Centrotemporal spikes in families with rolandic epilepsy: linkage to chromosome 15q14

OBJECTIVE: To localize a gene predisposing to benign epilepsy of childhood with centrotemporal spikes (BECTS). BACKGROUND: BECTS, or rolandic epilepsy, is the most prevalent idiopathic epilepsy syndrome in childhood. Functional relevant defects in the alpha 4 subunit of the neuronal nicotinic acetylcholine receptor (AChR) have been demonstrated in autosomal dominant nocturnal frontal lobe epilepsy, which, like BECTS, is an idiopathic partial epilepsy. METHODS: A DNA linkage study was conducted screening all chromosomal regions known to harbor neuronal nicotinic AChR subunit genes. Twenty-two nuclear families with BECTS were analyzed. RESULTS: In an "affected-only" study, best p values and lod scores were reached between D15S165 and D15S1010 on chromosome 15q14. In multipoint nonparametric linkage analysis a nominal p value of 0.000494 was calculated by GENEHUNTER. Best parametric results were obtained under an autosomal recessive model with heterogeneity (multipoint lod score 3.56 with 70% of families linked to the locus). These markers are localized in direct vicinity to the alpha 7 subunit gene of the AChR. CONCLUSIONS: We found evidence for linkage of BECTS to a region on chromosome 15q14. Either the alpha 7 AChR subunit gene or a closely linked gene are implicated in pedigrees with BECTS. The disorder is genetically heterogeneous. Surprisingly, the same chromosomal area has been reported to be linked to the phenotype in families with an auditory neurophysiologic deficit as well as in families with juvenile myoclonic epilepsy, another idiopathic but generalized epilepsy syndrome.     

Refined mapping of the epilepsy susceptibility locus EJM1 on chromosome 6

Juvenile myoclonic epilepsy (JME) is a genetically determined common subtype of idiopathic generalized epilepsy. Linkage to the HLA complex on chromosome 6p21.3 and an allelic association with HLA-DR13 and -DQB1 alleles suggest that a susceptibility locus for JME, designated as "EJM1," is located within or near the HLA region. However, further studies revealed controversial results, and genetic heterogeneity has been suspected. The present study was designed to evaluate the validity of the association and linkage findings and to refine the map position of EJM1. Our association analysis showed no significant difference of the frequency of HLA-DR13 carriers in 62 German JME patients compared with that in 77 German controls (X2 = 0.98, df = 1, p = 0.161, one-tailed). Multipoint linkage analysis with use of microsatellite markers from the chromosomal region 6p25-q13 in 29 German families of JME patients provided significant evidence that an epilepsy locus (EJM1) close to the HLA locus confers susceptibility to "idiopathic" generalized seizures (Zmax = 3.27 at theta max = 0.033 centromeric to the HLA-DQ locus), assuming an autosomal dominant mode of inheritance with 70% penetrance. Haplotype analyses revealed key recombinations in five families, which locate EJM1 to the centromeric side of the HLA-DQ locus. This study confirms a causative role of EJM1 in the pathogenesis of idiopathic generalized seizures in the majority of German families of JME patients and refines a candidate region of 10.1 cM in the chromosomal region 6p21 between the flanking loci HLA-DQ and D6S1019. A possible explanation for the current controversial results in families of different populations might be ethnic variation of interfering polygenic effects that could be permissive for heterogeneous susceptibility alleles.     

Landscape ecology and epidemiology of vector-borne diseases: tools for spatial analysis

We studied twins to examine the genetics of epilepsy syndromes. We ascertained 358 twin pairs in whom one or both reported seizures. After evaluation, 253 of 358 (71%) had seizure disorders and 105 pairs were false positives. Among the monozygous (MZ) pairs, more were concordant for seizures (48 of 108; casewise concordance = 0.62 +/- 0.05) than among the dizygous (DZ) pairs (14 of 145; casewise concordance = 0.18 +/- 0.04). In 94% of concordant MZ pairs, and 71% of concordant DZ pairs, both twins had the same major epilepsy syndrome. When analyzed according to major epilepsy syndrome, the casewise concordances for generalized epilepsies (MZ = 0.82; DZ = 0.26), both idiopathic (MZ = 0.76; DZ = 0.33) and symptomatic (MZ = 0.83; DZ = 0), were greater than those for partial epilepsies (MZ = 0.36; DZ = 0.05), with intermediate values seen for febrile seizures (MZ = 0.58; DZ = 0.14) and unclassified epilepsies (MZ = 0.53; DZ = 0.18). We conclude that genetic factors are particularly important in the generalized epilepsies but also play a role in the partial epilepsies. The high frequency of concordant MZ pairs with the same major syndrome strongly suggests there are syndrome-specific genetic determinants rather than a broad genetic predisposition to seizures.     

