251
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Webb T, Maina EN, Soni S, Whittington J, Boer H, Clarke D, Holland A. In search of the psychosis gene in people with Prader-Willi syndrome. Am J Med Genet A 2008; 146A:843-53. [DOI: 10.1002/ajmg.a.32212] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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252
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Imprinted Genes, Postnatal Adaptations and Enduring Effects on Energy Homeostasis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 626:41-61. [DOI: 10.1007/978-0-387-77576-0_4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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253
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Wan LB, Bartolomei MS. Regulation of imprinting in clusters: noncoding RNAs versus insulators. ADVANCES IN GENETICS 2008; 61:207-23. [PMID: 18282507 DOI: 10.1016/s0065-2660(07)00007-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Genomic imprinting is an epigenetic mechanism of transcriptional regulation through which expression of a subset of mammalian genes is restricted to one parental allele. An intriguing characteristic of imprinted genes is that they often cluster in megabase-sized chromosomal domains, indicating that domain-specific mechanisms regulate imprinting. Detailed study of the known imprinted domains has revealed a number of common characteristics. First, all clusters have an imprinting control region (ICR) that is typically 1-5 kb in size and differentially methylated, and that regulates imprinting across the entire domain. Second, the clusters have at least one noncoding RNA (ncRNA) that is usually expressed from the maternal allele and multiple paternally expressed protein-coding genes. Finally, the clusters are likely regulated by one of two mechanisms, transcription of a long ncRNA that silences expression of protein-coding genes bidirectionally in cis and blocking of shared enhancer elements by CCCTC binding factor (CTCF) binding insulators. More recent experiments may even suggest that both mechanisms operate at some clusters. In this chapter, we will describe what is known about imprinting at five well-studied imprinted loci and highlight some of the critical experiments that are required before a full understanding of imprinting mechanisms is achieved.
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Affiliation(s)
- Le-Ben Wan
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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254
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Newschaffer CJ, Croen LA, Daniels J, Giarelli E, Grether JK, Levy SE, Mandell DS, Miller LA, Pinto-Martin J, Reaven J, Reynolds AM, Rice CE, Schendel D, Windham GC. The epidemiology of autism spectrum disorders. Annu Rev Public Health 2007; 28:235-58. [PMID: 17367287 DOI: 10.1146/annurev.publhealth.28.021406.144007] [Citation(s) in RCA: 604] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autism spectrum disorders (ASDs) are complex, lifelong, neurodevelopmental conditions of largely unknown cause. They are much more common than previously believed, second in frequency only to mental retardation among the serious developmental disorders. Although a heritable component has been demonstrated in ASD etiology, putative risk genes have yet to be identified. Environmental risk factors may also play a role, perhaps via complex gene-environment interactions, but no specific exposures with significant population effects are known. A number of endogenous biomarkers associated with autism risk have been investigated, and these may help identify significant biologic pathways that, in turn, will aid in the discovery of specific genes and exposures. Future epidemiologic research should focus on expanding population-based descriptive data on ASDs, exploring candidate risk factors in large well-designed studies incorporating both genetic and environmental exposure data and addressing possible etiologic heterogeneity in studies that can stratify case groups and consider alternate endophenotypes.
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Affiliation(s)
- Craig J Newschaffer
- Department of Epidemiology and Biostatistics, Drexel University School of Public Health, Philadelphia, PA 19102, USA.
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255
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Wang J, Valo Z, Smith D, Singer-Sam J. Monoallelic expression of multiple genes in the CNS. PLoS One 2007; 2:e1293. [PMID: 18074017 PMCID: PMC2100171 DOI: 10.1371/journal.pone.0001293] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Accepted: 11/11/2007] [Indexed: 11/19/2022] Open
Abstract
The inheritance pattern of a number of major genetic disorders suggests the possible involvement of genes that are expressed from one allele and silent on the other, but such genes are difficult to detect. Since DNA methylation in regulatory regions is often a mark of gene silencing, we modified existing microarray-based assays to detect both methylated and unmethylated DNA sequences in the same sample, a variation we term the MAUD assay. We probed a 65 Mb region of mouse Chr 7 for gene-associated sequences that show two distinct DNA methylation patterns in the mouse CNS. Selected genes were then tested for allele-specific expression in clonal neural stem cell lines derived from reciprocal F(1) (C57BL/6xJF1) hybrid mice. In addition, using a separate approach, we directly analyzed allele-specific expression of a group of genes interspersed within clusters of OlfR genes, since the latter are subject to allelic exclusion. Altogether, of the 500 known genes in the chromosomal region surveyed, five show monoallelic expression, four identified by the MAUD assay (Agc1, p (pink-eyed dilution), P4ha3 and Thrsp), and one by its proximity to OlfR genes (Trim12). Thrsp (thyroid hormone responsive SPOT14 homolog) is expressed in hippocampus, but the human protein homolog, S14, has also been implicated in aggressive breast cancer. Monoallelic expression of the five genes is not coordinated at a chromosome-wide level, but rather regulated at individual loci. Taken together, our results suggest that at least 1% of previously untested genes are subject to allelic exclusion, and demonstrate a dual approach to expedite their identification.
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Affiliation(s)
- Jinhui Wang
- Division of Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
- Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
| | - Zuzana Valo
- Division of Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
- Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
| | - David Smith
- Division of Information Sciences, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
| | - Judith Singer-Sam
- Division of Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
- Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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256
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Pigeyre M, Romon M. Obésités génétiques. ANNALES D'ENDOCRINOLOGIE 2007; 68:430-7. [DOI: 10.1016/j.ando.2007.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Revised: 09/07/2007] [Accepted: 09/17/2007] [Indexed: 11/26/2022]
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257
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Rauch J, Knoch TA, Solovei I, Teller K, Stein S, Buiting K, Horsthemke B, Langowski J, Cremer T, Hausmann M, Cremer C. Light optical precision measurements of the active and inactive Prader-Willi syndrome imprinted regions in human cell nuclei. Differentiation 2007; 76:66-82. [PMID: 18039333 DOI: 10.1111/j.1432-0436.2007.00237.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite the major advancements during the last decade with respect to both knowledge of higher order chromatin organization in the cell nucleus and the elucidation of epigenetic mechanisms of gene control, the true three-dimensional (3D) chromatin structure of endogenous active and inactive gene loci is not known. The present study was initiated as an attempt to close this gap. As a model case, we compared the chromatin architecture between the genetically active and inactive domains of the imprinted Prader-Willi syndrome (PWS) locus in human fibroblast and lymphoblastoid cell nuclei by 3D fluorescence in situ hybridization and quantitative confocal laser scanning microscopy. The volumes and 3D compactions of identified maternal and paternal PWS domains were determined in stacks of light optical serial sections using a novel threshold-independent approach. Our failure to detect volume and compaction differences indicates that possible differences are below the limits of light optical resolution. To overcome this limitation, spectral precision distance microscopy, a method of localization microscopy at the nanometer scale, was used to measure 3D distances between differentially labeled probes located both within the PWS region and in its neighborhood. This approach allows the detection of intranuclear differences between 3D distances down to about 70-90 nm, but again did not reveal clearly detectable differences between active and inactive PWS domains. Despite this failure, a comparison of the experimental 3D distance measurements with computer simulations of chromatin folding strongly supports a non-random higher order chromatin configuration of the PWS locus and argues against 3D configurations based on giant chromatin loops. Our results indicate that the search for differences between endogenous active and inactive PWS domains must be continued at still smaller scales than hitherto possible with conventional light microscopic procedures. The possibilities to achieve this goal are discussed.
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Affiliation(s)
- Joachim Rauch
- Kirchhoff Institute of Physics, University of Heidelberg, Im Neuenheimer Feld 227, D-69120 Heidelberg, Germany
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258
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Abstract
In a simplified view, members of the HECT E3 family have a modular structure consisting of the C-terminal HECT domain, which is catalytically involved in the attachment of ubiquitin to substrate proteins, and N-terminal extensions of variable length and sequence that mediate the substrate specificity of the respective HECT E3. Although the physiologically relevant substrates of most HECT E3s have remained elusive, it is becoming increasingly clear that HECT E3s play an important role in sporadic and hereditary human diseases including cancer, cardiovascular (Liddle's syndrome) and neurological (Angelman syndrome) disorders, and/or in disease-relevant processes including bone homeostasis, immune response and retroviral budding. Thus, molecular approaches to target the activity of distinct HECT E3s, regulators thereof, and/or of HECT E3 substrates could prove valuable in the treatment of the respective diseases. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; ).
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Affiliation(s)
- Martin Scheffner
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
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259
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Saitoh S, Hosoki K, Takano K, Tonoki H. Mosaic paternally derived inv dup(15) may partially rescue the Prader-Willi syndrome phenotype with uniparental disomy. Clin Genet 2007; 72:378-80. [PMID: 17850637 DOI: 10.1111/j.1399-0004.2007.00860.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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260
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Bowers CW, Singer-Sam J. Unique retrotransposon LINE-1 distribution at the Prader-Willi Angelman syndrome locus. J Mol Evol 2007; 65:475-84. [PMID: 17932619 DOI: 10.1007/s00239-007-9043-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 06/13/2007] [Accepted: 09/18/2007] [Indexed: 11/27/2022]
Abstract
We analyzed the distribution of long interspersed nuclear elements (LINE)-1 (L1) along mouse autosomes at a 1-Mb scale, and found a unique combination of high density and strand asymmetry of L1 elements at the imprinted Prader-Willi syndrome/Angelman syndrome (PWS/AS) locus on mouse chromosome 7. This L1 signature overlaps the paternally expressed domain of the locus, excluding the maternally expressed Ube3a gene, and is conserved in rat and human. Unlike the PWS/AS locus, other instances of high L1 density and strand asymmetry in the mouse are not associated with imprinted regions and are not evolutionarily conserved in human. The evolutionary conservation of the L1 signature at the PWS/AS locus despite differences in composition of L1 elements between rodent and human, requires a mechanism for active perpetuation of L1 asymmetry during bursts of L1 activity, and indicates a possible functional role for L1 elements at this locus. Aside from the PWS/AS locus, rodents have a far greater correlation of L1 densities between DNA strands than do humans; we provide evidence that this difference in interstrand correlation between the two taxa is due largely to the difference in average age of the dominant L1 families.
