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1.
Hum Mutat ; 2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31513310

RESUMO

Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with early-onset DEE. KCNB1 encodes the alpha subunit of the delayed-rectifier voltage-dependent potassium channel Kv 2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of Kv 2.1. We also report the first inherited variant (p.Arg583*). KCNB1-related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty-five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C-terminal domain are associated with a less severe epileptic phenotype. Overall, this report provides an up-to-date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms. This article is protected by copyright. All rights reserved.

2.
Epilepsy Res ; 156: 106181, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31394400

RESUMO

Infantile spasms (IS) is a developmental and epileptic encephalopathy with heterogeneous etiologies including many genetic causes. Genetic studies have identified pathogenic variants in over 30 genes as causes of IS. Many of these genetic causes are extremely rare, with only one reported incidence in an individual with IS. To better understand the genetic landscape of IS, we used targeted sequencing to screen 42 candidate IS genes and 53 established developmental and epileptic encephalopathy genes in 92 individual with IS. We identified a genetic diagnosis for 7.6% of our cohort, including pathogenic variants in KCNB1 (n = 2), GNAO1 (n = 1), STXBP1 (n = 1), SLC35A2 (n = 1), TBL1XR1 (n = 1), and KIF1A (n = 1). Our data emphasize the genetic heterogeneity of IS and will inform the diagnosis and management of individuals with this devastating disorder.

4.
Hum Mutat ; 40(4): 374-379, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30556619

RESUMO

Rapid advances in genomic technologies have facilitated the identification pathogenic variants causing human disease. We report siblings with developmental and epileptic encephalopathy due to a novel, shared heterozygous pathogenic 13 bp duplication in SYNGAP1 (c.435_447dup, p.(L150Vfs*6)) that was identified by whole genome sequencing (WGS). The pathogenic variant had escaped earlier detection via two methodologies: whole exome sequencing and high-depth targeted sequencing. Both technologies had produced reads carrying the variant, however, they were either not aligned due to the size of the insertion or aligned to multiple major histocompatibility complex (MHC) regions in the hg19 reference genome, making the critical reads unavailable for variant calling. The WGS pipeline followed different protocols, including alignment of reads to the GRCh37 reference genome, which lacks the additional MHC contigs. Our findings highlight the benefit of using orthogonal clinical bioinformatic pipelines and all relevant inheritance patterns to re-analyze genomic data in undiagnosed patients.

5.
Am J Hum Genet ; 104(1): 35-44, 2019 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-30554721

RESUMO

Baratela-Scott syndrome (BSS) is a rare, autosomal-recessive disorder characterized by short stature, facial dysmorphisms, developmental delay, and skeletal dysplasia caused by pathogenic variants in XYLT1. We report clinical and molecular investigation of 10 families (12 individuals) with BSS. Standard sequencing methods identified biallelic pathogenic variants in XYLT1 in only two families. Of the remaining cohort, two probands had no variants and six probands had only a single variant, including four with a heterozygous 3.1 Mb 16p13 deletion encompassing XYLT1 and two with a heterozygous truncating variant. Bisulfite sequencing revealed aberrant hypermethylation in exon 1 of XYLT1, always in trans with the sequence variant or deletion when present; both alleles were methylated in those with no identified variant. Expression of the methylated XYLT1 allele was severely reduced in fibroblasts from two probands. Southern blot studies combined with repeat expansion analysis of genome sequence data showed that the hypermethylation is associated with expansion of a GGC repeat in the XYLT1 promoter region that is not present in the reference genome, confirming that BSS is a trinucleotide repeat expansion disorder. The hypermethylated allele accounts for 50% of disease alleles in our cohort and is not present in 130 control subjects. Our study highlights the importance of investigating non-sequence-based alterations, including epigenetic changes, to identify the missing heritability in genetic disorders.

