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Abstract Genetic epilepsy with febrile seizures plus (GEFS+) is a genetic epilepsy syndrome characterized by a marked hereditary tendency inherited as an autosomal dominant trait. Patients with GEFS+ may develop typical febrile seizures (FS), while generalized tonic–clonic seizures (GTCSs) with fever commonly occur between 3 months and 6 years of age, which is generally followed by febrile seizure plus (FS+), with or without absence seizures, focal seizures, or GTCSs. GEFS+ exhibits significant genetic heterogeneity, with polymerase chain reaction, exon sequencing, and single nucleotide polymorphism analyses all showing that the occurrence of GEFS+ is mainly related to mutations in the gamma-aminobutyric acid type A receptor gamma 2 subunit (GABRG2) gene. The most common mutations in GABRG2 are separated in large autosomal dominant families, but their pathogenesis remains unclear. The predominant types of GABRG2 mutations include missense (c.983A → T, c.245G → A, p.Met199Val), nonsense (R136*, Q390*, W429*), frameshift (c.1329delC, p.Val462fs*33, p.Pro59fs*12), point (P83S), and splice site (IVS6+2T → G) mutations. All of these mutations types can reduce the function of ion channels on the cell membrane; however, the degree and mechanism underlying these dysfunctions are different and could be linked to the main mechanism of epilepsy. The γ2 subunit plays a special role in receptor trafficking and is closely related to its structural specificity. This review focused on investigating the relationship between GEFS+ and GABRG2 mutation types in recent years, discussing novel aspects deemed to be great significance for clinically accurate diagnosis, anti-epileptic treatment strategies, and new drug development.

Genetic epilepsy with febrile seizures plus (GEFS+) is a genetic epilepsy syndrome characterized by a marked hereditary tendency inherited as an autosomal dominant trait. Patients with GEFS+ may develop typical febrile seizures (FS), while generalized tonic–clonic seizures (GTCSs) with fever commonly occur between 3 months and 6 years of age, which is generally followed by febrile seizure plus (FS+), with or without absence seizures, focal seizures, or GTCSs. GEFS+ exhibits significant genetic heterogeneity, with polymerase chain reaction, exon sequencing, and single nucleotide polymorphism analyses all showing that the occurrence of GEFS+ is mainly related to mutations in the gamma-aminobutyric acid type A receptor gamma 2 subunit (GABRG2) gene. The most common mutations in GABRG2 are separated in large autosomal dominant families, but their pathogenesis remains unclear. The predominant types of GABRG2 mutations include missense (c.983A → T, c.245G → A, p.Met199Val), nonsense (R136*, Q390*, W429*), frameshift (c.1329delC, p.Val462fs*33, p.Pro59fs*12), point (P83S), and splice site (IVS6+2T → G) mutations. All of these mutations types can reduce the function of ion channels on the cell membrane; however, the degree and mechanism underlying these dysfunctions are different and could be linked to the main mechanism of epilepsy. The γ2 subunit plays a special role in receptor trafficking and is closely related to its structural specificity. This review focused on investigating the relationship between GEFS+ and GABRG2 mutation types in recent years, discussing novel aspects deemed to be great significance for clinically accurate diagnosis, anti-epileptic treatment strategies, and new drug development. [ABSTRACT FROM AUTHOR]

Genetic epilepsy with febrile seizures plus (GEFSP) is a familial epileptic syndrome that is genetically heterogeneous and inherited in an autosomal dominant form in most cases. To date, at least seven genes have been reported to associate with GEFSP. This study aimed to identify the disease-causing variant in a Chinese Tujia ethnic family with GEFSP by using whole exome sequencing, Sanger sequencing, and in silico prediction. A heterozygous missense variant c.5725A>G (p.T1909A) was identified in the sodium voltage-gated channel alpha subunit 1 gene (SCN1A) coding region. The variant co-segregated with the GEFSP phenotype in this family, and it was predicted as disease-causing by multiple in silico programs, which was proposed as the genetic cause of GEFSP, further genetically diagnosed as GEFSP2. These findings expand the genetic and phenotypic spectrum of GEFSP and should contribute to genetic diagnoses, personalized therapies, and prognoses.

