Phenotypic analysis of 303 multiplex families with common epilepsies

Cerebral Palsy Phenotypes in Genetic Epilepsies

BACKGROUND

Although there are established connections between genetic epilepsies and neurodevelopmental disorders like intellectual disability, the presence of cerebral palsy (CP) in genetic epilepsies is undercharacterized. We performed a retrospective chart review evaluating the motor phenotype of patients with genetic epilepsies.

METHODS

Patients were ascertained through a research exome sequencing study to identify genetic causes of epilepsy. We analyzed data from the first 100 individuals with molecular diagnoses. We determined motor phenotype by reviewing medical records for muscle tone and motor function data. We characterized patients according to CP subtypes: spastic diplegic, spastic quadriplegic, spastic hemiplegic, dyskinetic, hypotonic-ataxic.

RESULTS

Of 100 individuals with genetic epilepsies, 14% had evidence of possible CP, including 5% characterized as hypotonic-ataxic CP, 5% spastic quadriplegic CP, 3% spastic diplegic CP, and 1% hemiplegic CP. Presence of CP did not correlate with seizure onset age (P = 0.63) or seizure control (P = 0.07). CP occurred in 11% (n = 3 of 27) with focal epilepsy, 9% (n = 5 of 54) with generalized epilepsy, and 32% (n = 6 of 19) with combined focal/generalized epilepsy (P = 0.06).

CONCLUSIONS

In this retrospective analysis of patients with genetic epilepsies, we identified a substantial portion with CP phenotypes, representing an under-recognized comorbidity. These findings underscore the many neurodevelopmental features associated with neurogenetic conditions, regardless of the feature for which they were ascertained for sequencing. Detailed motor phenotyping is needed to determine the prevalence of CP and its subtypes among genetic epilepsies. These motor phenotypes require clinical management and represent important targeted outcomes in trials for patients with genetic epilepsies.

Familial aggregation of seizure outcomes in four familial epilepsy cohorts

OBJECTIVE

To assess the possible effects of genetics on seizure outcome by estimating the familial aggregation of three outcome measures: seizure remission, history of ≥4 tonic-clonic seizures, and seizure control for individuals taking antiseizure medication.

METHODS

We analyzed families containing multiple persons with epilepsy in four previously collected retrospective cohorts. Seizure remission was defined as being 5 and 10 years seizure-free at last observation. Total number of tonic-clonic seizures was dichotomized at <4 and ≥4 seizures. Seizure control in patients taking antiseizure medication was defined as no seizures for 1, 2, and 3 years. We used Bayesian generalized linear mixed-effects model (GLMM) to estimate the intraclass correlation coefficient (ICC) of the family-specific random effect, controlling for epilepsy type, age at epilepsy onset, and age at last data collection as fixed effects. We analyzed each cohort separately and performed meta-analysis using GLMMs.

RESULTS

The combined cohorts included 3644 individuals with epilepsy from 1463 families. A history of ≥4 tonic-clonic seizures showed strong familial aggregation in three separate cohorts and meta-analysis (ICC .28, 95% confidence interval [CI] .21-.35, Bayes factor 8 × 1016). Meta-analyses did not reveal significant familial aggregation of seizure remission (ICC .08, 95% CI .01-.17, Bayes factor 1.46) or seizure control for individuals taking antiseizure medication (ICC .13, 95% CI 0-.35, Bayes factor 0.94), with heterogeneity among cohorts.

SIGNIFICANCE

A history of ≥4 tonic-clonic seizures aggregated strongly in families, suggesting a genetic influence, whereas seizure remission and seizure control for individuals taking antiseizure medications did not aggregate consistently in families. Different seizure outcomes may have different underlying biology and risk factors. These findings should inform the future molecular genetic studies of seizure outcomes.

The role of copy number variants in the genetic architecture of common familial epilepsies

OBJECTIVE

Copy number variants (CNVs) contribute to genetic risk and genetic etiology of both rare and common epilepsies. Whereas many studies have explored the role of CNVs in sporadic or severe cases, fewer have been done in familial generalized and focal epilepsies.