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Affiliation(s)
- Chauncey W Bowers
- Division of Neurosciences, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91010, USA
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261
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Kawahara M, Wu Q, Ferguson-Smith AC, Kono T. Appropriate expression of imprinted genes on mouse chromosome 12 extends development of bi-maternal embryos to term. FEBS Lett 2007; 581:5178-84. [PMID: 17959172 DOI: 10.1016/j.febslet.2007.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 09/25/2007] [Accepted: 10/01/2007] [Indexed: 11/17/2022]
Abstract
Recently, we reported that the restored regulation of imprinted gene expression from two regions -H19 differentially methylated region (H19-DMR) and intergenic germline-derived DMR (IG-DMR) - is sufficient for accomplishing full-term development in mice. In the present study, we determined the developmental ability of the bi-maternal embryos (BMEs) containing the non-growing oocyte genome with the IG-DMR deletion (ng(Deltach12)) and fully-grown (fg) oocyte genome. Foetuses derived from ng(Deltach12)/fg BMEs were alive at E19.5 but could not survive further. Comparison with BMEs derived from Igf2+/- ng/fg genomes suggests that bi-allelic H19 expression might be involved in foetal development.
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Affiliation(s)
- Manabu Kawahara
- Department of BioScience, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan
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262
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Saadeh R, Lisi EC, Batista DAS, McIntosh I, Hoover-Fong JE. Albinism and developmental delay: the need to test for 15q11-q13 deletion. Pediatr Neurol 2007; 37:299-302. [PMID: 17903679 PMCID: PMC2128718 DOI: 10.1016/j.pediatrneurol.2007.06.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 05/16/2007] [Accepted: 06/20/2007] [Indexed: 11/20/2022]
Abstract
We report on a 17-month-old African girl with cutaneous and ophthalmologic features of oculocutaneous albinism type 2 as well as microcephaly, absent speech, and tremulous movements. Mutations of the P gene within the Angelman/Prader-Willi syndrome critical region at 15q11-q13 cause oculocutaneous albinism type 2. Comorbid oculocutaneous albinism and Angelman syndrome were suspected and confirmed by cytogenetics. Phenotypic features of Angelman syndrome or Prader-Willi syndrome in a patient with albinism should prompt further investigation.
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Affiliation(s)
- Reem Saadeh
- Institute of Genetic Medicine, Johns Hopkins University, Baltimore, Maryland 21287, USA.
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263
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Abstract
Major depressive disorder (MDD) is a common and highly heterogeneous psychiatric disorder encompassing a spectrum of symptoms involving deficits to a range of cognitive, psychomotor and emotional processes. As is the norm for aetiological studies into the majority of psychiatric phenotypes, particular focus has fallen on the interplay between genetic and environmental factors. There are, however, several epidemiological, clinical and molecular peculiarities associated with MDD that are hard to explain using traditional gene- and environment-based approaches. Our goal in this study is to demonstrate the benefits of looking beyond conventional 'DNA+environment' and 'DNA x environment' aetiological paradigms. Epigenetic factors - inherited and acquired modifications of DNA and histones that regulate various genomic functions occurring without a change in nuclear DNA sequence - offer new insights about many of the non-Mendelian features of major depression, and provide a direct mechanistic route via which the environment can interact with the genome. The study of epigenetics, especially in complex diseases, is a relatively new field of research, and optimal laboratory techniques and analysis methods are still being developed. Incorporating epigenetic research into aetiological studies of MDD thus presents a number of methodological and interpretive challenges that need to be addressed. Despite these difficulties, the study of DNA methylation and histone modifications has the potential to transform our understanding about the molecular aetiology of complex diseases.
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Affiliation(s)
- J Mill
- The Krembil Family Epigenetics Laboratory, Centre for Addiction and Mental Health, Toronto, ON, Canada.
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264
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Hore TA, Rapkins RW, Graves JAM. Construction and evolution of imprinted loci in mammals. Trends Genet 2007; 23:440-8. [PMID: 17683825 DOI: 10.1016/j.tig.2007.07.003] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Accepted: 07/05/2007] [Indexed: 11/28/2022]
Abstract
Genomic imprinting first evolved in mammals around the time that humans last shared a common ancestor with marsupials and monotremes (180-210 million years ago). Recent comparisons of large imprinted domains in these divergent mammalian groups have shown that imprinting evolved haphazardly at various times in different lineages, perhaps driven by different selective forces. Surprisingly, some imprinted domains were formed relatively recently, using non-imprinted components acquired from unexpected genomic regions. Rearrangement and the insertion of retrogenes, small nucleolar RNAs, microRNAs, differential CpG methylation and control by non-coding RNA often accompanied the acquisition of imprinting. Here, we use comparisons between different mammalian groups to chart the course of evolution of two related epigenetic regulatory systems in mammals: genomic imprinting and X-chromosome inactivation.
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Affiliation(s)
- Timothy A Hore
- Research School of Biological Sciences, The Australian National University, Canberra, ACT 2601, Australia
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265
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Lebedev IN, Puzyrev VP. Epigenetic perspectives of safety in assisted reproductive technologies. RUSS J GENET+ 2007. [DOI: 10.1134/s1022795407090013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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266
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Tuiskula-Haavisto M, Vilkki J. Parent-of-origin specific QTL--a possibility towards understanding reciprocal effects in chicken and the origin of imprinting. Cytogenet Genome Res 2007; 117:305-12. [PMID: 17675872 DOI: 10.1159/000103192] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Accepted: 10/06/2006] [Indexed: 01/16/2023] Open
Abstract
Reciprocal effects for sexual maturity, egg production, egg quality traits and viability are well known in poultry crosses. They have been used in an optimal way to form profitable production hybrids. These effects have been hypothesized to originate from sex-linked genes, maternal effects or a combination of both. However, these may not be the only explanations for reciprocal effects. Recent mapping of quantitative trait loci (QTL) has revealed autosomal areas with parent-of-origin specific effects in the chicken. In mammals, parental imprinting, i.e. the specifically regulated expression of either maternal or paternal allele in the offspring, is the main cause of such effects. The most commonly accepted hypothesis for the origin of imprinting, the conflict hypothesis, assumes a genetic conflict of interest between the maternal and paternal genomes regarding the allocation of resources to the offspring. It also intrinsically implies that imprinting should not occur in oviparous taxa. However, new molecular genetic information has raised a need to review the possible involvement of imprinting or some related phenomena as a putative cause of reciprocal effects in poultry. Comparative mapping provides strong evidence for the conservation of orthologous imprinted gene clusters on chicken macrochromosomes. Furthermore, these gene clusters exhibit asynchronous DNA replication, an epigenetic mark specific for all imprinted regions. It has been proposed that these intrinsic chromosomal properties have been important for the evolution of imprinted gene expression in the mammalian lineage. Many of the mapped parent-of-origin specific QTL effects in chicken locate in or close to these conserved regions that show some of the basic features involved in monoallelic expression. If monoallelic expression in these regions would be observed in birds, the actual mechanism and cause may be different from the imprinting that evolved later in the mammalian lineage. In this review we discuss recent molecular genetic results that may provide tools for understanding of reciprocal differences in poultry breeding and the evolution of imprinting.
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Affiliation(s)
- M Tuiskula-Haavisto
- Biotechnology and Food Research, MTT Agrifood Research Finland, Jokioinen, Finland.
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267
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Hergüner S, Motavalli Mukaddes N. Psychosis associated with fluoxetine in Prader-Willi syndrome. J Am Acad Child Adolesc Psychiatry 2007; 46:944-945. [PMID: 17667473 DOI: 10.1097/chi.0b013e318068fbed] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Sabri Hergüner
- Department of Child and Adolescent Psychiatry, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Nahit Motavalli Mukaddes
- Department of Child and Adolescent Psychiatry, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
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268
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Dudley O, Muscatelli F. Clinical evidence of intrauterine disturbance in Prader-Willi syndrome, a genetically imprinted neurodevelopmental disorder. Early Hum Dev 2007; 83:471-8. [PMID: 17055193 DOI: 10.1016/j.earlhumdev.2006.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 08/02/2006] [Accepted: 09/05/2006] [Indexed: 11/18/2022]
Abstract
BACKGROUND Imprinted genes are considered to play an important role in growth and early development but much of the research is based on animal studies. AIM This study reports clinical data from a French population concerning prenatal, perinatal and postnatal complications in Prader-Willi syndrome (PWS), a genetically imprinted neurodevelopmental disorder associated with growth retardation, intellectual impairment and obesity. STUDY DESIGN Data from family health records concerning prenatal, perinatal and postnatal complications were collected from 52 French people with the deletion form (DEL), and 34 French people with the maternal disomy form of PWS (UPD) and compared against national norms and between groups. RESULTS Significant findings include: a history of miscarriage, high rate of polyhydramnios (12/34 UPD, 11/52 DEL), a high rate of induced labour, a high rate of Caesarian section (20/34 UPD, 26/52 DEL), small gestational age (10/34 UPD, 22/52 DEL), hypotonia (34/34 UPD, 49/52 DEL), and suckling deficit (25/34 UPD, 46/52 DEL). Significant differences between genetic subtypes include a higher rate of induced labour in UPD (27/34 UPD, 25/52 DEL), an increased risk of premature term in UPD (9/34 UPD vs. 4/52 DEL), raised maternal age in UPD (36.4 years vs. 29.3 years), low birth weight for newborns with a deletion form of PWS (girls 2.8 kg, boys 2.7 kg), a positive correlation between parental weight and offspring birth weight only for patients with UPD (UPD maternal: r=0.62, paternal: r=0.51). CONCLUSION The results indicate significant intrauterine disturbance in PWS, particularly in PWS due to UPD, but a more significant weight disturbance for PWS due to deletion.
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Affiliation(s)
- Oenone Dudley
- NMDA, UMR CNRS 6156, Intitut de Biologie Moléculaire de Luminy (IBDML), Campus de Luminy, Case 907, 13288 Marseille, France.
