Comparative characterization of PCDH19 missense and truncating variants in PCDH19-related epilepsy.

Missense and truncating variants in protocadherin 19 (PCDH19) cause PCDH19-related epilepsy. In this study, we aimed to investigate variations in distributional characteristics and the clinical implications of variant type in PCDH19-related epilepsy. We comprehensively collected PCDH19 missense and truncating variants from the literature and by sequencing six exons and intron-exon boundaries of PCDH19 in our cohort. We investigated the distribution of each type of variant using the cumulative distribution function and tested for associations between variant types and phenotypes. The distribution of missense variants in patients was clearly different from that of healthy individuals and was uniform throughout the extracellular cadherin (EC) domain, which consisted of six highly conserved domains. Truncating variants showed two types of distributions: (1) located from EC domain 1 to EC domain 4, and (2) located from EC domain 5 to the cytoplasmic domain. Furthermore, we also found that later onset seizures and milder intellectual disability occurred in patients with truncating variants located from EC domain 5 to the cytoplasmic domain compared with those of patients with other variants. Our findings provide the first evidence of two types of truncating variants in the PCDH19 gene with regard to distribution and the resulting clinical phenotype.

Application of induced pluripotent stem cells in epilepsy.

Epilepsy is among the most common neurological disorders, affecting approximately 50 million people worldwide. Importantly, epilepsy is genetically and etiologically heterogenous, but several epilepsy types exhibit similar clinical presentations. Epilepsy-associated genes are being identified. However, the molecular pathomechanisms remain largely unknown. Approximately one-third of epilepsy is refractory to multiple conventional anti-epileptic drugs (AEDs). Induced pluripotent stem cells (iPSCs) provide an excellent tool to study the pathomechanisms underlying epilepsy and to develop novel treatments. Indeed, disease-specific iPSCs have been established for several genetic epilepsies. In particular, the molecular mechanisms underlying certain developmental and epileptic encephalopathies, such as Dravet syndrome, have been revealed. Modeling epilepsy with iPSCs enables new drug development based on the elucidated pathomechanisms. This can also be used to evaluate conventional AEDs and drug repurposing. Furthermore, transplanting neuronal cells derived from iPSCs into the brain has great potential to treat refractory epilepsies. Recent advances in iPSC technology have enabled the generation of neuronal organoids, or "mini brains." These organoids demonstrate electrophysiological activities similar to those of the brain and have the potential for extensive epilepsy research opportunities. Thus, the application of iPSCs in epilepsy provides insight into novel treatments based on the molecular pathomechanisms of epilepsy. In this review, we comprehensively discuss the studies conducted on iPSCs established for genetic epilepsy or epilepsies without major structural dysmorphic features.

Copy number variation analysis in 83 children with early-onset developmental and epileptic encephalopathy after targeted resequencing of a 109-epilepsy gene panel.

Early-onset developmental and epileptic encephalopathy (DEE) is a group of devastating disorders that appear during the neonatal and infantile periods. Despite great progress in the discovery of genes leading to early-onset DEE, many cases with unexplained etiology remain. Furthermore, to date, the association of copy number variations (CNVs) with early-onset DEE has seldom been addressed. Here, we investigated the contribution of CNVs to epilepsy in a cohort of Japanese children with a variety of early-onset DEEs. Single nucleotide polymorphism (SNP) array analysis was performed for 83 cases that were previously negative for pathogenic single nucleotide variants (SNVs) in 109 genes known or suspected to cause epileptic seizures. Rare CNVs were detected in a total of 12 cases (14.4%), of which three cases (3.6%) involved clearly pathogenic CNVs and nine cases (10.8%) were CNVs of uncertain significance. The three pathogenic CNVs included two de novo heterozygous deletions involving known epileptic encephalopathy genes, such as GABRG2 and PCDH19, and one maternally inherited duplication encompassing MECP2. Our findings indicate rare CNVs are also relevant for the diagnosis of early-onset DEEs, highlighting the importance of not relying only on the investigation of SNVs/small indels at the risk of missing large deletions and duplications.

Characteristics of KCNQ2 variants causing either benign neonatal epilepsy or developmental and epileptic encephalopathy.