6.
Neurology ; 92(2): e96-e107, 2019 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-30541864

RESUMO

OBJECTIVE: To delineate the epileptology, a key part of the SYNGAP1 phenotypic spectrum, in a large patient cohort. METHODS: Patients were recruited via investigators' practices or social media. We included patients with (likely) pathogenic SYNGAP1 variants or chromosome 6p21.32 microdeletions incorporating SYNGAP1. We analyzed patients' phenotypes using a standardized epilepsy questionnaire, medical records, EEG, MRI, and seizure videos. RESULTS: We included 57 patients (53% male, median age 8 years) with SYNGAP1 mutations (n = 53) or microdeletions (n = 4). Of the 57 patients, 56 had epilepsy: generalized in 55, with focal seizures in 7 and infantile spasms in 1. Median seizure onset age was 2 years. A novel type of drop attack was identified comprising eyelid myoclonia evolving to a myoclonic-atonic (n = 5) or atonic (n = 8) seizure. Seizure types included eyelid myoclonia with absences (65%), myoclonic seizures (34%), atypical (20%) and typical (18%) absences, and atonic seizures (14%), triggered by eating in 25%. Developmental delay preceded seizure onset in 54 of 56 (96%) patients for whom early developmental history was available. Developmental plateauing or regression occurred with seizures in 56 in the context of a developmental and epileptic encephalopathy (DEE). Fifty-five of 57 patients had intellectual disability, which was moderate to severe in 50. Other common features included behavioral problems (73%); high pain threshold (72%); eating problems, including oral aversion (68%); hypotonia (67%); sleeping problems (62%); autism spectrum disorder (54%); and ataxia or gait abnormalities (51%). CONCLUSIONS: SYNGAP1 mutations cause a generalized DEE with a distinctive syndrome combining epilepsy with eyelid myoclonia with absences and myoclonic-atonic seizures, as well as a predilection to seizures triggered by eating.

7.
Am J Hum Genet ; 103(5): 666-678, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30343943

RESUMO

Developmental and epileptic encephalopathies (DEEs) are severe neurodevelopmental disorders often beginning in infancy or early childhood that are characterized by intractable seizures, abundant epileptiform activity on EEG, and developmental impairment or regression. CACNA1E is highly expressed in the central nervous system and encodes the α1-subunit of the voltage-gated CaV2.3 channel, which conducts high voltage-activated R-type calcium currents that initiate synaptic transmission. Using next-generation sequencing techniques, we identified de novo CACNA1E variants in 30 individuals with DEE, characterized by refractory infantile-onset seizures, severe hypotonia, and profound developmental impairment, often with congenital contractures, macrocephaly, hyperkinetic movement disorders, and early death. Most of the 14, partially recurring, variants cluster within the cytoplasmic ends of all four S6 segments, which form the presumed CaV2.3 channel activation gate. Functional analysis of several S6 variants revealed consistent gain-of-function effects comprising facilitated voltage-dependent activation and slowed inactivation. Another variant located in the domain II S4-S5 linker results in facilitated activation and increased current density. Five participants achieved seizure freedom on the anti-epileptic drug topiramate, which blocks R-type calcium channels. We establish pathogenic variants in CACNA1E as a cause of DEEs and suggest facilitated R-type calcium currents as a disease mechanism for human epilepsy and developmental disorders.

8.
Am J Hum Genet ; 103(2): 305-316, 2018 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-30057029

RESUMO

Next-generation sequencing combined with international data sharing has enormously facilitated identification of new disease-associated genes and mutations. This is particularly true for genetically extremely heterogeneous entities such as neurodevelopmental disorders (NDDs). Through exome sequencing and world-wide collaborations, we identified and assembled 20 individuals with de novo variants in FBXO11. They present with mild to severe developmental delay associated with a range of features including short (4/20) or tall (2/20) stature, obesity (5/20), microcephaly (4/19) or macrocephaly (2/19), behavioral problems (17/20), seizures (5/20), cleft lip or palate or bifid uvula (3/20), and minor skeletal anomalies. FBXO11 encodes a member of the F-Box protein family, constituting a subunit of an E3-ubiquitin ligase complex. This complex is involved in ubiquitination and proteasomal degradation and thus in controlling critical biological processes by regulating protein turnover. The identified de novo aberrations comprise two large deletions, ten likely gene disrupting variants, and eight missense variants distributed throughout FBXO11. Structural modeling for missense variants located in the CASH or the Zinc-finger UBR domains suggests destabilization of the protein. This, in combination with the observed spectrum and localization of identified variants and the lack of apparent genotype-phenotype correlations, is compatible with loss of function or haploinsufficiency as an underlying mechanism. We implicate de novo missense and likely gene disrupting variants in FBXO11 in a neurodevelopmental disorder with variable intellectual disability and various other features.

