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Tritto V, Eoli M, Paterra R, Redaelli S, Moscatelli M, Rusconi F, Riva P. Characterization of 22q12 Microdeletions Causing Position Effect in Rare NF2 Patients with Complex Phenotypes. Int J Mol Sci 2022; 23:ijms231710017. [PMID: 36077416 PMCID: PMC9456353 DOI: 10.3390/ijms231710017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/11/2022] [Accepted: 08/25/2022] [Indexed: 11/18/2022] Open
Abstract
Neurofibromatosis type 2 is an autosomal dominant tumor-prone disorder mainly caused by NF2 point mutations or intragenic deletions. Few individuals with a complex phenotype and 22q12 microdeletions have been described. The 22q12 microdeletions’ pathogenic effects at the genetic and epigenetic levels are currently unknown. We here report on 22q12 microdeletions’ characterization in three NF2 patients with different phenotype complexities. A possible effect of the position was investigated by in silico analysis of 22q12 topologically associated domains (TADs) and regulatory elements, and by expression analysis of 12 genes flanking patients’ deletions. A 147 Kb microdeletion was identified in the patient with the mildest phenotype, while two large deletions of 561 Kb and 1.8 Mb were found in the other two patients, showing a more severe symptomatology. The last two patients displayed intellectual disability, possibly related to AP1B1 gene deletion. The microdeletions change from one to five TADs, and the 22q12 chromatin regulatory landscape, according to the altered expression levels of four deletion-flanking genes, including PIK3IP1, are likely associated with an early ischemic event occurring in the patient with the largest deletion. Our results suggest that the identification of the deletion extent can provide prognostic markers, predictive of NF2 phenotypes, and potential therapeutic targets, thus overall improving patient management.
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Affiliation(s)
- Viviana Tritto
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, 20054 Segrate, Italy
| | - Marica Eoli
- Unità di Neuro-Oncologia Molecolare, Fondazione IRCCS, Istituto Neurologico Carlo Besta, 20133 Milan, Italy
- Correspondence: (M.E.); (P.R.)
| | - Rosina Paterra
- Unità di Neuro-Oncologia Molecolare, Fondazione IRCCS, Istituto Neurologico Carlo Besta, 20133 Milan, Italy
| | - Serena Redaelli
- Dipartimento di Medicina e Chirurgia, University of Milano-Bicocca, 20900 Monza, Italy
| | - Marco Moscatelli
- Unità di Neuroradiologia, Fondazione IRCCS, Istituto Neurologico Carlo Besta, 20133 Milan, Italy
| | - Francesco Rusconi
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, 20054 Segrate, Italy
| | - Paola Riva
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, 20054 Segrate, Italy
- Correspondence: (M.E.); (P.R.)
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Kehrer-Sawatzki H, Cooper DN. Classification of NF1 microdeletions and its importance for establishing genotype/phenotype correlations in patients with NF1 microdeletions. Hum Genet 2021; 140:1635-1649. [PMID: 34535841 PMCID: PMC8553723 DOI: 10.1007/s00439-021-02363-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/01/2021] [Indexed: 01/12/2023]
Abstract
An estimated 5–11% of patients with neurofibromatosis type-1 (NF1) harbour large deletions encompassing the NF1 gene and flanking regions. These NF1 microdeletions are subclassified into type 1, 2, 3 and atypical deletions which are distinguishable from each other by their extent and by the number of genes included within the deletion regions as well as the frequency of mosaicism with normal cells. Most common are type-1 NF1 deletions which encompass 1.4-Mb and 14 protein-coding genes. Type-1 deletions are frequently associated with overgrowth, global developmental delay, cognitive disability and dysmorphic facial features which are uncommon in patients with intragenic pathogenic NF1 gene variants. Further, patients with type-1 NF1 deletions frequently exhibit high numbers of neurofibromas and have an increased risk of malignant peripheral nerve sheath tumours. Genes located within the type-1 NF1 microdeletion interval and co-deleted with NF1 are likely to act as modifiers responsible for the severe disease phenotype in patients with NF1 microdeletions, thereby causing the NF1 microdeletion syndrome. Genotype/phenotype correlations in patients with NF1 microdeletions of different lengths are important to identify such modifier genes. However, these correlations are critically dependent upon the accurate characterization of the deletions in terms of their extent. In this review, we outline the utility as well as the shortcomings of multiplex ligation-dependent probe amplification (MLPA) to classify the different types of NF1 microdeletion and indicate the importance of high-resolution microarray analysis for correct classification, a necessary precondition to identify those genes responsible for the NF1 microdeletion syndrome.
