Genetics of epilepsy

Copy Number Variation and Epilepsy: State of the Art in the Era of High-Throughput Sequencing-A Multicenter Cohort Study

BACKGROUND

Genetic epilepsy diagnosis is increasing due to technological advancements. Although the use of molecular diagnosis is increasing, chromosomal microarray analysis (CMA) remains an important diagnostic tool for many patients. We aim to explore the role and indications of CMA in epilepsy, given the current genomic advances.

METHODS

We obtained data from 378 epileptic described patients, who underwent CMA between 2015 and 2021. Different types of syndromic or nonsyndromic epilepsy were represented.

RESULTS

After excluding patients who were undertreated or had missing data, we included 250 patients with treated epilepsy and relevant clinical information. These patients mostly had focal epilepsy or developmental and epileptic encephalopathy, with a median start age of 2 years. Ninety percent of the patients had intellectual disability, more than two thirds had normal head size, and 60% had an abnormal magnetic resonance imaging. We also included 10 patients with epilepsy without comorbidities. In our cohort, we identified 35 pathogenic copy number variations (CNVs) explaining epilepsy with nine recurrent CNVs enriched in patients with epilepsy, 12 CNVs related to neurodevelopmental disorder phenotype with possible epilepsy, five CNVs including a gene already known in epilepsy, and nine CNVs based on size combined with de novo occurrence. The diagnosis rate in our study reached 14% (35 of 250) with first-line CMA, as previously reported. Although targeted gene panel sequencing could potentially diagnose some of the reported epilepsy CNVs (34% [12 of 35]).

CONCLUSIONS

CMA remains a viable option as the first-line genetic test in cases where other genetic tests are not available and as a second-line diagnostic technique if gene panel or exome sequencing yields negative results.

Somatic variants as a cause of drug-resistant epilepsy including mesial temporal lobe epilepsy with hippocampal sclerosis

OBJECTIVE

The contribution of somatic variants to epilepsy has recently been demonstrated, particularly in the etiology of malformations of cortical development. The aim of this study was to determine the diagnostic yield of somatic variants in genes that have been previously associated with a somatic or germline epilepsy model, ascertained from resected brain tissue from patients with multidrug-resistant focal epilepsy.

METHODS

Forty-two patients were recruited across three categories: (1) malformations of cortical development, (2) mesial temporal lobe epilepsy with hippocampal sclerosis, and (3) nonlesional focal epilepsy. Participants were subdivided based on histopathology of the resected brain. Paired blood- and brain-derived DNA samples were sequenced using high-coverage targeted next generation sequencing to high depth (585× and 1360×, respectively). Variants were identified using Genome Analysis ToolKit (GATK4) MuTect-2 and confirmed using high-coverage Amplicon-EZ sequencing.

RESULTS

Sequence data on 41 patients passed quality control. Four somatic variants were validated following amplicon sequencing: within CBL, ALG13, MTOR, and FLNA. The diagnostic yield across 41 patients was 10%, 9% in mesial temporal lobe epilepsy with hippocampal sclerosis and 20% in malformations of cortical development.

SIGNIFICANCE

This study provides novel insights into the etiology of mesial temporal lobe epilepsy with hippocampal sclerosis, highlighting a potential pathogenic role of somatic variants in CBL and ALG13. We also report candidate diagnostic somatic variants in FLNA in focal cortical dysplasia, while providing further insight into the importance of MTOR and related genes in focal cortical dysplasia. This work demonstrates the potential molecular diagnostic value of variants in both germline and somatic epilepsy genes.

Association of epilepsy with neuroimaging patterns in children with cerebral palsy

OBJECTIVES

In this study, we examined whether epilepsy and drug-resistant epilepsy are associated with neuroimaging findings in children with cerebral palsy (CP).

METHODS

Magnetic resonance imaging classification system (MRICS) proposed by Surveillance of Cerebral Palsy in Europe (SCPE) was used for classification of different MRI patterns in patients with cerebral palsy. We reviewed the brain MRI scans and medical records of children with CP who were followed-up in our clinic between 2019 and 2023. Patients were divided into three categories: CP without epilepsy, CP with controlled epilepsy and CP with DRE. MRI patterns were grouped as maldevelopments, predominant white matter injury, predominant gray matter injury, miscellaneous (delayed myelination, cerebral atrophy, cerebellar atrophy, brainstem lesions and calcifications, lesions that were not classified under any other group) and normal according to MRICS of the SCPE.

