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Open AccessJournal ArticleDOI

SCN1A duplications and deletions detected in Dravet syndrome: Implications for molecular diagnosis

TLDR
The type, frequency, and size of microchromosomal copy number variations affecting the neuronal sodium channel α 1 subunit gene (SCN1A) in Dravet syndrome, other epileptic encephalopathies, and generalized epilepsy with febrile seizures plus are determined.
Abstract
P>Objective:We aimed to determine the type, frequency, and size of microchromosomal copy number variations (CNVs) affecting the neuronal sodium channel alpha 1 subunit gene (SCN1A) in Dravet syndrome (DS), other epileptic encephalopathies, and generalized epilepsy with febrile seizures plus (GEFS+).Methods:Multiplex ligation-dependent probe amplification (MLPA) was applied to detect SCN1A CNVs among 289 cases (126 DS, 97 GEFS+, and 66 with other phenotypes). CNVs extending beyond SCN1A were further characterized by comparative genome hybridization (array CGH).Results:Novel SCN1A CNVs were found in 12.5% of DS patients where sequence-based mutations had been excluded. We identified the first partial SCN1A duplications in two siblings with typical DS and in a patient with early-onset symptomatic generalized epilepsy. In addition, a patient with DS had a partial SCN1A amplification of 5-6 copies. The remaining CNVs abnormalities were four partial and nine whole SCN1A deletions involving contiguous genes. Two CNVs (a partial SCN1A deletion and a duplication) were inherited from a parent, in whom there was mosaicism. Array CGH showed intragenic deletions of 90 kb and larger, with the largest of 9.3 Mb deleting 49 contiguous genes and extending beyond SCN1A.Discussion:Duplication and amplification involving SCN1A are now added to molecular mechanisms of DS patients. Our findings showed that 12.5% of DS patients who are mutation negative have MLPA-detected SCN1A CNVs with an overall frequency of about 2-3%. MLPA is the established second-line testing strategy to reliably detect all CNVs of SCN1A from the megabase range down to one exon. Large CNVs extending outside SCN1A and involving contiguous genes can be precisely characterized by array CGH.

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Etiological heterogeneity in autism spectrum disorders: More than 100 genetic and genomic disorders and still counting

TL;DR: An exhaustive review of the clinical genetics and research genetics literature in an attempt to collate all genes and recurrent genomic imbalances that have been implicated in the etiology of ASD shows that autism is not a single clinical entity but a behavioral manifestation of tens or perhaps hundreds of genetic and genomic disorders.
Journal ArticleDOI

NaV1.1 channels and epilepsy

TL;DR: A unified loss‐of‐function hypothesis for the spectrum of epilepsy syndromes caused by genetic changes in NaV1.1 channels is proposed, in which mild impairment predisposes to febrile seizures, intermediate impairment leads to GEFS+ epilepsy, and severe or complete loss of function leads to the intractable seizures and comorbidities of SMEI.
Journal ArticleDOI

Sodium channel SCN1A and epilepsy: mutations and mechanisms.

TL;DR: Results from mouse models suggest that the primary effect of both GEFS+ and DS mutations is to decrease the activity of GABAergic inhibitory neurons, and may be a general consequence of SCN1A mutations.
Journal ArticleDOI

Neurological perspectives on voltage-gated sodium channels

TL;DR: This review will outline the functions and roles of specific sodium channels in electrical signalling and disease, focusing on neurological aspects, and discuss recent advances in the development of selective sodium channel inhibitors.
Journal ArticleDOI

The genetics of Dravet syndrome

TL;DR: Dravet syndrome has a genetic etiology: between 70% and 80% of patients carry sodium channel α1 subunit gene (SCN1A) abnormalities, and truncating mutations account for about 40% and have a significant correlation with an earlier age of seizures onset.
References
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Journal ArticleDOI

Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification

TL;DR: A new method for relative quantification of 40 different DNA sequences in an easy to perform reaction requiring only 20 ng of human DNA is described.
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A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology.

TL;DR: A diagnostic scheme that makes use of standardized terminology and concepts to describe individual patients is proposed, and a variety of approaches to classification are possible, and some are presented here by way of example only.
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De novo mutations in the sodium-channel gene SCN1A cause severe myoclonic epilepsy of infancy.

TL;DR: Missense mutations in the gene that codes for a neuronal voltage-gated sodium-channel alpha-subunit (SCN1A) were identified in families with generalized epilepsy with febrile seizures plus (GEFS+) and seven unrelated patients with SMEI were screened for mutations.
Journal ArticleDOI

Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia

TL;DR: The data suggest that mutations in SCN9A cause primary erythermalgia, encoding a voltage-gated sodium channel alpha subunit predominantly expressed in sensory and sympathetic neurones, may play an important role in nociception and vasomotor regulation.
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