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Canton APM, Tinano FR, Guasti L, Montenegro LR, Ryan F, Shears D, de Melo ME, Gomes LG, Piana MP, Brauner R, Espino-Aguilar R, Escribano-Muñoz A, Paganoni A, Read JE, Korbonits M, Seraphim CE, Costa SS, Krepischi AC, Jorge AAL, David A, Kaisinger LR, Ong KK, Perry JRB, Abreu AP, Kaiser UB, Argente J, Mendonca BB, Brito VN, Howard SR, Latronico AC. Rare variants in the MECP2 gene in girls with central precocious puberty: a translational cohort study. Lancet Diabetes Endocrinol 2023; 11:545-554. [PMID: 37385287 PMCID: PMC7615084 DOI: 10.1016/s2213-8587(23)00131-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 04/22/2023] [Accepted: 04/22/2023] [Indexed: 07/01/2023]
Abstract
BACKGROUND Identification of genetic causes of central precocious puberty have revealed epigenetic mechanisms as regulators of human pubertal timing. MECP2, an X-linked gene, encodes a chromatin-associated protein with a role in gene transcription. MECP2 loss-of-function mutations usually cause Rett syndrome, a severe neurodevelopmental disorder. Early pubertal development has been shown in several patients with Rett syndrome. The aim of this study was to explore whether MECP2 variants are associated with an idiopathic central precocious puberty phenotype. METHODS In this translational cohort study, participants were recruited from seven tertiary centres from five countries (Brazil, Spain, France, the USA, and the UK). Patients with idiopathic central precocious puberty were investigated for rare potentially damaging variants in the MECP2 gene, to assess whether MECP2 might contribute to the cause of central precocious puberty. Inclusion criteria were the development of progressive pubertal signs (Tanner stage 2) before the age of 8 years in girls and 9 years in boys and basal or GnRH-stimulated LH pubertal concentrations. Exclusion criteria were the diagnosis of peripheral precocious puberty and the presence of any recognised cause of central precocious puberty (CNS lesions, known monogenic causes, genetic syndromes, or early exposure to sex steroids). All patients included were followed up at the outpatient clinics of participating academic centres. We used high-throughput sequencing in 133 patients and Sanger sequencing of MECP2 in an additional 271 patients. Hypothalamic expression of Mecp2 and colocalisation with GnRH neurons were determined in mice to show expression of Mecp2 in key nuclei related to pubertal timing regulation. FINDINGS Between Jun 15, 2020, and Jun 15, 2022, 404 patients with idiopathic central precocious puberty (383 [95%] girls and 21 [5%] boys; 261 [65%] sporadic cases and 143 [35%] familial cases from 134 unrelated families) were enrolled and assessed. We identified three rare heterozygous likely damaging coding variants in MECP2 in five girls: a de novo missense variant (Arg97Cys) in two monozygotic twin sisters with central precocious puberty and microcephaly; a de novo missense variant (Ser176Arg) in one girl with sporadic central precocious puberty, obesity, and autism; and an insertion (Ala6_Ala8dup) in two unrelated girls with sporadic central precocious puberty. Additionally, we identified one rare heterozygous 3'UTR MECP2 insertion (36_37insT) in two unrelated girls with sporadic central precocious puberty. None of them manifested Rett syndrome. Mecp2 protein colocalised with GnRH expression in hypothalamic nuclei responsible for GnRH regulation in mice. INTERPRETATION We identified rare MECP2 variants in girls with central precocious puberty, with or without mild neurodevelopmental abnormalities. MECP2 might have a role in the hypothalamic control of human pubertal timing, adding to the evidence of involvement of epigenetic and genetic mechanisms in this crucial biological process. FUNDING Fundação de Amparo à Pesquisa do Estado de São Paulo, Conselho Nacional de Desenvolvimento Científico e Tecnológico, and the Wellcome Trust.
