Subtle Brain Developmental Abnormalities in the Pathogenesis of Juvenile Myoclonic Epilepsy

Bromodomain and Extraterminal Domain Protein 2 in Multiple Human Diseases

Bromodomain and extraterminal domain protein 2 (BRD2), a member of the bromodomain and extraterminal domain (BET) protein family, is a crucial epigenetic regulator with significant function in various diseases and cellular processes. The central function of BRD2 is modulating gene transcription by binding to acetylated lysine residues on histones and transcription factors. This review highlights key findings on BRD2 in recent years, emphasizing its roles in maintaining genomic stability, influencing chromatin spatial organization, and participating in transcriptional regulation. BRD2's diverse functions are underscored by its involvement in diseases such as malignant tumors, neurologic disorders, inflammatory conditions, metabolic diseases, and virus infection. Notably, the potential role of BRD2 as a diagnostic marker and therapeutic target is discussed in the context of various diseases. Although pan inhibitors targeting the BET family have shown promise in preclinical studies, a critical need exists for the development of highly selective BRD2 inhibitors. In conclusion, this review offers insights into the multifaceted nature of BRD2 and calls for continued research to unravel its intricate mechanisms and harness its therapeutic potential. SIGNIFICANCE STATEMENT: BRD2 is involved in the occurrence and development of diseases through maintaining genomic stability, influencing chromatin spatial organization, and participating in transcriptional regulation. Targeting BRD2 through protein degradation-targeting complexes technology is emerging as a promising therapeutic approach for malignant cancer and inflammatory diseases.

Diffusion tensor imaging in photosensitive and nonphotosensitive juvenile myoclonic epilepsy

INTRODUCTION/BACKGROUND

Juvenile myoclonic epilepsy (JME) syndrome is known to cause alterations in brain structure and white matter integrity. The study aimed to determine structural white matter changes in patients with JME and to reveal the differences between the photosensitive (PS) and nonphotosensitive (NPS) subgroups by diffusion tensor imaging (DTI) using the tract-based spatial statistics (TBSS) method.

METHODS

This study included data from 16 PS, 15 NPS patients with JME, and 41 healthy participants. The mean fractional anisotropy (FA) values of these groups were calculated, and comparisons were made via the TBSS method over FA values in the whole-brain and 81 regions of interest (ROI) obtained from the John Hopkins University White Matter Atlas.

RESULTS

In the whole-brain TBSS analysis, no significant differences in FA values were observed in pairwise comparisons of JME patient group and subgroups with healthy controls (HCs) and in comparison between JME subgroups. In ROI-based TBSS analysis, an increase in FA values of right anterior corona radiata and left corticospinal pathways was found in JME patient group compared with HC group. When comparing JME-PS patients with HCs, an FA increase was observed in the bilateral anterior corona radiata region, whereas when comparing JME-NPS patients with HCs, an FA increase was observed in bilateral corticospinal pathway. Moreover, in subgroup comparison, an increase in FA values was noted in corpus callosum genu region in JME-PS compared with JME-NPS.

CONCLUSIONS

Our results support the disruption in thalamofrontal white matter integrity in JME, and subgroups and highlight the importance of using different analysis methods to show the underlying microstructural changes.

Heterozygous RELN missense variants associated with genetic generalized epilepsy

PURPOSE

The RELN gene encodes the secreted glycoprotein Reelin and has important functions in both developing and adult brains. In this study, we aimed to explore the association between the RELN and genetic generalized epilepsy (GGE).

METHODS

We performed whole-exome sequencing on a cohort of 92 patients with GGE. Based on amino acid sequence alignments, allele frequency, pedigree validation and computational modeling, the RELN variants were identified and clinical features of cases were summarized. Cell-based Reelin secretion assays were examined by Western blotting. Alterations of mutant Reelin transport through the secretion pathway were detected by immunofluorescence staining.

RESULTS

Three novel pathogenic RELN variants (3.26%; c.2260C>T/p.R754W, c.2914C>G/p.P972A and c.3029G>A/p.R1010H) were identified. All probands showed adolescence-onset generalized seizures characterized by generalized epileptiform discharges with normal EEG backgrounds, no or mild cognitive impairment, and responded well to anti-seizure medications. All these variants were located in the central regions from 1B to 2A consecutive repeats, and protein modeling demonstrated structural alterations in Reelin. Moreover, we found that these heterozygous missense variants significantly decreased the secretion of mutant proteins in HEK-293T cells, and this impairment was due to the altered transport of mutant Reelin in the secretion pathway.

