Publications by authors named "Hiltrud Muhle"

91 Publications

Efficacy, tolerability, and retention of fenfluramine for the treatment of seizures in patients with Dravet syndrome: Compassionate use program in Germany.

Epilepsia 2021 Aug 10. Epub 2021 Aug 10.

Epilepsy Center Frankfurt Rhine-Main, Center of Neurology and Neurosurgery, Goethe University Frankfurt, Frankfurt am Main, Germany.

Objective: Dravet syndrome (DS) is a rare but severe drug-resistant epilepsy. Before the approval of fenfluramine (FFA) for the treatment of seizures in DS, patients in Germany could receive treatment under a compassionate use program (CUP).

Methods: We conducted a multicenter, retrospective, observational study to describe the efficacy, tolerability, and retention of FFA within the CUP. Patients received add-on therapy with oral FFA gradually titrated to a target dose between .13 and .7 mg/kg/day.

Results: Overall, 78 patients with DS (median age = 8.0 years, range = 2.1-46.0; 53% female, median concomitant antiseizure medications [ASMs] = 3) were treated with FFA for a median duration of 255.5 days (range = 31-572). Responder rates (a ≥50% reduction; n = 78) and seizure-freedom rates at 3 months were 68% and 14% for total seizures, respectively, and 67% and 23% for generalized tonic-clonic seizures. Responder rates were consistent at 6 and 12 months (n = 66 and n = 43, respectively). Median seizure days per month significantly decreased from 10.0 (range = .5-30) to 3.0 (range = 0-30) in the 3-month period before and after FFA treatment (p < .001). Significantly fewer patients reported at least one episode of status epilepticus (28% vs. 14% patients before and after FFA initiation, p = .005). During FFA treatment, 35 (45%) patients were able to discontinue a concomitant ASM. At the last follow-up date, 66 (85%) patients remained on treatment with FFA. The most common adverse events were somnolence (36%), decreased appetite (22%), and ataxia (8%). Forty-eight (62%) patients were reported as having a meaningful global clinical improvement.

Significance: In a large cohort of patients, FFA demonstrated efficacy across a range of outcomes including clinically significant reductions in convulsive seizures, and was well tolerated, providing valuable information for real-world practice.
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http://dx.doi.org/10.1111/epi.17034DOI Listing
August 2021

Efficacy, Retention and Tolerability of Everolimus in Patients with Tuberous Sclerosis Complex: A Survey-Based Study on Patients' Perspectives.

CNS Drugs 2021 Jul 17. Epub 2021 Jul 17.

Division of Nephrology, Medizinische Klinik und Poliklinik IV, Klinikum der LMU München - Innenstadt, München, Germany.

Background: The approval of everolimus (EVE) for the treatment of angiomyolipoma (2013), subependymal giant cell astrocytoma (2013) and drug-refractory epilepsy (2017) in patients with tuberous sclerosis complex (TSC) represents the first disease-modifying treatment option available for this rare and complex genetic disorder.

Objective: The objective of this study was to analyse the use, efficacy, tolerability and treatment retention of EVE in patients with TSC in Germany from the patient's perspective.

Methods: A structured cross-age survey was conducted at 26 specialised TSC centres in Germany and by the German TSC patient advocacy group between February and July 2019, enrolling children, adolescents and adult patients with TSC.

Results: Of 365 participants, 36.7% (n = 134) reported the current or past intake of EVE, including 31.5% (n = 115) who were taking EVE at study entry. The mean EVE dosage was 6.1 ± 2.9 mg/m (median: 5.6 mg/m, range 2.0-15.1 mg/m) in children and adolescents and 4 ± 2.1 mg/m (median: 3.7 mg/m, range 0.8-10.1 mg/m) in adult patients. An early diagnosis of TSC, the presence of angiomyolipoma, drug-refractory epilepsy, neuropsychiatric manifestations, subependymal giant cell astrocytoma, cardiac rhabdomyoma and overall multi-organ involvement were associated with the use of EVE as a disease-modifying treatment. The reported efficacy was 64.0% for angiomyolipoma (75% in adult patients), 66.2% for drug-refractory epilepsy, and 54.4% for subependymal giant cell astrocytoma. The overall retention rate for EVE was 85.8%. The retention rates after 12 months of EVE therapy were higher among adults (93.7%) than among children and adolescents (88.7%; 90.5% vs 77.4% after 24 months; 87.3% vs 77.4% after 36 months). Tolerability was acceptable, with 70.9% of patients overall reporting adverse events, including stomatitis (47.0%), acne-like rash (7.7%), increased susceptibility to common infections and lymphoedema (each 6.0%), which were the most frequently reported symptoms. With a total score of 41.7 compared with 36.8 among patients not taking EVE, patients currently being treated with EVE showed an increased Liverpool Adverse Event Profile. Noticeable deviations in the sub-items 'tiredness', 'skin problems' and 'mouth/gum problems', which are likely related to EVE-typical adverse effects, were more frequently reported among patients taking EVE.

Conclusions: From the patients' perspective, EVE is an effective and relatively well-tolerated disease-modifying treatment option for children, adolescents and adults with TSC, associated with a high long-term retention rate that can be individually considered for each patient. Everolimus therapy should ideally be supervised by a centre experienced in the use of mechanistic target of rapamycin inhibitors, and adverse effects should be monitored on a regular basis.
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http://dx.doi.org/10.1007/s40263-021-00839-4DOI Listing
July 2021

Direct and indirect costs and cost-driving factors of Tuberous sclerosis complex in children, adolescents, and caregivers: a multicenter cohort study.

Orphanet J Rare Dis 2021 06 21;16(1):282. Epub 2021 Jun 21.

Division of Pediatric Epileptology, Centre for Paediatrics and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

Background: Tuberous sclerosis complex (TSC), a multisystem genetic disorder, affects many organs and systems, characterized by benign growths. This German multicenter study estimated the disease-specific costs and cost-driving factors associated with various organ manifestations in TSC patients.

Methods: A validated, three-month, retrospective questionnaire was administered to assess the sociodemographic and clinical characteristics, organ manifestations, direct, indirect, out-of-pocket, and nursing care-level costs, completed by caregivers of patients with TSC throughout Germany.

Results: The caregivers of 184 patients (mean age 9.8 ± 5.3 years, range 0.7-21.8 years) submitted questionnaires. The reported TSC disease manifestations included epilepsy (92%), skin disorders (86%), structural brain disorders (83%), heart and circulatory system disorders (67%), kidney and urinary tract disorders (53%), and psychiatric disorders (51%). Genetic variations in TSC2 were reported in 46% of patients, whereas 14% were reported in TSC1. Mean total direct health care costs were EUR 4949 [95% confidence interval (95% CI) EUR 4088-5863, median EUR 2062] per patient over three months. Medication costs represented the largest direct cost category (54% of total direct costs, mean EUR 2658), with mechanistic target of rapamycin (mTOR) inhibitors representing the largest share (47%, EUR 2309). The cost of anti-seizure drugs (ASDs) accounted for a mean of only EUR 260 (5%). Inpatient costs (21%, EUR 1027) and ancillary therapy costs (8%, EUR 407) were also important direct cost components. The mean nursing care-level costs were EUR 1163 (95% CI EUR 1027-1314, median EUR 1635) over three months. Total indirect costs totaled a mean of EUR 2813 (95% CI EUR 2221-3394, median EUR 215) for mothers and EUR 372 (95% CI EUR 193-586, median EUR 0) for fathers. Multiple regression analyses revealed polytherapy with two or more ASDs and the use of mTOR inhibitors as independent cost-driving factors of total direct costs. Disability and psychiatric disease were independent cost-driving factors for total indirect costs as well as for nursing care-level costs.