RESULTS

There were 325 CP patients. The most common MRI patterns were predominant white matter injury (47.6%) and gray matter injury (23.8%). There was a 1.5-fold reduction in the risk of epilepsy in patients with predominant white matter injury (OR = 1.54, 95% CI 1.23-1.94). In contrast, children in the miscellaneous group had significantly higher risks of epilepsy (p < 0.001), and we were able to determine that miscellaneous findings increased the risk by 1.8 times (OR = 1.77, 95% CI 1.47-2.12).

CONCLUSION

In conclusion, more than half of the children with CP had epilepsy, 40.7% of whom had DRE. On MRI, miscellaneous findings may indicate a poor prognosis for epilepsy, while predominant white matter injury may indicate a good outcome. Children with CP, especially those with miscellaneous findings on MRI, should be closely monitored for epilepsy development.

The role of molecular chaperones in the mechanisms of epileptogenesis

Epilepsy is a group of neurological diseases which requires significant economic costs for the treatment and care of patients. The central point of epileptogenesis stems from the failure of synaptic signal transmission mechanisms, leading to excessive synchronous excitation of neurons and characteristic epileptic electroencephalogram activity, in typical cases being manifested as seizures and loss of consciousness. The causes of epilepsy are extremely diverse, which is one of the reasons for the complexity of selecting a treatment regimen for each individual case and the high frequency of pharmacoresistant cases. Therefore, the search for new drugs and methods of epilepsy treatment requires an advanced study of the molecular mechanisms of epileptogenesis. In this regard, the investigation of molecular chaperones as potential mediators of epileptogenesis seems promising because the chaperones are involved in the processing and regulation of the activity of many key proteins directly responsible for the generation of abnormal neuronal excitation in epilepsy. In this review, we try to systematize current data on the role of molecular chaperones in epileptogenesis and discuss the prospects for the use of chemical modulators of various chaperone groups' activity as promising antiepileptic drugs.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

Rodent Models of Audiogenic Epilepsy: Genetic Aspects, Advantages, Current Problems and Perspectives

Animal models of epilepsy are of great importance in epileptology. They are used to study the mechanisms of epileptogenesis, and search for new genes and regulatory pathways involved in the development of epilepsy as well as screening new antiepileptic drugs. Today, many methods of modeling epilepsy in animals are used, including electroconvulsive, pharmacological in intact animals, and genetic, with the predisposition for spontaneous or refractory epileptic seizures. Due to the simplicity of manipulation and universality, genetic models of audiogenic epilepsy in rodents stand out among this diversity. We tried to combine data on the genetics of audiogenic epilepsy in rodents, the relevance of various models of audiogenic epilepsy to certain epileptic syndromes in humans, and the advantages of using of rodent strains predisposed to audiogenic epilepsy in current epileptology.

Fever-Associated Seizures or Epilepsy: An Overview of Old and Recent Literature Acquisitions

In addition to central nervous system infections, seizures and fever may occur together in several neurological disorders. Formerly, based on the clinical features and prognostic evolution, the co-association of seizure and fever included classical febrile seizures (FS) divided into simple, complex, and prolonged FS (also called febrile status epilepticus). Later, this group of disorders has been progressively indicated, with a more inclusive term, as "fever-associated seizures or epilepsy" (FASE) that encompasses: (a) FS divided into simple, complex, and prolonged FS; (b) FS plus; (c) severe myoclonic epilepsy in infancy (Dravet syndrome); (d) genetic epilepsy with FS plus; and (e) febrile infection-related epilepsy syndrome (FIRES). Among the FASE disorders, simple FS, the most common and benign condition, is rarely associated with subsequent epileptic seizures. The correlation of FS with epilepsy and other neurological disorders is highly variable. The pathogenesis of FASE is unclear but immunological and genetic factors play a relevant role and the disorders belonging to the FASE group show to have an underlying common clinical, immunological, and genetic pathway. In this study, we have reviewed and analyzed the clinical data of each of the heterogeneous group of disorders belonging to FASE.