METHODS

We analyzed exome sequence data from 267 multiplex families and 859 first-degree relative pairs with a diagnosis of genetic generalized epilepsies or nonacquired focal epilepsies to predict CNVs. Validation and segregation studies were performed using an orthogonal method when possible.

RESULTS

We identified CNVs likely to contribute to epilepsy risk or etiology in the probands of 43 of 1116 (3.9%) families, including known recurrent CNVs (16p13.11 deletion, 15q13.3 deletion, 15q11.2 deletion, 16p11.2 duplication, 1q21.1 duplication, and 5-Mb duplication of 15q11q13). We also identified CNVs affecting monogenic epilepsy genes, including four families with CNVs disrupting the DEPDC5 gene, and a de novo deletion of HNRNPU in one affected individual from a multiplex family. Several large CNVs (>500 kb) of uncertain clinical significance were identified, including a deletion in 18q, a large duplication encompassing the SCN1A gene, and a 15q13.3 duplication (BP4-BP5).

SIGNIFICANCE

The overall CNV landscape in common familial epilepsies is similar to that of sporadic epilepsies, with large recurrent deletions at 15q11, 15q13, and 16p13 contributing in 2.5%-3% of families. CNVs that interrupt known epilepsy genes and rare, large CNVs were also identified. Multiple etiologies were found in a subset of families, emphasizing the importance of genetic testing for multiple affected family members. Rare CNVs found in a single proband remain difficult to interpret and require larger cohorts to confirm their potential role in disease. Overall, our work indicates that CNVs contribute to the complex genetic architecture of familial generalized and focal epilepsies, supporting the role for clinical testing in affected individuals.

Common risk variants for epilepsy are enriched in families previously targeted for rare monogenic variant discovery

BACKGROUND

The epilepsies are highly heritable conditions that commonly follow complex inheritance. While monogenic causes have been identified in rare familial epilepsies, most familial epilepsies remain unsolved. We aimed to determine (1) whether common genetic variation contributes to familial epilepsy risk, and (2) whether that genetic risk is enriched in familial compared with non-familial (sporadic) epilepsies.

METHODS

Using common variants derived from the largest epilepsy genome-wide association study, we calculated polygenic risk scores (PRS) for patients with familial epilepsy (n = 1,818 from 1,181 families), their unaffected relatives (n = 771), sporadic patients (n = 1,182), and population controls (n = 15,929). We also calculated separate PRS for genetic generalised epilepsy (GGE) and focal epilepsy. Statistical analyses used mixed-effects regression models to account for familial relatedness, sex, and ancestry.

FINDINGS

Patients with familial epilepsies had higher epilepsy PRS compared to population controls (OR 1·20, p_adj = 5×10^-9), sporadic patients (OR 1·11, p_adj = 0.008), and their own unaffected relatives (OR 1·12, p_adj = 0.01). The top 1% of the PRS distribution was enriched 3.8-fold for individuals with familial epilepsy when compared to the lowest decile (p_adj = 5×10^-11). Familial PRS enrichment was consistent across epilepsy type; overall, polygenic risk was greatest for the GGE clinical group. There was no significant PRS difference in familial cases with established rare variant genetic etiologies compared to unsolved familial cases.

INTERPRETATION

The aggregate effects of common genetic variants, measured as polygenic risk scores, play an important role in explaining why some families develop epilepsy, why specific family members are affected while their relatives are not, and why families manifest specific epilepsy types. Polygenic risk contributes to the complex inheritance of the epilepsies, including in individuals with a known genetic etiology.

FUNDING

National Health and Medical Research Council of Australia, National Institutes of Health, American Academy of Neurology, Thomas B and Jeannette E Laws McCabe Fund, Mirowski Family Foundation.

Female preponderance in genetic generalized epilepsies

INTRODUCTION

Epilepsy is more prevalent in men but Genetic Generalized Epilepsies (GGE) seem to be more common in women. A predominant maternal inheritance has been previously described in GGE. Our objective was to determine sex and inheritance patterns in a GGE population compared to mesial temporal lobe epilepsy with hippocampal sclerosis (MTLEHS).

METHODS

We performed a prospective observational study including adult GGE and MTLEHS patients followed up at a tertiary epilepsy center from January 2016 to December 2019. Patients' familial history was obtained by a detailed questionnaire. Clinical and demographic data was retrieved from clinical notes.

