Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Idiopathic generalized epilepsies account for about 40% of epilepsy up to age 40 and commonly have a genetic basis. One type is benign familial neonatal convulsions (BFNC), a dominantly inherited disorder of newborns. We have identified a sub-microscopic deletion of chromosome 20q13.3 that co-segregates with seizures in a BFNC family. Characterization of cDNAs spanning the deleted region identified one encoding a novel voltage-gated potassium channel, KCNQ2, which belongs to a new KQT-like class of potassium channels. Five other BFNC probands were shown to have KCNQ2 mutations, including two transmembrane missense mutations, two frameshifts and one splice-site mutation. This finding in BFNC provides additional evidence that defects in potassium channels are involved in the mammalian epilepsy phenotype.
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PMID:A novel potassium channel gene, KCNQ2, is mutated in an inherited epilepsy of newborns. 942 86

Benign neonatal familial convulsions have been recognized as a distinctive epileptic syndrome since 1964. This rare epileptic syndrome was classified in the category of idiopathic generalized epilepsies. Recently, mutations of potassium channel genes (KCNQ2, KCNQ3) were identified as responsible for this autosomic dominant epileptic syndrome. Generalized tonico-clonic seizures start at the second or third day after birth in children with no prenatal or perinatal pathological history. Interictal EEG is normal. This epilepsy is age-dependent: less than ten percent of children present seizures later in life. Despite their rarity, BNFC represent a useful model to understand the pathophysiology of idiopathic age dependant epilepsies.
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PMID:[Benign familial neonatal convulsions: a model of idiopathic epilepsy]. 1047 60

Benign familial neonatal convulsions (BFNC) is a rare dominantly inherited epileptic syndrome characterized by frequent brief seizures within the first days of life. The disease is caused by mutations in one of two recently identified voltage-gated potassium channel genes, KCNQ2 or KCNQ3. Here, we describe a four-generation BFNC family carrying a novel mutation within the distal, unconserved C-terminal domain of KCNQ2, a 1-bp deletion, 2513delG, in codon 838 predicting substitution of the last seven and extension by another 56 amino acids. Three family members suffering from febrile but not from neonatal convulsions do not carry the mutation, confirming that febrile convulsions and BFNC are of different pathogenesis. Functional expression of the mutant channel in Xenopus oocytes revealed a reduction of the potassium current to 5% of the wild-type current, but the voltage sensitivity and kinetics were not significantly changed. To find out whether the loss of the last seven amino acids or the C-terminal extension because of 2513delG causes the phenotype, a second, artificial mutation was constructed yielding a stop codon at position 838. This truncation increased the potassium current by twofold compared with the wild type, indicating that the pathological extension produces the phenotype, and suggesting an important role of the distal, unconserved C-terminal domain of this channel. Our results indicate that BFNC is caused by a decreased potassium current impairing repolarization of the neuronal cell membrane, which results in hyperexcitability of the central nervous system.
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PMID:A reduced K+ current due to a novel mutation in KCNQ2 causes neonatal convulsions. 1048 60

Potassium channels play a critical role in limiting neuronal excitability. Mutations in certain voltage-gated potassium channels have been associated with hyperexcitable phenotypes in both humans and animals. However, only recently have mutations in potassium channel genes (i.e. KCNQ2 and KCNQ3) been discovered in a human epilepsy, benign familial neonatal convulsions. Recently, it has been reported that mice lacking the voltage-gated Shaker-like potassium channel Kv1.1 alpha-subunit develop recurrent spontaneous seizures early in postnatal development. The clinical relevance of the Kv1.1 knockout mouse has been underscored by a recent report of epilepsy occurring in a family affected by mutations in the KCNA1 locus (the human homologue of Kv1.1) which typically cause episodic ataxia and myokymia. Here we summarize preliminary studies characterizing the developmental changes in seizure susceptibility and neuronal activation in the three genotypes of Kv1.1 mice (-/-, +/-, +/+). Using behavioral and immediate-early gene indicators of regional brain excitability, we have found that a seizure-sensitive predisposition exists in Kv1.1 -/- animals at a very young age (P10), before either spontaneous seizure activity or changes in c-fos mRNA expression can be demonstrated. Kv1.1 +/- mice, although behaviorally indistinguishable from wild types, also have an increased susceptibility to seizures at a similar early age. The Kv1. 1 knockout mouse possesses many features desirable in a developmental animal epilepsy model and represents a clinically relevant model of early-onset epilepsies.
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PMID:Developmental seizure susceptibility of kv1.1 potassium channel knockout mice. 1057 55

Major advances in the identification of genetic loci and genes that predispose individuals to epilepsy have been made in the last several years. Two main themes for human, idiopathic epilepsies are emerging; genetic, or locus heterogeneity is not uncommon, and the discovery that epilepsy susceptibility genes are voltage-gated and ligand-gated ion channels. Knowledge that more than a single genetic locus is responsible for a single seizure type, along with a wide spectrum of disease mutations among families will complicate clinical, diagnostic issues. Disease gene identification, such as the two potassium ion channels (KCNQ2 and KCNQ3) for the two forms of benign familial neonatal seizures (BFNC) and the alpha4 subunit of the nicotinic receptor for autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), however, should yield significant advances in drug discoveries. Understanding the primary defect in inherited epilepsies provides for specific protein and pathway targets for potential drug intervention.
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PMID:Susceptibility genes in human epilepsy. 1071 62