De novo mutations in childhood cases of sudden unexplained death that disrupt intracellular Ca2+ regulation

Approximately 400 United States children 1 y of age and older die suddenly from unexplained causes annually. We studied whole-exome sequence data from 124 “trios” (decedent child and living parents) to identify genetic risk factors. Nonsynonymous mutations, mostly de novo (present in child but absent in both biological parents), were highly enriched in genes associated with cardiac and seizure disorders relative to controls, and contributed to 9% of deaths. We found significant overtransmission of loss-of-function or pathogenic missense variants in cardiac and seizure disorder genes. Most pathogenic variants were de novo in origin, highlighting the importance of trio studies. Many of these pathogenic de novo mutations altered a protein network regulating calcium-related excitability at submembrane junctions in cardiomyocytes and neurons.

Sudden unexplained death in childhood (SUDC) is an understudied problem. Whole-exome sequence data from 124 “trios” (decedent child, living parents) was used to test for excessive de novo mutations (DNMs) in genes involved in cardiac arrhythmias, epilepsy, and other disorders. Among decedents, nonsynonymous DNMs were enriched in genes associated with cardiac and seizure disorders relative to controls (odds ratio = 9.76, P = 2.15 × 10⁻⁴). We also found evidence for overtransmission of loss-of-function (LoF) or previously reported pathogenic variants in these same genes from heterozygous carrier parents (11 of 14 transmitted, P = 0.03). We identified a total of 11 SUDC proband genotypes (7 de novo, 1 transmitted parental mosaic, 2 transmitted parental heterozygous, and 1 compound heterozygous) as pathogenic and likely contributory to death, a genetic finding in 8.9% of our cohort. Two genes had recurrent missense DNMs, RYR2 and CACNA1C. Both RYR2 mutations are pathogenic (P = 1.7 × 10⁻⁷) and were previously studied in mouse models. Both CACNA1C mutations lie within a 104-nt exon (P = 1.0 × 10⁻⁷) and result in slowed L-type calcium channel inactivation and lower current density. In total, six pathogenic DNMs can alter calcium-related regulation of cardiomyocyte and neuronal excitability at a submembrane junction, suggesting a pathway conferring susceptibility to sudden death. There was a trend for excess LoF mutations in LoF intolerant genes, where ≥1 nonhealthy sample in denovo-db has a similar variant (odds ratio = 6.73, P = 0.02); additional uncharacterized genetic causes of sudden death in children might be discovered with larger cohorts.

Nonsyndromic Early-Onset Epileptic Encephalopathies: Two Novel KCTD7 Pathogenic Variants and a Literature Review

Early-onset epileptic encephalopathies (EOEE) affect cognitive, sensory, and motor development. Genetic variations are among the identifiable primary causes of these syndromes. However, some patients have been reported to be affected by EOEE without any other clinical symptoms and signs. We study the genotype and phenotype of patients with nonsyndromic early-onset epileptic encephalopathy (NSEOEE) and report 2 novel patients from Iran. A comprehensive search was conducted in PubMed, John Willy, Springer, Elsevier, and Google Scholar databases to collect related information of all the previously reported cases with KCTD7 mutations. Fifty-four patients (from 40 families) were investigated. Using trio-whole-exome sequencing (trio-WES) and Sanger sequencing, the possible genetic causes of the disorder were checked. The probable impacts of the identified variants on the KCTD7 protein structure and function were predicted. This study provided a detailed overview of all published KCTD7 mutations and 2 de novo ones. We identified 2 novel homozygous variants of uncertain significance, c.458 G > A p. Arg153His and c.529C > T (p.Arg177Cys), in KCTD7 (NM_153033.4) (Chr7(GRCh37)). There is a significant wide distribution of the KCTD7 gene causing NSEOEE among different populations. In conclusion, KCTD7 mutations demonstrate a diverse geographical distribution alongside a wide range of ethnicities. This highlights the importance of careful consideration in the WES data analysis. Mutations of this gene may be a common cause of NSEOEE. Also, this study imprints targeted therapeutic opportunities for potassium channelepsies such as KCTD7-related NSEOEE.