RESULTS

A cohort of 641 patients, 403 with GGE and 238 with MTLEHS, was analyzed. GGE was more common in women than MTLEHS (58.8% vs 44.5%, OR=1.63, p = 0.004). Compared to MTLEHS patients, more GGE patients had familial history of epilepsy (45.4% vs 25.2%; p<0.001). The GGE group had a higher percentage of female relatives with epilepsy (55% vs 37%; p = 0.006). The prevalence of maternal inheritance was not different between GGE and MTLEHS groups (62.9% vs 57.7%; p = 0.596). Photosensitivity was more common in females than in males (44.7% vs 34.3%, p = 0.036).

CONCLUSION

There is a female preponderance in GGE when compared to MTLEHS, as both GGE patients and their affected relatives are more frequently women. The prevalence of maternal inheritance was not higher in GGE than in MTLEHS.

Generalized, focal, and combined epilepsies in families: New evidence for distinct genetic factors

OBJECTIVE

To determine the roles of shared and distinct genetic influences on generalized and focal epilepsy operating in individuals who manifest features of both types (combined epilepsies), and in families manifesting both generalized and focal epilepsies in separate individuals (mixed families).

METHODS

We analyzed the deeply phenotyped Epi4K cohort of multiplex families (≥3 affected individuals per family) using methods that quantify the aggregation of phenotypes within families and the relatedness of individuals with different phenotypes within family pedigrees.

RESULTS

The cohort included 281 families containing 1021 individuals with generalized (n = 484), focal (304), combined (51), or unclassified (182) epilepsies. The odds of combined epilepsy was higher in relatives of participants with combined epilepsy than in relatives of those with other epilepsy types (odds ratio [OR] 5.2, 95% confidence interval [CI] 1.7-16.1, P = .004). Individuals with combined epilepsy co-occurred in families more often than expected by chance (P = .03). Within mixed families, individuals with each type of epilepsy were more closely related to relatives with the same type than to relatives with other types (P < .001).

SIGNIFICANCE

These findings suggest that distinct genetic influences underlie the recently recognized entity of combined epilepsies, just as generalized epilepsies and focal epilepsies each have distinct genetic influences. Mixed families may in part reflect chance co-occurrence of these distinct genetic influences. These conclusions have important implications for molecular genetic studies aimed at identifying genetic determinants of the epilepsies.

Semantic Similarity Analysis Reveals Robust Gene-Disease Relationships in Developmental and Epileptic Encephalopathies

More than 100 genetic etiologies have been identified in developmental and epileptic encephalopathies (DEEs), but correlating genetic findings with clinical features at scale has remained a hurdle because of a lack of frameworks for analyzing heterogenous clinical data. Here, we analyzed 31,742 Human Phenotype Ontology (HPO) terms in 846 individuals with existing whole-exome trio data and assessed associated clinical features and phenotypic relatedness by using HPO-based semantic similarity analysis for individuals with de novo variants in the same gene. Gene-specific phenotypic signatures included associations of SCN1A with “complex febrile seizures” (HP: 0011172; p = 2.1 × 10⁻⁵) and “focal clonic seizures” (HP: 0002266; p = 8.9 × 10⁻⁶), STXBP1 with “absent speech” (HP: 0001344; p = 1.3 × 10⁻¹¹), and SLC6A1 with “EEG with generalized slow activity” (HP: 0010845; p = 0.018). Of 41 genes with de novo variants in two or more individuals, 11 genes showed significant phenotypic similarity, including SCN1A (n = 16, p < 0.0001), STXBP1 (n = 14, p = 0.0021), and KCNB1 (n = 6, p = 0.011). Including genetic and phenotypic data of control subjects increased phenotypic similarity for all genetic etiologies, whereas the probability of observing de novo variants decreased, emphasizing the conceptual differences between semantic similarity analysis and approaches based on the expected number of de novo events. We demonstrate that HPO-based phenotype analysis captures unique profiles for distinct genetic etiologies, reflecting the breadth of the phenotypic spectrum in genetic epilepsies. Semantic similarity can be used to generate statistical evidence for disease causation analogous to the traditional approach of primarily defining disease entities through similar clinical features.

