District, Beijing, 100034, People's Republic of China
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Delgado IJ, Kim DS, Thatcher KN, LaSalle JM, Van den Veyver IB. Expression profiling of clonal lymphocyte cell cultures from Rett syndrome patients. BMC MEDICAL GENETICS 2006; 7:61. [PMID: 16859563 PMCID: PMC1569822 DOI: 10.1186/1471-2350-7-61] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Accepted: 07/21/2006] [Indexed: 11/10/2022]
Abstract
Background More than 85% of Rett syndrome (RTT) patients have heterozygous mutations in the X-linked MECP2 gene which encodes methyl-CpG-binding protein 2, a transcriptional repressor that binds methylated CpG sites. Because MECP2 is subject to X chromosome inactivation (XCI), girls with RTT express either the wild type or mutant MECP2 in each of their cells. To test the hypothesis that MECP2 mutations result in genome-wide transcriptional deregulation and identify its target genes in a system that circumvents the functional mosaicism resulting from XCI, we performed gene expression profiling of pure populations of untransformed T-lymphocytes that express either a mutant or a wild-type allele. Methods Single T lymphocytes from a patient with a c.473C>T (p.T158M) mutation and one with a c.1308-1309delTC mutation were subcloned and subjected to short term culture. Gene expression profiles of wild-type and mutant clones were compared by oligonucleotide expression microarray analysis. Results Expression profiling yielded 44 upregulated genes and 77 downregulated genes. We compared this gene list with expression profiles of independent microarray experiments in cells and tissues of RTT patients and mouse models with Mecp2 mutations. These comparisons identified a candidate MeCP2 target gene, SPOCK1, downregulated in two independent microarray experiments, but its expression was not altered by quantitative RT-PCR analysis on brain tissues from a RTT mouse model. Conclusion Initial expression profiling from T-cell clones of RTT patients identified a list of potential MeCP2 target genes. Further detailed analysis and comparison to independent microarray experiments did not confirm significantly altered expression of most candidate genes. These results are consistent with other reported data.
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Affiliation(s)
- Ivan J Delgado
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA
- Senior Scientist, Identigene Inc., 5615 Kirby, Suite 800 Houston, TX 77005, USA
| | - Dong Sun Kim
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA
- Assistant Professor, Department of Anatomy, School of Medicine, Kyungpook National University, South Korea
| | - Karen N Thatcher
- Medical Microbiology and Immunology and Rowe Program in Human Genetics, School of Medicine, University of California, Davis, CA, USA
| | - Janine M LaSalle
- Medical Microbiology and Immunology and Rowe Program in Human Genetics, School of Medicine, University of California, Davis, CA, USA
| | - Ignatia B Van den Veyver
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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Bartholdi D, Klein A, Weissert M, Koenig N, Baumer A, Boltshauser E, Schinzel A, Berger W, Mátyás G. Clinical profiles of four patients with Rett syndrome carrying a novel exon 1 mutation or genomic rearrangement in the MECP2 gene. Clin Genet 2006; 69:319-26. [PMID: 16630165 DOI: 10.1111/j.1399-0004.2006.00604.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene encoding methyl CpG binding protein 2 (MeCP2). Recently, a new isoform of MeCP2 including exon 1 was identified. This new isoform is more abundantly expressed in brain than the isoform including exons 2-4. Very little is known about the phenotypes associated with mutations in exon 1 of MECP2 since only a limited number of RTT patients carrying such mutations have been identified so far. In this study, we screened a cohort of 20 girls with RTT for exon 1 mutations by sequencing and multiplex ligation-dependent probe amplification (MLPA). We identified one girl with a novel exon 1 mutation (c.30delCinsGA) by sequencing and three with genomic rearrangements by MLPA. Comparison of the phenotypes showed that the girls carrying a mutation or rearrangement encompassing exon 1 were more severely affected than the girls with rearrangements not affecting exon 1.
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Affiliation(s)
- D Bartholdi
- Institute of Medical Genetics, University of Zurich, Schwerzenbach.