Genetic cause of epilepsy in a Greek cohort of children and young adults with heterogeneous epilepsy syndromes

We describe a cohort of 10 unrelated Greek patients (4 females, 6 males; median age 6.5 years, range 2-18 years) with heterogeneous epilepsy syndromes with a genetic basis. In these patients, causative genetic variants, including two novel ones, were identified in 9 known epilepsy-related genes through whole exome sequencing. A patient with glycine encephalopathy was a compound heterozygote for the p.Arg222Cys and the p.Ser77Leu AMT variant. A patient affected with Lafora disease carried the homozygous p.Arg171His EPM2A variant. A de novo heterozygous variant in the GABRG2 gene (p.Pro282Thr) was found in one patient and a pathogenic variant in the GRIN2B gene (p.Gly820Val) in another patient. Infantile-onset lactic acidosis with seizures was associated with the p.Arg446Ter PDHX gene variant in one patient. In two additional epilepsy patients, the p.Ala1662Val and the novel non-sense p.Phe1330Ter SCN1A gene variants were found. Finally, in 3 patients we observed a novel heterozygous missense variant in SCN2A (p.Ala1874Thr), a heterozygous splice site variant in SLC2A1 (c.517-2A>G), as a cause of Glut1 deficiency syndrome, and a pathogenic variant in STXBP1 (p.Arg292Leu), respectively. In half of our cases (patients with variants in the GRIN2B, SCN1A, SCN2A and SLC2A1 genes), a genetic cause with potential management implications was identified.

Prospects and Limitations Related to the Use of MicroRNA as a Biomarker of Epilepsy in Children: A Systematic Review

Epilepsy is one of the most common neurological diseases in children. There is an unmet need for new objective methods that would facilitate and accelerate the diagnostic process, thus improving the prognosis. In many studies, the participation of microRNA in epileptogenesis has been confirmed. Therefore, it seems to be a promising candidate for this role. Scientists show the possibility of using microRNAs as diagnostic and predictive biomarkers as well as novel therapeutic targets. Children with epilepsy would benefit particularly from the use of this innovative method. However, the number of studies related to this age group is very limited. This review is based on 10 studies in children and summarizes the information collected from studies on animal models and the adult population. A total of 136 manuscripts were included in the analysis. The aim of the review was to facilitate the design of studies in children and to draw attention to the challenges and traps related to the analysis of the results. Our review suggests a high potential for the use of microRNAs and the need for further research.

Modeling the Interactions Between Sodium Channels Provides Insight Into the Negative Dominance of Certain Channel Mutations

BACKGROUND

Nav1.5 cardiac Na+ channel mutations can cause arrhythmogenic syndromes. Some of these mutations exert a dominant negative effect on wild-type channels. Recent studies showed that Na+ channels can dimerize, allowing coupled gating. This leads to the hypothesis that allosteric interactions between Na+ channels modulate their function and that these interactions may contribute to the negative dominance of certain mutations.

METHODS

To investigate how allosteric interactions affect microscopic and macroscopic channel function, we developed a modeling paradigm in which Markovian models of two channels are combined. Allosteric interactions are incorporated by modifying the free energies of the composite states and/or barriers between states.

RESULTS

Simulations using two generic 2-state models (C-O, closed-open) revealed that increasing the free energy of the composite states CO/OC leads to coupled gating. Simulations using two 3-state models (closed-open-inactivated) revealed that coupled closings must also involve interactions between further composite states. Using two 6-state cardiac Na+ channel models, we replicated previous experimental results mainly by increasing the energies of the CO/OC states and lowering the energy barriers between the CO/OC and the CO/OO states. The channel model was then modified to simulate a negative dominant mutation (Nav1.5 p.L325R). Simulations of homodimers and heterodimers in the presence and absence of interactions showed that the interactions with the variant channel impair the opening of the wild-type channel and thus contribute to negative dominance.

CONCLUSION

Our new modeling framework recapitulates qualitatively previous experimental observations and helps identifying possible interaction mechanisms between ion channels.

Functional Genomics of Epileptogenesis in Animal Models and Humans

It has been estimated that epilepsies are among the top five neurological diseases with the highest burden of disease. In recent years, genome-wide expression studies (GWES) have been carried out in experimental models of epilepsy and in samples from human patients. In this study, I carried out meta-analyses and analyses of convergence for available GWES for epileptogenesis in humans and in mouse, rat, zebrafish and fruit fly models. Multiple lines of evidence (such as genome-wide association data and known druggable genes) were integrated to prioritize top candidate genes for epileptogenesis and a functional enrichment analysis was carried out. Several top candidate genes, which are supported by multiple lines of genomic evidence, such as GRIN1, KCNAB1 and STX1B, were identified. Druggable genes of potential interest (such as GABRA2, GRIK1, KCNAB1 and STX4) were also identified. An enrichment of genes regulated by the MEF2 and SOX5 transcription factors and the miR-106b-5p and miR-101-3p miRNAs was found. The current work is the first meta-analysis and convergent analysis of GWES for epileptogenesis in humans and in multiple animal models, integrating results from several genomic studies. Novel candidate genes and pathways for epileptogenesis were identified in this analysis.

