SCN2A mutations and benign familial neonatal-infantile seizures: The phenotypic spectrum

The definitive version is available at www.blackwell-synergy.comSummary: Mutations of the sodium channel subunit gene SCN2A have been described in families with benign familial neonatal-infantile seizure (BFNIS). We describe two large families with BFNIS and novel SCN2A mutations. The families had 12 and 9 affected individuals, respectively, with phenotypes consistent with BFNIS. Two mutations were discovered in SCN2A (E430Q; I1596S). Both families had individuals with neonatal onset but the typical age of onset was in the early infantile period (mean 3.0 months). One mutation positive individual, with an otherwise typical clinical pattern, had seizures beginning at 13 months. Two individuals with SCN2A mutations were identified with seizures in later life. In each family a single individual with infantile seizures was mutation negative and thus represented phenocopies. This study extends the age range of presentation of BFNIS, confirms that neonatal and early infantile onsets are characteristic, and emphasizes the role of molecular diagnosis to confirm the etiology.Eric Herlenius, Sarah E. Heron, Bronwyn E. Grinton, Deborah Keay, Ingrid E. Scheffer, John C. Mulley, Samuel F. Berkovi

Novel mutations in the KCNQ2 gene link epilepsy to a dysfunction of the KCNQ2-calmodulin interaction

Copyright © 2004 by the BMJ Publishing Group Ltd.M C Richards, S E Heron, H E Spendlove, I E Scheffer, B Grinton, S F Berkovic, J C Mulley, A Dav

Investigation of the 15q13.3 CNV as a genetic modifier for familial epilepsies with variable phenotypes

Incomplete penetrance and variable phenotypic expression are characteristic of a number of syndromes of familial epilepsy. The purpose of the present investigation is to determine if the 15q13.3 copy number deletion functions as a locus modifying the epilepsy phenotype caused by other known or presumed pathogenic mutations segregating in families with epilepsies. No 15q13.3 microdeletions were detected in 756 affected or definite obligate carrier individuals across 151 families selected on the basis of having multiple members affected with epilepsy and showing a range of seizure types. Therefore, the 15q13.3 microdeletion does not act as a genetic modifier in this cohort of families and is not responsible for any of the genetic heterogeneity hypothesized to account for failure to detect linkage in previous genome-wide scans in five of the larger families included in this study.John C. Mulley, Ingrid E. Scheffer, Tarishi Desai, Marta A. Bayly, Bronwyn E. Grinton, Danya F. Vears, Samuel F. Berkovic, and Leanne M. Dibben

Novel MissenseCACNA1GMutations Associated with Infantile-Onset Developmental and Epileptic Encephalopathy

The CACNA1G gene encodes the low-voltage-activated Cav3.1 channel, which is expressed in various areas of the CNS, including the cerebellum. We studied two missense CACNA1G variants, p.L208P and p.L909F, and evaluated the relationships between the severity of Cav3.1 dysfunction and the clinical phenotype. The presentation was of a developmental and epileptic encephalopathy without evident cerebellar atrophy. Both patients exhibited axial hypotonia, developmental delay, and severe to profound cognitive impairment. The patient with the L909F mutation had initially refractory seizures and cerebellar ataxia, whereas the L208P patient had seizures only transiently but was overall more severely affected. In transfected mammalian cells, we determined the biophysical characteristics of L208P and L909F variants, relative to the wild-type channel and a previously reported gain-of-function Cav3.1 variant. The L208P mutation shifted the activation and inactivation curves to the hyperpolarized direction, slowed the kinetics of inactivation and deactivation, and reduced the availability of Ca2+ current during repetitive stimuli. The L909F mutation impacted channel function less severely, resulting in a hyperpolarizing shift of the activation curve and slower deactivation. These data suggest that L909F results in gain-of-function, whereas L208P exhibits mixed gain-of-function and loss-of-function effects due to opposing changes in the biophysical properties. Our study expands the clinical spectrum associated with CACNA1G mutations, corroborating further the causal association with distinct complex phenotype

The Health-related quality of life of childhood epilepsy syndromes

Objective: There is increasing awareness of the importance of assessing physical, psychological, social and behavioural well-being in chronic disease. The aim of this study was to examine the health-related quality of life (HRQoL) of children with common epilepsy syndromes and to explore if there are HRQoL differences between those syndromes. Methods: Each child had their epilepsy syndrome defined according to the International League Against Epilepsy classification. Epilepsy syndromes included symptomatic frontal, temporal, parietal/occipital lobe and partial unlocalized epilepsy, and two idiopathic epilepsies, childhood absence epilepsy (CAE) and benign rolandic epilepsy (BRE). Seizure semiology and ictal/interictal electroencephalogram (EEG) were determined for symptomatic partial epilepsy syndromes by video-EEG monitoring. HRQoL was evaluated with an epilepsy-specific instrument, the Quality of Life in Childhood Epilepsy Questionnaire, and two generic instruments, the Child Health Questionnaire and Child Behavior Checklist. Results: Children with symptomatic partial epilepsy syndromes were affected by epilepsy in a similar way and did not have unique HRQoL profiles. However, these children had significantly lower HRQoL scores compared to those with CAE or BRE. All children with epilepsy regardless of syndrome had a higher frequency of behavioural problems compared to normative data. Conclusion: These results indicate that children with epilepsy regardless of syndrome require evaluation of the psychosocial implications. There is a greater impact on HRQoL in symptomatic epilepsy compared to idiopathic epilepsy. Specific symptomatic partial syndromes did not differ in the degree they affect HRQoL. These findings have important implications for clinicians caring for children with epilepsy.7 page(s