Effect of thyroid hormone deficiency on RC3/neurogranin mRNA expression in the prenatal and adult caprine brain

We describe a new syndrome of familial temporal lobe epilepsy in 38 individuals from 13 unrelated white families. The disorder was first identified in 5 concordant monozygotic twin pairs as part of a large-scale twin study of epilepsy. When idiopathic partial epilepsy syndromes were excluded, the 5 pairs accounted for 23% of monozygotic pairs with partial epilepsies, and 38% of monozygotic pairs with partial epilepsy and no known etiology. Seizure onset for twin and nontwin subjects usually occurred during adolescence or early adult life. Seizure types were simple partial seizures with psychic or autonomic symptoms, infrequent complex partial seizures, and rare secondarily generalized seizures. Electroencephalograms revealed sparse focal temporal interictal epileptiform discharges in 22% of subjects. Magnetic resonance images appeared normal. Nine affected family members (24%) had not been diagnosed prior to the study. Pedigree analysis suggested autosomal dominant inheritance with age-dependent penetrance. The estimated segregation ratio was 0.3, indicating an overall penetrance of 60% assuming autosomal dominant inheritance. The mild and often subtle nature of the symptoms in some family members may account for lack of prior recognition of this common familial partial epilepsy. This disorder has similarities to the El mouse, a genetic model of temporal lobe epilepsy with a major gene on mouse chromosome 9, which is homologous with a region on human chromosome 3.     

Ectopic cerebral tissue in the middle ear. A case report

Most idiopathic generalized epilepsies have an onset in childhood or adolescence, with a moderate second incidence peak in the presenium predominantly in women. This study addressed the question of a later onset. The available literature and the records of four personal data sets (two prospective incidence surveys of epileptic seizures, one prevalence study of epilepsy, and one clinical series of individuals with epilepsy) were screened for patients who had experienced a first generalized convulsive seizure with bilateral spike-wave complexes on EEG after 60 years of age. Reports of first idiopathic generalized tonic-clonic seizures occurring after age 60 were extremely rare and none was found in our four cohorts regardless of the methodology involved. Only five case reports were found, all involving a woman. Two had a family history of seizure disorders and two had had at least one seizure earlier in life. Idiopathic generalized epilepsy of late onset, if this condition actually exists, is likely to be the consequence of a genetic predisposition triggered by acquired epileptogenic factors.     

Comparison of specificity between IgG, IgE and T cells to three casein components: implication for the role of circulating allergen-specific T cells in food allergy

Juvenile absence epilepsy (JAE) is a common subtype of idiopathic generalized epilepsy (IGE). Hereditary factors play a major role in its etiology. The important function of glutamate receptors (GluRs) in excitatory neurotransmission, synaptic plasticity, and neurodevelopment suggests their involvement in epileptogenesis. A tetranucleotide repeat polymorphism in the non-coding region of the kainate-selective GluR5 receptor gene (GRIK1) on chromosome 21q22.1 provides the tool to investigate this candidate gene. The present association and linkage study tested the hypothesis that allelic variants of GRIK1 confer genetic susceptibility to the pathogenesis of JAE. Our family-based association analysis using the haplotype-based haplotype relative risk statistic revealed an association of JAE with the nine-repeat containing allele of the GRIK1 tetranucleotide polymorphism (chi2 = 8.31, df = 1, P = 0.004). Supportive evidence for linkage to a JAE related IGE spectrum (Zmax = 1.67 at GRIK1) under an autosomal dominant mode of inheritance and significant allele sharing (P < 0.05) among the affected family members suggest that allelic variants of GRIK1 contribute a major genetic determinant to the pathogenesis of JAE-related phenotypes.     

