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Eckhaus J, Lawrence KM, Helbig I, Bui M, Vadlamudi L, Hopper JL, Scheffer IE, Berkovic SF. Genetics of febrile seizure subtypes and syndromes: a twin study. Epilepsy Res 2013; 105:103-9. [PMID: 23522981 DOI: 10.1016/j.eplepsyres.2013.02.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 12/27/2012] [Accepted: 02/12/2013] [Indexed: 01/30/2023]
Abstract
PURPOSE Febrile seizures (FS) are the most common seizure syndrome. A strong genetic component has been well established through family and twin studies; however, such studies have not examined the genetics of different FS types (simple, complex, febrile status epilepticus) and sub-syndromes (true FS, febrile seizures plus (FS+), 'FS with later epilepsy'). Here we used a community-based twin sample to analyze genetic factors within different FS subtypes and FS syndromes. METHODS Twin pairs were ascertained from the twin database of the Epilepsy Research Centre. A retrospective chart review was conducted and follow-up attempted for all subjects. Casewise concordance values were calculated for the different subgroups and intra-pair variation was analyzed. KEY FINDINGS One hundred and seventy-nine twin pairs with FS were identified. Overall casewise concordance for FS in monozygotic (MZ) twins (0.62) was greater than in dizygotic (DZ) twins (0.16, p<0.0001). A greater concordance amongst MZ pairs than DZ twin pairs was also observed for all FS subtypes and FS sub-syndromes, particularly in twins with FS+. Within concordant MZ pairs, we did not observe the co-occurrence of FS and FS+. SIGNIFICANCE These results suggest a strong genetic contribution to different FS subtypes and sub-syndromes. They also support the existence of distinct genetic factors for different FS subtypes and sub-syndromes, especially FS+. This information is important for the strategic planning of next generation sequencing studies of febrile seizures.
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Weckhuysen S, Holmgren P, Hendrickx R, Jansen AC, Hasaerts D, Dielman C, de Bellescize J, Boutry-Kryza N, Lesca G, Von Spiczak S, Helbig I, Gill D, Yendle S, Møller RS, Klitten L, Korff C, Godfraind C, Van Rijckevorsel K, De Jonghe P, Hjalgrim H, Scheffer IE, Suls A. Reduction of seizure frequency after epilepsy surgery in a patient with STXBP1 encephalopathy and clinical description of six novel mutation carriers. Epilepsia 2013; 54:e74-80. [PMID: 23409955 DOI: 10.1111/epi.12124] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/17/2013] [Indexed: 01/10/2023]
Abstract
Mutations in STXBP1 have been identified in a subset of patients with early onset epileptic encephalopathy (EE), but the full phenotypic spectrum remains to be delineated. Therefore, we screened a cohort of 160 patients with an unexplained EE, including patients with early myoclonic encephalopathy (EME), Ohtahara syndrome, West syndrome, nonsyndromic EE with onset in the first year, and Lennox-Gastaut syndrome (LGS). We found six de novo mutations in six patients presenting as Ohtahara syndrome (2/6, 33%), West syndrome (1/65, 2%), and nonsyndromic early onset EE (3/64, 5%). No mutations were found in LGS or EME. Only two of four mutation carriers with neonatal seizures had Ohtahara syndrome. Epileptic spasms were present in five of six patients. One patient with normal magnetic resonance imaging (MRI) but focal seizures underwent epilepsy surgery and seizure frequency dropped drastically. Neuropathology showed a focal cortical dysplasia type 1a. There is a need for additional neuropathologic studies to explore whether STXBP1 mutations can lead to structural brain abnormalities.
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Moehring J, von Spiczak S, Moeller F, Helbig I, Wolff S, Jansen O, Muhle H, Boor R, Stephani U, Siniatchkin M. Variability of EEG-fMRI findings in patients withSCN1A-positive Dravet syndrome. Epilepsia 2013; 54:918-26. [DOI: 10.1111/epi.12119] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2013] [Indexed: 01/18/2023]
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204
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Kirov A, Dimova P, Todorova A, Mefford H, Todorov T, Saraylieva G, Bojinova V, Mitev V, Helbig I. 15q13.3 microdeletions in a prospectively recruited cohort of patients with idiopathic generalized epilepsy in Bulgaria. Epilepsy Res 2013; 104:241-5. [PMID: 23352738 DOI: 10.1016/j.eplepsyres.2012.10.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 10/11/2012] [Accepted: 10/30/2012] [Indexed: 01/12/2023]
Abstract
PURPOSE The chromosome 15q13.3 region is a genomic rearrangement hotspot linked to idiopathic generalized epilepsies (IGEs) and such rearrangements remain the strongest risk factor for IGE known to date. Increasing evidence suggests that genetic variations can be highly population-specific. Therefore, we aimed to assess the frequency of 15q13.3 microdeletions in IGE patients from Bulgaria. METHODS A cohort of 100 patients with various IGE syndromes was screened for large deletions/duplications by MLPA. All deletions and duplications were confirmed by array CGH analysis as previously described. RESULTS In 100 prospectively recruited Bulgarian patients with IGE, we found one case with a microdeletion, which amounted to 1% frequency for this copy number variant. CONCLUSION We confirm the frequency of 1% for the 15q13.3 microdeletion in a prospectively recruited cohort of Bulgarian epilepsy patients, demonstrating that this variation represents a significant risk factor for IGE for various populations and that it is retrospectively detected frequency is not due to selection bias.