OBJECTIVE: Pathogenic variants of KCNQ2, which encode a potassium channel subunit, cause either benign (familial) neonatal epilepsy-B(F)NE)-or KCNQ2 encephalopathy (KCNQ2 DEE). We examined the characteristics of KCNQ2 variants. METHODS: KCNQ2 pathogenic variants were collected from in-house data and two large disease databases with their clinical phenotypes. Nonpathogenic KCNQ2 variants were collected from the Genome Aggregation Database (gnomAD). Pathogenicity of all variants was reevaluated with clinical information to exclude irrelevant variants. The cumulative distribution plots of B(F)NE, KCNQ2 DEE, and gnomAD KCNQ2 variants were compared. Several algorithms predicting genetic variant pathogenicity were evaluated. RESULTS: A total of 259 individuals or pedigrees with 216 different pathogenic KCNQ2 variants and 2967 individuals with 247 different nonpathogenic variants were deemed eligible for the study. Compared to the distribution of nonpathogenic variants, B(F)NE and KCNQ2 DEE missense variants occurred in five and three specific KCNQ2 regions, respectively. Comparison between B(F)NE and KCNQ2 DEE sets showed that B(F)NE missense variants frequently localized to the intracellular domain between S2 and S3, whereas those of KCNQ2 DEE were more frequent in S6, and its adjacent pore domain, as well as in the intracellular domain between S6 and helix A. The scores of Protein Variation Effect Analyzer (PROVEAN) and Percent Accepted Mutation (PAM) 30 prediction algorithms were associated with phenotypes of the variant loci. SIGNIFICANCE: Missense variants in the intracellular domain between S2 and S3 are likely to cause B(F)NE, whereas those in S6 and its adjacent regions are more likely to cause KCNQ2 DEE. With such regional specificities of variants, PAM30 is a helpful tool to examine the possibility that a novel KCNQ2 variant is a B(F)NE or KCNQ2 DEE variant in genetic analysis.

Somatic mosaic deletions involving SCN1A cause Dravet syndrome.

Somatic mosaicism in single nucleotide variants of SCN1A is known to occur in a subset of parents of children with Dravet syndrome (DS). Here, we report recurrent somatic mosaic microdeletions involving SCN1A in children diagnosed with DS. Through the evaluation of 237 affected individuals with DS who did not show SCN1A or PCHD19 mutations in prior sequencing analyzes, we identified two children with mosaic microdeletions covering the entire SCN1A region. The allele frequency of the mosaic deletions estimated by multiplex ligation-dependent probe amplification and array comparative genomic hybridization was 25-40%, which was comparable to the mosaic ratio in lymphocytes and buccal mucosa cells observed by fluorescence in situ hybridization analysis. The minimal prevalence of SCN1A mosaic deletion is estimated to be 0.9% (95% confidence level: 0.11-3.11%) of DS with negative for SCN1A and PCDH19 mutations. This study reinforces the importance of somatic mosaicism caused by copy number variations in disease-causing genes, and provides an alternative spectrum of SCN1A mutations causative of DS. Somatic deletions in SCN1A should be considered in cases with DS when standard screenings for SCN1A mutations are apparently negative for mutations.

A de novo missense mutation of GABRB2 causes early myoclonic encephalopathy.

BACKGROUND: Early myoclonic encephalopathy (EME), a disease with a devastating prognosis, is characterised by neonatal onset of seizures and massive myoclonus accompanied by a continuous suppression-burst EEG pattern. Three genes are associated with EMEs that have metabolic features. Here, we report a pathogenic mutation of an ion channel as a cause of EME for the first time. METHODS: Sequencing was performed for 214 patients with epileptic seizures using a gene panel with 109 genes that are known or suspected to cause epileptic seizures. Functional assessments were demonstrated by using electrophysiological experiments and immunostaining for mutant γ-aminobutyric acid-A (GABAA) receptor subunits in HEK293T cells. RESULTS: We discovered a de novo heterozygous missense mutation (c.859A>C [p.Thr287Pro]) in the GABRB2-encoded ß2 subunit of the GABAA receptor in an infant with EME. No GABRB2 mutations were found in three other EME cases or in 166 patients with infantile spasms. GABAA receptors bearing the mutant ß2 subunit were poorly trafficked to the cell membrane and prevented γ2 subunits from trafficking to the cell surface. The peak amplitudes of currents from GABAA receptors containing only mutant ß2 subunits were smaller than that of those from receptors containing only wild-type ß2 subunits. The decrease in peak current amplitude (96.4% reduction) associated with the mutant GABAA receptor was greater than expected, based on the degree to which cell surface expression was reduced (66% reduction). CONCLUSION: This mutation has complex functional effects on GABAA receptors, including reduction of cell surface expression and attenuation of channel function, which would significantly perturb GABAergic inhibition in the brain.