Conclusions: This study revealed substantial direct (including medication), nursing care-level, and indirect costs associated with TSC over three months, highlighting the spectrum of organ manifestations and their treatment needs in the German healthcare setting.

Trial Registration: DRKS, DRKS00016045. Registered 01 March 2019, http://www.drks.de/DRKS00016045.
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http://dx.doi.org/10.1186/s13023-021-01899-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8218507PMC
June 2021

KCNT1-related epilepsies and epileptic encephalopathies: phenotypic and mutational spectrum.

Brain 2021 Jun 11. Epub 2021 Jun 11.

Pediatric Neurology Department, Lyon University Hospital, 69500 Bron, France.

Variants in KCNT1, encoding a sodium-gated potassium channel (subfamily T member 1), have been associated with a spectrum of epilepsies and neurodevelopmental disorders. These range from familial autosomal dominant or sporadic sleep-related hypermotor epilepsy ((AD)SHE) to epilepsy of infancy with migrating focal seizures (EIMFS) and include developmental and epileptic encephalopathies (DEE). This study aims to provide a comprehensive overview of the phenotypic and genotypic spectrum of KCNT1 mutation-related epileptic disorders in 248 individuals, including 66 unpreviously published and 182 published cases, the largest cohort reported so far. Four phenotypic groups emerged from our analysis: i) EIMFS (152 individuals, 33 previously unpublished); ii) DEE other than EIMFS (non-EIMFS DEE) (37 individuals, 17 unpublished); iii) (AD)SHE (53 patients, 14 unpublished); iv) other phenotypes (6 individuals, 2 unpublished). In our cohort of 66 new cases, the most common phenotypic features were: a) in EIMFS, heterogeneity of seizure types, including epileptic spasms, epilepsy improvement over time, no epilepsy-related deaths; b) in non-EIMFS DEE, possible onset with West syndrome, occurrence of atypical absences, possible evolution to DEE with SHE features; one case of sudden unexplained death in epilepsy (SUDEP); c) in (AD)SHE, we observed a high prevalence of drug-resistance, although seizure frequency improved with age in some individuals, appearance of cognitive regression after seizure onset in all patients, no reported severe psychiatric disorders, although behavioural/psychiatric comorbidities were reported in about 50% of the patients, SUDEP in one individual; d) other phenotypes in individuals with mutation of KCNT1 included temporal lobe epilepsy, and epilepsy with tonic-clonic seizures and cognitive regression. Genotypic analysis of the whole cohort of 248 individuals showed only missense mutations and one inframe deletion in KCNT1. Although the KCNT1 mutations in affected individuals were seen to be distributed among the different domains of the KCNT1 protein, genotype-phenotype considerations showed many of the (AD)SHE-associated mutations to be clustered around the RCK2 domain in the C-terminus, distal to the NADP domain. Mutations associated with EIMFS/non-EIMFS DEE did not show a particular pattern of distribution in the KCNT1 protein. Recurrent KCNT1 mutations were seen to be associated with both severe and less severe phenotypes. Our study further defines and broadens the phenotypic and genotypic spectrums of KCNT1-related epileptic conditions and emphasizes the increasingly important role of this gene in the pathogenesis of early onset DEEs as well as in focal epilepsies, namely (AD)SHE.
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http://dx.doi.org/10.1093/brain/awab219DOI Listing
June 2021

Prescription patterns of antiseizure drugs in tuberous sclerosis complex (TSC)-associated epilepsy: a multicenter cohort study from Germany and review of the literature.

Expert Rev Clin Pharmacol 2021 Jun 31;14(6):749-760. Epub 2021 May 31.

Department of Neuropediatrics and Social Pediatrics, St. Josef-Hospital, University Hospital of Pediatrics and Adolescent Medicine, Ruhr-University Bochum, Bochum, Germany.

Objective: Seizures are a primary and early disease manifestation of Tuberous Sclerosis Complex (TSC). We aimed to describe the age-stratified patterns of antiseizure drug (ASD) treatments among children, adolescents, and adults with TSC in Germany. Additionally, we reviewed real-world and clinical study evidence regarding ASD utilization in patients with TSC.

Methods: We evaluated the pattern of routine ASD use and everolimus prescriptions based on a 2019 multicenter survey of 268 individuals with TSC-associated epilepsy. We contextualized the results with a structured review of real-world and clinical study evidence.

Results: TSC-associated epilepsy treatment comprises a wide variety of ASDs. In this German sample, the majority of patients were treated with polytherapy, and lamotrigine (34.7%), valproate (32.8%), oxcarbazepine (28.7%), vigabatrin (19.0%), and levetiracetam (17.9%) were identified as the most-commonly used ASDs. In addition, everolimus was used by 32.5% of patients. In adherence to current TSC guidelines, the disease-modifying ASD vigabatrin was widely used in children (58% below the age of 5 years), whereas treatment in adults did not necessarily reflect guideline preference for (partial) GABAergic ASDs.

Conclusions: The selection of ASDs for patients with TSC-associated epilepsy follows well-evaluated recommendations, including the guidelines regarding vigabatrin use in children. Several characteristics, such as the comparatively high frequency of valproate use and polytherapy, reflect the severity of TSC-associated epilepsy.
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http://dx.doi.org/10.1080/17512433.2021.1911643DOI Listing
June 2021

The Phenotypic Spectrum of PRRT2-Associated Paroxysmal Neurologic Disorders in Childhood.

Biomedicines 2020 Oct 28;8(11). Epub 2020 Oct 28.

Department of Pediatric Neurology, Children's Hospital Datteln, Witten/Herdecke University, 45711 Datteln, Germany.

Pathogenic variants in , encoding the proline-rich transmembrane protein 2, have been associated with an evolving spectrum of paroxysmal neurologic disorders. Based on a cohort of children with PRRT2-related infantile epilepsy, this study aimed at delineating the broad clinical spectrum of PRRT2-associated phenotypes in these children and their relatives. Only a few recent larger cohort studies are on record and findings from single reports were not confirmed so far. We collected detailed genetic and phenotypic data of 40 previously unreported patients from 36 families. All patients had benign infantile epilepsy and harbored pathogenic variants in (core cohort). Clinical data of 62 family members were included, comprising a cohort of 102 individuals (extended cohort) with PRRT2-associated neurological disease. Additional phenotypes in the cohort of patients with benign sporadic and familial infantile epilepsy consist of movement disorders with paroxysmal kinesigenic dyskinesia in six patients, infantile-onset movement disorders in 2 of 40 individuals, and episodic ataxia after mild head trauma in one girl with bi-allelic variants in . The same girl displayed a focal cortical dysplasia upon brain imaging. Familial hemiplegic migraine and migraine with aura were reported in nine families. A single individual developed epilepsy with continuous spikes and waves during sleep. In addition to known variants, we report the novel variant c.843G>T, p.(Trp281Cys) that co-segregated with benign infantile epilepsy and migraine in one family. Our study highlights the variability of clinical presentations of patients harboring pathogenic variants and expands the associated phenotypic spectrum.
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http://dx.doi.org/10.3390/biomedicines8110456DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7719266PMC
October 2020

Semantic Similarity Analysis Reveals Robust Gene-Disease Relationships in Developmental and Epileptic Encephalopathies.

Am J Hum Genet 2020 10 26;107(4):683-697. Epub 2020 Aug 26.

Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; The Epilepsy NeuroGenetics Initiative (ENGIN), Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Biomedical and Health Informatics (DBHi), Children's Hospital of Philadelphia, Philadelphia, PA 19146, USA; Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

More than 100 genetic etiologies have been identified in developmental and epileptic encephalopathies (DEEs), but correlating genetic findings with clinical features at scale has remained a hurdle because of a lack of frameworks for analyzing heterogenous clinical data. Here, we analyzed 31,742 Human Phenotype Ontology (HPO) terms in 846 individuals with existing whole-exome trio data and assessed associated clinical features and phenotypic relatedness by using HPO-based semantic similarity analysis for individuals with de novo variants in the same gene. Gene-specific phenotypic signatures included associations of SCN1A with "complex febrile seizures" (HP: 0011172; p = 2.1 × 10) and "focal clonic seizures" (HP: 0002266; p = 8.9 × 10), STXBP1 with "absent speech" (HP: 0001344; p = 1.3 × 10), and SLC6A1 with "EEG with generalized slow activity" (HP: 0010845; p = 0.018). Of 41 genes with de novo variants in two or more individuals, 11 genes showed significant phenotypic similarity, including SCN1A (n = 16, p < 0.0001), STXBP1 (n = 14, p = 0.0021), and KCNB1 (n = 6, p = 0.011). Including genetic and phenotypic data of control subjects increased phenotypic similarity for all genetic etiologies, whereas the probability of observing de novo variants decreased, emphasizing the conceptual differences between semantic similarity analysis and approaches based on the expected number of de novo events. We demonstrate that HPO-based phenotype analysis captures unique profiles for distinct genetic etiologies, reflecting the breadth of the phenotypic spectrum in genetic epilepsies. Semantic similarity can be used to generate statistical evidence for disease causation analogous to the traditional approach of primarily defining disease entities through similar clinical features.
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http://dx.doi.org/10.1016/j.ajhg.2020.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7536581PMC
October 2020

Whole-Exome Sequencing in NF1-Related West Syndrome Leads to the Identification of KCNC2 as a Novel Candidate Gene for Epilepsy.

Neuropediatrics 2020 10 11;51(5):368-372. Epub 2020 May 11.

Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany.

Patients with neurofibromatosis type 1 (NF1) have an increased risk for West syndrome (WS), but the underlying mechanisms linking NF1 and WS are unknown. In contrast to other neurocutaneous syndromes, intracerebral abnormalities explaining the course of infantile spasms (IS) are often absent and the seizure outcome is usually favorable. Several studies have investigated a potential genotype-phenotype correlation between and seizure susceptibility, but an association was not identified. Therefore, we identified three patients with NF1-related WS (NF1-WS) in a cohort of 51 NF1 patients and performed whole-exome sequencing (WES) to identify genetic modifiers. In two NF1 patients with WS and good seizure outcome, we did not identify variants in epilepsy-related genes. However, in a single patient with NF1-WS and transition to drug-resistant epilepsy, we identified a variant in (c.G499T, p.D167Y) coding for Kv3.2 as a previously undescribed potassium channel to be correlated to epilepsy. Electrophysiological studies of the identified variant demonstrated both a strong loss-of-function effect for the current amplitude and a gain-of-function effect for the channel activation recommending a complex network effect. These results suggest that systematic genetic analysis for potentially secondary genetic etiologies in NF1 patients and severe epilepsy presentations should be done.
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http://dx.doi.org/10.1055/s-0040-1710524DOI Listing
October 2020

RARS1-related hypomyelinating leukodystrophy: Expanding the spectrum.

Ann Clin Transl Neurol 2020 01 8;7(1):83-93. Epub 2019 Dec 8.

Metabolic Unit, Department of Clinical Chemistry, Amsterdam Neuroscience, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.

Objective: Biallelic variants in RARS1, encoding the cytoplasmic tRNA synthetase for arginine (ArgRS), cause a hypomyelinating leukodystrophy. This study aimed to investigate clinical, neuroradiological and genetic features of patients with RARS1-related disease, and to identify possible genotype-phenotype relationships.

Methods: We performed a multinational cross-sectional survey among 20 patients with biallelic RARS1 variants identified by next-generation sequencing techniques. Clinical data, brain MRI findings and genetic results were analyzed. Additionally, ArgRS activity was measured in fibroblasts of four patients, and translation of long and short ArgRS isoforms was quantified by western blot.

Results: Clinical presentation ranged from severe (onset in the first 3 months, usually with refractory epilepsy and early brain atrophy), to intermediate (onset in the first year with nystagmus and spasticity), and mild (onset around or after 12 months with minimal cognitive impairment and preserved independent walking). The most frequent RARS1 variant, c.5A>G, led to mild or intermediate phenotypes, whereas truncating variants and variants affecting amino acids close to the ArgRS active centre led to severe phenotypes. ArgRS activity was significantly reduced in three patients with intermediate and severe phenotypes; in a fourth patient with intermediate to severe presentation, we measured normal ArgRS activity, but found translation mainly of the short instead of the long ArgRS isoform.

Interpretation: Variants in RARS1 impair ArgRS activity and do not only lead to a classic hypomyelination presentation with nystagmus and spasticity, but to a wide spectrum, ranging from severe, early-onset epileptic encephalopathy with brain atrophy to mild disease with relatively preserved myelination.
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http://dx.doi.org/10.1002/acn3.50960DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952319PMC
January 2020

A post glycosylphosphatidylinositol (GPI) attachment to proteins, type 2 (PGAP2) variant identified in Mabry syndrome index cases: Molecular genetics of the prototypical inherited GPI disorder.

Eur J Med Genet 2020 Apr 2;63(4):103822. Epub 2019 Dec 2.

Department of Pediatrics, College of Medicine, University of Kentucky, United States.

We report that recessive inheritance of a post-GPI attachment to proteins 2 (PGAP2) gene variant results in the hyperphosphatasia with neurologic deficit (HPMRS) phenotype described by Mabry et al., in 1970. HPMRS, or Mabry syndrome, is now known to be one of 21 inherited glycosylphosphatidylinositol (GPI) deficiencies (IGDs), or GPI biosynthesis defects (GPIBDs). Bi-allelic mutations in at least six genes result in HPMRS phenotypes. Disruption of four phosphatidylinositol glycan (PIG) biosynthesis genes, PIGV, PIGO, PIGW and PIGY, expressed in the endoplasmic reticulum, result in HPMRS 1, 2, 5 and 6; disruption of the PGAP2 and PGAP3 genes, necessary for stabilizing the association of GPI anchored proteins (AP) with the Golgi membrane, result in HPMRS 3 and 4. We used exome sequencing to identify a novel homozygous missense PGAP2 variant NM_014489.3:c.881C > T, p.Thr294Met in two index patients and targeted sequencing to identify this variant in an unrelated patient. Rescue assays were conducted in two PGAP2 deficient cell lines, PGAP2 KO cells generated by CRISPR/Cas9 and PGAP2 deficient CHO cells, in order to examine the pathogenicity of the PGAP2 variant. First, we used the CHO rescue assay to establish that the wild type PGAP2 isoform 1, translated from transcript 1, is less active than the wild type PGAP2 isoform 8, translated from transcript 12 (alternatively spliced to omit exon 3). As a result, in our variant rescue assays, we used the more active NM_001256240.2:c.698C > T, p.Thr233Met isoform 8 instead of NM_014489.3:c.881C > T, p.Thr294Met isoform 1. Flow cytometric analysis showed that restoration of cell surface CD59 and CD55 with variant PGAP2 isoform 8, driven by the weak (pTA FLAG) promoter, was less efficient than wild type isoform 8. Therefore, we conclude that recessive inheritance of c.881C > T PGAP2, expressed as the hypomorphic PGAP2 c.698C > T, p.Thr233Met isoform 8, results in prototypical Mabry phenotype, HPMRS3 (GPIBD 8 [MIM: 614207]). This study highlights the need for long-term follow up of individuals with rare diseases in order to ensure that they benefit from innovations in diagnosis and treatment.
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http://dx.doi.org/10.1016/j.ejmg.2019.103822DOI Listing
April 2020

SLC35A2-CDG: Functional characterization, expanded molecular, clinical, and biochemical phenotypes of 30 unreported Individuals.