Familial mesial temporal lobe epilepsy in Mexico: Inheritance pattern and clinical features

PURPOSE

The objectives of this study were to determine the inheritance pattern by which familial mesial temporal lobe epilepsy (FMTLE) is segregated in Mexican families, and to identify if there was an association between the clinical characteristics and the inheritance pattern.

METHOD

We included a total of 25 families with two or more members affected with MTLE during two years and elaborated a family pedigree for each family. The inheritance pattern was classified as autosomal dominant (AD) or autosomal recessive (AR), considering the affected members. We used statistical analysis association and differences between clinical characteristics and inheritance patterns.

RESULTS

The affected families with the AD pattern were 15.7 fold times more likely to start seizures at 5 years of age or earlier than families with AR pattern, OR = 15.7 (IC 95% = 1.9-128.9). We observed a predominance and greater déjà vu association (64.4% vs 31.3%; p = 0.021), OR = 3.9 (CI 95% = 1.1-13.5) in patients with AD versus AR pattern. Finally, we identified that patients with AD pattern had a likelihood of presenting emotional alterations 5.6 times higher than AR (OR = 5.6, IC = 1.1-27.5).

CONCLUSION

FMTLE is a heterogeneous syndrome, both phenotypically and genotypically; thus, our findings may be helpful for clinical use to perform an early diagnosis, to provide timely treatment, and to prevent comorbidities associated to this disease. However, in order to identify the possible genetic causes underlying these inheritance patterns, the use of molecular studies is necessary.

Familial aggregation of status epilepticus in generalized and focal epilepsies

OBJECTIVE

To determine whether familial aggregation of status epilepticus (SE) occurs in a large cohort of familial common epilepsies.

METHODS

We used the Epilepsy Phenome/Genome Project dataset, which consisted of 2,197 participants in 1,043 family units with ≥2 members having a common generalized or nonacquired focal epilepsy (NAFE). We identified participants with a history of traditionally defined SE (TSE) (seizures ≥30 minutes) and operationally defined SE (OSE) (seizures ≥10 minutes) by chart review. We assessed familial aggregation of TSE and OSE using χ² analysis and generalized estimating equations (GEE).

RESULTS

One hundred fifty-five (7%) participants in 1,043 families had ≥1 episodes of TSE. Two hundred fifty (11%) had ≥1 episodes of OSE. In a χ² analysis, the number of family units with ≥2 members having TSE (odds ratio [OR] 4.79, 95% confidence interval [CI] 2.56-8.97) or OSE (OR 4.23, 95% CI 2.67-6.70) was greater than expected by chance. In GEE models adjusted for sex, broad epilepsy class (GE or NAFE), age at onset, and duration of epilepsy, TSE in a proband predicted TSE in a first-degree relative (OR 2.79, 95% CI 1.24-6.22), and OSE in a proband predicted OSE in a first-degree relative (OR 2.91, 95% CI 1.65-5.15). The results remained significant in models addressing epilepsy severity by incorporating the number of antiseizure medications used or epilepsy surgery.

CONCLUSIONS

TSE and OSE showed robust familial aggregation in a cohort of familial epilepsy independently of epilepsy severity or class, suggesting that genetic factors contribute to SE independently of the genetic cause of these epilepsies.

CLINICALTRIALSGOV IDENTIFIER

NCT00552045.

Genetic Testing in Children with Epilepsy: Report of a Single-Center Experience

BACKGROUND

Retrospective observational study to determine diagnostic yield and utility of genetic testing in children with epilepsy attending the Epilepsy Clinic at Children's Hospital, London, Ontario, Canada.

METHODS

Children (birth-18 years) with epilepsy, who were seen in a 10-year period (January 1, 2008-March 31, 2018), were selected using defined inclusion criteria and by combining clinic datasets and laboratory records.

RESULTS

In total, 105 children (52.38% male and 47.61% female) with a variety of seizures were included in the analysis. Developmental delay was documented in the majority (83; 79.04%). Overall, a genetic diagnosis was established in 24 (22.85%) children. The diagnostic yield was highest for whole-exome sequencing (WES), at 35.71%. The yield from microarray was 8.33%. Yields of single-gene testing (18.60%) and targeted multigene panel testing (19.23%) were very similar. Several likely pathogenic and pathogenic variants not previously reported were identified and categorized using ACMG criteria. All diagnosed patients underwent a review of anti-seizure medication management and received counseling on natural history of their disease, possible complications, recurrence risks, and possibilities of preimplantation or prenatal genetic diagnosis.