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Affiliation(s)
- Ana P M Canton
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Flávia R Tinano
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Leonardo Guasti
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Luciana R Montenegro
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Fiona Ryan
- Oxford Children's Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Deborah Shears
- Oxford Centre for Genomic Medicine, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | | | - Larissa G Gomes
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | | | - Raja Brauner
- Fondation Ophtalmologique Adolphe de Rothschild and Université de Paris, Paris, France
| | | | - Arancha Escribano-Muñoz
- Endocrinology Unit, Department of Pediatrics, Virgen de la Arrixaca University Hospital, Murcia, Spain
| | - Alyssa Paganoni
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Jordan E Read
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Márta Korbonits
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Carlos E Seraphim
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Silvia S Costa
- Discipline of Endocrinology and Metabolism, Clinicas Hospital, School of Medicine and Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Ana Cristina Krepischi
- Discipline of Endocrinology and Metabolism, Clinicas Hospital, School of Medicine and Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Alexander A L Jorge
- Genetic Endocrinology Unit LIM/25, University of Sao Paulo, Sao Paulo, Brazil
| | - Alessia David
- Centre for Integrative Systems Biology and Bioinformatics, Department of Life Sciences, Imperial College London, London, UK
| | - Lena R Kaisinger
- Medical Research Council Epidemiology Unit, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge School of Clinical Medicine, Cambridge, UK
| | - Ken K Ong
- Medical Research Council Epidemiology Unit, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge School of Clinical Medicine, Cambridge, UK
| | - John R B Perry
- Medical Research Council Epidemiology Unit, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge School of Clinical Medicine, Cambridge, UK
| | - Ana Paula Abreu
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Ursula B Kaiser
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Jesús Argente
- Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain; Department of Pediatrics and Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, IMDEA Food Institute, Madrid, Spain
| | - Berenice B Mendonca
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Vinicius N Brito
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil
| | - Sasha R Howard
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK; Department of Paediatric Endocrinology, Barts Health NHS Trust, London, UK
| | - Ana Claudia Latronico
- Developmental Endocrinology Unit, Laboratory of Hormones and Molecular Genetics LIM/42, University of Sao Paulo, Sao Paulo, Brazil.
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Good KV, Vincent JB, Ausió J. MeCP2: The Genetic Driver of Rett Syndrome Epigenetics. Front Genet 2021; 12:620859. [PMID: 33552148 PMCID: PMC7859524 DOI: 10.3389/fgene.2021.620859] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/05/2021] [Indexed: 12/24/2022] Open
Abstract
Mutations in methyl CpG binding protein 2 (MeCP2) are the major cause of Rett syndrome (RTT), a rare neurodevelopmental disorder with a notable period of developmental regression following apparently normal initial development. Such MeCP2 alterations often result in changes to DNA binding and chromatin clustering ability, and in the stability of this protein. Among other functions, MeCP2 binds to methylated genomic DNA, which represents an important epigenetic mark with broad physiological implications, including neuronal development. In this review, we will summarize the genetic foundations behind RTT, and the variable degrees of protein stability exhibited by MeCP2 and its mutated versions. Also, past and emerging relationships that MeCP2 has with mRNA splicing, miRNA processing, and other non-coding RNAs (ncRNA) will be explored, and we suggest that these molecules could be missing links in understanding the epigenetic consequences incurred from genetic ablation of this important chromatin modifier. Importantly, although MeCP2 is highly expressed in the brain, where it has been most extensively studied, the role of this protein and its alterations in other tissues cannot be ignored and will also be discussed. Finally, the additional complexity to RTT pathology introduced by structural and functional implications of the two MeCP2 isoforms (MeCP2-E1 and MeCP2-E2) will be described. Epigenetic therapeutics are gaining clinical popularity, yet treatment for Rett syndrome is more complicated than would be anticipated for a purely epigenetic disorder, which should be taken into account in future clinical contexts.