Clinical implications of SCN1A missense and truncation variants in a large Japanese cohort with Dravet syndrome.

OBJECTIVE: Two major classes of SCN1A variants are associated with Dravet syndrome (DS): those that result in haploinsufficiency (truncating) and those that result in an amino acid substitution (missense). The aim of this retrospective study was to describe the first large cohort of Japanese patients with SCN1A mutation-positive DS (n = 285), and investigate the relationship between variant (type and position) and clinical expression and response to treatment. METHODS: We sequenced all exons and intron-exon boundaries of SCN1A in our cohort, investigated differences in the distribution of truncating and missense variants, tested for associations between variant type and phenotype, and compared these patterns with those of cohorts with milder epilepsy and healthy individuals. RESULTS: Unlike truncation variants, missense variants are found at higher density in the S4 voltage sensor and pore loops and at lower density in the domain I-II and II-III linkers and the first three segments of domain II. Relative to healthy individuals, there is an increased frequency of truncating (but not missense) variants in the noncoding C-terminus. The rate of cognitive decline is more rapid for patients with truncation variants regardless of age at seizure onset, whereas age at onset is a predictor of the rate of cognitive decline for patients with missense variants. SIGNIFICANCE: We found significant differences in the distribution of truncating and missense variants across the SCN1A sequence among healthy individuals, patients with DS, and those with milder forms of SCN1A-variant positive epilepsy. Testing for associations with phenotype revealed that variant type can be predictive of rate of cognitive decline. Analysis of descriptive medication data suggests that in addition to conventional drug therapy in DS, bromide, clonazepam and topiramate may reduce seizure frequency.

HOMOLOGY FOR QUANDLES WITH PARTIAL GROUP OPERATIONS.

A quandle is a set that has a binary operation satisfying three conditions corresponding to the Reidemeister moves. Homology theories of quandles have been developed in a way similar to group homology, and have been applied to knots and knotted surfaces. In this paper, a homology theory is defined that unifies group and quandle homology theories. A quandle that is a union of groups with the operation restricting to conjugation on each group component is called a multiple conjugation quandle (MCQ, defined rigorously within). In this definition, compatibilities between the group and quandle operations are imposed which are motivated by considerations on colorings of handlebody-links. The homology theory defined here for MCQs takes into consideration both group and quandle operations, as well as their compatibility. The first homology group is characterized, and the notion of extensions by 2-cocycles is provided. Degenerate subcomplexes are defined in relation to simplicial decompositions of prismatic (products of simplices) complexes and group inverses. Cocycle invariants are also defined for handlebody-links.

SCN8A encephalopathy: Research progress and prospects.

On April 21, 2015, the first SCN8A Encephalopathy Research Group convened in Washington, DC, to assess current research into clinical and pathogenic features of the disorder and prepare an agenda for future research collaborations. The group comprised clinical and basic scientists and representatives of patient advocacy groups. SCN8A encephalopathy is a rare disorder caused by de novo missense mutations of the sodium channel gene SCN8A, which encodes the neuronal sodium channel Nav 1.6. Since the initial description in 2012, approximately 140 affected individuals have been reported in publications or by SCN8A family groups. As a result, an understanding of the severe impact of SCN8A mutations is beginning to emerge. Defining a genetic epilepsy syndrome goes beyond identification of molecular etiology. Topics discussed at this meeting included (1) comparison between mutations of SCN8A and the SCN1A mutations in Dravet syndrome, (2) biophysical properties of the Nav 1.6 channel, (3) electrophysiologic effects of patient mutations on channel properties, (4) cell and animal models of SCN8A encephalopathy, (5) drug screening strategies, (6) the phenotypic spectrum of SCN8A encephalopathy, and (7) efforts to develop a bioregistry. A panel discussion of gaps in bioregistry, biobanking, and clinical outcomes data was followed by a planning session for improved integration of clinical and basic science research. Although SCN8A encephalopathy was identified only recently, there has been rapid progress in functional analysis and phenotypic classification. The focus is now shifting from identification of the underlying molecular cause to the development of strategies for drug screening and prioritized patient care.

