Inactivation of the Kv2.1 channel through electromechanical coupling.

The Kv2.1 voltage-activated potassium (Kv) channel is a prominent delayed-rectifier Kv channel in the mammalian central nervous system, where its mechanisms of activation and inactivation are critical for regulating intrinsic neuronal excitability1,2. Here we present structures of the Kv2.1 channel in a lipid environment using cryo-electron microscopy to provide a framework for exploring its functional mechanisms and how mutations causing epileptic encephalopathies3-7 alter channel activity. By studying a series of disease-causing mutations, we identified one that illuminates a hydrophobic coupling nexus near the internal end of the pore that is critical for inactivation. Both functional and structural studies reveal that inactivation in Kv2.1 results from dynamic alterations in electromechanical coupling to reposition pore-lining S6 helices and close the internal pore. Consideration of these findings along with available structures for other Kv channels, as well as voltage-activated sodium and calcium channels, suggests that related mechanisms of inactivation are conserved in voltage-activated cation channels and likely to be engaged by widely used therapeutics to achieve state-dependent regulation of channel activity.

Distinctive In Vitro Phenotypes in iPSC-Derived Neurons From Patients With Gain- and Loss-of-Function SCN2A Developmental and Epileptic Encephalopathy.

SCN2A encodes NaV1.2, an excitatory neuron voltage-gated sodium channel and a major monogenic cause of neurodevelopmental disorders, including developmental and epileptic encephalopathies (DEE) and autism. Clinical presentation and pharmocosensitivity vary with the nature of SCN2A variant dysfunction and can be divided into gain-of-function (GoF) cases with pre- or peri-natal seizures and loss-of-function (LoF) patients typically having infantile spasms after 6 months of age. We established and assessed patient induced pluripotent stem cell (iPSC) - derived neuronal models for two recurrent SCN2A DEE variants with GoF R1882Q and LoF R853Q associated with early- and late-onset DEE, respectively. Two male patient-derived iPSC isogenic pairs were differentiated using Neurogenin-2 overexpression yielding populations of cortical-like glutamatergic neurons. Functional properties were assessed using patch clamp and multielectrode array recordings and transcriptomic profiles obtained with total mRNA sequencing after 2-4 weeks in culture. At 3 weeks of differentiation, increased neuronal activity at cellular and network levels was observed for R1882Q iPSC-derived neurons. In contrast, R853Q neurons showed only subtle changes in excitability after 4 weeks and an overall reduced network activity after 7 weeks in vitro. Consistent with the reported efficacy in some GoF SCN2A patients, phenytoin (sodium channel blocker) reduced the excitability of neurons to the control levels in R1882Q neuronal cultures. Transcriptomic alterations in neurons were detected for each variant and convergent pathways suggested potential shared mechanisms underlying SCN2A DEE. In summary, patient iPSC-derived neuronal models of SCN2A GoF and LoF pathogenic variants causing DEE show specific functional and transcriptomic in vitro phenotypes.

CDKL5-mediated developmental tuning of neuronal excitability and concomitant regulation of transcriptome.

Cyclin-dependent kinase-like 5 (CDKL5) is a serine-threonine kinase enriched in the forebrain to regulate neuronal development and function. Patients with CDKL5 deficiency disorder (CDD), a severe neurodevelopmental condition caused by mutations of CDKL5 gene, present early-onset epilepsy as the most prominent feature. However, spontaneous seizures have not been reported in mouse models of CDD, raising vital questions on the human-mouse differences and the roles of CDKL5 in early postnatal brains. Here, we firstly measured electroencephalographic (EEG) activities via a wireless telemetry system coupled with video-recording in neonatal mice. We found that mice lacking CDKL5 exhibited spontaneous epileptic EEG discharges, accompanied with increased burst activities and ictal behaviors, specifically at postnatal day 12 (P12). Intriguingly, those epileptic spikes disappeared after P14. We next performed an unbiased transcriptome profiling in the dorsal hippocampus and motor cortex of Cdkl5 null mice at different developmental timepoints, uncovering a set of age-dependent and brain region-specific alterations of gene expression in parallel with the transient display of epileptic activities. Finally, we validated multiple differentially expressed genes, such as glycine receptor alpha 2 and cholecystokinin, at the transcript or protein levels, supporting the relevance of these genes to CDKL5-regulated excitability. Our findings reveal early-onset neuronal hyperexcitability in mouse model of CDD, providing new insights into CDD etiology and potential molecular targets to ameliorate intractable neonatal epilepsy.

