Genes and loci involved in febrile seizures and related epilepsy syndromes

Unlocking the link between haptoglobin polymorphism and noninfectious human diseases: insights and implications

Haptoglobin (Hp) is a polymorphic protein that was initially described as a hemoglobin (Hb)-binding protein. The major functions of Hp are to scavenge Hb, prevent iron loss, and prevent heme-based oxidation. Hp regulates angiogenesis, nitric oxide homeostasis, immune responses, and prostaglandin synthesis. Genetic polymorphisms in the Hp gene give rise to different phenotypes, including Hp 1-1, Hp 2-1, and Hp 2-2. Extensive research has been conducted to investigate the association between Hp polymorphisms and several medical conditions including cardiovascular disease, inflammatory bowel disease, cancer, transplantation, and hemoglobinopathies. Generally, the Hp 2-2 phenotype is associated with increased disease risk and poor outcomes. Over the years, the Hp 2 allele has spread under genetic pressures. Individuals with the Hp 2-2 phenotype generally exhibit lower levels of CD163 expression in macrophages. The decreased expression of CD163 may be associated with the poor antioxidant capacity in the serum of subjects carrying the Hp 2-2 phenotype. However, the Hp 1-1 phenotype may confer protection in some cases. The Hp1 allele has strong antioxidant, anti-inflammatory, and immunomodulatory properties. It is important to note that the benefits of the Hp1 allele may vary depending on genetic and environmental factors as well as the specific disease or condition under consideration. Therefore, the Hp1 allele may not necessarily confer advantages in all situations, and its effects may be context-dependent. This review highlights the current understanding of the role of Hp polymorphisms in cardiovascular disease, inflammatory bowel disease, cancer, transplantation, hemoglobinopathies, and polyuria.

Seizures in Children with Influenza during the 2022-2023 Winter Season, a Case Series

Influenza is a viral infection presenting with general symptoms such as fever, headache, fatigue, and involvement of airways or the gastrointestinal tract. The nervous system may be involved, but less frequently. These neurological complications remain challenging to diagnose; moreover, no guidelines for management and treatment exist. Therefore, when presenting with neurological symptoms, patients undergo invasive diagnostic procedures and empirical treatments before making the correct diagnosis. During the winter of 2022-2023, four children between nine months and nine years of age were admitted to the Lausanne University Hospital, Switzerland, complaining of influenza and neurological complications. This report presents the symptoms of neurological manifestation and the treatment management of the four patients. All the legally authorized representatives gave their written informed consent before study inclusion.

Etiological and risk factors in recurrent febrile seizures: Insights through EEG analysis

BACKGROUND

Febrile seizures, convulsive episodes in young children during febrile illnesses, are a significant concern due to their potential for recurrence and associated uncertainties. This study investigated the causes and risks associated with recurrent febrile seizures and the critical role of electroencephalogram (EEG) in their accurate diagnosis.

METHODS

Following Institutional Review Board approval and going through the consenting process with parents, this study gathered the clinical features and EEG recordings of children admitted with febrile seizures in the Department of Pediatrics, Mahatma Gandhi Memorial Hospital, Kakatiya Medical College, Warangal, Telangana, India. Descriptive statistics, including mean, standard deviation (SD), frequencies, and percentages, were computed to understand the data comprehensively. The Chi-Square test was employed to analyze the association between variables, with a significance level of 0.05, ensuring reliable and trustworthy findings.

RESULTS

Out of 42 children studied, 28 (66.67%) presented with simple febrile seizures, with the mean time of occurrence of seizures from the onset of fever being 7.85 hours. Abnormal EEG was seen in 50% of children with complex febrile seizures and 16% with simple febrile seizures. Generalized epileptiform discharges were the most common epileptic activity observed. Low sodium levels had a significant relationship with febrile seizures in the analysis.

CONCLUSIONS

This study emphasizes the importance of EEG in diagnosing febrile seizures, particularly in complex cases. Our findings suggest that low sodium levels may be a significant risk factor for febrile seizures. Further research is necessary to identify other preventable risk factors to reduce the burden of the medical condition.

Molecular analysis and prenatal diagnosis of seven Chinese families with genetic epilepsy

Introduction

Genetic epilepsy is a large group of clinically and genetically heterogeneous neurological disorders characterized by recurrent seizures, which have a clear association with genetic defects. In this study, we have recruited seven families from China with neurodevelopmental abnormalities in which epilepsy was a predominant manifestation, aiming to elucidate the underlying causes and make a precise diagnosis for the cases.

Methods

Whole-exome sequencing (WES) combined with Sanger sequencing was used to identify the causative variants associated with the diseases in addition to essential imaging and biomedical examination.

