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)

Several lines of clinical evidence suggest that myoclonus is caused by a reduction of serotonin in the brain and hyperactivity of the inferior olive. We determined whether a change in serotonin content within the olivocerebellar system accompanied a predisposition to myoclonus and investigated the necessity of the inferior olive for a myoclonic seizure. The experiments employed the genetically epilepsy-prone rat that exhibits a profound myoclonic seizure in response to an auditory stimulus. We found that these animals demonstrated a significant reduction in the serotonergic innervation of the inferior olive without a significant change in the serotonergic innervation at any other level of the olivocerebellar circuit. The deficit in olivary serotonin was verified physiologically and pharmacologically by a reduced sensitivity of the genetically epilepsy-prone rat to the tremorogenic effect of harmaline, which is known to produce tremor through a mechanism that requires serotonergic innervation of the inferior olive. We quantified the timing of the myoclonic seizure of the genetically epilepsy-prone rat and found that its large amplitude 2-6 Hz clonus was always preceded by 9-10 Hz tremor that was synchronized among limbs. Ablation of the inferior olive by 3-acetylpyridine abolished the myoclonic seizure. The specificity of the deficit in olivary serotonin, the timing of the seizure, and the demonstration of the necessity of the inferior olive for myoclonus suggest that pathological inferior olivary activity contributes to the genesis of a myoclonic seizure.
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PMID:Removal of the inferior olive abolishes myoclonic seizures associated with a loss of olivary serotonin. 948 43

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1) is a rare, autosomal recessive disorder characterized by onset at age 6-16 years, generalized seizures, incapacitating myoclonus, and variable progression to cerebellar ataxia. The gene that causes EPM1, cystatin B, encodes a cysteine proteinase inhibitor. Only a minority of EPM1 patients carry a point mutation within the transcription unit. The majority of EPM1 alleles contain large expansions of a dodecamer repeat, CCC CGC CCC GCG, located upstream of the 5' transcription start site of the cystatin B gene; normal alleles contain two or three copies of this repeat. All EPM1 alleles with an expansion were resistant to standard PCR amplification. To precisely determine the size of the repeat in affected individuals, we developed a detection protocol involving PCR amplification and subsequent hybridization with an oligonucleotide containing the repeat. The largest detected expansion was approximately 75 copies; the smallest was approximately 30 copies. We identified affected siblings with repeat expansions, of different sizes, on the same haplotype, which confirms the repeat's instability during transmissions. Expansions were observed directly; contractions were deduced by comparison of allele sizes within a family. In a sample of 28 patients, we found no correlation between age at onset of EPM1 and the size of the expanded dodecamer. This suggests that once the dodecamer repeat expands beyond a critical threshold, cystatin B expression is reduced in certain cells, with pathological consequences.
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PMID:A PCR amplification method reveals instability of the dodecamer repeat in progressive myoclonus epilepsy (EPM1) and no correlation between the size of the repeat and age at onset. 952 56

Lafora's disease (LD; OMIM 254780) is an autosomal recessive form of progressive myoclonus epilepsy characterized by seizures and cumulative neurological deterioration. Onset occurs during late childhood and usually results in death within ten years of the first symptoms. With few exceptions, patients follow a homogeneous clinical course despite the existence of genetic heterogeneity. Biopsy of various tissues, including brain, revealed characteristic polyglucosan inclusions called Lafora bodies, which suggested LD might be a generalized storage disease. Using a positional cloning approach, we have identified at chromosome 6q24 a novel gene, EPM2A, that encodes a protein with consensus amino acid sequence indicative of a protein tyrosine phosphatase (PTP). mRNA transcripts representing alternatively spliced forms of EPM2A were found in every tissue examined, including brain. Six distinct DNA sequence variations in EPM2A in nine families, and one homozygous microdeletion in another family, have been found to cosegregate with LD. These mutations are predicted to cause deleterious effects in the putative protein product, named laforin, resulting in LD.
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PMID:Mutations in a gene encoding a novel protein tyrosine phosphatase cause progressive myoclonus epilepsy. 977 10