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38
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Moog U, Van Roozendaal K, Smeets E, Tserpelis D, Devriendt K, Buggenhout GV, Frijns JP, Schrander-Stumpel C. MECP2 mutations are an infrequent cause of mental retardation associated with neurological problems in male patients. Brain Dev 2006; 28:305-10. [PMID: 16376510 DOI: 10.1016/j.braindev.2005.10.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 09/04/2005] [Accepted: 10/14/2005] [Indexed: 02/04/2023]
Abstract
Mutations in the methyl-CpG-binding protein 2 (MECP2) gene located on Xq28, cause Rett syndrome (RTT) in female patients. Meanwhile, nonmosaic MECP2 mutations unknown in girls have been found in an increasing number of male patients with a normal 46, XY karyotype. They can cause a broad spectrum of neurodevelopmental disorders which often show a combination of mental retardation (MR) with neurological symptoms. We present the results of MECP2 analysis in a group of 72 male patients with an unexplained combination of MR and neurological features, and review the mutational reports published on male patients since the discovery of the MECP2 gene. Analysis included sequencing of exon 1 which thus far was mostly omitted from DNA screening. One pathogenic mutation has been found in a patient with Rett variant, in addition to an unclassified variant and a series of nonpathogenic changes. No changes have been found in exon 1. Criteria for testing of male patients are classic RTT, severe neonatal encephalopathy, and RTT variant which may be clinically underrecognized. Testing can also be considered in males with a combination of unexplained MR and (progressive) neurological manifestations although the yield of MECP2 analysis is probably low in this situation. Based on the literature, MECP2 testing in males with MR only is debatable.
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Affiliation(s)
- Ute Moog
- Department of Clinical Genetics, University Hospital Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
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Laurvick CL, de Klerk N, Bower C, Christodoulou J, Ravine D, Ellaway C, Williamson S, Leonard H. Rett syndrome in Australia: a review of the epidemiology. J Pediatr 2006; 148:347-52. [PMID: 16615965 DOI: 10.1016/j.jpeds.2005.10.037] [Citation(s) in RCA: 240] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 09/01/2005] [Accepted: 10/19/2005] [Indexed: 11/22/2022]
Abstract
OBJECTIVE To examine the prevalence, cumulative incidence, and survival in an Australian cohort with Rett syndrome (RTT). STUDY DESIGN The Australian Rett Syndrome Database is a longitudinal data collection that included 276 verified female cases at the end of 2004. Survival was calculated using the Kaplan-Meier product limit method, and cumulative incidence was determined using the complement of the Kaplan-Meier method. RESULTS Most cases (88.4%) have had MECP2 mutation testing, with positive results in 73%. The prevalence of RTT was .88 per 10,000 females in 5- to 18-year-olds, and the cumulative incidence was 1.09 per 10,000 females by 12 years of age. The cumulative incidence by the age of 5 years increased from .39 per 10,000 in the 1980 to 1984 cohort to .76 per 10,000 in birth cohorts beyond 1984. Survival was 77.8% at 25 years, compared with 99.96% survival in the Australian female population. Pneumonia (10/25) was the most common cause of death. CONCLUSIONS The availability of genetic testing has contributed to the changing pattern and timing of RTT diagnosis in Australia. Girls with RTT have worse survival compared with the general female population. When more data are available, it will be possible to evaluate the relationship between survival and specific MECP2 mutations.
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Affiliation(s)
- Crystal L Laurvick
- Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, Perth
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40
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Quenard A, Yilmaz S, Fontaine H, Bienvenu T, Moncla A, des Portes V, Rivier F, Mathieu M, Raux G, Jonveaux P, Philippe C. Deleterious mutations in exon 1 of MECP2 in Rett syndrome. Eur J Med Genet 2005; 49:313-22. [PMID: 16829352 DOI: 10.1016/j.ejmg.2005.11.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Accepted: 11/29/2005] [Indexed: 11/15/2022]
Abstract
The MECP2 gene is responsible for 80-85% of typical cases of Rett syndrome with deleterious mutations affecting exons 3 and 4. Recently, an alternate transcript including exon 1 was discovered with a new protein isoform (MeCP2_e1) much more abundant in brain. We screened exon 1 of MECP2 for mutations and for large rearrangements in a panel of 212 typical cases of Rett syndrome and one family case with atypical Rett syndrome. We identified two deleterious mutations (c.48_55dup and c.62+2_62+3del) and four large rearrangements encompassing exon 1 of MECP2. We also identified the c.16_21dup alteration formerly reported as c.3_4insGCCGCC and give additional support to classify this sequence variation as polymorphic. In our large panel of typical Rett, mutations affecting exon 1 of MECP2 represent 1% of the deleterious alleles. This study confirms that mutations in exon 1 of MECP2 are a rare cause of Rett syndrome.