Results

A gross intragenic deletion detected in MFSD8 was investigated via gap-polymerase chain reaction (PCR), real-time quantitative PCR (qPCR), and mRNA sequence analysis. We identified 11 variants in seven genes (ALDH7A1, CDKL5, PCDH19, QARS1, POLG, GRIN2A, and MFSD8) responsible for genetic epilepsy in the seven families, respectively. A total of six variants (c.1408T>G in ALDH7A1, c.1994_1997del in CDKL5, c.794G>A in QARS1, c.2453C>T in GRIN2A, and c.217dup and c.863+995_998+1480del in MFSD8) have not yet been reported to be associated with diseases and were all evaluated to be pathogenic or likely pathogenic according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

Methods

Based on the molecular findings, we have associated the intragenic deletion in MFSD8 with the mutagenesis mechanism of Alu-mediated genomic rearrangements for the first time and provided genetic counseling, medical suggestions, and prenatal diagnosis for the families. In conclusion, molecular diagnosis is crucial to obtain improved medical outcomes and recurrence risk evaluation for genetic epilepsy.

CELSR3 variants are associated with febrile seizures and epilepsy with antecedent febrile seizures

Aims

To identify novel pathogenic gene of febrile seizures (FS)/epilepsy with antecedent FS (EFS+).

Methods

The trio‐based whole‐exome sequencing was performed in a cohort of 462 cases with FS/EFS+. Silico programs, sequence alignment, and protein modeling were used to predict the damaging of variants. Statistical testing was performed to analyze gene‐based burden of variants.

Results

Five heterozygous missense variants in CELSR3 were detected in five cases (families) with eight individuals (five females, three males) affected. Two variants were de novo, and three were identified in families with more than one individual affected. All the variants were predicted to be damaging in silico tools. Protein modeling showed that the variants resulted in disappearance of multiple hydrogen bonds and one disulfide bond, which potentially caused functional impairments of protein. The frequency of CELSR3 variants identified in this study was significantly higher than that in controls. All affected individuals were diagnosed with FS/EFS+, including six patients with FS and two patients with EFS+. All cases presented favorable outcomes without neurodevelopmental disorders.

Conclusions

CELSR3 variants are potentially associated with FS/EFS+.

SCN1A Variants in vaccine-related febrile seizures: A prospective study

OBJECTIVE

Febrile seizures may follow vaccination. Common variants in the sodium channel gene, SCN1A, are associated with febrile seizures, and rare pathogenic variants in SCN1A cause the severe developmental and epileptic encephalopathy Dravet syndrome. Following vaccination, febrile seizures may raise the specter of poor outcome and inappropriately implicate vaccination as the cause. We aimed to determine the prevalence of SCN1A variants in children having their first febrile seizure either proximal to vaccination or unrelated to vaccination compared to controls.

METHODS

We performed SCN1A sequencing, blind to clinical category, in a prospective cohort of children presenting with their first febrile seizure as vaccine proximate (n = 69) or as non-vaccine proximate (n = 75), and children with no history of seizures (n = 90) recruited in Australian pediatric hospitals.

RESULTS

We detected 2 pathogenic variants in vaccine-proximate cases (p.R568X and p.W932R), both of whom developed Dravet syndrome, and 1 in a non-vaccine-proximate case (p.V947L) who had febrile seizures plus from 9 months. All had generalized tonic-clonic seizures lasting >15 minutes. We also found enrichment of a reported risk allele, rs6432860-T, in children with febrile seizures compared to controls (odds ratio = 1.91, 95% confidence interval = 1.31-2.81).

INTERPRETATION

Pathogenic SCN1A variants may be identified in infants with vaccine-proximate febrile seizures. As early diagnosis of Dravet syndrome is essential for optimal management and outcome, SCN1A sequencing in infants with prolonged febrile seizures, proximate to vaccination, should become routine. ANN NEUROL 2020;87:281-288.

Sociodemographic risk factors for febrile seizures: A school-based study from Izmir, Turkey

PURPOSE

Despite the fact that socioeconomic and environmental factors of a population are changing over time, there are few studies focusing on the effects of sociodemographic factors on the prevalence of febrile seizures (FS). This study was designed to find out the prevalence of FS and to investigate the effect of socio-cultural and economic factors on this prevalence among the Turkish school children.

METHODS

A school-based, cross-sectional study was conducted in first and second-class children. Data were collected through a questionnaire from the parents who agreed to be involved in the study. The survey had questions about some socioeconomic and demographic features of the children and febrile seizure episodes.

RESULTS

3806 children and parent pairs accepted to participate in the survey. Febrile seizure prevalence was 4.8%. It was found that the prevalence of FS was significantly associated with the chronic illnesses of a child that requires continuous medication, developmental delay of a child, NICU history, gestational hypertension history of a mother, and lower educational level of a mother. Recurrence of FS was observed in 32.9% of children. Children whose first FS was seen below the 39 °C had 1.9 times more recurrence risk.