CONCLUSIONS

Our study confirms the multiple benefits of detecting a genetic etiology in children with epilepsy. Similar yields in single versus multigene testing underscore the importance of accurate clinical phenotyping. Patients with epilepsy and their caregivers in Ontario would undoubtedly benefit from repatriation of multigene panels and WES to the province.

Exome sequencing in 57 patients with self-limited focal epilepsies of childhood with typical or atypical presentations suggests novel candidate genes

OBJECTIVE

Self-limited focal epilepsies of childhood (SFEC) are amongst the best defined and most frequent epilepsy syndromes affecting children with usually normal developmental milestones. They include core syndromes such as Rolandic epilepsy or "Benign" epilepsy with Centro-Temporal Spikes and the benign occipital epilepsies, the early onset Panayiotopoulos syndrome and the late-onset Gastaut type. Atypical forms exist for all of them. Atypical Rolandic epilepsies are conceptualized as belonging to a continuum reaching from the "benign" RE to the severe end of the Landau-Kleffner (LKS) and Continuous Spike-Waves during Sleep syndromes (CSWS). GRIN2A has been shown to cause the epilepsy-aphasia continuum that includes some patients with atypical Rolandic epilepsy with frequent speech disorders, LKS and CSWS. In the present study, we searched novel genes causing SFEC with typical or atypical presentations.

METHODS

Exome sequencing was performed in 57 trios. Patients presented with typical or atypical SFEC, negative for GRIN2A pathogenic variant.

RESULTS

We found rare candidate variants in 20 patients. Thirteen had occurred de novo and were mostly associated to atypical Rolandic Epilepsy. Two of them could be considered as disease related: a null variant in GRIN2B and a missense variant in CAMK2A. Others were considered good candidates, including a substitution affecting a splice site in CACNG2 and missense variants in genes encoding enzymes involved in chromatin remodeling.

SIGNIFICANCE

Our results further illustrate the fact that atypical SFEC are more likely to have Mendelian inheritance than typical SFEC.

The Genetics of Epilepsy

Epilepsy encompasses a group of heterogeneous brain diseases that affect more than 50 million people worldwide. Epilepsy may have discernible structural, infectious, metabolic, and immune etiologies; however, in most people with epilepsy, no obvious cause is identifiable. Based initially on family studies and later on advances in gene sequencing technologies and computational approaches, as well as the establishment of large collaborative initiatives, we now know that genetics plays a much greater role in epilepsy than was previously appreciated. Here, we review the progress in the field of epilepsy genetics and highlight molecular discoveries in the most important epilepsy groups, including those that have been long considered to have a nongenetic cause. We discuss where the field of epilepsy genetics is moving as it enters a new era in which the genetic architecture of common epilepsies is starting to be unraveled.

Inherited RORB pathogenic variants: Overlap of photosensitive genetic generalized and occipital lobe epilepsy

Variants in RORB have been reported in eight individuals with epilepsy, with phenotypes ranging from eyelid myoclonia with absence epilepsy to developmental and epileptic encephalopathies. We identified novel RORB variants in 11 affected individuals from four families. One was from whole genome sequencing and three were from RORB screening of three epilepsy cohorts: developmental and epileptic encephalopathies (n = 1021), overlap of generalized and occipital epilepsy (n = 84), and photosensitivity (n = 123). Following interviews and review of medical records, individuals' seizure and epilepsy syndromes were classified. Three novel missense variants and one exon 3 deletion were predicted to be pathogenic by in silico tools, not found in population databases, and located in key evolutionary conserved domains. Median age at seizure onset was 3.5 years (0.5-10 years). Generalized, predominantly absence and myoclonic, and occipital seizures were seen in all families, often within the same individual (6/11). All individuals with epilepsy were photosensitive, and seven of 11 had cognitive abnormalities. Electroencephalograms showed generalized spike and wave and/or polyspike and wave. Here we show a striking RORB phenotype of overlap of photosensitive generalized and occipital epilepsy in both individuals and families. This is the first report of a gene associated with this overlap of epilepsy syndromes.