Febrile seizures (FS) occur in about 2–3% of children aged 3 months to 5 years. Atypical febrile seizures are those with a focal component. Each subsequent febrile attack increases the risk of transformation into epilepsy. After the third febrile seizure, the risk of additional episodes of febrile seizures is already approaching 50%, and the risk of formation of epilepsy is 15.8%. Recent studies show the great contribution of genetic causes to the development of genetic epilepsy with febrile seizures plus (GEFS+). GEFS+ includes a combination of some febrile seizures with subsequent afebrile attack, or recurring febrile seizures after 6 years. The genetic causes of GEFS+ are both monogenic (in particular, disorders in the SCN1B, SCN1A, GABRG2, GABRD, SCN9A, STX1B, HCN1 genes, etc.) and copy number variations. Twin methods suggest that different genetic factors play a role in the case of FS, FS+ and FS with subsequent epilepsy. Genetic cause can be found in about 30% of cases, that affects not only the final diagnosis and prognosis for the patient, but also the prevention of disease in the family. In GEFS+ seizures are usually generalized tonic-clonic, less often myoclonic, myoclonic-atonic seizures, absences and status epilepticus, but sometimes they also describe focal seizures. The clinical picture of patients with GEFS+ varies from family febrile seizures (the least severe cases) to Drave-like syndrome (the most severe cases), although all of them have a predominantly normal level of intellect.

• GABRG2 gene knockout cell model was established using CRISPR/Cas9 system. • GABRG2 KO altered the expression of other GABARs subunits at different temperatures. • Expression of CACNA1 decreased as temperature increased. • Expression of MMP3, MMP9, and MMP13 was upregulated at 37°C. • MAPK and PI3K-Akt signaling pathways were significantly altered. Mutations in γ-aminobutyric acid A receptor (GABA A) subunits and sodium channel genes, especially GABRG2 and SCN1A , have been reported to be associated with febrile seizures (FS) and genetic epilepsy with febrile seizures plus (GEFS+). GEFS+ is a well-known family of epileptic syndrome with autosomal dominant inheritance in children. Its most common phenotypes are febrile seizures often with accessory afebrile generalized tonic-clonic seizures, febrile seizures plus (FS+), severe epileptic encephalopathy, as well as other types of generalized or localization-related seizures. However, the pathogenesis of febrile seizures remains largely unknown. Here, we generated a GABRG2 gene knockout cell line (HT22 GABRG2KO) by applying the CRISPR/Cas9-mediated genomic deletion in HT-22 mouse hippocampal neuronal cell line to explore the function of GABRG2 in vitro. With mRNA-seq, we found significant changes in the expression profiles of several epilepsy-related genes when GABRG2 was knockout, some of them showing temperature-induced changes as well. Kyoto Encyclopedia Gene and Genomic (KEGG) analysis revealed a significant alteration in the MAPK and PI3K-Akt signaling pathways. We also observed an up-regulation of the matrix metalloproteinases (MMPs) family after GABRG2 knockout. Furthermore, the significant decrease in expression of GABRA1 and CACNA1A (but not others) with an increase in temperature is a novel finding. In summary, mutations in the GABA A receptor can lead to a decrease in numbers of receptors, which may cause the impairment of GABAergic pathway signaling. This data has been the first time to reveal that GABRG2 mutations would affect the function of other genes, and based on this finding we hope this work would also provide a new direction for the research of GABRG2 in GEFS+. It also may provide a molecular basis for the severity of epilepsy, and guide the clinical medication for the treatment of the epilepsy focused on the function on GABA A receptors, which, might be a new strategy for genetic diagnosis and targeted treatment of epilepsy. [ABSTRACT FROM AUTHOR]