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Affiliation(s)
- Katrina V. Good
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - John B. Vincent
- Molecular Neuropsychiatry & Development (MiND) Lab, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
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3
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Luoma LM, Berry FB. Molecular analysis of NPAS3 functional domains and variants. BMC Mol Biol 2018; 19:14. [PMID: 30509165 PMCID: PMC6276216 DOI: 10.1186/s12867-018-0117-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 11/26/2018] [Indexed: 12/14/2022] Open
Abstract
Background NPAS3 encodes a transcription factor which has been associated with multiple human psychiatric and neurodevelopmental disorders. In mice, deletion of Npas3 was found to cause alterations in neurodevelopment, as well as a marked reduction in neurogenesis in the adult mouse hippocampus. This neurogenic deficit, alongside the reduction in cortical interneuron number, likely contributes to the behavioral and cognitive alterations observed in Npas3 knockout mice. Although loss of Npas3 has been found to affect proliferation and apoptosis, the molecular function of NPAS3 is largely uncharacterized outside of predictions based on its high homology to bHLH–PAS transcription factors. Here we set out to characterize NPAS3 as a transcription factor, and to confirm whether NPAS3 acts as predicted for a Class 1 bHLH–PAS family member. Results Through these studies we have experimentally demonstrated that NPAS3 behaves as a true transcription factor, capable of gene regulation through direct association with DNA. NPAS3 and ARNT are confirmed to directly interact in human cells through both bHLH and PAS dimerization domains. The C-terminus of NPAS3 was found to contain a functional transactivation domain. Further, the NPAS3::ARNT heterodimer was shown to directly regulate the expression of VGF and TXNIP through binding of their proximal promoters. Finally, we assessed the effects of three human variants of NPAS3 on gene regulatory function and do not observe significant deficits. Conclusions NPAS3 is a true transcription factor capable of regulating expression of target genes through their promoters by directly cooperating with ARNT. The tested human variants of NPAS3 require further characterization to identify their effects on NPAS3 expression and function in the individuals that carry them. These data enhance our understanding of the molecular function of NPAS3 and the mechanism by which it contributes to normal and abnormal neurodevelopment and neural function. Electronic supplementary material The online version of this article (10.1186/s12867-018-0117-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Leiah M Luoma
- Department of Medical Genetics, University of Alberta, Edmonton, AB, Canada
| | - Fred B Berry
- Department of Medical Genetics, University of Alberta, Edmonton, AB, Canada. .,Department of Surgery, 3002D Li Ka Shing Centre, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
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Sheikh TI, de Paz AM, Akhtar S, Ausió J, Vincent JB. MeCP2_E1 N-terminal modifications affect its degradation rate and are disrupted by the Ala2Val Rett mutation. Hum Mol Genet 2018; 26:4132-4141. [PMID: 28973632 DOI: 10.1093/hmg/ddx300] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 07/24/2017] [Indexed: 11/14/2022] Open
Abstract
Methyl CpG-binding protein 2 (MeCP2), the mutated protein in Rett syndrome (RTT), is a crucial chromatin-modifying and gene-regulatory protein that has two main isoforms (MeCP2_E1 and MeCP2_ E2) due to the alternative splicing and switching between translation start codons in exons one and two. Functionally, these two isoforms appear to be virtually identical; however, evidence suggests that only MeCP2_E1 is relevant to RTT, including a single RTT missense mutation in exon 1, Ala2Val. Here, we show that N-terminal co- and post-translational modifications differ for MeCP2_E1 and MeCP2_E1-Ala2Val, which result in different protein degradation rates in vitro. We report complete N-methionine excision (NME) for MeCP2_E1 and evidence of excision of multiple alanine residues from the N-terminal polyalanine stretch. For MeCP2_E1-Ala2Val, we observed only partial NME and N-acetylation (NA) of either methionine or valine. The localization of MeCP2_E1 and co-localization with chromatin appear to be unaffected by the Ala2Val mutation. However, a higher proteasomal degradation rate was observed for MeCP2_E1-Ala2Val compared with that for wild type MeCP2_E1. Thus, the etiopathology of Ala2Val is likely due to a reduced bio-availability of MeCP2 because of the faster degradation rate of the unmodified defective protein. Our data on the effects of the Ala2Val mutation on N-terminal modifications of MeCP2 may be applicable to Ala2Val mutations in other disease genes for which no etiopathological mechanism has been established.