The "maternal effect" on epilepsy risk: Analysis of familial epilepsies and reassessment of prior evidence

OBJECTIVE

Previous studies have observed that epilepsy risk is higher among offspring of affected women than offspring of affected men. We tested whether this "maternal effect" was present in familial epilepsies, which are enriched for genetic factors that contribute to epilepsy risk.

METHODS

We assessed evidence of a maternal effect in a cohort of families containing ≥3 persons with epilepsy using 3 methods: (1) "downward-looking" analysis, comparing the rate of epilepsy in offspring of affected women versus men; (2) "upward-looking" analysis, comparing the rate of epilepsy among mothers versus fathers of affected individuals; and (3) lineage analysis, comparing the proportion of affected individuals with family history of epilepsy on the maternal versus paternal side.

RESULTS

Downward-looking analysis revealed no difference in epilepsy rates among offspring of affected mothers versus fathers (prevalence ratio = 1.0, 95% confidence interval [CI] = 0.8-1.2). Upward-looking analysis revealed more affected mothers than affected fathers; this effect was similar for affected and unaffected sibships (odds ratio = 0.8, 95% CI = 0.5-1.2) and was explained by a combination of differential fertility and participation rates. Lineage analysis revealed no significant difference in the likelihood of maternal versus paternal family history of epilepsy.

INTERPRETATION

We found no evidence of a maternal effect on epilepsy risk in this familial epilepsy cohort. Confounding sex imbalances can create the appearance of a maternal effect in upward-looking analyses and may have impacted prior studies. We discuss possible explanations for the lack of evidence, in familial epilepsies, of the maternal effect observed in population-based studies. ANN NEUROL 2020;87:132-138.

Genetic mechanisms of neurodevelopmental disorders

Neurodevelopmental disorders encompass a broad range of conditions, which include autism, epilepsy, and intellectual disability. These disorders are relatively common and have associated clinical and genetic heterogeneity. Technology has driven much of our understanding of these diseases and their genetic underlying mechanisms, particularly highlighted by the study of large cohorts with comparative genomic hybridization and the more recent implementation of next-generation sequencing (NGS). The mapping of copy number variants throughout the genome has highlighted the recurrent, highly penetrant, de novo variation in syndromic forms of neurodevelopmental disease. NGS of affected individuals and their parents led to a dramatic shift in our understanding as these studies showed that a significant proportion of affected individuals carry rare, de novo variants within single genes that explain their disease presentation. Deep sequencing studies further implicate mosaicism as another mechanism of disease. However, it has also become clear that while rare variants explain a significant proportion of sporadic neurodevelopmental disease, rare variation still does not fully account for the familial clustering and high heritability observed. Common variants, including those within these known disease genes, are also shown to contribute significantly to overall risk. There is also increasing awareness of the important contribution of epigenetic factors and gene-environment interactions.

Quantitative analysis of phenotypic elements augments traditional electroclinical classification of common familial epilepsies

OBJECTIVE

Classification of epilepsy into types and subtypes is important for both clinical care and research into underlying disease mechanisms. A quantitative, data-driven approach may augment traditional electroclinical classification and shed new light on existing classification frameworks.

METHODS

We used latent class analysis, a statistical method that assigns subjects into groups called latent classes based on phenotypic elements, to classify individuals with common familial epilepsies from the Epi4K Multiplex Families study. Phenotypic elements included seizure types, seizure symptoms, and other elements of the medical history. We compared class assignments to traditional electroclinical classifications and assessed familial aggregation of latent classes.

RESULTS

A total of 1120 subjects with epilepsy were assigned to five latent classes. Classes 1 and 2 contained subjects with generalized epilepsy, largely reflecting the distinction between absence epilepsies and younger onset (class 1) versus myoclonic epilepsies and older onset (class 2). Classes 3 and 4 contained subjects with focal epilepsies, and in contrast to classes 1 and 2, these did not adhere as closely to clinically defined focal epilepsy subtypes. Class 5 contained nearly all subjects with febrile seizures plus or unknown epilepsy type, as well as a few subjects with generalized epilepsy and a few with focal epilepsy. Family concordance of latent classes was similar to or greater than concordance of clinically defined epilepsy types.