Genetic epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome in which affected individuals may have a variety of epilepsy phenotypes, the most common being febrile seizures (FS) and febrile seizures plus (FS+). We investigated the possible contribution of copy number variation to GEFS+. We searched our epilepsy research database for patients in GEFS + families who underwent chromosomal microarray analysis. We reviewed the clinical features and results of genetic testing in these families. Of twelve families with available microarray data, four had at least one copy number variant (CNV) identified. In Family 1, the proband had a maternally-inherited 15q11.2 deletion. In Family 5, four different CNVs were identified, variably present in the affected individuals; this included a 19p13.3 deletion affecting CACNA1A. Finally, in both Families 9 and 10, the proband had Dravet syndrome with pathogenic SCN1A variant, as well as a CNV (10q11.22 duplication in Family 9 and 22q11.2 deletion in Family 10). The significance of these specific variants is difficult to precisely determine; however, there appeared to be an overrepresentation of CNVs in this small cohort. These findings suggest chromosomal microarray analysis could have clinical utility as part of the workup in GEFS + families. • The frequency of copy number variants (CNVs) in GEFS + families was reviewed. • Seven CNVs were identified, distributed among 4 of the 12 GEFS + families studied. • Two CNVs were classified likely pathogenic, 4 uncertain significance, and 1 benign. • Likely pathogenic variants were deletions at 15q11.2 (263 kb) and 19p13.13 (67 kb). • The 19p13.13 deletion was intragenic, affecting only CACNA1A. [ABSTRACT FROM AUTHOR]

Summary: Pathogenic SCN1A/NaV1.1 mutations cause well‐defined epilepsies, including genetic epilepsy with febrile seizures plus (GEFS+) and the severe epileptic encephalopathy Dravet syndrome. In addition, they cause a severe form of migraine with aura, familial hemiplegic migraine. Moreover, SCN1A/NaV1.1 variants have been inferred as risk factors in other types of epilepsy. We review here the advancements obtained studying pathologic mechanisms of SCN1A/NaV1.1 mutations with experimental systems. We present results gained with in vitro expression systems, gene‐targeted animal models, and the induced pluripotent stem cell (iPSC) technology, highlighting advantages, limits, and pitfalls for each of these systems. Overall, the results obtained in the last two decades confirm that the initial pathologic mechanism of epileptogenic SCN1A/NaV1.1 mutations is loss‐of‐function of NaV1.1 leading to hypoexcitability of at least some types of γ‐aminobutyric acid (GABA)ergic neurons (including cortical and hippocampal parvalbumin‐positive and somatostatin‐positive ones). Conversely, more limited results point to NaV1.1 gain‐of‐function for familial hemiplegic migraine (FHM) mutations. Behind these relatively simple pathologic mechanisms, an unexpected complexity has been observed, in part generated by technical issues in experimental studies and in part related to intrinsically complex pathophysiologic responses and remodeling, which yet remain to be fully disentangled. [ABSTRACT FROM AUTHOR]

Summary: Pathogenic SCN1A/NaV1.1 mutations cause well‐defined epilepsies, including genetic epilepsy with febrile seizures plus (GEFS+) and the severe epileptic encephalopathy Dravet syndrome. In addition, they cause a severe form of migraine with aura, familial hemiplegic migraine. Moreover, SCN1A/NaV1.1 variants have been inferred as risk factors in other types of epilepsy. We review here the advancements obtained studying pathologic mechanisms of SCN1A/NaV1.1 mutations with experimental systems. We present results gained with in vitro expression systems, gene‐targeted animal models, and the induced pluripotent stem cell (iPSC) technology, highlighting advantages, limits, and pitfalls for each of these systems. Overall, the results obtained in the last two decades confirm that the initial pathologic mechanism of epileptogenic SCN1A/NaV1.1 mutations is loss‐of‐function of NaV1.1 leading to hypoexcitability of at least some types of γ‐aminobutyric acid (GABA)ergic neurons (including cortical and hippocampal parvalbumin‐positive and somatostatin‐positive ones). Conversely, more limited results point to NaV1.1 gain‐of‐function for familial hemiplegic migraine (FHM) mutations. Behind these relatively simple pathologic mechanisms, an unexpected complexity has been observed, in part generated by technical issues in experimental studies and in part related to intrinsically complex pathophysiologic responses and remodeling, which yet remain to be fully disentangled. [ABSTRACT FROM AUTHOR]