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269
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Miller JL, James GA, Goldstone AP, Couch JA, He G, Driscoll DJ, Liu Y. Enhanced activation of reward mediating prefrontal regions in response to food stimuli in Prader-Willi syndrome. J Neurol Neurosurg Psychiatry 2007; 78:615-9. [PMID: 17158560 PMCID: PMC2077944 DOI: 10.1136/jnnp.2006.099044] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Individuals with Prader-Willi syndrome (PWS) exhibit severe disturbances in appetite regulation, including delayed meal termination, early return of hunger after a meal, seeking and hoarding food and eating of non-food substances. Brain pathways involved in the control of appetite in humans are thought to include the hypothalamus, frontal cortex (including the orbitofrontal, ventromedial prefrontal, dorsolateral prefrontal and anterior cingulate areas), insula, and limbic and paralimbic areas. We hypothesised that the abnormal appetite in PWS results from aberrant reward processing of food stimuli in these neural pathways. METHODS We compared functional MRI blood oxygen level dependent (BOLD) responses while viewing pictures of food in eight adults with PWS and eight normal weight adults after ingestion of an oral glucose load. RESULTS Subjects with PWS demonstrated significantly greater BOLD activation in the ventromedial prefrontal cortex than controls when viewing food pictures. No significant differences were found in serum insulin, glucose or triglyceride levels between the groups at the time of the scan. CONCLUSIONS Individuals with PWS had an increased BOLD response in the ventromedial prefrontal cortex compared with normal weight controls when viewing pictures of food after an oral glucose load. These findings suggest that an increased reward value for food may underlie the excessive hunger in PWS, and support the significance of the frontal cortex in modulating the response to food in humans. Our findings in the extreme appetite phenotype of PWS support the importance of the neural pathways that guide reward related behaviour in modulating the response to food in humans.
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Affiliation(s)
- Jennifer L Miller
- Department of Pediatrics, University of Florida, College of Medicine, Gainesville, Florida, USA
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270
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Peery EG, Elmore MD, Resnick JL, Brannan CI, Johnstone KA. A targeted deletion upstream of Snrpn does not result in an imprinting defect. Mamm Genome 2007; 18:255-62. [PMID: 17514346 DOI: 10.1007/s00335-007-9019-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 03/01/2007] [Indexed: 11/25/2022]
Abstract
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) result from the disturbance of imprinted gene expression within human chromosome 15q11-q13. Some cases of PWS and AS are caused by microdeletions near the SNRPN gene that disrupt a regulatory element termed the imprinting center (IC). The IC has two functional components; an element at the promoter of SNRPN involved in PWS (PWS-IC) and an element 35 kilobases (kb) upstream of SNRPN involved in AS (AS-IC). To further understand the function of the IC, we sought to create a mouse model for AS-IC mutations. We have generated two deletions at a location analogous to that of the human AS-IC. Neither deletion produced an imprinting defect as indicated by DNA methylation and gene expression analyses. These results indicate that no elements critical for AS-IC function in mouse reside within the 12.8-kb deleted region and suggest that the specific location of the AS-IC is not conserved between human and mouse.
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Affiliation(s)
- Edwin G Peery
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida 32610-0266, USA
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271
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Butler MG, Bittel DC. Plasma obestatin and ghrelin levels in subjects with Prader-Willi syndrome. Am J Med Genet A 2007; 143A:415-21. [PMID: 17304548 PMCID: PMC5463458 DOI: 10.1002/ajmg.a.31687] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Prader-Willi syndrome (PWS) is an obesity syndrome characterized by rapid weight gain and excessive food intake. Food intake is regulated by the hypothalamus but directly influenced by gastrointestinal peptides responding to the nutritional status and body composition of an individual. Ghrelin, derived from preproghrelin, is secreted by the stomach and increases appetite while obestatin, a recently identified peptide derived post-translationally from preproghrelin, works in opposition to ghrelin by decreasing appetite. The objective of this study was to measure fasting obestatin and ghrelin levels in peripheral blood of subjects with PWS and compare to age and gender matched control subjects. Plasma obestatin and ghrelin levels were measured in subjects with PWS (n = 16, mean age = 16.0 +/- 13.3 years; age range 1-44 years) and age and gender matched control subjects (n = 16). Significantly higher obestatin levels were seen in the 16 PWS subjects (398 +/- 102 pg/ml) compared with 16 controls (325 +/- 109 pg/ml; matched t-test, P = 0.04), particularly in 5 young (< or =3 years old) PWS subjects (460 +/- 49 pg/ml) compared with 5 young controls (369 +/- 96 pg/ml; matched t-test, P = 0.03). No significant difference in ghrelin levels was seen between the PWS and comparison groups. No significant correlation was observed for either peptide when compared with body mass index but a significant negative correlation was seen for ghrelin and age in PWS subjects. Our observations suggest that obestatin may be higher in infants with PWS compared to comparison infants. The possibility that obestatin may contribute to the failure to thrive which is common in infants with PWS warrants further investigation.
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Affiliation(s)
- Merlin G Butler
- Section of Medical Genetics and Molecular Medicine, Children's Mercy Hospitals and Clinics and University of Missouri-Kansas City School of Medicine, Kansas City, Missouri 64108, USA.
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272
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Miller JL, Couch JA, Schmalfuss I, He G, Liu Y, Driscoll DJ. Intracranial abnormalities detected by three-dimensional magnetic resonance imaging in Prader-Willi syndrome. Am J Med Genet A 2007; 143A:476-83. [PMID: 17103438 DOI: 10.1002/ajmg.a.31508] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The neuropathologic abnormalities associated with Prader-Willi syndrome (PWS) are largely unknown. PWS is due to the loss of several paternally expressed genes in chromosome 15q11-q13 region. Several of the imprinted genes in the 15q11-q13 region are normally expressed in the brain and thought to be necessary for neuronal growth and development. Thus, we hypothesized that we would find abnormalities in gray and white matter growth in individuals with PWS. We evaluated three-dimensional (3-D) MRI scans of 20 individuals with PWS, aged three months to 39 years, and compared them to 3-D MRI scans of 21 normal weight sibling controls and 16 individuals with early-onset morbid obesity (EMO) of unknown etiology. The interpreters of the scans were blinded to the diagnosis of the subjects. Intracranial abnormalities in individuals with PWS included ventriculomegaly (100% of individuals), decreased volume of brain tissue in the parietal-occipital lobe (50%), sylvian fissure polymicrogyria (60%), and incomplete insular closure (65%). None of the EMO or normal weight control subjects had any of these findings. We found multiple morphologic brain abnormalities in subjects with PWS suggesting that the loss of paternally expressed genes in chromosome 15q11-q13 region may result in abnormalities of neuronal development. The specific mechanisms underlying these neuropathological abnormalities and their correlation with the clinical phenotype remain to be elucidated.
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Affiliation(s)
- Jennifer L Miller
- Department of Pediatrics, University of Florida, Gainesville, Florida 32610-0296, USA
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273
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Butler MG, Theodoro MF, Bittel DC, Kuipers PJ, Driscoll DJ, Talebizadeh Z. X-chromosome inactivation patterns in females with Prader-Willi syndrome. Am J Med Genet A 2007; 143A:469-75. [PMID: 17036338 PMCID: PMC5459689 DOI: 10.1002/ajmg.a.31506] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder caused by loss of paternally expressed genes from the 15q11-q13 region generally due to a paternally-derived deletion of the 15q11-q13 region or maternal disomy 15 (UPD). Maternal disomy 15 is usually caused by maternal meiosis I non-disjunction associated with advanced maternal age and after fertilization with a normal sperm leading to trisomy 15, a lethal condition unless trisomy rescue occurs with loss of the paternal chromosome 15. To further characterize the pathogenesis of maternal disomy 15 process in PWS, the status of X-chromosome inactivation was calculated to determine whether non-random skewing of X-inactivation is present indicating a small pool of early embryonic cells. We studied X-chromosome inactivation in 25 females with PWS-UPD, 35 with PWS-deletion, and 50 controls (with similar means, medians, and age ranges) using the polymorphic androgen receptor (AR) gene assay. A significant positive correlation (r = 0.5, P = 0.01) was seen between X-chromosome inactivation and age for only the UPD group. Furthermore, a significantly increased level (P = 0.02) of extreme X-inactivation skewness (>90%) was detected in our PWS-UPD group (24%) compared to controls (4%). This observation could indicate that trisomy 15 occurred at conceptus with trisomy rescue in early pregnancy leading to extreme skewness in several PWS-UPD subjects. Extreme X-inactivation skewness may also lead to additional risks for X-linked recessive disorders in PWS females with UPD and extreme X-chromosome skewness.
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Affiliation(s)
- Merlin G Butler
- Section of Medical Genetics and Molecular Medicine, Children's Mercy Hospitals and Clinics and University of Missouri, Kansas City School of Medicine, Kansas City, Missouri 64108, USA.
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274
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Edwards CA, Ferguson-Smith AC. Mechanisms regulating imprinted genes in clusters. Curr Opin Cell Biol 2007; 19:281-9. [PMID: 17467259 DOI: 10.1016/j.ceb.2007.04.013] [Citation(s) in RCA: 272] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 04/16/2007] [Indexed: 12/20/2022]
Abstract
Clustered imprinted genes are regulated by differentially methylated imprinting control regions (ICRs) that affect gene activity and repression in cis over a large region. Although a primary imprint signal for each of these clusters is DNA methylation, different mechanisms are used to establish and maintain these marks. The majority of ICRs are methylated in the maternal germline and are usually promoters for antisense transcripts whose elongation is associated with imprinting control in the domain. In contrast, ICRs methylated in the paternal germline do not appear to act as promoters and are located between genes. At least one, at the Igf2/H19 locus, is known to function as an insulator. Analysis of ICRs suggests that maternal and paternal methylation imprints function in distinct ways.