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Muhle H, Helbig I, Frøslev TG, Suls A, von Spiczak S, Klitten LL, Dahl HA, Brusgaard K, Neubauer B, De Jonghe P, Tommerup N, Stephani U, Hjalgrim H, Møller RS. The role of SLC2A1 in early onset and childhood absence epilepsies. Epilepsy Res 2013; 105:229-33. [PMID: 23306390 DOI: 10.1016/j.eplepsyres.2012.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 11/24/2012] [Indexed: 11/15/2022]
Abstract
Early Onset Absence Epilepsy constitutes an Idiopathic Generalized Epilepsy with absences starting before the age of four years. Mutations in SLC2A1, encoding the glucose transporter, account for approximately 10% of EOAE cases. The role of SLC2A1 mutations in absence epilepsies with a later onset has not been assessed. We found two mutation carriers in 26 EOAE patients, while no mutations were found in 124 probands affected by CAE or JAE.
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Møller RS, Weber YG, Klitten LL, Trucks H, Muhle H, Kunz WS, Mefford HC, Franke A, Kautza M, Wolf P, Dennig D, Schreiber S, Rückert IM, Wichmann HE, Ernst JP, Schurmann C, Grabe HJ, Tommerup N, Stephani U, Lerche H, Hjalgrim H, Helbig I, Sander T. Exon-disrupting deletions of NRXN1 in idiopathic generalized epilepsy. Epilepsia 2013; 54:256-64. [PMID: 23294455 DOI: 10.1111/epi.12078] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/14/2012] [Indexed: 11/27/2022]
Abstract
PURPOSE Neurexins are neuronal adhesion molecules located in the presynaptic terminal, where they interact with postsynaptic neuroligins to form a transsynaptic complex required for efficient neurotransmission in the brain. Recently, deletions and point mutations of the neurexin 1 (NRXN1) gene have been associated with a broad spectrum of neuropsychiatric disorders. This study aimed to investigate if NRXN1 deletions also increase the risk of idiopathic generalized epilepsies (IGEs). METHODS We screened for deletions involving the NRXN1 gene in 1,569 patients with IGE and 6,201 controls using high-density oligonucleotide microarrays. KEY FINDINGS We identified exon-disrupting deletions of NRXN1 in 5 of 1,569 patients with IGE and 2 of 6,201 control individuals (p = 0.0049; odds ratio (OR) 9.91, 95% confidence interval (CI) 1.92-51.12). A complex familial segregation pattern in the IGE families was observed, suggesting that heterozygous NRXN1 deletions are susceptibility variants. Intriguingly, we identified a second large copy number variant in three of five index patients, supporting an involvement of heterogeneous susceptibility alleles in the etiology of IGE. SIGNIFICANCE We conclude that exon-disrupting deletions of NRXN1 represent a genetic risk factor in the genetically complex predisposition of common IGE syndromes.
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Appenzeller S, Helbig I, Stephani U, Häusler M, Kluger G, Bungeroth M, Müller S, Kuhlenbäumer G, van Baalen A. Febrile infection-related epilepsy syndrome (FIRES) is not caused by SCN1A, POLG, PCDH19 mutations or rare copy number variations. Dev Med Child Neurol 2012; 54:1144-8. [PMID: 23066759 DOI: 10.1111/j.1469-8749.2012.04435.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Febrile infection-related epilepsy syndrome (FIRES) is an enigmatic seizure disorder in childhood with an innocuous febrile infection triggering severe and intractable multifocal epilepsy, mostly with status epilepticus. FIRES shares several phenotypic features with epilepsies seen in patients with protocadherin 19 (PCDH19), sodium channel protein type 1 subunit alpha (SCN1A), and DNA polymerase subunit gamma-1 (POLG) mutations. The aim of the study was the mutation analysis of these prime candidate genes in a cohort of patients with FIRES. Additionally, given that rare copy number variations (CNVs) have recently been established as important risk factors for epilepsies, we performed a genome-wide CNV analysis. METHOD We analysed the protein coding region, including splice sites of the three candidate genes in 15 patients (eight males, seven females) with FIRES (age at onset 3-15 y, median 6) using Sanger sequencing. Inclusion criteria were a status epilepticus without identifiable cause and a preceding febrile infection in previously healthy children. In addition, we performed genome-wide human single-nucleotide polymorphism 6.0 arrays in a subset of 10 patients to identify pathological CNVs. RESULTS We could not identify the most likely pathogenic mutations or CNVs in FIRES. INTERPRETATION Mutations in PCDH19, SCN1A, POLG, or CNVs are not responsible for FIRES.