CDKL5 kinase controls transcription-coupled responses to DNA damage.

Mutations in the gene encoding the CDKL5 kinase are among the most common genetic causes of childhood epilepsy and can also give rise to the severe neurodevelopmental condition CDD (CDKL5 deficiency disorder). Despite its importance for human health, the phosphorylation targets and cellular roles of CDKL5 are poorly understood, especially in the cell nucleus. Here, we report that CDKL5 is recruited to sites of DNA damage in actively transcribed regions of the nucleus. A quantitative phosphoproteomic screen for nuclear CDKL5 substrates reveals a network of transcriptional regulators including Elongin A (ELOA), phosphorylated on a specific CDKL5 consensus motif. Recruitment of CDKL5 and ELOA to damaged DNA, and subsequent phosphorylation of ELOA, requires both active transcription and the synthesis of poly(ADP-ribose) (PAR), to which CDKL5 can bind. Critically, CDKL5 kinase activity is essential for the transcriptional silencing of genes induced by DNA double-strand breaks. Thus, CDKL5 is a DNA damage-sensing, PAR-controlled transcriptional modulator, a finding with implications for understanding the molecular basis of CDKL5-related diseases.

Novel CDKL5 targets identified in human iPSC-derived neurons.

CDKL5 Deficiency Disorder (CDD) is a debilitating epileptic encephalopathy disorder affecting young children with no effective treatments. CDD is caused by pathogenic variants in Cyclin-Dependent Kinase-Like 5 (CDKL5), a protein kinase that regulates key phosphorylation events in neurons. For therapeutic intervention, it is essential to understand molecular pathways and phosphorylation targets of CDKL5. Using an unbiased phosphoproteomic approach we identified novel targets of CDKL5, including GTF2I, PPP1R35, GATAD2A and ZNF219 in human iPSC-derived neuronal cells. The phosphoserine residue in the target proteins lies in the CDKL5 consensus motif. We validated direct phosphorylation of GTF2I and PPP1R35 by CDKL5 using complementary approaches. GTF2I controls axon guidance, cell cycle and neurodevelopment by regulating expression of neuronal genes. PPP1R35 is critical for centriole elongation and cilia morphology, processes that are impaired in CDD. PPP1R35 interacts with CEP131, a known CDKL5 phospho-target. GATAD2A and ZNF219 belong to the Nucleosome Remodelling Deacetylase (NuRD) complex, which regulates neuronal activity-dependent genes and synaptic connectivity. In-depth knowledge of molecular pathways regulated by CDKL5 will allow a better understanding of druggable disease pathways to fast-track therapeutic development.

Genotype and phenotype correlation of PHACTR1-related neurological disorders.

BACKGROUND: PHACTR1 (phosphatase and actin regulators) plays a key role in cortical migration and synaptic activity by binding and regulating G-actin and PPP1CA. This study aimed to expand the genotype and phenotype of patients with de novo variants in PHACTR1 and analyse the impact of variants on protein-protein interaction. METHODS: We identified seven patients with PHACTR1 variants by trio-based whole-exome sequencing. Additional two subjects were ascertained from two centres through GeneMatcher. The genotype-phenotype correlation was determined, and AlphaFold-Multimer was used to predict protein-protein interactions and interfaces. RESULTS: Eight individuals carried missense variants and one had CNV in the PHACTR1. Infantile epileptic spasms syndrome (IESS) was the unifying phenotype in eight patients with missense variants of PHACTR1. They could present with other types of seizures and often exhibit drug-resistant epilepsy with a poor prognosis. One patient with CNV displayed a developmental encephalopathy phenotype. Using AlphaFold-Multimer, our findings indicate that PHACTR1 and G-actin-binding sequences overlap with PPP1CA at the RPEL3 domain, which suggests possible competition between PPP1CA and G-actin for binding to PHACTR1 through a similar polymerisation interface. In addition, patients carrying missense variants located at the PHACTR1-PPP1CA or PHACTR1-G-actin interfaces consistently exhibit the IESS phenotype. These missense variants are mostly concentrated in the overlapping sequence (RPEL3 domain). CONCLUSIONS: Patients with variants in PHACTR1 can have a phenotype of developmental encephalopathy in addition to IESS. Moreover, our study confirmed that the variants affect the binding of PHACTR1 to G-actin or PPP1CA, resulting in neurological disorders in patients.

