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Ozonoff S, Iosif AM. Changing conceptualizations of regression: What prospective studies reveal about the onset of autism spectrum disorder. Neurosci Biobehav Rev 2019; 100:296-304. [PMID: 30885812 PMCID: PMC6451681 DOI: 10.1016/j.neubiorev.2019.03.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 02/12/2019] [Accepted: 03/14/2019] [Indexed: 12/23/2022]
Abstract
Until the last decade, studies of the timing of early symptom emergence in autism spectrum disorder (ASD) relied upon retrospective methods. Recent investigations, however, are raising significant questions about the accuracy and validity of such data. Questions about when and how behavioral signs of autism emerge may be better answered through prospective studies, in which infants are enrolled near birth and followed longitudinally until the age at which ASD can be confidently diagnosed or ruled out. This review summarizes the results of recent studies that utilized prospective methods to study infants at high risk of developing ASD due to family history. Collectively, prospective studies demonstrate that the onset of ASD involves declines in the rates of key social and communication behaviors during the first years of life for most children. This corpus of literature suggests that regressive onset patterns occur much more frequently than previously recognized and may be the rule rather than the exception.
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Affiliation(s)
- Sally Ozonoff
- Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California - Davis, 2825 50th Street, Sacramento CA, 95817, USA.
| | - Ana-Maria Iosif
- Department of Public Health Sciences, University of California - Davis, Medical Sciences 1C, Davis CA, 95616, USA.
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2
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Shiohama T, Levman J, Takahashi E. Surface- and voxel-based brain morphologic study in Rett and Rett-like syndrome with MECP2 mutation. Int J Dev Neurosci 2019; 73:83-88. [PMID: 30690146 DOI: 10.1016/j.ijdevneu.2019.01.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 12/20/2018] [Accepted: 01/23/2019] [Indexed: 12/21/2022] Open
Abstract
Rett syndrome (RTT) is a rare congenital disorder which in most cases (95%) is caused by methyl-CpG binding protein 2 (MECP2) mutations. RTT is characterized by regression in global development, epilepsy, autistic features, acquired microcephaly, habitual hand clapping, loss of purposeful hand skills, and autonomic dysfunctions. Although the literature has demonstrated decreased volumes of the cerebrum, cerebellum, and the caudate nucleus in RTT patients, surface-based brain morphology including cortical thickness and cortical gyrification analyses are lacking in RTT. We present quantitative surface- and voxel-based morphological measurements in young children with RTT and Rett-like syndrome (RTT-l) with MECP2 mutations. The 8 structural T1-weighted MR images were obtained from 7 female patients with MECP2 mutations (3 classic RTT, 2 variant RTT, and 2 RTT-l) (mean age 5.2 [standard deviation 3.3] years old). Our analyses demonstrated decreased total volumes of the cerebellum in RTT/RTT-l compared to gender- and age-matched controls (t (22)=-2.93, p = .008, Cohen's d = 1.27). In contrast, global cerebral cortical surface areas, global/regional cortical thicknesses, the degree of global gyrification, and global/regional gray and white matter volumes were not statistically significantly different between the two groups. Our findings, as well as literature findings, suggest that early brain abnormalities associated with RTT/RTT-l (with MECP2 mutations) can be detected as regionally decreased cerebellar volumes. Decreased cerebellar volume may be helpful for understanding the etiology of RTT/RTT-l.
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Affiliation(s)
- Tadashi Shiohama
- Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA; Department of Pediatrics, Chiba University Hospital, Inohana 1-8-1, Chiba-shi, Chiba, 2608670, Japan.