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Steffens M, Leu C, Ruppert AK, Zara F, Striano P, Robbiano A, Capovilla G, Tinuper P, Gambardella A, Bianchi A, La Neve A, Crichiutti G, de Kovel CGF, Kasteleijn-Nolst Trenité D, de Haan GJ, Lindhout D, Gaus V, Schmitz B, Janz D, Weber YG, Becker F, Lerche H, Steinhoff BJ, Kleefuß-Lie AA, Kunz WS, Surges R, Elger CE, Muhle H, von Spiczak S, Ostertag P, Helbig I, Stephani U, Møller RS, Hjalgrim H, Dibbens LM, Bellows S, Oliver K, Mullen S, Scheffer IE, Berkovic SF, Everett KV, Gardiner MR, Marini C, Guerrini R, Lehesjoki AE, Siren A, Guipponi M, Malafosse A, Thomas P, Nabbout R, Baulac S, Leguern E, Guerrero R, Serratosa JM, Reif PS, Rosenow F, Mörzinger M, Feucht M, Zimprich F, Kapser C, Schankin CJ, Suls A, Smets K, De Jonghe P, Jordanova A, Caglayan H, Yapici Z, Yalcin DA, Baykan B, Bebek N, Ozbek U, Gieger C, Wichmann HE, Balschun T, Ellinghaus D, Franke A, Meesters C, Becker T, Wienker TF, Hempelmann A, Schulz H, Rüschendorf F, Leber M, Pauck SM, Trucks H, Toliat MR, Nürnberg P, Avanzini G, Koeleman BPC, Sander T. Genome-wide association analysis of genetic generalized epilepsies implicates susceptibility loci at 1q43, 2p16.1, 2q22.3 and 17q21.32. Hum Mol Genet 2012; 21:5359-72. [PMID: 22949513 DOI: 10.1093/hmg/dds373] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Genetic generalized epilepsies (GGEs) have a lifetime prevalence of 0.3% and account for 20-30% of all epilepsies. Despite their high heritability of 80%, the genetic factors predisposing to GGEs remain elusive. To identify susceptibility variants shared across common GGE syndromes, we carried out a two-stage genome-wide association study (GWAS) including 3020 patients with GGEs and 3954 controls of European ancestry. To dissect out syndrome-related variants, we also explored two distinct GGE subgroups comprising 1434 patients with genetic absence epilepsies (GAEs) and 1134 patients with juvenile myoclonic epilepsy (JME). Joint Stage-1 and 2 analyses revealed genome-wide significant associations for GGEs at 2p16.1 (rs13026414, P(meta) = 2.5 × 10(-9), OR[T] = 0.81) and 17q21.32 (rs72823592, P(meta) = 9.3 × 10(-9), OR[A] = 0.77). The search for syndrome-related susceptibility alleles identified significant associations for GAEs at 2q22.3 (rs10496964, P(meta) = 9.1 × 10(-9), OR[T] = 0.68) and at 1q43 for JME (rs12059546, P(meta) = 4.1 × 10(-8), OR[G] = 1.42). Suggestive evidence for an association with GGEs was found in the region 2q24.3 (rs11890028, P(meta) = 4.0 × 10(-6)) nearby the SCN1A gene, which is currently the gene with the largest number of known epilepsy-related mutations. The associated regions harbor high-ranking candidate genes: CHRM3 at 1q43, VRK2 at 2p16.1, ZEB2 at 2q22.3, SCN1A at 2q24.3 and PNPO at 17q21.32. Further replication efforts are necessary to elucidate whether these positional candidate genes contribute to the heritability of the common GGE syndromes.
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Helbig I, Lawrence KM, Connellan MM, Torn-Broers Y, Vadlamudi L, Eckhaus J, Milne RL, Hopper JL, Berkovic SF. Obstetric Events as a Risk Factor for Febrile Seizures: A Community-Based Twin Study. Twin Res Hum Genet 2012; 11:634-40. [DOI: 10.1375/twin.11.6.634] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractAdverse events during the perinatal period have traditionally been thought to contribute to the risk of febrile seizures although an association has not been found in large epidemiological studies. Disease-discordant twins provide a means to assess the role of non-shared environmental factors while matching for confounding factors and avoiding difficulties of epidemiological studies in singletons. This study aimed to examine the association of obstetric events and febrile seizures in a community-based twin study. Twenty-one twin pairs discordant for febrile seizures were ascertained from a community-based twin register. Obstetric events were scored using the McNeil-Sjöström Scale for Obstetric Complications and expressed as a summary score (OC score). The frequency of individual obstetric events in affected and unaffected twins, the within-pair differences in OC scores and other markers of perinatal risk including birthweight, birth order and Apgar scores were examined. No significant difference was found in the frequency of individual obstetric events, nor in OC scores between affected and unaffected twins. No differences in birth weight, birth order, 1- or 5-minute Apgar scores were observed. Our results confirm previous findings that obstetric events are not associated with the risk of febrile seizures.