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Affiliation(s)
- Taimoor I Sheikh
- Molecular Neuropsychiatry & Development (MiND) Lab, Brain Science Division, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada
| | | | - Shamim Akhtar
- University of Engineering and Technology Taxila, Taxila, Punjab 47080, Pakistan
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, BC V8P 5C2, Canada
| | - John B Vincent
- Molecular Neuropsychiatry & Development (MiND) Lab, Brain Science Division, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
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5
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Reilly J, Gallagher L, Chen JL, Leader G, Shen S. Bio-collections in autism research. Mol Autism 2017; 8:34. [PMID: 28702161 PMCID: PMC5504648 DOI: 10.1186/s13229-017-0154-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 06/23/2017] [Indexed: 01/06/2023] Open
Abstract
Autism spectrum disorder (ASD) is a group of complex neurodevelopmental disorders with diverse clinical manifestations and symptoms. In the last 10 years, there have been significant advances in understanding the genetic basis for ASD, critically supported through the establishment of ASD bio-collections and application in research. Here, we summarise a selection of major ASD bio-collections and their associated findings. Collectively, these include mapping ASD candidate genes, assessing the nature and frequency of gene mutations and their association with ASD clinical subgroups, insights into related molecular pathways such as the synapses, chromatin remodelling, transcription and ASD-related brain regions. We also briefly review emerging studies on the use of induced pluripotent stem cells (iPSCs) to potentially model ASD in culture. These provide deeper insight into ASD progression during development and could generate human cell models for drug screening. Finally, we provide perspectives concerning the utilities of ASD bio-collections and limitations, and highlight considerations in setting up a new bio-collection for ASD research.
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Affiliation(s)
- Jamie Reilly
- Regenerative Medicine Institute, School of Medicine, BioMedical Sciences Building, National University of Ireland (NUI), Galway, Ireland
| | - Louise Gallagher
- Trinity Translational Medicine Institute and Department of Psychiatry, Trinity Centre for Health Sciences, St. James Hospital Street, Dublin 8, Ireland
| | - June L Chen
- Department of Special Education, Faculty of Education, East China Normal University, Shanghai, 200062 China
| | - Geraldine Leader
- Irish Centre for Autism and Neurodevelopmental Research (ICAN), Department of Psychology, National University of Ireland Galway, University Road, Galway, Ireland
| | - Sanbing Shen
- Regenerative Medicine Institute, School of Medicine, BioMedical Sciences Building, National University of Ireland (NUI), Galway, Ireland
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6
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Endow JK, Rocha AG, Baldwin AJ, Roston RL, Yamaguchi T, Kamikubo H, Inoue K. Polyglycine Acts as a Rejection Signal for Protein Transport at the Chloroplast Envelope. PLoS One 2016; 11:e0167802. [PMID: 27936133 PMCID: PMC5147994 DOI: 10.1371/journal.pone.0167802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 11/21/2016] [Indexed: 11/19/2022] Open
Abstract
PolyGly is present in many proteins in various organisms. One example is found in a transmembrane β-barrel protein, translocon at the outer-envelope-membrane of chloroplasts 75 (Toc75). Toc75 requires its N-terminal extension (t75) for proper localization. t75 comprises signals for chloroplast import (n75) and envelope sorting (c75) in tandem. n75 and c75 are removed by stromal processing peptidase and plastidic type I signal peptidase 1, respectively. PolyGly is present within c75 and its deletion or substitution causes mistargeting of Toc75 to the stroma. Here we have examined the properties of polyGly-dependent protein targeting using two soluble passenger proteins, the mature portion of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (mSS) and enhanced green fluorescent protein (EGFP). Both t75-mSS and t75-EGFP were imported into isolated chloroplasts and their n75 removed. Resultant c75-mSS was associated with the envelope at the intermembrane space, whereas c75-EGFP was partially exposed outside the envelope. Deletion of polyGly or substitution of tri-Ala for the critical tri-Gly segment within polyGly caused each passenger to be targeted to the stroma. Transient expression of t75-EGFP in Nicotiana benthamiana resulted in accumulation of c75-EGFP exposed at the surface of the chloroplast, but the majority of the EGFP passenger was found free in the cytosol with most of its c75 attachment removed. Results of circular dichroism analyses suggest that polyGly within c75 may form an extended conformation, which is disrupted by tri-Ala substitution. These data suggest that polyGly is distinct from a canonical stop-transfer sequence and acts as a rejection signal at the chloroplast inner envelope.