Hum Mutat 2019 07 24;40(7):908-925. Epub 2019 Apr 24.

Department of Metabolic Medicine, The Royal Children's Hospital, Melbourne, Parkville, Victoria, Australia.

Pathogenic de novo variants in the X-linked gene SLC35A2 encoding the major Golgi-localized UDP-galactose transporter required for proper protein and lipid glycosylation cause a rare type of congenital disorder of glycosylation known as SLC35A2-congenital disorders of glycosylation (CDG; formerly CDG-IIm). To date, 29 unique de novo variants from 32 unrelated individuals have been described in the literature. The majority of affected individuals are primarily characterized by varying degrees of neurological impairments with or without skeletal abnormalities. Surprisingly, most affected individuals do not show abnormalities in serum transferrin N-glycosylation, a common biomarker for most types of CDG. Here we present data characterizing 30 individuals and add 26 new variants, the single largest study involving SLC35A2-CDG. The great majority of these individuals had normal transferrin glycosylation. In addition, expanding the molecular and clinical spectrum of this rare disorder, we developed a robust and reliable biochemical assay to assess SLC35A2-dependent UDP-galactose transport activity in primary fibroblasts. Finally, we show that transport activity is directly correlated to the ratio of wild-type to mutant alleles in fibroblasts from affected individuals.
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http://dx.doi.org/10.1002/humu.23731DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6661012PMC
July 2019

Clinical spectrum of -related epileptic disorders.

Neurology 2019 03 8;92(11):e1238-e1249. Epub 2019 Feb 8.

From the University of Tübingen (S. Wolking, J.M., Y.G.W., H.L., J.S.), Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Tübingen, Germany; Luxembourg Centre for Systems Biomedicine (P.M.), University of Luxembourg, Esch-sur-Alzette; Pediatric Neurology and Neurogenetics Unit and Laboratories (D.M., R.G., C.M.), Children's Hospital Anna Meyer, University of Florence, Italy; Danish Epilepsy Centre (R.S.M.), Dianalund; Institute for Regional Health Services (R.S.M.), University of Southern Denmark, Odense; Department of Clinical and Experimental Epilepsy (S.B.), UCL Institute of Neurology and Epilepsy Society, UK, London; Division of Neurology (K.L.H., I.H.), Children's Hospital of Philadelphia, PA; Department of Pediatric Neurology (C.D.A.), Centre de Compétences Maladies Rares, CHU Besançon; Service de Génétique (N.C.), Hospices Civils des Lyon, Bron; GENDEV Team (N.C.), Neurosciences Research Center of Lyon, Bron, France; Neuropediatric Clinic and Clinic for Neurorehabilitation (K.S.), Epilepsy Center for Children and Adolescents, Schoen Klinik Vogtareuth, Germany; Beaumont Hospital (P.W.-W.), Dublin, Ireland; Department of Pediatrics, Division of Medical Genetics, Institute of Human Genetics (B.A.M.), Departments of Neurology and Pediatrics (A.N.), and Departments of Neurology and Pediatrics, and Institute of Human Genetics (M.R.C.), University of California, San Francisco; Department of Neurology (W.V.P.), University Hospitals Leuven, Belgium; Department of Pediatrics (L.L.S.), Hvidovre Hospital, Denmark; King's College Hospital (S.O., E.H., S.G., D.K.P.), London; Evelina London Children's Hospital (S.O., E.H., S.G.), London, UK; Section of Genetics (K.B., M.S.S.), Department of Pediatrics, University of Colorado and Children's Hospital Colorado, Aurora; Clinique Bernoise Montana (T.D.), Crans-Montana, Switzerland; Department of Neuropediatrics (H.M.), University Medical Center Schleswig-Holstein, Christian-Albrechts University, Kiel, Germany; National Institute for Health Research Oxford Biomedical Research Centre, Wellcome Centre for Human Genetics (A.T.P., S.J.L.K., J.C.T.) and Department of Oncology (D.V.V.), University of Oxford, UK; Epilepsy Center (M.P.C.), Health Sciences Department, San Paolo Hospital, University of Milan; Child Neuropsychiatry (F.D.), Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, Italy; Departments of Neurology and Clinical Genomics (R.H.G.) and Health Sciences Research and Clinical Genomics (E.W.K., C.K.), Mayo Clinic, Rochester, MN; Ambry Genetics (Z.P.), Aliso Viejo, CA; Department of Clinical Neuroscience (S.T.), King's College London; New Medicines (M.A., D.M.), UCB Pharma, Slough, UK; Neuropediatric Clinic and Clinic for Neurorehabilitation (G.J.K.), Epilepsy Center for Children and Adolescents, Schoen Klinik Vogtareuth, Germany; Research Institute for Rehabilitation, Transition and Palliation (G.J.K.), PMU Salzburg, Austria; Department of Neurology (D.H.L.), University of California, San Francisco; Neurogenetics Group (S. Weckhuysen), Center for Molecular Neurology, VIB, Antwerp; Laboratory of Neurogenetics (S. Weckhuysen), Institute Born-Bunge, University of Antwerp; Department of Neurology (S. Weckhuysen), Antwerp University Hospital, Antwerp, Belgium; Department of Basic & Clinical Neuroscience, Institute of Psychiatry, Psychology & Neuroscience (D.K.P.), MRC Centre for Neurodevelopmental Disorders (D.K.P.), King's College London, UK; Evelina London Children's Hospital (D.K.P.), London, UK; Department of Neuropediatrics (I.H.), University Medical Center Schleswig-Holstein, Christian-Albrechts University, Kiel, Germany; Institute of Neuroscience (R.H.T.), Henry Wellcome Building, Newcastle University; Neurology Research Group (M.I.R.), Institute of Life Science, Swansea University Medical School, Swansea, UK; Service de Génétique (G.L.), Hospices Civils des Lyon, Bron; GENDEV Team (G.L.), Neurosciences Research Center of Lyon, Bron, France; NIHR University College London Hospitals Biomedical Research Centre (S.M.S.), UCL Institute of Neurology, London, UK; Cologne Center for Genomics (D.L.), University of Cologne, Germany; Stanley Center for Psychiatric Research (D.L.) and Program in Medical and Population Genetics (D.L.), Broad Institute of MIT and Harvard, Cambridge; Psychiatric and Neurodevelopmental Genetics Unit (D.L.), Massachusetts General Hospital and Harvard Medical School, Boston.

Objective: The aim of this study was to expand the spectrum of epilepsy syndromes related to , encoding the presynaptic protein syntaxin-1B, and establish genotype-phenotype correlations by identifying further disease-related variants.

Methods: We used next-generation sequencing in the framework of research projects and diagnostic testing. Clinical data and EEGs were reviewed, including already published cases. To estimate the pathogenicity of the variants, we used established and newly developed in silico prediction tools.

Results: We describe 17 new variants in , which are distributed across the whole gene. We discerned 4 different phenotypic groups across the newly identified and previously published patients (49 patients in 23 families): (1) 6 sporadic patients or families (31 affected individuals) with febrile and afebrile seizures with a benign course, generally good drug response, normal development, and without permanent neurologic deficits; (2) 2 patients with genetic generalized epilepsy without febrile seizures and cognitive deficits; (3) 13 patients or families with intractable seizures, developmental regression after seizure onset and additional neuropsychiatric symptoms; (4) 2 patients with focal epilepsy. More often, we found loss-of-function mutations in benign syndromes, whereas missense variants in the SNARE motif of syntaxin-1B were associated with more severe phenotypes.