CONCLUSION

These results suggest that RELN is potentially associated with GGE. The phenotype of GGE caused by RELN variants is relatively mild, and the pathogenic mechanism may involve a loss-of-function.

Early onset ataxia with comorbid myoclonus and epilepsy: A disease spectrum with shared molecular pathways and cortico-thalamo-cerebellar network involvement

OBJECTIVES

Early onset ataxia (EOA) concerns a heterogeneous disease group, often presenting with other comorbid phenotypes such as myoclonus and epilepsy. Due to genetic and phenotypic heterogeneity, it can be difficult to identify the underlying gene defect from the clinical symptoms. The pathological mechanisms underlying comorbid EOA phenotypes remain largely unknown. The aim of this study is to investigate the key pathological mechanisms in EOA with myoclonus and/or epilepsy.

METHODS

For 154 EOA-genes we investigated (1) the associated phenotype (2) reported anatomical neuroimaging abnormalities, and (3) functionally enriched biological pathways through in silico analysis. We assessed the validity of our in silico results by outcome comparison to a clinical EOA-cohort (80 patients, 31 genes).

RESULTS

EOA associated gene mutations cause a spectrum of disorders, including myoclonic and epileptic phenotypes. Cerebellar imaging abnormalities were observed in 73-86% (cohort and in silico respectively) of EOA-genes independently of phenotypic comorbidity. EOA phenotypes with comorbid myoclonus and myoclonus/epilepsy were specifically associated with abnormalities in the cerebello-thalamo-cortical network. EOA, myoclonus and epilepsy genes shared enriched pathways involved in neurotransmission and neurodevelopment both in the in silico and clinical genes. EOA gene subgroups with myoclonus and epilepsy showed specific enrichment for lysosomal and lipid processes.

CONCLUSIONS

The investigated EOA phenotypes revealed predominantly cerebellar abnormalities, with thalamo-cortical abnormalities in the mixed phenotypes, suggesting anatomical network involvement in EOA pathogenesis. The studied phenotypes exhibit a shared biomolecular pathogenesis, with some specific phenotype-dependent pathways. Mutations in EOA, epilepsy and myoclonus associated genes can all cause heterogeneous ataxia phenotypes, which supports exome sequencing with a movement disorder panel over conventional single gene panel testing in the clinical setting.

Variation in prognosis and treatment outcome in juvenile myoclonic epilepsy: a Biology of Juvenile Myoclonic Epilepsy Consortium proposal for a practical definition and stratified medicine classifications

Reliable definitions, classifications and prognostic models are the cornerstones of stratified medicine, but none of the current classifications systems in epilepsy address prognostic or outcome issues. Although heterogeneity is widely acknowledged within epilepsy syndromes, the significance of variation in electroclinical features, comorbidities and treatment response, as they relate to diagnostic and prognostic purposes, has not been explored. In this paper, we aim to provide an evidence-based definition of juvenile myoclonic epilepsy showing that with a predefined and limited set of mandatory features, variation in juvenile myoclonic epilepsy phenotype can be exploited for prognostic purposes. Our study is based on clinical data collected by the Biology of Juvenile Myoclonic Epilepsy Consortium augmented by literature data. We review prognosis research on mortality and seizure remission, predictors of antiseizure medication resistance and selected adverse drug events to valproate, levetiracetam and lamotrigine. Based on our analysis, a simplified set of diagnostic criteria for juvenile myoclonic epilepsy includes the following: (i) myoclonic jerks as mandatory seizure type; (ii) a circadian timing for myoclonia not mandatory for the diagnosis of juvenile myoclonic epilepsy; (iii) age of onset ranging from 6 to 40 years; (iv) generalized EEG abnormalities; and (v) intelligence conforming to population distribution. We find sufficient evidence to propose a predictive model of antiseizure medication resistance that emphasises (i) absence seizures as the strongest stratifying factor with regard to antiseizure medication resistance or seizure freedom for both sexes and (ii) sex as a major stratifying factor, revealing elevated odds of antiseizure medication resistance that correlates to self-report of catamenial and stress-related factors including sleep deprivation. In women, there are reduced odds of antiseizure medication resistance associated with EEG-measured or self-reported photosensitivity. In conclusion, by applying a simplified set of criteria to define phenotypic variations of juvenile myoclonic epilepsy, our paper proposes an evidence-based definition and prognostic stratification of juvenile myoclonic epilepsy. Further studies in existing data sets of individual patient data would be helpful to replicate our findings, and prospective studies in inception cohorts will contribute to validate them in real-world practice for juvenile myoclonic epilepsy management.