Identification of four classes of brain nicotinic receptors using beta2 mutant mice

Although the expression patterns of the neuronal nicotinic acetylcholine receptor (nAChR) subunits thus far described are known, the subunit composition of functional receptors in different brain areas is an ongoing question. Mice lacking the beta2 subunit of the nAChR were used for receptor autoradiography studies and patch-clamp recording in thin brain slices. Four distinct types of nAChRs were identified, expanding on an existing classification [Alkondon M, Albuquerque EX (1993) Diversity of nicotinic acetylcholine receptors in rat hippocampal neurons. I. Pharmacological and functional evidence for distinct structural subtypes. J Pharmacol Exp Ther 265:1455-1473.], and tentatively identifying the subunit composition of nAChRs in different brain regions. Type 1 nAChRs bind alpha-bungarotoxin, are not altered in beta2 -/- mice, and contain the alpha7 subunit. Type 2 nAChRs contain the beta2 subunit because they are absent in beta2 -/- mice, bind all nicotinic agonists used with high affinity (excluding alpha-bungarotoxin), have an order of potency for nicotine > cytisine in electrophysiological experiments, and are likely to be composed of alpha4 beta2 in most brain regions, with other alpha subunits contributing in specific areas. Type 3 nAChRs bind epibatidine with high affinity in equilibrium binding experiments and show that cytisine is as effective as nicotine in electrophysiological experiments; their distribution and persistence in beta2 -/- mice strongly suggest a subunit composition of alpha3 beta4. Type 4 nAChRs bind cytisine and epibatidine with high affinity in equilibrium binding experiments and persist in beta2 -/- mice; cytisine = nicotine in electrophysiological experiments. Type 4 nAChRs also exhibit faster desensitization than type 3 nAChRs at high doses of nicotine. Knock-out animals lacking individual alpha subunits should allow a further dissection of nAChR subclasses.     

X-linked malformations of neuronal migration

Malformations of neuronal migration such as lissencephaly (agyria-pachygyria spectrum) are well-known causes of mental retardation and epilepsy that are often genetic. For example, isolated lissencephaly sequence and Miller-Dieker syndrome are caused by deletions involving a lissencephaly gene in chromosome 17p13.3, while many other malformation syndromes have autosomal recessive inheritance. In this paper, we review evidence supporting the existence of two distinct X-linked malformations of neuronal migration. X-linked lissencephaly and subcortical band heterotopia (XLIS) presents with sporadic or familial mental retardation and epilepsy. The brain malformation varies from classical lissencephaly, which is observed in males, to subcortical band heterotopia, which is observed primarily in females. The XLIS gene is located in chromosome Xq22.3 based on the breakpoint of an X-autosomal translocation. Bilateral periventricular nodular heterotopia (BPNH) usually presents with sporadic or familial epilepsy with normal intelligence, primarily in females, although we have evaluated two boys with BPNH and severe mental retardation. The gene for BPNH has been mapped to chromosome Xq28 based on linkage studies in multiplex families and observation of a subtle structural abnormality in one of the boys with BPNH and severe mental retardation.     

Role of the nucleus raphe magnus in antinociception produced by ABT-594: immediate early gene responses possibly linked to neuronal nicotinic acetylcholine receptors on serotonergic neurons

Recently, a novel cholinergic channel modulator, (R)-5-(2-azetidinylmethoxy)-2-chloropyridine (ABT-594), was shown to produce potent analgesia in a variety of rodent pain models when administered either systemically or centrally into the nucleus raphe magnus (NRM). The purpose of the present study was to investigate the possible supraspinal contribution of ABT-594 by assessing its ability to induce expression of the immediate early gene c-fos, a biochemical marker of neuronal activation, in the NRM of rats. Putative serotonergic neurons in the NRM, a medullary nucleus proposed to be involved in descending antinociceptive pathways, were identified immunohistochemically using a monoclonal antibody (mAb) against tryptophan hydroxylase. ABT-594 (0.03-0.3 micromol/kg, i.p.) produced a dose-dependent induction of Fos protein that was blocked by the central nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine (5 micromol/kg, i.p.) but not by the peripheral nAChR antagonist hexamethonium (15 micromol/kg, i.p.). Immunohistological studies using mAb 299 revealed the expression of alpha4-containing nAChRs in the NRM. The alpha4 immunostaining was dramatically reduced by pretreating (30 d) animals with the serotonin neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), which was previously shown to substantially attenuate the antinociceptive actions of ABT-594. In a double immunohistochemical labeling experiment, coexpression of the serotonin marker tryptophan hxdroxylase and the alpha4 nAChR subunit in NRM neurons was observed. These results suggest that the analgesic mechanism of ABT-594 may in part involve the activation of the NRM, a site where alpha4-containing nAChRs are expressed by serotonergic neurons.     