CONCLUSION

FS prevalence rate has declined from 9.7% to 4.3% in our study population within ten years. It was thought that advancing healthcare systems in our country might be decreased the prevalence. Our study enabled us to find out sociodemographic risk factors of FS, but further studies are needed in order to confirm the effect of sociodemographic factors on FS prevalence.

De novo GABRA1 mutations in Ohtahara and West syndromes

OBJECTIVE

GABRA1 mutations have been identified in patients with familial juvenile myoclonic epilepsy, sporadic childhood absence epilepsy, and idiopathic familial generalized epilepsy. In addition, de novo GABRA1 mutations were recently reported in a patient with infantile spasms and four patients with Dravet syndrome. Those reports suggest that GABRA1 mutations are associated with infantile epilepsy including early onset epileptic encephalopathies. In this study, we searched for GABRA1 mutations in patients with infantile epilepsy to investigate the phenotypic spectrum of GABRA1 mutations.

METHODS

In total, 526 and 145 patients with infantile epilepsy were analyzed by whole-exome sequencing and GABRA1-targeted resequencing, respectively.

RESULTS

We identified five de novo missense GABRA1 mutations in six unrelated patients. A p.R112Q mutation in the long extracellular N-terminus was identified in a patient with infantile epilepsy; p.P260L, p.M263T, and p.M263I in transmembrane spanning domain 1 (TM1) were identified in three unrelated patients with West syndrome and a patient with Ohtahara syndrome, respectively; and p.V287L in TM2 was identified in a patient with unclassified early onset epileptic encephalopathy. Four of these mutations have not been observed previously.

SIGNIFICANCE

Our study suggests that de novo GABRA1 mutations can cause early onset epileptic encephalopathies, including Ohtahara syndrome and West syndrome.

Novel GABRG2 mutations cause familial febrile seizures

Objective:

To identify the genetic cause in a large family with febrile seizures (FS) and temporal lobe epilepsy (TLE) and subsequently search for additional mutations in a cohort of 107 families with FS, with or without epilepsy.

Methods:

The cohort consisted of 1 large family with FS and TLE, 64 smaller French families recruited through a national French campaign, and 43 Italian families. Molecular analyses consisted of whole-exome sequencing and mutational screening.

Results:

Exome sequencing revealed a p.Glu402fs*3 mutation in the γ2 subunit of the GABA_A receptor gene (GABRG2) in the large family with FS and TLE. Three additional nonsense and frameshift GABRG2 mutations (p.Arg136*, p.Val462fs*33, and p.Pro59fs*12), 1 missense mutation (p.Met199Val), and 1 exonic deletion were subsequently identified in 5 families of the follow-up cohort.

Conclusions:

We report GABRG2 mutations in 5.6% (6/108) of families with FS, with or without associated epilepsy. This study provides evidence that GABRG2 mutations are linked to the FS phenotype, rather than epilepsy, and that loss-of-function of GABA_A receptor γ2 subunit is the probable underlying pathogenic mechanism.

GABAA receptor biogenesis is impaired by the γ2 subunit febrile seizure-associated mutation, GABRG2(R177G)

A missense mutation in the GABAA receptor γ2L subunit, R177G, was reported in a family with complex febrile seizures (FS). To gain insight into the mechanistic basis for these genetic seizures, we explored how the R177G mutation altered the properties of recombinant α1β2γ2L GABAA receptors expressed in HEK293T cells. Using a combination of electrophysiology, flow cytometry, and immunoblotting, we found that the R177G mutation decreased GABA-evoked whole-cell current amplitudes by decreasing cell surface expression of α1β2γ2L receptors. This loss of receptor surface expression resulted from endoplasmic reticulum (ER) retention of mutant γ2L(R177G) subunits, which unlike wild-type γ2L subunits, were degraded by ER-associated degradation (ERAD). Interestingly, when compared to the condition of homozygous γ2L(R177G) subunit expression, disproportionately low levels of γ2L(R177G) subunits reached the cell surface with heterozygous expression, indicating that wild-type γ2L subunits possessed a competitive advantage over mutant γ2L(R177G) subunits for receptor assembly and/or forward trafficking. Inhibiting protein synthesis with cycloheximide demonstrated that the R177G mutation primarily decreased the stability of an intracellular pool of unassembled γ2L subunits, suggesting that the mutant γ2L(R177G) subunits competed poorly with wild-type γ2L subunits due to impaired subunit folding and/or oligomerization. Molecular modeling confirmed that the R177G mutation could disrupt intrasubunit salt bridges, thereby destabilizing secondary and tertiary structure of γ2L(R177G) subunits. These findings support an emerging body of literature implicating defects in GABAA receptor biogenesis in the pathogenesis of genetic epilepsies (GEs) and FS.