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Affiliation(s)
- Joshua K. Endow
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
| | - Agostinho Gomes Rocha
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
| | - Amy J. Baldwin
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
| | - Rebecca L. Roston
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
| | - Toshio Yamaguchi
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
| | - Hironari Kamikubo
- Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama, Ikoma, Nara, Japan
| | - Kentaro Inoue
- Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, California, United States of America
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7
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Abstract
Mutations in Methyl-CpG-Binding protein 2 (MECP2) are commonly associated with the neurodevelopmental disorder Rett syndrome (RTT). However, some people with RTT do not have mutations in MECP2, and interestingly there have been people identified with MECP2 mutations that do not have the clinical features of RTT. In this report we present four people with neurodevelopmental abnormalities and clear RTT-disease causing MECP2 mutation but lacking the characteristic clinical features of RTT. One patient's symptoms suggest an extension of the known spectrum of MECP2 associated phenotypes to include global developmental delay with obsessive compulsive disorder and attention deficit hyperactivity disorder. These results reemphasize that RTT should remain a clinical diagnosis, based on the recent consensus criteria.
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8
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Computational and experimental approaches to reveal the effects of single nucleotide polymorphisms with respect to disease diagnostics. Int J Mol Sci 2014; 15:9670-717. [PMID: 24886813 PMCID: PMC4100115 DOI: 10.3390/ijms15069670] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 05/15/2014] [Accepted: 05/16/2014] [Indexed: 12/25/2022] Open
Abstract
DNA mutations are the cause of many human diseases and they are the reason for natural differences among individuals by affecting the structure, function, interactions, and other properties of DNA and expressed proteins. The ability to predict whether a given mutation is disease-causing or harmless is of great importance for the early detection of patients with a high risk of developing a particular disease and would pave the way for personalized medicine and diagnostics. Here we review existing methods and techniques to study and predict the effects of DNA mutations from three different perspectives: in silico, in vitro and in vivo. It is emphasized that the problem is complicated and successful detection of a pathogenic mutation frequently requires a combination of several methods and a knowledge of the biological phenomena associated with the corresponding macromolecules.
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9
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Sheikh TI, Mittal K, Willis MJ, Vincent JB. A synonymous change, p.Gly16Gly in MECP2 Exon 1, causes a cryptic splice event in a Rett syndrome patient. Orphanet J Rare Dis 2013; 8:108. [PMID: 23866855 PMCID: PMC3729535 DOI: 10.1186/1750-1172-8-108] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/12/2013] [Indexed: 12/01/2022] Open
Abstract
Background Mutations in MECP2 are the main cause of Rett Syndrome. To date, no pathogenic synonymous MECP2 mutation has yet been identified. Here, we investigated a de novo synonymous variant c.48C>T (p.Gly16Gly) identified in a girl presenting with a typical RTT phenotype. Methods In silico analyses to predict the effects of sequence variation on mRNA splicing were employed, followed by sequencing and quantification of lymphocyte mRNAs from the subject for splice variants MECP2_E1 and MECP2_E2. Results Analysis of mRNA confirmed predictions that this synonymous mutation activates a splice-donor site at an early position in exon 1, leading to a deletion (r.[=, 48_63del]), codon frameshift and premature stop codon (p.Glu17Lysfs*16) for MECP2_E1. For MECP2_E2, the same premature splice site is used, but as this is located in the 5′untranslated region, no effect on the amino acid sequence is predicted. Quantitative analysis that specifically measured this cryptic splice variant also revealed a significant decrease in the quantity of the correct MECP2_E1 transcript, which indicates that this is the etiologically significant mutation in this patient. Conclusion These findings suggest that synonymous variants of MECP2 as well as other known disease genes—and de novo variants in particular— should be re-evaluated for potential effects on splicing.
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Affiliation(s)
- Taimoor I Sheikh
- Molecular Neuropsychiatry & Development Lab, Campbell Family Mental Health Research Institute, Centre for Addiction & Mental Health, Toronto, Canada
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10
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Persico AM, Napolioni V. Autism genetics. Behav Brain Res 2013; 251:95-112. [PMID: 23769996 DOI: 10.1016/j.bbr.2013.06.012] [Citation(s) in RCA: 173] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 06/03/2013] [Accepted: 06/04/2013] [Indexed: 12/22/2022]
Abstract
Autism spectrum disorder (ASD) is a severe neuropsychiatric disease with strong genetic underpinnings. However, genetic contributions to autism are extremely heterogeneous, with many different loci underlying the disease to a different extent in different individuals. Moreover, the phenotypic expression (i.e., "penetrance") of these genetic components is also highly variable, ranging from fully penetrant point mutations to polygenic forms with multiple gene-gene and gene-environment interactions. Furthermore, many genes involved in ASD are also involved in intellectual disability, further underscoring their lack of specificity in phenotypic expression. We shall hereby review current knowledge on the genetic basis of ASD, spanning genetic/genomic syndromes associated with autism, monogenic forms due to copy number variants (CNVs) or rare point mutations, mitochondrial forms, and polygenic autisms. Finally, the recent contributions of genome-wide association and whole exome sequencing studies will be highlighted.