Conclusion: These data expand the genetic and phenotypic spectrum of -related epilepsies to a diverse range of epilepsies that span the International League Against Epilepsy classification. Variants in are protean and contribute to many different epilepsy phenotypes, similar to , the most important gene associated with fever-associated epilepsies.
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http://dx.doi.org/10.1212/WNL.0000000000007089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6511102PMC
March 2019

TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants.

Genet Med 2019 03 24;21(3):601-607. Epub 2018 Sep 24.

GeneDx, Gaithersburg, Maryland, USA.

Purpose: TANGO2-related disorders were first described in 2016 and prior to this publication, only 15 individuals with TANGO2-related disorder were described in the literature. Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias. We assess whether genotype and phenotype of TANGO2-related disorder has expanded since the initial discovery and determine the efficacy of exome sequencing (ES) as a diagnostic tool for detecting variants.

Methods: We present a series of 14 individuals from 11 unrelated families with complex medical and developmental histories, in whom ES or microarray identified compound heterozygous or homozygous variants in TANGO2.

Results: The initial presentation of patients with TANGO2-related disorders can be variable, including primarily neurological presentations. We expand the phenotype and genotype for TANGO2, highlighting the variability of the disorder.

Conclusion: TANGO2-related disorders can have a more diverse clinical presentation than previously anticipated. We illustrate the utility of routine ES data reanalysis whereby discovery of novel disease genes can lead to a diagnosis in previously unsolved cases and the need for additional copy-number variation analysis when ES is performed.
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http://dx.doi.org/10.1038/s41436-018-0137-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752277PMC
March 2019

Rare coding variants in genes encoding GABA receptors in genetic generalised epilepsies: an exome-based case-control study.

Lancet Neurol 2018 08 17;17(8):699-708. Epub 2018 Jul 17.

Background: Genetic generalised epilepsy is the most common type of inherited epilepsy. Despite a high concordance rate of 80% in monozygotic twins, the genetic background is still poorly understood. We aimed to investigate the burden of rare genetic variants in genetic generalised epilepsy.

Methods: For this exome-based case-control study, we used three different genetic generalised epilepsy case cohorts and three independent control cohorts, all of European descent. Cases included in the study were clinically evaluated for genetic generalised epilepsy. Whole-exome sequencing was done for the discovery case cohort, a validation case cohort, and two independent control cohorts. The replication case cohort underwent targeted next-generation sequencing of the 19 known genes encoding subunits of GABA receptors and was compared to the respective GABA receptor variants of a third independent control cohort. Functional investigations were done with automated two-microelectrode voltage clamping in Xenopus laevis oocytes.

Findings: Statistical comparison of 152 familial index cases with genetic generalised epilepsy in the discovery cohort to 549 ethnically matched controls suggested an enrichment of rare missense (Nonsyn) variants in the ensemble of 19 genes encoding GABA receptors in cases (odds ratio [OR] 2·40 [95% CI 1·41-4·10]; p=0·0014, adjusted p=0·019). Enrichment for these genes was validated in a whole-exome sequencing cohort of 357 sporadic and familial genetic generalised epilepsy cases and 1485 independent controls (OR 1·46 [95% CI 1·05-2·03]; p=0·0081, adjusted p=0·016). Comparison of genes encoding GABA receptors in the independent replication cohort of 583 familial and sporadic genetic generalised epilepsy index cases, based on candidate-gene panel sequencing, with a third independent control cohort of 635 controls confirmed the overall enrichment of rare missense variants for 15 GABA receptor genes in cases compared with controls (OR 1·46 [95% CI 1·02-2·08]; p=0·013, adjusted p=0·027). Functional studies for two selected genes (GABRB2 and GABRA5) showed significant loss-of-function effects with reduced current amplitudes in four of seven tested variants compared with wild-type receptors.

Interpretation: Functionally relevant variants in genes encoding GABA receptor subunits constitute a significant risk factor for genetic generalised epilepsy. Examination of the role of specific gene groups and pathways can disentangle the complex genetic architecture of genetic generalised epilepsy.

Funding: EuroEPINOMICS (European Science Foundation through national funding organisations), Epicure and EpiPGX (Sixth Framework Programme and Seventh Framework Programme of the European Commission), Research Unit FOR2715 (German Research Foundation and Luxembourg National Research Fund).
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http://dx.doi.org/10.1016/S1474-4422(18)30215-1DOI Listing
August 2018

De novo variants in neurodevelopmental disorders with epilepsy.

Nat Genet 2018 07 25;50(7):1048-1053. Epub 2018 Jun 25.

University of Leipzig Hospitals and Clinics, Leipzig, Germany.

Epilepsy is a frequent feature of neurodevelopmental disorders (NDDs), but little is known about genetic differences between NDDs with and without epilepsy. We analyzed de novo variants (DNVs) in 6,753 parent-offspring trios ascertained to have different NDDs. In the subset of 1,942 individuals with NDDs with epilepsy, we identified 33 genes with a significant excess of DNVs, of which SNAP25 and GABRB2 had previously only limited evidence of disease association. Joint analysis of all individuals with NDDs also implicated CACNA1E as a novel disease-associated gene. Comparing NDDs with and without epilepsy, we found missense DNVs, DNVs in specific genes, age of recruitment, and severity of intellectual disability to be associated with epilepsy. We further demonstrate the extent to which our results affect current genetic testing as well as treatment, emphasizing the benefit of accurate genetic diagnosis in NDDs with epilepsy.
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http://dx.doi.org/10.1038/s41588-018-0143-7DOI Listing
July 2018

Variants in the ATP1A3 Gene Mutations within Severe Apnea Starting in Early Infancy: An Observational Study of Two Cases with a Possible Relation to Epileptic Activity.

Neuropediatrics 2018 10 25;49(5):342-346. Epub 2018 May 25.

Department of Neuropediatrics, University Medical Center Schleswig Holstein, Kiel, Germany.

Mutations in the gene are known to cause alternating hemiplegia of childhood (AHC) and rapid-onset dystonia parkinsonism (RDP). Both conditions are childhood-onset neurological disorders with distinct symptoms and different times of onset. has also been associated with CAPOS syndrome (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss). Within the various -related neurological syndromes, a specific genotype-phenotype correlation is starting to emerge. Several mutations such as the relatively common p.E815K pathogenic variant have been shown to strongly correlate with AHC, while others may cause both AHC and RDP. A significant subset of patients with AHC and RDP are reported to have epileptic seizures. Even though detailed clinical descriptions of seizures in childhood are rare, seizures involving apneic events seem to be frequent in -related neurological disorders. Here, we describe two children with unexplained severe apnea beginning around the first year of life and pathogenic variants in . We hypothesize that the symptoms are early-onset autonomic seizures related to the underlying pathogenic variants.
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http://dx.doi.org/10.1055/s-0038-1653978DOI Listing
October 2018

Mutations in PMPCB Encoding the Catalytic Subunit of the Mitochondrial Presequence Protease Cause Neurodegeneration in Early Childhood.

Am J Hum Genet 2018 04 22;102(4):557-573. Epub 2018 Mar 22.

