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Waldvogel SM, Posey JE, Goodell MA. Human embryonic genetic mosaicism and its effects on development and disease. Nat Rev Genet 2024; 25:698-714. [PMID: 38605218 PMCID: PMC11408116 DOI: 10.1038/s41576-024-00715-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2024] [Indexed: 04/13/2024]
Abstract
Nearly every mammalian cell division is accompanied by a mutational event that becomes fixed in a daughter cell. When carried forward to additional cell progeny, a clone of variant cells can emerge. As a result, mammals are complex mosaics of clones that are genetically distinct from one another. Recent high-throughput sequencing studies have revealed that mosaicism is common, clone sizes often increase with age and specific variants can affect tissue function and disease development. Variants that are acquired during early embryogenesis are shared by multiple cell types and can affect numerous tissues. Within tissues, variant clones compete, which can result in their expansion or elimination. Embryonic mosaicism has clinical implications for genetic disease severity and transmission but is likely an under-recognized phenomenon. To better understand its implications for mosaic individuals, it is essential to leverage research tools that can elucidate the mechanisms by which expanded embryonic variants influence development and disease.
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Affiliation(s)
- Sarah M Waldvogel
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, USA
- Graduate Program in Cancer and Cell Biology, Baylor College of Medicine, Houston, TX, USA
| | - Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Margaret A Goodell
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
- Graduate Program in Cancer and Cell Biology, Baylor College of Medicine, Houston, TX, USA.
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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Krishna S, Fasaludeen A, Jose M, Banerjee M, Sundaram S, Radhakrishnan A, Menon RN. Impact of variant subtype on electro-clinical phenotype of Dravet syndrome- a South Indian cohort study. Seizure 2024; 115:81-86. [PMID: 38232648 DOI: 10.1016/j.seizure.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/21/2023] [Accepted: 01/09/2024] [Indexed: 01/19/2024] Open
Abstract
OBJECTIVE We aimed to compare the electroclinical correlates of truncating and missense variants of SCN1A variants in children with Dravet syndrome (DS) and to determine phenotypic features in relation to variants identified and seizure outcomes. METHODS A single center prospective study was carried out on a South Indian cohort. Patients below 18 years of age who met the clinical criteria for DS who had undergone genetic testing and completed a minimum of one year follow up were included. We compared the differences in clinical profile, seizure outcome, developmental characteristics and anti-seizure medication (ASM) responsiveness profiles between patients with missense and truncating variants. RESULTS Out of a total of 3967 children with drug-resistant epilepsy during the period 2015-2021, 49 patients who fulfilled the inclusion criteria were studied. Thirty-seven had positive genetic tests, out of which 29 were SCN1A variants and 9 were other novel variants. The proportion of missense (14; 48.3%) and truncating SCN1A variants (15; 51.7%) was similar. A significant trend for developing multiple seizure types was noted among children with truncating variants (p = 0.035) and seizure freedom was more likely among children with missense variants (p = 0.042). All patients with truncating variants had ASM resistant epilepsy (p = 0.020). Developmental outcomes did not differ between the variant subtypes. CONCLUSION Our results show that children harbouring missense variants demonstrated a significantly lower propensity for multiple seizure subtypes and a higher proportion with seizure freedom. However developmental implications appear to be independent of variant subtype.
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Affiliation(s)
- S Krishna
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
| | - Alfiya Fasaludeen
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
| | - Manna Jose
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
| | - Moinak Banerjee
- Human Molecular Genetics Laboratory, Rajiv Gandhi Centre for Biotechnology, Trivandrum, Kerala, India
| | - Soumya Sundaram
- Comprehensive Care Centre for Neuodevelopmental Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
| | - Ashalatha Radhakrishnan
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
| | - Ramshekhar N Menon
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India; Comprehensive Care Centre for Neuodevelopmental Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India.
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3
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Zeng B, Zhang H, Lu Q, Fu Q, Yan Y, Lu W, Ma P, Feng C, Qin J, Luo L, Yang B, Zou Y, Liu Y. Identification of five novel SCN1A variants. Front Behav Neurosci 2023; 17:1272748. [PMID: 38025388 PMCID: PMC10663289 DOI: 10.3389/fnbeh.2023.1272748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 10/27/2023] [Indexed: 12/01/2023] Open
Abstract
Background Epilepsy is characterized by recurrent unprovoked seizures. Mutations in the voltage-gated sodium channel alpha subunit 1 (SCN1A) gene are the main monogenic cause of epilepsy. Type and location of variants make a huge difference in the severity of SCN1A disorder, ranging from the mild phenotype (genetic epilepsy with febrile seizures plus, GEFS+) to the severe phenotype (developmental and epileptic encephalopathies, DEEs). Dravet Syndrome (DS) is an infantile-onset DEE, characterized by drug-resistant epilepsy and temperature sensitivity or febrile seizures. Genetic test results reveal SCN1A variants are positive in 80% DS patients and DS is mainly caused by de novo variants. Methods Trio-whole exome sequencing (WES) was used to detect variants which were associated with clinical phenotype of five probands with epilepsy or twitching. Then, Sanger sequencing was performed to validate the five novel SCN1A variants and segregation analysis. After analyzing the location of five SCN1A variants, the pathogenic potential was assessed. Results In this study, we identified five novel SCN1A variants (c.4224G > C, c.3744_3752del, c.209del, c.5727_5734delTTTAAAACinsCTTAAAAAG and c.5776delT) as the causative variants. In the five novel SCN1A variants, four were de novo and the remaining one was inherited. All novel variants would be classified as "pathogenic" or "likely pathogenic." Conclusion The five novel SCN1A variants will enrich the SCN1A mutations database and provide the corresponding reference data for the further genetic counseling.
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Affiliation(s)
- Baitao Zeng
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Haoyi Zhang
- School of Public Health, Nanchang University, Nanchang, China
| | - Qing Lu
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Qingzi Fu
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Yang Yan
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Wan Lu
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Pengpeng Ma
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Chuanxin Feng
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Jiawei Qin
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Laipeng Luo
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Bicheng Yang
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Yongyi Zou
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
| | - Yanqiu Liu
- Department of Medical Genetics, Jiangxi Maternal and Child Health Hospital, Nanchang, China
- Jiangxi Provincial Key Laboratory of Birth Defect for Prevention and Control, Jiangxi Maternal and Child Health Hospital, Nanchang, China
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Chen J, Chen Y, Yang Y, Niu X, Zhang J, Zeng Q, Liu A, Xu X, Yang X, Li S, Yang X, Wang Y, Zhang Y. Detecting genomic mosaicism in "de novo" genetic epilepsy by amplicon-based deep sequencing. J Hum Genet 2023; 68:73-80. [PMID: 36482122 DOI: 10.1038/s10038-022-01103-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 11/28/2022] [Accepted: 11/29/2022] [Indexed: 12/13/2022]
Abstract
AIM To investigate the occurrence of mosaicism in epilepsy probands and their parents using amplicon-based deep sequencing (ADS). METHODS Patients were recruited from the outpatient of Peking University First Hospital. Two hundred and sixty-four probands with pathogenic variants tested by next-generation sequencing (NGS) were enrolled. RESULTS Mosaic variants were detected in seventeen disease-associated genes from 20 probands, 5 paternal, and 6 maternal parents. The frequency of mosaicism was 11.74% (31/264). Mosaicism in 11 genes was identified from 20 probands with the mutant allelic fractions (MAFs) of 12.95-38.00% in autosomal dominant genes. Five paternal mosaicisms were identified in genes with a MAF of 6.30-20.99%, and six maternal mosaic individuals with a MAF of 2.07-21.90%. Only four mosaic parents had milder seizure history. The affected sibling had the same phenotype consistent with that of the proband, who inherited the variant of SLC1A2 or STXBP1 from their unaffected mosaic mothers, respectively. INTERPRETATION Mosaic phenomenon is not rare in families with epilepsy. Phenotypes of mosaic parents were milder or normal. Mosaicism detection is helpful to identify the mutation origin and it provides a theoretical basis for prenatal diagnosis of family reproduction. ADS is a reliable way of mosaicism detection for clinical application.
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Affiliation(s)
- Jiaoyang Chen
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Yi Chen
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Ying Yang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Xueyang Niu
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Jing Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Qi Zeng
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Aijie Liu
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Xiaojing Xu
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Xiaoxu Yang
- Center for Bioinformatics, Peking University, Beijing, 100871, China
| | - Shupin Li
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Xiaoling Yang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China
| | - Yi Wang
- Department of Neurology, National Epilepsy Center, Children's Hospital of Fudan University, National Children's Medical Center, Shanghai, 201102, China
| | - Yuehua Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, 100034, China.