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Muhle H, Mefford HC, Obermeier T, von Spiczak S, Eichler EE, Stephani U, Sander T, Helbig I. Absence seizures with intellectual disability as a phenotype of the 15q13.3 microdeletion syndrome. Epilepsia 2011; 52:e194-8. [PMID: 22050399 PMCID: PMC3270691 DOI: 10.1111/j.1528-1167.2011.03301.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
15q13.3 microdeletions are the most common genetic findings identified in idiopathic generalized epilepsies to date, and they are present in up to 1% of patients. In addition, 15q13.3 microdeletions have been described in patients with epilepsy as part of a complex neurodevelopmental phenotype. We analyzed a cohort of 570 patients with various pediatric epilepsies for 15q13.3 microdeletions. Screening was performed using quantitative polymerase chain reaction; deletions were confirmed by array comparative genomic hybridization (CGH). We carried out detailed phenotyping of deletion carriers. In total, we identified four pediatric patients with 15q13.3 microdeletions, including one previously described patient. Two of four deletions were de novo, one deletion was inherited from an unaffected parent, and for one patient the inheritance is unknown. All four patients had absence epilepsy with various degrees of intellectual disability. We suggest that absence epilepsy accompanied by intellectual disability may represent a common phenotype of the 15q13.3 microdeletion in pediatric patients with epilepsy.
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211
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von Spiczak S, Finsterwalder K, Muhle H, Franke A, Schilhabel M, Stephani U, Helbig I. Comprehensive analysis of candidate genes for photosensitivity using a complementary bioinformatic and experimental approach. Epilepsia 2011; 52:e143-7. [PMID: 21883175 DOI: 10.1111/j.1528-1167.2011.03197.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Photoparoxysmal response (PPR) is a highly heritable electroencephalographic trait characterized by an increased sensitivity to photic stimulation. It may serve as an endophenotype for idiopathic generalized epilepsy. Family linkage studies identified susceptibility loci for PPR on chromosomes 5q35.3, 8q21.13, and 16p13.3. This study aimed to identify key candidate genes within these loci. We used bioinformatics tools for gene prioritization integrating information on biologic function, sequence data, gene expression, and others. The prime candidate gene from this analysis was sequenced in 48 photopositive probands. Presumed functional implications of identified polymorphisms were investigated using bioinformatics methods. The glutamate receptor subunit gene GRIN2A was identified as a prime candidate gene. Sequence analysis revealed various new polymorphisms. None of the identified variants was predicted to be functionally relevant. We objectified the selection of candidate genes for PPR without an a priori hypothesis. Particularly among the various ion channel genes in the linkage regions, GRIN2A was identified as the prime candidate gene. GRIN2A mutations have recently been identified in various epilepsies. Even though our mutation analysis failed to demonstrate direct involvement of GRIN2A in photosensitivity, in silico gene prioritization may provide a useful tool for the identification of candidate genes within large genomic regions.
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von Spiczak S, Helbig I, Drechsel-Baeuerle U, Muhle H, van Baalen A, van Kempen MJ, Lindhout D, Scheffer IE, Berkovic SF, Stephani U, Keller-Stanislawski B. A retrospective population-based study on seizures related to childhood vaccination. Epilepsia 2011; 52:1506-12. [DOI: 10.1111/j.1528-1167.2011.03134.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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213
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Tro-Baumann B, von Spiczak S, Lotte J, Bast T, Haberlandt E, Sassen R, Freund A, Leiz S, Stephani U, Boor R, Holthausen H, Helbig I, Kluger G. A retrospective study of the relation between vaccination and occurrence of seizures in Dravet syndrome. Epilepsia 2011; 52:175-8. [PMID: 21219303 DOI: 10.1111/j.1528-1167.2010.02885.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Dravet syndrome is a severe epileptic encephalopathy starting in the first year of life. Mutations in SCN1A can be identified in the majority of patients, and epileptic seizures in the setting of fever are a clinical hallmark. Fever is also commonly seen after vaccinations and provocation of epileptic seizures by vaccinations in patients with Dravet syndrome has been reported, but not systematically assessed. In a retrospective evaluation of 70 patients with Dravet syndrome and SCN1A mutations, seizures following vaccinations were reported in 27%. In 58% of these patients vaccination-related seizures represented the first clinical manifestation. The majority of seizures occurred after DPT vaccinations and within 72 h after vaccination. Two-thirds of events occurred in the context of fever. Our findings highlight seizures after vaccinations as a common feature in Dravet syndrome and emphasize the need for preventive measures for seizures triggered by vaccination or fever in these children.
