Publications by authors named "Line H G Larsen"

15 Publications

  • Page 1 of 1

Next Generation Sequencing in Pediatric Epilepsy Using Customized Panels: Size Matters.

Neuropediatrics 2021 04 21;52(2):92-97. Epub 2020 Oct 21.

Division of Pediatric Neurology, Developmental Medicine and Social Pediatrics Department of Pediatrics, Ludwig-Maximilians University of Munich, Dr. von Hauner Children's Hospital, Munich, Germany.

Introduction: Next generation sequencing (NGS) with customized gene panels is a helpful tool to identify monogenic epilepsy syndromes. The number of genes tested within a customized panel may vary greatly. The aim of the present study was to compare the diagnostic yield of small (<25 kb) and large (>25 kb) customized epilepsy panels.

Methods: This retrospective cohort study investigated data of 190 patients of 18 years or younger, with the diagnosis of an epilepsy of unknown etiology who underwent NGS using customized gene panels. Small (<25 kb) and large (>25 kb) panels were compared regarding the distribution of benign/likely benign and pathogenic/likely pathogenic variants and variants of unclear significance. In addition, differences of the diagnostic yield with respect to epilepsy severity, i.e., developmental and epileptic encephalopathy [DEE] vs. non-DEE, were analyzed.

Results: The diagnostic yield defined as pathogenic or likely pathogenic variants in large panels was significantly increased (29% [ = 14/48] vs. 13% [ = 18/142],  = 0.0198) compared with smaller panels. In non-DEE patients the increase of the diagnostic yield in large panels was significant(35%  = 6/17 vs. 13%  = 12/94,  = 0.0378), which was not true for DEE patients.

Discussion: This study indicates that large panels are superior for pediatric patients with epilepsy forms without encephalopathy (non-DEE). For patients suffering from DEE small panels of a maximum of 10 genes seem to be sufficient. The proportion of unclear findings increases with rising panel sizes.

Conclusion: Customized epilepsy panels of >25 kb compared with smaller panels show a significant higher diagnostic yield in patients with epilepsy especially in non-DEE patients.
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http://dx.doi.org/10.1055/s-0040-1712488DOI Listing
April 2021

Utility of genetic testing for therapeutic decision-making in adults with epilepsy.

Epilepsia 2020 06 19;61(6):1234-1239. Epub 2020 May 19.

Department of Epilepsy Genetics and Personalized Treatment, Danish Epilepsy Center, Dianalund, Denmark.

Objective: Genetic testing has become a routine part of the diagnostic workup in children with early onset epilepsies. In the present study, we sought to investigate a cohort of adult patients with epilepsy, to determinate the diagnostic yield and explore the gain of personalized treatment approaches in adult patients.

Methods: Two hundred patients (age span = 18-80 years) referred for diagnostic gene panel testing at the Danish Epilepsy Center were included. The vast majority (91%) suffered from comorbid intellectual disability. The medical records of genetically diagnosed patients were mined for data on epilepsy syndrome, cognition, treatment changes, and seizure outcome following the genetic diagnosis.

Results: We found a genetic diagnosis in 46 of 200 (23%) patients. SCN1A, KCNT1, and STXBP1 accounted for the greatest number of positive findings (48%). More rare genetic findings included SLC2A1, ATP6A1V, HNRNPU, MEF2C, and IRF2BPL. Gene-specific treatment changes were initiated in 11 of 46 (17%) patients (one with SLC2A1, 10 with SCN1A) following the genetic diagnosis. Ten patients improved, with seizure reduction and/or increased alertness and general well-being.

Significance: With this study, we show that routine diagnostic testing is highly relevant in adults with epilepsy. The diagnostic yield is similar to previously reported pediatric cohorts, and the genetic findings can be useful for therapeutic decision-making, which may lead to better seizure control, ultimately improving quality of life.
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http://dx.doi.org/10.1111/epi.16533DOI Listing
June 2020

Impact on Clinical Decision Making of Next-Generation Sequencing in Pediatric Epilepsy in a Tertiary Epilepsy Referral Center.

Clin EEG Neurosci 2020 Jan 25;51(1):61-69. Epub 2019 Sep 25.