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Affiliation(s)
- Carol A Edwards
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
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275
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Hogart A, Nagarajan RP, Patzel KA, Yasui DH, LaSalle JM. 15q11-13 GABAA receptor genes are normally biallelically expressed in brain yet are subject to epigenetic dysregulation in autism-spectrum disorders. Hum Mol Genet 2007; 16:691-703. [PMID: 17339270 PMCID: PMC1934608 DOI: 10.1093/hmg/ddm014] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Human chromosome 15q11-13 is a complex locus containing imprinted genes as well as a cluster of three GABA(A) receptor subunit (GABR) genes-GABRB3, GABRA5 and GABRG3. Deletion or duplication of 15q11-13 GABR genes occurs in multiple human neurodevelopmental disorders including Prader-Willi syndrome (PWS), Angelman syndrome (AS) and autism. GABRB3 protein expression is also reduced in Rett syndrome (RTT), caused by mutations in MECP2 on Xq28. Although Gabrb3 is biallelically expressed in mouse brain, conflicting data exist regarding the imprinting status of the 15q11-13 GABR genes in humans. Using coding single nucleotide polymorphisms we show that all three GABR genes are biallelically expressed in 21 control brain samples, demonstrating that these genes are not imprinted in normal human cortex. Interestingly, four of eight autism and one of five RTT brain samples showed monoallelic or highly skewed allelic expression of one or more GABR gene, suggesting that epigenetic dysregulation of these genes is common to both disorders. Quantitative real-time RT-PCR analysis of PWS and AS samples with paternal and maternal 15q11-13 deletions revealed a paternal expression bias of GABRB3, while RTT brain samples showed a significant reduction in GABRB3 and UBE3A. Chromatin immunoprecipitation and bisulfite sequencing in SH-SY5Y neuroblastoma cells demonstrated that MeCP2 binds to methylated CpG sites within GABRB3. Our previous studies demonstrated that homologous 15q11-13 pairing in neurons was dependent on MeCP2 and was disrupted in RTT and autism cortex. Combined, these results suggest that MeCP2 acts as a chromatin organizer for optimal expression of both alleles of GABRB3 in neurons.
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Affiliation(s)
| | | | | | | | - Janine M. LaSalle
- * Address correspondence to: Janine M. LaSalle, Medical Microbiology and Immunology, One Shields Ave, Davis, CA 95616, (530) 754-7598 (phone), (530) 752-8692 (fax),
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276
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Bittel DC, Kibiryeva N, Sell SM, Strong TV, Butler MG. Whole genome microarray analysis of gene expression in Prader-Willi syndrome. Am J Med Genet A 2007; 143A:430-42. [PMID: 17236194 PMCID: PMC5467864 DOI: 10.1002/ajmg.a.31606] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Prader-Willi syndrome (PWS) is caused by loss of function of paternally expressed genes in the 15q11-q13 region and a paucity of data exists on transcriptome variation. To further characterize genetic alterations in this classic obesity syndrome using whole genome microarrays to analyze gene expression, microarray and quantitative RT-PCR analysis were performed using RNA isolated from lymphoblastoid cells from PWS male subjects (four with 15q11-q13 deletion and three with UPD) and three age and cognition matched nonsyndromic comparison males. Of more than 47,000 probes examined in the microarray, 23,383 were detectable and 323 had significantly different expression in the PWS lymphoblastoid cells relative to comparison cells, 14 of which were related to neurodevelopment and function. As expected, there was no evidence of expression of paternally expressed genes from the 15q11-q13 region (e.g., SNRPN) in the PWS cells. Alterations in expression of serotonin receptor genes (e.g., HTR2B) and genes involved in eating behavior and obesity (ADIPOR2, MC2R, HCRT, OXTR) were noted. Other genes of interest with reduced expression in PWS subjects included STAR (a key regulator of steroid synthesis) and SAG (an arrestin family member which desensitizes G-protein-coupled receptors). Quantitative RT-PCR for SAG, OXTR, STAR, HCRT, and HTR2B using RNA isolated from their lymphoblastoid cells and available brain tissue (frontal cortex) from separate individuals with PWS and control subjects and normalized to GAPD gene expression levels validated our microarray gene expression data. Our analysis identified previously unappreciated changes in gene expression which may contribute to the clinical manifestations seen in PWS.
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Affiliation(s)
- Douglas C. Bittel
- Children’s Mercy Hospitals and Clinics, University of Missouri-Kansas City, School of Medicine, Kansas City, MO
| | - Nataliya Kibiryeva
- Children’s Mercy Hospitals and Clinics, University of Missouri-Kansas City, School of Medicine, Kansas City, MO
| | | | | | - Merlin G. Butler
- Children’s Mercy Hospitals and Clinics, University of Missouri-Kansas City, School of Medicine, Kansas City, MO
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277
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Bittel DC, Kibiryeva N, McNulty SG, Driscoll DJ, Butler MG, White RA. Whole genome microarray analysis of gene expression in an imprinting center deletion mouse model of Prader-Willi syndrome. Am J Med Genet A 2007; 143A:422-9. [PMID: 17036336 PMCID: PMC5453790 DOI: 10.1002/ajmg.a.31504] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Prader-Willi syndrome (PWS) is caused by loss of paternally expressed genes in the 15q11-q13 region. To further characterize alterations in gene expression in this classical obesity syndrome we used whole genome microarrays to study a PWS mouse model resulting from a paternally derived imprinting center (IC) deletion (PWS IC deletion). These mice die generally within 2-3 days of life (reflective of failure to thrive in infants with PWS) and therefore, the analysis was performed on RNA extracted from the whole brain of PWS IC deletion mice and normal littermates at less than 24 hr after birth. Of more than 45,000 probes examined, 26,471 (59%) were detected for further analysis, and 69 had a significant change in expression of at least 1.5-fold and a false discovery rate (FDR) of 5%. Eight of the genes with differential expression were imprinted and from the PWS critical region (PWSCR). The three genes with the highest expression in the PWS IC mice were pro-opiomelanocortin (Pomc) and two transcripts of unknown function. Pomc knockout mice have been shown to develop obesity. Therefore, elevated Pomc RNA in PWS IC deletion neonatal mice may be an important genetic factor in the survival of these mice as it may affect eating behavior. Interestingly, Mc5r, a melanocortin receptor known to directly respond to Pomc expression changes, was upregulated as well. Mc5r is known to be involved with thermoregulation which is reportedly abnormal in PWS infants. These observations support a role for Pomc and the network of genes involved in regulating energy homeostasis in the early clinical findings of failure to thrive observed in PWS. Other notable patterns include three previously unstudied transcripts that are expressed only from the paternal allele under regulatory control of the IC and include AK013560, BB3144814, and BB182944 (whose genes are located in the mouse PWSCR on chromosome 7B). As expected, all the known paternally expressed genes from the PWSCR had detection signals below the threshold in the PWS IC deletion mice but were clearly detectable in control littermates. Several of the genes in this study were further examined by quantitative reverse transcription-PCR (RT-PCR) to confirm their expression status. Further analysis of gene expression in these mice may lead to novel pathways affected in PWS. These results, along with other recent reports, suggest that the cumulative effect of modest changes in expression of many genes, especially genes involved in energy metabolism, contribute to the failure to thrive of infants with PWS.
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Affiliation(s)
- Douglas C. Bittel
- Children’s Mercy Hospitals and Clinics and University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri
| | - Nataliya Kibiryeva
- Children’s Mercy Hospitals and Clinics and University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri
| | - Steven G. McNulty
- Children’s Mercy Hospitals and Clinics and University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri
| | - Daniel J. Driscoll
- Department of Pediatrics, University of Florida College of Medicine, Gainesville, Florida
| | - Merlin G. Butler
- Children’s Mercy Hospitals and Clinics and University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri
| | - Robert A. White
- Children’s Mercy Hospitals and Clinics and University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri
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278
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Maina EN, Webb T, Soni S, Whittington J, Boer H, Clarke D, Holland A. Analysis of candidate imprinted genes in PWS subjects with atypical genetics: a possible inactivating mutation in the SNURF/SNRPN minimal promoter. J Hum Genet 2007; 52:297-307. [PMID: 17262171 DOI: 10.1007/s10038-007-0109-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 12/28/2006] [Indexed: 10/23/2022]
Abstract
Prader-Willi syndrome (PWS) is a neurodevelopmental disorder associated with abnormalities of chromosome 15q11q13. The majority of cases result either from a deletion approximately 4 Mb in size, affecting chromosome 15 of paternal origin or from UPD(15)mat; these account for approximately 70 and approximately 20-25% of PWS cases, respectively. In the remaining 3-5% of PWS cases where neither the deletion nor UPD is detectable, PWS is thought to be caused either by a defect in the imprinting centre resulting in a failure to reset the paternally inherited chromosome 15 derived from the paternal grandmother or, very occasionally, from a balanced translocation involving a breakpoint in 15q11q13. Nine probands with a firm clinical diagnosis of PWS but who had neither a typical deletion in the PWS region nor UPD(15)mat were investigated for inactivating mutations in 11 genes located in the PWS region, including SNURF and SNRPN, which are associated with the imprinting centre. Other genes studied for mutations included MKRN3, NDN, IPW, HBII-85, HBII-13, HBII-436, HBII-438a, PAR1 and PAR5. A possibly inactivating mutation in the SNRPN minimal promoter region was identified. No other inactivating mutations were found in the remainder of our panel of PWS subjects with atypical genetics. Expression levels of several of the candidate genes for PWS were also investigated in this series of probands. The results indicate that PWS may result from a stochastic partial inactivation of important genes.
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Affiliation(s)
- Esther N Maina
- University Department of Medical and Molecular Genetics, Birmingham Women's Hospital Edgbaston, Birmingham, B15 2TG, UK
| | - Tessa Webb
- University Department of Medical and Molecular Genetics, Birmingham Women's Hospital Edgbaston, Birmingham, B15 2TG, UK
| | - Sarita Soni
- Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Douglas House, Trumpington Road, Cambridge, CB2 2AH, UK
| | - Joyce Whittington
- Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Douglas House, Trumpington Road, Cambridge, CB2 2AH, UK
| | - Harm Boer
- Janet Shaw Clinic, North Warwickshire NHS Trust, Warwickshire, UK
| | - David Clarke
- Lea Castle Hospital, North Warwickshire NHS Trust, Warwickshire, UK
| | - Anthony Holland
- Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Douglas House, Trumpington Road, Cambridge, CB2 2AH, UK.