9.
Epilepsia ; 59(6): 1177-1187, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29750358

RESUMO

OBJECTIVE: The severe epilepsies of infancy (SEI) are a devastating group of disorders that pose a major care and economic burden on society; early diagnosis is critical for optimal management. This study sought to determine the incidence and etiologies of SEI, and model the yield and cost-effectiveness of early genetic testing. METHODS: A population-based study was undertaken of the incidence, etiologies, and cost-effectiveness of a whole exome sequencing-based gene panel (targeted WES) in infants with SEI born during 2011-2013, identified through electroencephalography (EEG) and neonatal databases. SEI was defined as seizure onset before age 18 months, frequent seizures, epileptiform EEG, and failure of ≥2 antiepileptic drugs. Medical records, investigations, MRIs, and EEGs were analyzed, and genetic testing was performed if no etiology was identified. Economic modeling was performed to determine yield and cost-effectiveness of investigation of infants with unknown etiology at epilepsy onset, incorporating targeted WES at different stages of the diagnostic pathway. RESULTS: Of 114 infants with SEI (incidence = 54/100 000 live births/y), the etiology was determined in 76 (67%): acquired brain injuries (n = 14), focal cortical dysplasias (n = 14), other brain malformations (n = 17), channelopathies (n = 11), chromosomal (n = 9), metabolic (n = 6), and other genetic (n = 5) disorders. Modeling showed that incorporating targeted WES increased diagnostic yield compared to investigation without targeted WES (48/86 vs 39/86). Early targeted WES had lower total cost ($677 081 U.S. dollars [USD] vs $738 136 USD) than late targeted WES. A pathway with early targeted WES and limited metabolic testing yielded 7 additional diagnoses compared to investigation without targeted WES (46/86 vs 39/86), with lower total cost ($455 597 USD vs $661 103 USD), lower cost per diagnosis ($9904 USD vs $16 951 USD), and a dominant cost-effectiveness ratio. SIGNIFICANCE: Severe epilepsies occur in 1 in 2000 infants, with the etiology identified in two-thirds, most commonly malformative. Early use of targeted WES yields more diagnoses at lower cost. Early genetic diagnosis will enable timely administration of precision medicines, once developed, with the potential to improve long-term outcome.

10.
Genet Med ; 20(11): 1354-1364, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29671837

RESUMO

PURPOSE: To estimate diagnostic yield and genotype-phenotype correlations in a cohort of 811 patients with lissencephaly or subcortical band heterotopia. METHODS: We collected DNA from 756 children with lissencephaly over 30 years. Many were tested for deletion 17p13.3 and mutations of LIS1, DCX, and ARX, but few other genes. Among those tested, 216 remained unsolved and were tested by a targeted panel of 17 genes (ACTB, ACTG1, ARX, CRADD, DCX, LIS1, TUBA1A, TUBA8, TUBB2B, TUBB, TUBB3, TUBG1, KIF2A, KIF5C, DYNC1H1, RELN, and VLDLR) or by whole-exome sequencing. Fifty-five patients studied at another institution were added as a validation cohort. RESULTS: The overall mutation frequency in the entire cohort was 81%. LIS1 accounted for 40% of patients, followed by DCX (23%), TUBA1A (5%), and DYNC1H1 (3%). Other genes accounted for 1% or less of patients. Nineteen percent remained unsolved, which suggests that several additional genes remain to be discovered. The majority of unsolved patients had posterior pachygyria, subcortical band heterotopia, or mild frontal pachygyria. CONCLUSION: The brain-imaging pattern correlates with mutations in single lissencephaly-associated genes, as well as in biological pathways. We propose the first LIS classification system based on the underlying molecular mechanisms.