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Affiliation(s)
| | - David N Cooper
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
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3
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Demaerel W, Mostovoy Y, Yilmaz F, Vervoort L, Pastor S, Hestand MS, Swillen A, Vergaelen E, Geiger EA, Coughlin CR, Chow SK, McDonald-McGinn D, Morrow B, Kwok PY, Xiao M, Emanuel BS, Shaikh TH, Vermeesch JR. The 22q11 low copy repeats are characterized by unprecedented size and structural variability. Genome Res 2020; 29:1389-1401. [PMID: 31481461 PMCID: PMC6724673 DOI: 10.1101/gr.248682.119] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Accepted: 07/24/2019] [Indexed: 12/17/2022]
Abstract
Low copy repeats (LCRs) are recognized as a significant source of genomic instability, driving genome variability and evolution. The Chromosome 22 LCRs (LCR22s) mediate nonallelic homologous recombination (NAHR) leading to the 22q11 deletion syndrome (22q11DS). However, LCR22s are among the most complex regions in the genome, and their structure remains unresolved. The difficulty in generating accurate maps of LCR22s has also hindered localization of the deletion end points in 22q11DS patients. Using fiber FISH and Bionano optical mapping, we assembled LCR22 alleles in 187 cell lines. Our analysis uncovered an unprecedented level of variation in LCR22s, including LCR22A alleles ranging in size from 250 to 2000 kb. Further, the incidence of various LCR22 alleles varied within different populations. Additionally, the analysis of LCR22s in 22q11DS patients and their parents enabled further refinement of the rearrangement site within LCR22A and -D, which flank the 22q11 deletion. The NAHR site was localized to a 160-kb paralog shared between the LCR22A and -D in seven 22q11DS patients. Thus, we present the most comprehensive map of LCR22 variation to date. This will greatly facilitate the investigation of the role of LCR variation as a driver of 22q11 rearrangements and the phenotypic variability among 22q11DS patients.
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Affiliation(s)
| | - Yulia Mostovoy
- Cardiovascular Research Institute, UCSF School of Medicine, San Francisco, California 94158, USA
| | - Feyza Yilmaz
- Department of Integrative Biology, University of Colorado Denver, Denver, Colorado 80204, USA.,Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado Denver, Aurora, Colorado 80045, USA
| | | | - Steven Pastor
- Division of Human Genetics, Children's Hospital of Philadelphia and Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Matthew S Hestand
- Departement of Human Genetics, KU Leuven, Leuven, 3000 Belgium.,Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.,Department of Pediatrics, University of Cincinnati, Cincinnati, Ohio 45221, USA
| | - Ann Swillen
- Departement of Human Genetics, KU Leuven, Leuven, 3000 Belgium
| | - Elfi Vergaelen
- Departement of Human Genetics, KU Leuven, Leuven, 3000 Belgium
| | - Elizabeth A Geiger
- Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado Denver, Aurora, Colorado 80045, USA
| | - Curtis R Coughlin
- Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado Denver, Aurora, Colorado 80045, USA
| | - Stephen K Chow
- Cardiovascular Research Institute, UCSF School of Medicine, San Francisco, California 94158, USA
| | - Donna McDonald-McGinn
- Division of Human Genetics, Children's Hospital of Philadelphia and Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Bernice Morrow
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Pui-Yan Kwok
- Cardiovascular Research Institute, UCSF School of Medicine, San Francisco, California 94158, USA
| | - Ming Xiao
- School of Biomedical Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA
| | - Beverly S Emanuel
- Division of Human Genetics, Children's Hospital of Philadelphia and Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Tamim H Shaikh
- Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado Denver, Aurora, Colorado 80045, USA
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Grossi A, Cusano R, Rusmini M, Penco F, Schena F, Podda RA, Caorsi R, Gattorno M, Uva P, Ceccherini I. ADA2 deficiency due to a novel structural variation in 22q11.1. Clin Genet 2019; 95:732-733. [PMID: 30920658 DOI: 10.1111/cge.13518] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Revised: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 01/10/2023]
Affiliation(s)
- Alice Grossi
- UOC Genetica Medica, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | | | - Marta Rusmini
- UOC Genetica Medica, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Federica Penco
- UOSD Malattie Autoinfiammatorie/Immunodeficienze, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Francesca Schena
- UOSD Malattie Autoinfiammatorie/Immunodeficienze, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Rosa A Podda
- Ospedale Brotzu and Università di Cagliari, Cagliari, Italy
| | - Roberta Caorsi
- UOSD Malattie Autoinfiammatorie/Immunodeficienze, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Marco Gattorno
- UOSD Malattie Autoinfiammatorie/Immunodeficienze, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Paolo Uva
- CRS4, Science and Technology Park Polaris, Pula, Italy
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Maisenbacher MK, Merrion K, Pettersen B, Young M, Paik K, Iyengar S, Kareht S, Sigurjonsson S, Demko ZP, Martin KA. Incidence of the 22q11.2 deletion in a large cohort of miscarriage samples. Mol Cytogenet 2017; 10:6. [PMID: 28293297 PMCID: PMC5345148 DOI: 10.1186/s13039-017-0308-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/22/2017] [Indexed: 03/16/2023] Open
Abstract
Background The 22q11.2 deletion syndrome is the most common microdeletion syndrome in livebirths, but data regarding its incidence in other populations is limited and also include ascertainment bias. This study was designed to determine the incidence of the 22q11.2 deletion in miscarriage samples sent for clinical molecular cytogenetic testing. Results Twenty-six thousand one hundred one fresh product of conception (POC) samples were sent to a CLIA- certified, CAP-accredited laboratory from April 2010–-May 2016 for molecular cytogenetic miscarriage testing using a single-nucleotide polymorphism (SNP)-based microarray platform. A retrospective review determined the incidence of the 22q11.2 deletion in this sample set. Fetal results were obtained in 22,451 (86%) cases, of which, 15 (0.07%) had a microdeletion in the 22q11.2 region (incidence, 1/1497). Of those, 12 (80%) cases were found in samples that were normal at the resolution of traditional karyotyping (i.e., had no chromosome abnormalities above 10 Mb in size) and three (20%) cases had additional findings (Trisomy 15, Trisomy 16, XXY). Ten (67%) cases with a 22q11.2 deletion had the common ~3 Mb deletion; the remaining 5 cases had deletions ranging in size from 0.65 to 1.5 Mb. A majority (12/15) of cases had a deletion on the maternally inherited chromosome. No significant relationship between maternal age and presence of a fetal 22q11.2 deletion was observed. Conclusions The observed incidence of 1/1497 for the 22q11.2 deletion in miscarriage samples is higher than the reported general population prevalence (1/4000–1/6000). Further research is needed to determine whether the 22q11.2 deletion is a causal factor for miscarriage.