Prevalence, classification, and severity of epilepsy and epileptic syndromes in children

PURPOSE: To determine the point prevalence of active childhood epilepsy in a defined area and evaluate the usefulness of ILAE classification of seizures, and epilepsies/syndromes with special interest in severe epilepsies. METHODS: By using the latest ILAE International Classification of Epileptic Seizures (ICES, 1981) and Epilepsies and Epileptic Syndromes (ICE, 1989), we determined the age- and sex-specific prevalence rates of epilepsy, type of seizures, epilepsies, and recognizable epileptic syndromes, as well as the proportion of severe cases in each seizure/epilepsy/syndrome category in all children 0-15 years of age from a geographically defined area in Finland. All medical records, neurophysiological recordings and available clinical data were reviewed retrospectively. RESULTS: Point prevalence of active epilepsy on December 12, 1992 was 3.94 per 1,000. According to ICES/ICE, we were able to classify 96% of seizures and 90% of epilepsies and syndromes. Generalized seizure and epilepsy/syndrome types were more prevalent in children 0-6 years of age and partial/localization-related in children 6-15 years of age. Epilepsy was intractable in 17% of all cases and correlated significantly with symptomatic etiology and early onset of epilepsy, as well as with additional neuroimpairments. CONCLUSIONS: A considerable number of cases fell into the nonspecific categories of ICE, which limits the value of present epilepsy/syndrome classification in terms of prognosis, prediction, and indication for special investigations in individual cases. A number of intractable cases was relatively low, indicating good prognosis in many childhood epilepsies, especially when additional neuroimpairments are absent.     

D alpha3, a new functional alpha subunit of nicotinic acetylcholine receptors from Drosophila

Nicotinic acetylcholine (ACh) receptors (nAChRs) are important excitatory neurotransmitter receptors in the insect CNS. We have isolated and characterized the gene and the cDNA of a new nAChR subunit from Drosophila. The predicted mature nAChR protein consists of 773 amino acid residues and has the structural features of an ACh-binding alpha subunit. It was therefore named D alpha3, for Drosophila alpha-subunit 3. The d alpha3 gene maps to the X chromosome at position 7E. The properties of the D alpha3 protein were assessed by expression in Xenopus oocytes. D alpha3 did not form functional receptors on its own or in combination with any Drosophila beta-type nAChR subunit. Nondesensitizing ACh-evoked inward currents were observed when D alpha3 was coexpressed with the chick beta2 subunit. Half-maximal responses were at approximately 0.15 microM ACh with a Hill coefficient of approximately 1.5. The snake venom component alpha-bungarotoxin (100 nM) efficiently but reversibly blocked D alpha3/beta2 receptors, suggesting that D alpha3 may be a component of one of the previously described two classes of toxin binding sites in the Drosophila CNS.     

Alpha 5 subunit forms functional alpha 3 beta 4 alpha 5 nAChRs in transfected human cells

nAChRs heterologously expressed in human cells after transient transfection with alpha 3 beta 4 alpha 5 or alpha 3 beta 4 subunit cDNAs exhibited similar sensitivities to antagonists and comparable functional channel profiles. However, the sum of two Hill equations was required for best fitting the ACh dose-current response curves after co-expression of alpha 5, alpha 3 and beta 4 subunits. One component was comparable to that obtained in alpha 3 beta 4-transfected cells, while the additional component, putatively attributed to an alpha 3 beta 4 alpha 5 nAChR population, showed a Hill coefficient > 2 and a nine-fold greater half-maximal ACh concentration (EC50). These results suggest that the alpha 5 subunit participates in the assembly of alpha 3 beta 4 alpha 5 nAChRs complexes in human cells, adding a new member to the family of neuronal nicotinic receptors.     

A new alpha-conotoxin which targets alpha3beta2 nicotinic acetylcholine receptors

We have isolated a 16-amino acid peptide from the venom of the marine snail Conus magus which potently blocks nicotinic acetylcholine receptors (nAChRs) composed of alpha3beta2 subunits. This peptide, named alpha-conotoxin MII, was identified by electrophysiologically screening venom fractions against cloned nicotinic receptors expressed in Xenopus oocytes. The peptide's structure, which has been confirmed by mass spectrometry and total chemical synthesis, differs significantly from those of all previously isolated alpha-conotoxins. Disulfide bridging, however, is conserved. The toxin blocks the response to acetylcholine in oocytes expressing alpha3beta2 nAChRs with an IC50 of 0.5 nM and is 2-4 orders of magnitude less potent on other nAChR subunit combinations. We have recently reported the isolation and characterization of alpha-conotoxin ImI, which selectively targets homomeric alpha7 neuronal nAChRs. Yet other alpha-conotoxins selectively block the muscle subtype of nAChR. Thus, it is increasingly apparent that alpha-conotoxins represent a significant resource for ligands with which to probe structure-function relationships of various nAChR subtypes.     