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Affiliation(s)
- Antonio M Persico
- Child and Adolescent Neuropsychiatry Unit, University Campus Bio-Medico, Rome, Italy.
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11
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Abstract
Rett syndrome (RTT, MIM#312750) is a neurodevelopmental disorder that is classified as an autism spectrum disorder. Clinically, RTT is characterized by psychomotor regression with loss of volitional hand use and spoken language, the development of repetitive hand stereotypies, and gait impairment. The majority of people with RTT have mutations in Methyl-CpG-binding Protein 2 (MECP2), a transcriptional regulator. Interestingly, alterations in the function of the protein product produced by MECP2, MeCP2, have been identified in a number of other clinical conditions. The many clinical features found in RTT and the various clinical problems that result from alteration in MeCP2 function have led to the belief that understanding RTT will provide insight into a number of other neurological disorders. Excitingly, RTT is reversible in a mouse model, providing inspiration and hope that such a goal may be achieved for RTT and potentially for many neurodevelopmental disorders.
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Affiliation(s)
- Jeffrey Lorenz Neul
- Neurological Research Institute, 1250 Moursund Street, Suite 1250.18, Houston, TX 77030, USA.
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12
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Cukier HN, Lee JM, Ma D, Young JI, Mayo V, Butler BL, Ramsook SS, Rantus JA, Abrams AJ, Whitehead PL, Wright HH, Abramson RK, Haines JL, Cuccaro ML, Pericak-Vance MA, Gilbert JR. The expanding role of MBD genes in autism: identification of a MECP2 duplication and novel alterations in MBD5, MBD6, and SETDB1. Autism Res 2012; 5:385-97. [PMID: 23055267 DOI: 10.1002/aur.1251] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 08/02/2012] [Indexed: 01/09/2023]
Abstract
The methyl-CpG-binding domain (MBD) gene family was first linked to autism over a decade ago when Rett syndrome, which falls under the umbrella of autism spectrum disorders (ASDs), was revealed to be predominantly caused by MECP2 mutations. Since that time, MECP2 alterations have been recognized in idiopathic ASD patients by us and others. Individuals with deletions across the MBD5 gene also present with ASDs, impaired speech, intellectual difficulties, repetitive behaviors, and epilepsy. These findings suggest that further investigations of the MBD gene family may reveal additional associations related to autism. We now describe the first study evaluating individuals with ASD for rare variants in four autosomal MBD family members, MBD5, MBD6, SETDB1, and SETDB2, and expand our initial screening in the MECP2 gene. Each gene was sequenced over all coding exons and evaluated for copy number variations in 287 patients with ASD and an equal number of ethnically matched control individuals. We identified 186 alterations through sequencing, approximately half of which were novel (96 variants, 51.6%). We identified 17 ASD specific, nonsynonymous variants, four of which were concordant in multiplex families: MBD5 Tyr1269Cys, MBD6 Arg883Trp, MECP2 Thr240Ser, and SETDB1 Pro1067del. Furthermore, a complex duplication spanning of the MECP2 gene was identified in two brothers who presented with developmental delay and intellectual disability. From our studies, we provide the first examples of autistic patients carrying potentially detrimental alterations in MBD6 and SETDB1, thereby demonstrating that the MBD gene family potentially plays a significant role in rare and private genetic causes of autism.