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279
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Rogelj B. Brain-specific small nucleolar RNAs. J Mol Neurosci 2007; 28:103-9. [PMID: 16679551 DOI: 10.1385/jmn:28:2:103] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Revised: 11/30/1999] [Accepted: 08/08/2005] [Indexed: 11/11/2022]
Abstract
Small nucleolar RNAs (snoRNAs) are a group of noncoding RNAs that function mainly as guides for modification of ribosomal RNAs (rRNAs) and small nuclear RNAs (snRNAs). A subgroup of snoRNAs was found to be predominantly expressed in the brain; and interestingly, these brain-specific snoRNAs (b-snoRNAs) appear not to be involved in modification of rRNAs and snRNAs, raising the question of what their function and targets might be. Expression studies of b-snoRNAs in mice have shown potential involvement of two b-snoRNAs, MBII-48 and MBII-52, in learning and memory. HBII-52, the human homolog of MBII-52, appears to be involved with regulation of 5-HT(2C) receptor subunit mRNA. Furthermore, several reports link the disruption of expression of a specific b-snoRNA, HBII-85, with a neurobehavioral disorder, Prader-Willi syndrome. This paper reviews the current knowledge of the properties, expression, and functions of b-snoRNAs.
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Affiliation(s)
- Boris Rogelj
- Department of Neuroscience, Institute of Psychiatry, King's College London, London, UK.
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280
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Soni S, Whittington J, Holland AJ, Webb T, Maina E, Boer H, Clarke D. The course and outcome of psychiatric illness in people with Prader-Willi syndrome: implications for management and treatment. JOURNAL OF INTELLECTUAL DISABILITY RESEARCH : JIDR 2007; 51:32-42. [PMID: 17181601 DOI: 10.1111/j.1365-2788.2006.00895.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
BACKGROUND This study is part of a larger UK-wide study investigating psychiatric illness in people with Prader-Willi syndrome (PWS), and describes the longitudinal aspect of psychiatric illness, in particular psychotic illness, and examines the use and role of psychotropic medication. METHOD A total of 119 individuals with genetically confirmed PWS were included in the study. An informant-based questionnaire was administered for each participant to screen for a history of psychopathology. Those who screened positive were visited at their homes to obtain further information. This assessment included a full psychiatric history and mental state examination using the Psychiatric Assessment Schedule for Adults with Developmental Disability and the Operational Criteria Checklist for psychotic and affective illness to collect information regarding phenomenology and course of illness, and a modified life events questionnaire. At the end of the study period, informant-based telephone interviews were again carried out, up to 2.5 years after the initial screening. Information regarding medication usage was collected. RESULTS The results confirm previous findings that psychiatric illness in people with PWS resembles an affective disorder. Individuals with the maternal uniparental disomy genetic subtype had a more severe course of illness than those with the deletion genetic subtype in terms of a greater risk of recurrence, more episodes, higher incidence and a possibly poorer response to medication with more side-effects. Individuals with a recurrent episode during the follow-up period had a poorer course of illness. Selective serotonin reuptake inhibitor medication is frequently used, and beneficial effects may reflect fundamental pathological processes in PWS. Mood-stabilizing medication was found to be of little benefit and reasons for this are examined. CONCLUSION The longitudinal course of psychiatric illness and response to medication in people with PWS is fully described. Further research is needed regarding the effect of psychotropic medications, particularly mood-stabilizing medication. These data will enable informed decisions to be made regarding management options and provide information on the possible long-term outcome of illness.
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Affiliation(s)
- S Soni
- Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Cambridge, UK.
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281
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Torrado M, Araoz V, Baialardo E, Abraldes K, Mazza C, Krochik G, Ozuna B, Leske V, Caino S, Fano V, Chertkoff L. Clinical-etiologic correlation in children with Prader-Willi syndrome (PWS): An interdisciplinary study. Am J Med Genet A 2007; 143A:460-8. [PMID: 17163531 DOI: 10.1002/ajmg.a.31520] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes within chromosome 15q11-q13. Most cases are due to paternal deletion of this region; the remaining cases result from maternal uniparental disomy (UPD) and imprinting defects. To better understand the phenotypic variability of PWS, a genotype-phenotype correlation study was performed in 91 children with PWS. Patients were diagnosed by Southern Blot Methylation assay and genetic subtypes were established using FISH and microsatellite analyses. Fifty-nine subjects with deletion (31/28 males/females; mean age 3.86 years), 30 with UPD (14/16 males/females; mean age 3.89 years) and 2 girls with a presumed imprinting defect (mean age 0.43 yrs) were identified. For correlation purposes patients were grouped as "deleted" and "non-deleted." An increased maternal age was found in the UPD group. Four of Holm's criteria were more frequently present in the deleted group: need for special feeding techniques, sleep disturbance, hypopigmentation, and speech articulation defects. Concerning cognitive assessments, only 9.52% of subjects with deletion had Full-Scale IQ (FSIQ) > or =70, while 61.53% of subjects without deletion had FSIQ > or =70. Similar results were found in behavioral measures. Sleep disorders and carbohydrate metabolism were systematically assessed. Polysomnoghaphic studies revealed a higher frequency of central events with desaturations > or =10% in the deleted group (P = 0.020). In summary, the phenotype was significantly different between both groups in certain parameters related to the CNS. These results might be related to the differences in brain gene expression of the genetic subtypes.
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Affiliation(s)
- Maria Torrado
- Hospital de Pediatría Prof. Dr. Juan P. Garrahan - Genética, Buenos Aires, Argentina.
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282
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Promkan M, Teingtat S, Stheinkijkarnchai A, Wasant P, Patmasiriwat P. Highest accuracy of combined consensus clinical criteria and SNRPN gene molecular markers in diagnosis of Prader-Willi syndrome in Thai patients. Clin Chem Lab Med 2007; 45:972-80. [PMID: 17867985 DOI: 10.1515/cclm.2007.271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Prader-Willi Syndrome (PWS) is a complex human genetic disease arising from a loss of paternal allele expression of imprinting genes on chromosome 15q11-q13. Normally the CpG islands at this site are heavily methylated in the maternal allele, but unmethylated in the paternal allele and therefore activated in gene expression. only the methylated allele should present in pws patients when methylation-specific pcr (msp) is analyzed. METHODS This paper reports an analysis of PWS in Thai patients using consensus diagnostic criteria based on a combination of clinical data, basic G-banding and fluorescence in situ hybridization (FISH) cytogenetics, PCR-based methylation assay, and bisulfite sequencing of the CpG islands of SNRPN to confirm 15q deletion or the methylation pattern of the SNRPN promoter and exon 1. Lack of complete clinical reports or inadequacy of the minimum laboratory support required had made it difficult to diagnose PWS, Angelman syndrome and other microdeletion disorders. RESULTS Accuracy of 100% was obtained for diagnosis of the PWS study patients using the minimum requirements necessary. A total of 20 patients were diagnosed as PWS based on clinical criteria and the scoring tool for PWS, and the same approach was applied to four separate patients with some unmatched criteria but phenotypic similarity to PWS. Findings showed that 70% of those clinically diagnosed as PWS patients (14/20) had a deletion at 15q11-q13 according to FISH, while all 20 patients showed MSP positive of SNRPN gene. Six cases (30%) without a paternal deletion were confirmed to have maternal uniparental disomy (mUPD) of PWS by MSP and methylation sequencing approaches. Noteworthy, two of the six cases with mUPD were 3.5 year-old twins. None of the five cases with scores lower than the reported consensus criteria showed positive G-band, FISH or MSP results. CONCLUSIONS We demonstrate here the high power of combining clinical findings, FISH and MSP in definitive diagnosis of PWS and in distinguishing between the two major different types of molecular mechanisms. No false positives or false negatives were observed in our analysis.
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Affiliation(s)
- Moltira Promkan
- Department of Clinical Microscopy, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand
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283
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Rapkins RW, Hore T, Smithwick M, Ager E, Pask AJ, Renfree MB, Kohn M, Hameister H, Nicholls RD, Deakin JE, Graves JAM. Recent assembly of an imprinted domain from non-imprinted components. PLoS Genet 2006; 2:e182. [PMID: 17069464 PMCID: PMC1626109 DOI: 10.1371/journal.pgen.0020182] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 09/11/2006] [Indexed: 02/02/2023] Open
Abstract
Genomic imprinting, representing parent-specific expression of alleles at a locus, raises many questions about how—and especially why—epigenetic silencing of mammalian genes evolved. We present the first in-depth study of how a human imprinted domain evolved, analyzing a domain containing several imprinted genes that are involved in human disease. Using comparisons of orthologous genes in humans, marsupials, and the platypus, we discovered that the Prader-Willi/Angelman syndrome region on human Chromosome 15q was assembled only recently (105–180 million years ago). This imprinted domain arose after a region bearing UBE3A (Angelman syndrome) fused with an unlinked region bearing SNRPN (Prader-Willi syndrome), which had duplicated from the non-imprinted SNRPB/B′. This region independently acquired several retroposed gene copies and arrays of small nucleolar RNAs from different parts of the genome. In their original configurations, SNRPN and UBE3A are expressed from both alleles, implying that acquisition of imprinting occurred after their rearrangement and required the evolution of a control locus. Thus, the evolution of imprinting in viviparous mammals is ongoing. Humans and other mammals have two copies of the genome. For most genes, both copies are active. However, some genes are active only when they are inherited from the father, others only when inherited from the mother. These “imprinted” genes are clustered in domains that are controlled coordinately. Only mammals show genomic imprinting. It is not understood how or why genes became imprinted during mammalian evolution. The authors used comparisons between humans and the most distantly related mammals, marsupials and monotremes, to discover how one of these imprinted domains evolved. The authors studied an imprinted domain on human Chromosome 15, mutations which cause Prader-Willi and Angelman syndromes (PWS-AS). They discovered that the PWS and AS genes lie on different chromosomes in kangaroos and platypus and are not imprinted. Other imprinted genes in the domain, including the putative control region, are absent from the genome and derived from copies of genes from yet other chromosomes. The arrangement in kangaroos and platypus is present also in the chicken genome, so it must be ancestral. This study concludes that the PWS-AS imprinted region was assembled relatively recently from non-imprinted components that were moved together or copied from all over the genome.