Highlights • Sudden unexpected death rarely occurs in GEFS + families. • Two GEFS + families with sodium channel gene mutations (SCN1A and SCN1B) are described. • In both families, an affected child suffered sudden death. • Presence of sodium channel mutation may increase sudden death risk in GEFS + families. • Genetic testing in GEFS + may provide information that aids mortality risk counseling. Abstract We aimed to describe families with genetic epilepsy with febrile seizures plus (GEFS+) in which individuals suffered sudden unexpected death. The Epilepsy Pharmacogenomics Research Database was reviewed for GEFS + families in which at least one individual had suffered sudden death, and two families were identified. In Family A, five males had febrile seizures and one girl had febrile seizures plus. The latter died at 22 months of age and was classified as definite SUDEP. Molecular genetic testing identified a pathogenic SCN1B variant. In Family B, two brothers had recurrent focal status epilepticus with fever, and were classified as having atypical multifocal Dravet syndrome. The elder brother died suddenly at seven years of age, but was not classified SUDEP because the event occurred following status epilepticus. SCN1A sequencing in the surviving brother identified a likely pathogenic variant. These two cases of sudden death in GEFS + families with likely pathogenic variants in sodium channel genes demonstrate that sudden death may occur in GEFS+, even with mild phenotypes. The presence of sodium channel variants may have further increased the sudden death risk, particularly in the case of SCN1B , a gene which has also been associated with cardiac conditions including Brugada syndrome and long QT. [ABSTRACT FROM AUTHOR]

Genetic epilepsy with febrile seizures plus ( GEFS+) is a familial epilepsy syndrome characterized by heterogeneous phenotypes ranging from mild disorders such as febrile seizures to epileptic encephalopathies ( EEs) such as Dravet syndrome ( DS). Although DS often occurs with de novo SCN1A pathogenic variants, milder GEFS+ spectrum phenotypes are associated with inherited pathogenic variants. We identified seven cases with non- EE GEFS+ phenotypes and de novo SCN1A pathogenic variants, including a monozygotic twin pair. Febrile seizures plus ( FS+) occurred in six patients, five of whom had additional seizure types. The remaining case had childhood-onset temporal lobe epilepsy without known febrile seizures. Although early development was normal in all individuals, three later had learning difficulties, and the twin girls had language impairment and working memory deficits. All cases had SCN1A missense pathogenic variants that were not found in either parent. One pathogenic variant had been reported previously in a case of DS, and the remainder were novel. Our finding of de novo pathogenic variants in mild phenotypes within the GEFS+ spectrum shows that mild GEFS+ is not always inherited. SCN1A screening should be considered in patients with GEFS+ phenotypes because identification of pathogenic variants will influence antiepileptic therapy, and prognostic and genetic counseling. [ABSTRACT FROM AUTHOR]

De novo loss-of-function mutations in the voltage-gated sodium channel (VGSC) SCN1A (encoding Nav1.1) are the main cause of Dravet syndrome (DS), a catastrophic early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), refractory afebrile epilepsy, cognitive and behavioral deficits, and a 15-20% mortality rate. SCN1A mutations also lead to genetic epilepsy with febrile seizures plus (GEFS+), which is an inherited disorder characterized by early-life FSs and the development of a range of adult epilepsy subtypes. Current antiepileptic drugs often fail to protect against the severe seizures and behavioral and cognitive deficits found in patients with SCN1A mutations. To address the need for more efficacious treatments for SCN1A-derived epilepsies, we evaluated the therapeutic potential of Huperzine A, a naturally occurring reversible acetylcholinesterase inhibitor. In CF1 mice, Hup A (0.56 or 1 mg/kg) was found to confer protection against 6 Hz-, pentylenetetrazole (PTZ)-, and maximal electroshock (MES)-induced seizures. Robust protection against 6 Hz-, MES-, and hyperthermia-induced seizures was also achieved following Hup A administration in mouse models of DS (Scn1a+/-) and GEFS+ (Scn1aRH/+). Furthermore, Hup A-mediated seizure protection was sustained during 3 weeks of daily injections in Scn1aRH/+ mutants. Finally, we determined that the muscarinic and GABAA receptors play a role in Hup A-mediated seizure protection. These findings indicate that Hup A might provide a novel therapeutic strategy for increasing seizure resistance in DS and GEFS+, and more broadly, in other forms of refractory epilepsy.