Febrile seizures: recent developments and unanswered questions

BACKGROUND

Febrile seizures (FS) are typically observed in infants and children affecting 2-5 % of the pediatric population and are the commonest seizures in childhood.

OBJECTIVES

The present review summarizes epidemiology, etiology, clinical picture, and diagnostic procedures as well as the therapeutic options and the different courses this disorder may take.

METHOD

An extensive review of literature is performed, while views and aspects towards the pathogenesis of FS are stated. Risk factors for multiple recurrences of FS and for subsequent epilepsy are analyzed. Questions regarding the treatment and follow-up of children with FS are answered.

RESULTS

Whereas the frequency of epilepsy following simple FS is estimated to be 1.0-2.2 % of patients, and thus does not differ from the risk of normal population, complicated FS are associated with an increased risk of subsequent epilepsy in 4.1-6.0 %. Febrile status epilepticus with focal symptoms may result in approximately 5 % of cases in complex partial epilepsy. Furthermore, multiple recurrences increase the risk for generalized epilepsy (>4 %). The immediate management of FS, intermittent prophylaxis, and the effectiveness of the treatment in combination with antipyretics are presented in detail.

CONCLUSION

FS can cause a great anxiety and even panic to parents and to the whole family. Parents should be educated about the benign condition and the good prognosis. Although much information has been gained, much remains to be learned.

Pediatric epilepsy genetics

PURPOSE OF REVIEW

Genetic epilepsies in childhood are a complex group of disorders, with heterogeneous etiologies and clinicopathologic features. This review focuses on primary genetic epilepsies, which may have variable neuropsychiatric comorbidities, but usually have no underlying gross neuropathology or evident metabolic disturbance. Epilepsy due to inherited metabolic diseases, chromosomal abnormalities, phakomatoses, or malformations of cortical development is reviewed elsewhere.

RECENT FINDINGS

The use of high-throughput approaches to sequence DNA and to detect copy number variants is revealing a landscape of mutations in genetic epilepsies, affecting a variety of genes involved in neuronal excitability, synaptic transmission, neuronal metabolism, or network development.

SUMMARY

A number of distinct clinical syndromes of pediatric genetic epilepsy have been described and linked to specific gene defects. Phenotypes may include, in addition to epilepsy, variable degrees of intellectual disability, elements of autism spectrum disorders, other psychiatric disorders, and motor impairment. In some cases, these comorbidities derive from uncontrolled seizure activity (epileptic encephalopathies), but in other cases they are direct, multifaceted consequences of global brain dysfunction. Mutations may be de novo, or, when inherited, show reduced penetrance and variable expressivity. Understanding the genetics of these conditions will improve diagnosis, reveal pathogenic mechanisms, and eventually lead to better treatment.

Identification of SCN1A and PCDH19 mutations in Chinese children with Dravet syndrome

BACKGROUND

Dravet syndrome is a severe form of epilepsy. Majority of patients have a mutation in SCN1A gene, which encodes a voltage-gated sodium channel. A recent study has demonstrated that 16% of SCN1A-negative patients have a mutation in PCDH19, the gene encoding protocadherin-19. Mutations in other genes account for only a very small proportion of families. TSPYL4 is a novel candidate gene within the locus 6q16.3-q22.31 identified by linkage study.

OBJECTIVE

The present study examined the mutations in epileptic Chinese children with emphasis on Dravet syndrome.

METHODS

A hundred children with severe epilepsy were divided into Dravet syndrome and non-Dravet syndrome groups and screened for SCN1A mutations by direct sequencing. SCN1A-negative Dravet syndrome patients and patients with phenotypes resembling Dravet syndrome were checked for PCDH19 and TSPYL4 mutations.

RESULTS

Eighteen patients (9 males, 9 females) were diagnosed to have Dravet syndrome. Among them, 83% (15/18) had SCN1A mutations including truncating (7), splice site (2) and missense mutations (6). The truncating/splice site mutations were associated with moderate to severe degree of intellectual disability (p<0.05). During the progression of disease, 73% (11/15) had features fitting into the diagnostic criteria of autism spectrum disorder and 53% (8/15) had history of vaccination-induced seizures. A novel PCDH19 p.D377N mutation was identified in one SCN1A-negative female patient with Dravet syndrome and a known PCDH19 p.N340S mutation in a female non-Dravet syndrome patient. The former also inherited a TSPYL4 p.G60R variant.

CONCLUSION

A high percentage of SCN1A mutations was identified in our Chinese cohort of Dravet syndrome patients but none in the rest of patients. We demonstrated that truncating/splice site mutations were linked to moderate to severe intellectual disability in these patients. A de novo PCDH19 missense mutation together with an inherited TSPYL4 missense variant were identified in a patient with Dravet syndrome.