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Reutlinger C, Helbig I, Gawelczyk B, Subero JIM, Tönnies H, Muhle H, Finsterwalder K, Vermeer S, Pfundt R, Sperner J, Stefanova I, Gillessen-Kaesbach G, von Spiczak S, van Baalen A, Boor R, Siebert R, Stephani U, Caliebe A. Deletions in 16p13 including GRIN2A in patients with intellectual disability, various dysmorphic features, and seizure disorders of the rolandic region. Epilepsia 2010; 51:1870-3. [PMID: 20384727 DOI: 10.1111/j.1528-1167.2010.02555.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Seizure disorders of the rolandic region comprise a spectrum of different epilepsy syndromes ranging from benign rolandic epilepsy to more severe seizure disorders including atypical benign partial epilepsy/pseudo-Lennox syndrome,electrical status epilepticus during sleep, and Landau-Kleffner syndrome. Centrotemporal spikes are the unifying electroencephalographic hallmark of these benign focal epilepsies, indicating a pathophysiologic relationship between the various epilepsies arising from the rolandic region. The etiology of these epilepsies is elusive, but a genetic component is assumed given the heritability of the characteristic electrographic trait. Herein we report on three patients with intellectual disability, various dysmorphic features, and epilepsies involving the rolandic region, carrying previously undescribed deletions in 16p13. The only gene located in the critical region shared by all three patients is GRIN2A coding for the alpha-2 subunit of the neuronal N-methyl-D-aspartate(NMDA) receptor.
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Muhle H, Steinich I, von Spiczak S, Franke A, Weber Y, Lerche H, Wittig M, Heidemann S, Suls A, de Jonghe P, Marini C, Guerrini R, Scheffer IE, Berkovic SF, Stephani U, Siebert R, Sander T, Helbig I, Tönnies H. A duplication in 1q21.3 in a family with early onset and childhood absence epilepsy. Epilepsia 2010; 51:2453-6. [PMID: 21204805 DOI: 10.1111/j.1528-1167.2010.02712.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Early onset absence epilepsy (EOAE) starting before the age of 4 years constitutes a rare subgroup of the idiopathic generalized epilepsies (IGEs). A strong genetic component in IGE has been suggested by twin and family studies. We describe a boy with absence seizures starting at the age of 9 months whose parents both had childhood absence epilepsy. A 192-kb duplication in 1q21.3 was identified in the proband and his father, encompassing the gene CHRNB2 coding for the β-2 subunit of the nicotinic acetylcholine receptor and the gene ADAR coding for adenosine deaminase, an enzyme responsible for RNA editing. Both are candidate genes for seizure disorders. The duplication was not identified in 191 independent IGE patients (93 EOAE; 98 classical IGE) or in 1,157 population controls.
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Helbig I, Sammler E, Eliava M, Bolshakov AP, Rozov A, Bruzzone R, Monyer H, Hormuzdi SG. In vivo evidence for the involvement of the carboxy terminal domain in assembling connexin 36 at the electrical synapse. Mol Cell Neurosci 2010; 45:47-58. [PMID: 20510366 PMCID: PMC3025355 DOI: 10.1016/j.mcn.2010.05.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 05/03/2010] [Accepted: 05/15/2010] [Indexed: 12/03/2022] Open
Abstract
Connexin 36 (Cx36)-containing electrical synapses contribute to the timing and amplitude of neural responses in many brain regions. A Cx36-EGFP transgenic was previously generated to facilitate their identification and study. In this study we demonstrate that electrical coupling is normal in transgenic mice expressing Cx36 from the genomic locus and suggest that fluorescent puncta present in brain tissue represent distributed electrical synapses. These qualities emphasize the usefulness of the Cx36-EGFP reporter as a tool for the detailed anatomical characterization of electrical synapses in fixed and living tissue. However, though the fusion protein is able to form gap junctions between Xenopus laevis oocytes it is unable to restore electrical coupling to interneurons in the Cx36-deficient mouse. Further experiments in transgenic tissue and non-neural cell lines reveal impaired transport to the plasma membrane as the possible cause. By analyzing the functional deficits exhibited by the fusion protein in vivo and in vitro, we identify a motif within Cx36 that may interact with other trafficking or scaffold proteins and thereby be responsible for its incorporation into electrical synapses.