SIGNIFICANCE

Quantitative classification of epilepsy has the potential to augment traditional electroclinical classification by (1) combining some syndromes into a single class, (2) splitting some syndromes into different classes, (3) helping to classify subjects who could not be classified clinically, and (4) defining the boundaries of clinically defined classifications. This approach can guide future research, including molecular genetic studies, by identifying homogeneous sets of individuals that may share underlying disease mechanisms.

EXOME REPORT: Novel mutation in ATP6V1B2 segregating with autosomal dominant epilepsy, intellectual disability and mild gingival and nail abnormalities

Mutations in ATP6V1B2, which encodes the B2 subunit of the vacuolar H + ATPase have previously been associated with Zimmermann-Laband syndrome 2 (ZLS2) and deafness-onychodystrophy (DDOD) syndrome. Recently epilepsy has also been described as a potentially associated phenotype. Here we further uncover the role of ATP61VB2 in epilepsy and report autosomal dominant inheritance of a novel missense variant in ATP6V1B2 in a large Polish family with relatively mild gingival and nail problems, no phalangeal hypoplasia and with generalized epilepsy. In light of our findings and review of the literature, we propose that the ATP6V1B2 gene should be considered in families with autosomal dominant epilepsy both with or without intellectual disability, and that presence of subtle gingival and nail problems may be another characteristic calling card of affected individuals with ATP6V1B2 mutations.

Sleepwalking and Sleep Paralysis: Prevalence in Colombian Families With Genetic Generalized Epilepsy

BACKGROUND

Sleep deprivation commonly increases seizure frequency in patients with genetic generalized epilepsy, though it is unknown whether there is an increased prevalence of sleepwalking or sleep paralysis in genetic generalized epilepsy patients. Establishing this could provide insights into the bio-mechanisms or genetic architecture of both disorders. The aim of this study was to determine the prevalence of sleepwalking and sleep paralysis in a cohort of patients with genetic generalized epilepsy and their relatives in extended families.

METHODS

A structured interview based on International League Against Epilepsy (ILAE) and International Classification of Sleep Disorders (ICSD-3) criteria was applied to 67 index cases and their relatives to determine genetic generalized epilepsy subtypes and assess the occurrence of sleepwalking or sleep paralysis. Bivariate analysis was performed using chi-square and Fisher exact tests.

RESULTS

The prevalence of sleepwalking and sleep paralysis was 15.3% (95% confidence interval 12.1-18.9) and 11.7% (95% confidence interval 8.7-15.3), respectively. Unusually, no sleepwalkers were found among individuals displaying epilepsy with generalized tonic-clonic seizures. Approximately a quarter of the patients had either parasomnia or genetic generalized epilepsy. Over half the genetic generalized epilepsy families had at least 1 individual with sleepwalking, and more than 40% of the families had one individual with sleep paralysis.

CONCLUSION

The prevalence of sleepwalking or sleep paralysis is reported for individuals with genetic generalized epilepsy and their relatives. The co-existence of either parasomnia in the genetic generalized epilepsy patients and the co-aggregation within their families let suggest that shared heritability and pathophysiological mechanisms exist between these disorders. We hypothesize that sleepwalking/sleep paralysis and genetic generalized epilepsy could be variable expression of genes in shared pathways.

Epilepsy in families: Age at onset is a familial trait, independent of syndrome

OBJECTIVE

We tested 2 hypotheses regarding age at onset within familial epilepsies: (1) family members with epilepsy tend to have similar ages at onset, independent of epilepsy syndrome; and (2) age at onset is younger in successive generations after controlling for sampling bias.

METHODS

We analyzed clinical data collected by the Epi4K Consortium (303 multiplex families, 1,120 individuals). To test hypothesis 1, we used both linear mixed models commonly used for heritability analysis and Cox regression models with frailty terms to assess clustering of onset within families after controlling for other predictors. To test hypothesis 2, we used mixed effects models, pairwise analyses, and survival analysis to address sampling-related bias that may mimic anticipation.