Department of Neuropediatrics, Christian-Albrechts-University of Kiel, Kiel 24105, Germany; Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA. Electronic address:

Mitochondrial disorders causing neurodegeneration in childhood are genetically heterogeneous, and the underlying genetic etiology remains unknown in many affected individuals. We identified biallelic variants in PMPCB in individuals of four families including one family with two affected siblings with neurodegeneration and cerebellar atrophy. PMPCB encodes the catalytic subunit of the essential mitochondrial processing protease (MPP), which is required for maturation of the majority of mitochondrial precursor proteins. Mitochondria isolated from two fibroblast cell lines and induced pluripotent stem cells derived from one affected individual and differentiated neuroepithelial stem cells showed reduced PMPCB levels and accumulation of the processing intermediate of frataxin, a sensitive substrate for MPP dysfunction. Introduction of the identified PMPCB variants into the homologous S. cerevisiae Mas1 protein resulted in a severe growth and MPP processing defect leading to the accumulation of mitochondrial precursor proteins and early impairment of the biogenesis of iron-sulfur clusters, which are indispensable for a broad range of crucial cellular functions. Analysis of biopsy materials of an affected individual revealed changes and decreased activity in iron-sulfur cluster-containing respiratory chain complexes and dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes. We conclude that biallelic mutations in PMPCB cause defects in MPP proteolytic activity leading to dysregulation of iron-sulfur cluster biogenesis and triggering a complex neurological phenotype of neurodegeneration in early childhood.
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http://dx.doi.org/10.1016/j.ajhg.2018.02.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5985287PMC
April 2018

Effects of Levetiracetam and Sulthiame on EEG in benign epilepsy with centrotemporal spikes: A randomized controlled trial.

Seizure 2018 Mar 3;56:115-120. Epub 2018 Feb 3.

Children's Hospital, Vechta, Germany.

Purpose: BECTS (benign childhood epilepsy with centrotemporal spikes) is associated with characteristic EEG findings. This study examines the influence of anti-convulsive treatment on the EEG.

Methods: In a randomized controlled trial including 43 children with BECTS, EEGs were performed prior to treatment with either Sulthiame or Levetiracetam as well as three times under treatment. Using the spike-wave-index, the degree of EEG pathology was quantified. The EEG before and after initiation of treatment was analyzed. Both treatment arms were compared and the EEG of the children that were to develop recurrent seizures was compared with those that were successfully treated.

Results: Regardless of the treatment agent, the spike-wave-index was reduced significantly under treatment. There were no differences between the two treatment groups. In an additional analysis, the EEG characteristics of the children with recurrent seizures differed statistically significant from those that did not have any further seizures.

Conclusion: Both Sulthiame and Levetiracetam influence the EEG of children with BECTS. Persistent EEG pathologies are associated with treatment failures.
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http://dx.doi.org/10.1016/j.seizure.2018.01.015DOI Listing
March 2018

Characterization of glycosylphosphatidylinositol biosynthesis defects by clinical features, flow cytometry, and automated image analysis.

Genome Med 2018 01 9;10(1). Epub 2018 Jan 9.

The Jackson Laboratory for Genomic Medicine, 06032, Farmington, USA.

Background: Glycosylphosphatidylinositol biosynthesis defects (GPIBDs) cause a group of phenotypically overlapping recessive syndromes with intellectual disability, for which pathogenic mutations have been described in 16 genes of the corresponding molecular pathway. An elevated serum activity of alkaline phosphatase (AP), a GPI-linked enzyme, has been used to assign GPIBDs to the phenotypic series of hyperphosphatasia with mental retardation syndrome (HPMRS) and to distinguish them from another subset of GPIBDs, termed multiple congenital anomalies hypotonia seizures syndrome (MCAHS). However, the increasing number of individuals with a GPIBD shows that hyperphosphatasia is a variable feature that is not ideal for a clinical classification.

Methods: We studied the discriminatory power of multiple GPI-linked substrates that were assessed by flow cytometry in blood cells and fibroblasts of 39 and 14 individuals with a GPIBD, respectively. On the phenotypic level, we evaluated the frequency of occurrence of clinical symptoms and analyzed the performance of computer-assisted image analysis of the facial gestalt in 91 individuals.

Results: We found that certain malformations such as Morbus Hirschsprung and diaphragmatic defects are more likely to be associated with particular gene defects (PIGV, PGAP3, PIGN). However, especially at the severe end of the clinical spectrum of HPMRS, there is a high phenotypic overlap with MCAHS. Elevation of AP has also been documented in some of the individuals with MCAHS, namely those with PIGA mutations. Although the impairment of GPI-linked substrates is supposed to play the key role in the pathophysiology of GPIBDs, we could not observe gene-specific profiles for flow cytometric markers or a correlation between their cell surface levels and the severity of the phenotype. In contrast, it was facial recognition software that achieved the highest accuracy in predicting the disease-causing gene in a GPIBD.

Conclusions: Due to the overlapping clinical spectrum of both HPMRS and MCAHS in the majority of affected individuals, the elevation of AP and the reduced surface levels of GPI-linked markers in both groups, a common classification as GPIBDs is recommended. The effectiveness of computer-assisted gestalt analysis for the correct gene inference in a GPIBD and probably beyond is remarkable and illustrates how the information contained in human faces is pivotal in the delineation of genetic entities.
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http://dx.doi.org/10.1186/s13073-017-0510-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5759841PMC
January 2018

Neurodevelopmental Disorders Caused by De Novo Variants in KCNB1 Genotypes and Phenotypes.

JAMA Neurol 2017 10;74(10):1228-1236

Epilepsiezentrum Bethel, Krankenhaus Mara, Kinderepileptologie, Bielefeld, Germany.

Importance: Knowing the range of symptoms seen in patients with a missense or loss-of-function variant in KCNB1 and how these symptoms correlate with the type of variant will help clinicians with diagnosis and prognosis when treating new patients.

Objectives: To investigate the clinical spectrum associated with KCNB1 variants and the genotype-phenotype correlations.

Design, Setting, And Participants: This study summarized the clinical and genetic information of patients with a presumed pathogenic variant in KCNB1. Patients were identified in research projects or during clinical testing. Information on patients from previously published articles was collected and authors contacted if feasible. All patients were seen at a clinic at one of the participating institutes because of presumed genetic disorder. They were tested in a clinical setting or included in a research project.

Main Outcomes And Measures: The genetic variant and its inheritance and information on the patient's symptoms and characteristics in a predefined format. All variants were identified with massive parallel sequencing and confirmed with Sanger sequencing in the patient. Absence of the variant in the parents could be confirmed with Sanger sequencing in all families except one.

Results: Of 26 patients (10 female, 15 male, 1 unknown; mean age at inclusion, 9.8 years; age range, 2-32 years) with developmental delay, 20 (77%) carried a missense variant in the ion channel domain of KCNB1, with a concentration of variants in region S5 to S6. Three variants that led to premature stops were located in the C-terminal and 3 in the ion channel domain. Twenty-one of 25 patients (84%) had seizures, with 9 patients (36%) starting with epileptic spasms between 3 and 18 months of age. All patients had developmental delay, with 17 (65%) experiencing severe developmental delay; 14 (82%) with severe delay had behavioral problems. The developmental delay was milder in 4 of 6 patients with stop variants and in a patient with a variant in the S2 transmembrane element rather than the S4 to S6 region.

Conclusions And Relevance: De novo KCNB1 missense variants in the ion channel domain and loss-of-function variants in this domain and the C-terminal likely cause neurodevelopmental disorders with or without seizures. Patients with presumed pathogenic variants in KCNB1 have a variable phenotype. However, the type and position of the variants in the protein are (imperfectly) correlated with the severity of the disorder.
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http://dx.doi.org/10.1001/jamaneurol.2017.1714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5710242PMC
October 2017

encephalopathy: A new disease of vesicle fission.

Neurology 2017 Jul 30;89(4):385-394. Epub 2017 Jun 30.

Author affiliations are provided at the end of the article.

Objective: To evaluate the phenotypic spectrum caused by mutations in dynamin 1 (), encoding the presynaptic protein DNM1, and to investigate possible genotype-phenotype correlations and predicted functional consequences based on structural modeling.

Methods: We reviewed phenotypic data of 21 patients (7 previously published) with mutations. We compared mutation data to known functional data and undertook biomolecular modeling to assess the effect of the mutations on protein function.