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Wittig M, Helbig I, Schreiber S, Franke A. CNVineta: a data mining tool for large case-control copy number variation datasets. Bioinformatics 2010; 26:2208-9. [PMID: 20605930 PMCID: PMC2922892 DOI: 10.1093/bioinformatics/btq356] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 06/05/2010] [Accepted: 06/29/2010] [Indexed: 11/12/2022] Open
Abstract
MOTIVATION Copy number variation (CNV), a major contributor to human genetic variation, comprises >/= 1 kb genomic deletions and insertions. Yet, the identification of CNVs from microarray data is still hampered by high false negative and positive prediction rates due to the noisy nature of the raw data. Here, we present CNVineta, an R package for rapid data mining and visualization of CNVs in large case-control datasets genotyped with single nucleotide polymorphism oligonucleotide arrays. CNVineta is compatible with various established CNV prediction algorithms, can be used for genome-wide association analysis of rare and common CNVs and enables rapid and serial display of log(2) of raw data ratios as well as B-allele frequencies for visual quality inspection. In summary, CNVineta aides in the interpretation of large-scale CNV datasets and prioritization of target regions for follow-up experiments. AVAILABILITY AND IMPLEMENTATION CNVineta is available as an R package and can be downloaded from http://www.ikmb.uni-kiel.de/CNVineta/; the package contains a tutorial outlining a typical workflow. The CNVineta compatible HapMap dataset can also be downloaded from the link above.
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Mefford HC, Muhle H, Ostertag P, von Spiczak S, Buysse K, Baker C, Franke A, Malafosse A, Genton P, Thomas P, Gurnett CA, Schreiber S, Bassuk AG, Guipponi M, Stephani U, Helbig I, Eichler EE. Genome-wide copy number variation in epilepsy: novel susceptibility loci in idiopathic generalized and focal epilepsies. PLoS Genet 2010; 6:e1000962. [PMID: 20502679 PMCID: PMC2873910 DOI: 10.1371/journal.pgen.1000962] [Citation(s) in RCA: 345] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 04/20/2010] [Indexed: 11/18/2022] Open
Abstract
Epilepsy is one of the most common neurological disorders in humans with a prevalence of 1% and a lifetime incidence of 3%. Several genes have been identified in rare autosomal dominant and severe sporadic forms of epilepsy, but the genetic cause is unknown in the vast majority of cases. Copy number variants (CNVs) are known to play an important role in the genetic etiology of many neurodevelopmental disorders, including intellectual disability (ID), autism, and schizophrenia. Genome-wide studies of copy number variation in epilepsy have not been performed. We have applied whole-genome oligonucleotide array comparative genomic hybridization to a cohort of 517 individuals with various idiopathic, non-lesional epilepsies. We detected one or more rare genic CNVs in 8.9% of affected individuals that are not present in 2,493 controls; five individuals had two rare CNVs. We identified CNVs in genes previously implicated in other neurodevelopmental disorders, including two deletions in AUTS2 and one deletion in CNTNAP2. Therefore, our findings indicate that rare CNVs are likely to contribute to a broad range of generalized and focal epilepsies. In addition, we find that 2.9% of patients carry deletions at 15q11.2, 15q13.3, or 16p13.11, genomic hotspots previously associated with ID, autism, or schizophrenia. In summary, our findings suggest common etiological factors for seemingly diverse diseases such as ID, autism, schizophrenia, and epilepsy.
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Helbig I, Fölster-Holst R, Brasch J, Hausser I, van Baalen A, Muhle H, Alfke K, Caliebe A, Stephani U, Happle R. Dyschromatosis ptychotropica: an unusual pigmentary disorder in a boy with epileptic encephalopathy and progressive atrophy of the central nervous system-a novel entity? Eur J Pediatr 2010; 169:495-500. [PMID: 19707786 DOI: 10.1007/s00431-009-1046-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 08/05/2009] [Indexed: 11/28/2022]
Abstract
The skin and the central nervous system are tissues of common ectodermal origin and share a close ontogenetic relationship. Genetic diseases primarily affecting both organ systems are regularly encountered in both dermatological and neurological settings. Here, we report on a boy with epileptic encephalopathy, severe intellectual disability, optic atrophy, and progressive cerebellar and supratentorial atrophy, reminiscent of progressive encephalopathy with edema and hypsarrythmia (PEHO) syndrome displaying a previously undescribed dyschromatosis in the form of progressive reticulate and mottled hyper- and hypopigmentation of the neck and the inguinal and axillary regions. We hypothesised that this combination of neurological and cutaneous findings has a common aetiology and represents a novel recognisable entity. Because of the unusual dermatological findings, we suggest the term dyschromatosis ptychotropica. Recognition of further cases may help elucidate the aetiology of this condition and give insight into the pathophysiology of both pigmentation disorders and epileptic encephalopathies.