Objective · To explore the correlation of febrile seizure (FS) with voltage-gated sodium channel alpha 1 subtype (SCN1A) gene exons 25, 26 and 3'UTR region in children from Shanghai chongming County. Methods · The genomic DNA in peripheral venous blood was extracted from 96 children with FS (including 32 cases of genetic epilepsy with febrile seizures plus [GEFS+]) and 53 healthy controls. PCR amplification and sequencing analysis were performed for SCN1A gene exons 25, 26 and 3'UTR region. Results · No mutation in SCN1A gene exons E25, E26 was found in both groups. For 3'UTR region, c.310311 delgt GT variation was found in 1 case of GEFS+, c.589 T> G variation in 2 cases of FS, and c.593 T>G variation in 6 cases, while no mutation was found in the control group. Reported frequencies of single nucleotide polymorphism (SNP) c.1025T>C were 18.2% (the case group) and 24.5% (the control group). The difference between two groups was not statistically significant. Prediction results showed that 114 microRNAs could bind with the 3'UTR region of SCN1A gene. C.310-311 delGT was not located in the sequence where miRNAs bound with 3'UTR region of SCN1A gene, while c. 589 T>G and c.593 T > G variations were located in this sequence. Conclusion · No mutation was found in SCN1Agene exons E25, E26. The c. 310-311delGT, c.589 T > G, and c. 593 T > G variations were found in 3'UTR region. There is no obvious correlation between SNPc.1025T>C and FS. [ABSTRACT FROM AUTHOR]

De novo loss-of-function mutations in the voltage-gated sodium channel (VGSC) SCN1A (encoding Nav1.1) are the main cause of Dravet syndrome (DS), a catastrophic early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), refractory afebrile epilepsy, cognitive and behavioral deficits, and a 15-20% mortality rate. SCN1A mutations also lead to genetic epilepsy with febrile seizures plus (GEFS+), which is an inherited disorder characterized by early-life FSs and the development of a range of adult epilepsy subtypes. Current antiepileptic drugs often fail to protect against the severe seizures and behavioral and cognitive deficits found in patients with SCN1A mutations. To address the need for more efficacious treatments for SCN1A-derived epilepsies, we evaluated the therapeutic potential of Huperzine A, a naturally occurring reversible acetylcholinesterase inhibitor. In CF1 mice, Hup A (0.56 or 1 mg/kg) was found to confer protection against 6 Hz-, pentylenetetrazole (PTZ)-, and maximal electroshock (MES)-induced seizures. Robust protection against 6 Hz-, MES-, and hyperthermia-induced seizures was also achieved following Hup A administration in mouse models of DS (Scn1a+/-) and GEFS+ (Scn1aRH/+). Furthermore, Hup A-mediated seizure protection was sustained during 3 weeks of daily injections in Scn1aRH/+ mutants. Finally, we determined that muscarinic and GABAA receptors play a role in Hup A-mediated seizure protection. These findings indicate that Hup A might provide a novel therapeutic strategy for increasing seizure resistance in DS and GEFS+, and more broadly, in other forms of refractory epilepsy. [ABSTRACT FROM AUTHOR]

Mutations of the SCN1A subunit of the sodium channel is a cause of genetic epilepsy with febrile seizures plus ( GEFS+) in multiplex families and accounts for 70-80% of Dravet syndrome ( DS). DS cases without SCN1A mutation inherited have predicted SCN9A susceptibility variants, which may contribute to complex inheritance for these unexplained cases of DS. Compared with controls, DS cases were significantly enriched for rare SCN9A genetic variants. None of the multiplex febrile seizure or GEFS+ families could be explained by highly penetrant SCN9A mutations. [ABSTRACT FROM AUTHOR]

Abstract: Mutations in SCN2A, the gene encoding α2 subunit of the neuronal sodium channel, are associated with a variety of epilepsies: benign familial neonatal–infantile seizures (BFNIS); genetic epilepsy with febrile seizures plus (GEFS+); Dravet syndrome (DS); and some intractable childhood epilepsies. More than 10 new mutations have been identified in BFNIS, all of them are missense. To date, only one nonsense mutation has been found in a patient with intractable childhood epilepsy and severe mental decline. Recently, microduplication of chromosome 2q24.3 (containing eight genes including SCN2A, SCN3A, and the 3′ end of SCN1A) was reported in a family with dominantly inherited neonatal seizures and intellectual disability. Functional studies of SCN2A mutations show that they can cause divergent biophysical defects in NaV1.2 and impair cell surface expressions. There is no consistent relationship between genotype and phenotype. [Copyright &y& Elsevier]