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Deng H, Zhang Y, Ding J, Wang F. Detection of Very Low-Level Somatic Mosaic COL4A5 Splicing Variant in Asymptomatic Female Using Droplet Digital PCR. Front Med (Lausanne) 2022; 9:847056. [PMID: 35360741 PMCID: PMC8963732 DOI: 10.3389/fmed.2022.847056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Accepted: 02/09/2022] [Indexed: 12/02/2022] Open
Abstract
Background Alport syndrome is a hereditary glomerulopathy featured by haematuria, proteinuria, and progressive renal failure. X-linked Alport syndrome (XLAS) due to COL4A5 disease-causing variants is the most common form. In the case of XLAS resulting from 10–18% presumed de novo COL4A5 disease-causing variants, there are only a few studies for mosaicism in the probands or parents. Very low-level (<1.0%) somatic mosaicism for COL4A5 disease-causing variants has not been published. Materials and Methods Chinese XLAS families with suspected parental mosaicism were enrolled in the present study to evaluate the forms of mosaicism, to offer more appropriate genetic counseling. PCR and direct sequencing were used to detect COL4A5 disease-causing variants harbored by the affected probands in parental multi-tissue DNAs (peripheral blood, urine sediments, saliva, hair), and droplet digital PCR (ddPCR) was used to quantify the mutant COL4A5 allelic fractions in parental different samples such as peripheral blood, saliva, and urine sediments. Results A Chinese asymptomatic female with suspected somatic and germline mosaicism was enrolled in the present study. She gave birth to two boys with XLAS caused by a hemizygous disease-causing variant c. 2245-1G>A in COL4A5 (NM_033380) intron 28, whereas this disease-causing variant was not detected in genomic DNA extracted from peripheral blood leukocytes in the woman using Sanger sequencing. She had multiple normal urine test results, and continuous linear immunofluorescence staining of α2 (IV) and α5 (IV) chains of skin tissue. Sanger sequencing demonstrated that COL4A5 disease-causing variant c. 2245-1G>A was not detected in her genomic DNAs isolated from urine sediments, saliva, and hair roots. Using ddPCR, the wild-type and mutant-type (c.2245-1G>A) COL4A5 was identified in the female's genomic DNAs isolated from peripheral blood, saliva, and urine sediments. The mutant allelic fractions in these tissues were 0.26% (peripheral blood), 0.73% (saliva), and 1.39% (urine), respectively. Conclusions Germline and very low-level somatic mosaicism for a COL4A5 splicing variant was detected in an asymptomatic female, which highlights that parental mosaicism should be excluded when a COL4A5 presumed de novo disease-causing variant is detected.
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Molecular diagnosis of epileptic encephalopathy of the first year of life applying a customized gene panel in a group of Argentinean patients. Epilepsy Behav 2020; 111:107322. [PMID: 32702657 DOI: 10.1016/j.yebeh.2020.107322] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/01/2020] [Accepted: 07/04/2020] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The aim of this study was to perform a molecular characterization of 17 Argentinean pediatric patients with diagnosis of having epileptic encephalopathies (EEs) of the first year of life without known etiology, applying next-generation sequencing (NGS). METHODS We included 17 patients with EE with age of onset under 12 months without known etiology after ruling out structural abnormalities, metabolic disorders, and large chromosomal abnormalities. They presented with the following clinical phenotypes: Dravet syndrome (DS; n: 7), epilepsy of infancy with migrating focal seizures (EIMFS; n: 3), West syndrome (WS; n: 2), and undetermined epileptic encephalopathy (UEE; n: 5). Neurologic examinations, seizure semiology, brain magnetic resonance imaging, and standard electroencephalography (EEG) or video-EEG studies were performed in all cases. Using a custom amplicon strategy, we designed an NGS panel to study 47 genes associated with EEs. RESULTS Pathogenic variants were detected in 8 cases (47%), including seven novel pathogenic variants and one previously reported as being pathogenic. The pathogenic variants were identified in 6 patients with DS (SCN1A gene), one with EIMFS (SCN2A gene), and one with UEE (SLC2A1 gene). Nonrelevant variants were identified in the patients with WS. CONCLUSION We demonstrated the feasibility of an NGS-gene panel approach for the analysis of patients with EE in our setting. A genetic diagnosis was achieved in nearly 50% of patients, 87% of them presenting with nonpreviously reported variants. The early identification of the underlying causative genetic alteration will be a valuable tool for providing prognostic information and genetic counselling and also to improve therapeutic decisions in Argentinean patients.
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Abstract
Epilepsy encompasses a group of heterogeneous brain diseases that affect more than 50 million people worldwide. Epilepsy may have discernible structural, infectious, metabolic, and immune etiologies; however, in most people with epilepsy, no obvious cause is identifiable. Based initially on family studies and later on advances in gene sequencing technologies and computational approaches, as well as the establishment of large collaborative initiatives, we now know that genetics plays a much greater role in epilepsy than was previously appreciated. Here, we review the progress in the field of epilepsy genetics and highlight molecular discoveries in the most important epilepsy groups, including those that have been long considered to have a nongenetic cause. We discuss where the field of epilepsy genetics is moving as it enters a new era in which the genetic architecture of common epilepsies is starting to be unraveled.
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Affiliation(s)
- Piero Perucca
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, Victoria 3000, Australia.,Departments of Medicine and Neurology, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, Victoria 3050, Australia.,Department of Neurology, Alfred Health, Melbourne, Victoria 3000, Australia
| | - Melanie Bahlo
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Samuel F Berkovic
- Epilepsy Research Centre, Department of Medicine, Austin Health, The University of Melbourne, Melbourne, Victoria 3084, Australia;
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Mei D, Cetica V, Marini C, Guerrini R. Dravet syndrome as part of the clinical and genetic spectrum of sodium channel epilepsies and encephalopathies. Epilepsia 2020; 60 Suppl 3:S2-S7. [PMID: 31904125 DOI: 10.1111/epi.16054] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/06/2019] [Accepted: 05/08/2019] [Indexed: 01/01/2023]
Abstract
Dravet syndrome is the most studied form of genetic epilepsy. It has now been clarified that the clinical spectrum of the syndrome does not have firmly established boundaries. The core phenotype is characterized by intractable, mainly clonic, seizures precipitated by increased body temperature with onset in the first year of life and subsequent appearance of multiple seizures types still precipitated by, but not confined to, hyperthermia. Cognitive impairment is invariably present when the full syndrome is manifested. This complex of symptoms is related to mutations in the SCN1A gene, which are often de novo and constitutional but can also be inherited from a parent with less severe clinical manifestations or be present as somatic mosaicism. Inheritance from less severely affected individuals, at times only having experienced a few febrile seizures, and differences in severity, even within the same family, with a subset of patients only showing fragments of the syndrome, testify to a remarkable phenotypic heterogeneity as far as severity, but less so clinical phenomenology, are concerned. This characteristic, together with underascertainment of SCN1A mutations due to human errors or technical limitations in uncovering alternative pathogenic molecular mechanisms, such as genomic rearrangements or poison exons, has contributed to making clinicians and geneticists suspicious that Dravet syndrome may be caused by more than one gene. This opinion has been further amplified by the description of other genetic disorders, such as PCDH19- or CHD2-related epilepsy, whose phenotypes have included fragments of the Dravet phenotypic spectrum, and by the suboptimal characterization of phenotypes associated with mutations in SCN1B, HCN1, KCN2A, GABRA1, GABRG2, and STXBP1. The SCN1A gene-Dravet syndrome association is in our opinion highly specific. However, because the syndrome spectrum is wide, fragments of it can at times also be manifested in other genetic epilepsy syndromes, thereby leading to overdiagnosis of Dravet syndrome beyond SCN1A. Dravet syndrome is in turn a severe SCN1A phenotype within a continuum of SCN1A-related clinical phenomenology.
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Affiliation(s)
- Davide Mei
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Meyer Children's Hospital-University of Florence, Florence, Italy
| | - Valentina Cetica
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Meyer Children's Hospital-University of Florence, Florence, Italy
| | - Carla Marini
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Meyer Children's Hospital-University of Florence, Florence, Italy
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Meyer Children's Hospital-University of Florence, Florence, Italy.,IRCCS Stella Maris Foundation, Pisa, Italy
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Till Á, Zima J, Fekete A, Bene J, Czakó M, Szabó A, Melegh B, Hadzsiev K. Mutation spectrum of the SCN1A gene in a Hungarian population with epilepsy. Seizure 2019; 74:8-13. [PMID: 31765958 DOI: 10.1016/j.seizure.2019.10.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/30/2019] [Accepted: 10/29/2019] [Indexed: 01/05/2023] Open
Abstract
PURPOSE The vast majority of mutations responsible for epilepsy syndromes such as genetic epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (DS) occur in the gene encoding the type 1 alpha subunit of neuronal voltage-gated sodium channel (SCN1A). METHODS 63 individuals presenting with either DS or GEFS + syndrome phenotype were screened for SCN1A gene mutation using Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). RESULTS Our research study identified 15 novel pathogen mutations in the SCN1A gene of which 12 appeared to be missense mutations with addition of two frameshift-deletions and one in-frame deletion. The distribution of clinical phenotypes in patients carrying SCN1A mutations was as follows: twelve patients had classical DS, three patients had GEFS + syndrome and two relatives of DS patients were suffering from febrile seizures. CONCLUSIONS Our study highlights the phenotypic and genotypic heterogeneities of DS and GEFS + with the important aim of gaining a deeper understanding of SCN1A-related disorders. This study also represents the first genetic analysis of the SCN1A gene in a Hungarian cohort with the DS and GEFS + syndrome phenotype.