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Muhle H, von Spiczak S, Gaus V, Kara S, Helbig I, Hampe J, Franke A, Weber Y, Lerche H, Kleefuss-Lie AA, Elger CE, Schreiber S, Stephani U, Sander T. Role of GRM4 in idiopathic generalized epilepsies analysed by genetic association and sequence analysis. Epilepsy Res 2010; 89:319-26. [PMID: 20338729 DOI: 10.1016/j.eplepsyres.2010.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 02/02/2010] [Accepted: 02/14/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND GRM4 encoding the group III metabotropic glutamate receptor 4 (mGluR4), is located on the chromosomal segment 6p21.3 where tentative susceptibility loci for Juvenile Myoclonic Epilepsy (JME) and Photoparoxysmal Response (PPR) have been mapped. The present candidate gene study examined if variation in GRM4 confers susceptibility to IGE. PATIENTS AND METHODS The case-control association sample included 564 unrelated IGE patients and 733 population controls of German descent. Association analysis was carried out for 17 single nucleotide polymorphisms (SNPs) covering the genomic GRM4 sequence for all IGE patients as well as for two common IGE subsyndromes [Juvenile Myoclonic Epilepsy (JME, n=215) and Childhood Absence Epilepsy (CAE, n=175)]. Sequence analysis was performed in 85 IGE and 42 PPR cases and 44 controls. RESULTS Nominally significant associations were detected between IGE and seven GRM4 SNPs (with P-values ranging from 0.037 to 0.0036), between JME and five SNPs (P=0.042-0.0106), and between CAE and two SNPs (P=0.0466-0.0021). Four novel SNPs were identified by sequence analysis. CONCLUSIONS Our association findings support the hypothesis that GRM4 sequence variants might confer low-risk effects to the etiology of IGE. A minor pathogenetic contribution of the examined variants is possible. These exploratory findings warrant further replication analyses.
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Helbig KL, Bernhardt BA, Conway LJ, Valverde KD, Helbig I, Sperling MR. Genetic risk perception and reproductive decision making among people with epilepsy. Epilepsia 2010; 51:1874-7. [DOI: 10.1111/j.1528-1167.2009.02507.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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de Kovel CGF, Trucks H, Helbig I, Mefford HC, Baker C, Leu C, Kluck C, Muhle H, von Spiczak S, Ostertag P, Obermeier T, Kleefuss-Lie AA, Hallmann K, Steffens M, Gaus V, Klein KM, Hamer HM, Rosenow F, Brilstra EH, Trenité DKN, Swinkels MEM, Weber YG, Unterberger I, Zimprich F, Urak L, Feucht M, Fuchs K, Møller RS, Hjalgrim H, De Jonghe P, Suls A, Rückert IM, Wichmann HE, Franke A, Schreiber S, Nürnberg P, Elger CE, Lerche H, Stephani U, Koeleman BPC, Lindhout D, Eichler EE, Sander T. Recurrent microdeletions at 15q11.2 and 16p13.11 predispose to idiopathic generalized epilepsies. Brain 2009; 133:23-32. [PMID: 19843651 DOI: 10.1093/brain/awp262] [Citation(s) in RCA: 342] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Idiopathic generalized epilepsies account for 30% of all epilepsies. Despite a predominant genetic aetiology, the genetic factors predisposing to idiopathic generalized epilepsies remain elusive. Studies of structural genomic variations have revealed a significant excess of recurrent microdeletions at 1q21.1, 15q11.2, 15q13.3, 16p11.2, 16p13.11 and 22q11.2 in various neuropsychiatric disorders including autism, intellectual disability and schizophrenia. Microdeletions at 15q13.3 have recently been shown to constitute a strong genetic risk factor for common idiopathic generalized epilepsy syndromes, implicating that other recurrent microdeletions may also be involved in epileptogenesis. This study aimed to investigate the impact of five microdeletions at the genomic hotspot regions 1q21.1, 15q11.2, 16p11.2, 16p13.11 and 22q11.2 on the genetic risk to common idiopathic generalized epilepsy syndromes. The candidate microdeletions were assessed by high-density single nucleotide polymorphism arrays in 1234 patients with idiopathic generalized epilepsy from North-western Europe and 3022 controls from the German population. Microdeletions were validated by quantitative polymerase chain reaction and their breakpoints refined by array comparative genomic hybridization. In total, 22 patients with idiopathic generalized epilepsy (1.8%) carried one of the five novel microdeletions compared with nine controls (0.3%) (odds ratio = 6.1; 95% confidence interval 2.8-13.2; chi(2) = 26.7; 1 degree of freedom; P = 2.4 x 10(-7)). Microdeletions were observed at 1q21.1 [Idiopathic generalized epilepsy (IGE)/control: 1/1], 15q11.2 (IGE/control: 12/6), 16p11.2 IGE/control: 1/0, 16p13.11 (IGE/control: 6/2) and 22q11.2 (IGE/control: 2/0). Significant associations with IGEs were found for the microdeletions at 15q11.2 (odds ratio = 4.9; 95% confidence interval 1.8-13.2; P = 4.2 x 10(-4)) and 16p13.11 (odds ratio = 7.4; 95% confidence interval 1.3-74.7; P = 0.009). Including nine patients with idiopathic generalized epilepsy in this cohort with known 15q13.3 microdeletions (IGE/control: 9/0), parental transmission could be examined in 14 families. While 10 microdeletions were inherited (seven maternal and three paternal transmissions), four microdeletions occurred de novo at 15q13.3 (n = 1), 16p13.11 (n = 2) and 22q11.2 (n = 1). Eight of the transmitting parents were clinically unaffected, suggesting that the microdeletion itself is not sufficient to cause the epilepsy phenotype. Although the microdeletions investigated are individually rare (<1%) in patients with idiopathic generalized epilepsy, they collectively seem to account for a significant fraction of the genetic variance in common idiopathic generalized epilepsy syndromes. The present results indicate an involvement of microdeletions at 15q11.2 and 16p13.11 in epileptogenesis and strengthen the evidence that recurrent microdeletions at 15q11.2, 15q13.3 and 16p13.11 confer a pleiotropic susceptibility effect to a broad range of neuropsychiatric disorders.