In vivo loss of slow potassium channel activity in individuals with benign familial neonatal epilepsy in remission

Fulltext embargoed for: 12 months post date of publicationBenign familial neonatal epilepsy is a neuronal channelopathy most commonly caused by mutations in KCNQ2, which encodes the K(v)7.2 subunit of the slow K(+) channel. K(v)7.2 is expressed in both central and peripheral nervous systems. Seizures occur in the neonatal period, often in clusters within the first few days of life, and usually remit by 12 months of age. The mechanism of involvement of K(v)7.2 mutations in the process of seizure generation has not been established in vivo. In peripheral axons, K(v)7.2 contributes to the nodal slow K(+) current. The present study aimed to determine whether axonal excitability studies could detect changes in peripheral nerve function related to dysfunction or loss of slow potassium channel activity. Nerve excitability studies were performed on eight adults with KCNQ2 mutations and a history of benign familial neonatal epilepsy, now in remission. Studies detected distinctive changes in peripheral nerve, indicating a reduction in slow K(+) current. Specifically, accommodation to long-lasting depolarizing currents was reduced in mutation carriers by 24% compared with normal controls, and the threshold undershoot after 100 ms depolarizing currents was reduced by 22%. Additional changes in excitability included a reduction in the relative refractory period, an increase in superexcitability and a tendency towards reduced sub-excitability. Modelling of the nerve excitability changes suggested that peripheral nerve hyperexcitability may have been ameliorated by upregulation of other potassium channels. We conclude that subclinical dysfunction of K(v)7.2 in peripheral axons can be reliably detected non-invasively in adulthood. Related alterations in neuronal excitability may contribute to epilepsy associated with KCNQ2 mutations

The Polarity Sensitivity Factor (PSF) of some Fluorescent Probe Molecules Used for Studying Supramolecular Systems and other Heterogeneous Environments

Fluorescence spectroscopy provides an excellent technique for investigating heterogeneous systems, due to its high sensitivity and the large effect of the local environment on molecular emission. In addition, the use of polarity-sensitive fluorescent probes as guests in supramolecular host-guest inclusion complexes can be exploited in fluorescent sensors. This paper identifies, tabulates, and quantifies a series of useful polarity-sensitive fluorescent probes, with a wide range of polarity-dependent fluorescence responses. The degree of polarity sensitivity is quantified using the Polarity Sensitivity Factor (PSF), developed in our laboratory. In most cases, such polarity-sensitive probes show increased emission as the local polarity is decreased (PSF>1); ten such probes are described. However, less commonly, â reverse polarity dependenceâ can occur in which probe emission decreases with decreasing polarity (PSFThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Deletions or duplications in KCNQ2 can cause benign familial neonatal seizures

Copyright © 2007 by the BMJ Publishing Group Ltd.Background: Benign familial neonatal seizures are most often caused by mutations in the voltage-gated potassium channel subunit gene KCNQ2. More than 60 mutations have been described in BFNS families, approximately half of which lead to protein truncation. The hypothesis of this study was that deletion or duplication of 1 exons of KCNQ2 could cause BFNS in cases without coding or splicing mutations. Methods: Multiplex ligation-dependent probe amplification (MLPA) was used to test a group of 21 unrelated patients with clinical features consistent with either BFNS, benign familial neonatal–infantile seizures or sporadic neonatal seizures, for exonic deletions and duplications. Results: Three deletions and one duplication mutation were identified in four familial cases and cascade testing of their available family members showed that the mutations segregated with the phenotype in each family. The junction fragment for one of the deletions was amplified by PCR and sequenced to characterise the breakpoint and verify that a deletion had occurred. Conclusions: Submicroscopic deletions or duplications of KCNQ2 are seen in a significant proportion of BFNS families: four of nine (44%) cases previously testing negative for coding or splice site mutation by sequencing KCNQ2 and KCNQ3. MLPA is an efficient second-tier testing strategy for KCNQ2 to identify pathogenic intragenic mutations not detectable by conventional DNA sequencing methods.S E Heron, K Cox, B E Grinton, S M Zuberi, S Kivity, Z Afawi, R Straussberg, S F Berkovic, I E Scheffer and J C Mulle