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Affiliation(s)
- Robert W Rapkins
- Australian Research Council Center for Kangaroo Genomics and Research School of Biological Sciences, Australian National University, Canberra, Australia
| | - Tim Hore
- Australian Research Council Center for Kangaroo Genomics and Research School of Biological Sciences, Australian National University, Canberra, Australia
| | - Megan Smithwick
- Department of Genetics, La Trobe University, Melbourne, Australia
| | - Eleanor Ager
- Department of Zoology, University of Melbourne, Melbourne, Australia
| | - Andrew J Pask
- Department of Zoology, University of Melbourne, Melbourne, Australia
| | - Marilyn B Renfree
- Department of Zoology, University of Melbourne, Melbourne, Australia
| | - Matthias Kohn
- Department of Medical Genetics, University of Ulm, Ulm, Germany
| | - Horst Hameister
- Department of Medical Genetics, University of Ulm, Ulm, Germany
| | - Robert D Nicholls
- Department of Pediatrics, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Janine E Deakin
- Australian Research Council Center for Kangaroo Genomics and Research School of Biological Sciences, Australian National University, Canberra, Australia
| | - Jennifer A. Marshall Graves
- Australian Research Council Center for Kangaroo Genomics and Research School of Biological Sciences, Australian National University, Canberra, Australia
- * To whom correspondence should be addressed. E-mail:
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284
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Mitalipov S, Clepper L, Sritanaudomchai H, Fujimoto A, Wolf D. Methylation status of imprinting centers for H19/IGF2 and SNURF/SNRPN in primate embryonic stem cells. Stem Cells 2006; 25:581-8. [PMID: 17170068 DOI: 10.1634/stemcells.2006-0120] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Embryonic stem cells (ESCs) hold promise for cell and tissue replacement approaches to treating human diseases based on their capacity to differentiate into a wide variety of somatic cells and tissues. However, long-term in vitro culture and manipulations of ESCs may adversely affect their epigenetic integrity, including imprinting. We have recently reported aberrant biallelic expression of IGF2 and H19 in several rhesus monkey ESC lines, whereas SNRPN and NDN were normally imprinted and expressed predominantly from the paternal allele. The dysregulation of IGF2 and H19 that is associated with tumorigenesis in humans may result from improper maintenance of allele-specific methylation patterns at an imprinting center (IC) upstream of H19. To test this possibility, we performed methylation analysis of several monkey ESC lines by genomic bisulfite sequencing. We investigated methylation profiles of CpG islands within the IGF2/H19 IC harboring the CTCF-6 binding site. In addition, the methylation status of the IC within the promoter/exon 1 of SNURF/SNRPN known as the Prader-Willi syndrome IC was examined. Our results demonstrate abnormal hypermethylation within the IGF2/H19 IC in all analyzed ESC lines, whereas the SNURF/SNRPN IC was differentially methylated, consistent with monoallelic expression.
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Affiliation(s)
- Shoukhrat Mitalipov
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Ave., Beaverton, OR 97006, USA.
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285
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Goytain A, Hines RM, El-Husseini A, Quamme GA. NIPA1(SPG6), the basis for autosomal dominant form of hereditary spastic paraplegia, encodes a functional Mg2+ transporter. J Biol Chem 2006; 282:8060-8. [PMID: 17166836 DOI: 10.1074/jbc.m610314200] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mutations in the NIPA1(SPG6) gene, named for "nonimprinted in Prader-Willi/Angelman" has been implicated in one form of autosomal dominant hereditary spastic paraplegia (HSP), a neurodegenerative disorder characterized by progressive lower limb spasticity and weakness. However, the function of NIPA1 is unknown. Here, we show that reduced magnesium concentration enhances expression of NIPA1 suggesting a role in cellular magnesium metabolism. Indeed NIPA1 mediates Mg2+ uptake that is electrogenic, voltage-dependent, and saturable with a Michaelis constant of 0.69+/-0.21 mM when expressed in Xenopus oocytes. Subcellular localization with immunofluorescence showed that endogenous NIPA1 protein associates with early endosomes and the cell surface in a variety of neuronal and epithelial cells. As expected of a magnesium-responsive gene, we find that altered magnesium concentration leads to a redistribution between the endosomal compartment and the plasma membrane; high magnesium results in diminished cell surface NIPA1 whereas low magnesium leads to accumulation in early endosomes and recruitment to the plasma membrane. The mouse NIPA1 mutants, T39R and G100R, corresponding to the respective human mutants showed a loss-of-function when expressed in oocytes and altered trafficking in transfected COS7 cells. We conclude that NIPA1 normally encodes a Mg2+ transporter and the loss-of function of NIPA1(SPG6) due to abnormal trafficking of the mutated protein provides the basis of the HSP phenotype.
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Affiliation(s)
- Angela Goytain
- Department of Medicine and Department of Psychiatry, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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286
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Hung CC, Chen CP, Lin SP, Chien SC, Lee CN, Cheng WF, Hsieh WS, Liu MS, Su YN, Lin WL. Quantitative Assay of Deletion or Duplication Genotype by Capillary Electrophoresis System: Application in Prader–Willi Syndrome and Duchenne Muscular Dystrophy. Clin Chem 2006; 52:2203-10. [PMID: 17040959 DOI: 10.1373/clinchem.2006.071118] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Abstract
Background: Deletions and duplications involving large DNA segments result in underexpression or overexpression, depending on the changes in allele dose, and are known to cause many common disorders. Detection of allele dose variations in the human genome is increasingly important in medical genetic diagnosis.
Methods: We used multiplex quantitative PCR coupled with capillary electrophoresis for accurate allele dose determination. In cases of Prader–Willi syndrome (PWS), a total of 24 patients with PWS, as well as 205 control individuals from the general population, were analyzed by use of multiplex quantitative PCR to amplify the FGFR2 gene, the KRIT1 gene, and the SNRPN gene simultaneously. In cases of Duchenne muscular dystrophy (DMD), we optimized the multiplex quantitative PCR to amplify 38 exons to analyze the DMD gene for rapid diagnosis of 12 DMD-affected males, 12 obligate carriers from families, and 50 unaffected female controls.
Results: We were able to unambiguously diagnose the deletion genotype in PWS patients and identify all deletion or duplication genotypes and carrier status in DMD-affected cases with 100% sensitivity and specificity.
Conclusions: This report describes a novel single assay that can rapidly quantify allele dose to provide accurate clinical genetic diagnosis. This technique offers a valuable alternative for the rapid detection of genomic deletions or duplications and decreases costs because it does not require expensive fluorescent reagents.
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Affiliation(s)
- Chia-Cheng Hung
- Institute of Biomedical Engineering, College of Medicine and College of Engineering, Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
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287
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Abstract
The autism spectrum disorders (ASD) comprise a complex group of behaviorally related disorders that are primarily genetic in origin. Involvement of epigenetic regulatory mechanisms in the pathogenesis of ASD has been suggested by the occurrence of ASD in patients with disorders arising from epigenetic mutations (fragile X syndrome) or that involve key epigenetic regulatory factors (Rett syndrome). Moreover, the most common recurrent cytogenetic abnormalities in ASD involve maternally derived duplications of the imprinted domain on chromosome 15q11-13. Thus, parent of origin effects on sharing and linkage to imprinted regions on chromosomes 15q and 7q suggest that these regions warrant specific examination from an epigenetic perspective, particularly because epigenetic modifications do not change the primary genomic sequence, allowing risk epialleles to evade detection using standard screening strategies. This review examines the potential role of epigenetic factors in the etiology of ASD.
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Affiliation(s)
- N Carolyn Schanen
- Center for Pediatric Research, Nemours Biomedical Research, Wilmington, DE 19803, USA.
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288
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Santos-Rebouças CB, Pimentel MMG. Implication of abnormal epigenetic patterns for human diseases. Eur J Hum Genet 2006; 15:10-7. [PMID: 17047674 DOI: 10.1038/sj.ejhg.5201727] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Significant evidences have brought new insights on the mechanisms by which epigenetic machinery proteins regulate gene expression, leading to a redefinition of chromatin regulation in terms of modification of core histones, DNA methylation, RNA-mediated silencing pathways, action of methylation-dependent sensitive insulators and Polycomb/Trithorax group proteins. Consistent with these fundamental aspects, an increasing number of human pathologies have been found to be associated with aberrant epigenetics regulation, including cancer, mental retardation, neurodegenerative symptoms, imprinting disorders, syndromes involving chromosomal instabilities and a great number of human life-threatening diseases. The possibility of reversing epigenetic marks, in contrast to genetic code, may provide new pharmacological targets for emerging therapeutic intervention.
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Affiliation(s)
- C B Santos-Rebouças
- Department of Cell Biology and Genetics, State University of Rio de Janeiro, Rio de Janeiro, Brazil.