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Affiliation(s)
| | | | | | - Michael Young
- Natera, Inc., 201 Industrial Road, San Carlos, 94070 CA USA
| | - Kiyoung Paik
- Natera, Inc., 201 Industrial Road, San Carlos, 94070 CA USA
| | - Sushma Iyengar
- Natera, Inc., 201 Industrial Road, San Carlos, 94070 CA USA
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6
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An exploratory study of predisposing genetic factors for DiGeorge/velocardiofacial syndrome. Sci Rep 2017; 7:40031. [PMID: 28059126 PMCID: PMC5216377 DOI: 10.1038/srep40031] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 12/01/2016] [Indexed: 12/13/2022] Open
Abstract
DiGeorge/velocardiofacial syndrome (DGS/VCFS) is a disorder caused by a 22q11.2 deletion mediated by non-allelic homologous recombination (NAHR) between low-copy repeats (LCRs). We have evaluated the role of LCR22 genomic architecture and PRDM9 variants as DGS/VCFS predisposing factors. We applied FISH using fosmid probes on chromatin fibers to analyze the number of tandem repeat blocks in LCR22 in two DGS/VCFS fathers-of-origin with proven 22q11.2 NAHR susceptibility. Results revealed copy number variations (CNVs) of L9 and K3 fosmids in these individuals compared to controls. The total number of L9 and K3 copies was also characterized using droplet digital PCR (ddPCR). Although we were unable to confirm variations, we detected an additional L9 amplicon corresponding to a pseudogene. Moreover, none of the eight DGS/VCFS parents-of-origin was heterozygote for the inv(22)(q11.2) haplotype. PRDM9 sequencing showed equivalent allelic distributions between DGS/VCFS parents-of-origin and controls, although a new PRDM9 allele (L50) was identified in one case. Our results support the hypothesis that LCR22s variations influences 22q11.2 NAHR events, however further studies are needed to confirm this association and clarify the contribution of pseudogenes and rare PDRM9 alleles to NAHR susceptibility.
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7
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Vangkilde A, Olsen L, Hoeffding LK, Pedersen CB, Mortensen PB, Werge T, Trabjerg B. Schizophrenia Spectrum Disorders in a Danish 22q11.2 Deletion Syndrome Cohort Compared to the Total Danish Population--A Nationwide Register Study. Schizophr Bull 2016; 42:824-31. [PMID: 26738530 PMCID: PMC4838106 DOI: 10.1093/schbul/sbv195] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Cross-sectional studies have shown associations between 22q11.2 deletion syndrome and schizophrenia. However, large-scale prospective studies have been lacking. We, therefore, conducted the first large-scale population based study on the risk of being diagnosed with schizophrenia in persons identified with 22q11.2 deletion syndrome. METHODS Danish nationwide registers were linked to establish a cohort consisting of all Danish citizens born during 1955-2004 and the cohort was followed from January 1, 1994 until December 31, 2013. Data were analyzed using survival analyses and adjusted for calendar year, age, sex, and parental mental health history. RESULTS A total of 156 individuals with 22q11.2 deletion syndrome were identified, out of which 6 individuals were diagnosed with schizophrenia spectrum disorders following identification with 22q11 deletion syndrome. Identified carriers of 22q11.2 deletion had an 8.13(95% CI: 3.65-18.09) fold increased risk of schizophrenia spectrum disorder. CONCLUSIONS Carriers of a 22q11.2 deletion who had been clinically identified had a highly increased risk of schizophrenia spectrum disorders.