Cardiac and neuronal HCN channelopathies

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed as four different isoforms (HCN1-4) in the heart and in the central and peripheral nervous systems. In the voltage range of activation, HCN channels carry an inward current mediated by Na⁺ and K⁺, termed I_f in the heart and I_h in neurons. Altered function of HCN channels, mainly HCN4, is associated with sinus node dysfunction and other arrhythmias such as atrial fibrillation, ventricular tachycardia, and atrioventricular block. In recent years, several data have also shown that dysfunctional HCN channels, in particular HCN1, but also HCN2 and HCN4, can play a pathogenic role in epilepsy; these include experimental data from animal models, and data collected over genetic mutations of the channels identified and characterized in epileptic patients. In the central nervous system, alteration of the I_h current could predispose to the development of neurodegenerative diseases such as Parkinson's disease; since HCN channels are widely expressed in the peripheral nervous system, their dysfunctional behavior could also be associated with the pathogenesis of neuropathic pain. Given the fundamental role played by the HCN channels in the regulation of the discharge activity of cardiac and neuronal cells, the modulation of their function for therapeutic purposes is under study since it could be useful in various pathological conditions. Here we review the present knowledge of the HCN-related channelopathies in cardiac and neurological diseases, including clinical, genetic, therapeutic, and physiopathological aspects.

The voltage-gated sodium channel inhibitor, 4,9-anhydrotetrodotoxin, blocks human Nav1.1 in addition to Nav1.6

Voltage-gated sodium channels (VGSCs) are responsible for the initiation and propagation of action potentials in neurons. The human genome includes ten human VGSC α-subunit genes, SCN(X)A, encoding Nav1.1-1.9 plus Nax. To understand the unique role that each VGSC plays in normal and pathophysiological function in neural networks, compounds with high affinity and selectivity for specific VGSC subtypes are required. Toward that goal, a structural analog of the VGSC pore blocker tetrodotoxin, 4,9-anhydrotetrodotoxin (4,9-ah-TTX), has been reported to be more selective in blocking Na+ current mediated by Nav1.6 than other TTX-sensitive VGSCs, including Nav1.2, Nav1.3, Nav1.4, and Nav1.7. While SCN1A, encoding Nav1.1, has been implicated in several neurological diseases, the effects of 4,9-ah-TTX on Nav1.1-mediated Na+ current have not been tested. Here, we compared the binding of 4,9-ah-TTX for human and mouse brain preparations, and the effects of 4,9-ah-TTX on human Nav1.1-, Nav1.3- and Nav1.6-mediated Na+ currents using the whole-cell patch clamp technique in heterologous cells. We show that, while 4,9-ah-TTX administration results in significant blockade of Nav1.6-mediated Na+ current in the nanomolar range, it also has significant effects on Nav1.1-mediated Na+ current. Thus, 4,9-ah-TTX is not a useful tool in identifying Nav1.6-specific effects in human brain networks.

Abnormal expression of GABAA receptor subunits and hypomotility upon loss of gabra1 in zebrafish

We used whole-exome sequencing (WES) to determine the genetic etiology of a patient with a multi-system disorder characterized by a seizure phenotype. WES identified a heterozygous de novo missense mutation in the GABRA1 gene (c.875C>T). GABRA1 encodes the alpha subunit of the gamma-aminobutyric acid receptor A (GABAAR). The GABAAR is a ligand gated ion channel that mediates the fast inhibitory signals of the nervous system, and mutations in the subunits that compose the GABAAR have been previously associated with human disease. To understand the mechanisms by which GABRA1 regulates brain development, we developed a zebrafish model of gabra1 deficiency. gabra1 expression is restricted to the nervous system and behavioral analysis of morpholino injected larvae suggests that the knockdown of gabra1 results in hypoactivity and defects in the expression of other subunits of the GABAAR. Expression of the human GABRA1 protein in morphants partially restored the hypomotility phenotype. In contrast, the expression of the c.875C>T variant did not restore these behavioral deficits. Collectively, these results represent a functional approach to understand the mechanisms by which loss-of-function alleles cause disease.