Department of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Dr von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany.

. Next-generation sequencing (NGS) describes new powerful techniques of nucleic acid analysis, which allow not only disease gene identification diagnostics but also applications for transcriptome/methylation analysis and meta-genomics. NGS helps identify many monogenic epilepsy syndromes. Pediatric epilepsy patients can be tested using NGS epilepsy panels to diagnose them, thereby influencing treatment choices. The primary objective of this study was to evaluate the impact of genetic testing on clinical decision making in pediatric epilepsy patients. . We completed a single-center retrospective cohort study of 91 patients (43 male) aged 19 years or less undergoing NGS with epilepsy panels differing in size ranging from 5 to 434 genes from October 2013 to September 2017. . During a mean time of 3.6 years between symptom onset and genetic testing, subjects most frequently showed epileptic encephalopathy (40%), focal epilepsy (33%), and generalized epilepsy (18%). In 16 patients (18% of the study population), "pathogenic" or "likely pathogenic" results according to ACMG criteria were found. Ten of the 16 patients (63%) experienced changes in clinical management regarding their medication and avoidance of further diagnostic evaluation, that is, presurgical evaluation. . NGS epilepsy panels contribute to the diagnosis of pediatric epilepsy patients and may change their clinical management with regard to both preventing unnecessary and potentially harmful diagnostic procedures and management. Thus, the present data support the early implementation in order to adopt clinical management in selected cases and prevent further invasive investigations. Given the relatively small sample size and heterogeneous panels a larger prospective study with more homogeneous panels would be helpful to further determine the impact of NGS on clinical decision making.
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http://dx.doi.org/10.1177/1550059419876518DOI Listing
January 2020

Parental mosaicism in epilepsies due to alleged de novo variants.

Epilepsia 2019 06 11;60(6):e63-e66. Epub 2019 May 11.

Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany.

Severe early onset epilepsies are often caused by de novo pathogenic variants. Few studies have reported the frequency of somatic mosaicism in parents of children with severe epileptic encephalopathies. Here we aim to investigate the frequency of mosaicism in the parents of children with epilepsy caused by alleged de novo variants. We tested parental genomic DNA derived from different tissues for 75 cases using targeted next-generation sequencing. Five parents (6.6%) showed mosaicism at minor allele frequencies of 0.8%-29% for the pathogenic variant detected in their offspring. Parental mosaicism was observed in the following genes: SCN1A, SCN2A, SCN8A, and STXBP1. One of the identified parents had epilepsy himself. Our results show that de novo events can occur already in parental tissue and in some cases can be detected in peripheral blood. Consequently, parents affected by low-grade mosaicism are faced with an increased recurrence risk for transmitting the pathogenic variant, compared to the overall recurrence risk for a second affected child estimated at approximately 1%. However, testing for parental somatic mosaicism will help identifying those parents who truly are at higher risk and will significantly improve genetic counseling in the respective families.
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http://dx.doi.org/10.1111/epi.15187DOI Listing
June 2019

PIGT-CDG, a disorder of the glycosylphosphatidylinositol anchor: description of 13 novel patients and expansion of the clinical characteristics.

Genet Med 2019 10 12;21(10):2216-2223. Epub 2019 Apr 12.

Danish Epilepsy Centre, Dianalund, Denmark.

Purpose: To provide a detailed electroclinical description and expand the phenotype of PIGT-CDG, to perform genotype-phenotype correlation, and to investigate the onset and severity of the epilepsy associated with the different genetic subtypes of this rare disorder. Furthermore, to use computer-assisted facial gestalt analysis in PIGT-CDG and to the compare findings with other glycosylphosphatidylinositol (GPI) anchor deficiencies.

Methods: We evaluated 13 children from eight unrelated families with homozygous or compound heterozygous pathogenic variants in PIGT.

Results: All patients had hypotonia, severe developmental delay, and epilepsy. Epilepsy onset ranged from first day of life to two years of age. Severity of the seizure disorder varied from treatable seizures to severe neonatal onset epileptic encephalopathies. The facial gestalt of patients resembled that of previously published PIGT patients as they were closest to the center of the PIGT cluster in the clinical face phenotype space and were distinguishable from other gene-specific phenotypes.