Febrile seizures: current role of the laboratory investigation and source of the fever in the diagnostic approach

OBJECTIVES

The aim of this study was to analyze the value of performing laboratory tests, taking cultures, and imaging, a diagnostic approach for febrile seizures (FSs) still routinely performed despite the American Academy of Pediatrics recommendations not to. Another aim of this study was to identify the most common sources of fever in patients with FSs and to determine whether the occurrence of FSs correlates with the seasons of the year.

METHODS

This is a retrospective study that included all patients diagnosed with simple or complex FSs who were seen in the emergency room or inpatient unit from January 2004 to December 2009.

RESULTS

Of the 219 patients included in the study, 135 (61.4%) cases had the etiology of the FS diagnosed. Upper respiratory tract infection, otitis media, urinary infection, and pneumonia were the most common diagnoses attributed to the fever. Leukocytosis was present in 48 (24%) of 219, and neutrophilia in 199 (91%) of 219 cases. Low bicarbonate levels were common among every age group. Only 1 blood culture was positive for Salmonella. The incidence of FS was higher during the winter (49.3% of the cases), and it closely paralleled the seasonal variation of viral infections.

CONCLUSIONS

Even though laboratory tests, taking cultures, and imaging are performed in daily practice when approaching FSs, the association of FSs with serious infectious disease is rare and usually overestimated. The diagnostic approach should be individualized to each case and correlated with available data like that shown in this study. Parents should be educated with the knowledge that the occurrence of FSs tends to be higher in winter.

Lack of association between TNF-α gene polymorphisms at position -308 A, -850T and risk of simple febrile convulsion in pediatric patients

Background:

Febrile convulsions (FCs), occurring between 6 months and 6 years of age is the most common seizure disorder during childhood. The febrile response is thought to be mediated by the release of pyrogenic cytokines, such as tumor necrosis factor and interleukin-1 (IL-1). There is a significant relationship between genetic components for susceptibility of FCs and different report mutation. We investigated association between two polymorphisms in the tumor necrosis factor (TNF)-α promoter region (G-308A, C-850T) and FCs in the southwest area of Iran.

Materials and Methods:

In this matched case–control study, 100 patients with febrile convulsion as case group and 130 healthy children as control group were enrolled in the study. Peripheral blood samples were collected and DNA was extracted by standard phenol–chloroform method. The genotype and allele frequencies of TNF- α polymorphisms in case and control groups were determined by using PCR-RFLP (polymerase chain reaction restriction fragment length polymorphism) method. Statistical analysis was done using Chi-square test.

Results:

The average age of case and control groups were 3.4 ± 1.4 and 3.4 ± 1.2 years, respectively. There was no significant difference between age and sex in both the groups (P > 0.05). A family history of febrile convulsion was detected in 44% of patients. Moreover, the simple febrile convulsion was detected in 85% of the case group.

Conclusion:

RFLP analysis of TNF- α promoter region polymorphisms, considering P = 0.146 and P = 0.084 for G-308A and C-850T, respectively, showed no correlation between TNF- α polymorphisms and predisposition to simple febrile, based on the kind of convulsion (atypical and simple febrile convulsion). We found a significant relation between genotype distribution of G-308A and atypical febrile convulsion in case group (P = 0.04). A significant correlation between genotype distribution of G-308A and atypical febrile convulsion in the case group was found, but there was no correlation between TNF- α polymorphisms at positions of -308A, and 850T and predisposition to simple febrile convulsion. Further studies are needed to understand clinical usefulness of this correlation.

The Role of Seizure-Related SEZ6 as a Susceptibility Gene in Febrile Seizures

Sixty cases of febrile seizures from a Chinese cohort had previously been reported with a strong association between variants in the seizure-related (SEZ) 6 gene and febrile seizures. They found a striking lack of genetic variation in their controls. We found genetic variation in SEZ6 at similar levels at the same DNA sequence positions in our 94 febrile seizure cases as in our 96 unaffected controls. Two of our febrile seizure cases carried rare variants predicted to have damaging consequences. Combined with some of the variants from the Chinese cohort, these data are compatible with a role for SEZ6 as a susceptibility gene for febrile seizures. However, the polygenic determinants underlying most cases of febrile seizures with complex inheritance remain to be determined.