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Affiliation(s)
- Holly N Cukier
- John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL 33136, USA
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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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Sanmann JN, Schaefer GB, Buehler BA, Sanger WG. Algorithmic approach for methyl-CpG binding protein 2 (MECP2) gene testing in patients with neurodevelopmental disabilities. J Child Neurol 2012; 27:346-54. [PMID: 22123427 DOI: 10.1177/0883073811424796] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Methyl-CpG binding protein 2 gene (MECP2) testing is indicated for patients with numerous clinical presentations, including Rett syndrome (classic and atypical), unexplained neonatal encephalopathy, Angelman syndrome, nonspecific mental retardation, autism (females), and an X-linked family history of developmental delay. Because of this complexity, a gender-specific approach for comprehensive MECP2 gene testing is described. Briefly, sequencing of exons 1 to 4 of MECP2 is recommended for patients with a Rett syndrome phenotype, unexplained neonatal encephalopathy, an Angelman syndrome phenotype (with negative 15q11-13 analysis), nonspecific mental retardation, or autism (females). Additional testing for large-scale MECP2 deletions is recommended for patients with Rett syndrome or Angelman syndrome phenotypes (with negative 15q11-13 analysis) following negative sequencing. Alternatively, testing for large-scale MECP2 duplications is recommended for males presenting with mental retardation, an X-linked family history of developmental delay, and a significant proportion of previously described clinical features (particularly a history of recurrent respiratory infections).
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Affiliation(s)
- Jennifer N Sanmann
- Human Genetics Laboratories, University of Nebraska Medical Center and the Munroe-Meyer Institute for Genetics and Rehabilitation, Omaha, NE 68198-5440, USA.
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Macintyre G, Alford T, Xiong L, Rouleau GA, Tibbo PG, Cox DW. Association of NPAS3 exonic variation with schizophrenia. Schizophr Res 2010; 120:143-9. [PMID: 20466522 DOI: 10.1016/j.schres.2010.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 04/05/2010] [Accepted: 04/07/2010] [Indexed: 01/31/2023]
Abstract
BACKGROUND We previously identified the neuronal PAS3 (NPAS3) gene as a candidate gene for schizophrenia. A mother and daughter, both with schizophrenia, were carriers of a translocation, t(9;14)(q34;q13), that disrupts the NPAS3 gene. The gene is located at 14q13, a region implicated in schizophrenia and bipolar disorder in various linkage studies. NPAS3 belongs to the basic helix-loop-helix Per-Arnt-Sim (bHLH-PAS) transcription factor family, involved in diverse processes including the regulation of cell differentiation and circadian rhythms, and the development and function of the nervous system. METHODS The 12 exons encoding NPAS3 were sequenced in DNA from individuals with schizophrenia. NPAS3 variants were identified in exons 6 and 12, initially in 12 patients only. These two exons were then sequenced in 83 patients and 83 controls. RESULTS AND CONCLUSION Three common variants of NPAS3, also found in controls, showed a positive association with schizophrenia (NM_001164749: rs12434716, c.1654G>C, p=0.009; rs10141940, c.2208C>T, p=0.01; rs10142034, c.2262C>G, p=0.01). The c.1654G>C variant, results in an p.Ala552Pro change and may affect NPAS3 protein function directly. Alternatively, the three SNPs may affect the splicing of NPAS3 transcripts, as they are each located within putative exonic splicing enhancer (ESE) motifs (ESEFinder). A c.726C>T variant, identified in three patients, is located in an ESE element and is predicted to reduce the function of the motif. Other variants, identified in controls, included c.2089G>A (p.Gly697Ser) and c.2097T>C. Our identification of potentially defective NPAS3 variants supports recent studies that implicate perturbations in NPAS3 pathways in impaired neurogenesis and psychosis.
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Affiliation(s)
- Georgina Macintyre
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada.
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Cukier HN, Rabionet R, Konidari I, Rayner-Evans MY, Baltos ML, Wright HH, Abramson RK, Martin ER, Cuccaro ML, Pericak-Vance MA, Gilbert JR. Novel variants identified in methyl-CpG-binding domain genes in autistic individuals. Neurogenetics 2010; 11:291-303. [PMID: 19921286 PMCID: PMC2941261 DOI: 10.1007/s10048-009-0228-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 10/26/2009] [Indexed: 12/01/2022]
Abstract
Misregulation of the methyl-CpG-binding protein 2 (MECP2) gene has been found to cause a myriad of neurological disorders including autism, mental retardation, seizures, learning disabilities, and Rett syndrome. We hypothesized that mutations in other members of the methyl-CpG-binding domain (MBD) family may also cause autistic features in individuals. We evaluated 226 autistic individuals for alterations in the four genes most homologous to MECP2: MBD1, MBD2, MBD3, and MBD4. A total of 46 alterations were identified in the four genes, including ten missense changes and two deletions that alter coding sequence. Several are either unique to our autistic population or cosegregate with affected individuals within a family, suggesting a possible relation of these variations to disease etiology. Variants include a R23M alteration in two affected half brothers which falls within the MBD domain of the MBD3 protein, as well as a frameshift in MBD4 that is predicted to truncate almost half of the protein. These results suggest that rare cases of autism may be influenced by mutations in members of the dynamic MBD protein family.