Purpose: We evaluated the ability of the ketogenic diet (KD) to improve thresholds to flurothyl-induced seizures in two mouse lines with Scn1a mutations: one that models Dravet syndrome (DS) and another that models genetic (generalized) epilepsy with febrile seizures plus (GEFS+). Methods: At postnatal day 21, mouse models of DS and GEFS+ were fasted for 12-14 h and then placed on either a 6:1 (fats to proteins and carbohydrates) KD or a standard diet (SD) for 2 weeks. At the end of the 2-week period, we measured thresholds to seizures induced by the chemiconvulsant flurothyl. Body weight, β-hydroxybutyrate (BHB) levels, and glucose levels were also recorded every 2 days over a 2-week period in separate cohorts of mutant and wild-type mice that were either on the KD or the SD. Key Findings: Mice on the KD gained less weight and exhibited significantly higher BHB levels compared to mice on the SD. It is notable that thresholds to flurothyl-induced seizures were restored to more normal levels in both mouse lines after 2 weeks on the KD. Significance: These results indicate that the KD may be an effective treatment for refractory patients with SCN1A mutations. The availability of mouse models of DS and GEFS+ also provides an opportunity to better understand the mechanism of action of the KD, which may facilitate the development of improved treatments. [ABSTRACT FROM AUTHOR]

Abstract: Rare GABAA receptor γ2 and α1 subunit mutations of pathogenic effect have been described segregating in families with “monogenic” epilepsies. We now report globally on the genetic variation contained within all 16 neuronal GABAA receptor subunit genes from the one patient cohort. The cohort consists of GEFS+, FS, and IGE subgroups as either sporadic cases or index cases from small families, with one index case from one large IGE family. The rarity of mutations and coding variation in general across all of the subunits suggests a low tolerance for mutations affecting GABA mediated neuronal inhibition. Characterization of the broader channelopathy load associated with susceptibility to these common epilepsies mostly with complex genetics will need to be expanded beyond the family of GABAA receptor subunits to all families of neuronal ion channels and their interacting molecules by systematic mutation detection associated with functional investigation of their naturally occurring genetic variations. [Copyright &y& Elsevier]

Genetic epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome in which affected individuals within a family typically have a variety of epilepsy phenotypes, varying from simple febrile seizures and febrile seizures plus with a good outcome to severe epileptic encephalopathies. Here, we review the spectrum of epilepsy phenotypes, the genetic architecture of GEFS+, and the implicated genes. Using an illustrative clinical case study, we describe important steps in managing patients with GEFS+: making the diagnosis of GEFS+, appropriate genetic testing, and counselling.

Objectives: Generalized epilepsy with febrile seizures plus (GEFS+) is a new epilepsy syndrome named by the International League Against Epilepsy (ILAE) in 2001. The SCN2A gene encoding α2 subunit of the neuronal sodium channel has been reported to be associated with BFNIS, GFES+, Dravet syndrome and some intractable childhood epilepsies. This study aimed to develop an approach based on next-generation sequencing to determine the genetic defects in a monozygotic twin family with GEFS+., Patients and Methods: We collected a twin family with GEFS+. The DNA of the twin patients was extracted from their peripheral venous whole blood. A total of 308 known genes related to epilepsies were selected for deep exon resequencing. The patients family's DNA was sequenced through Sanger's sequencing for expanded validation. Through systematic data analysis using established bioinformatics pipeline and segregation analysis techniques, a number of genetic variants were released., Results: Through detailed data analysis, we found a new heterozygous mutation c.1399G > A on exon11 of SCN2A (Nav1.2) which has not been reported in the HGMD (Human Gene Mutation Database), in the twin patients. Then we tested and verified the presence of the same mutation site in all individuals of the family. Asymptomatic individuals of this family didn't show this mutation., Conclusion: The methodology provides a reliable strategy for routine gene diagnosis of GEFS+. This observation of a potentially pathogenic mutation of SCN2A (Nav1.2) indicates that this gene should be further evaluated in order to determine possible routes of causation of GEFS+., (Copyright © 2017. Published by Elsevier B.V.)