[Characteristic asymmetric abnormal eye movement and dystonic posture as the first symptoms of alternating hemiplegia of childhood].

A 3-month-old girl exhibited asymmetric abnormal eye movement and unilateral dystonic posture intermittently after the first few days of life. Unilateral ocular deviation or nystagmus were the main signs of abnormal eye movements. She was suspected to have alternating hemiplegia of childhood (AHC) despite the absence of apparent alternating hemiplegic episodes. Gene analysis revealed a de-novo missense mutation (Asp801Asn) of ATP1A3. AHC is a rare neurodevelopmental disorder characterized by recurrent transient attacks of hemiplegia affecting the unilateral or bilateral side of the body; in most cases, these attacks begin in the first 6 months of life. Initial symptoms of AHC are not alternating hemiplegic episodes, but rather asymmetric abnormal eye movement, dystonic posture, or seizures. It is difficult to diagnose AHC early because no specific findings are observed in the diagnostic laboratory or neuroradiological examinations. Early diagnosis is important because flunarizine may have a protective effect on the severe motor deterioration associated with AHC. Asymmetric abnormal eye movement could be an important clinical symptom for the diagnosis of AHC in early infancy.

A female patient with a hot spot mutation of PRRT2 gene suffering from several types of epileptic seizures in infancy.

Benign familial infantile epilepsy (BFIE) is characterized by non-febrile focal seizures, which sometimes evolve to secondarily generalized seizures and are usually resolved in the second year. Proline-rich transmembrane protein 2 (PRRT2) is confirmed as the major cause of BFIE, familial paroxysmal kinesigeneic dystonia (PKD) and infantile convulsions and choreoathetosis (ICCA) syndrome. We examined a female patient with a hot spot mutation of PRRT2 gene. She had recurrent tonic seizures when she was three months old. The seizures were controlled by several kinds of anticonvulsants. Then, she had several times of focal seizures daily at nine months old. However, the seizures were stopped by small amounts of carbamazepine. Later, when she was two years old, she experienced frequent motor seizures characterized by truncal flexion and swaying the body with partially disturbed consciousness. Her father also had the same PRRT2 gene mutation and non-febrile seizures in infancy. The patient had mild to moderate mental retardation, whereas her father was mentally normal. Therefore, the patient revealed a quiet different phenotype from that of her father as a carrier of the same PRRT2 gene mutation. We speculate that the PRRT2 mutation had caused the BFIE-like seizures both in the patient and her father, whereas other unknown genetic factors specific for the patient might be associated with the atypical seizures observed only in her.

A novel SCN1A mutation in a cytoplasmic loop in intractable juvenile myoclonic epilepsy without febrile seizures.

Generalised (genetic) epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome with various phenotypes. The majority of individuals with GEFS+ have generalised seizure types, in addition to febrile seizures (FS) or febrile seizures plus (FS+), defined as either continued FS after 6 years of age or afebrile seizures following FS. A 27-year-old man with no history of FS/FS+ experienced intractable generalised convulsive seizures. The patient's father had a history of similar seizures during puberty and the patient's siblings had only FS. No individual in the family had both generalised seizures and FS/FS+, although GEFS+ might be considered to be present in the family. Analysis of SCN1A, a sodium channel gene, revealed a novel mutation (c.3250A>T [S1084C]) in the cytoplasmic loop 2 of SCN1A in both the patient and his father. Most previously reported SCN1A mutations in GEFS+ patients are located in the conserved homologous domains of SCN1A, whereas mutations in the cytoplasmic loops are very rare. SCN1A gene analysis is not commonly performed in subjects with generalised seizures without FS. SCN1A mutation may be a clinically-useful genetic marker in order to distinguish GEFS+ patients from those with classic idiopathic generalised epilepsy, even if they present an atypical clinical picture.