A locus for juvenile myoclonic epilepsy maps to 2q33-q36

We performed a whole genome linkage analysis in a three-generation south Indian family with multiple members affected with juvenile myoclonic epilepsy (JME). The maximum two-point LOD score obtained was 3.32 at recombination fraction (theta) = 0 for D2S2248. The highest multipoint score of 3.59 was observed for the genomic interval between D2S2322 and D2S2228 at the chromosomal region 2q33-q36. Proximal and distal boundaries of the critical genetic interval were defined by D2S116 and D2S2390, respectively. A 24-Mb haplotype was found to co-segregate with JME in the family. While any potentially causative variant in the functional candidate genes, SLC4A3, SLC23A3, SLC11A1 and KCNE4, was not detected, we propose to examine brain-expressed NRP2, MAP2, PAX3, GPR1, TNS1 and DNPEP, and other such positional candidate genes to identify the disease-causing gene for the disorder.

Axon initial segment dysfunction in epilepsy

The axon initial segment (AIS) contains the site of action potential initiation and plays a major role in neuronal excitability. AIS function relies on high concentrations of different ion channels and complex regulatory mechanisms that orchestrate molecular microarchitecture. We review recent evidence that a large number of ion channels associated with epilepsy are enriched at the AIS, making it a 'hotspot' for epileptogenesis. Furthermore, we present novel data on the clustering of GABRgamma2 receptors in the AIS of cortical and hippocampal neurons in a knock in mouse model of a human genetic epilepsy. This article highlights the molecular coincidence of epilepsy mutations at the AIS and reviews pathogenic mechanisms converging at the AIS.

The long-term effects of febrile seizures on the hippocampal neuronal plasticity - clinical and experimental evidence

Febrile seizures are the most common seizure disorder in childhood, but their long-term effects on the developing brains especially neuronal injury and neurocognitive function remain unresolved. Recent epidemiological studies reassure that most febrile seizures do not adversely affect global intelligence and hippocampal function, such as memory. However, there are concerns regarding those children who experience febrile seizures during the first postnatal year, having prior developmental delay and pre- or peri-natal events. Magnetic resonance imaging (MRI) studies confirmed that prolonged and focal FS can occasionally produce acute hippocampal injury that evolves into atrophy. Animal studies have revealed that the exposure of hippocampal neurons to experimental febrile seizures early in life, particularly prolonged or frequently repetitive FS, or together with brain malformation, may lead to sustained dysfunction of these cells, in spite of the absence of neuronal damage. Genetic studies suggest that the relationship between febrile seizures and subsequent epilepsy and neurocognitive dysfunction is sometimes genetic, but there are complex interactions with genetic or environmental modifiers. Therefore, there is a small group of children in whom febrile seizures-induced hippocampal injury might occur. Identification of the target population for subsequent mesial temporal sclerosis is important for prevention and early intervention.

Excitatory and inhibitory synaptic transmission is differentially influenced by two ortho-substituted polychlorinated biphenyls in the hippocampal slice preparation

Exposure to polychlorinated biphenyls impairs cognition and behavior in children. Two environmental PCBs 2,2',3,3',4,4',5-heptachlorobiphenyl (PCB170) and 2,2',3,5',6-pentachlorobiphenyl (PCB95) were examined in vitro for influences on synaptic transmission in rat hippocampal slices. Field excitatory postsynaptic potentials (fEPSPs) were recorded in the CA1 region using a multi-electrode array. Perfusion with PCB170 (10 nM) had no effect on fEPSP slope relative to baseline period, whereas (100 nM) initially enhanced then depressed fEPSP slope. Perfusion of PCB95 (10 or 100 nM) persistently enhanced fEPSP slope >200%, an effect that could be inhibited by dantrolene, a drug that attenuates ryanodine receptor signaling. Perfusion with picrotoxin (PTX) to block GABA neurotransmission resulted in a modest increase in fEPSP slope, whereas PTX+PCB170 (1-100 nM) persistently enhanced fEPSP slope in a dose dependent manner. fEPSP slope reached >250% of baseline period in the presence of PTX+100 nM PCB170, conditions that evoked marked epileptiform after-potential discharges. PCB95 and PCB170 were found to differentially influence the Ca(2+)-dependence of [(3)H]ryanodine-binding to hippocampal ryanodine receptors. Non-coplanar PCB congeners can differentially alter neurotransmission in a manner suggesting they can elicit imbalances between inhibitory and excitatory circuits within the hippocampus. Differential sensitization of ryanodine receptors by Ca(2+) appears to mediate, at least in part, hippocampal excitotoxicity by non-coplanar PCBs.