| | - Jacob Levman
- Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA; Department of Mathematics, Statistics and Computer Science, St. Francis Xavier University, 2323 Notre Dame Ave, Antigonish, Nova Scotia, B2G 2W5, Canada
| | - Emi Takahashi
- Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
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Chen LF, Zhou AS, West AE. Transcribing the connectome: roles for transcription factors and chromatin regulators in activity-dependent synapse development. J Neurophysiol 2017; 118:755-770. [PMID: 28490640 DOI: 10.1152/jn.00067.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 05/09/2017] [Accepted: 05/09/2017] [Indexed: 12/21/2022] Open
Abstract
The wiring of synaptic connections in the developing mammalian brain is shaped by both intrinsic and extrinsic signals. One point where these regulatory pathways converge is via the sensory experience-dependent regulation of new gene transcription. Recent studies have elucidated a number of molecular mechanisms that allow nuclear transcription factors and chromatin regulatory proteins to encode aspects of specificity in experience-dependent synapse development. Here we review the evidence for the transcriptional mechanisms that sculpt activity-dependent aspects of synaptic connectivity during postnatal development and discuss how disruption of these processes is associated with aberrant brain development in autism and intellectual disability.
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Affiliation(s)
- Liang-Fu Chen
- Department of Neurobiology, Duke University, Durham, North Carolina
| | - Allen S Zhou
- Department of Neurobiology, Duke University, Durham, North Carolina
| | - Anne E West
- Department of Neurobiology, Duke University, Durham, North Carolina
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4
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Vrečar I, Innes J, Jones EA, Kingston H, Reardon W, Kerr B, Clayton-Smith J, Douzgou S. Further Clinical Delineation of the MEF2C Haploinsufficiency Syndrome: Report on New Cases and Literature Review of Severe Neurodevelopmental Disorders Presenting with Seizures, Absent Speech, and Involuntary Movements. J Pediatr Genet 2017; 6:129-141. [PMID: 28794905 DOI: 10.1055/s-0037-1601335] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 02/16/2017] [Indexed: 01/24/2023]
Abstract
Mutations in the MEF2C ( myocyte enhancer factor 2 ) gene have been established as a cause for an intellectual disability syndrome presenting with seizures, absence of speech, stereotypic movements, hypotonia, and limited ambulation. Phenotypic overlap with Rett's and Angelman's syndromes has been noted. Following the first reports of 5q14.3q15 microdeletions encompassing the MEF2C gene, further cases with point mutations and partial gene deletions of the MEF2C gene have been described. We present the clinical phenotype of our cohort of six patients with MEF2C mutations and compare our findings with previously reported patients as well as with a growing number of genetic conditions presenting with a severe neurodevelopmental, Rett-like, phenotype. We aim to add to the current knowledge of the natural history of the "MEF2C haploinsufficiency syndrome" as well as of the differential diagnosis, clinical management, and genetic counseling in this diagnostically challenging group of patients.
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Affiliation(s)
- Irena Vrečar
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Clinical Institute of Medical Genetics, University Medical Centre of Ljubljana, Ljubljana, Slovenia
| | - Josie Innes
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom
| | - Elizabeth A Jones
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Division of Evolution and Genomic Sciences, University of Manchester, School of Biological Sciences, Manchester, United Kingdom
| | - Helen Kingston
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Division of Evolution and Genomic Sciences, University of Manchester, School of Biological Sciences, Manchester, United Kingdom
| | - William Reardon
- Department of Clinical Genetics, Our Lady's Children Hospital Crumlin, Dublin, Ireland
| | - Bronwyn Kerr
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Division of Evolution and Genomic Sciences, University of Manchester, School of Biological Sciences, Manchester, United Kingdom
| | - Jill Clayton-Smith
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Division of Evolution and Genomic Sciences, University of Manchester, School of Biological Sciences, Manchester, United Kingdom
| | - Sofia Douzgou
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Academic Health Sciences Centre, Manchester, United Kingdom.,Division of Evolution and Genomic Sciences, University of Manchester, School of Biological Sciences, Manchester, United Kingdom
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Magdalon J, Sánchez-Sánchez SM, Griesi-Oliveira K, Sertié AL. Dysfunctional mTORC1 Signaling: A Convergent Mechanism between Syndromic and Nonsyndromic Forms of Autism Spectrum Disorder? Int J Mol Sci 2017; 18:ijms18030659. [PMID: 28335463 PMCID: PMC5372671 DOI: 10.3390/ijms18030659] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 03/13/2017] [Accepted: 03/14/2017] [Indexed: 12/28/2022] Open
Abstract
Whereas autism spectrum disorder (ASD) exhibits striking heterogeneity in genetics and clinical presentation, dysfunction of mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway has been identified as a molecular feature common to several well-characterized syndromes with high prevalence of ASD. Additionally, recent findings have also implicated mTORC1 signaling abnormalities in a subset of nonsyndromic ASD, suggesting that defective mTORC1 pathway may be a potential converging mechanism in ASD pathology across different etiologies. However, the mechanistic evidence for a causal link between aberrant mTORC1 pathway activity and ASD neurobehavioral features varies depending on the ASD form involved. In this review, we first discuss six monogenic ASD-related syndromes, including both classical and potentially novel mTORopathies, highlighting their contribution to our understanding of the neurobiological mechanisms underlying ASD, and then we discuss existing evidence suggesting that aberrant mTORC1 signaling may also play a role in nonsyndromic ASD.