Conclusion: We expand our knowledge of PIGT. Our cases reaffirm that the use of genetic testing is essential for diagnosis in this group of disorders. Finally, we show that computer-assisted facial gestalt analysis accurately assigned PIGT cases to the multiple congenital anomalies-hypotonia-seizures syndrome phenotypic series advocating the additional use of next-generation phenotyping technology.
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http://dx.doi.org/10.1038/s41436-019-0512-3DOI Listing
October 2019

Mesial Temporal Sclerosis in SCN1A-Related Epilepsy: Two Long-Term EEG Case Studies.

Clin EEG Neurosci 2019 Jul 17;50(4):267-272. Epub 2018 Aug 17.

1 Department of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Dr von Haunersches Children's Hospital, University of Munich, Munich, Germany.

Patients with temporal lobe epilepsy (TLE) due to mesial temporal sclerosis (MTS) are eligible candidates for resective epilepsy surgery. We report on 2 male patients aged 4 years with suspected TLE due to MTS who were referred for presurgical evaluation. Both patients came to medical attention within the first year of life suffering from febrile status epileptici and subsequent unprovoked seizures. The following years, moderate developmental delay was present. High-resolution magnetic resonance imaging confirmed hippocampal sclerosis. Continuous EEG video monitoring revealed seizure patterns contralateral to the MTS in both patients. Genetic analysis was performed as both the clinical presentation of the patients and EEG video monitoring findings were not consistent with the presence of the hippocampal sclerosis alone and revealed de novo mutations within exon of the SCN1A gene. Resective surgical strategies were omitted due to the genetic findings. In conclusion, both patients suffered from a dual pathology syndrome with ( a) TLE related to MTS resulting most likely from recurrent febrile status in early childhood and ( b) Dravet syndrome, which is most likely the cause of the febrile convulsions leading to the MTS in these 2 patients.
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http://dx.doi.org/10.1177/1550059418794347DOI Listing
July 2019

Incorporating epilepsy genetics into clinical practice: a 360°evaluation.

NPJ Genom Med 2018 10;3:13. Epub 2018 May 10.

1King's College Hospital, London, UK.

We evaluated a new epilepsy genetic diagnostic and counseling service covering a UK population of 3.5 million. We calculated diagnostic yield, estimated clinical impact, and surveyed referring clinicians and families. We costed alternative investigational pathways for neonatal onset epilepsy. Patients with epilepsy of unknown aetiology onset < 2 years; treatment resistant epilepsy; or familial epilepsy were referred for counseling and testing. We developed NGS panels, performing clinical interpretation with a multidisciplinary team. We held an educational workshop for paediatricians and nurses. We sent questionnaires to referring paediatricians and families. We analysed investigation costs for 16 neonatal epilepsy patients. Of 96 patients, a genetic diagnosis was made in 34% of patients with seizure onset < 2 years, and 4% > 2 years, with turnaround time of 21 days. Pathogenic variants were seen in , , and . Clinician prediction was poor. Clinicians and families rated the service highly. In neonates, the cost of investigations could be reduced from £9362 to £2838 by performing gene panel earlier and the median diagnostic delay of 3.43 years reduced to 21 days. Panel testing for epilepsy has a high yield among children with onset < 2 years, and an appreciable clinical and financial impact. Parallel gene testing supersedes single gene testing in most early onset cases that do not show a clear genotype-phenotype correlation. Clinical interpretation of laboratory results, and in-depth discussion of implications for patients and their families, necessitate multidisciplinary input and skilled genetic counseling.
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http://dx.doi.org/10.1038/s41525-018-0052-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5945675PMC
May 2018

Mutations in GABRB3: From febrile seizures to epileptic encephalopathies.

Neurology 2017 01 4;88(5):483-492. Epub 2017 Jan 4.