ZFHX3 variants cause childhood partial epilepsy and infantile spasms with favourable outcomes.

BACKGROUND: The ZFHX3 gene plays vital roles in embryonic development, cell proliferation, neuronal differentiation and neuronal death. This study aims to explore the relationship between ZFHX3 variants and epilepsy. METHODS: Whole-exome sequencing was performed in a cohort of 378 patients with partial (focal) epilepsy. A Drosophila Zfh2 knockdown model was used to validate the association between ZFHX3 and epilepsy. RESULTS: Compound heterozygous ZFHX3 variants were identified in eight unrelated cases. The burden of ZFHX3 variants was significantly higher in the case cohort, shown by multiple/specific statistical analyses. In Zfh2 knockdown flies, the incidence and duration of seizure-like behaviour were significantly greater than those in the controls. The Zfh2 knockdown flies exhibited more firing in excitatory neurons. All patients presented partial seizures. The five patients with variants in the C-terminus/N-terminus presented mild partial epilepsy. The other three patients included one who experienced frequent non-convulsive status epilepticus and two who had early spasms. These three patients had also neurodevelopmental abnormalities and were diagnosed as developmental epileptic encephalopathy (DEE), but achieved seizure-free after antiepileptic-drug treatment without adrenocorticotropic-hormone/steroids. The analyses of temporal expression (genetic dependent stages) indicated that ZFHX3 orthologous were highly expressed in the embryonic stage and decreased dramatically after birth. CONCLUSION: ZFHX3 is a novel causative gene of childhood partial epilepsy and DEE. The patients of infantile spasms achieved seizure-free after treatment without adrenocorticotropic-hormone/steroids implies a significance of genetic diagnosis in precise treatment. The genetic dependent stage provided an insight into the underlying mechanism of the evolutional course of illness.

Epilepsy-Related CDKL5 Deficiency Slows Synaptic Vesicle Endocytosis in Central Nerve Terminals.

Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a severe early-onset epileptic encephalopathy resulting mainly from de novo mutations in the X-linked CDKL5 gene. To determine whether loss of presynaptic CDKL5 function contributes to CDD, we examined synaptic vesicle (SV) recycling in primary hippocampal neurons generated from Cdkl5 knockout rat males. Using a genetically encoded reporter, we revealed that CDKL5 is selectively required for efficient SV endocytosis. We showed that CDKL5 kinase activity is both necessary and sufficient for optimal SV endocytosis, since kinase-inactive mutations failed to correct endocytosis in Cdkl5 knockout neurons, whereas the isolated CDKL5 kinase domain fully restored SV endocytosis kinetics. Finally, we demonstrated that CDKL5-mediated phosphorylation of amphiphysin 1, a putative presynaptic target, is not required for CDKL5-dependent control of SV endocytosis. Overall, our findings reveal a key presynaptic role for CDKL5 kinase activity and enhance our insight into how its dysfunction may culminate in CDD.SIGNIFICANCE STATEMENT Loss of cyclin-dependent kinase like 5 (CDKL5) function is a leading cause of monogenic childhood epileptic encephalopathy. However, information regarding its biological role is scarce. In this study, we reveal a selective presynaptic role for CDKL5 in synaptic vesicle endocytosis and that its protein kinase activity is both necessary and sufficient for this role. The isolated protein kinase domain is sufficient to correct this loss of function, which may facilitate future gene therapy strategies if presynaptic dysfunction is proven to be central to the disorder. It also reveals that a CDKL5-specific substrate is located at the presynapse, the phosphorylation of which is required for optimal SV endocytosis.

Identification of a Novel Homozygous GLS Gene Variant Associated with Developmental and Epileptic Encephalopathy (DEE) Type 71.