Inhibition of Calcium-Sensing Receptor Alleviates Chronic Intermittent Hypoxia-Induced Cognitive Dysfunction via CaSR-PKC-ERK1/2 Pathway

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is typically characterized by chronic intermittent hypoxia (CIH), associated with cognitive dysfunction in children. Calcium-sensing receptor (CaSR) mediates the apoptosis of hippocampal neurons in various diseases. However, the effect of CaSR on OSAHS remains elusive. In the present study, we investigated the role of CaSR in CIH-induced memory dysfunction and underlying mechanisms on regulation of PKC-ERK1/2 signaling pathway in vivo and in vitro. CIH exposures for 4 weeks in mice, modeling OSAHS, contributed to cognitive dysfunction. CIH accelerated apoptosis of hippocampal neurons and resulted in the synaptic plasticity deficit via downregulated synaptophysin (Syn) protein level. The mice were intraperitoneally injected with CaSR inhibitor (NPS2143) 30 min before CIH exposure and the results demonstrated CaSR inhibitor alleviated the apoptosis and synaptic plasticity deficit in the hippocampus of CIH mice. We established intermittent hypoxia PC12 cell model and found that the activation of CaSR accelerated CIH-induced PC12 apoptosis and synaptic plasticity deficit by upregulated p-ERK1/2 and PKC. Overall, our findings revealed that CaSR held a critical function on CIH-induced cognitive dysfunction in mice by accelerating hippocampal neuronal apoptosis and reducing synaptic plasticity via augmenting CaSR-PKC-ERK1/2 pathway; otherwise, inhibition of CaSR alleviated CIH-induced cognitive dysfunction.

The phenotypic spectrum associated with loss-of-function variants in monogenic epilepsy genes in the general population

Variants in monogenic epilepsy genes can cause phenotypes of varying severity. For example, pathogenic variants in the SCN1A gene can cause the severe, sporadic, and drug-resistant Dravet syndrome or the milder familiar GEFS + syndrome. We hypothesized that coding variants in epilepsy-associated genes could lead to other disease-related phenotypes in the general population. We selected 127 established monogenic epilepsy genes and explored rare loss-of-function (LoF) variant associations with 3700 phenotypes across 281,850 individuals from the UK Biobank with whole-exome sequencing data. For 5.5% of epilepsy genes, we found significant associations of LoF variants with non-epilepsy phenotypes, mostly related to mental health. These findings suggest that LoF variants in epilepsy genes are associated with neurological or psychiatric phenotypes in the general population. The evidence provided may warrant further research and genetic screening of patients with atypical presentation and inform clinical care of comorbid disorders in individuals with monogenic epilepsy forms.

Development and Validation of MRI-Based Radiomics Models for Diagnosing Juvenile Myoclonic Epilepsy

OBJECTIVE

Radiomic modeling using multiple regions of interest in MRI of the brain to diagnose juvenile myoclonic epilepsy (JME) has not yet been investigated. This study aimed to develop and validate radiomics prediction models to distinguish patients with JME from healthy controls (HCs), and to evaluate the feasibility of a radiomics approach using MRI for diagnosing JME.

MATERIALS AND METHODS

A total of 97 JME patients (25.6 ± 8.5 years; female, 45.5%) and 32 HCs (28.9 ± 11.4 years; female, 50.0%) were randomly split (7:3 ratio) into a training (n = 90) and a test set (n = 39) group. Radiomic features were extracted from 22 regions of interest in the brain using the T1-weighted MRI based on clinical evidence. Predictive models were trained using seven modeling methods, including a light gradient boosting machine, support vector classifier, random forest, logistic regression, extreme gradient boosting, gradient boosting machine, and decision tree, with radiomics features in the training set. The performance of the models was validated and compared to the test set. The model with the highest area under the receiver operating curve (AUROC) was chosen, and important features in the model were identified.