From the Danish Epilepsy Centre (R.S.M., K.M.J., M.N.), Dianalund; Institute for Regional Health Services (R.S.M., K.M.J., M.N.), University of Southern Denmark, Odense; Department of Neurology and Epileptology (T.V.W., S.V., H.L., S.M.), Hertie Institute for Clinical Brain Research, and Department of Neurosurgery (T.V.W.), University of Tübingen; Department of Neuropediatrics (I.H., M.P., S.v.S., H.M.), University Medical Center Schleswig-Holstein, Kiel, Germany; Division of Neurology (I.H., S.H., H.D.), The Children's Hospital of Philadelphia, PA; Neuroscience Department (C.M., R.G.), Children's Hospital Anna Meyer-University of Florence, Italy; Department of Genetics (E.H.B., M.S., K.L.v.G.), University Medical Center Utrecht, the Netherlands; Department of Neurology and Neurorehabilitation (U.V., I.T., T.T.), Children's Clinic of Tartu University Hospital, Estonia; Department of Pediatric Neurology and Epilepsy Center (I.B.), LMU Munich, Germany; Department of Pediatrics (I.T., T.T.), University of Tartu; Tallinn Children's Hospital (I.T.), Tallinn, Estonia; Clinic for Neuropediatrics and Neurorehabilitation (G.K., C.B., H.H.), Epilepsy Center for Children and Adolescents, Schön Klinik Vogtareuth, Germany; Paracelsus Medical Private University (G.K.), Salzburg, Austria; Neuropeadiatric Department (L.L.F.), Hospices Civils de Lyon; Department of Genetics (G.L., N.C.), Lyon University Hospitals; Claude Bernard Lyon I University (G.L., N.C.); Lyon Neuroscience Research Centre (G.L., N.C.), CNRS UMR5292, INSERM U1028; Epilepsy, Sleep and Pediatric Neurophysiology Department (J.d.B.), Lyon University Hospitals, France; Clinic for Pediatric Neurology (S.B.), Pediatric Department, University Hospital, Herlev, Denmark; Kleinwachau (N.H.), Sächsisches Epilepsiezentrum Radeberg, Dresden; Department of Neuropediatrics/Epilepsy Center (J.J.), University Medical Center Freiburg; Department of General Paediatrics (S.S.), Division of Child Neurology and Inherited Metabolic Diseases, Centre for Paediatrics and Adolescent Medicine, University Hospital Heidelberg; Department of Women and Child Health (S.S.), Hospital for Children and Adolescents, University of Leipzig Hospitals and Clinics, Germany; Department of Pediatrics (C.T.M., H.C.M.), Division of Genetic Medicine, University of Washington, Seattle; Amplexa Genetics (L.H.G.L., H.A.D.), Odense, Denmark; Northern German Epilepsy Center for Children and Adolescents (S.v.S.), Schwentinental-Raisdorf, Germany; Wilhelm Johannsen Centre for Functional Genome Research (Y.M., N.T.), Department of Cellular and Molecular Medicine, University of Copenhagen; Danish Epilepsy Center (G.R.), Filadelfia/University of Copenhagen, Denmark; Department of Diagnostics (J.R.L.), Institute of Human Genetics, University of Leipzig; and Svt. Luka's Institute of Child Neurology and Epilepsy (K.M.), Moscow, Russia. Dr Maljevic is currently at the Florey Institute of Neuroscience and Mental Health, Melbourne, Australia.

Objective: To examine the role of mutations in GABRB3 encoding the β subunit of the GABA receptor in individual patients with epilepsy with regard to causality, the spectrum of genetic variants, their pathophysiology, and associated phenotypes.

Methods: We performed massive parallel sequencing of GABRB3 in 416 patients with a range of epileptic encephalopathies and childhood-onset epilepsies and recruited additional patients with epilepsy with GABRB3 mutations from other research and diagnostic programs.

Results: We identified 22 patients with heterozygous mutations in GABRB3, including 3 probands from multiplex families. The phenotypic spectrum of the mutation carriers ranged from simple febrile seizures, genetic epilepsies with febrile seizures plus, and epilepsy with myoclonic-atonic seizures to West syndrome and other types of severe, early-onset epileptic encephalopathies. Electrophysiologic analysis of 7 mutations in Xenopus laevis oocytes, using coexpression of wild-type or mutant β, together with α and γ subunits and an automated 2-microelectrode voltage-clamp system, revealed reduced GABA-induced current amplitudes or GABA sensitivity for 5 of 7 mutations.