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289
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Bittel DC, Kibiryeva N, Butler MG. Expression of 4 genes between chromosome 15 breakpoints 1 and 2 and behavioral outcomes in Prader-Willi syndrome. Pediatrics 2006; 118:e1276-83. [PMID: 16982806 PMCID: PMC5453799 DOI: 10.1542/peds.2006-0424] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Prader-Willi syndrome is a neurodevelopmental disorder that is characterized by infantile hypotonia, feeding difficulties, hypogonadism, mental deficiency, hyperphagia (leading to obesity in early childhood), learning problems, and behavioral difficulties. A paternal 15q11-q13 deletion is found in approximately 70% of patients with Prader-Willi syndrome, approximately 25% have uniparental maternal disomy 15, and the remaining 2% to 5% have imprinting defects. The proximal deletion breakpoint in the 15q11-q13 region occurs at 1 of 2 sites located within either of 2 large duplicons allowing for the identification of 2 deletion subgroups. The larger, type I (TI) deletion involves breakpoint 1, which is close to the centromere, whereas the smaller, type II (TII) deletion involves breakpoint 2, located approximately 500 kilobases distal to breakpoint 1. Breakpoint 3 is located at the distal end of the 15q11-q13 region and common to both typical deletion subgroups. Analyses of the genetic subtypes of Prader-Willi syndrome to date have primarily compared individuals with typical deletion and uniparental maternal disomy 15 without grouping the individuals with a deletion into TI or TII. Distinct differences have been reported between individuals with Prader-Willi syndrome resulting from deletion compared with uniparental maternal disomy 15 in physical, cognitive, and behavioral parameters. We previously presented the first assessment of clinical differences in individuals with Prader-Willi syndrome categorized as having type I or II deletions. Adaptive behavior, obsessive-compulsive behaviors, reading, math, and visual-motor integration assessments were generally poorer in individuals with Prader-Willi syndrome and the TI deletion compared with subjects with Prader-Willi syndrome with the TII deletion or uniparental maternal disomy 15. Four genes (NIPA1, NIPA2, CYFIP1, and GCP5) have been identified in the chromosomal region between breakpoints 1 and 2 and are implicated in compulsive behavior and lower intellectual ability observed in individuals with Prader-Willi syndrome with TI versus TII deletions. We quantified messenger-RNA levels of these 4 genes in actively growing lymphoblastoid cells derived from 8 subjects with Prader-Willi syndrome with the TI deletion (4 males, 4 females; mean: age 25.2 +/- 8.9 years) and 9 with the TII deletion (3 males, 6 females; mean age: 19.5 +/- 5.8 years). Messenger-RNA levels were correlated with validated psychological and behavioral scales administered by trained psychologists blinded to genotype status. Messenger RNA from NIPA1, NIPA2, CYFIP1, and GCP5 was reduced but detectable in the subjects with Prader-Willi syndrome with the TI deletion, supporting biallelic expression. For the most part, messenger-RNA values were positively correlated with assessment parameters, indicating a direct relationship between messenger-RNA levels and better assessment scores, with the highest correlation for NIPA2. The coefficient of determination indicated the quantity of messenger RNA of the 4 genes explained from 24% to 99% of the variation of the behavioral and academic parameters measured. By comparison, the coefficient of determination for deletion type alone explained 5% to 50% of the variation in the assessed parameters. Understanding the influence of gene expression on behavioral and cognitive characteristics in humans is in the early stage of research development. Additional research is needed to identify the function of these genes and their interaction with gene networks to clarify the potential role they play in central nervous system development and function.
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Affiliation(s)
- Douglas C Bittel
- Children's Mercy Hospitals and Clinics and University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108, USA
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290
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Froyen G, Bauters M, Voet T, Marynen P. X-linked mental retardation and epigenetics. J Cell Mol Med 2006; 10:808-25. [PMID: 17125586 PMCID: PMC3933076 DOI: 10.1111/j.1582-4934.2006.tb00526.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Accepted: 10/23/2006] [Indexed: 01/08/2023] Open
Abstract
The search for the genetic defects in constitutional diseases has so far been restricted to direct methods for the identification of genetic mutations in the patients' genome. Traditional methods such as karyotyping, FISH, mutation screening, positional cloning and CGH, have been complemented with newer methods including array-CGH and PCR-based approaches (MLPA, qPCR). These methods have revealed a high number of genetic or genomic aberrations that result in an altered expression or reduced functional activity of key proteins. For a significant percentage of patients with congenital disease however, the underlying cause has not been resolved strongly suggesting that yet other mechanisms could play important roles in their etiology. Alterations of the 'native' epigenetic imprint might constitute such a novel mechanism. Epigenetics, heritable changes that do not rely on the nucleotide sequence, has already been shown to play a determining role in embryonic development, X-inactivation, and cell differentiation in mammals. Recent progress in the development of techniques to study these processes on full genome scale has stimulated researchers to investigate the role of epigenetic modifications in cancer as well as in constitutional diseases. We will focus on mental impairment because of the growing evidence for the contribution of epigenetics in memory formation and cognition. Disturbance of the epigenetic profile due to direct alterations at genomic regions, or failure of the epigenetic machinery due to genetic mutations in one of its components, has been demonstrated in cognitive derangements in a number of neurological disorders now. It is therefore tempting to speculate that the cognitive deficit in a significant percentage of patients with unexplained mental retardation results from epigenetic modifications.
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Affiliation(s)
- Guy Froyen
- Human Genome Laboratory, VIB, Department Molecular and Developmental Genetics, University of Leuven, Leuven, Belgium.
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291
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Reinhart B, Paoloni-Giacobino A, Chaillet JR. Specific differentially methylated domain sequences direct the maintenance of methylation at imprinted genes. Mol Cell Biol 2006; 26:8347-56. [PMID: 16954379 PMCID: PMC1636798 DOI: 10.1128/mcb.00981-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Landmark features of imprinted genes are differentially methylated domains (DMDs), in which one parental allele is methylated on CpG dinucleotides and the opposite allele is unmethylated. Genetic experiments in the mouse have shown that DMDs are required for the parent-specific expression of linked clusters of imprinted genes. To understand the mechanism whereby the differential methylation is established and maintained, we analyzed a series of transgenes containing DMD sequences and showed that imperfect tandem repeats from DMDs associated with the Snurf/Snrpn, Kcnq1, and Igf2r gene clusters govern transgene imprinting. For the Igf2r DMD the minimal imprinting signal is two unit copies of the tandem repeat. This imprinted transgene behaves identically to endogenous imprinted genes in Dnmt1o and Dnmt3L mutant mouse backgrounds. The primary function of the imprinting signal within the transgene DMD is to maintain, during embryogenesis and a critical period of genomic reprogramming, parent-specific DNA methylation states established in the germ line. This work advances our understanding of the imprinting mechanism by defining a genomic signal that dependably perpetuates an epigenetic state during postzygotic development.
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Affiliation(s)
- Bonnie Reinhart
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh, W1257 Biomedical Science Tower, Pittsburgh, PA 15213, USA
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292
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Schumacher A, Petronis A. Epigenetics of Complex Diseases: From General Theory to Laboratory Experiments. Curr Top Microbiol Immunol 2006; 310:81-115. [PMID: 16909908 DOI: 10.1007/3-540-31181-5_6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Despite significant effort, understanding the causes and mechanisms of complex non-Mendelian diseases remains a key challenge. Although numerous molecular genetic linkage and association studies have been conducted in order to explain the heritable predisposition to complex diseases, the resulting data are quite often inconsistent and even controversial. In a similar way, identification of environmental factors causal to a disease is difficult. In this article, a new interpretation of the paradigm of "genes plus environment" is presented in which the emphasis is shifted to epigenetic misregulation as a major etiopathogenic factor. Epigenetic mechanisms are consistent with various non-Mendelian irregularities of complex diseases, such as the existence of clinically indistinguishable sporadic and familial cases, sexual dimorphism, relatively late age of onset and peaks of susceptibility to some diseases, discordance of monozygotic twins and major fluctuations on the course of disease severity. It is also suggested that a substantial portion of phenotypic variance that traditionally has been attributed to environmental effects may result from stochastic epigenetic events in the cell. It is argued that epigenetic strategies, when applied in parallel with the traditional genetic ones, may significantly advance the discovery of etiopathogenic mechanisms of complex diseases. The second part of this chapter is dedicated to a review of laboratory methods for DNA methylation analysis, which may be useful in the study of complex diseases. In this context, epigenetic microarray technologies are emphasized, as it is evident that such technologies will significantly advance epigenetic analyses in complex diseases.
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Affiliation(s)
- A Schumacher
- The Krembil Family Epigenetics Laboratory, Centre for Addiction and Mental Health, ON, Toronto, Canada
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293
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Fassihi H, Lu L, Wessagowit V, Ozoemena LC, Jones CA, Dopping-Hepenstal PJC, Foster L, Atherton DJ, Mellerio JE, McGrath JA. Complete Maternal Isodisomy of Chromosome 3 in a Child with Recessive Dystrophic Epidermolysis Bullosa but No Other Phenotypic Abnormalities. J Invest Dermatol 2006; 126:2039-43. [PMID: 16710310 DOI: 10.1038/sj.jid.5700348] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mechanobullous disease Hallopeau-Siemens recessive dystrophic epidermolysis bullosa (HS-RDEB) results from mutations in the type VII collagen gene (COL7A1) on chromosome 3p21.31. Typically, there are frameshift, splice site, or nonsense mutations on both alleles. In this report, we describe a patient with HS-RDEB, who was homozygous for a new frameshift mutation, 345insG, in exon 3 of COL7A1. However, sequencing of parental DNA showed that although the patient's mother was a heterozygous carrier of this mutation, the father's DNA contained only wild-type sequence. Microsatellite marker analysis confirmed paternity and genotyping of 28 microsatellites spanning chromosome 3 revealed that the affected child was homozygous for every marker tested with all alleles originating from a single maternal chromosome 3. Thus, the HS-RDEB phenotype in this patient is due to complete maternal isodisomy of chromosome 3 and reduction to homozygosity of the mutant COL7A1 gene locus. To our knowledge, there are no published reports of uniparental disomy (UPD) in HS-RDEB; moreover, this case represents only the third example of UPD of chromosome 3 to be reported. The severity of the HS-RDEB in this case was similar to other affected individuals and no additional phenotypic abnormalities were observed, suggesting an absence of maternally imprinted genes on chromosome 3.