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Affiliation(s)
- Anders Vangkilde
- Mental Health Services Copenhagen, Institute of Biological Psychiatry, Mental Health Centre Sct. Hans, Copenhagen, Denmark; Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark
| | - Line Olsen
- Mental Health Services Copenhagen, Institute of Biological Psychiatry, Mental Health Centre Sct. Hans, Copenhagen, Denmark; Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark;
| | - Louise K Hoeffding
- Mental Health Services Copenhagen, Institute of Biological Psychiatry, Mental Health Centre Sct. Hans, Copenhagen, Denmark; Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark
| | - Carsten B Pedersen
- Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark; National Centre for Register-based Research, Business and Social Sciences, Aarhus University, Aarhus, Denmark; Centre for Integrated Register-based Research, CIRRAU, Aarhus University, Aarhus, Denmark
| | - Preben B Mortensen
- Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark; National Centre for Register-based Research, Business and Social Sciences, Aarhus University, Aarhus, Denmark
| | - Thomas Werge
- Mental Health Services Copenhagen, Institute of Biological Psychiatry, Mental Health Centre Sct. Hans, Copenhagen, Denmark; Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Betina Trabjerg
- Initiative for Integrative Psychiatric Research, iPSYCH, The Lundbeck Foundation, Copenhagen, Denmark; National Centre for Register-based Research, Business and Social Sciences, Aarhus University, Aarhus, Denmark
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Meechan DW, Maynard TM, Tucker ES, Fernandez A, Karpinski BA, Rothblat LA, LaMantia AS. Modeling a model: Mouse genetics, 22q11.2 Deletion Syndrome, and disorders of cortical circuit development. Prog Neurobiol 2015; 130:1-28. [PMID: 25866365 DOI: 10.1016/j.pneurobio.2015.03.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 03/24/2015] [Accepted: 03/29/2015] [Indexed: 12/21/2022]
Abstract
Understanding the developmental etiology of autistic spectrum disorders, attention deficit/hyperactivity disorder and schizophrenia remains a major challenge for establishing new diagnostic and therapeutic approaches to these common, difficult-to-treat diseases that compromise neural circuits in the cerebral cortex. One aspect of this challenge is the breadth and overlap of ASD, ADHD, and SCZ deficits; another is the complexity of mutations associated with each, and a third is the difficulty of analyzing disrupted development in at-risk or affected human fetuses. The identification of distinct genetic syndromes that include behavioral deficits similar to those in ASD, ADHC and SCZ provides a critical starting point for meeting this challenge. We summarize clinical and behavioral impairments in children and adults with one such genetic syndrome, the 22q11.2 Deletion Syndrome, routinely called 22q11DS, caused by micro-deletions of between 1.5 and 3.0 MB on human chromosome 22. Among many syndromic features, including cardiovascular and craniofacial anomalies, 22q11DS patients have a high incidence of brain structural, functional, and behavioral deficits that reflect cerebral cortical dysfunction and fall within the spectrum that defines ASD, ADHD, and SCZ. We show that developmental pathogenesis underlying this apparent genetic "model" syndrome in patients can be defined and analyzed mechanistically using genomically accurate mouse models of the deletion that causes 22q11DS. We conclude that "modeling a model", in this case 22q11DS as a model for idiopathic ASD, ADHD and SCZ, as well as other behavioral disorders like anxiety frequently seen in 22q11DS patients, in genetically engineered mice provides a foundation for understanding the causes and improving diagnosis and therapy for these disorders of cortical circuit development.
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Affiliation(s)
- Daniel W Meechan
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States
| | - Thomas M Maynard
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States
| | - Eric S Tucker
- Department of Neurobiology and Anatomy, Neuroscience Graduate Program, and Center for Neuroscience, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Alejandra Fernandez
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States
| | - Beverly A Karpinski
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States
| | - Lawrence A Rothblat
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States; Department of Psychology, The George Washington University, Washington, DC, United States
| | - Anthony-S LaMantia
- Institute for Neuroscience, Department of Pharmacology & Physiology, The George Washington University, Washington, DC, United States.
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Vergaelen E, Swillen A, Van Esch H, Claes S, Van Goethem G, Devriendt K. 3 generation pedigree with paternal transmission of the 22q11.2 deletion syndrome: Intrafamilial phenotypic variability. Eur J Med Genet 2015; 58:244-8. [PMID: 25655469 DOI: 10.1016/j.ejmg.2015.01.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 01/20/2015] [Indexed: 12/31/2022]
Abstract
In this case report, we present a paternal transmission of a classic 3 Mb 22q11.2 deletion syndrome (22q11.2 DS) in a 3 generation family. In this family a young girl, her father, her uncle and her grandfather were diagnosed with this disorder. All carriers showed phenotypic expression, there were no unaffected siblings in the second or third generation. Presenting symptoms in the patient in first generation (grandfather) were psoriatic arthritis, thrombocytopenia and a right aortic arch. There was no intellectual disability. The second generation uncle was known with a severe intellectual disability, mild facial characteristics, a septal defect and a clubfoot, whereas the second generation father had a tetralogy of Fallot, no intellectual disability and minimal facial characteristics. The third generation daughter had a moderate intellectual disability, hypernasal speech, triphalangeal thumb, severe speech and language development delay, pronounced facial characteristics and a diagnosis of ADHD. It was notable that the expression in the two brothers of the second generation gives two very different clinical phenotypes with a severe intellectual disability in the oldest brother. This report describes a pronounced clinical variability in a 3 generation familial 22q11.2 deletion with paternal transmission. We can assume that several mechanisms play an important role in the heterogeneity and part of the answer should be found in the genetic background underlying the 22q11.2 deletion. In addition in this family the neuropsychiatric phenotype and intellectual disability seem to be associated with a lower level of social and occupational functioning while a congenital heart disease does not. This clinical report illustrates that a detailed description of these patients can be very informative and still increase the knowledge on this heterogeneous syndrome. For the clinicians working with these patients it emphasizes the need for a multidisciplinary approach that takes into account the individual needs.