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Affiliation(s)
- Aline Quenard
- Laboratoire de Génétique, EA 3441, CHU Brabois, avenue du Morvan, 54511 Vandoeuvre-les-Nancy cedex, France
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Abuhatzira L, Makedonski K, Galil YP, Gak E, Ben Zeev B, Razin A, Shemer R. Splicing mutation associated with Rett syndrome and an experimental approach for genetic diagnosis. Hum Genet 2005; 118:91-8. [PMID: 16133181 DOI: 10.1007/s00439-005-0025-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 06/20/2005] [Indexed: 11/25/2022]
Abstract
Around 80% of Rett syndrome (RS) cases have a mutation or deletion within the coding sequence of the MeCP2 gene. The other RS patients remain genetically undiagnosed. A significant fraction (10-15%) of disease-causing mutations in humans, affect pre-mRNA splicing. Two potential splice mutations were found in the MeCP2 gene in RS patients, however it was not clear whether these mutations in fact interfere with splicing and consequently cause RS. One such mutation is a deletion of the GT dinucleotide at the 5' donor splice site of exon 1 and the other a deletion of the T nucleotide in the polypyrimidine tract (PPT) of intron 3. Here we experimentally assess the effects exerted by these mutations on the expression of MeCP2 in patients' blood samples and on splicing of the MeCP2 transcript using a hybrid minigene in transient transfection experiments. The results revealed that the Delta T mutation in the PPT is a benign polymorphism and that the GT deletion in intron 1 is a bona fide splicing mutation that causes a complete skipping of exon 1 in the minigene transfection experiment. This explains the observed complete elimination of the MeCP2 message and protein in the lymphoblast clones of the RS patient that carry the mutation on the active X. An analysis of the MeCP2 transcript and protein production in lymphoblast clones, as described here, can be used to confirm clinically diagnosed RS patients with no mutation in the MeCP2 coding sequence. This will enable RS diagnosis without specifically identifying a mutation.
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Affiliation(s)
- Liron Abuhatzira
- Department of Cellular Biochemistry and Human Genetics, Hadassah Medical School, The Hebrew University, Jerusalem, Israel
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Saxena A, de Lagarde D, Leonard H, Williamson SL, Vasudevan V, Christodoulou J, Thompson E, MacLeod P, Ravine D. Lost in translation: translational interference from a recurrent mutation in exon 1 of MECP2. J Med Genet 2005; 43:470-7. [PMID: 16155192 PMCID: PMC2593027 DOI: 10.1136/jmg.2005.036244] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Rett syndrome (RTT) is an X linked neuro-developmental disorder affecting mostly girls. Mutations in the coding region of MECP2 are found in 80% of classic RTT patients. Until recently, the region encoding MECP2 was believed to comprise exons 2, 3, and 4 with the ATG start site located at the end of exon 2 (MeCP2_e2). METHODS Recent reports of another mRNA transcript transcribed from exon 1 (MeCP2_e1) prompted us to screen exon 1 among RNA samples from 20 females with classic or atypical RTT. RESULTS A previously reported 11 base pair deletion in exon 1 was detected in one subject with a milder phenotype. Although RNA expression for both protein isoforms was detected from the mutant allele, evaluation of MeCP2 protein in uncultured patient lymphocytes by immunocytochemistry revealed that MeCP2 protein production was restricted to only 74-76% of lymphocytes. X chromosome inactivation studies of genomic DNA revealed similar XCI ratios at the HUMARA locus (73:27 with HpaII and 74:26 with McrBC). We have demonstrated that translation but not transcription of the MeCP2_e2 isoform is ablated by the 11 nucleotide deletion, 103 nucleotides upstream of the e2 translation start site. CONCLUSIONS These findings reveal that nucleotides within the deleted sequence in the 5'-UTR of the MeCP2_e2 transcript, while not required for transcription, are essential for translation.
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Affiliation(s)
- A Saxena
- Western Australian Institute for Medical Research, Centre for Medical Research, University of Western Australia, Level 2, North Block, Perth 6000, WA, Australia
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Abstract
Rett syndrome is a leading cause of postnatal neurodevelopmental regression. Rett syndrome is caused by mutations in MECP2, the gene encoding methyl-CpG binding protein 2. In up to 96% of all classic cases, Rett syndrome cases are caused by mutations or deletions in MECP2. The phenotypic spectrum of MECP2 mutations is broad and includes mental retardation with or without seizures, Angelman syndrome-like phenotype, and autism. Mecp308/Y mice carry a truncating mutation and display many of the features seen in Rett syndrome. Social behavior abnormalities and impaired social interactions in Mecp308/Y mice suggest that MeCP2 plays a role in modulating the activity of genes and neurons important for social interactions. Mice that overexpress MeCP2 at twice the endogenous levels develop a progressive neurologic disorder, demonstrating that MeCP2 levels are tightly regulated and raising the possibility that duplications or gain-of-function mutations of MECP2 might underlie some cases of neurodevelopmental X-linked disorders.
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44
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LaSalle JM, Hogart A, Thatcher KN. Rett Syndrome: A Rosetta Stone for Understanding the Molecular Pathogenesis of Autism. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 71:131-65. [PMID: 16512349 DOI: 10.1016/s0074-7742(05)71006-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Affiliation(s)
- Janine M LaSalle
- Medical Microbiology and Immunology and Rowe Program in Human Genetics, School of Medicine, University of California, Davis 95616, USA
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