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Affiliation(s)
- Holly N. Cukier
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Raquel Rabionet
- Genes and Disease Program, Centre de Regulació Genòmica and CIBER en Epidemiología y Salud Pública, Barcelona, Spain
| | - Ioanna Konidari
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Melissa Y. Rayner-Evans
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Mary L. Baltos
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Harry H. Wright
- University of South Carolina School of Medicine, Columbia, SC, USA
| | - Ruth K. Abramson
- University of South Carolina School of Medicine, Columbia, SC, USA
| | - Eden R. Martin
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Michael L. Cuccaro
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - Margaret A. Pericak-Vance
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - John R. Gilbert
- John P. Hussman Institute for Human Genomics, University of Miami, 1501 NW 10th Avenue, Miami, FL 33136, USA
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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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Lintas C, Persico AM. Autistic phenotypes and genetic testing: state-of-the-art for the clinical geneticist. J Med Genet 2008; 46:1-8. [PMID: 18728070 PMCID: PMC2603481 DOI: 10.1136/jmg.2008.060871] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Autism spectrum disorders represent a group of developmental disorders with strong genetic underpinnings. Several cytogenetic abnormalities or de novo mutations able to cause autism have recently been uncovered. In this study, the literature was reviewed to highlight genotype-phenotype correlations between causal gene mutations or cytogenetic abnormalities and behavioural or morphological phenotypes. Based on this information, a set of practical guidelines is proposed to help clinical geneticists pursue targeted genetic testing for patients with autism whose clinical phenotype is suggestive of a specific genetic or genomic aetiology.
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Affiliation(s)
- C Lintas
- Laboratory of Molecular Psychiatry and Neurogenetics, University Campus Bio-Medico, Via Alvaro del Portillo 21, I-00128 Rome, Italy
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Skuse DH. Rethinking the nature of genetic vulnerability to autistic spectrum disorders. Trends Genet 2007; 23:387-95. [PMID: 17630015 DOI: 10.1016/j.tig.2007.06.003] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 05/24/2007] [Accepted: 06/22/2007] [Indexed: 12/28/2022]
Abstract
Autism is a common and genetically heterogeneous disorder, with an estimated heritability of >90%. Its specific underlying causes are largely unknown. Here, I propose that low levels of autistic vulnerability, reflected in social-cognitive processing differences, do not necessarily manifest in a behavioural phenotype but are usually compensated for during development. They are more likely to lead to a recognizable syndrome among individuals of low intelligence, who are male or have independent neurodevelopmental vulnerability owing to a wide range of gene mutations, chromosomal anomalies or environmental insults. Consequently, the apparent association between mental retardation and autistic syndromes is not because they usually have common causes, but rather because the presence of both features greatly increases the probability of clinical ascertainment.
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Affiliation(s)
- David H Skuse
- Behavioural and Brain Sciences Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
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Abstract
Rett syndrome (RS) is an X-linked neurodevelopmental disorder and the second most common cause of genetic mental retardation in females. Different mutations in MECP2 are found in up to 95% of typical cases of RS. This mainly neuronal expressed gene functions as a major transcription repressor. Extensive studies on girls who have RS and mouse models are aimed at finding main gene targets for MeCP2 protein and defining neuropathologic changes caused by its defects. Studies comparing autistic features in RS with idiopathic autism and mentally retarded patients are presented. Decreased dendritic arborization is common to RS and autism, leading to further research on similarities in pathogenesis, including MeCP2 protein levels in autistic brains and MeCP2 effects on genes connected to autism, like DLX5 and genes on 15q11-13 region. This area also is involved in Angelman syndrome, which has many similarities to RS. Despite these connections, MECP2 mutations in nonspecific autistic and mentally retarded populations are rare.
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Affiliation(s)
- Bruria Ben Zeev Ghidoni
- Pediatric Neurology Unit, Safra Pediatric Hospital, Sheba Medical Center, Ramat-Gan, Israel.
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