12.
Epilepsia ; 59(2): 389-402, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29315614

RESUMO

OBJECTIVE: Pathogenic SLC6A1 variants were recently described in patients with myoclonic atonic epilepsy (MAE) and intellectual disability (ID). We set out to define the phenotypic spectrum in a larger cohort of SCL6A1-mutated patients. METHODS: We collected 24 SLC6A1 probands and 6 affected family members. Four previously published cases were included for further electroclinical description. In total, we reviewed the electroclinical data of 34 subjects. RESULTS: Cognitive development was impaired in 33/34 (97%) subjects; 28/34 had mild to moderate ID, with language impairment being the most common feature. Epilepsy was diagnosed in 31/34 cases with mean onset at 3.7 years. Cognitive assessment before epilepsy onset was available in 24/31 subjects and was normal in 25% (6/24), and consistent with mild ID in 46% (11/24) or moderate ID in 17% (4/24). Two patients had speech delay only, and 1 had severe ID. After epilepsy onset, cognition deteriorated in 46% (11/24) of cases. The most common seizure types were absence, myoclonic, and atonic seizures. Sixteen cases fulfilled the diagnostic criteria for MAE. Seven further patients had different forms of generalized epilepsy and 2 had focal epilepsy. Twenty of 31 patients became seizure-free, with valproic acid being the most effective drug. There was no clear-cut correlation between seizure control and cognitive outcome. Electroencephalography (EEG) findings were available in 27/31 patients showing irregular bursts of diffuse 2.5-3.5 Hz spikes/polyspikes-and-slow waves in 25/31. Two patients developed an EEG pattern resembling electrical status epilepticus during sleep. Ataxia was observed in 7/34 cases. We describe 7 truncating and 18 missense variants, including 4 recurrent variants (Gly232Val, Ala288Val, Val342Met, and Gly362Arg). SIGNIFICANCE: Most patients carrying pathogenic SLC6A1 variants have an MAE phenotype with language delay and mild/moderate ID before epilepsy onset. However, ID alone or associated with focal epilepsy can also be observed.


Assuntos
Epilepsias Mioclônicas/fisiopatologia , Proteínas da Membrana Plasmática de Transporte de GABA/genética , Deficiência Intelectual/fisiopatologia , Transtornos do Desenvolvimento da Linguagem/fisiopatologia , Adolescente , Adulto , Anticonvulsivantes/uso terapêutico , Ataxia/complicações , Ataxia/genética , Ataxia/fisiopatologia , Criança , Pré-Escolar , Estudos de Coortes , Eletroencefalografia , Epilepsias Mioclônicas/complicações , Epilepsias Mioclônicas/tratamento farmacológico , Epilepsias Mioclônicas/genética , Epilepsias Parciais/complicações , Epilepsias Parciais/tratamento farmacológico , Epilepsias Parciais/genética , Epilepsias Parciais/fisiopatologia , Epilepsia Generalizada/complicações , Epilepsia Generalizada/tratamento farmacológico , Epilepsia Generalizada/genética , Epilepsia Generalizada/fisiopatologia , Feminino , Estudos de Associação Genética , Humanos , Deficiência Intelectual/complicações , Deficiência Intelectual/genética , Transtornos do Desenvolvimento da Linguagem/complicações , Transtornos do Desenvolvimento da Linguagem/genética , Masculino , Mutação , Mutação de Sentido Incorreto , Transtornos do Neurodesenvolvimento/complicações , Transtornos do Neurodesenvolvimento/genética , Fenótipo , Resultado do Tratamento , Ácido Valproico/uso terapêutico , Adulto Jovem
14.
Am J Hum Genet ; 101(5): 664-685, 2017 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-29100083