Results: We identified 19 patients with de novo mutations in and a sibling pair who had an inherited mutation from a mosaic parent. Seven patients (33.3%) carried the recurrent p.Arg237Trp mutation. A common phenotype emerged that included severe to profound intellectual disability and muscular hypotonia in all patients and an epilepsy characterized by infantile spasms in 16 of 21 patients, frequently evolving into Lennox-Gastaut syndrome. Two patients had profound global developmental delay without seizures. In addition, we describe a single patient with normal development before the onset of a catastrophic epilepsy, consistent with febrile infection-related epilepsy syndrome at 4 years. All mutations cluster within the GTPase or middle domains, and structural modeling and existing functional data suggest a dominant-negative effect on DMN1 function.

Conclusions: The phenotypic spectrum of -related encephalopathy is relatively homogeneous, in contrast to many other genetic epilepsies. Up to one-third of patients carry the recurrent p.Arg237Trp variant, which is now one of the most common recurrent variants in epileptic encephalopathies identified to date. Given the predicted dominant-negative mechanism of this mutation, this variant presents a prime target for therapeutic intervention.
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http://dx.doi.org/10.1212/WNL.0000000000004152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574673PMC
July 2017

Genetic and phenotypic heterogeneity suggest therapeutic implications in SCN2A-related disorders.

Brain 2017 May;140(5):1316-1336

CeGaT - Center for Genomics and Transcriptomics, Tübingen, Germany.

Mutations in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been associated with a spectrum of epilepsies and neurodevelopmental disorders. Here, we report the phenotypes of 71 patients and review 130 previously reported patients. We found that (i) encephalopathies with infantile/childhood onset epilepsies (≥3 months of age) occur almost as often as those with an early infantile onset (<3 months), and are thus more frequent than previously reported; (ii) distinct phenotypes can be seen within the late onset group, including myoclonic-atonic epilepsy (two patients), Lennox-Gastaut not emerging from West syndrome (two patients), and focal epilepsies with an electrical status epilepticus during slow sleep-like EEG pattern (six patients); and (iii) West syndrome constitutes a common phenotype with a major recurring mutation (p.Arg853Gln: two new and four previously reported children). Other known phenotypes include Ohtahara syndrome, epilepsy of infancy with migrating focal seizures, and intellectual disability or autism without epilepsy. To assess the response to antiepileptic therapy, we retrospectively reviewed the treatment regimen and the course of the epilepsy in 66 patients for which well-documented medical information was available. We find that the use of sodium channel blockers was often associated with clinically relevant seizure reduction or seizure freedom in children with early infantile epilepsies (<3 months), whereas other antiepileptic drugs were less effective. In contrast, sodium channel blockers were rarely effective in epilepsies with later onset (≥3 months) and sometimes induced seizure worsening. Regarding the genetic findings, truncating mutations were exclusively seen in patients with late onset epilepsies and lack of response to sodium channel blockers. Functional characterization of four selected missense mutations using whole cell patch-clamping in tsA201 cells-together with data from the literature-suggest that mutations associated with early infantile epilepsy result in increased sodium channel activity with gain-of-function, characterized by slowing of fast inactivation, acceleration of its recovery or increased persistent sodium current. Further, a good response to sodium channel blockers clinically was found to be associated with a relatively small gain-of-function. In contrast, mutations in patients with late-onset forms and an insufficient response to sodium channel blockers were associated with loss-of-function effects, including a depolarizing shift of voltage-dependent activation or a hyperpolarizing shift of channel availability (steady-state inactivation). Our clinical and experimental data suggest a correlation between age at disease onset, response to sodium channel blockers and the functional properties of mutations in children with SCN2A-related epilepsy.
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http://dx.doi.org/10.1093/brain/awx054DOI Listing
May 2017

Gene expression analysis in untreated absence epilepsy demonstrates an inconsistent pattern.

Epilepsy Res 2017 05 28;132:84-90. Epub 2017 Feb 28.

Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Kiel University, Kiel, Germany. Electronic address:

Objective: Childhood and Juvenile Absence Epilepsy account for 30% of all genetic generalized epilepsies with a strong genetic contribution. At the current state the genetic background remains to be resolved. The aim of this study was to identify disease associated transcripts pinpointing potential underlying disease mechanisms in patients with CAE and JAE.

Methods: We performed gene expression analysis from peripheral blood mononuclear cells (PBMCs) in 30 patients with newly-diagnosed absence epilepsy prior to initiating treatment and 30 healthy age - and gender-matched pediatric controls. In a first group (group 1), 10 patients and controls we performed genome-wide transcriptome analysis using the Affymetrix HG U133 2.0+ microarray. 75 differentially expressed genes were followed up by qRT-PCR in two independent groups of 10 patients and controls (group 2 and 3). Furthermore, we analyzed 18 candidate genes by qRT-PCR in groups 2 and 3, which had previously been considered strong candidates for genetic epilepsies.

Results: Genome-wide gene expression analysis in group 1 revealed 601 differentially regulated genes. Independent validation of 75 group 1-derived genes by qRT-PCR in groups 2 and 3 confirmed candidate genes with a consistent, but non-significant pattern of up- or down-regulation across all groups (ATP1B3, CAND1, PRPF6, TRIM8). Previously known genes including GABRA1, GABRB3, GABRG2, and RCN2 showed evidence for up- or down-regulation in individual experiments, but were not reliable across groups either.

Discussion: Gene expression analysis in absence epilepsy from PMBCs displayed a high degree of heterogeneity between different patient groups. Our study provides several potentially interesting candidate genes, while demonstrating the limits of using gene expression analysis from blood in the identification of novel pathogenic mechanisms. In particular, we found that gene expression levels vary in response to altered experimental conditions, representing a substantial challenge for the identification of disease-related gene expression signatures for neurological diseases from whole blood.
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http://dx.doi.org/10.1016/j.eplepsyres.2017.02.008DOI Listing
May 2017

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

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

Pitfalls in genetic testing: the story of missed SCN1A mutations.

Mol Genet Genomic Med 2016 Jul 14;4(4):457-64. Epub 2016 Apr 14.

Department of Neuropediatrics University Medical Center Schleswig-Holstein Kiel Germany.

Background: Sanger sequencing, still the standard technique for genetic testing in most diagnostic laboratories and until recently widely used in research, is gradually being complemented by next-generation sequencing (NGS). No single mutation detection technique is however perfect in identifying all mutations. Therefore, we wondered to what extent inconsistencies between Sanger sequencing and NGS affect the molecular diagnosis of patients. Since mutations in SCN1A, the major gene implicated in epilepsy, are found in the majority of Dravet syndrome (DS) patients, we focused on missed SCN1A mutations.

Methods: We sent out a survey to 16 genetic centers performing SCN1A testing.

Results: We collected data on 28 mutations initially missed using Sanger sequencing. All patients were falsely reported as SCN1A mutation-negative, both due to technical limitations and human errors.

Conclusion: We illustrate the pitfalls of Sanger sequencing and most importantly provide evidence that SCN1A mutations are an even more frequent cause of DS than already anticipated.
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http://dx.doi.org/10.1002/mgg3.217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4947864PMC
July 2016

Idiopathic focal epilepsies: the "lost tribe".

Epileptic Disord 2016 Sep;18(3):252-88

GSTT, Clin Neurophysiology and Epilepsies, Lambeth Wing, St Thomas' Hospital, London, UK.