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Affiliation(s)
- Ágnes Till
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary
| | - Judith Zima
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary
| | - Anett Fekete
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary
| | - Judit Bene
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary; Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Márta Czakó
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary; Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - András Szabó
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary; Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Béla Melegh
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary; Szentágothai Research Center, University of Pécs, Pécs, Hungary.
| | - Kinga Hadzsiev
- Department of Medical Genetics, Medical School, Clinical Center, University of Pécs, Pécs, Hungary; Szentágothai Research Center, University of Pécs, Pécs, Hungary
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Liu A, Yang X, Yang X, Wu Q, Zhang J, Sun D, Yang Z, Jiang Y, Wu X, Wei L, Zhang Y. Mosaicism and incomplete penetrance of PCDH19 mutations. J Med Genet 2018; 56:81-88. [PMID: 30287595 PMCID: PMC6581080 DOI: 10.1136/jmedgenet-2017-105235] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 08/25/2018] [Accepted: 08/30/2018] [Indexed: 02/02/2023]
Abstract
BACKGROUND Mutations in the PCDH19 gene have mainly been reported in female patients with epilepsy. To date, PCDH19 mutations have been reported in hundreds of females and only in 10 mosaic male epileptic patients with mosaicism. OBJECTIVE We aimed to investigate the occurrence of mosaic PCDH19 mutations in 42 families comprising at least one patient with PCDH19-related epilepsy. METHODS Two male patients with mosaic PCDH19 variants were identified using targeted next-generation sequencing. Forty female patients with PCDH19 variants were identified by Sanger sequencing and Multiple Ligation Probe Amplification (MLPA). Microdroplet digital PCR was used to quantify the mutant allelic fractions (MAFs) in 20 families with PCDH19 variants. RESULTS Five mosaic individuals, four males and one female, were identified in total. Mosaic variant was confirmed in multiple somatic tissues from one male patient and in blood from the other male patient. Among 22 female patients harbouring a newly occurred PCDH19 variant identified by Sanger sequencing and MLPA, Sanger sequencing revealed two mosaic fathers (9%, 2/22), one with two affected daughters and the other with an affected child. Two asymptomatic mosaic fathers were confirmed as gonosomal mosaicism, with MAFs ranging from 4.16% to 37.38% and from 1.27% to 19.13%, respectively. In 11 families with apparent de novo variants, 1 female patient was identified as a mosaic with a blood MAF of 26.72%. CONCLUSION Our study provides new insights into phenotype-genotype correlations in PCDH19 related epilepsy and the finding of high-frequency mosaicism has important implications for genetic counselling.
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Affiliation(s)
- Aijie Liu
- Department of Pediatrics, Peking University First Hospital, Beijing, China.,Department of Pediatric Neurology, Capital Institute of Pediatrics, Beijing, China
| | - Xiaoxu Yang
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Xiaoling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Qixi Wu
- School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Jing Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Dan Sun
- Department of Neurology, Wuhan Children's Hospital, Wuhan, China
| | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Yuwu Jiang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiru Wu
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Liping Wei
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Yuehua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
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Myers KA, Johnstone DL, Dyment DA. Epilepsy genetics: Current knowledge, applications, and future directions. Clin Genet 2018; 95:95-111. [PMID: 29992546 DOI: 10.1111/cge.13414] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 07/03/2018] [Accepted: 07/06/2018] [Indexed: 12/12/2022]
Abstract
The rapid pace of disease gene discovery has resulted in tremendous advances in the field of epilepsy genetics. Clinical testing with comprehensive gene panels, exomes, and genomes are now available and have led to higher diagnostic rates and insights into the underlying disease processes. As such, the contribution to the care of patients by medical geneticists, neurogeneticists and genetic counselors are significant; the dysmorphic examination, the necessary pre- and post-test counseling, the selection of the appropriate next-generation sequencing-based test(s), and the interpretation of sequencing results require a care provider to have a comprehensive working knowledge of the strengths and limitations of the available testing technologies. As the underlying mechanisms of the encephalopathies and epilepsies are better understood, there may be opportunities for the development of novel therapies based on an individual's own specific genotype. Drug screening with in vitro and in vivo models of epilepsy can potentially facilitate new treatment strategies. The future of epilepsy genetics will also probably include other-omic approaches such as transcriptomes, metabolomes, and the expanded use of whole genome sequencing to further improve our understanding of epilepsy and provide better care for those with the disease.
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Affiliation(s)
- K A Myers
- Department of Pediatrics, University of McGill, Montreal, Canada.,Research Institute of the McGill University Health Centre, Montreal, Canada
| | - D L Johnstone
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
| | - D A Dyment
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada.,Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Canada
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12
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Ye AY, Dou Y, Yang X, Wang S, Huang AY, Wei L. A model for postzygotic mosaicisms quantifies the allele fraction drift, mutation rate, and contribution to de novo mutations. Genome Res 2018; 28:943-951. [PMID: 29875290 PMCID: PMC6028137 DOI: 10.1101/gr.230003.117] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 05/02/2018] [Indexed: 12/14/2022]
Abstract
The allele fraction (AF) distribution, occurrence rate, and evolutionary contribution of postzygotic single-nucleotide mosaicisms (pSNMs) remain largely unknown. In this study, we developed a mathematical model to describe the accumulation and AF drift of pSNMs during the development of multicellular organisms. By applying the model, we quantitatively analyzed two large-scale data sets of pSNMs identified from human genomes. We found that the postzygotic mutation rate per cell division during early embryogenesis, especially during the first cell division, was higher than the average mutation rate in either male or female gametes. We estimated that the stochastic cell death rate per cell cleavage during human embryogenesis was ∼5%, and parental pSNMs occurring during the first three cell divisions contributed to ∼10% of the de novo mutations observed in children. We further demonstrated that the genomic profiles of pSNMs could be used to measure the divergence distance between tissues. Our results highlight the importance of pSNMs in estimating recurrence risk and clarified the quantitative relationship between postzygotic and de novo mutations.
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Affiliation(s)
- Adam Yongxin Ye
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, People's Republic of China.,Peking-Tsinghua Center for Life Sciences, Beijing 100871, People's Republic of China.,Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, People's Republic of China
| | - Yanmei Dou
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, People's Republic of China.,National Institute of Biological Sciences, Beijing 102206, People's Republic of China
| | - Xiaoxu Yang
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Sheng Wang
- National Institute of Biological Sciences, Beijing 102206, People's Republic of China.,College of Biological Sciences, China Agricultural University, Beijing 100094, People's Republic of China
| | - August Yue Huang
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Liping Wei
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, People's Republic of China
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13
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de Lange IM, Koudijs MJ, van 't Slot R, Gunning B, Sonsma ACM, van Gemert LJJM, Mulder F, Carbo EC, van Kempen MJA, Verbeek NE, Nijman IJ, Ernst RF, Savelberg SMC, Knoers NVAM, Brilstra EH, Koeleman BPC. Mosaicism of de novo pathogenic SCN1A
variants in epilepsy is a frequent phenomenon that correlates with variable phenotypes. Epilepsia 2018; 59:690-703. [DOI: 10.1111/epi.14021] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Iris M. de Lange
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Marco J. Koudijs
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Ruben van 't Slot
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | | | - Anja C. M. Sonsma
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | | | - Flip Mulder
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Ellen C. Carbo
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Marjan J. A. van Kempen
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Nienke E. Verbeek
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Isaac J. Nijman
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Robert F. Ernst
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Sanne M. C. Savelberg
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Nine V. A. M. Knoers
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Eva H. Brilstra
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
| | - Bobby P. C. Koeleman
- Department of Genetics; Center for Molecular Medicine; University Medical Center Utrecht; Utrecht the Netherlands
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14
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Mahdieh N, Mikaeeli S, Badv RS, Shirazi AG, Maleki M, Rabbani B. Pathogenic significance of SCN1A splicing variants causing Dravet syndrome: Improving diagnosis with targeted sequencing for variants by in silico analysis. Clin Neurol Neurosurg 2018; 166:80-90. [PMID: 29408779 DOI: 10.1016/j.clineuro.2018.01.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 01/21/2018] [Accepted: 01/27/2018] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Genetic heterogeneity of epileptic encephalopathy (IEE) mandates the use of gene-panels for diagnosis. PATIENTS AND METHODS A 36-gene-panel next-generation sequencing was applied for IEE in two Iranian families. A literature search was performed using keywords to identify reported splicing mutations in SCN1A and perform genotype-phenotype correlation. RESULTS An update of splicing mutations revealed 147 variants with 65.75% of them de novo mutations. Most of the familial variants were of parental origin. The structure of the protein was often affected in the linker and transmembrane segments. 92% of intronic variants were pathogenic. A de novo heterozygous mutation was found in the first patient, but not in her sibling and parents. In the second family, a novel de novo heterozygous mutation was found at position c.1210insT leading to a truncated protein. CONCLUSION Gene-panel sequencing is helpful for reducing the time and cost, guiding early treatment, and estimating the recurrence risks. The importance of characterization of intronic variants was noticed; though bioinformatics analysis of novel intronic variants should be of concern for rapid reporting the pathogenic effect of variants.
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Affiliation(s)
- Nejat Mahdieh
- Genetic Research Laboratory, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
| | - Sepideh Mikaeeli
- Genetic Research Laboratory, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Reza Shervin Badv
- Children's Hospital Center, Pediatric Center of Excellence, Tehran University of Medical Center, Tehran, Iran
| | - Azadeh Gharehzadeh Shirazi
- Children's Hospital Center, Pediatric Center of Excellence, Tehran University of Medical Center, Tehran, Iran
| | - Majid Maleki
- Genetic Research Laboratory, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Bahareh Rabbani
- Genetic Research Laboratory, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
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15
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Genomic mosaicism in paternal sperm and multiple parental tissues in a Dravet syndrome cohort. Sci Rep 2017; 7:15677. [PMID: 29142202 PMCID: PMC5688122 DOI: 10.1038/s41598-017-15814-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 11/02/2017] [Indexed: 12/21/2022] Open
Abstract
Genomic mosaicism in parental gametes and peripheral tissues is an important consideration for genetic counseling. We studied a Chinese cohort affected by a severe epileptic disorder, Dravet syndrome (DS). There were 56 fathers who donated semen and 15 parents who donated multiple peripheral tissue samples. We used an ultra-sensitive quantification method, micro-droplet digital PCR (mDDPCR), to detect parental mosaicism of the proband’s pathogenic mutation in SCN1A, the causal gene of DS in 112 families. Ten of the 56 paternal sperm samples were found to exhibit mosaicism of the proband’s mutations, with mutant allelic fractions (MAFs) ranging from 0.03% to 39.04%. MAFs in the mosaic fathers’ sperm were significantly higher than those in their blood (p = 0.00098), even after conditional probability correction (p’ = 0.033). In three mosaic fathers, ultra-low fractions of mosaicism (MAF < 1%) were detected in the sperm samples. In 44 of 45 cases, mosaicism was also observed in other parental peripheral tissues. Hierarchical clustering showed that MAFs measured in the paternal sperm, hair follicles and urine samples were clustered closest together. Milder epileptic phenotypes were more likely to be observed in mosaic parents (p = 3.006e-06). Our study provides new insights for genetic counseling.
