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Abstract
PURPOSE OF REVIEW Mammals have two complete sets of chromosomes, one from each parent with equal autosomal gene expression. Less than one percentage of human genes are imprinted or show expression from only one parent without changing gene structure, usually by DNA methylation, but reversible in gametogenesis. Many imprinted genes affect fetal growth and development accounting for several human disorders reviewed in this report. RECENT FINDINGS Disorders include Prader-Willi and Angelman syndromes, the first examples of imprinting errors in humans, chromosome 15q11.2-q13.3 duplication, Silver-Russell syndrome, Beckwith-Weidemann syndrome, GNAS gene-related inactivation disorders (e.g. Albright hereditary osteodystrophy), uniparental chromosome 14 disomy, chromosome 6q24-related transient neonatal diabetes mellitus, parent of origin effects in 15q11.2 BP1-BP2 deletion (Burnside-Butler) syndrome and 15q11-q13 single gene imprinted disorders. SUMMARY Periconceptional and intrauterine life can be influenced by environmental factors and nutrition impacting DNA methylation. This process not only alters development of the fetus, but pregnancy complications may result from large fetal size. Epigenetic processes control imprinted gene functions and regulation with susceptibility to diseases as described. A better understanding of these processes will impact on care and treatment of affected individuals.
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Affiliation(s)
- Merlin G Butler
- Departments of Psychiatry & Behavioral Sciences and Pediatrics, University of Kansas Medical Center, Kansas City, Kansas, USA
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Abstract
Epigenetic marks are modifications of DNA and histones. They are considered to be permanent within a single cell during development, and are heritable across cell division. Programming of neurons through epigenetic mechanisms is believed to be critical in neural development. Disruption or alteration in this process causes an array of neurodevelopmental disorders, including autism spectrum disorders (ASDs). Recent studies have provided evidence for an altered epigenetic landscape in ASDs and demonstrated the central role of epigenetic mechanisms in their pathogenesis. Many of the genes linked to the ASDs encode proteins that are involved in transcriptional regulation and chromatin remodeling. In this review we highlight selected neurodevelopmental disorders in which epigenetic dysregulation plays an important role. These include Rett syndrome, fragile X syndrome, Prader-Willi syndrome, Angelman syndrome, and Kabuki syndrome. For each of these disorders, we discuss how advances in our understanding of epigenetic mechanisms may lead to novel therapeutic approaches.
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Affiliation(s)
- Sampathkumar Rangasamy
- />Developmental Neurogenetics Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
| | | | - Vinodh Narayanan
- />Developmental Neurogenetics Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
- />Developmental Neurogenetic Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
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van Bon BWM, Koolen DA, Brueton L, McMullan D, Lichtenbelt KD, Adès LC, Peters G, Gibson K, Novara F, Pramparo T, Bernardina BD, Zoccante L, Balottin U, Piazza F, Pecile V, Gasparini P, Guerci V, Kets M, Pfundt R, de Brouwer AP, Veltman JA, de Leeuw N, Wilson M, Antony J, Reitano S, Luciano D, Fichera M, Romano C, Brunner HG, Zuffardi O, de Vries BBA. The 2q23.1 microdeletion syndrome: clinical and behavioural phenotype. Eur J Hum Genet 2010; 18:163-70. [PMID: 19809484 PMCID: PMC2987180 DOI: 10.1038/ejhg.2009.152] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 09/02/2009] [Accepted: 09/02/2009] [Indexed: 11/08/2022] Open
Abstract
Six submicroscopic deletions comprising chromosome band 2q23.1 in patients with severe mental retardation (MR), short stature, microcephaly and epilepsy have been reported, suggesting that haploinsufficiency of one or more genes in the 2q23.1 region might be responsible for the common phenotypic features in these patients. In this study, we report the molecular and clinical characterisation of nine new 2q23.1 deletion patients and a clinical update on two previously reported patients. All patients were mentally retarded with pronounced speech delay and additional abnormalities including short stature, seizures, microcephaly and coarse facies. The majority of cases presented with stereotypic repetitive behaviour, a disturbed sleep pattern and a broad-based gait. These features led to the initial clinical impression of Angelman, Rett or Smith-Magenis syndromes in several patients. The overlapping 2q23.1 deletion region in all 15 patients comprises only one gene, namely, MBD5. Interestingly, MBD5 is a member of the methyl CpG-binding domain protein family, which also comprises MECP2, mutated in Rett's syndrome. Another gene in the 2q23.1 region, EPC2, was deleted in 12 patients who had a broader phenotype than those with a deletion of MBD5 only. EPC2 is a member of the polycomb protein family, involved in heterochromatin formation and might be involved in causing MR. Patients with a 2q23.1 microdeletion present with a variable phenotype and the diagnosis should be considered in mentally retarded children with coarse facies, seizures, disturbed sleeping patterns and additional specific behavioural problems.
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Affiliation(s)
- Bregje WM van Bon
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - David A Koolen
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Louise Brueton
- Division of Medical and Molecular Genetics, University of Birmingham, Birmingham, UK
| | - Dominic McMullan
- Division of Medical and Molecular Genetics, University of Birmingham, Birmingham, UK
| | - Klaske D Lichtenbelt
- Department of Medical Genetics, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Lesley C Adès
- Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia
| | - Gregory Peters
- Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia
| | - Kate Gibson
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Queensland, Australia
| | | | | | | | - Leonardo Zoccante
- Child Neuropsychiatry Unit, University of Verona, Policlinico G.B. Rossi, Verona, Italy
| | - Umberto Balottin
- Child Neuropsychiatry Unit, University of Verona, Policlinico G.B. Rossi, Verona, Italy
| | - Fausta Piazza
- Child Neuropsychiatry Unit, University of Verona, Policlinico G.B. Rossi, Verona, Italy
| | - Vanna Pecile
- Cytogenetics Laboratory, IRCCS Burlo Garafano, Trieste, Italy
| | - Paolo Gasparini
- Medical Genetics, IRCCS Burlo Garofolo, University of Trieste, Trieste, Italy
| | - Veronica Guerci
- Medical Genetics, IRCCS Burlo Garofolo, University of Trieste, Trieste, Italy
| | - Marleen Kets
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Rolph Pfundt
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Arjan P de Brouwer
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Joris A Veltman
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Nicole de Leeuw
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Meredith Wilson
- Department of Clinical Genetics, Children's Hospital at Westmead, Sydney, Australia
| | - Jayne Antony
- Department of Clinical Genetics, Children's Hospital at Westmead, Sydney, Australia
| | - Santina Reitano
- Pediatrics and Medical Genetics, I.R.C.C.S. Associazione Oasi Maria Santissima, Troina, Italy
| | - Daniela Luciano
- Laboratory of Genetic Diagnosis, I.R.C.C.S. Associazione Oasi Maria Santissima, Troina, Italy
| | - Marco Fichera
- Laboratory of Genetic Diagnosis, I.R.C.C.S. Associazione Oasi Maria Santissima, Troina, Italy
| | - Corrado Romano
- Pediatrics and Medical Genetics, I.R.C.C.S. Associazione Oasi Maria Santissima, Troina, Italy
| | - Han G Brunner
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Orsetta Zuffardi
- Genetica Medica, Università di Pavia, Pavia, Italy
- IRCCS Fondazione C. Mondino, Pavia, Italy
| | - Bert BA de Vries
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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