Case of Desbuquois dysplasia type 1: potentially lethal skeletal dysplasia.

We report a boy with Desbuquois dysplasia type 1. He had the typical skeletal changes: a "Swedish key" appearance of the proximal femora; advanced carpal ossification and other distinctive features of the hand, including an extra-ossification center at the base of the proximal phalanx of the index and middle fingers; dislocation of the metacarpophalangeal joint of the index finger; and bifid distal phalanx of the thumb. In addition, he presented with very severe prenatal growth failure, respiratory distress as a neonate, subsequent failure to thrive and susceptibility to airway infection, and sudden death in early childhood. Molecular analysis identified homozygous 1 bp deletion in the Calcium-Activated Nucleotidase 1 gene (CANT1). To our knowledge, this is the first report of Desbuquois dysplasia type 1 in Japan. Our experience suggests potential lethality in the disorder.

Reconstruction of the boundary between climate science and politics: the IPCC in the Japanese mass media, 1988-2007.

The Intergovernmental Panel on Climate Change (IPCC) plays a significant role in bridging the boundary between climate science and politics. Media coverage is crucial for understanding how climate science is communicated and embedded in society. This study analyzes the discursive construction of the IPCC in three Japanese newspapers from 1988 to 2007 in terms of the science-politics boundary. The results show media discourses engaged in boundary-work which rhetorically separated science and politics, and constructed the iconic image of the IPCC as a pure scientific authority. In the linkages between the global and national arenas of climate change, the media "domesticate" the issue, translating the global nature of climate change into a discourse that suits the national context. We argue that the Japanese media's boundary-work is part of the media domestication that reconstructed the boundary between climate science and politics reflecting the Japanese context.

[Genetic aberrations and epilepsy].

Despite its frequency in central nervous disease, epilepsy's molecular pathogenesis has been unclear. Still, the association of genes causing epilepsy--and particular familial epilepsy--have ben ascertained, as having abnormalities identified in gene encoding ion channels and receptors. Knowledge of sporadic epilepsy, for its part, has been much improved by a next generation sequencer, but epilepsy's molecular mechanisms remain uncertain even now, when some 400 genes have been identified. The identification of genetic abnormalities is, nonetheless, helpful in diagnosis, treatment, and counseling for the disease. Here, we describe epilepsies in which genetic analyses are useful, the contributions made by new technologies, and future prospects in the understanding and treatment of epilepsy.

Impact of general practice/family medicine training on Japanese junior residents:reflective writing analysis using text mining.

BACKGROUND: We previously reported the impact of general practice/family medicine training on postgraduate training in Japan using evaluation criteria standardized nationwide. However, there is a possibility that new insights may be gained by analyzing the reflective reports written by these residents. METHODS: Junior residents who participated in one-month general practice/family medicine training at one of five medical institutions with full-time family medicine specialists between 2019 and 2022 were enrolled in this study. They were assigned to submit a reflective report on their experiences and thoughts every day during the training. We analyzed these reflective writings using text mining and created a co-occurrence network map to see the relationship between the most frequently used words. RESULTS: Ninety junior residents participated in the study. The words that appeared most frequently in the sentences referring to clinical ability included "symptoms," "medical examination," "consultation," "treatment," and "examination." The words of "family" and "(patient) oneself" showed strong association in the co-occurrence network map. CONCLUSION: It was suggested that general practice/family medicine training greatly contributes to the acquisition of clinical abilities and deepens the learning of junior residents not only about patient care but also about family-oriented care.

Newborn screening for Fabry disease in Japan: prevalence and genotypes of Fabry disease in a pilot study.