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16
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High frequency of mosaic pathogenic variants in genes causing epilepsy-related neurodevelopmental disorders. Genet Med 2017; 20:403-410. [PMID: 28837158 PMCID: PMC5895461 DOI: 10.1038/gim.2017.114] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/09/2017] [Indexed: 12/18/2022] Open
Abstract
Purpose Mosaicism probably represents an underreported cause of genetic disorders due to detection challenges during routine molecular diagnostics. The purpose of this study was to evaluate the frequency of mosaicism detected by next-generation sequencing in genes associated with epilepsy-related neurodevelopmental disorders. Methods We conducted a retrospective analysis of 893 probands with epilepsy who had a multigene epilepsy panel or whole-exome sequencing performed in a clinical diagnostic laboratory and were positive for a pathogenic or likely pathogenic variant in one of nine genes (CDKL5, GABRA1, GABRG2, GRIN2B, KCNQ2, MECP2, PCDH19, SCN1A, or SCN2A). Parental results were available for 395 of these probands. Results Mosaicism was most common in the CDKL5, PCDH19, SCN2A, and SCN1A genes. Mosaicism was observed in GABRA1, GABRG2, and GRIN2B, which previously have not been reported to have mosaicism, and also in KCNQ2 and MECP2. Parental mosaicism was observed for pathogenic variants in multiple genes including KCNQ2, MECP2, SCN1A, and SCN2A. Conclusion Mosaic pathogenic variants were identified frequently in nine genes associated with various neurological conditions. Given the potential clinical ramifications, our findings suggest that next-generation sequencing diagnostic methods may be utilized when testing these genes in a diagnostic laboratory.
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17
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FOXG1 syndrome: genotype-phenotype association in 83 patients with FOXG1 variants. Genet Med 2017; 20:98-108. [PMID: 28661489 DOI: 10.1038/gim.2017.75] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 03/16/2017] [Indexed: 12/31/2022] Open
Abstract
PurposeThe study aimed at widening the clinical and genetic spectrum and assessing genotype-phenotype associations in FOXG1 syndrome due to FOXG1 variants.MethodsWe compiled 30 new and 53 reported patients with a heterozygous pathogenic or likely pathogenic variant in FOXG1. We grouped patients according to type and location of the variant. Statistical analysis of molecular and clinical data was performed using Fisher's exact test and a nonparametric multivariate test.ResultsAmong the 30 new patients, we identified 19 novel FOXG1 variants. Among the total group of 83 patients, there were 54 variants: 20 frameshift (37%), 17 missense (31%), 15 nonsense (28%), and 2 in-frame variants (4%). Frameshift and nonsense variants are distributed over all FOXG1 protein domains; missense variants cluster within the conserved forkhead domain. We found a higher phenotypic variability than previously described. Genotype-phenotype association revealed significant differences in psychomotor development and neurological features between FOXG1 genotype groups. More severe phenotypes were associated with truncating FOXG1 variants in the N-terminal domain and the forkhead domain (except conserved site 1) and milder phenotypes with missense variants in the forkhead conserved site 1.ConclusionsThese data may serve for improved interpretation of new FOXG1 sequence variants and well-founded genetic counseling.
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18
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Mei D, Parrini E, Marini C, Guerrini R. The Impact of Next-Generation Sequencing on the Diagnosis and Treatment of Epilepsy in Paediatric Patients. Mol Diagn Ther 2017; 21:357-373. [DOI: 10.1007/s40291-017-0257-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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19
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Kozhanova TV, Zhylina SS, Aivazian SO, Ananyeva TV, Abramov AA, Belenikin MS, Meshcheryakova TI, Mutovin GR, Zavadenko NN. [The diagnosis of idiopathic epilepsy in children based on the algorithm of molecular-genetic studies]. Zh Nevrol Psikhiatr Im S S Korsakova 2016; 116:49-56. [PMID: 28005047 DOI: 10.17116/jnevro20161169249-56] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AIM To study mutations and polymorphisms in the sodium channels genes, determining the development of idiopathic epilepsy (IE). MATERIAL AND METHODS The study of SCN1A gene by direct Sanger sequencing in 53 patients and targeted resequencing of the regions of 34 genes in 40 patients with different clinical forms of IE was performed. RESULTS Seven mutations (c.3022G>T, c.3637C>T, c.1144G>T, c.80G>C, c.1603C>T, c.2427G>A and c.1131A>C) were detected among 53 patients by direct Sanger sequencing of SCN1A gene. The mutations of SCN1A gene (2 - nonsense mutation, 5 - missense mutation) were identified in 7/40 (17.5%) patients with epilepsy using high-performance sequencing, Mutations in sodium channel genes encoding other subunits: SCN1B, SCN2A, SCN9A were identified in 6 patients. CONCLUSION As epileptic encephalopathy is polygenic, it is important to conduct genetic testing of more genes (primarily sodium channel genes - SCN1B, SCN2A, SCN9A etc.) using special gene panels to find the molecular defect in DNA.
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Affiliation(s)
- T V Kozhanova
- Scientific and Practical Center of Children Medical Care, Moscow, Russia; Pirogov Russian National Research Medical University, Moscow, Russia
| | - S S Zhylina
- Scientific and Practical Center of Children Medical Care, Moscow, Russia; Pirogov Russian National Research Medical University, Moscow, Russia
| | - S O Aivazian
- Scientific and Practical Center of Children Medical Care, Moscow, Russia
| | - T V Ananyeva
- Scientific and Practical Center of Children Medical Care, Moscow, Russia
| | - A A Abramov
- Scientific and Practical Center of Children Medical Care, Moscow, Russia
| | - M S Belenikin
- Scientific and Practical Center of Children Medical Care, Moscow, Russia
| | - T I Meshcheryakova
- Scientific and Practical Center of Children Medical Care, Moscow, Russia
| | - G R Mutovin
- Scientific and Practical Center of Children Medical Care, Moscow, Russia; Pirogov Russian National Research Medical University, Moscow, Russia
| | - N N Zavadenko
- Pirogov Russian National Research Medical University, Moscow, Russia
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20
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McTague A, Howell KB, Cross JH, Kurian MA, Scheffer IE. The genetic landscape of the epileptic encephalopathies of infancy and childhood. Lancet Neurol 2016; 15:304-16. [DOI: 10.1016/s1474-4422(15)00250-1] [Citation(s) in RCA: 296] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 09/16/2015] [Accepted: 09/17/2015] [Indexed: 10/22/2022]
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21
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Xu X, Yang X, Wu Q, Liu A, Yang X, Ye AY, Huang AY, Li J, Wang M, Yu Z, Wang S, Zhang Z, Wu X, Wei L, Zhang Y. Amplicon Resequencing Identified Parental Mosaicism for Approximately 10% of "de novo" SCN1A Mutations in Children with Dravet Syndrome. Hum Mutat 2015; 36:861-72. [PMID: 26096185 PMCID: PMC5034833 DOI: 10.1002/humu.22819] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 05/28/2015] [Indexed: 12/13/2022]
Abstract
The majority of children with Dravet syndrome (DS) are caused by de novo SCN1A mutations. To investigate the origin of the mutations, we developed and applied a new method that combined deep amplicon resequencing with a Bayesian model to detect and quantify allelic fractions with improved sensitivity. Of 174 SCN1A mutations in DS probands which were considered "de novo" by Sanger sequencing, we identified 15 cases (8.6%) of parental mosaicism. We identified another five cases of parental mosaicism that were also detectable by Sanger sequencing. Fraction of mutant alleles in the 20 cases of parental mosaicism ranged from 1.1% to 32.6%. Thirteen (65% of 20) mutations originated paternally and seven (35% of 20) maternally. Twelve (60% of 20) mosaic parents did not have any epileptic symptoms. Their mutant allelic fractions were significantly lower than those in mosaic parents with epileptic symptoms (P = 0.016). We identified mosaicism with varied allelic fractions in blood, saliva, urine, hair follicle, oral epithelium, and semen, demonstrating that postzygotic mutations could affect multiple somatic cells as well as germ cells. Our results suggest that more sensitive tools for detecting low-level mosaicism in parents of families with seemingly "de novo" mutations will allow for better informed genetic counseling.