Developmental and epileptic encephalopathy (DEEs) (OMIM#618,328) is characterized by seizures, hypotonia, and brain abnormalities, often arising from mutations in genes crucial for brain function. Among these genes, GLS stands out due to its vital role in the central nervous system (CNS), with homozygous variants potentially causing DEE type 71. Using Whole Exome Sequencing (WES) on a patient exhibiting symptoms of epileptic encephalopathy, we identified a novel homozygous variant, NM_014905.5:c.1849G > T; p.(Asp617Tyr), in the GLS gene. The 5-year-old patient, born to consanguineous parents, presented with developmental delay, encephalopathy, frequent seizures, and hypotonia. Sanger sequencing further validated the GLS gene variant in both the patient and his family. Furthermore, our bioinformatics analysis indicated that this missense variant could lead to alteration of splicing, resulting in the activation of a cryptic donor site and potentially causing loss of protein function. Our finding highlights the pathogenic significance of the GLS gene, particularly in the context of brain disorders, specifically DEE71.

Expanding the clinical and genetic landscape of (developmental) epileptic encephalopathy with spike-and-wave activation in sleep: results from studies of a Turkish cohort.

The terms developmental epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS) and epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) designate a spectrum of conditions that are typified by different combinations of motor, cognitive, language, and behavioral regression linked to robust spike-and-wave activity during sleep. In this study, we aimed at describing the clinical and molecular findings in "(developmental) epileptic encephalopathy with spike-and-wave activation in sleep" (D)EE-SWAS) patients as well as at contributing to the genetic etiologic spectrum of (D)EE-SWAS. Single nucleotide polymorphism (SNP) array and whole-exome sequencing (WES) techniques were used to determine the underlying genetic etiologies. Of the 24 patients included in the study, 8 (33%) were female and 16 (67%) were male. The median age at onset of the first seizure was 4 years and the median age at diagnosis of (D)EE-SWAS was 5 years. Of the 24 cases included in the study, 13 were compatible with the clinical diagnosis of DEE-SWAS and 11 were compatible with the clinical diagnosis of EE-SWAS. Abnormal perinatal history was present in four cases (17%), and two cases (8%) had a family history of epilepsy. Approximately two-thirds (63%) of all patients had abnormalities detected on brain computerized tomography/magnetic resonance (CT/MR) imaging. After SNP array and WES analysis, the genetic etiology was revealed in 7 out of 24 (29%) cases. Three of the variants detected were novel (SLC12A5, DLG4, SLC9A6). This study revealed for the first time that Smith-Magenis syndrome, SCN8A-related DEE type 13 and SLC12A5 gene variation are involved in the genetic etiology of (D)EE-SWAS. (D)EE-SWAS is a genetically diverse disorder with underlying copy number variations and single-gene abnormalities. In the current investigation, rare novel variations in genes known to be related to (D)EE-SWAS and not previously reported genes to be related to (D)EE-SWAS were discovered, adding to the molecular genetic spectrum. Molecular etiology enables the patient and family to receive thorough and accurate genetic counseling as well as a personalized medicine approach.

Early onset epileptic and developmental encephalopathy and MOGS variants: a new diagnosis in the whole exome sequencing (WES) ERA : Report of a new patient and review of the literature.

Mannosyl-oligosaccharide glucosidase - congenital disorder of glycosylation (MOGS-CDG) is determined by biallelic mutations in the mannosyl-oligosaccharide glucosidase (glucosidase I) gene. MOGS-CDG is a rare disorder affecting the processing of N-Glycans (CDG type II) and is characterized by prominent neurological involvement including hypotonia, developmental delay, seizures and movement disorders. To the best of our knowledge, 30 patients with MOGS-CDG have been published so far. We described a child who is compound heterozygous for two novel variants in the MOGS gene. He presented Early Infantile Developmental and Epileptic Encephalopathy (EI-DEE) in the absence of other specific systemic involvement and unrevealing first-line biochemical findings. In addition to the previously described features, the patient presented a Hirschprung disease, never reported before in individuals with MOGS-CDG.

Behavioral impulsivity is associated with pupillary alterations and hyperactivity in CDKL5 mutant mice.