RESULTS

The seven tested radiomics models, including light gradient boosting machine, support vector classifier, random forest, logistic regression, extreme gradient boosting, gradient boosting machine, and decision tree, showed AUROC values of 0.817, 0.807, 0.783, 0.779, 0.767, 0.762, and 0.672, respectively. The light gradient boosting machine with the highest AUROC, albeit without statistically significant differences from the other models in pairwise comparisons, had accuracy, precision, recall, and F1 scores of 0.795, 0.818, 0.931, and 0.871, respectively. Radiomic features, including the putamen and ventral diencephalon, were ranked as the most important for suggesting JME.

CONCLUSION

Radiomic models using MRI were able to differentiate JME from HCs.

Increased prevalence of minor physical anomalies in patients with epilepsy

Our aim was to investigate the rate and topological profile of minor physical anomalies (MPAs) in adult patients with epilepsy with the use of the Méhes Scale, a comprehensive modern scale of dysmorphology. Consecutive epilepsy patients admitted for outpatient evaluation were included. Patients with comorbidities of neurodevelopmental origin (such as autism, severe intellectual disability, attention deficit hyperactivity disorder, schizophrenia, tic disorder, Tourette syndrome, bipolar disorder, specific learning disorder and specific language impairment) were excluded. All participants underwent physical examination with the use of the Méhes Scale for evaluation of MPAs, including 57 minor signs. The frequency and topological profile of MPAs were correlated to clinical patient data using Kruskal–Wallis, chi2 tests and logistic regression model. 235 patients were included, according to the following subgroups: acquired epilepsy (non-genetic, non-developmental etiology) [N = 63], temporal lobe epilepsy with hippocampal sclerosis (TLE with HS) [N = 27], epilepsy with cortical dysgenesis etiology [N = 29], cryptogenic epilepsy [N = 69] and idiopathic generalized epilepsy (IGE) [N = 47]. As controls, 30 healthy adults were recruited. The frequency of MPAs were significantly affected by the type of epilepsy [H(6) = 90.17; p < 0.001]. Pairwise comparisons showed that all patient groups except for acquired epilepsy were associated with increased frequency of MPAs (p < 0.001 in all cases). Furrowed tongue and high arched palate were more common compared to controls in all epilepsy subgroup except for TLE (p < 0.001 or p = 0.001 in all cases). A positive association was detected between the occurrence of MPAs and antiepileptic drug therapy resistance [Exp(B) = 4.19; CI 95% 1.37–12.80; p = 0.012]. MPAs are more common in patients with epilepsy, which corroborates the emerging concept of epilepsy as a neurodevelopmental disorder. Assessment of these signs may contribute to the clarification of the underlying etiology. Moreover, as increased frequency of MPAs may indicate pharmacoresistance, the identification of patients with high number of MPAs could allow evaluation for non-pharmacological treatment in time.

Correlations Between Structural Brain Abnormalities, Cognition and Electroclinical Characteristics in Patients With Juvenile Myoclonic Epilepsy

Objective

To explore the structural brain abnormality and its relationship with neuropsychological disorders and electroclinical characteristics in juvenile myoclonic epilepsy (JME) patients.

Methods

Sixty-seven patients diagnosed with JME and 56 healthy controls were enrolled. All subjects underwent MRI using T1-weighted 3D brain structural images with 1 mm thickness. Voxel-based morphometry (VBM) and surface-based morphometry (SBM) analyses were performed. They also underwent a series of neuropsychological tests to assess cognitive function. The correlation analyses were conducted between structural changes, neuropsychological outcomes, and electroclinical features.