RESUMO

Developmental and epileptic encephalopathy (DEE) is a group of conditions characterized by the co-occurrence of epilepsy and intellectual disability (ID), typically with developmental plateauing or regression associated with frequent epileptiform activity. The cause of DEE remains unknown in the majority of cases. We performed whole-genome sequencing (WGS) in 197 individuals with unexplained DEE and pharmaco-resistant seizures and in their unaffected parents. We focused our attention on de novo mutations (DNMs) and identified candidate genes containing such variants. We sought to identify additional subjects with DNMs in these genes by performing targeted sequencing in another series of individuals with DEE and by mining various sequencing datasets. We also performed meta-analyses to document enrichment of DNMs in candidate genes by leveraging our WGS dataset with those of several DEE and ID series. By combining these strategies, we were able to provide a causal link between DEE and the following genes: NTRK2, GABRB2, CLTC, DHDDS, NUS1, RAB11A, GABBR2, and SNAP25. Overall, we established a molecular diagnosis in 63/197 (32%) individuals in our WGS series. The main cause of DEE in these individuals was de novo point mutations (53/63 solved cases), followed by inherited mutations (6/63 solved cases) and de novo CNVs (4/63 solved cases). De novo missense variants explained a larger proportion of individuals in our series than in other series that were primarily ascertained because of ID. Moreover, these DNMs were more frequently recurrent than those identified in ID series. These observations indicate that the genetic landscape of DEE might be different from that of ID without epilepsy.


Assuntos
Encefalopatias/genética , Epilepsia/genética , Mutação/genética , Criança , Pré-Escolar , Feminino , Genoma Humano/genética , Estudo de Associação Genômica Ampla/métodos , Humanos , Deficiência Intelectual/genética , Masculino , Recidiva , Convulsões/genética
15.
Am J Hum Genet ; 101(4): 516-524, 2017 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-28942967

RESUMO

Exome sequencing has readily enabled the discovery of the genetic mutations responsible for a wide range of diseases. This success has been particularly remarkable in the severe epilepsies and other neurodevelopmental diseases for which rare, often de novo, mutations play a significant role in disease risk. Despite significant progress, the high genetic heterogeneity of these disorders often requires large sample sizes to identify a critical mass of individuals with disease-causing mutations in a single gene. By pooling genetic findings across multiple studies, we have identified six individuals with severe developmental delay (6/6), refractory seizures (5/6), and similar dysmorphic features (3/6), each harboring a de novo mutation in PPP3CA. PPP3CA encodes the alpha isoform of a subunit of calcineurin. Calcineurin encodes a calcium- and calmodulin-dependent serine/threonine protein phosphatase that plays a role in a wide range of biological processes, including being a key regulator of synaptic vesicle recycling at nerve terminals. Five individuals with de novo PPP3CA mutations were identified among 4,760 trio probands with neurodevelopmental diseases; this is highly unlikely to occur by chance (p = 1.2 × 10-8) given the size and mutability of the gene. Additionally, a sixth individual with a de novo mutation in PPP3CA was connected to this study through GeneMatcher. Based on these findings, we securely implicate PPP3CA in early-onset refractory epilepsy and further support the emerging role for synaptic dysregulation in epilepsy.


Assuntos
Calcineurina/genética , Epilepsia/genética , Mutação , Transtornos do Neurodesenvolvimento/genética , Transmissão Sináptica/fisiologia , Adolescente , Adulto , Calcineurina/metabolismo , Criança , Pré-Escolar , Estudos de Coortes , Epilepsia/patologia , Exoma/genética , Feminino , Humanos , Lactente , Recém-Nascido , Síndrome de Lennox Gastaut/patologia , Masculino , Transtornos do Neurodesenvolvimento/patologia , Análise de Sequência de DNA , Índice de Gravidade de Doença , Espasmos Infantis/genética , Espasmos Infantis/patologia , Adulto Jovem
16.
Neurology ; 89(10): 1035-1042, 2017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28794249

RESUMO

OBJECTIVE: To define a distinct SCN1A developmental and epileptic encephalopathy with early onset, profound impairment, and movement disorder. METHODS: A case series of 9 children were identified with a profound developmental and epileptic encephalopathy and SCN1A mutation. RESULTS: We identified 9 children 3 to 12 years of age; 7 were male. Seizure onset was at 6 to 12 weeks with hemiclonic seizures, bilateral tonic-clonic seizures, or spasms. All children had profound developmental impairment and were nonverbal and nonambulatory, and 7 of 9 required a gastrostomy. A hyperkinetic movement disorder occurred in all and was characterized by dystonia and choreoathetosis with prominent oral dyskinesia and onset from 2 to 20 months of age. Eight had a recurrent missense SCN1A mutation, p.Thr226Met. The remaining child had the missense mutation p.Pro1345Ser. The mutation arose de novo in 8 of 9; for the remaining case, the mother was negative and the father was unavailable. CONCLUSIONS: Here, we present a phenotype-genotype correlation for SCN1A. We describe a distinct SCN1A phenotype, early infantile SCN1A encephalopathy, which is readily distinguishable from the well-recognized entities of Dravet syndrome and genetic epilepsy with febrile seizures plus. This disorder has an earlier age at onset, profound developmental impairment, and a distinctive hyperkinetic movement disorder, setting it apart from Dravet syndrome. Remarkably, 8 of 9 children had the recurrent missense mutation p.Thr226Met.