The term idiopathic focal epilepsies of childhood (IFE) is not formally recognised by the ILAE in its 2010 revision (Berg et al., 2010), nor are its members and boundaries precisely delineated. The IFEs are amongst the most commonly encountered epilepsy syndromes affecting children. They are fascinating disorders that hold many "treats" for both clinicians and researchers. For example, the IFEs pose many of the most interesting questions central to epileptology: how are functional brain networks involved in the manifestation of epilepsy? What are the shared mechanisms of comorbidity between epilepsy and neurodevelopmental disorders? How do focal EEG discharges impact cognitive functioning? What explains the age-related expression of these syndromes? Why are EEG discharges and seizures so tightly locked to slow-wave sleep? In the last few decades, the clinical symptomatology and the respective courses of many IFEs have been described, although they are still not widely appreciated beyond the specialist community. Most neurologists would recognise the core syndromes of IFE to comprise: benign epilepsy of childhood with centro-temporal spikes or Rolandic epilepsy (BECTS/RE); Panayiotopoulos syndrome; and the idiopathic occipital epilepsies (Gastaut and photosensitive types). The Landau-Kleffner syndrome and the related (idiopathic) epilepsy with continuous spikes and waves in sleep (CSWS or ESES) are also often included, both as a consequence of the shared morphology of the interictal discharges and their potential evolution from core syndromes, for example, CSWS from BECTS. Atypical benign focal epilepsy of childhood also has shared electro-clinical features warranting inclusion. In addition, a number of less well-defined syndromes of IFE have been proposed, including benign childhood seizures with affective symptoms, benign childhood epilepsy with parietal spikes, benign childhood seizures with frontal or midline spikes, and benign focal seizures of adolescence. The term "benign" is often used in connection with the IFEs and is increasingly being challenged. Certainly most of these disorders are not associated with the devastating cognitive and behavioural problems seen with early childhood epileptic encephalopathies, such as West or Dravet syndromes. However, it is clear that specific, and sometimes persistent, neuropsychological deficits in attention, language and literacy accompany many of the IFEs that, when multiplied by the large numbers affected, make up a significant public health problem. Understanding the nature, distribution, evolution, risk and management of these is an important area of current research. A corollary to such questions regarding comorbidities is the role of focal interictal spikes and their enduring impact on cognitive functioning. What explains the paradox that epilepsies characterised by abundant interictal epileptiform abnormalities are often associated with very few clinical seizures? This is an exciting area in both clinical and experimental arenas and will eventually have important implications for clinical management of the whole child, taking into account not just seizures, but also adaptive functioning and quality of life. For several decades, we have accepted an evidence-free approach to using or not using antiepileptic drugs in IFEs. There is huge international variation and only a handful of studies examining neurocognitive outcomes. Clearly, this is a situation ready for an overhaul in practice. Fundamental to understanding treatment is knowledge of aetiology. In recent years, there have been several significant discoveries in IFEs from studies of copy number variation, exome sequencing, and linkage that prompt reconsideration of the "unknown cause" classification and strongly suggest a genetic aetiology. The IFE are strongly age-related, both with regards to age of seizure onset and remission. Does this time window solely relate to a similar age-related gene expression, or are there epigenetic factors involved that might also explain low observed twin concordance? The genetic (and epigenetic) models for different IFEs, their comorbidities, and their similarities to other neurodevelopmental disorders deserve investigation in the coming years. In so doing, we will probably learn much about normal brain functioning. This is because these disorders, perhaps more than any other human brain disease, are disorders of functional brain systems (even though these functional networks may not yet be fully defined). In June 2012, an international group of clinical and basic science researchers met in London under the auspices of the Waterloo Foundation to discuss and debate these issues in relation to IFEs. This Waterloo Foundation Symposium on the Idiopathic Focal Epilepsies: Phenotype to Genotype witnessed presentations that explored the clinical phenomenology, phenotypes and endophenotypes, and genetic approaches to investigation of these disorders. In parallel, the impact of these epilepsies on children and their families was reviewed. The papers in this supplement are based upon these presentations. They represent an updated state-of-the-art thinking on the topics explored. The symposium led to the formation of international working groups under the umbrella of "Luke's Idiopathic Focal Epilepsy Project" to investigate various aspects of the idiopathic focal epilepsies including: semiology and classification, genetics, cognition, sleep, high-frequency oscillations, and parental resources (see www.childhood-epilepsy.org). The next sponsored international workshop, in June 2014, was on randomised controlled trials in IFEs and overnight learning outcome measures.
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http://dx.doi.org/10.1684/epd.2016.0839DOI Listing
September 2016

STXBP1 encephalopathy: A neurodevelopmental disorder including epilepsy.

Neurology 2016 Mar 10;86(10):954-62. Epub 2016 Feb 10.

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

Objective: To give a comprehensive overview of the phenotypic and genetic spectrum of STXBP1 encephalopathy (STXBP1-E) by systematically reviewing newly diagnosed and previously reported patients.

Methods: We recruited newly diagnosed patients with STXBP1 mutations through an international network of clinicians and geneticists. Furthermore, we performed a systematic literature search to review the phenotypes of all previously reported patients.

Results: We describe the phenotypic features of 147 patients with STXBP1-E including 45 previously unreported patients with 33 novel STXBP1 mutations. All patients have intellectual disability (ID), which is mostly severe to profound (88%). Ninety-five percent of patients have epilepsy. While one-third of patients presented with Ohtahara syndrome (21%) or West syndrome (9.5%), the majority has a nonsyndromic early-onset epilepsy and encephalopathy (53%) with epileptic spasms or tonic seizures as main seizure type. We found no correlation between severity of seizures and severity of ID or between mutation type and seizure characteristics or cognitive outcome. Neurologic comorbidities including autistic features and movement disorders are frequent. We also report 2 previously unreported adult patients with prominent extrapyramidal features.

Conclusion: De novo STXBP1 mutations are among the most frequent causes of epilepsy and encephalopathy. Most patients have severe to profound ID with little correlation among seizure onset, seizure severity, and the degree of ID. Accordingly, we hypothesize that seizure severity and ID present 2 independent dimensions of the STXBP1-E phenotype. STXBP1-E may be conceptualized as a complex neurodevelopmental disorder rather than a primary epileptic encephalopathy.
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http://dx.doi.org/10.1212/WNL.0000000000002457DOI Listing
March 2016

The role of SLC2A1 mutations in myoclonic astatic epilepsy and absence epilepsy, and the estimated frequency of GLUT1 deficiency syndrome.

Epilepsia 2015 Dec 5;56(12):e203-8. Epub 2015 Nov 5.

Danish Epilepsy Center, Dianalund, Denmark.

The first mutations identified in SLC2A1, encoding the glucose transporter type 1 (GLUT1) protein of the blood-brain barrier, were associated with severe epileptic encephalopathy. Recently, dominant SLC2A1 mutations were found in rare autosomal dominant families with various forms of epilepsy including early onset absence epilepsy (EOAE), myoclonic astatic epilepsy (MAE), and genetic generalized epilepsy (GGE). Our study aimed to investigate the possible role of SLC2A1 in various forms of epilepsy including MAE and absence epilepsy with early onset. We also aimed to estimate the frequency of GLUT1 deficiency syndrome in the Danish population. One hundred twenty patients with MAE, 50 patients with absence epilepsy, and 37 patients with unselected epilepsies, intellectual disability (ID), and/or various movement disorders were screened for mutations in SLC2A1. Mutations in SLC2A1 were detected in 5 (10%) of 50 patients with absence epilepsy, and in one (2.7%) of 37 patient with unselected epilepsies, ID, and/or various movement disorders. None of the 120 MAE patients harbored SLC2A1 mutations. We estimated the frequency of SLC2A1 mutations in the Danish population to be approximately 1:83,000. Our study confirmed the role of SLC2A1 mutations in absence epilepsy with early onset. However, our study failed to support the notion that SLC2A1 aberrations are a cause of MAE without associated features such as movement disorders.
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http://dx.doi.org/10.1111/epi.13222DOI Listing
December 2015
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