RESULTS

Regarding hypothesis 1, age at seizure onset was significantly heritable (intraclass correlation coefficient = 0.17, p < 0.001) after adjusting for epilepsy type, sex, site, history of febrile seizure, and age at last observation. This finding remained significant after adjusting for epilepsy syndromes, and was robust across statistical methods in all families and in generalized families. Regarding hypothesis 2, the mean age at onset decreased in successive generations (p < 0.001). After adjusting for age at last observation, this effect was not significant in mixed effects models (p = 0.14), but remained significant in pairwise (p = 0.0003) and survival analyses (p = 0.02).

INTERPRETATION

Age at seizure onset is an independent familial trait, and may have genetic determinants distinct from the determinants of particular epilepsy syndromes. Younger onsets in successive generations can be explained in part by sampling bias, but the presence of genetic anticipation cannot be excluded. ANN NEUROL 2019.

Epilepsy genetics: Current knowledge, applications, and future directions

The rapid pace of disease gene discovery has resulted in tremendous advances in the field of epilepsy genetics. Clinical testing with comprehensive gene panels, exomes, and genomes are now available and have led to higher diagnostic rates and insights into the underlying disease processes. As such, the contribution to the care of patients by medical geneticists, neurogeneticists and genetic counselors are significant; the dysmorphic examination, the necessary pre- and post-test counseling, the selection of the appropriate next-generation sequencing-based test(s), and the interpretation of sequencing results require a care provider to have a comprehensive working knowledge of the strengths and limitations of the available testing technologies. As the underlying mechanisms of the encephalopathies and epilepsies are better understood, there may be opportunities for the development of novel therapies based on an individual's own specific genotype. Drug screening with in vitro and in vivo models of epilepsy can potentially facilitate new treatment strategies. The future of epilepsy genetics will also probably include other-omic approaches such as transcriptomes, metabolomes, and the expanded use of whole genome sequencing to further improve our understanding of epilepsy and provide better care for those with the disease.

Clinical and genetic study of Tunisian families with genetic generalized epilepsy: contribution of CACNA1H and MAST4 genes

Genetic generalized epilepsies (GGE) (childhood absence epilepsy (CAE), juvenile myoclonic epilepsy (JME) and epilepsy with generalized tonic-clonic seizures (GTCS)) are mainly determined by genetic factors. Since few mutations were identified in rare families with autosomal dominant GGE, a polygenic inheritance was suspected in most patients. Recent studies on large American or European cohorts of sporadic cases showed that susceptibility genes were numerous although their variants were rare, making their identification difficult. Here, we reported clinical and genetic characteristics of 30 Tunisian GGE families, including 71 GGE patients. The phenotype was close to that in sporadic cases. Nineteen pedigrees had a homogeneous type of GGE (JME-CAE-CGTS), and 11 combined these epileptic syndromes. Rare non-synonymous variants were selected in probands using a targeted panel of 30 candidate genes and their segregation was determined in families. Molecular studies incriminated different genes, mainly CACNA1H and MAST4. The segregation of at least two variants in different genes in some pedigrees was compatible with the hypothesis of an oligogenic inheritance, which was in accordance with the relatively low frequency of consanguineous probands. Since at least 2 susceptibility genes were likely shared by different populations, genetic factors involved in the majority of Tunisian GGE families remain to be discovered. Their identification should be easier in families with a homogeneous type of GGE, in which an intra-familial genetic homogeneity could be suspected.

Familial temporal lobe epilepsy in the 19th century

PURPOSE

To draw attention to a publication showing that familial temporal lobe epilepsy had been described in 1895, considerably earlier than 1994, usually thought to be the date of the original account of the disorder METHODS: Examination of the contents of Sir James Crichton-Browne's Cavendish lecture on 'Dreamy mental states' that was published in the Lancet in mid-1895 RESULTS: At a time when the clinical phenomena that later became associated with the idea of temporal lobe epilepsy were beginning to become known, Creighton-Browne described the presence of this disorder in members of four consecutive generations of a British family throughout the course of the 19th Century CONCLUSIONS: There is evidence that the genetic abnormality responsible for familial temporal epilepsy had probably appeared considerably earlier than hitherto thought.