Assuntos
Deficiências do Desenvolvimento/genética , Epilepsia/genética , Hipercinese/genética , Mutação de Sentido Incorreto , Canal de Sódio Disparado por Voltagem NAV1.1/genética , Idade de Início , Encéfalo/diagnóstico por imagem , Encéfalo/fisiopatologia , Criança , Pré-Escolar , Deficiências do Desenvolvimento/diagnóstico por imagem , Deficiências do Desenvolvimento/fisiopatologia , Epilepsias Mioclônicas/genética , Epilepsias Mioclônicas/fisiopatologia , Epilepsia/diagnóstico por imagem , Epilepsia/fisiopatologia , Feminino , Humanos , Hipercinese/diagnóstico por imagem , Hipercinese/fisiopatologia , Masculino , Fenótipo
17.
J Med Genet ; 54(7): 460-470, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28377535

RESUMO

BACKGROUND: We aimed for a comprehensive delineation of genetic, functional and phenotypic aspects of GRIN2B encephalopathy and explored potential prospects of personalised medicine. METHODS: Data of 48 individuals with de novo GRIN2B variants were collected from several diagnostic and research cohorts, as well as from 43 patients from the literature. Functional consequences and response to memantine treatment were investigated in vitro and eventually translated into patient care. RESULTS: Overall, de novo variants in 86 patients were classified as pathogenic/likely pathogenic. Patients presented with neurodevelopmental disorders and a spectrum of hypotonia, movement disorder, cortical visual impairment, cerebral volume loss and epilepsy. Six patients presented with a consistent malformation of cortical development (MCD) intermediate between tubulinopathies and polymicrogyria. Missense variants cluster in transmembrane segments and ligand-binding sites. Functional consequences of variants were diverse, revealing various potential gain-of-function and loss-of-function mechanisms and a retained sensitivity to the use-dependent blocker memantine. However, an objectifiable beneficial treatment response in the respective patients still remains to be demonstrated. CONCLUSIONS: In addition to previously known features of intellectual disability, epilepsy and autism, we found evidence that GRIN2B encephalopathy is also frequently associated with movement disorder, cortical visual impairment and MCD revealing novel phenotypic consequences of channelopathies.


Assuntos
Encefalopatias/genética , Mutação/genética , Receptores de N-Metil-D-Aspartato/genética , Encefalopatias/tratamento farmacológico , Heterozigoto , Humanos , Imagem por Ressonância Magnética , Memantina/uso terapêutico , Terapia de Alvo Molecular , Neuroimagem , Fenótipo , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo
18.
Neurology ; 88(5): 483-492, 2017 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-28053010

RESUMO

OBJECTIVE: To examine the role of mutations in GABRB3 encoding the ß3 subunit of the GABAA 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 ß3, together with α5 and γ2s 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.


Assuntos
Epilepsia/genética , Mutação , Receptores de GABA-A/genética , Animais , Automação Laboratorial , Criança , Pré-Escolar , Estudos de Coortes , Epilepsia/fisiopatologia , Feminino , Heterozigoto , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Lactente , Recém-Nascido , Masculino , Potenciais da Membrana/fisiologia , Oócitos , Técnicas de Patch-Clamp , Fenótipo , Receptores de GABA-A/metabolismo , Xenopus laevis
19.
Neurology ; 87(19): 1975-1984, 2016 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-27733563