Results

The gray matter concentration (GMC) was decreased in the bilateral pre-central and post-central gyrus, right anterior cingulate gyrus, left posterior orbital region, bilateral occipital regions, bilateral hippocampus and bilateral caudate nucleus in the JME groups (corrected P < 0.05). The evaluation of gray matter volume (GMV) showed significant decrease respectively in bilateral pre-central and post-central gyrus, left paracentral lobule, left orbital gyrus, left amygdala, left basal ganglia and left thalamus of JME patients (P < 0.05). The cortex thicknesses of the right inferior temporal gyrus, right insular gyrus, and right cingulate gyrus had negative correlations with the disease duration significantly. At the same time, the whole-brain white matter volume was positively associated with the course of the disease (P < 0.05). Patients with persistent abnormal EEG discharges had significantly less whole-brain gray matter volume than JME patients with normal EEG (P = 0.03). Correlation analyses and linear regression analyses showed that, in addition to the gray matter volumes of frontal and parietal lobe, the temporal lobe, as well as the basal ganglia and thalamus, were also significantly correlated with neuropsychological tests' results (P < 0.05).

Conclusion

The JME patients showed subtle structural abnormalities in multiple brain regions that were not only limited to the frontal lobe but also included the thalamus, basal ganglia, parietal lobe, temporal lobe and some occipital cortex, with significant involvement of the primary somatosensory cortex and primary motor cortex. And we significantly demonstrated a correlation between structural abnormalities and cognitive impairment. In addition, the course of disease and abnormal discharges had a specific negative correlation with the structural changes.

Parvalbumin Role in Epilepsy and Psychiatric Comorbidities: From Mechanism to Intervention

Parvalbumin is a calcium-binding protein present in inhibitory interneurons that play an essential role in regulating many physiological processes, such as intracellular signaling and synaptic transmission. Changes in parvalbumin expression are deeply related to epilepsy, which is considered one of the most disabling neuropathologies. Epilepsy is a complex multi-factor group of disorders characterized by periods of hypersynchronous activity and hyperexcitability within brain networks. In this scenario, inhibitory neurotransmission dysfunction in modulating excitatory transmission related to the loss of subsets of parvalbumin-expressing inhibitory interneuron may have a prominent role in disrupted excitability. Some studies also reported that parvalbumin-positive interneurons altered function might contribute to psychiatric comorbidities associated with epilepsy, such as depression, anxiety, and psychosis. Understanding the epileptogenic process and comorbidities associated with epilepsy have significantly advanced through preclinical and clinical investigation. In this review, evidence from parvalbumin altered function in epilepsy and associated psychiatric comorbidities were explored with a translational perspective. Some advances in potential therapeutic interventions are highlighted, from current antiepileptic and neuroprotective drugs to cutting edge modulation of parvalbumin subpopulations using optogenetics, designer receptors exclusively activated by designer drugs (DREADD) techniques, transcranial magnetic stimulation, genome engineering, and cell grafting. Creating new perspectives on mechanisms and therapeutic strategies is valuable for understanding the pathophysiology of epilepsy and its psychiatric comorbidities and improving efficiency in clinical intervention.

Leu226Trp CACNA1A variant associated with juvenile myoclonic epilepsy with and without intellectual disability

OBJECTIVE

Epilepsy is a disease of Central Nervous System (CNS) characterized by abnormal brain activity and recurrent seizures and is considered a clinically and genetically heterogeneous disease. Here, we investigated pathogenic genetic alteration and described the clinical characteristics of three Iranian family members affected by Idiopathic Generalized Epilepsy (IGE) with and without intellectual disability.

METHODS

A non-consanguineous Iranian family with juvenile myoclonic epilepsy was enrolled in the study. The comprehensive neurological evaluation included motor and sensory skills, vision, hearing, speech, coordination, and mood. Whole-exome Sequencing (WES) was performed on the proband to detect probable pathogenic variant, and after the filtering process, probable variants were evaluated with familial segregation analysis using Sanger sequencing.

RESULTS

Using WES, we identified a heterozygous missense substitution (NM_023035.3:c.T677G:p.Leu226Trp) in CACNA1A gene in the studied family with juvenile myoclonic epilepsy with and without intellectual disability and psychiatric phenotype. Considering the patients' clinical synopsis, familial segregation analysis, and literature review, we postulated this variant to be causative of the disease. Indeed, the resulting missense mutation of Leu226Trp affects a highly conserved residue supporting our hypothesis that this mutation is potentially pathogenic.

CONCLUSION

To the best of our knowledge, this is the first report of juvenile myoclonic epilepsy related to CACNA1A gene. Our results provide evidence for expanding the clinical and molecular findings related to the CACNA1A gene.