Conclusions: Our results indicate that GABRB3 mutations are associated with a broad phenotypic spectrum of epilepsies and that reduced receptor function causing GABAergic disinhibition represents the relevant disease mechanism.
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http://dx.doi.org/10.1212/WNL.0000000000003565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5278942PMC
January 2017

Germline and somatic mutations in the gene in focal cortical dysplasia and epilepsy.

Neurol Genet 2016 Dec 31;2(6):e118. Epub 2016 Oct 31.

The Danish Epilepsy Centre Filadelfia (R.S.M., G.R.), Dianalund, Denmark; Institute for Regional Health Services (R.S.M.), University of Southern Denmark, Odense; Sorbonne Universités (S.W., E.M., V.L., E.L., S.B.), UPMC Univ Paris 06 UMR S 1127, Inserm U1127, CNRS UMR 7225, AP-HP, Institut du cerveau et la moelle (ICM)-Hôpital Pitié-Salpêtrière, Paris, France; Epilepsy Unit (S.W., V.L.), AP-HP Groupe hospitalier Pitié-Salpêtrière, Paris, France; Neurogenetics Group (S.W.), VIB-Department of Molecular Genetics; Laboratory of Neurogenetics (S.W.), Institute Born-Bunge, University of Antwerp, Belgium; Department of Neurology (S.W.), University Hospital Antwerp, Belgium; Department of Pediatric Neurosurgery (M.C., S.F.-S., G.D.), Fondation Rothschild, Paris, France; Université Paris Sorbonne Cité (V.T.), INSERM UMR-S1147 MEPPOT, CNRS SNC5014, Centre Universitaire des Saints-Pères, Paris, France; Department of Neurology (E.M.B.), University of Alabama at Birmingham; HudsonAlpha Institute for Biotechnology (S.M.H., J.W.P., K.M.B., G.M.C.), Huntsville, AL; Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories (D.M., V.C., R.G.), Neuroscience Department, A Meyer Children's Hospital, University of Florence, Florence, Italy; Genosplice (P.d.l.G.), Institut du Cerveau et de la Moelle épinière, ICM, Paris, France; Amplexa Genetics (L.H.G.L.), Odense, Denmark; Department of Genetics and Cytogenetics (E.L., S.B.), AP-HP Groupe hospitalier Pitié-Salpêtrière, Paris, France; and University of Copenhagen (G.R.), Denmark.

Objective: To assess the prevalence of somatic mutations in focal cortical dysplasia (FCD) and of germline mutations in a broad range of epilepsies.

Methods: We collected 20 blood-brain paired samples from patients with FCD and searched for somatic variants using deep-targeted gene panel sequencing. Germline mutations in were assessed in a French research cohort of 93 probands with focal epilepsies and in a diagnostic Danish cohort of 245 patients with a broad range of epilepsies. Data sharing among collaborators allowed us to ascertain additional germline variants in .

Results: We detected recurrent somatic variants (p.Ser2215Phe, p.Ser2215Tyr, and p.Leu1460Pro) in the gene in 37% of participants with FCD II and showed histologic evidence for activation of the mTORC1 signaling cascade in brain tissue. We further identified 5 novel de novo germline missense variants in 6 individuals with a variable phenotype from focal, and less frequently generalized, epilepsies without brain malformations, to macrocephaly, with or without moderate intellectual disability. In addition, an inherited variant was found in a mother-daughter pair with nonlesional autosomal dominant nocturnal frontal lobe epilepsy.

Conclusions: Our data illustrate the increasingly important role of somatic mutations of the gene in FCD and germline mutations in the pathogenesis of focal epilepsy syndromes with and without brain malformation or macrocephaly.
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http://dx.doi.org/10.1212/NXG.0000000000000118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5089441PMC
December 2016

Gene Panel Testing in Epileptic Encephalopathies and Familial Epilepsies.

Mol Syndromol 2016 Sep 20;7(4):210-219. Epub 2016 Aug 20.

Danish Epilepsy Centre, Filadelfia, Dianalund, Denmark.