Cyclin-dependent kinase-like 5 (Cdkl5) deficiency disorder (CDD) is a severe neurodevelopmental condition caused by mutations in the X-linked Cdkl5 gene. CDD is characterized by early-onset seizures in the first month of life, intellectual disability, motor and social impairment. No effective treatment is currently available and medical management is only symptomatic and supportive. Recently, mouse models of Cdkl5 disorder have demonstrated that mice lacking Cdkl5 exhibit autism-like phenotypes, hyperactivity and dysregulations of the arousal system, suggesting the possibility to use these features as translational biomarkers. In this study, we tested Cdkl5 male and female mutant mice in an appetitive operant conditioning chamber to assess cognitive and motor abilities, and performed pupillometry to assess the integrity of the arousal system. Then, we evaluated the performance of artificial intelligence models to classify the genotype of the animals from the behavioral and physiological phenotype. The behavioral results show that CDD mice display impulsivity, together with low levels of cognitive flexibility and perseverative behaviors. We assessed arousal levels by simultaneously recording pupil size and locomotor activity. Pupillometry reveals in CDD mice a smaller pupil size and an impaired response to unexpected stimuli associated with hyperlocomotion, demonstrating a global defect in arousal modulation. Finally, machine learning reveals that both behavioral and pupillometry parameters can be considered good predictors of CDD. Since early diagnosis is essential to evaluate treatment outcomes and pupillary measures can be performed easily, we proposed the monitoring of pupil size as a promising biomarker for CDD.

Biallelic hypomorphic variants in CAD cause uridine-responsive macrocytic anaemia with elevated haemoglobin-A2.

Biallelic pathogenic variants in CAD, that encode the multienzymatic protein required for de-novo pyrimidine biosynthesis, cause early infantile epileptic encephalopathy-50. This rare disease, characterized by developmental delay, intractable seizures and anaemia, is amenable to treatment with uridine. We present a patient with macrocytic anaemia, elevated haemoglobin-A2 levels, anisocytosis, poikilocytosis and target cells in the blood smear, and mild developmental delay. A next-generation sequencing panel revealed biallelic variants in CAD. Functional studies did not support complete abrogation of protein function; however, the patient responded to uridine supplement. We conclude that biallelic hypomorphic CAD variants may cause a primarily haematological phenotype.

Novel copy number variations and phenotypes of infantile epileptic spasms syndrome.

We summarize the copy number variations (CNVs) and phenotype spectrum of infantile epileptic spasms syndrome (IESS) in a Chinese cohort. The CNVs were identified by genomic copy number variation sequencing. The CNVs and clinical data were analyzed. 74 IESS children with CNVs were enrolled. 35 kinds of CNVs were identified. There were 11 deletions and 5 duplications not reported previously in IESS, including 2 CNVs not reported in epilepsy. 87.8% were de novo, 9.5% were inherited from mother and 2.7% from father. Mosaicism occurred in one patient with Xq21.31q25 duplication. 16.2% (12/74) were 1p36 deletion, and 20.3% (15/74) were 15q11-q13 duplication. The age of seizure onset ranged from 17 days to 24 months. Seizure types included epileptic spasms, focal seizures, tonic seizures, and myoclonic seizures. All patients displayed developmental delay. Additional features included craniofacial anomaly, microcephaly, congenital heart defects, and hemangioma. 29.7% of patients were seizure-free for more than 12 months, and 70.3% still had seizures after trying 2 or more anti-seizure medications. In conclusion, CNVs is a prominent etiology of IESS. 1p36 deletion and 15q duplication occurred most frequently. CNV detection should be performed in patients with IESS of unknown causes, especially in children with craniofacial anomalies and microcephaly.

CYFIP2 p.Arg87Cys Causes Neurological Defects and Degradation of CYFIP2.

Here, we report the generation and comprehensive characterization of a knockin mouse model for the hotspot p.Arg87Cys variant of the cytoplasmic FMR1-interacting protein 2 (CYFIP2) gene, which was recently identified in individuals diagnosed with West syndrome, a developmental and epileptic encephalopathy. The Cyfip2+/R87C mice recapitulated many neurological and neurobehavioral phenotypes of the patients, including spasmlike movements, microcephaly, and impaired social communication. Age-progressive cytoarchitectural disorganization and gliosis were also identified in the hippocampus of Cyfip2+/R87C mice. Beyond identifying a decrease in CYFIP2 protein levels in the Cyfip2+/R87C brains, we demonstrated that the p.Arg87Cys variant enhances ubiquitination and proteasomal degradation of CYFIP2. ANN NEUROL 2023;93:155-163.