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Affiliation(s)
- Elfi Vergaelen
- Centre of Human Genetics, University Hospitals Leuven, Belgium & Department of Human Genetics, KU Leuven, Belgium; Department of Adult Psychiatry, University Psychiatric Centre, KU Leuven, Belgium.
| | - Ann Swillen
- Centre of Human Genetics, University Hospitals Leuven, Belgium & Department of Human Genetics, KU Leuven, Belgium; Department of Kinesiology and Rehabilitation Sciences, KU Leuven, Belgium
| | - Hilde Van Esch
- Centre of Human Genetics, University Hospitals Leuven, Belgium & Department of Human Genetics, KU Leuven, Belgium
| | - Stephan Claes
- Department of Adult Psychiatry, University Psychiatric Centre, KU Leuven, Belgium
| | - Gert Van Goethem
- Het GielsBos, Gierle, Belgium and Department of Neurology, University Hospital of Antwerpen (UZA), Antwerpen, Belgium
| | - Koenraad Devriendt
- Centre of Human Genetics, University Hospitals Leuven, Belgium & Department of Human Genetics, KU Leuven, Belgium
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Hu H, Yao H, Dong Y, Long Y, Xu L, Hu B, Xu G, Liang Z. Distinct karyotypes in two offspring of a man with jumping translocation karyotype 45,XY,der(16)t(16;22)(q24;q11.2), -22 [59]/45,XY,der(1)t(1;22)(p36;q11.2), -22 [11]/45,XY,der(22)t(22;22)(p13;q11.2), -22 [10]. Am J Med Genet A 2014; 164A:2048-53. [PMID: 24737738 DOI: 10.1002/ajmg.a.36560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 03/10/2014] [Indexed: 11/07/2022]
Abstract
We examined a man and his daughter, who both had different jumping translocation karyotypes. The man's wife was pregnant and had been referred for prenatal diagnosis of the fetus. The karyotype of the husband's peripheral blood lymphocytes was 45,XY,der(16)t(16;22)(q24;q11.2), -22 [59]/45,XY,der(1)t(1;22)(p36;q11.2), -22 [11]/45,XY,der(22)t(22;22)(p13;q11.2), -22 [10]. The karyotype of the daughter's peripheral blood lymphocytes was 45,XX,der(16)t(16;22)(q24;q11.2), -22 [45]/45,XX,der(9)t(9;22)(q34;q11.2), -22 [30]/45,XX,der(5)t(5;22)(q35;q11.2), -22 [25]. The wife and the fetus both had a normal karyotype. To the best of our knowledge, the present familial transmitted jumping translocation has not been previously described and the jumping translocation in the husband and daughter did not cause any phenotypic abnormalities.
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Affiliation(s)
- Hua Hu
- Center for Prenatal Diagnosis, Department of Obstetrics and Gynecology, Southwest Hospital, Third Military Medical University, ChongQing, People's Republic of China
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Mussotter T, Bengesser K, Högel J, Cooper DN, Kehrer-Sawatzki H. Population-specific differences in gene conversion patterns between human SUZ12 and SUZ12P are indicative of the dynamic nature of interparalog gene conversion. Hum Genet 2014; 133:383-401. [PMID: 24385046 DOI: 10.1007/s00439-013-1410-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 12/08/2013] [Indexed: 11/29/2022]
Abstract
Nonallelic homologous gene conversion (NAHGC) resulting from interparalog recombination without crossover represents an important influence on the evolution of duplicated sequences in the human genome. In 17q11.2, different paralogous sequences mediate large NF1 deletions by nonallelic homologous recombination with crossover (NAHR). Among these paralogs are SUZ12 and its pseudogene SUZ12P which harbour the breakpoints of type-2 (1.2-Mb) NF1 deletions. Such deletions are caused predominantly by mitotic NAHR since somatic mosaicism with normal cells is evident in most patients. Investigating whether SUZ12 and SUZ12P have also been involved in NAHGC, we observed gene conversion tracts between these paralogs in both Africans (AFR) and Europeans (EUR). Since germline type-2 NF1 deletions resulting from meiotic NAHR are very rare, the vast majority of the gene conversion tracts in SUZ12 and SUZ12P are likely to have resulted from mitotic recombination during premeiotic cell divisions of germ cells. A higher number of gene conversion tracts were noted within SUZ12 and SUZ12P in AFR as compared to EUR. Further, the distinctive signature of NAHGC (a high number of SNPs per paralog and a high number of shared SNPs between paralogs), a characteristic of many actively recombining paralogs, was observed in both SUZ12 and SUZ12P but only in AFR and not in EUR. A novel polymorphic 2.3-kb deletion in SUZ12P was identified which exhibited a high allele frequency in EUR. We postulate that this interparalog structural difference, together with low allelic recombination rates, could have caused a reduction in NAHGC between SUZ12 and SUZ12P during human evolution.