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Affiliation(s)
- Juliana Magdalon
- Hospital Israelita Albert Einstein, Centro de Pesquisa Experimental, São Paulo 05652-900, Brazil.
| | - Sandra M Sánchez-Sánchez
- Hospital Israelita Albert Einstein, Centro de Pesquisa Experimental, São Paulo 05652-900, Brazil.
- Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brazil.
| | - Karina Griesi-Oliveira
- Hospital Israelita Albert Einstein, Centro de Pesquisa Experimental, São Paulo 05652-900, Brazil.
| | - Andréa L Sertié
- Hospital Israelita Albert Einstein, Centro de Pesquisa Experimental, São Paulo 05652-900, Brazil.
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Leonard H, Cobb S, Downs J. Clinical and biological progress over 50 years in Rett syndrome. Nat Rev Neurol 2016; 13:37-51. [PMID: 27934853 DOI: 10.1038/nrneurol.2016.186] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the 50 years since Andreas Rett first described the syndrome that came to bear his name, and is now known to be caused by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, a compelling blend of astute clinical observations and clinical and laboratory research has substantially enhanced our understanding of this rare disorder. Here, we document the contributions of the early pioneers in Rett syndrome (RTT) research, and describe the evolution of knowledge in terms of diagnostic criteria, clinical variation, and the interplay with other Rett-related disorders. We provide a synthesis of what is known about the neurobiology of MeCP2, considering the lessons learned from both cell and animal models, and how they might inform future clinical trials. With a focus on the core criteria, we examine the relationships between genotype and clinical severity. We review current knowledge about the many comorbidities that occur in RTT, and how genotype may modify their presentation. We also acknowledge the important drivers that are accelerating this research programme, including the roles of research infrastructure, international collaboration and advocacy groups. Finally, we highlight the major milestones since 1966, and what they mean for the day-to-day lives of individuals with RTT and their families.
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Affiliation(s)
- Helen Leonard
- Telethon Kids Institute, 100 Roberts Road, Subiaco, Perth, Western Australia 6008, Australia
| | - Stuart Cobb
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
| | - Jenny Downs
- Telethon Kids Institute, 100 Roberts Road, Subiaco, Perth, Western Australia 6008, Australia
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Sheen V, Valencia IM, Torres AR. Atypical features in MECP2 P152R-associated Rett syndrome. Pediatr Neurol 2013; 49:124-6. [PMID: 23859859 DOI: 10.1016/j.pediatrneurol.2012.12.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/31/2012] [Indexed: 10/26/2022]
Abstract
BACKGROUND Rett syndrome is a neurodevelopmental disorder that occurs in individuals with a mutation in the X-linked methyl-CpG-binding protein 2 (2MECP2) gene. 2MECP2 mutations produce a high degree of variability in the clinical phenotypes including the classic Rett features of head growth deceleration, psychomotor regression, deviant communicative ability, hand stereotypes, autonomic dysfunction, and seizures. Atypical forms of Rett such as those with preserved speech do not follow these characteristics. PATIENT We report a 9-year-old girl with atypical Rett (macrocephaly, preserved speech, and psychiatric manifestations) with a 2MECP2 (P152R) mutation that generally is not associated with these clinical signs. CONCLUSION This case broadens the genotype-phenotype correlation between the P152R mutation 2MECP2-associated Rett syndrome.