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a deficiency of α-galactosidase A (GLA) activity. Enzyme replacement therapy (ERT) for FD is available, and newborn mass screening for FD is being implemented. Here, we undertook a pilot study of newborn mass screening for FD in Japan. GLA activity in dried blood spots was measured using a fluorescence assay and confirmed by measurement of GLA activity in white blood cells (WBCs) in infants with abnormally low GLA activity. This was followed up by genetic testing. A total of 21 170 neonates were enrolled in the study. Of these, seven (five boys, two girls) had low GLA activities, which were verified by the WBC GLA activity assay. Thus, the initial fluorescence assay was suitable for newborn mass screening for FD. Pathogenic mutations of the GLA gene, that is, V199M and IVS4+919G>A, were found in two boys and one boy, respectively. Functional mutations, E66Q and c.-10C>T: g.1170C>T, were found in two boys and one girl, respectively. The prevalence of test-positive newborns was 1/3024, while that of those with a pathogenic mutation was 1/7057. The numbers are higher than those previously anticipated. Standardized management for FD found during newborn mass screening, including an ERT regimen, remains to be established.

Impact of general practice / family medicine training on Japanese junior residents:a descriptive study.

BACKGROUND: Despite international recognition of the impact of general practice / family medicine training on postgraduate training outcomes, there have been few reports from Japan. METHODS: Junior residents who participated in community medicine training for one month between 2019 and 2022 were enrolled in the study. The settings were five medical institutions (one hospital and four clinics) that had full-time family doctors. The junior residents were assigned to one of these institutions. The training content mainly consisted of general ambulatory care, home medical care, community-based care, and reflection. The junior residents evaluated themselves at the beginning and end of their training, and the family doctors evaluated the junior residents at the end. The evaluation items were 36 items in 10 areas, based on the objectives outlined in the Guidelines for Residency Training - 2020 Edition, and were rated on a 10-point Likert scale. In the statistical analysis, Wilcoxon signed rank test of two related groups was performed to analyze changes between pre and post self-evaluation, and the effect size r was calculated. RESULTS: Ninety-one junior residents completed the study. Their self-evaluations showed statistically significant increases in all 36 items. The effect size was large in 33 items. The family doctors' evaluation was 8-9 points for all 36 items. CONCLUSION: General practice / family medicine training may greatly contribute to the acquisition of various required clinical abilities in postgraduate training even in Japan.

Relationship Between Sensory Processing and Autism Spectrum Disorder-Like Behaviors in Prader-Willi Syndrome.

The relationship between sensory processing and ASD-like and associated behaviors in patients with Prader-Willi Syndrome (PWS) remains relatively unexplored. Examining this relationship, 51 adults with PWS were administered the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS), Short Sensory Profile (SSP-J), Food-Related Problem Questionnaire (FRPQ), and Aberrant Behavior Checklist (ABC-J). Based on SSP-J z-scores, participants were classified into three severity groups. Analysis of variance was performed to compare the behavioral scores of these three groups. Statistically significant group differences were observed in PARS (p = .006, ηp2 = .194) and ABC-J (p = .006, ηp2 = .193) scores. Our findings suggest that the level of sensory processing may predict ASD-like and aberrant behaviors in adults with PWS, implying the importance of a proper assessment for early intervention.

Mutation in the STXBP1 Gene Associated with Early Onset West Syndrome: A Case Report and Literature Review.

Syntaxin-binding protein1 (STXBP1) is a member of the Sec1/Munc18-1 protein family, which comprises important regulators of the secretory and synaptic vesicle fusion machinery underlying hormonal and neuronal transmission, respectively. STXBP1 pathogenic variants are associated with multiple neurological disorders. Herein, we present the case of a Japanese girl with a mutation in the STXBP1 gene, who was born at 40 weeks without neonatal asphyxia. At 15 days old, she developed epilepsy and generalized seizures. Around 88 days old, she presented with a series of nodding spasms, with the seizure frequency gradually increasing. Interictal EEG indicated hypsarrhythmia and she presented with developmental regression. At 1.5 years old, genetic testing was performed and mutational analysis revealed an STXBP1 gene mutation (c.875G > A: p.Arg292His). Accordingly, she was diagnosed with developmental and epileptic encephalopathy, presenting West syndrome's clinical characteristics caused by the STXBP1 gene mutation. Although drug treatment has reduced the frequency of epileptic seizures, her development has remained regressive. The relationship between the location and type of genetic abnormality and the phenotype remains unclear. Future studies should investigate the genotype−phenotype correlation and the underlying pathophysiology to elucidate the causal relationships among the multiple phenotype-determining factors.