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Affiliation(s)
- Xiaojing Xu
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Xiaoxu Yang
- Center for BioinformaticsState Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking UniversityBeijingChina
| | - Qixi Wu
- National Institute of Biological SciencesBeijingChina
| | - Aijie Liu
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Xiaoling Yang
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Adam Yongxin Ye
- Center for BioinformaticsState Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking UniversityBeijingChina
- Peking‐Tsinghua Center for Life SciencesBeijingChina
- Academy for Advanced Interdisciplinary StudiesPeking UniversityBeijingChina
| | | | - Jiarui Li
- Center for BioinformaticsState Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking UniversityBeijingChina
| | - Meng Wang
- Center for BioinformaticsState Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking UniversityBeijingChina
| | - Zhe Yu
- National Institute of Biological SciencesBeijingChina
| | - Sheng Wang
- National Institute of Biological SciencesBeijingChina
- College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Zhichao Zhang
- Andrology CenterPeking University First HospitalBeijingChina
| | - Xiru Wu
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Liping Wei
- Center for BioinformaticsState Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking UniversityBeijingChina
- National Institute of Biological SciencesBeijingChina
| | - Yuehua Zhang
- Department of PediatricsPeking University First HospitalBeijingChina
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22
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Meng H, Xu HQ, Yu L, Lin GW, He N, Su T, Shi YW, Li B, Wang J, Liu XR, Tang B, Long YS, Yi YH, Liao WP. TheSCN1AMutation Database: Updating Information and Analysis of the Relationships among Genotype, Functional Alteration, and Phenotype. Hum Mutat 2015; 36:573-80. [PMID: 25754450 DOI: 10.1002/humu.22782] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/25/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Heng Meng
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
- Department of Neurology; The First Affiliated Hospital of Jinan University; Guangzhou China
| | - Hai-Qing Xu
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Lu Yu
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Guo-Wang Lin
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Na He
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Tao Su
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Yi-Wu Shi
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Bin Li
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Jie Wang
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Xiao-Rong Liu
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Bin Tang
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Yue-Sheng Long
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Yong-Hong Yi
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
| | - Wei-Ping Liao
- Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China; Guangzhou China
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Ben Mahmoud A, Ben Mansour R, Driss F, Baklouti-Gargouri S, Siala O, Mkaouar-Rebai E, Fakhfakh F. Evaluation of the effect of c.2946+1G>T mutation on splicing in the SCN1A gene. Comput Biol Chem 2015; 54:44-8. [DOI: 10.1016/j.compbiolchem.2015.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 11/05/2014] [Accepted: 01/03/2015] [Indexed: 10/24/2022]
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25
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Guerrini R, Marini C, Mantegazza M. Genetic epilepsy syndromes without structural brain abnormalities: clinical features and experimental models. Neurotherapeutics 2014; 11:269-85. [PMID: 24664660 PMCID: PMC3996114 DOI: 10.1007/s13311-014-0267-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Research in genetics of epilepsy represents an area of great interest both for clinical purposes and for understanding the basic mechanisms of epilepsy. Most mutations in epilepsies without structural brain abnormalities have been identified in ion channel genes, but an increasing number of genes involved in a diversity of functional and developmental processes are being recognized through whole exome or genome sequencing. Targeted molecular diagnosis is now available for different forms of epilepsy. The identification of epileptogenic mutations in patients before epilepsy onset and the possibility of developing therapeutic strategies tested in experimental models may facilitate experimental approaches that prevent epilepsy or decrease its severity. Functional analysis is essential for better understanding pathogenic mechanisms and gene interactions. In vitro experimental systems are either cells that usually do not express the protein of interest or neurons in primary cultures. In vivo/ex vivo systems are organisms or preparations obtained from them (e.g., brain slices), which should better model the complexity of brain circuits and actual pathophysiological conditions. Neurons differentiated from induced pluripotent stem cells generated from the skin fibroblasts of patients have recently allowed the study of mutations in human neurons having the genetic background of a given patient. However, there is remarkable complexity underlying epileptogenesis in the clinical dimension, as reflected by the fact that experimental models have not provided yet results having clinical translation and that, with a few exceptions concerning rare conditions, no new curative treatment has emerged from any genetic finding in epilepsy.
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Affiliation(s)
- Renzo Guerrini
- Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Viale Pieraccini 24, 50139, Florence, Italy,
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26
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Le Gal F, Lebon S, Ramelli GP, Datta AN, Mercati D, Maier O, Combescure C, Rodriguez MI, Seeck M, Roulet E, Korff CM. When is a child with status epilepticus likely to have Dravet syndrome? Epilepsy Res 2014; 108:740-7. [PMID: 24679980 DOI: 10.1016/j.eplepsyres.2014.02.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 02/07/2014] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
Abstract
PURPOSE To identify clinical risk factors for Dravet syndrome (DS) in a population of children with status epilepticus (SE). MATERIAL AND METHODS Children aged between 1 month and 16 years with at least one episode of SE were referred from 6 pediatric neurology centers in Switzerland. SE was defined as a clinical seizure lasting for more than 30min without recovery of normal consciousness. The diagnosis of DS was considered likely in previously healthy patients with seizures of multiple types starting before 1 year and developmental delay on follow-up. The presence of a SCN1A mutation was considered confirmatory for the diagnosis. Data such as gender, age at SE, SE clinical presentation and recurrence, additional seizure types and epilepsy diagnosis were collected. SCN1A analyses were performed in all patients, initially with High Resolution Melting Curve Analysis (HRMCA) and then by direct sequencing on selected samples with an abnormal HRMCA. Clinical and genetic findings were compared between children with DS and those with another diagnosis, and statistical methods were applied for significance analysis. RESULTS 71 children with SE were included. Ten children had DS, and 61 had another diagnosis. SCN1A mutations were found in 12 of the 71 patients (16.9%; ten with DS, and two with seizures in a Generalized Epilepsy with Febrile Seizures+(GEFS+) context). The median age at first SE was 8 months in patients with DS, and 41 months in those with another epilepsy syndrome (p<0.001). Nine of the 10 DS patients had their initial SE before 18 months. Among the 26 patients aged 18 months or less at initial SE, the risk of DS was significantly increased for patients with two or more episodes (56.3%), as compared with those who had only one episode (0.0%) (p=0.005). CONCLUSION In a population of children with SE, patients most likely to have DS are those who present their initial SE episode before 18 months, and who present with recurrent SE episodes.
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Affiliation(s)
- François Le Gal
- Psychiatric Genetic Unit, Genetic Medicine Service, University Hospitals, Geneva, Switzerland; Molecular Diagnostic Laboratory, Genetic Medicine Service, University Hospitals, Geneva, Switzerland
| | | | | | | | | | - Oliver Maier
- Pediatric Neurology, Children's Hospital, St. Gallen, Switzerland
| | - Christophe Combescure
- Clinical Research Center, Division of Clinical Epidemiology, Department of Health and Community Medicine, University of Geneva and University Hospitals, Geneva, Switzerland
| | - Maria Isabel Rodriguez
- Clinical Research Platform, Child and Adolescent Department, University Hospitals, Geneva, Switzerland
| | - Margitta Seeck
- Clinical Neurosciences Department, University Hospitals, Geneva, Switzerland
| | | | - Christian M Korff
- Pediatric Neurology, Child and Adolescent Department, University Hospitals, Geneva, Switzerland.
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Goldberg-Stern H, Aharoni S, Afawi Z, Bennett O, Appenzeller S, Pendziwiat M, Kuhlenbäumer G, Basel-Vanagaite L, Shuper A, Korczyn AD, Helbig I. Broad phenotypic heterogeneity due to a novel SCN1A mutation in a family with genetic epilepsy with febrile seizures plus. J Child Neurol 2014; 29:221-6. [PMID: 24257433 DOI: 10.1177/0883073813509016] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Genetic (generalized) epilepsy with febrile seizures plus is a familial epilepsy syndrome with marked phenotypic heterogeneity ranging from simple febrile seizure to severe phenotypes. Here we report on a large Israeli family with genetic (generalized) epilepsy with febrile seizures plus and 14 affected individuals. A novel SCN1A missense mutation in exon 21 (p.K1372E) was identified in all affected individuals and 3 unaffected carriers. The proband had Dravet syndrome, whereas febrile seizure plus phenotypes were present in all other affected family members. Simple febrile seizures were not observed. Phenotypes were found at both extremes of the genetic (generalized) epilepsy with febrile seizures plus spectrum and distribution of phenotypes suggested modifying familial, possibly genetic factors. We suggest that families with extreme phenotype distributions can represent prime candidates for the identification of genetic or environmental modifiers.
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Affiliation(s)
- Hadassa Goldberg-Stern
- 1Department of Pediatric and Adolescent Neurology, Epilepsy Center, Schneider Children's Medical Center of Israel, Petach Tikva, Israel
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28
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Abstract
Epilepsy affects almost 1% of the population, and yet the pathophysiology of this disorder is unknown in the majority of the cases. Recently, a number of mutations in different genes were identified, mostly in cases of familial epilepsy with a Mendelian mode of inheritance. The majority of these genes code for voltage- or ligand-gated ion channels. Interestingly, not only generalized epilepsies, but also focal epilepsies were shown to be caused by mutated genes, which in some cases are expressed ubiquitously in the brain. This review will focus on the monogenic familial epilepsies and the clinical and molecular aspects of these diseases.
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Affiliation(s)
- Danielle M Andrade
- University of Toronto, Division of Neurology, Krembil Neuroscience Centre, Toronto Western Hospital, Toronto, Canada.