A locus for autosomal dominant reflex epilepsy precipitated by hot water maps at chromosome 10q21.3-q22.3

Hot water epilepsy (HWE) is a form of reflex or sensory epilepsy wherein seizures are precipitated by an unusual stimulus, the contact of hot water over the head and body. Genome-wide linkage analysis of a large family with ten affected members, provided evidence of linkage (Z (max) = 3.17 at theta = 0 for D10S412) to chromosome 10q21. Analysis of five additional HWE families, for markers on chromosome 10, further strengthened the evidence of linkage to the same chromosomal region with three out of five families showing concordance for the disease haplotype and providing a two-point LOD score of 4.86 at theta = 0 and 60% penetrance for D10S412. The centromere-proximal and -distal boundaries of the critical genetic interval of about 15 Mb at 10q21.3-q22.3 were defined by D10S581 and D10S201, respectively. Sequence analysis of a group of functional candidate genes, the ion channels KCNMA1, VDAC2 and solute carriers SLC25A16, SLC29A3 revealed no potentially pathogenic mutation. We propose to carry out further analysis of positional candidate genes from this region to identify the gene responsible for this unusual neurobehavioral phenotype.

FIRST: a practical approach to the causes and management of febrile seizures

During almost 4 decades of clinical practice of pediatrics and pediatric neurology, the senior authors have rarely made a formal presentation on the topic of "febrile seizures." In any large pediatric teaching hospital, questions regarding the diagnosis and management of febrile seizures are raised by medical students, pediatric residents, and adult and pediatric neurology residents. The acronym FIRST was developed as a teaching tool to present a simple and pragmatic clinical approach to children presenting with a single seizure or cluster of seizures in 1 day associated with a febrile illness before, during, or after the seizure event(s). FIRST refers to Febrile, Illness, Related, Seizure(s) and Template, with the latter representing an outline of the basic cause(s). The authors propose the use of the Table as a tool to help determine the underlying etiology of febrile seizures because this is the major factor affecting the choice of treatment.

What's new in: "genetics in childhood epilepsy"

In recent years, different mutations in genes that control the excitability of neurons have been described in idiopathic childhood epilepsies. Most commonly, sodium/potassium channelopathies and GABA-receptor mutations are involved. Major progress has been made in the field of idiopathic generalised epilepsies associated with febrile seizures (GEFS+). It now is becoming clear that mutations should not only be looked for in familial cases, but also in sporadic cases, especially in infants and young children with unexplained severe epileptic encephalopathies. Many studies also define 'epilepsy susceptibility genes', which contribute to one's individual genetic vulnerability to develop epilepsy. It should be realized, however, that in the most common idiopathic benign childhood epilepsies (benign rolandic and occipital epilepsies), major breakthroughs are still awaited. In addition, a better clinical description of the epileptic phenotypes is needed to explain more precisely the genotypic and phenotypic heterogeneity. Genetic studies are nowadays becoming a necessary diagnostic step in the evaluation of idiopathic childhood epilepsies, not only in familial cases, but also in sporadic cases.

Haptoglobin HP2-2 genotype, alpha-thalassaemia and acute seizures in children living in a malaria-endemic area

Polymorphisms of the haptoglobin (HP) gene and deletions in alpha-globin gene (alpha-thalassaemia) are common in malaria-endemic Africa. The same region also has high incidence rates for childhood acute seizures. The haptoglobin HP2-2 genotype has been associated with idiopathic generalized epilepsies and altered iron metabolism in children with alpha-thalassaemia can potentially interfere with neurotransmission and increase the risk of seizures. We investigated the hypothesis that the HP2-2 genotype and the common African alpha-globin gene deletions are associated with the increased risk of seizures. 288 children aged 3-156 months admitted with acute seizures to Kilifi District Hospital (Kenya), were matched for ethnicity to an equal number of community controls. The proportion of cases (72/288 [25.0%]) and controls (80/288 [27.8%]) with HP2-2 genotype was similar, p=0.499. The allele frequency of HP2 gene in cases (49.3%) and controls (48.6%) was also similar, p=0.814. Similarly, we found no significant difference between the proportion of cases (177/267 [66.3%]) and controls (186/267 [69.7%]) with deletions in alpha-globin gene (p=0.403). Among cases, HP2-2 polymorphism and deletions in alpha-globin gene were neither associated with changes in the type, number or duration of seizures nor did they affect outcome. We conclude that the HP2-2 polymorphism and deletions in alpha-globin gene are not risk factors for acute seizures in children. Future studies should examine other susceptibility genes.

Hyperglycosylation and reduced GABA currents of mutated GABRB3 polypeptide in remitting childhood absence epilepsy