Refining the phenotypic spectrum of CCDC88A-related PEHO-like syndrome.

Progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy (PEHO) and PEHO-like syndromes are very rare infantile disorders characterized by profound intellectual disability, hypotonia, convulsions, optic, and progressive brain atrophy. Many causative genes for PEHO and PEHO-like syndromes have been identified including CCDC88A. So far, only five patients from two unrelated families with biallelic CCDC88A variants have been reported in the literature. Herein, we describe a new family from Egypt with a lethal epileptic encephalopathy. Our patient was the youngest child born to a highly consanguineous couple and had a family history of five deceased sibs with the same condition. She presented with postnatal microcephaly, poor visual responsiveness, and epilepsy. Her brain MRI showed abnormal cortical gyration with failure of opercularization of the insula, hypogenesis of corpus callosum, colpocephaly, reduced white matter, hypoplastic vermis, and brain stem. Whole exome sequencing identified a new homozygous frameshift variant in CCDC88A gene (c.1795_1798delACAA, p.Thr599ValfsTer4). Our study presents the third reported family with this extremely rare disorder. We also reviewed all described cases to better refine the phenotypic spectrum associated with biallelic loss of function variants in the CCDC88A gene.

Identification of a novel splice-site WWOX variant with paternal uniparental isodisomy in a patient with infantile epileptic encephalopathy.

WOREE syndrome is an early infantile epileptic encephalopathy characterized by drug-resistant seizures and severe psychomotor developmental delays. We report a case of a WWOX splice-site mutation with uniparental isodisomy. A 1-year and 7-month-old girl presented with nystagmus and epileptic seizures from early infancy, with no fixation or pursuit of vision. Physical examination revealed small deformities, such as swelling of both cheeks, folded fingers, rocking feet, and scoliosis. Brain imaging revealed slight hypoplasia of the cerebrum. Electroencephalogram showed focal paroxysmal discharges during the interictal phase of seizures. Vitamin B6 and zonisamide were administered for early infantile epileptic encephalopathy; however, the seizures were not relieved. Despite altering the type and dosage of antiepileptic drugs and ACTH therapy, the seizures were intractable. Whole-exome analysis revealed the homozygosity of WWOX(NM_016373.4):c.516+1G>A. The WWOX mRNA sequencing using peripheral blood RNA confirmed that exon 5 was homozygously deleted. Based on these results, the patient was diagnosed with WOREE syndrome at 5 months. The WWOX variant found in this study is novel and has never been reported before. WOREE syndrome being extremely rare, further case series and analyses of its pathophysiology are warranted.

Communication of individuals with CDKL5 deficiency disorder as observed by caregivers: A descriptive qualitative study.

CDKL5 deficiency disorder (CDD) is a genetically caused developmental epileptic encephalopathy that causes severe communication impairments. Communication of individuals with CDD is not well understood in the literature and currently available measures are not well validated in this population. Accurate and sensitive measurement of the communication of individuals with CDD is important for understanding this condition, clinical practice, and upcoming interventional trials. The aim of this descriptive qualitative study was to understand how individuals with CDD communicate, as observed by caregivers. Participants were identified through the International CDKL5 Disorder Database and invited to take part if their child had a pathogenic variant of the CDKL5 gene and they had previously completed the Communication and Symbolic Behavior Checklist (CSBS-DP ITC). The sample comprised caregivers of 23 individuals with CDD, whose ages ranged from 2 to 30 years (median 13 years), 15 were female, and most did not use words. Semistructured interviews were conducted via videoconference and analyzed using a conventional content analysis. Three overarching categories were identified: mode, purpose and meaning, and reciprocal exchanges. These categories described the purposes and mechanism of how some individuals with CDD communicate, including underpinning influential factors. Novel categories included expressing a range of emotions, and reciprocal exchanges (two-way interactions that varied in complexity). Caregivers observed many communication modes for multiple purposes. Understanding how individuals with CDD communicate improves understanding of the condition and will guide research to develop accurate measurement for clinical practice and upcoming medication trials.