Parental report of quality of life in children with epilepsy: A Spanish/French comparison

BACKGROUND

Epilepsy is a chronic neurological condition that affects the quality of life (QoL) of patients and their families. In this study, we compare two sets of reports on QoL that were completed by two samples of parents whose children have epilepsy.

METHOD

Parents of children with various types of epilepsy from Spain (N = 196) and France (N = 219) completed the same QoL questionnaire. Medical variables were recorded from the referred specialist doctor for each patient.

RESULTS

The factors associated with parental reports on QoL were similar in both countries. Parents of children with nonidiopathic generalized or unclassified epilepsy reported poorer QoL and the highest proportion of learning and behavioral problems. However, the intensity of difficulties varied between the two samples.

CONCLUSIONS

This questionnaire made it possible to detect comorbidities and daily life difficulties in children with epilepsy and their families. The type of epilepsy had the same influence on Spanish and French families' ratings of QoL. Families shared the same comorbidities in terms of hyperactivity/attention/sociability problems. Nevertheless, the intensity of reported difficulties varied in both countries, possibly because of differences in cultural and educational environments. This aspect should be further explored in future research.

Epilepsy Benchmarks Area I: Understanding the Causes of the Epilepsies and Epilepsy-Related Neurologic, Psychiatric, and Somatic Conditions

The 2014 NINDS Benchmarks for Epilepsy Research included area I: Understand the causes of the epilepsies and epilepsy-related neurologic, psychiatric, and somatic conditions. In preparation for the 2020 Curing Epilepsies Conference, where the Benchmarks will be revised, this review will cover scientific progress toward that Benchmark, with emphasize on studies since 2016.

Progress of Induced Pluripotent Stem Cell Technologies to Understand Genetic Epilepsy

The study of the pathomechanisms by which gene mutations lead to neurological diseases has benefit from several cellular and animal models. Recently, induced Pluripotent Stem Cell (iPSC) technologies have made possible the access to human neurons to study nervous system disease-related mechanisms, and are at the forefront of the research into neurological diseases. In this review, we will focalize upon genetic epilepsy, and summarize the most recent studies in which iPSC-based technologies were used to gain insight on the molecular bases of epilepsies. Moreover, we discuss the latest advancements in epilepsy cell modeling. At the two dimensional (2D) level, single-cell models of iPSC-derived neurons lead to a mature neuronal phenotype, and now allow a reliable investigation of synaptic transmission and plasticity. In addition, functional characterization of cerebral organoids enlightens neuronal network dynamics in a three-dimensional (3D) structure. Finally, we discuss the use of iPSCs as the cutting-edge technology for cell therapy in epilepsy.

The role of somatic mutational events in the pathogenesis of epilepsy

PURPOSE OF REVIEW

There has been rapid progress in defining novel causative gene variants responsible for a large spectrum of human epilepsy syndromes and subtypes. Of particular interest is the discovery that somatic mutations, for example, noninherited mutations occurring in neuroglial progenitor cells during embryonic brain development, are highly linked to malformations of cortical development (MCD) such as focal cortical dysplasia (FCD) type II and hemimegalencephaly.

RECENT FINDINGS

Somatic gene variants have been identified in genes encoding regulatory proteins within the mechanistic target of rapamycin (mTOR) signaling cascade and have thus comprised the group classified as mTORopathies. FCD II and hemimegalencephaly often result from mutations in identical genes suggesting that these are spectrum disorders. An exciting recent development has been the identification of somatic mutations causing both FCD Ia and nonlesional neocortical epilepsy.

SUMMARY

Defining somatic gene mutations in brain tissue specimens has shed new light on how MCD form and the mechanisms of epileptogenesis associated with MCD. Trials of mTOR inhibitors in tuberous sclerosis complex have demonstrated that inhibition of mTOR activation in mTORopathies can reduce seizure frequency. New somatic mutations found for a variety of epilepsy syndromes may provide new targets for clinical therapeutics.

Mapping the knowledge structure and trends of epilepsy genetics over the past decade: A co-word analysis based on medical subject headings terms

INTRODUCTION

Over the past 10 years, epilepsy genetics has made dramatic progress. This study aimed to analyze the knowledge structure and the advancement of epilepsy genetics over the past decade based on co-word analysis of medical subject headings (MeSH) terms.