RESUMO

OBJECTIVE: To identify the genetic basis of a family segregating episodic ataxia, infantile seizures, and heterogeneous epilepsies and to study the phenotypic spectrum of KCNA2 mutations. METHODS: A family with 7 affected individuals over 3 generations underwent detailed phenotyping. Whole genome sequencing was performed on a mildly affected grandmother and her grandson with epileptic encephalopathy (EE). Segregating variants were filtered and prioritized based on functional annotations. The effects of the mutation on channel function were analyzed in vitro by voltage clamp assay and in silico by molecular modeling. KCNA2 was sequenced in 35 probands with heterogeneous phenotypes. RESULTS: The 7 family members had episodic ataxia (5), self-limited infantile seizures (5), evolving to genetic generalized epilepsy (4), focal seizures (2), and EE (1). They had a segregating novel mutation in the shaker type voltage-gated potassium channel KCNA2 (CCDS_827.1: c.765_773del; p.255_257del). A rare missense SCN2A (rs200884216) variant was also found in 2 affected siblings and their unaffected mother. The p.255_257del mutation caused dominant negative loss of channel function. Molecular modeling predicted repositioning of critical arginine residues in the voltage-sensing domain. KCNA2 sequencing revealed 1 de novo mutation (CCDS_827.1: c.890G>A; p.Arg297Gln) in a girl with EE, ataxia, and tremor. CONCLUSIONS: A KCNA2 mutation caused dominantly inherited episodic ataxia, mild infantile-onset seizures, and later generalized and focal epilepsies in the setting of normal intellect. This observation expands the KCNA2 phenotypic spectrum from EE often associated with chronic ataxia, reflecting the marked variation in severity observed in many ion channel disorders.


Assuntos
Anticonvulsivantes/uso terapêutico , Ataxia/genética , Epilepsia/tratamento farmacológico , Epilepsia/genética , Canal de Potássio Kv1.2/genética , Mutação/genética , Farmacogenética , Idoso , Animais , Criança , Pré-Escolar , Estudos de Coortes , Análise Mutacional de DNA , Saúde da Família , Feminino , Humanos , Lactente , Masculino , Potenciais da Membrana/genética , Pessoa de Meia-Idade , Modelos Químicos , Oócitos , Xenopus laevis , Adulto Jovem
20.
J Med Genet ; 53(12): 850-858, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27358180

RESUMO

BACKGROUND: Mutations in the KIAA2022 gene have been reported in male patients with X-linked intellectual disability, and related female carriers were unaffected. Here, we report 14 female patients who carry a heterozygous de novo KIAA2022 mutation and share a phenotype characterised by intellectual disability and epilepsy. METHODS: Reported females were selected for genetic testing because of substantial developmental problems and/or epilepsy. X-inactivation and expression studies were performed when possible. RESULTS: All mutations were predicted to result in a frameshift or premature stop. 12 out of 14 patients had intractable epilepsy with myoclonic and/or absence seizures, and generalised in 11. Thirteen patients had mild to severe intellectual disability. This female phenotype partially overlaps with the reported male phenotype which consists of more severe intellectual disability, microcephaly, growth retardation, facial dysmorphisms and, less frequently, epilepsy. One female patient showed completely skewed X-inactivation, complete absence of RNA expression in blood and a phenotype similar to male patients. In the six other tested patients, X-inactivation was random, confirmed by a non-significant twofold to threefold decrease of RNA expression in blood, consistent with the expected mosaicism between cells expressing mutant or normal KIAA2022 alleles. CONCLUSIONS: Heterozygous loss of KIAA2022 expression is a cause of intellectual disability in females. Compared with its hemizygous male counterpart, the heterozygous female disease has less severe intellectual disability, but is more often associated with a severe and intractable myoclonic epilepsy.


Assuntos
Epilepsia Resistente a Medicamentos/metabolismo , Mutação da Fase de Leitura , Deficiência Intelectual/metabolismo , Mosaicismo , Proteínas do Tecido Nervoso/genética , Inativação do Cromossomo X , Adolescente , Adulto , Criança , Pré-Escolar , Cromossomos Humanos X , Códon sem Sentido , Epilepsia Resistente a Medicamentos/genética , Feminino , Genes Ligados ao Cromossomo X , Heterozigoto , Humanos , Deficiência Intelectual/genética , Pessoa de Meia-Idade , Síndrome
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