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Dibbens LM, Mullen S, Helbig I, Mefford HC, Bayly MA, Bellows S, Leu C, Trucks H, Obermeier T, Wittig M, Franke A, Caglayan H, Yapici Z, Sander T, Eichler EE, Scheffer IE, Mulley JC, Berkovic SF. Familial and sporadic 15q13.3 microdeletions in idiopathic generalized epilepsy: precedent for disorders with complex inheritance. Hum Mol Genet 2009; 18:3626-31. [PMID: 19592580 DOI: 10.1093/hmg/ddp311] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Microdeletion at chromosomal position 15q13.3 has been described in intellectual disability, autism spectrum disorders, schizophrenia and recently in idiopathic generalized epilepsy (IGE). Using independent IGE cohorts, we first aimed to confirm the association of 15q13.3 deletions and IGE. We then set out to determine the relative occurrence of sporadic and familial cases and to examine the likelihood of having seizures for individuals with the microdeletion in familial cases. The 15q13.3 microdeletion was identified in 7 of 539 (1.3%) unrelated cases of IGE using quantitative PCR or SNP arrays and confirmed by array comparative genomic hybridization analysis using probes specific to the 15q13.3 region. The inheritance of this lesion was tracked using family studies. Of the seven microdeletions identified in probands, three were de novo, two were transmitted from an unaffected parent and in two cases the parents were unavailable. Non-penetrance of the microdeletion was identified in 4/7 pedigrees and three pedigrees included other family members with IGE who lacked the 15q13.3 deletion. The odds ratio is 68 (95% confidence interval 29-181), indicating a pathogenic lesion predisposing to epilepsy with complex inheritance and incomplete penetrance for the IGE component of the phenotype in multiplex families.
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Mullen SA, Crompton DE, Carney PW, Helbig I, Berkovic SF. A neurologist's guide to genome-wide association studies. Neurology 2009; 72:558-65. [PMID: 19204266 DOI: 10.1212/01.wnl.0000341942.29513.bd] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Genome-wide association studies are utilized for gene discovery in common diseases. Genotypes of large groups of unrelated patients are compared to controls. This has become feasible due to the recent technical advances in genomics and convincing positive results are now regularly being published. This review is an accessible introduction to the genetic and technical knowledge needed to interpret such studies. Genome-wide association studies are being applied to many neurologic diseases. Here we use idiopathic generalized epilepsy as an example to highlight the phenotyping, sample size, and statistical issues that must be addressed in such studies. These studies are likely to transform our understanding of complex neurologic diseases in the next few years.
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Helbig I, Mefford HC, Sharp AJ, Guipponi M, Fichera M, Franke A, Muhle H, de Kovel C, Baker C, von Spiczak S, Kron KL, Steinich I, Kleefuss-Lie AA, Leu C, Gaus V, Schmitz B, Klein KM, Reif PS, Rosenow F, Weber Y, Lerche H, Zimprich F, Urak L, Fuchs K, Feucht M, Genton P, Thomas P, Visscher F, de Haan GJ, Møller RS, Hjalgrim H, Luciano D, Wittig M, Nothnagel M, Elger CE, Nürnberg P, Romano C, Malafosse A, Koeleman BPC, Lindhout D, Stephani U, Schreiber S, Eichler EE, Sander T. 15q13.3 microdeletions increase risk of idiopathic generalized epilepsy. Nat Genet 2009; 41:160-2. [PMID: 19136953 DOI: 10.1038/ng.292] [Citation(s) in RCA: 408] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 10/27/2008] [Indexed: 11/09/2022]
Abstract
We identified 15q13.3 microdeletions encompassing the CHRNA7 gene in 12 of 1,223 individuals with idiopathic generalized epilepsy (IGE), which were not detected in 3,699 controls (joint P = 5.32 x 10(-8)). Most deletion carriers showed common IGE syndromes without other features previously associated with 15q13.3 microdeletions, such as intellectual disability, autism or schizophrenia. Our results indicate that 15q13.3 microdeletions constitute the most prevalent risk factor for common epilepsies identified to date.
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