METHODS

Scientific publications focusing on epilepsy genetics from the PubMed database (January 2009-December 2018) were retrieved. Bibliometric information was analyzed quantitatively using Bibliographic Item Co-Occurrence Matrix Builder (BICOMB) software. A knowledge social network analysis and publication trend based on the high-frequency MeSH terms was built using VOSviewer.

RESULTS

According to the search strategy, a total of 5185 papers were included. Among all the extracted MeSH terms, 86 high-frequency MeSH terms were identified. Hot spots were clustered into 5 categories including: "ion channel diseases," "beyond ion channel diseases," "experimental research & epigenetics," "single nucleotide polymorphism & pharmacogenetics," and "genetic techniques". "Epilepsy," "mutation," and "seizures," were located at the center of the knowledge network. "Ion channel diseases" are typically in the most prominent position of epilepsy genetics research. "Beyond ion channel diseases" and "genetic techniques," however, have gradually grown into research cores and trends, such as "intellectual disability," "infantile spasms," "phenotype," "exome," " deoxyribonucleic acid (DNA) copy number variations," and "application of next-generation sequencing." While ion channel genes such as "SCN1A," "KCNQ2," "SCN2A," "SCN8A" accounted for nearly half of epilepsy genes in MeSH terms, a number of additional beyond ion channel genes like "CDKL5," "STXBP1," "PCDH19," "PRRT2," "LGI1," "ALDH7A1," "MECP2," "EPM2A," "ARX," "SLC2A1," and more were becoming increasingly popular. In contrast, gene therapies, treatment outcome, and genotype-phenotype correlations were still in their early stages of research.

CONCLUSION

This co-word analysis provides an overview of epilepsy genetics research over the past decade. The 5 research categories display publication hot spots and trends in epilepsy genetics research which could consequently supply some direction for geneticists and epileptologists when launching new projects.

Harnessing ionic mechanisms to achieve disease modification in neurodegenerative disorders

Progressive neuronal death is the key pathogenic event leading to clinical symptoms in neurodegenerative disorders (NDDs). Neuroprotective treatments are virtually unavailable, partly because of the marked internal heterogeneity of the mechanisms underlying pathology. Targeted neuroprotection would require deep mechanistic knowledge across the entire aetiological spectrum of each NDD and the development of tailored treatments. Although ideal, this strategy appears challenging, as it would require a degree of characterization of both the disease and the patient that is currently unavailable. The alternate strategy is to search for commonalities across molecularly distinct NDD forms and exploit these for the development of drugs with broad-spectrum efficacy. In this view, mounting evidence points to ionic mechanisms (IMs) as targets with potential therapeutic efficacy across distinct NDD subtypes. The scope of this review is to present clinical and preclinical evidence supporting the link between disruption of IMs and neuronal death in specific NDDs and to critically revise past and ongoing attempts of harnessing IMs for the development of neuroprotective treatments.

Epidemiology and familial clustering of pediatric epilepsy in the geographic isolate of Ischia

BACKGROUND

Geographic isolates are the ideal setting to study the genetic background and the epidemiology of epilepsy. There are only few published reports on the epidemiology of pediatric epilepsy in geographic isolates.

METHODS

This study was performed in the Ischia island, district of Napoli (Southern Italy). The local population includes 61,086 individuals, 8381 of them aged from 0 to 14 years. We included children with two or more unprovoked seizures or one unprovoked seizure associated to a high risk of relapse, observed from 2004 to 2017. Neonatal, febrile and acute symptomatic seizures were excluded. Eligible patients were identified through the local pediatricians' medical records. All probands and their parents underwent a face-to-face interview. Clinical charts were reviewed and electroclinical diagnoses were confirmed by two authors (AC, VB).

RESULTS

Thirty-six children and adolescents were included. Overall, the prevalence of epilepsy in the Ischia island was 4.3 per 1,000 (95% CI 3.0-5.9). Incidence was 51.7 per 100,000 person-years (95% CI 36.2-71.6). Sixteen (44.4%) patients had a genetic (idiopathic) origin and 20 (55.6%) a symptomatic (structural/metabolic) etiology. Nine probands (25%) had at least one family member with epilepsy (including third-degree relatives). Their pedigrees were suggestive of dominant inheritance in six and of recessive inheritance in three families.

CONCLUSIONS

The epidemiological features of pediatric epilepsy in this geographic isolate are similar to the general population. A family history was reported in one fourth of the patients with a wide clinical heterogeneity, likely reflecting genetic heterogeneity in this population.