Benign familial neonatal convulsions (BFNC) are one of the rare idiopathic epilepsies with autosomal dominant mode of inheritance. Two voltage-gated potassium channels, KCNQ2 on chromosome 20q13.3 and KCNQ3 on 8q24, have been recently identified as the genes responsible for BFNC. Here we describe a large family with BFNC in which we found a previously undescribed mutation in the KCNQ2 gene. A 1187(+2)T/G nucleotide exchange affects the conserved donor splice site motif in intron 9. This mutation can be predicted to give rise to aberrant splicing of the primary transcript. There was a wide range of clinical manifestations in this family. An unusual clinical feature is the occurrence of partial seizures in later life with corresponding focal neurological deficits.
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PMID:A KCNQ2 splice site mutation causing benign neonatal convulsions in a Scottish family. 1077 89

Benign familial neonatal convulsion (BFNC) is a common idiopathic epilepsy with autosomal dominant inheritance. Recently, two novel voltage-dependent potassium channel genes, KCNQ2 and KCNQ3, were identified by positional cloning as being responsible for BFNC. Heterotetramers of the products of these genes form M-channels and regulate the threshold of electrical excitability of neurons. We disrupted the mouse KCNQ2 gene via gene targeting to study the relationship between KCNQ2 and epilepsy. Homozygous pups (KCNQ2 -/-) died within a few hours after birth owing to pulmonary atelectasis that was not due to the status of epileptic seizures, although their development was morphologically normal. Heterozygous mice had decreased expression of KCNQ2 and showed hypersensitivity to pentylenetetrazole, an inducer of seizure. These data indicate that the decreased expression of KCNQ2 might cause a hyperexcitability of the CNS, which accounts for the mechanism of BFNC.
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PMID:Disruption of the epilepsy KCNQ2 gene results in neural hyperexcitability. 1085 43

In 1998, mutations in the voltage gated potassium channel gene KCNQ2 were found to be the main cause underlying the autosomal dominant inherited syndrome of benign familial neonatal convulsions (BFNC). In one BFNC family a mutation was found in an homologous gene, KCNQ3. We have now identified another brain-expressed member of this ion channel subfamily, KCNQ5, which maps to chromosome 6q14. On the genomic level KCNQ5 is composed of 14 exons, which are coding for 897 amino acid residues. Mutation analysis made KCNQ5 unlikely as a candidate gene for benign neonatal convulsions in patients with a positive family history for neonatal or early infantile seizures, but without mutations in the KCNQ2 or KCNQ3 genes.
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PMID:The new voltage gated potassium channel KCNQ5 and neonatal convulsions. 1088 71

A genetic contribution to aetiology is estimated to be present in up to 40% of patients with epilepsy. It is useful to categorise genetic epilepsies according to the mechanisms of inheritance into Mendelian disorders, non-mendelian or 'complex' disorders, and chromosomal disorders. Over 200 Mendelian diseases include epilepsy as part of the phenotype, and the genes for a number of these have been identified recently. These include autosomal recessive progressive myoclonic epilepsies such as Unverricht-Lundborg disease, Lafora disease and the neuronal ceroid lipofuscinoses, and three autosomal dominant idiopathic epilepsies. The last named have been shown to arise from mutations in ion channel genes. Autosomal dominant nocturnal frontal lobe epilepsy is caused by mutations in CHRNA4, benign familial neonatal convulsions by mutations in KCNQ2 and KCNQ3, and generalised epilepsy with febrile seizures plus by mutations in SCN1B. 'Complex', familial epilepsies are more difficult to analyse, but evidence has been obtained for loci predisposing to juvenile myoclonic epilepsy on chromosome 6p and 15q. Lastly, the genes underlying several spike-wave epilepsies in mice have been cloned, and three of these encode sub-units of voltage-gated calcium channels.
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PMID:Impact of our understanding of the genetic aetiology of epilepsy. 1089 63

Retigabine [N-(2-amino-4-[fluorobenzylamino]-phenyl) carbamic acid; D-23129] is a novel anticonvulsant, unrelated to currently available antiepileptic agents, with activity in a broad range of seizure models. In the present study, we sought to determine whether retigabine could enhance current through M-like currents in PC12 cells and KCNQ2/Q3 K(+) channels expressed in Chinese hamster ovary cells (CHO-KCNQ2/Q3). In differentiated PC12 cells, retigabine enhanced a linopirdine-sensitive current. The effect of retigabine was associated with a slowing of M-like tail current deactivation in these cells. Retigabine (0.1 to 10 microM) induced a potassium current and hyperpolarized CHO cells expressing KCNQ2/Q3 cells but not in wild-type cells. Retigabine-induced currents in CHO-KCNQ2/Q3 cells were inhibited by 60.6 +/- 11% (n = 4) by the KCNQ2/Q3 blocker, linopirdine (10 microM), and 82.7 +/- 5.4% (n = 4) by BaCl(2) (10 mM). The mechanism by which retigabine enhanced KCNQ2/Q3 currents involved large, drug-induced, leftward shifts in the voltage dependence of channel activation (-33.1 +/- 2.6 mV, n = 4, by 10 microM retigabine). Retigabine shifted the voltage dependence of channel activation with an EC(50) value of 1.6 +/- 0.3 microM (slope factor was 1.2 +/- 0.1, n = 4 to 5 cells per concentration). Retigabine (0.1 to 10 microM) also slowed the rate of channel deactivation, predominantly by increasing the contribution of a slowly deactivating tail current component. Our findings identify KCNQ2/Q3 channels as a molecular target for retigabine and suggest that activation of KCNQ2/Q3 channels may be responsible for at least some of the anticonvulsant activity of this agent.
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PMID:Retigabine, a novel anti-convulsant, enhances activation of KCNQ2/Q3 potassium channels. 1095 53


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