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29
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Abstract
Human genetic mosaicism is the presence of two or more cellular populations with distinct genotypes in an individual who developed from a single fertilized ovum. While initially observed across a spectrum of rare genetic disorders, detailed assessment of data from genome-wide association studies now reveal that detectable clonal mosaicism involving large structural alterations (>2 Mb) can also be seen in populations of apparently healthy individuals. The first generation of descriptive studies has generated new interest in understanding the molecular basis of the affected genomic regions, percent of the cellular subpopulation involved, and developmental timing of the underlying mutational event, which could reveal new insights into the initiation, clonal expansion, and phenotypic manifestations of mosaic events. Early evidence indicates detectable clonal mosaicism increases in frequency with age and could preferentially occur in males. The observed pattern of recurrent events affecting specific chromosomal regions indicates some regions are more susceptible to these events, which could reflect inter-individual differences in genomic stability. Moreover, it is also plausible that the presence of large structural events could be associated with cancer risk. The characterization of detectable genetic mosaicism reveals that there could be important dynamic changes in the human genome associated with the aging process, which could be associated with risk for common disorders, such as cancer, cardiovascular disease, diabetes, and neurological disorders.
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Affiliation(s)
- Mitchell J. Machiela
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA. 20892-4605
| | - Stephen J. Chanock
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA. 20892-4605
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Hirose S, Scheffer IE, Marini C, De Jonghe P, Andermann E, Goldman AM, Kauffman M, Tan NCK, Lowenstein DH, Sisodiya SM, Ottman R, Berkovic SF. SCN1Atesting for epilepsy: Application in clinical practice. Epilepsia 2013; 54:946-52. [DOI: 10.1111/epi.12168] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2013] [Indexed: 01/02/2023]
Affiliation(s)
- Shinichi Hirose
- Department of Pediatrics and Research Institute for the Molecular Pathomechanisms of Epilepsy; Fukuoka University; Fukuoka; Japan
| | - Ingrid E. Scheffer
- Florey Institute; Departments of Medicine and Paediatrics; Austin Health and Royal Children's Hospital; University of Melbourne; Melbourne; Victoria; Australia
| | - Carla Marini
- Epilepsy, Neurophysiology and Neurogenetics Unit; Division of Child Neurology and Psychiatry; University of Pisa and Research Institute Stella Maris Foundation; Pisa; Italy
| | | | - Eva Andermann
- Neurogenetics Unit; Montreal Neurological Hospital & Institute; Montreal; Quebec; Canada
| | - Alica M. Goldman
- Department of Neurology; Baylor College of Medicine; Houston; Texas; U.S.A
| | - Marcelo Kauffman
- Neurogenetics Clinic Hospital JM Ramos Mejia; University of Buenos Aires-CONICET; Buenos Aires; Argentina
| | - Nigel C. K. Tan
- Department of Neurology; National Neuroscience Institute; Singapore; Singapore
| | - Daniel H. Lowenstein
- Department of Neurology; University of California; San Francisco; California; U.S.A
| | | | - Ruth Ottman
- Sergievsky Center and Departments of Epidemiology and Neurology; Columbia University; New York; New York; U.S.A
| | - Samuel F. Berkovic
- Epilepsy Research Centre; University of Melbourne, Austin Health; Melbourne; Victoria; Australia
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Abstract
One of the most exciting areas in epilepsy has been the explosion in our understanding of the genetics of the epilepsies over the last decade. Built on a long history of careful clinical genetic studies of the epilepsies, the relatively recent discovery of epilepsy genes has enabled insights into pathways causing seizure disorders. A variety of mutational mechanisms can cause epilepsy resulting from different, and sometimes surprising, molecular processes such as copy number variation within the genome. The majority of known epilepsy genes encode ion channel subunits leading many of the genetic epilepsies to be regarded as channelopathies. Understanding how dysfunction of a mutant protein leads to hyperexcitability is key to understanding the pathophysiology of this group of serious and common childhood disorders. The architecture of the common genetic epilepsies following complex inheritance, where multiple genes are involved, is also beginning to be unraveled. The clinical approach to understanding the genetics of the epilepsies has matured and requires a detailed family history of seizures together with delineation of the child's epilepsy syndrome. Recognition of specific genetic epilepsy syndromes enables optimal treatment and prognostic and genetic counseling.
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Affiliation(s)
- Rima Nabbout
- Department of Pediatric Neurology, Hôpital Necker-Enfants Malades; Centre de référence épilepsies rares; INSERM U663, Paris, France.
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32
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Abstract
Dravet syndrome is a severe infantile-onset epilepsy syndrome with a distinctive but complex electroclinical presentation. A healthy, developmentally normal infant presents at around 6 months of age with convulsive status epilepticus, which may be hemiclonic or generalized; seizures may be triggered by fever, illness or vaccination. The infant typically has further episodes of status epilepticus every month or two, often triggered by fever. Other seizure types including focal dyscognitive seizures, absence and myoclonic seizures develop between 1 and 4 years. Atonic drop attacks and episodes of non-convulsive status may occur. Early development is normal but slows in the second year. Developmental regression may occur, particularly with status epilepticus. EEG studies are initially normal, but after 2 years they show generalized spike-wave and polyspike-wave activity with multifocal discharges. Photosensitivity may be seen. Imaging is normal or shows non-specific findings such as atrophy. Dravet syndrome is associated with mutations of the gene encoding the alpha-1 subunit of the sodium channel, SCN1A, in >70% of patients. These include sequencing mutations and copy number variant anomalies; 90% of mutations arise de novo. PCDH19 mutational analysis is a second-tier test for girls with a Dravet-like picture who do not have SCN1A mutations. Outcome is poor, with intellectual disability in most patients and ongoing seizures. Intellectual impairment varies from severe in 50% patients, to moderate and mild intellectual disability each accounting for 25% cases. Rare patients have normal intellect. The long-term course involves ongoing, brief nocturnal convulsions and a characteristic deterioration in gait.
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Affiliation(s)
- Ingrid E Scheffer
- Department of Medicine and Paediatrics, Florey Neuroscience Institutes, University of Melbourne, Austin Health and Royal Children's Hospital, Melbourne, Australia.
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33
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Abstract
Dravet syndrome (DS) is a severe form of infantile onset epilepsy characterized by multiple seizure types, prolonged convulsive seizures and frequent episodes of status epilepticus. Seizures precipitated by fever are a main characteristic. Affected children exhibit normal early development. Cognitive impairment, behavioral disturbances with hyperactivity and sometimes autistic traits occur after seizure onset. Seizures persist into adulthood but become less frequent. In about 85% of patients, a mutation of the SCN1A gene is present. DS fully illustrates the concept of epileptic encephalopathy. However, it is difficult to determine the causative role of the underlying sodium channel dysfunction and that of the consequent seizures in influencing cognitive outcome. An overwhelmingly high number of SCN1A mutations have been associated with DS. Intragenic or whole gene deletions, duplications and amplifications are additional rare molecular mechanisms. Most mutations are de novo, but familial mutations also occur. Somatic mosaic mutations should be considered when estimating the recurrence. MRI imaging is usually normal, and no neuropathologic signature of the condition seems to exist. In heterozygous Scn1a+/- mice, GABAergic interneurons exhibit substantially reduced sodium current density with reduced ability for sustained action potential firing. GABAergic output is reduced and excitability of downstream synaptic targets increased. Stiripentol was effective in combination with valproate and clobazam in two pivotal phase III trials. Phenytoin, carbamazepine, and lamotrigine can worsen seizures and should be avoided. Prospective studies will clarify to what extent earlier diagnosis and efforts at seizure control with the most appropriate drug combinations will reduce clinical deterioration.
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Affiliation(s)
- Renzo Guerrini
- Pediatric Neurology and Neurogenetics Unit and Laboratories, Children's Hospital A Meyer, University of Florence, Firenze, Italy.
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34
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Kwong AKY, Fung CW, Chan SY, Wong VCN. Identification of SCN1A and PCDH19 mutations in Chinese children with Dravet syndrome. PLoS One 2012; 7:e41802. [PMID: 22848613 PMCID: PMC3405017 DOI: 10.1371/journal.pone.0041802] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 06/25/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Dravet syndrome is a severe form of epilepsy. Majority of patients have a mutation in SCN1A gene, which encodes a voltage-gated sodium channel. A recent study has demonstrated that 16% of SCN1A-negative patients have a mutation in PCDH19, the gene encoding protocadherin-19. Mutations in other genes account for only a very small proportion of families. TSPYL4 is a novel candidate gene within the locus 6q16.3-q22.31 identified by linkage study. OBJECTIVE The present study examined the mutations in epileptic Chinese children with emphasis on Dravet syndrome. METHODS A hundred children with severe epilepsy were divided into Dravet syndrome and non-Dravet syndrome groups and screened for SCN1A mutations by direct sequencing. SCN1A-negative Dravet syndrome patients and patients with phenotypes resembling Dravet syndrome were checked for PCDH19 and TSPYL4 mutations. RESULTS Eighteen patients (9 males, 9 females) were diagnosed to have Dravet syndrome. Among them, 83% (15/18) had SCN1A mutations including truncating (7), splice site (2) and missense mutations (6). The truncating/splice site mutations were associated with moderate to severe degree of intellectual disability (p<0.05). During the progression of disease, 73% (11/15) had features fitting into the diagnostic criteria of autism spectrum disorder and 53% (8/15) had history of vaccination-induced seizures. A novel PCDH19 p.D377N mutation was identified in one SCN1A-negative female patient with Dravet syndrome and a known PCDH19 p.N340S mutation in a female non-Dravet syndrome patient. The former also inherited a TSPYL4 p.G60R variant. CONCLUSION A high percentage of SCN1A mutations was identified in our Chinese cohort of Dravet syndrome patients but none in the rest of patients. We demonstrated that truncating/splice site mutations were linked to moderate to severe intellectual disability in these patients. A de novo PCDH19 missense mutation together with an inherited TSPYL4 missense variant were identified in a patient with Dravet syndrome.