Progressive myoclonus epilepsy of the Unverricht-Lundborg type is the most common cause of progressive myoclonus epilepsy worldwide. Typical features include onset at the age of 6-15 years, stimulus-sensitive myoclonus, tonic-clonic seizures, a progressive course and characteristic electroencephalographic findings with an exceptionally high sensitivity to photic stimulation. With modern anticonvulsive therapy the symptoms are relatively well controlled, and the disease may not always progress. Previously, no biochemical or pathological marker existed for the diagnosis of Unverricht-Lundborg disease. The positional cloning strategy was applied to identify the genetic defects that are responsible for this disease. The underlying gene encodes cystatin B, a cysteine protease inhibitor. The major mutation worldwide is an unstable expansion of a dodecamer minisatellite repeat unit in the promoter region of the cystatin B gene. In addition, five 'minor' mutations have been described. In the majority of patients, a reduced level of the cystatin B gene product seems to be the primary mechanism in the pathology, but the pathogenetic mechanisms are yet unknown. The molecular genetic findings have made a specific diagnosis possible and are the basis for understanding the molecular pathogenesis of the disease. This understanding may lead to the development of specific therapies for Unverricht-Lundborg disease.
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PMID:Clinical features and genetics of progressive myoclonus epilepsy of the Univerricht-Lundborg type. 981 34

We report on a 31-year-old female with vitamin B6-dependent seizures whose seizure onset was in the neonatal period. Her elder brother had the same disorder and died in infancy. Administration of vitamin B6 was initiated in the postnatal period. At the age of 12 years 1 month, 2 months after withdrawal of vitamin B6, visual seizures began to occur frequently. Myoclonic seizures and occasional generalized convulsive seizures were also observed. At the same time, photoparoxysmal response and spontaneous diffuse spike-wave bursts were seen on her EEG. Myoclonic seizures were provoked by intermittent photic stimulation during the EEG. It is distinctive that visual seizures were one of the main seizure types in this patient, that her clinical course was relatively benign, and that she has normal intellectual outcome.
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PMID:Long-term follow-up of an individual with vitamin B6-dependent seizures. 1021 Feb 53

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1; MIM 254800) is an autosomal recessive disorder characterized by seizures, myoclonus and progression to cerebellar ataxia. EPM1 arises due to mutations in the cystatin B (CSTB) gene which encodes a cysteine proteinase inhibitor. Only a minority of EPM1 alleles carry point mutations, while the majority contain large expansions of the dodecamer CCCCGCCCCGCG repeat which is present at two to three copies in normal individuals. The dodecamer repeat is located in the 5' flanking region of the CSTB gene, presumably in its promoter. The pathological repeat expansion results in a reduction in CSTB mRNA, which may be cell specific. To elucidate the mechanism of this reduction of gene expression, we have studied the putative CSTB promoter in vitro. A 3.8 kb fragment, containing the putative promoter with a 600 bp repeat expansion, showed a 2- to 4-fold reduction in luciferase activity compared with an identical fragment with a normal repeat; this reduction was observed only in certain cell types. Introduction of heterologous DNA fragments of 730 and 1000 bp into the normal promoter, instead of the repeat expansion, showed similarly reduced activity. Terminal deletions of the promoter implicate a putative AP-1 binding site, upstream of the repeat, in CSTB transcription activation. We propose that a novel mechanism of pathogenesis, the altering of the spacing of transcription factor binding sites from each other and/or the transcription initiation site due to repeat expansion, is among the causes of reduction in CSTB expression and thus EPM1.
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PMID:Altered spacing of promoter elements due to the dodecamer repeat expansion contributes to reduced expression of the cystatin B gene in EPM1. 1044 45

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is characterized by onset at age 6-15 years, stimulus-sensitive myoclonus, tonic-clonic seizures, and typical EEG findings, with marked sensitivity to photic stimulation. Previously the course of the disease was progressive throughout the life, and no biochemical or pathologic marker existed for the diagnosis of EPM1. With modern anticonvulsive therapy, the prognosis has improved significantly, the symptoms are nowadays relatively well controlled, and the disease may not always progress. Moreover, the molecular genetic findings have now made possible an etiologic diagnosis of EPM1. The positional cloning strategy was applied to identify the gene whose defects are responsible for EPM1. The underlying gene encodes cystatin B, a cysteine protease inhibitor. The major mutation worldwide is an unstable expansion of a dodecamer minisatellite repeat unit in the promoter region of the cystatin B gene. In addition, five "minor" mutations have been described. Cystatin B mutations are now known to account for both Mediterranean myoclonus and for "Baltic" myoclonus, described mainly from Finland, thus solving a long-term controversy and proving that these two disorders are one single disease entity. The pathogenetic mechanisms in EPM1 are yet unknown, but in the majority of patients, a reduced level of the cystatin B gene product seems to be the primary mechanism in the pathology. Understanding the molecular pathogenesis of EPM1 may lead to the development of specific therapies for the disease.
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PMID:Progressive myoclonus epilepsy of Unverricht-Lundborg type. 1044 47