Childhood absence epilepsy (CAE) accounts for 10% to 12% of epilepsy in children under 16 years of age. We screened for mutations in the GABA(A) receptor (GABAR) beta 3 subunit gene (GABRB3) in 48 probands and families with remitting CAE. We found that four out of 48 families (8%) had mutations in GABRB3. One heterozygous missense mutation (P11S) in exon 1a segregated with four CAE-affected persons in one multiplex, two-generation Mexican family. P11S was also found in a singleton from Mexico. Another heterozygous missense mutation (S15F) was present in a singleton from Honduras. An exon 2 heterozygous missense mutation (G32R) was present in two CAE-affected persons and two persons affected with EEG-recorded spike and/or sharp wave in a two-generation Honduran family. All mutations were absent in 630 controls. We studied functions and possible pathogenicity by expressing mutations in HeLa cells with the use of Western blots and an in vitro translation and translocation system. Expression levels did not differ from those of controls, but all mutations showed hyperglycosylation in the in vitro translation and translocation system with canine microsomes. Functional analysis of human GABA(A) receptors (alpha 1 beta 3-v2 gamma 2S, alpha 1 beta 3-v2[P11S]gamma 2S, alpha 1 beta 3-v2[S15F]gamma 2S, and alpha 1 beta 3-v2[G32R]gamma 2S) transiently expressed in HEK293T cells with the use of rapid agonist application showed that each amino acid transversion in the beta 3-v2 subunit (P11S, S15F, and G32R) reduced GABA-evoked current density from whole cells. Mutated beta 3 subunit protein could thus cause absence seizures through a gain in glycosylation of mutated exon 1a and exon 2, affecting maturation and trafficking of GABAR from endoplasmic reticulum to cell surface and resulting in reduced GABA-evoked currents.

Voltage-gated sodium channel Nav1.1, Nav1.3 and beta1 subunit were up-regulated in the hippocampus of spontaneously epileptic rat

The spontaneously epileptic rat (SER), a double mutant (zi/zi, tm/tm), exhibits both tonic convulsions and absence-like seizures from the age of 8 weeks. Since the first point mutation in the voltage-gated sodium channel (VGSC) beta(1) subunit in human generalized epilepsy with febrile seizures plus (GEFS+) was identified, more and more types of genetic epilepsy have been causally suggested to be related to gene changes in VGSC. However, there are no reports that can elucidate the effects of VGSC in SER. The present study was undertaken to detect sodium channel I alpha-isoform (Na(v)1.1), sodium channel III alpha-isoform (Na(v)1.3) and beta(1) subunit from both the level of mRNA and protein in SERs hippocampus compared with control Wistar rats. In this study, the mRNA expressions of Na(v)1.1, Na(v)1.3 and beta(1) subunit in SERs hippocampus were significantly higher than those in control rats hippocampus by real-time RT-PCR; The protein distributions and expressions of Na(v)1.1, Na(v)1.3 and beta(1) subunit in SERs hippocampus were detected by immunofluorescence, immunohistochemistry and western blot, and the protein expressions of Na(v)1.1, Na(v)1.3 and beta(1) subunit were significantly increased. In conclusion, our study suggested for the first time that sodium channel Na(v)1.1, Na(v)1.3 and beta(1) subunit up-regulation at the mRNA and protein levels of SER hippocampus might contribute to the generation of epileptiform activity and underlie the observed seizure phenotype in SER. The results of this study may be of value in revealing components of the molecular mechanisms of hippocampal excitation that are related to genetic epilepsy.

Rat epileptic seizures evoked by BmK αIV and its possible mechanisms involved in sodium channels

This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx. Moreover, BmK alphaIV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK alphaIV-evoked epileptic seizures may be involved in the modulation of BmK alphaIV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca(2+) influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK alphaIV in the central nervous system for understanding epileptogenesis involved in sodium channels.

Febrile seizures are associated with mutation of seizure-related (SEZ) 6, a brain-specific gene

Genetic factors contribute significantly to the etiology of febrile seizures (FS), the most common type of seizures in childhood. However, in most patients with FS, the causative gene is unknown. The purpose of this study was to explore the relationship between human brain-specific gene SEZ-6 and FS. Through amplification of genomic DNA by PCR and sequencing of the resulting products, we screened 75 subjects for mutations in the coding region (17 exons) of the SEZ-6 gene. Fifteen subjects were healthy individuals and 60 subjects had FS. Patients with FS could be divided into sub-groups based on seizure type (42 simple and 18 complex) and family history (41 had a positive family history). All patients have been followed to date to evaluate seizure recurrence and the development of epilepsy. No mutations were found in healthy controls, but 21 of the patients with FS had mutations in SEZ-6, and the most common type of mutation was a heterozygous, cytosine insertion (frame shift mutation) at position 1435 of the cDNA. The mutation incidence was significantly higher in patients with complex FS (vs. simple FS) and in patients with a positive family history. Sixteen of 42 patients with simple FS experienced seizure recurrence during the 1-5-year follow-up period. Fifteen of 18 patients with complex FS also experienced a recurrence during this period. Among these patients with recurrences, five patients with simple FS and six patients with complex FS have developed epilepsy. The mutation incidence among these epileptic patients is 72.7%. The human SEZ-6 gene is related to the occurrence and development of FS and may be a novel candidate gene for epilepsy. Screening for mutations in SEZ-6 may be valuable in predicting FS recurrence or the development of epilepsy.