Expansion of bronchial epithelial cell populations by in vitro culture of explants from dysplastic and histologically normal sites

Most Colombian populations stem from the admixture of Caucasians, Amerindians and Negroids. In the world, these two latter ethnical groups show a significantly higher prevalence of epilepsy than the former one. We tested the hypothesis that the high prevalence of idiopathic epilepsy with generalized tonic clonic seizures found in the Antioquian population (Paisas), from Colombia, is due to their possible joint Negroid and Amerindian ethnic components. We have previously demonstrated that inheritance is the principal factor for developing epilepsy in this community. Analyses of racial admixture, heterogeneity between populations, genetic distance, and phyletic relationships were performed among epileptic and non epileptic samples from the Antioquian community. Also Caucasians, Spaniards, Basques, Jews, Chileans, Negroids, Amerindians and Mongoloids were included in the analysis. Four highly polymorphic blood systems were used as genetic markers: RH, MNS, ABO and FY. They were chosen because of their high discriminant power in these ethnic groups. In the population affected with idiopathic epilepsy, the estimated Negroid and Amerindian rates of admixture were low (3% and 14%, respectively). Although, these degrees of admixture can be explained due to common ancestral origins, the estimated proportion of Amerindian admixture in the epileptic affected population, was significantly higher than the estimated for the Non affected Antioquian population. The latter finding is consistent with the analysis of heterogeneity between populations that discriminated epileptic population from non epileptic Antioquian population (p < 0.05). Epileptic and non epileptic Paisas clustered in topology with Caucasians, very close to Spaniards and Basques and highly distant from Negroids and Amerindians. Thus, far, the origin of the high prevalence of idiopathic epilepsy in the Antioquian (Paisa) population cannot be explained by the hypothetical joint Negroid and Amerindian ethnical admixture, but using additional genetic markers and other methods of racial estimation of admixture it is necessary to corroborate if the Amerindian admixture component is significantly higher in the epileptic population than in the non epileptic Paisa population.     

Childhood absence epilepsy with tonic-clonic seizures and electroencephalogram 3-4-Hz spike and multispike-slow wave complexes: linkage to chromosome 8q24

Childhood absence epilepsy (CAE), a common form of idiopathic generalized epilepsy, accounts for 5%-15% of childhood epilepsies. To map the chromosomal locus of persisting CAE, we studied the clinical and electroencephalographic traits of 78 members of a five-generation family from Bombay, India. The model-free affected-pedigree member method was used during initial screening with chromosome 6p, 8q, and 1p microsatellites, and only individuals with absence seizures and/or electroencephalogram 3-4-Hz spike- and multispike-slow wave complexes were considered to be affected. Significant P values of .00000-.02 for several markers on 8q were obtained. Two-point linkage analysis, assuming autosomal dominant inheritance with 50% penetrance, yielded a maximum LOD score (Zmax) of 3.6 for D8S502. No other locus in the genome achieved a significant Zmax. For five smaller multiplex families, summed Zmax was 2.4 for D8S537 and 1.7 for D8S1761. Haplotypes composed of the same 8q24 microsatellites segregated with affected members of the large family from India and with all five smaller families. Recombinations positioned the CAE gene in a 3.2-cM interval.     

Computer analysis of polysomnographic data

OBJECTIVE: To map the gene causing an unusual EEG pattern of delta bursts that appears to segregate as an autosomal dominant trait in an Italian family. The EEG pattern was observed in four family members affected by idiopathic generalized epilepsy (IGE) and in six other clinically unaffected members. METHODS: All available family members underwent clinical and EEG examination. DNA samples were obtained and used to perform a whole-genome scan with 270 microsatellite markers. After the first linked marker was identified, 12 additional markers in the same chromosomal region were tested to confirm linkage and define a candidate interval. RESULTS: The gene responsible for the EEG trait was mapped to an 11-cM interval on the proximal short arm of chromosome 3 (3p14.2-p12.1). CONCLUSION: In this family, a characteristic EEG activity is due to the effect of a single gene on chromosome 3p. A gene encoding a Ca2+ channel subunit maps in the interval and is a potential candidate for the trait. The clinical expression of epilepsy in four family members may reflect the interaction of additional genes, though environmental or other factors cannot be excluded.