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Affiliation(s)
- Anna Ka-Yee Kwong
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Cheuk-Wing Fung
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Siu-Yuen Chan
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Virginia Chun-Nei Wong
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
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36
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Shi YW, Yu MJ, Long YS, Qin B, He N, Meng H, Liu XR, Deng WY, Gao MM, Yi YH, Li BM, Liao WP. Mosaic SCN1A mutations in familial partial epilepsy with antecedent febrile seizures. GENES BRAIN AND BEHAVIOR 2011; 11:170-6. [PMID: 22151702 DOI: 10.1111/j.1601-183x.2011.00756.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
SCN1A is the most relevant epilepsy gene. Mutations of SCN1A generate phenotypes ranging from the extremely severe form of Dravet syndrome (DS) to a mild form of generalized epilepsy with febrile seizures plus (GEFS+). Mosaic SCN1A mutations have been identified in rare familial DS. It is suspected that mosaic mutations of SCN1A may cause other types of familial epilepsies with febrile seizures (FS), which are more common clinically. Thus, we screened SCN1A mutations in 13 families with partial epilepsy with antecedent febrile seizures (PEFS+) using denaturing high-performance liquid chromatography and sequencing. The level of mosaicism was further quantified by pyrosequencing. Two missense SCN1A mutations with mosaic origin were identified in two unrelated families, accounting for 15.4% (2/13) of the PEFS+ families tested. One of the mosaic carriers with ~25.0% mutation of c.5768A>G/p.Q1923R had experienced simple FS; another with ~12.5% mutation of c.4847T>C/p.I1616T was asymptomatic. Their heterozygous children had PEFS+. Recurrent transmission occurred in both families, as noted in most of the families with germline mosaicism reported previously. The two mosaic mutations identified in this study are less destructive missense, compared with the more destructive truncating and splice-site mutations identified in the majority of previous studies. This is the first report of mosaic SCN1A mutations in families with probands that do not exhibit DS, but manifest only a milder phenotype. Therefore, such families with mild cases should be approached with caution in genetic counseling and the possibility of mosaicism origin associated with high recurrence risk should be excluded.
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Affiliation(s)
- Y-W Shi
- Institute of Neuroscience, The Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangdong, China
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37
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Arif B, Grünewald A, Fatima A, Ramirez A, Ali A, Brüggemann N, Würfel J, Rolfs A, Lohmann K, Malik A, Klein C, Naz S. An unusual neurological syndrome of crawling gait, dystonia, pyramidal signs, and limited speech. Mov Disord 2011; 26:2279-83. [PMID: 21953512 DOI: 10.1002/mds.23860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 05/03/2011] [Accepted: 06/08/2011] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND The purpose of the study was to identify and molecularly characterize a neurological syndrome in a consanguineous Pakistani family. METHODS Five patients, their 2 siblings, and their parents were clinically examined. DNA from all 7 siblings was genotyped with Affymetrix SNP arrays and sequencing of selected candidate genes. RESULTS An unusual neurological syndrome of crawling gait, predominant leg dystonia, pyramidal signs, microcephaly, and suspected deafness segregated in the family. Three patients ambulated on hands and knees, either by hopping and crossing their legs, or by dragging the legs behind them. Two patients have acquired the ability to walk bipedally with a dystonic gait. Unexpectedly, no chromosomal region was homozygous in patients only. Under different disease models, we localized 7 chromosomal regions in the genome common to all patients. No pathogenic mutations were identified in selected candidate genes or the mitochondrial genome. CONCLUSION We describe an unusual movement disorder syndrome reminiscent of but distinct from Uner Tan syndrome.
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Affiliation(s)
- Beenish Arif
- School of Biological Sciences, University of the Punjab, Lahore, Pakistan
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38
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The genetics of monogenic idiopathic epilepsies and epileptic encephalopathies. Seizure 2011; 21:3-11. [PMID: 21917483 DOI: 10.1016/j.seizure.2011.08.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 08/06/2011] [Accepted: 08/09/2011] [Indexed: 12/23/2022] Open
Abstract
The group of idiopathic epilepsies encompasses numerous syndromes without known organic substrate. Genetic anomalies are thought to be responsible for pathogenesis, with a monogenic or polygenic model of inheritance. Over the last two decades, a number of genetic anomalies and encoded proteins have been related to particular idiopathic epilepsies and epileptic encephalopathies. Most of these mutations involve subunits of neuronal ion channels (e.g. potassium, sodium, and chloride channels), and may result in abnormal neuronal hyperexcitability manifesting with seizures. However non-ion channel proteins may also be affected. Correlations between genotype and phenotype are not easy to establish, since genetic and non-genetic factors are likely to play a role in determining the severity of clinical features. The growing number of discoveries on this topic are improving classification, prognosis and counseling of patients and families with these forms of epilepsy, and may lead to targeted therapeutic approaches in the near future. In this article the authors have reviewed the main genetic discoveries in the field of the monogenic idiopathic epilepsies and epileptic encephalopathies, in order to provide epileptologists with a concise and comprehensive summary of clinical and genetic features of these seizure disorders.
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39
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Mulley JC, Dibbens LM. Genetic variations and associated pathophysiology in the management of epilepsy. APPLICATION OF CLINICAL GENETICS 2011; 4:113-25. [PMID: 23776372 PMCID: PMC3681183 DOI: 10.2147/tacg.s7407] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The genomic era has enabled the application of molecular tools to the solution of many of the genetic epilepsies, with and without comorbidities. Massively parallel sequencing has recently reinvigorated gene discovery for the monogenic epilepsies. Recurrent and novel copy number variants have given much-needed impetus to the advancement of our understanding of epilepsies with complex inheritance. Superimposed upon that is the phenotypic blurring by presumed genetic modifiers scattering the effects of the primary mutation. The genotype-first approach has uncovered associated syndrome constellations, of which epilepsy is only one of the syndromes. As the molecular genetic basis for the epilepsies unravels, it will increasingly influence the classification and diagnosis of the epilepsies. The ultimate goal of the molecular revolution has to be the design of treatment protocols based on genetic profiles, and cracking the 30% of epilepsies refractory to current medications, but that still lies well into the future. The current focus is on the scientific basis for epilepsy. Understanding its genetic causes and biophysical mechanisms is where we are currently positioned: prizing the causes of epilepsy "out of the shadows" and exposing its underlying mechanisms beyond even the ion-channels.
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Affiliation(s)
- John C Mulley
- Department of Genetic Medicine, Directorate of Genetics and Molecular Pathology, SA Pathology at Women's and Children's Hospital, North Adelaide, Australia ; School of Paediatrics and Reproductive Health, and School of Molecular and Biomedical Sciences, The University of Adelaide, Adelaide, Australia
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40
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Catarino CB, Liu JYW, Liagkouras I, Gibbons VS, Labrum RW, Ellis R, Woodward C, Davis MB, Smith SJ, Cross JH, Appleton RE, Yendle SC, McMahon JM, Bellows ST, Jacques TS, Zuberi SM, Koepp MJ, Martinian L, Scheffer IE, Thom M, Sisodiya SM. Dravet syndrome as epileptic encephalopathy: evidence from long-term course and neuropathology. Brain 2011; 134:2982-3010. [PMID: 21719429 PMCID: PMC3187538 DOI: 10.1093/brain/awr129] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dravet syndrome is an epilepsy syndrome of infantile onset, frequently caused by SCN1A mutations or deletions. Its prevalence, long-term evolution in adults and neuropathology are not well known. We identified a series of 22 adult patients, including three adult post-mortem cases with Dravet syndrome. For all patients, we reviewed the clinical history, seizure types and frequency, antiepileptic drugs, cognitive, social and functional outcome and results of investigations. A systematic neuropathology study was performed, with post-mortem material from three adult cases with Dravet syndrome, in comparison with controls and a range of relevant paediatric tissue. Twenty-two adults with Dravet syndrome, 10 female, were included, median age 39 years (range 20-66). SCN1A structural variation was found in 60% of the adult Dravet patients tested, including one post-mortem case with DNA extracted from brain tissue. Novel mutations were described for 11 adult patients; one patient had three SCN1A mutations. Features of Dravet syndrome in adulthood include multiple seizure types despite polytherapy, and age-dependent evolution in seizure semiology and electroencephalographic pattern. Fever sensitivity persisted through adulthood in 11 cases. Neurological decline occurred in adulthood with cognitive and motor deterioration. Dysphagia may develop in or after the fourth decade of life, leading to significant morbidity, or death. The correct diagnosis at an older age made an impact at several levels. Treatment changes improved seizure control even after years of drug resistance in all three cases with sufficient follow-up after drug changes were instituted; better control led to significant improvement in cognitive performance and quality of life in adulthood in two cases. There was no histopathological hallmark feature of Dravet syndrome in this series. Strikingly, there was remarkable preservation of neurons and interneurons in the neocortex and hippocampi of Dravet adult post-mortem cases. Our study provides evidence that Dravet syndrome is at least in part an epileptic encephalopathy.