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Affiliation(s)
- Tanja Mussotter
- Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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Castronovo C, Valtorta E, Crippa M, Tedoldi S, Romitti L, Amione MC, Guerneri S, Rusconi D, Ballarati L, Milani D, Grosso E, Cavalli P, Giardino D, Bonati MT, Larizza L, Finelli P. Design and validation of a pericentromeric BAC clone set aimed at improving diagnosis and phenotype prediction of supernumerary marker chromosomes. Mol Cytogenet 2013; 6:45. [PMID: 24171812 PMCID: PMC4176193 DOI: 10.1186/1755-8166-6-45] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 10/08/2013] [Indexed: 12/17/2022] Open
Abstract
Background Small supernumerary marker chromosomes (sSMCs) are additional, structurally abnormal chromosomes, generally smaller than chromosome 20 of the same metaphase spread. Due to their small size, they are difficult to characterize by conventional cytogenetics alone. In regard to their clinical effects, sSMCs are a heterogeneous group: in particular, sSMCs containing pericentromeric euchromatin are likely to be associated with abnormal outcomes, although exceptions have been reported. To improve characterization of the genetic content of sSMCs, several approaches might be applied based on different molecular and molecular-cytogenetic assays, e.g., fluorescent in situ hybridization (FISH), array-based comparative genomic hybridization (array CGH), and multiplex ligation-dependent probe amplification (MLPA). To provide a complementary tool for the characterization of sSMCs, we constructed and validated a new, FISH-based, pericentromeric Bacterial Artificial Chromosome (BAC) clone set that with a high resolution spans the most proximal euchromatic sequences of all human chromosome arms, excluding the acrocentric short arms. Results By FISH analysis, we assayed 561 pericentromeric BAC probes and excluded 75 that showed a wrong chromosomal localization. The remaining 486 probes were used to establish 43 BAC-based pericentromeric panels. Each panel consists of a core, which with a high resolution covers the most proximal euchromatic ~0.7 Mb (on average) of each chromosome arm and generally bridges the heterochromatin/euchromatin junction, as well as clones located proximally and distally to the core. The pericentromeric clone set was subsequently validated by the characterization of 19 sSMCs. Using the core probes, we could rapidly distinguish between heterochromatic (1/19) and euchromatic (11/19) sSMCs, and estimate the euchromatic DNA content, which ranged from approximately 0.13 to more than 10 Mb. The characterization was not completed for seven sSMCs due to a lack of information about the covered region in the reference sequence (1/19) or sample insufficiency (6/19). Conclusions Our results demonstrate that this pericentromeric clone set is useful as an alternative tool for sSMC characterization, primarily in cases of very small SMCs that contain either heterochromatin exclusively or a tiny amount of euchromatic sequence, and also in cases of low-level or cryptic mosaicism. The resulting data will foster knowledge of human proximal euchromatic regions involved in chromosomal imbalances, thereby improving genotype–phenotype correlations.
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Affiliation(s)
- Chiara Castronovo
- Laboratorio di Citogenetica Medica e Genetica Molecolare, IRCCS Istituto Auxologico Italiano, via Ariosto 13, 20145, Milano, Italy.
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13
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Costain G, Bassett AS. Clinical applications of schizophrenia genetics: genetic diagnosis, risk, and counseling in the molecular era. APPLICATION OF CLINICAL GENETICS 2012; 5:1-18. [PMID: 23144566 PMCID: PMC3492098 DOI: 10.2147/tacg.s21953] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Schizophrenia is a complex neuropsychiatric disease with documented clinical and genetic heterogeneity, and evidence for neurodevelopmental origins. Driven by new genetic technologies and advances in molecular medicine, there has recently been concrete progress in understanding some of the specific genetic causes of this serious psychiatric illness. In particular, several large rare structural variants have been convincingly associated with schizophrenia, in targeted studies over two decades with respect to 22q11.2 microdeletions, and more recently in large-scale, genome-wide case-control studies. These advances promise to help many families afflicted with this disease. In this review, we critically appraise recent developments in the field of schizophrenia genetics through the lens of immediate clinical applicability. Much work remains in translating the recent surge of genetic research discoveries into the clinic. The epidemiology and basic genetic parameters (such as penetrance and expression) of most genomic disorders associated with schizophrenia are not yet well characterized. To date, 22q11.2 deletion syndrome is the only established genetic subtype of schizophrenia of proven clinical relevance. We use this well-established association as a model to chart the pathway for translating emerging genetic discoveries into clinical practice. We also propose new directions for research involving general genetic risk prediction and counseling in schizophrenia.
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Affiliation(s)
- Gregory Costain
- Clinical Genetics Research Program, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada ; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
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14
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Zickler AM, Hampp S, Messiaen L, Bengesser K, Mussotter T, Roehl AC, Wimmer K, Mautner VF, Kluwe L, Upadhyaya M, Pasmant E, Chuzhanova N, Kestler HA, Högel J, Legius E, Claes K, Cooper DN, Kehrer-Sawatzki H. Characterization of the nonallelic homologous recombination hotspot PRS3 associated with type-3 NF1 deletions. Hum Mutat 2011; 33:372-83. [PMID: 22045503 DOI: 10.1002/humu.21644] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 10/06/2011] [Indexed: 12/21/2022]
Abstract
Nonallelic homologous recombination (NAHR) is the major mechanism underlying recurrent genomic rearrangements, including the large deletions at 17q11.2 that cause neurofibromatosis type 1 (NF1). Here, we identify a novel NAHR hotspot, responsible for type-3 NF1 deletions that span 1.0 Mb. Breakpoint clustering within this 1-kb hotspot, termed PRS3, was noted in 10 of 11 known type-3 NF1 deletions. PRS3 is located within the LRRC37B pseudogene of the NF1-REPb and NF1-REPc low-copy repeats. In contrast to other previously characterized NAHR hotspots, PRS3 has not developed on a preexisting allelic homologous recombination hotspot. Furthermore, the variation pattern of PRS3 and its flanking regions is unusual since only NF1-REPc (and not NF1-REPb) is characterized by a high single nucleotide polymorphism (SNP) frequency, suggestive of unidirectional sequence transfer via nonallelic homologous gene conversion (NAHGC). By contrast, the previously described intense NAHR hotspots within the CMT1A-REPs, and the PRS1 and PRS2 hotspots underlying type-1 NF1 deletions, experience frequent bidirectional sequence transfer. PRS3 within NF1-REPc was also found to be involved in NAHGC with the LRRC37B gene, the progenitor locus of the LRRC37B-P duplicons, as indicated by the presence of shared SNPs between these loci. PRS3 therefore represents a weak (and probably evolutionarily rather young) NAHR hotspot with unique properties.