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Affiliation(s)
- Hiva Fassihi
- Genetic Skin Disease Group, St John's Institute of Dermatology, King's College School of Medicine at Guy's, King's College and St Thomas' Hospitals, London, UK
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294
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Badcock C, Crespi B. Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism. J Evol Biol 2006; 19:1007-32. [PMID: 16780503 DOI: 10.1111/j.1420-9101.2006.01091.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We describe a new hypothesis for the development of autism, that it is driven by imbalances in brain development involving enhanced effects of paternally expressed imprinted genes, deficits of effects from maternally expressed genes, or both. This hypothesis is supported by: (1) the strong genomic-imprinting component to the genetic and developmental mechanisms of autism, Angelman syndrome, Rett syndrome and Turner syndrome; (2) the core behavioural features of autism, such as self-focused behaviour, altered social interactions and language, and enhanced spatial and mechanistic cognition and abilities, and (3) the degree to which relevant brain functions and structures are altered in autism and related disorders. The imprinted brain theory of autism has important implications for understanding the genetic, epigenetic, neurological and cognitive bases of autism, as ultimately due to imbalances in the outcomes of intragenomic conflict between effects of maternally vs. paternally expressed genes.
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Affiliation(s)
- C Badcock
- Department of Sociology, London School of Economics, London, UK
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295
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Miller J, Kranzler J, Liu Y, Schmalfuss I, Theriaque DW, Shuster JJ, Hatfield A, Mueller OT, Goldstone AP, Sahoo T, Beaudet AL, Driscoll DJ. Neurocognitive findings in Prader-Willi syndrome and early-onset morbid obesity. J Pediatr 2006; 149:192-8. [PMID: 16887432 DOI: 10.1016/j.jpeds.2006.04.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 03/22/2006] [Accepted: 04/13/2006] [Indexed: 11/18/2022]
Abstract
OBJECTIVES To examine whether early-onset morbid obesity is associated with cognitive impairment, neuropathologic changes, and behavioral problems. STUDY DESIGN This case-control study compared head MRI scans and cognitive, achievement, and behavioral evaluations of subjects with Prader-Willi syndrome (PWS), early-onset morbid obesity (EMO), and normal-weight sibling control subjects from both groups. Head MRI was done on 17 PWS, 18 EMO, and 21 siblings, and cognitive, achievement, and behavioral evaluations were done on 19 PWS, 17 EMO, and 24 siblings. RESULTS The mean General Intellectual Ability score of the EMO group was 77.4 +/- 17.8; PWS, 63.3 +/- 14.2; and control subjects, 106.4 +/- 13.0. Achievement scores for the three groups were EMO, 78.7 +/- 18.8; PWS, 71.2 +/- 17.0; and control subjects, 104.8 +/- 17.0. Significant negative behaviors and poor adaptive skills were found in the EMO group. White matter lesions were noted on brain MRI in 6 subjects with PWS and 5 with EMO. None of the normal-weight control subjects had these findings. CONCLUSIONS Individuals with EMO have significantly lower cognitive function and more behavioral problems than control subjects with no history of childhood obesity. Both EMO and PWS subjects have white matter lesions on brain MRI that have not previously been described.
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Affiliation(s)
- Jennifer Miller
- Department of Pediatrics and the Center for Mammalian Genetics, University of Florida, College of Medicine, Gainesville, Florida 32610-0296, USA
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296
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Schulz R, Menheniott TR, Woodfine K, Wood AJ, Choi JD, Oakey RJ. Chromosome-wide identification of novel imprinted genes using microarrays and uniparental disomies. Nucleic Acids Res 2006; 34:e88. [PMID: 16855283 PMCID: PMC1524921 DOI: 10.1093/nar/gkl461] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 05/26/2006] [Accepted: 06/15/2006] [Indexed: 01/06/2023] Open
Abstract
Genomic imprinting refers to a specialized form of epigenetic gene regulation whereby the expression of a given allele is dictated by parental origin. Defining the extent and distribution of imprinting across genomes will be crucial for understanding the roles played by imprinting in normal mammalian growth and development. Using mice carrying uniparental disomies or duplications, microarray screening and stringent bioinformatics, we have developed the first large-scale tissue-specific screen for imprinted gene detection. We quantify the stringency of our methodology and relate it to previous non-tissue-specific large-scale studies. We report the identification in mouse of four brain-specific novel paternally expressed transcripts and an additional three genes that show maternal expression in the placenta. The regions of conserved linkage in the human genome are associated with the Prader-Willi Syndrome (PWS) and Beckwith-Wiedemann Syndrome (BWS) where imprinting is known to be a contributing factor. We conclude that large-scale systematic analyses of this genre are necessary for the full impact of genomic imprinting on mammalian gene expression and phenotype to be elucidated.
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Affiliation(s)
- Reiner Schulz
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
| | - Trevelyan R. Menheniott
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
| | - Kathryn Woodfine
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
| | - Andrew J. Wood
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
| | - Jonathan D. Choi
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
| | - Rebecca J. Oakey
- King's College London, School of Medicine at Guy's, King's College and St. Thomas' Hospitals, Department of Medical and Molecular Genetics8th Floor Guy's Tower, London SE1 9RT, UK
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297
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Chelly J, Khelfaoui M, Francis F, Chérif B, Bienvenu T. Genetics and pathophysiology of mental retardation. Eur J Hum Genet 2006; 14:701-13. [PMID: 16721406 DOI: 10.1038/sj.ejhg.5201595] [Citation(s) in RCA: 188] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022] Open
Abstract
Mental retardation (MR) is defined as an overall intelligence quotient lower than 70, associated with functional deficit in adaptive behavior, such as daily-living skills, social skills and communication. Affecting 1-3% of the population and resulting from extraordinary heterogeneous environmental, chromosomal and monogenic causes, MR represents one of the most difficult challenges faced today by clinician and geneticists. Detailed analysis of the Online Mendelian Inheritance in Man database and literature searches revealed more than a thousand entries for MR, and more than 290 genes involved in clinical phenotypes or syndromes, metabolic or neurological disorders characterized by MR. We estimate that many more MR genes remain to be identified. The purpose of this review is to provide an overview on the remarkable progress achieved over the last decade in delineating genetic causes of MR, and to highlight the emerging biological and cellular processes and pathways underlying pathogeneses of human cognitive disorders.
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Affiliation(s)
- Jamel Chelly
- Institut Cochin, Inserm-U567, CNRS-UMR 8104, Université Paris 5 René Descartes, Faculté de Médecine René Descartes, Paris, France.
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298
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Vincent Q, Alcaïs A, Alter A, Schurr E, Abel L. Quantifying Genomic Imprinting in the Presence of Linkage. Biometrics 2006; 62:1071-80. [PMID: 17156281 DOI: 10.1111/j.1541-0420.2006.00610.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Genomic imprinting decreases the power of classical linkage analysis, in which paternal and maternal transmissions of marker alleles are equally weighted. Several methods have been proposed for taking genomic imprinting into account in the model-free linkage analysis of binary traits. However, none of these methods are suitable for the formal identification and quantification of genomic imprinting in the presence of linkage. In addition, the available methods are designed for use with pure sib-pairs, requiring artificial decomposition in cases of larger sibships, leading to a loss of power. We propose here the maximum likelihood binomial method adaptive for imprinting (MLB-I), which is a unified analytic framework giving rise to specific tests in sibships of any size for (i) linkage adaptive to imprinting, (ii) genomic imprinting in the presence of linkage, and (iii) partial versus complete genomic imprinting. In addition, we propose an original measure for quantifying genomic imprinting. We have derived and validated the distribution of the three tests under their respective null hypotheses for various genetic models, and have assessed the power of these tests in simulations. This method can readily be applied to genome-wide scanning, as illustrated here for leprosy sibships. Our approach provides a novel tool for dissecting genomic imprinting in model-free linkage analysis, and will be of considerable value for identifying and evaluating the contribution of imprinted genes to complex diseases.
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Affiliation(s)
- Quentin Vincent
- Laboratory of Human Genetics of Infectious Diseases, University of Paris René Descartes-INSERM U.550, Necker Medical School, Paris, 75015, France
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299
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Wu MY, Chen KS, Bressler J, Hou A, Tsai TF, Beaudet AL. Mouse imprinting defect mutations that model Angelman syndrome. Genesis 2006; 44:12-22. [PMID: 16397868 DOI: 10.1002/gene.20179] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are neurobehavioral disorders resulting from deficiency of imprinted gene expression from paternal or maternal chromosome 15q11-15q13, respectively. In humans, expression of the imprinted genes is under control of a bipartite cis-acting imprinting center (IC). Families with deletions causing PWS imprinting defects localize the PWS-IC to 4.3 kb overlapping with SNRPN exon 1. Families with deletions causing AS imprinting defects localize the AS-IC to 880 bp 35 kb upstream of the PWS-IC. We report two mouse mutations resulting in defects similar to that seen in AS patients with deletion of the AS-IC. An insertion/duplication mutation 13 kb upstream of Snrpn exon 1 resulted in lack of methylation at the maternal Snrpn promoter, activation of maternally repressed genes, and decreased expression of paternally repressed genes. The acquisition of a paternal epigenotype on the maternal chromosome in the mutant mice was demonstrated by the ability to rescue the lethality and growth retardation in a mouse model of a PWS imprinting defect. A second mutation, an 80-kb deletion extending upstream of the first mutation, caused a similar imprinting defect with variable penetrance. These results suggest that there is a mouse functional equivalent to the human AS-IC.
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Affiliation(s)
- Mei-Yi Wu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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300
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Royo H, Bortolin ML, Seitz H, Cavaillé J. Small non-coding RNAs and genomic imprinting. Cytogenet Genome Res 2006; 113:99-108. [PMID: 16575168 DOI: 10.1159/000090820] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Accepted: 07/19/2005] [Indexed: 12/29/2022] Open
Abstract
Experimental and computer-assisted approaches have led to the identification of hundreds of imprinted small RNA genes, mainly clustered in two chromosomal domains (human 15q11-->q13 and 14q32 loci). The genes are only detected in placental mammals and belong to the C/D RNA and microRNA gene families. These are small non-coding RNAs involved in RNA-guided post-transcriptional RNA modifications and RNA-mediated gene silencing, respectively. Here, we discuss their potential functions and report the identification of novel small RNA genes lying within (or nearby) known imprinted chromosomal domains.
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Affiliation(s)
- H Royo
- LBME-CNRS, UMR 5099, IFR 109, Toulouse, France
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