In recent years, several genes have been causally associated with epilepsy. However, making a genetic diagnosis in a patient can still be difficult, since extensive phenotypic and genetic heterogeneity has been observed in many monogenic epilepsies. This study aimed to analyze the genetic basis of a wide spectrum of epilepsies with age of onset spanning from the neonatal period to adulthood. A gene panel targeting 46 epilepsy genes was used on a cohort of 216 patients consecutively referred for panel testing. The patients had a range of different epilepsies from benign neonatal seizures to epileptic encephalopathies (EEs). Potentially causative variants were evaluated by literature and database searches, submitted to bioinformatic prediction algorithms, and validated by Sanger sequencing. If possible, parents were included for segregation analysis. We identified a presumed disease-causing variant in 49 (23%) of the 216 patients. The variants were found in 19 different genes including and . Patients with neonatal-onset epilepsies had the highest rate of positive findings (57%). The overall yield for patients with EEs was 32%, compared to 17% among patients with generalized epilepsies and 16% in patients with focal or multifocal epilepsies. By the use of a gene panel consisting of 46 epilepsy genes, we were able to find a disease-causing genetic variation in 23% of the analyzed patients. The highest yield was found among patients with neonatal-onset epilepsies and EEs.
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http://dx.doi.org/10.1159/000448369DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5073625PMC
September 2016

Phenotypic spectrum of GABRA1: From generalized epilepsies to severe epileptic encephalopathies.

Neurology 2016 09 12;87(11):1140-51. Epub 2016 Aug 12.

Authors' affiliations are listed at the end of the article.

Objective: To delineate phenotypic heterogeneity, we describe the clinical features of a cohort of patients with GABRA1 gene mutations.

Methods: Patients with GABRA1 mutations were ascertained through an international collaboration. Clinical, EEG, and genetic data were collected. Functional analysis of 4 selected mutations was performed using the Xenopus laevis oocyte expression system.

Results: The study included 16 novel probands and 3 additional family members with a disease-causing mutation in the GABRA1 gene. The phenotypic spectrum varied from unspecified epilepsy (1), juvenile myoclonic epilepsy (2), photosensitive idiopathic generalized epilepsy (1), and generalized epilepsy with febrile seizures plus (1) to severe epileptic encephalopathies (11). In the epileptic encephalopathy group, the patients had seizures beginning between the first day of life and 15 months, with a mean of 7 months. Predominant seizure types in all patients were tonic-clonic in 9 participants (56%) and myoclonic seizures in 5 (31%). EEG showed a generalized photoparoxysmal response in 6 patients (37%). Four selected mutations studied functionally revealed a loss of function, without a clear genotype-phenotype correlation.

Conclusions: GABRA1 mutations make a significant contribution to the genetic etiology of both benign and severe epilepsy syndromes. Myoclonic and tonic-clonic seizures with pathologic response to photic stimulation are common and shared features in both mild and severe phenotypes.
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http://dx.doi.org/10.1212/WNL.0000000000003087DOI Listing
September 2016

Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation.

Ann Neurol 2016 Mar 13;79(3):428-36. Epub 2016 Feb 13.

Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.

Objective: Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination-known as infantile convulsions and paroxysmal choreoathetosis (ICCA)-are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

Methods: We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

Results: In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic-clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or "shivering" attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

Interpretation: Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical-genetic spectrum of combined epileptic and dyskinetic syndromes.
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http://dx.doi.org/10.1002/ana.24580DOI Listing
March 2016

Mutations in KCNT1 cause a spectrum of focal epilepsies.

Epilepsia 2015 Sep 30;56(9):e114-20. Epub 2015 Jun 30.

Department of Pediatrics, Aarhus University Hospital, Aarhus, Denmark.