At a tertial referral epilepsy centre 39 children were consecutively enrolled in an open add-on study with topiramate (TPM). All children had intractable epilepsy; the mean seizure frequency was 36 per month, and 31 children were treated with polypharmacy. All but five children were mentally retarded. The initial dose of TPM was 0.5-1 mg/kg daily, slowly titrated with 1-3 mg/kg daily every second week with an estimated target dose of 10 mg/kg daily. At latest follow-up 19 children continued on TPM, three (8%) were seizure-free, eight (21%) had a seizure reduction of more than 50% and eight (21%) improved their general condition. Mean follow-up was 13 months (range 9-36 months). Seizure reduction was seen in focal as well as generalized epilepsies. Adverse effects were reported in 21 cases (54%), weight loss and sedation being most frequent. The mean steady state dose in the children continuing on TPM was at latest follow-up: 14 mg/kg daily (< 5 years), 10 mg/kg daily (5-7 years), 5.8 mg/kg daily (8-17 years). The corresponding plasma level varied from 3 to 45 mumol/litre, and a significant correlation between the daily dose in mg/kg and the plasma level was found. Two patients with progressive myoclonus epilepsy are described separately; one had a dramatic general improvement. It is concluded that TPM seems to be a promising new broad-spectrum anti-epileptic drug, which is efficacious even in epilepsy syndromes, intractable to other new anti-epileptic drugs such as vigabatrin and lamotrigine.
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PMID:Clinical experiences with topiramate in children with intractable epilepsy. 1046 65

A 7-year-old female with benign childhood epilepsy with centrotemporal spikes developed epileptic negative myoclonus (ENM) seizures during carbamazepine (CBZ) treatment. She had experienced nocturnal partial seizures since 5 years of age. Interictal electroencephalography demonstrated typical rolandic discharges. Valproate was first initiated at 6 years of age, but the seizures were uncontrollable. Carbamazepine was added and valproate withdrawn. The frequency of partial seizures did not decrease. Moreover, she had brief episodes of tone loss in each or both arms and eye blinking several weeks after CBZ introduction. Unilateral loss of arm tone corresponded to spike-and-wave discharges in the contralateral centrotemporal region, and a loss of tone in arms was associated with bilateral synchronous discharges. Eye blinking was also related to bilateral synchronous discharges and classified as a myoclonic seizure. The ENM and myoclonic seizures disappeared soon after CBZ withdrawal. Therefore the authors concluded that CBZ induced the ENM and myoclonic seizures in this patient. CBZ sometimes induces generalized seizures in the treatment of partial epilepsy and generalized epilepsy. CBZ-induced ENM seizures should be considered when a brief lapse of tone appears during CBZ treatment.
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PMID:Epileptic negative myoclonus induced by carbamazepine in a child with BECTS. Benign childhood epilepsy with centrotemporal spikes. 1051 96

Among the epilepsies, the progressive myoclonus epilepsies (PMEs) form a heterogeneous group of rare diseases characterized by myoclonus, epilepsy, and progressive neurologic deterioration, particularly dementia and ataxia. The success of the Human Genome Project and the fact that most PMEs are inherited through a mendelian or mitochondrial mode have resulted in important advances in the definition of the molecular basis of PME. The gene defects for the most common forms of PME (Unverricht-Lundborg disease, the neuronal ceroid lipofuscinoses, Lafora disease, type I sialidosis, and myoclonus epilepsy with ragged-red fibers) have been either identified or mapped to specific chromosome sites. Unverricht-Lundborg disease has been shown to be caused by mutations in the gene that codes for cystatin B, an inhibitor of cysteine protease. The most common mutation in Unverricht-Lundborg disease is an expansion of a dodecamer repeat located in a noncoding region upstream of the transcription start site of the cystatin B gene, making it the first human disease associated with instability of a dodecamer repeat. Juvenile neuronal ceroid lipofuscinosis is caused by mutations in the CLN3 gene, a gene of unknown function that encodes a 438-amino-acid protein of possible mitochondrial location. Other forms of neuronal ceroid lipofuscinosis that occur as PME and Lafora disease have been mapped by means of linkage analysis, but the corresponding gene defects remain unknown. Sialidosis has been shown to be caused by mutations in the sialidase gene, and myoclonus epilepsy with ragged-red fibers is well known to be caused by mutations in the mitochondrial gene that codes for tRNA(Lys). How the different PME gene defects described produce the various PME phenotypes, including epileptic seizures, remains unknown. The development of animal models that bear these mutations is needed to increase our knowledge of the basic mechanisms involved in the PMEs. This knowledge should lead to the development of new and effective forms of therapy, which are especially lacking for the PMEs.
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PMID:The molecular genetic bases of the progressive myoclonus epilepsies. 1051 28


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