Common genes and recurrent causative variants in 957 Asian patients with pediatric epilepsy.

OBJECTIVE: We aimed to identify common genes and recurrent causative variants in a large group of Asian patients with different epilepsy syndromes and subgroups. METHODS: Patients with unexplained pediatric-onset epilepsy were identified from the in-house Severance Neurodevelopmental Disorders and Epilepsy Database. All patients underwent either exome sequencing or multigene panels from January 2017 to December 2019, at Severance Children's Hospital in Korea. Clinical data were extracted from the medical records. RESULTS: Of the 957 patients studied, 947 (99.0%) were Korean and 570 were male (59.6%). The median age at testing was 4.91 years (interquartile range, 1.53-9.39). The overall diagnostic yield was 32.4% (310/957). Clinical exome sequencing yielded a diagnostic rate of 36.9% (134/363), whereas the epilepsy panel yielded a diagnostic rate of 29.9% (170/569). Diagnostic yield differed across epilepsy syndromes. It was high in Dravet syndrome (87.2%, 41/47) and early infantile developmental epileptic encephalopathy (60.7%, 17/28), but low in West syndrome (21.8%, 34/156) and myoclonic-atonic epilepsy (4.8%, 1/21). The most frequently implicated genes were SCN1A (n = 49), STXBP1 (n = 15), SCN2A (n = 14), KCNQ2 (n = 13), CDKL5 (n = 11), CHD2 (n = 9), SLC2A1 (n = 9), PCDH19 (n = 8), MECP2 (n = 6), SCN8A (n = 6), and PRRT2 (n = 5). The recurrent genetic abnormalities included 15q11.2 deletion/duplication (n = 9), Xq28 duplication (n = 5), PRRT2 deletion (n = 4), MECP2 duplication (n = 3), SCN1A, c.2556+3A>T (n = 3), and 2q24.3 deletion (n = 3). SIGNIFICANCE: Here we present the results of a large-scale study conducted in East Asia, where we identified several common genes and recurrent variants that varied depending on specific epilepsy syndromes. The overall genetic landscape of the Asian population aligns with findings from other populations of varying ethnicities.

Early life seizures and epileptic spasms in STXBP1-related disorders.

OBJECTIVE: Individuals with disease-causing variants in STXBP1 frequently have epilepsy onset in the first year of life with a variety of seizure types, including epileptic spasms. However, the impact of early onset seizures and antiseizure medication (ASM) on the risk of developing epileptic spasms and impact on their trajectory are poorly understood, limiting informed and anticipatory treatment, as well as trial design. METHODS: We retrospectively reconstructed seizure and medication histories in weekly intervals for individuals with STXBP1 developmental and epileptic encephalopathy (DEE) with epilepsy onset in the first year of life and quantitatively analyzed longitudinal seizure histories and medication response. RESULTS: We included 61 individuals with early onset seizures, 29 of whom had epileptic spasms. Individuals with neonatal seizures were likely to have continued seizures after the neonatal period (25/26). The risk of developing epileptic spasms was not increased in individuals with neonatal seizures or early infantile seizures (21/41 vs. 8/16, odds ratio [OR] = 1, 95% confidence interval [CI] = .3-3.9, p = 1). We did not find any ASM associated with the development of epileptic spasms following prior seizures. Individuals with prior seizures (n = 16/21, 76%) had a higher risk of developing refractory epileptic spasms (n = 5/8, 63%, OR = 1.9, 95% CI = .2-14.6, p = .6). Individuals with refractory epileptic spasms had a later onset of epileptic spasms (n = 20, median = 20 weeks) compared to individuals with nonrefractory epileptic spasms (n = 8, median = 13 weeks, p = .08). SIGNIFICANCE: We provide a comprehensive assessment of early onset seizures in STXBP1-DEE and show that the risk of epileptic spasms is not increased following a prior history of early life seizures, nor by certain ASMs. Our study provides baseline information for targeted treatment and prognostication in early life seizures in STXBP1-DEE.