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Affiliation(s)
- Antje M Zickler
- Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, Ulm, Germany
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15
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Cognitive, behavioural and psychiatric phenotype in 22q11.2 deletion syndrome. Behav Genet 2011; 41:403-12. [PMID: 21573985 DOI: 10.1007/s10519-011-9468-z] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 04/09/2011] [Indexed: 01/17/2023]
Abstract
22q11.2 Deletion syndrome has become an important model for understanding the pathophysiology of neurodevelopmental conditions, particularly schizophrenia which develops in about 20-25% of individuals with a chromosome 22q11.2 microdeletion. From the initial discovery of the syndrome, associated developmental delays made it clear that changes in brain development were a key part of the expression. Once patients were followed through childhood into adult years, further neurobehavioural phenotypes became apparent, including a changing cognitive profile, anxiety disorders and seizure diathesis. The variability of expression is as wide as for the myriad physical features associated with the syndrome, with the addition of evolving phenotype over the developmental trajectory. Notably, variability appears unrelated to length of the associated deletion. Several mouse models of the deletion have been engineered and are beginning to reveal potential molecular mechanisms for the cognitive and behavioural phenotypes observable in animals. Both animal and human studies hold great promise for further discoveries relevant to neurodevelopment and associated cognitive, behavioural and psychiatric disorders.
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Roehl AC, Vogt J, Mussotter T, Zickler AN, Spöti H, Högel J, Chuzhanova NA, Wimmer K, Kluwe L, Mautner VF, Cooper DN, Kehrer-Sawatzki H. Intrachromosomal mitotic nonallelic homologous recombination is the major molecular mechanism underlying type-2 NF1 deletions. Hum Mutat 2011; 31:1163-73. [PMID: 20725927 DOI: 10.1002/humu.21340] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Nonallelic homologous recombination (NAHR) is responsible for the recurrent rearrangements that give rise to genomic disorders. Although meiotic NAHR has been investigated in multiple contexts, much less is known about mitotic NAHR despite its importance for tumorigenesis. Because type-2 NF1 microdeletions frequently result from mitotic NAHR, they represent a good model in which to investigate the features of mitotic NAHR. We have used microsatellite analysis and SNP arrays to distinguish between the various alternative recombinational possibilities, thereby ascertaining that 17 of 18 type-2 NF1 deletions, with breakpoints in the SUZ12 gene and its highly homologous pseudogene, originated via intrachromosomal recombination. This high proportion of intrachromosomal NAHR causing somatic type-2 NF1 deletions contrasts with the interchromosomal origin of germline type-1 NF1 microdeletions, whose breakpoints are located within the NF1-REPs (low-copy repeats located adjacent to the SUZ12 sequences). Further, meiotic NAHR causing type-1 NF1 deletions occurs within recombination hotspots characterized by high GC-content and DNA duplex stability, whereas the type-2 breakpoints associated with the mitotic NAHR events investigated here do not cluster within hotspots and are located within regions of significantly lower GC-content and DNA stability. Our findings therefore point to fundamental mechanistic differences between the determinants of mitotic and meiotic NAHR.
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A deletion and a duplication in distal 22q11.2 deletion syndrome region. Clinical implications and review. BMC MEDICAL GENETICS 2009; 10:48. [PMID: 19490635 PMCID: PMC2700091 DOI: 10.1186/1471-2350-10-48] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 06/02/2009] [Indexed: 12/31/2022]
Abstract
Background Individuals affected with DiGeorge and Velocardiofacial syndromes present with both phenotypic diversity and variable expressivity. The most frequent clinical features include conotruncal congenital heart defects, velopharyngeal insufficiency, hypocalcemia and a characteristic craniofacial dysmorphism. The etiology in most patients is a 3 Mb recurrent deletion in region 22q11.2. However, cases of infrequent deletions and duplications with different sizes and locations have also been reported, generally with a milder, slightly different phenotype for duplications but with no clear genotype-phenotype correlation to date. Methods We present a 7 month-old male patient with surgically corrected ASD and multiple VSDs, and dysmorphic facial features not clearly suggestive of 22q11.2 deletion syndrome, and a newborn male infant with cleft lip and palate and upslanting palpebral fissures. Karyotype, FISH, MLPA, microsatellite markers segregation studies and SNP genotyping by array-CGH were performed in both patients and parents. Results Karyotype and FISH with probe N25 were normal for both patients. MLPA analysis detected a partial de novo 1.1 Mb deletion in one patient and a novel partial familial 0.4 Mb duplication in the other. Both of these alterations were located at a distal position within the commonly deleted region in 22q11.2. These rearrangements were confirmed and accurately characterized by microsatellite marker segregation studies and SNP array genotyping. Conclusion The phenotypic diversity found for deletions and duplications supports a lack of genotype-phenotype correlation in the vicinity of the LCRC-LCRD interval of the 22q11.2 chromosomal region, whereas the high presence of duplications in normal individuals supports their role as polymorphisms. We suggest that any hypothetical correlation between the clinical phenotype and the size and location of these alterations may be masked by other genetic and/or epigenetic modifying factors.