Autosomal dominant mutations in the sodium-gated potassium channel subunit gene KCNT1 have been associated with two distinct seizure syndromes, nocturnal frontal lobe epilepsy (NFLE) and malignant migrating focal seizures of infancy (MMFSI). To further explore the phenotypic spectrum associated with KCNT1, we examined individuals affected with focal epilepsy or an epileptic encephalopathy for mutations in the gene. We identified KCNT1 mutations in 12 previously unreported patients with focal epilepsy, multifocal epilepsy, cardiac arrhythmia, and in a family with sudden unexpected death in epilepsy (SUDEP), in addition to patients with NFLE and MMFSI. In contrast to the 100% penetrance so far reported for KCNT1 mutations, we observed incomplete penetrance. It is notable that we report that the one KCNT1 mutation, p.Arg398Gln, can lead to either of the two distinct phenotypes, ADNFLE or MMFSI, even within the same family. This indicates that genotype-phenotype relationships for KCNT1 mutations are not straightforward. We demonstrate that KCNT1 mutations are highly pleiotropic and are associated with phenotypes other than ADNFLE and MMFSI. KCNT1 mutations are now associated with Ohtahara syndrome, MMFSI, and nocturnal focal epilepsy. They may also be associated with multifocal epilepsy and cardiac disturbances.
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http://dx.doi.org/10.1111/epi.13071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5915334PMC
September 2015

Identification and characterization of the Thermus thermophilus 5-methylcytidine (m5C) methyltransferase modifying 23 S ribosomal RNA (rRNA) base C1942.

J Biol Chem 2012 Aug 18;287(33):27593-600. Epub 2012 Jun 18.

Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark.

Methylation of cytidines at carbon-5 is a common posttranscriptional RNA modification encountered across all domains of life. Here, we characterize the modifications of C1942 and C1962 in Thermus thermophilus 23 S rRNA as 5-methylcytidines (m(5)C) and identify the two associated methyltransferases. The methyltransferase modifying C1942, named RlmO, has not been characterized previously. RlmO modifies naked 23 S rRNA, but not the assembled 50 S subunit or 70 S ribosomes. The x-ray crystal structure of this enzyme in complex with the S-adenosyl-l-methionine cofactor at 1.7 Å resolution confirms that RlmO is structurally related to other m(5)C rRNA methyltransferases. Key residues in the active site are located similar to the further distant 5-methyluridine methyltransferase RlmD, suggestive of a similar enzymatic mechanism. RlmO homologues are primarily found in mesophilic bacteria related to T. thermophilus. In accordance, we find that growth of the T. thermophilus strain with an inactivated C1942 methyltransferase gene is not compromised at non-optimal temperatures.
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http://dx.doi.org/10.1074/jbc.M112.376160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3431712PMC
August 2012

Multi-site-specific 16S rRNA methyltransferase RsmF from Thermus thermophilus.

RNA 2010 Aug 17;16(8):1584-96. Epub 2010 Jun 17.

Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.

Cells devote a significant effort toward the production of multiple modified nucleotides in rRNAs, which fine tune the ribosome function. Here, we report that two methyltransferases, RsmB and RsmF, are responsible for all four 5-methylcytidine (m(5)C) modifications in 16S rRNA of Thermus thermophilus. Like Escherichia coli RsmB, T. thermophilus RsmB produces m(5)C967. In contrast to E. coli RsmF, which introduces a single m(5)C1407 modification, T. thermophilus RsmF modifies three positions, generating m(5)C1400 and m(5)C1404 in addition to m(5)C1407. These three residues are clustered near the decoding site of the ribosome, but are situated in distinct structural contexts, suggesting a requirement for flexibility in the RsmF active site that is absent from the E. coli enzyme. Two of these residues, C1400 and C1404, are sufficiently buried in the mature ribosome structure so as to require extensive unfolding of the rRNA to be accessible to RsmF. In vitro, T. thermophilus RsmF methylates C1400, C1404, and C1407 in a 30S subunit substrate, but only C1400 and C1404 when naked 16S rRNA is the substrate. The multispecificity of T. thermophilus RsmF is potentially explained by three crystal structures of the enzyme in a complex with cofactor S-adenosyl-methionine at up to 1.3 A resolution. In addition to confirming the overall structural similarity to E. coli RsmF, these structures also reveal that key segments in the active site are likely to be dynamic in solution, thereby expanding substrate recognition by T. thermophilus RsmF.
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http://dx.doi.org/10.1261/rna.2088310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2905757PMC
August 2010
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