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Affiliation(s)
- Volney Sheen
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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8
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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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9
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Na ES, Nelson ED, Kavalali ET, Monteggia LM. The impact of MeCP2 loss- or gain-of-function on synaptic plasticity. Neuropsychopharmacology 2013; 38:212-9. [PMID: 22781840 PMCID: PMC3521965 DOI: 10.1038/npp.2012.116] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Methyl-CpG-binding protein 2 (MeCP2) is a transcriptional regulator of gene expression that is an important epigenetic factor in the maintenance and development of the central nervous system. The neurodevelopmental disorders Rett syndrome and MECP2 duplication syndrome arise from loss-of-function and gain-of-function alterations in MeCP2 expression, respectively. Several animal models have been developed to recapitulate the symptoms of Rett syndrome and MECP2 duplication syndrome. Cell morphology, neurotransmission, and cellular processes that support learning and memory are compromised as a result of MeCP2 loss- or gain-of-function. Interestingly, loss-of-MeCP2 function and MeCP2 overexpression trigger diametrically opposite changes in synaptic transmission. These findings indicate that the precise regulation of MeCP2 expression is a key requirement for the maintenance of synaptic and neuronal homeostasis and underscore its importance in central nervous system function. This review highlights the functional role of MeCP2 in the brain as a regulator of synaptic and neuronal plasticity as well as its etiological role in the development of Rett syndrome and MECP2 duplication syndrome.
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Affiliation(s)
- Elisa S Na
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Erika D Nelson
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ege T Kavalali
- Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Lisa M Monteggia
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Psychiatry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9070, USA, Tel: +1 214 648 5548, Fax: +1 214 648 4947, E-mail:
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Tarquinio DC, Motil KJ, Hou W, Lee HS, Glaze DG, Skinner SA, Neul JL, Annese F, McNair L, Barrish JO, Geerts SP, Lane JB, Percy AK. Growth failure and outcome in Rett syndrome: specific growth references. Neurology 2012; 79:1653-61. [PMID: 23035069 DOI: 10.1212/wnl.0b013e31826e9a70] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVES Prominent growth failure typifies Rett syndrome (RTT). Our aims were to 1) develop RTT growth charts for clinical and research settings, 2) compare growth in children with RTT with that of unaffected children, and 3) compare growth patterns among RTT genotypes and phenotypes. METHODS A cohort of the RTT Rare Diseases Clinical Research Network observational study participants was recruited, and cross-sectional and longitudinal growth data and comprehensive clinical information were collected. A reliability study confirmed interobserver consistency. Reference curves for height, weight, head circumference, and body mass index (BMI), generated using a semiparametric model with goodness-of-fit tests, were compared with normative values using Student's t test adjusted for multiple comparisons. Genotype and phenotype subgroups were compared using analysis of variance and linear regression. RESULTS Growth charts for classic and atypical RTT were created from 9,749 observations of 816 female participants. Mean growth in classic RTT decreased below that for the normative population at 1 month for head circumference, 6 months for weight, and 17 months for length. Mean BMI was similar in those with RTT and the normative population. Pubertal increases in height and weight were absent in classic RTT. Classic RTT was associated with more growth failure than atypical RTT. In classic RTT, poor growth was associated with worse development, higher disease severity, and certain MECP2 mutations (pre-C-terminal truncation, large deletion, T158M, R168X, R255X, and R270X). CONCLUSIONS RTT-specific growth references will allow effective screening for disease and treatment monitoring. Growth failure occurs less frequently in girls with RTT with better development, less morbidity typically associated with RTT, and late truncation mutations.