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Affiliation(s)
- Claudia B Catarino
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, UCL, Queen Square, London WC1N 3BG, UK
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Marini C, Scheffer IE, Nabbout R, Suls A, De Jonghe P, Zara F, Guerrini R. The genetics of Dravet syndrome. Epilepsia 2011; 52 Suppl 2:24-9. [DOI: 10.1111/j.1528-1167.2011.02997.x] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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42
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Abstract
Before the advent of molecular genetics, the nature of Dravet syndrome remained largely obscure, and arguments in favour of either an acquired origin, such as the occurrence of Dravet syndrome after vaccination, or an inherited origin, such as the occurrence of epilepsy in relatives, were formulated. In 2001 we demonstrated that the majority of Dravet patients have a genetic cause due to loss-of-function mutations in the SCN1A gene. Understandably, since this syndrome severely affects reproductive fitness, these mutations almost exclusively arise de novo, with the rare exceptions of mosaic mutations in a non-affected transmitting parent. Besides classical Sanger sequencing, mutation analysis of the SCN1A gene also requires a method that allows the detection of genomic rearrangements (MAQ, MLPA), since microdeletions or whole gene deletions also result in Dravet syndromes. Depending on the series reported and their recruitment strategies, the yield of SCN1A mutations detected varied from 50 to 80%, implying that other genes or factors must be involved in these 'SCN1A-negative Dravet patients'. Recently mutations in some other genes have been described in these genuine Dravet patients who do not carry an SCN1A mutation. The second most important Dravet-associated gene is PCDH19.These patients initially may have all characteristics of Dravet syndrome but may later run a somewhat different course.
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Affiliation(s)
- Peter De Jonghe
- Neurogenetic Group, VIB Department of Molecular Genetics, University of Antwerp, Belgium.
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43
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Yordanova I, Todorov T, Dimova P, Hristova D, Tincheva R, Litvinenko I, Yotovska O, Kremensky I, Todorova A. One novel Dravet syndrome causing mutation and one recurrent MAE causing mutation in SCN1A gene. Neurosci Lett 2011; 494:180-3. [PMID: 21396429 DOI: 10.1016/j.neulet.2011.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 03/02/2011] [Accepted: 03/02/2011] [Indexed: 11/16/2022]
Abstract
Mutations in SCN1A gene, encoding the voltage-gated sodium channel α1-subunit, are found to be associated with severe myoclonic epilepsy in infancy or Dravet syndrome (DS), but only rarely with the myoclonic astatic epilepsy (MAE, or Doose syndrome). We report on two patients with SCN1A mutations and severe epilepsy within the spectrum of generalized epilepsy with febrile seizures plus syndrome (GEFS+), the phenotypes being consistent with DS and MAE, respectively. Analysis of SCN1A revealed a heterozygous de novo frameshift mutation (c.4205_4208delGAAA) in the patient with DS, and a recurrent missense mutation (c.3521C>G) in that suffering from MAE. The missense mutation has been reported in patients with neurological diseases of various manifestations, which suggests that this variability is likely to result from the modifying effects of other genetic or environmental factors. DS phenotype has been mainly found associated with truncation mutations, while predominantly missense mutations and very few prematurely terminating substitutions have been reported in GEFS+ patients.
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Affiliation(s)
- Iglika Yordanova
- National Genetic Laboratory, Sofia Medical University, Sofia, Bulgaria.
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Morse RP. Dravet syndrome: inroads into understanding epileptic encephalopathies. J Pediatr 2011; 158:354-9. [PMID: 21163495 DOI: 10.1016/j.jpeds.2010.10.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 08/17/2010] [Accepted: 10/21/2010] [Indexed: 12/17/2022]
Affiliation(s)
- Richard P Morse
- Section of Neurology and Development, Department of Pediatrics, Children's Hospital at Dartmouth, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756, USA.
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Nicita F, Spalice A, Papetti L, Ursitti F, Parisi P, Gennaro E, Zara F, Iannetti P. Genotype-phenotype correlations in a group of 15 SCN1A-mutated Italian patients with GEFS+ spectrum (seizures plus, classical and borderline severe myoclonic epilepsy of infancy). J Child Neurol 2010; 25:1369-76. [PMID: 20729507 DOI: 10.1177/0883073810365737] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mutations in SCN1A gene have been associated with the spectrum of generalized/genetic epilepsy with febrile seizures plus. Recently, databases reporting SCN1A mutations and clinical details of patients have been created to facilitate genotype- phenotype correlations, actually not completely defined, particularly if a specific mutation underlies phenotypes. We report on a group of 15 patients with clinical features of GEFS+ (3), classical (7), or borderline severe myoclonic epilepsy of infancy (5), in whom genetic analysis of patients and parents and follow-up period were performed to establish genotype-phenotype correlations, to enrich literature and databases data. We found 11 pathogenic mutations (5 novel: c.80 G>C exon 1; c.187 T>C exon 1; c.3061 G>T exon 16; c.4297 G>A exon 22; c.5579 delA ins TCTCC exon 26) and 4 novel nucleotidic variants (IVS5+38 C>T intron 5; IVS8-19 C>T intron 18; c.4945 C>T exon 25; c.5127 C>A exon 26). Paternal inheritance was observed in 4/4 cases.
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Affiliation(s)
- Francesco Nicita
- Child Neurology, Paediatric Department, I Faculty of Medicine, Sapienza University c/o Policlinico Umberto I, Rome, Italy
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Abstract
Mutations in a number of genes encoding voltage-gated sodium channels cause a variety of epilepsy syndromes in humans, including genetic (generalized) epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (DS, severe myoclonic epilepsy of infancy). Most of these mutations are in the SCN1A gene, and all are dominantly inherited. Most of the mutations that cause DS result in loss of function, whereas all of the known mutations that cause GEFS+ are missense, presumably altering channel activity. Family members with the same GEFS+ mutation often display a wide range of seizure types and severities, and at least part of this variability likely results from variation in other genes. Many different biophysical effects of SCN1A-GEFS+ mutations have been observed in heterologous expression systems, consistent with both gain and loss of channel activity. However, results from mouse models suggest that the primary effect of both GEFS+ and DS mutations is to decrease the activity of GABAergic inhibitory neurons. Decreased activity of the inhibitory circuitry is thus likely to be a major factor contributing to seizure generation in patients with GEFS+ and DS, and may be a general consequence of SCN1A mutations.
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Affiliation(s)
- Andrew Escayg
- Department of Human Genetics, Emory University, Atlanta, Georgia 30322, USA.
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Vadlamudi L, Dibbens LM, Lawrence KM, Iona X, McMahon JM, Murrell W, Mackay-Sim A, Scheffer IE, Berkovic SF. Timing of de novo mutagenesis--a twin study of sodium-channel mutations. N Engl J Med 2010; 363:1335-40. [PMID: 20879882 DOI: 10.1056/nejmoa0910752] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
De novo mutations are a cause of sporadic disease, but little is known about the developmental timing of such mutations. We studied concordant and discordant monozygous twins with de novo mutations in the sodium channel α1 subunit gene (SCN1A) causing Dravet's syndrome, a severe epileptic encephalopathy. On the basis of our findings and the literature on mosaic cases, we conclude that de novo mutations in SCN1A may occur at any time, from the premorula stage of the embryo (causing disease in the subject) to adulthood (with mutations in the germ-line cells of parents causing disease in offspring).
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Affiliation(s)
- Lata Vadlamudi
- Epilepsy Research Center, Austin Health, University of Melbourne, Melbourne, VIC, Australia
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Scheffer IE, Zhang YH, Gecz J, Dibbens L. Genetics of the epilepsies: genetic twists in the channels and other tales. Epilepsia 2010; 51 Suppl 1:33-6. [PMID: 20331710 DOI: 10.1111/j.1528-1167.2009.02440.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ingrid E Scheffer
- Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, Victoria, Australia.
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Sun H, Zhang Y, Liu X, Ma X, Yang Z, Qin J, Jiang Y, Qi Y, Wu X. Analysis of SCN1A mutation and parental origin in patients with Dravet syndrome. J Hum Genet 2010; 55:421-7. [PMID: 20431604 DOI: 10.1038/jhg.2010.39] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dravet syndrome (DS) or severe myoclonic epilepsy of infancy is an intractable epileptic syndrome that is caused by mutations in the neuronal voltage-gated sodium channel alpha1 subunit gene SCN1A. We investigated SCN1A mutations in 63 Chinese patients with DS and analyzed its inheritance. Genomic DNA was extracted from peripheral blood lymphocytes of DS patients and their available parents. The SCN1A open reading frame sequence was analyzed by PCR-DNA sequencing and multiple ligation-dependent probe amplication (MLPA). If the mutation was de novo, we used allele-specific PCR (AS-PCR) to determine the parental origin. Of the 63 patients examined, 49 unrelated patients had SCN1A mutations. The mutation rate was 77.8% (49 of 63), in which 61.2% (30 of 49) were truncation mutations. The mutations included 19 missense mutations, 14 frame-shift mutations, 6 nonsense mutations, 8 splice-site mutations. Through MLPA analysis, deletions or duplications of large fragments accounted for 12.5% (2 of 16) in PCR-sequencing-negative patients. By testing parents for the mutation, 40 mutations were found to be de novo and one mutation was inherited from a mother who was mosaic for a mutation. By AS-PCR analysis in 12 patients with de novo mutations, 10 were confirmed paternal in origin and 2 were maternal in origin. Thirty of the SCN1A mutations reported here have not been previously reported. Approximately 80% of Chinese DS patients have SCN1A mutations. MLPA analysis was essential for PCR-sequencing-negative patients. The majority of SCN1A mutations were de novo, most of which were paternal origin.
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Affiliation(s)
- Huihui Sun
- Department of Pediatrics, Peking University First Hospital, Beijing, PR China
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