A systematic review of resting-state and task-based fmri in juvenile myoclonic epilepsy

Functional neuroimaging modalities have enhanced our understanding of juvenile myoclonic epilepsy (JME) underlying neural mechanisms. Due to its non-invasive, sensitive and analytical nature, functional magnetic resonance imaging (fMRI) provides valuable insights into relevant functional brain networks and their segregation and integration properties. We systematically reviewed the contribution of resting-state and task-based fMRI to the current understanding of the pathophysiology and the patterns of seizure propagation in JME Altogether, despite some discrepancies, functional findings suggest that corticothalamo-striato-cerebellar network along with default-mode network and salience network are the most affected networks in patients with JME. However, further studies are required to investigate the association between JME's main deficiencies, e.g., motor and cognitive deficiencies and fMRI findings. Moreover, simultaneous electroencephalography-fMRI (EEG-fMRI) studies indicate that alterations of these networks play a role in seizure modulation but fall short of identifying a causal relationship between altered functional properties and seizure propagation. This review highlights the complex pathophysiology of JME, which necessitates the design of more personalized diagnostic and therapeutic strategies in this group.

Diagnostic and therapeutic approach to drug-resistant juvenile myoclonic epilepsy

INTRODUCTION

Juvenile myoclonic epilepsy (JME), also known as Janz syndrome, is a common form of generalized epilepsy of presumed genetic origin representing up to 10% of all epilepsy cases. Despite adequate anti-seizure medication (ASM) treatment, seizures persist in one-third of JME patients.

AREAS COVERED

A literature search was conducted using Pubmed search on the topics of drug-resistant JME.

EXPERT OPINION

About 30% of JME patients are drug-resistant. Valproate (VPA) is considered the first-choice drug. In women of childbearing potential, levetiracetam (LEV) should represent the first-choice treatment. Alternative monotherapy or add-on therapy should be considered in subjects with resistant seizures after the exclusion of pseudo-drug resistance. The choice of the add-on ASM depends on the predominant seizure type. In subjects with persistent bilateral tonic-clonic seizures, LEV or lamotrigine should be firstly considered. In patients with difficult-to-treat myoclonic seizures, clonazepam or LEV are recommended. In case of persistent absences, ethosuximide should be considered. With appropriate selection and safeguards in place, VPA should remain available as an option in women of childbearing potential whose seizures are resistant to other treatments.

Effects of sevoflurane general anesthesia during early pregnancy on AIM2 expression in the hippocampus and parietal cortex of Sprague-Dawley offspring rats

The aim of the present study was to investigate the effect of exposure to sevoflurane general anesthesia during early pregnancy on interferon-inducible protein AIM2 (AIM2) expression in the hippocampus and parietal cortex of the offspring Sprague-Dawley (SD) rats. A total of 18 SD rats at a gestational age of 5-7 days were randomly divided into three groups: i) A control group (control); ii) 2-h sevoflurane general anesthesia, group 1 (S1); and iii) 4-h sevoflurane general anesthesia, group 2 (S2). The six offspring rats in each group were maintained for 30 days and assessed by Morris water maze testing. Brain specimens were collected from offspring rats 30 days after birth. Changes in the structural morphology of neurons in the hippocampus and parietal cortex were observed using hematoxylin and eosin staining. Nissl bodies in the hippocampus and parietal cortex were observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), AIM2, CD45 and IL-1β was detected by immunohistochemistry and the protein levels of CD45, IL-1β, pro-caspase-1 and caspase-1 p10 were detected by western blotting. Compared with the control group, offspring rats in the S1 and S2 groups exhibited poor long-term learning and memory ability and experienced different degrees of damage to both the hippocampus and parietal cortex. The expression levels of GFAP, AIM2, CD45, IL-1β, caspase-1 and caspase-1 p10 in the offspring of both the S1 and the S2 groups were significantly increased (P<0.05) compared with offspring of the control group. Moreover, compared with the offspring of the S1 group, hippocampal and parietal cortex injury in the offspring of the S2 group was further aggravated, and the expression of GFAP, AIM2, CD45, IL-1β, pro-caspase-1 and cleaved-caspase-1 was significantly increased (P<0.05). In conclusion, sevoflurane general anesthesia in SD rat early pregnancy promoted the expression of AIM2 and the inflammatory response in the hippocampus and parietal cortex of offspring rats.