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Abstract
Rett syndrome is one of the most common causes of complex disability in girls. It is characterized by early neurological regression that severely affects motor, cognitive and communication skills, by autonomic dysfunction and often a seizure disorder. It is a monogenic X-linked dominant neurodevelopmental disorder related to mutation in MECP2, which encodes the methyl-CpG-binding protein MeCP2. There are several mouse models either based on conditional knocking out of the Mecp2 gene or on a truncating mutation. We discuss the clinical aspects with special emphasis on the behavioral phenotype and we review current perspectives in clinical management alongside with perspectives in altering gene expression.
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Affiliation(s)
- E E J Smeets
- Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
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12
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A model for neural development and treatment of Rett syndrome using human induced pluripotent stem cells. Cell 2010; 143:527-39. [PMID: 21074045 DOI: 10.1016/j.cell.2010.10.016] [Citation(s) in RCA: 961] [Impact Index Per Article: 68.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 08/04/2010] [Accepted: 10/08/2010] [Indexed: 12/14/2022]
Abstract
Autism spectrum disorders (ASD) are complex neurodevelopmental diseases in which different combinations of genetic mutations may contribute to the phenotype. Using Rett syndrome (RTT) as an ASD genetic model, we developed a culture system using induced pluripotent stem cells (iPSCs) from RTT patients' fibroblasts. RTT patients' iPSCs are able to undergo X-inactivation and generate functional neurons. Neurons derived from RTT-iPSCs had fewer synapses, reduced spine density, smaller soma size, altered calcium signaling and electrophysiological defects when compared to controls. Our data uncovered early alterations in developing human RTT neurons. Finally, we used RTT neurons to test the effects of drugs in rescuing synaptic defects. Our data provide evidence of an unexplored developmental window, before disease onset, in RTT syndrome where potential therapies could be successfully employed. Our model recapitulates early stages of a human neurodevelopmental disease and represents a promising cellular tool for drug screening, diagnosis and personalized treatment.
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Lewis JD, Elman JL. Growth-related neural reorganization and the autism phenotype: a test of the hypothesis that altered brain growth leads to altered connectivity. Dev Sci 2008; 11:135-55. [PMID: 18171375 PMCID: PMC2706588 DOI: 10.1111/j.1467-7687.2007.00634.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Theoretical considerations, and findings from computational modeling, comparative neuroanatomy and developmental neuroscience, motivate the hypothesis that a deviant brain growth trajectory will lead to deviant patterns of change in cortico-cortical connectivity. Differences in brain size during development will alter the relative cost and effectiveness of short- and long-distance connections, and should thus impact the growth and retention of connections. Reduced brain size should favor long-distance connectivity; brain overgrowth should favor short-distance connectivity; and inconsistent deviations from the normal growth trajectory - as occurs in autism - should result in potentially disruptive changes to established patterns of functional and physical connectivity during development. To explore this hypothesis, neural networks which modeled inter-hemispheric interaction were grown at the rate of either typically developing children or children with autism. The influence of the length of the inter-hemispheric connections was analyzed at multiple developmental time-points. The networks that modeled autistic growth were less affected by removal of the inter-hemispheric connections than those that modeled normal growth - indicating a reduced reliance on long-distance connections - for short response times, and this difference increased substantially at approximately 24 simulated months of age. The performance of the networks showed a corresponding decline during development. And direct analysis of the connection weights showed a parallel reduction in connectivity. These modeling results support the hypothesis that the deviant growth trajectory in autism spectrum disorders may lead to a disruption of established patterns of functional connectivity during development, with potentially negative behavioral consequences, and a subsequent reduction in physical connectivity. The results are discussed in relation to the growing body of evidence of reduced functional and structural connectivity in autism, and in relation to the behavioral phenotype, particularly the developmental aspects.
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Affiliation(s)
- John D Lewis
- Department of Cognitive Science, University of California at San Diego, USA.