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1.4Mb recurrent 22q11.2 distal deletion syndrome, two new cases expand the phenotype. Eur J Med Genet 2008; 51:646-50. [DOI: 10.1016/j.ejmg.2008.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Accepted: 07/13/2008] [Indexed: 12/21/2022]
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Bassett AS, Marshall CR, Lionel AC, Chow EWC, Scherer SW. Copy number variations and risk for schizophrenia in 22q11.2 deletion syndrome. Hum Mol Genet 2008; 17:4045-53. [PMID: 18806272 PMCID: PMC2638574 DOI: 10.1093/hmg/ddn307] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
22q11.2 Deletion Syndrome (22q11.2DS) is a common microdeletion syndrome with congenital and late-onset features. Testing for the genomic content of copy number variations (CNVs) may help elucidate the 22q11.2 deletion mechanism and the variable clinical expression of the syndrome including the high (25%) risk for schizophrenia. We used genome-wide microarrays to assess CNV content and the parental origin of 22q11.2 deletions in a cohort of 100 adults with 22q11.2DS (44 with schizophrenia) and controls. 22q11.2DS subjects with schizophrenia failed to exhibit de novo CNVs or any excess of novel inherited CNVs outside the 22q11.2 region. There were no significant effects of parental origin of the 22q11.2 deletion, deletion length, parental age or family history on expression of schizophrenia. There was no evidence for a general increase of de novo CNVs in 22q11.2DS. A novel finding was the relative paucity of males with de novo 22q11.2 deletions of paternal origin (P = 0.019). The Y chromosome may play a mediating role in the mechanism of 22q11.2 deletion events during spermatogenesis, resulting in the previously observed excess of maternal de novo 22q11.2 deletions. Hemizygosity of the 22q11.2 region appears to be the major CNV-related risk factor for schizophrenia in 22q11.2DS. The results reinforce the need for further efforts to identify specific molecular mechanisms underlying this expression and to identify the 1% of patients with schizophrenia who carry 22q11.2 deletions.
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Affiliation(s)
- Anne S Bassett
- Clinical Genetics Research Program, Centre for Addiction and Mental Health, 1001 Queen Street West, Toronto, Ontario M6J 1H4, Canada.
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20
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Xu J, Fan YS, Siu VM. A child with features of Goldenhar syndrome and a novel 1.12 Mb deletion in 22q11.2 by cytogenetics and oligonucleotide array CGH: is this a candidate region for the syndrome? Am J Med Genet A 2008; 146A:1886-9. [PMID: 18553512 DOI: 10.1002/ajmg.a.32359] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- J Xu
- Cytogenetics Lab, London Health Sciences Centre, University of Western Ontario, Canada.
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Schluth-Bolard C, Till M, Edery P, Sanlaville D. [New chromosomal syndromes]. ACTA ACUST UNITED AC 2008; 56:380-7. [PMID: 18467039 DOI: 10.1016/j.patbio.2008.03.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 03/14/2008] [Indexed: 10/22/2022]
Abstract
Mental retardation occurs in 2-3% of the general population either in isolation or in combination with facial dysmorphism and/or malformations. Chromosomal abnormalities are a most common etiology. Karyotype displays chromosome aberrations in about 10% of patients but it has a limited resolution (5 Mb). Recently, the development of new molecular cytogenetic tools, especially array CGH, allowed to detect smaller abnormalities and increased the diagnosis capability of 15-20%. Among these newly detected rearrangements, some of them are recurrent and define new recognized syndromes. We will first briefly explain the non-allelic homologous recombination (NAHR) mechanism that underlines the origin of recurrent microdeletions and microduplications. Then we will describe eight new syndromes, four microdeletions (del 17q21.31, del 3q29, del 15q24, del 2q32.3q33) and four microduplications (dup 22q11.2, dup 7q11.23, dup 17p11.2, duplication of MECP2). A better knowledge of these new recurrent chromosomal syndromes will allow to improve care for patients, to develop targeted chromosomal diagnosis and to identify genes involved in neurocognitive functions.
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Affiliation(s)
- C Schluth-Bolard
- Service de cytogénétique constitutionnelle, hospices civils de Lyon, centre de biologie et de pathologie Est, 59, boulevard Pinel, 69677 Bron, cedex, France
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Khil PP, Camerini-Otero RD. Variation in patterns of human meiotic recombination. GENOME DYNAMICS 2008; 5:117-127. [PMID: 18948711 DOI: 10.1159/000166623] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the last 30 years it has become evident that patterns of meiotic recombination can be highly variable among individuals. The evidence comes from both low and high resolution analyses of hotspots of recombination in human and other species. In addition, a comparison of the recombination profiles in closely related species such as human and chimpanzee reveals essentially no correlation in the position of hotspots. Although the variation in hotspots of meiotic recombination is clearly documented, the mechanisms responsible for such variation are far from being understood. Here we will review the available evidence of natural variation in meiotic recombination and will discuss potential implications of this variation on the functional mechanisms of crossover formation and control.
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Affiliation(s)
- P P Khil
- Genetics and Biochemistry Branch, NIDDK, National Institutes of Health, Bethesda, Md., USA
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