Genetic Landscape of Common Epilepsies: Advancing towards Precision in Treatment

Epilepsy, a neurological disease characterized by recurrent seizures, is highly heterogeneous in nature. Based on the prevalence, epilepsy is classified into two types: common and rare epilepsies. Common epilepsies affecting nearly 95% people with epilepsy, comprise generalized epilepsy which encompass idiopathic generalized epilepsy like childhood absence epilepsy, juvenile myoclonic epilepsy, juvenile absence epilepsy and epilepsy with generalized tonic-clonic seizure on awakening and focal epilepsy like temporal lobe epilepsy and cryptogenic focal epilepsy. In 70% of the epilepsy cases, genetic factors are responsible either as single genetic variant in rare epilepsies or multiple genetic variants acting along with different environmental factors as in common epilepsies. Genetic testing and precision treatment have been developed for a few rare epilepsies and is lacking for common epilepsies due to their complex nature of inheritance. Precision medicine for common epilepsies require a panoramic approach that incorporates polygenic background and other non-genetic factors like microbiome, diet, age at disease onset, optimal time for treatment and other lifestyle factors which influence seizure threshold. This review aims to comprehensively present a state-of-art review of all the genes and their genetic variants that are associated with all common epilepsy subtypes. It also encompasses the basis of these genes in the epileptogenesis. Here, we discussed the current status of the common epilepsy genetics and address the clinical application so far on evidence-based markers in prognosis, diagnosis, and treatment management. In addition, we assessed the diagnostic predictability of a few genetic markers used for disease risk prediction in individuals. A combination of deeper endo-phenotyping including pharmaco-response data, electro-clinical imaging, and other clinical measurements along with genetics may be used to diagnose common epilepsies and this marks a step ahead in precision medicine in common epilepsies management.

Developmental decrease in parvalbumin-positive neurons precedes increase in flurothyl-induced seizure susceptibility in the Brd2+/- mouse model of juvenile myoclonic epilepsy

OBJECTIVE

BRD2 is a human gene repeatedly linked to and associated with juvenile myoclonic epilepsy (JME). Here, we define the developmental stage when increased seizure susceptibility first manifests in heterozygous Brd2+/- mice, an animal model of JME. We wanted to determine (1) whether seizure susceptibility correlates with the proven decrease of γ-aminobutyric acidergic (GABAergic) neuron numbers and (2) whether the seizure phenotype can be affected by sex hormones.

METHODS

Heterozygous (Brd2+/-) and wild-type (wt) mice of both sexes were tested for flurothyl-induced seizure susceptibility at postnatal day 15 (P15; wt, n = 13; Brd2+/-, n = 20), at P30 (wt, n = 20; Brd2+/-, n = 20), and in adulthood (5-6 months of age; wt, n = 10; Brd2+/-, n = 12). We measured latency to clonic and tonic-clonic seizure onset (flurothyl threshold). We also compared relative density of parvalbumin-positive (PVA+) and GAD67+ GABA neurons in the striatum and primary motor (M1) neocortex of P15 (n = 6-13 mice per subgroup) and P30 (n = 7-10 mice per subgroup) mice. Additional neonatal Brd2+/- mice were injected with testosterone propionate (females) or formestane (males) and challenged with flurothyl at P30.

RESULTS

P15 Brd2+/- mice showed no difference in seizure susceptibility compared to P15 wt mice. However, even at this early age, Brd2+/- mice showed fewer PVA+ neurons in the striatum and M1 neocortex. Compared to wt, the striatum in Brd2+/- mice showed an increased proportion of immature PVA+ neurons, with smaller cell bodies and limited dendritic arborization. P30 Brd2+/- mice displayed increased susceptibility to flurothyl-induced clonic seizures compared to wt. Both genotype and sex strongly influenced the density of PVA+ neurons in the striatum. Susceptibility to clonic seizures remained increased in adult Brd2+/- mice, and additionally there was increased susceptibility to tonic-clonic seizures. In P30 females, neonatal testosterone reduced the number of flurothyl-induced clonic seizures.

SIGNIFICANCE

A decrease in striatal PVA+ GABAergic neurons developmentally precedes the onset of increased seizure susceptibility and likely contributes to the expression of the syndrome.