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14
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Nectoux J, Girard B, Bahi-Buisson N, Prieur F, Afenjar A, Rosas-Vargas H, Chelly J, Bienvenu T. Netrin G1 mutations are an uncommon cause of atypical Rett syndrome with or without epilepsy. Pediatr Neurol 2007; 37:270-4. [PMID: 17903671 DOI: 10.1016/j.pediatrneurol.2007.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Revised: 04/25/2007] [Accepted: 06/01/2007] [Indexed: 11/27/2022]
Abstract
Mutations in the methyl-cytosine-phosphate-guanosine dinucleotide (CpG) binding protein 2 gene are identified in up to 90% of patients with classic Rett syndrome. However, the lack of methyl-CpG binding protein 2 mutations in a small group of classic Rett syndrome cases, and the low frequency of these mutations in atypical Rett syndrome patients, suggest that other gene defects may play a role in this disorder. One report described a patient with atypical Rett syndrome who presented with early epilepsy and a de novo translocation which disrupted the Netrin G1 gene. This study tested a sample of 91 female patients with a clinically heterogeneous phenotype ranging from encephalopathy with epilepsy to atypical Rett syndrome without epilepsy for mutations in the Netrin G1 gene, to evaluate its involvement in this condition. Nine sequence variations (including six novel variations) were identified, all of which were unlikely to be pathogenic. One was a novel C to G transversion, resulting in a p.Leu537Val amino-acid substitution in one patient. The same substitution was detected in the asymptomatic mother, suggesting an absence of biological significance. Our study suggests that Netrin G1 is not involved in atypical Rett syndrome or in unexplained encephalopathy with epilepsy, but in specific forms to be delineated better in the future.
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Affiliation(s)
- Juliette Nectoux
- Assistance Publique-Hopitaux de Paris, Laboratoire de Biochimie et Génétique Moléculaires, Hôpital Cochin, France
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Oexle K, Thamm-Mücke B, Mayer T, Tinschert S. Macrocephalic mental retardation associated with a novel C-terminal MECP2 frameshift deletion. Eur J Pediatr 2005; 164:154-7. [PMID: 15558314 DOI: 10.1007/s00431-004-1583-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 10/19/2004] [Accepted: 10/20/2004] [Indexed: 11/30/2022]
Abstract
UNLABELLED We report a novel C-terminal MECP2 frameshift deletion (1135_1142delCCCGTG CC) in a 19-year-old woman with mental retardation and epilepsy. Preservation of language capabilities, purposeful hand use and sufficient locomotion implied an atypical variant of Rett syndrome (OMIM 312750). Occipito-frontal head circumference was large at birth (36 cm; SDS 1.7) and increased until adulthood (58.5 cm; SDS 2.3). CONCLUSION Our observation indicates that head size and head growth are of limited reliability in the diagnosis of MECP2-associated phenotypes.
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Affiliation(s)
- Konrad Oexle
- Institut für Klinische Genetik, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
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Luikenhuis S, Giacometti E, Beard CF, Jaenisch R. Expression of MeCP2 in postmitotic neurons rescues Rett syndrome in mice. Proc Natl Acad Sci U S A 2004; 101:6033-8. [PMID: 15069197 PMCID: PMC395918 DOI: 10.1073/pnas.0401626101] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in MECP2 are the cause of Rett syndrome (RTT) in humans, a neurodevelopmental disorder that affects mainly girls. MeCP2 is a protein that binds CpG dinucleotides and is thought to act as a global transcriptional repressor. It is highly expressed in neurons, but not in glia, of the postnatal brain. The timing of MeCP2 activation correlates with the maturation of the central nervous system, and recent reports suggest that MeCP2 may be involved in the formation of synaptic contacts and may function in activity-dependent neuronal gene expression. Deletion or targeted mutation of Mecp2 in mice leads to a Rett-like phenotype. Selective mutation of Mecp2 in postnatal neurons leads to a similar, although delayed, phenotype, suggesting that MeCP2 plays a role in postmitotic neurons. Here we test the hypothesis that the symptoms of RTT are exclusively caused by a neuronal MeCP2 deficiency by placing Mecp2 expression under the control of a neuron-specific promoter. Expression of the Mecp2 transgene in postmitotic neurons resulted in symptoms of severe motor dysfunction. Transgene expression in Mecp2 mutant mice, however, rescued the RTT phenotype.
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Affiliation(s)
- Sandra Luikenhuis
- Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, MA 02142, USA
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