Focal seizures with affective symptoms are a major feature ofPCDH19gene-related epilepsy

Dravet-like syndrome with PCDH19 mutations in Taiwan - A multicenter study

OBJECTIVE

Protocadherin-19 (PCDH19) epilepsy is a rare female restricted epilepsy syndrome with early onset seizures and developmental delay caused by a change or mutation of the PCDH19 gene on the X chromosome. SCN1A-negative patients with a Dravet-like phenotype may have a gene mutation in PCDH19. The aim of this case series was to characterize the phenotype of epileptic patients according to PCDH19 mutations, antiseizure medications, brain images and mutation types in Taiwan.

METHODS

We retrospectively reviewed the medical records of patients with PCDH19 epilepsy from July 2017 to December 2021 from multiple centers in Taiwan. We analyzed the patients' clinical data and genetic reports.

RESULTS

Fifteen female patients (age 3-23 years) were enrolled. Seizure onset was at 4 months to 2 years 7 months of age with generalized tonic-clonic or focal seizures. Seizure frequency tended to be in clusters rather than single longer seizures. The patients had varying degrees of intellectual disability, however 3 had no impairment. Two patients had abnormal brain images including mesial temporal sclerosis, subcortical and periventricular white matter lesions. On average, the patients received 4 antiseizure medications (range 3-6), including 9 patients who were seizure free, and 3 who received sodium channel blockers without aggravation. Missense and truncating variants (frameshift and nonsense variants) accounted for 40% and 46.7% of all mutations. The mutations of 13 patients were located on EC1 to EC4, and EC5 to cytoplasmic domain in 2 patients.

SIGNIFICANCE

PCDH19 epilepsy has distinct phenotypes and an unusual X-linked pattern of expression in which females manifest core symptoms. Psychiatric and behavioral problems are frequently part of the clinical picture. Patients are usually treated with a wide array of standard antiseizure medications, with no preferred antiseizure medication class. No strong correlations between phenotype and location of variant mutations were found in our patients.

Graph masked self-distillation learning for prediction of mutation impact on protein-protein interactions

Assessing mutation impact on the binding affinity change (ΔΔG) of protein-protein interactions (PPIs) plays a crucial role in unraveling structural-functional intricacies of proteins and developing innovative protein designs. In this study, we present a deep learning framework, PIANO, for improved prediction of ΔΔG in PPIs. The PIANO framework leverages a graph masked self-distillation scheme for protein structural geometric representation pre-training, which effectively captures the structural context representations surrounding mutation sites, and makes predictions using a multi-branch network consisting of multiple encoders for amino acids, atoms, and protein sequences. Extensive experiments demonstrated its superior prediction performance and the capability of pre-trained encoder in capturing meaningful representations. Compared to previous methods, PIANO can be widely applied on both holo complex structures and apo monomer structures. Moreover, we illustrated the practical applicability of PIANO in highlighting pathogenic mutations and crucial proteins, and distinguishing de novo mutations in disease cases and controls in PPI systems. Overall, PIANO offers a powerful deep learning tool, which may provide valuable insights into the study of drug design, therapeutic intervention, and protein engineering.

Multicenter retrospective study of patients with PCDH19-related epilepsy: The first Hungarian cohort

OBJECTIVE

PCDH19-related epilepsy occurs predominantly in girls and is caused by pathogenic variant of the protocadherin-19 gene. The initial seizures usually develop in association with fever, begin on average at 15 months of age, and often occur in clusters. Autistic symptoms, intellectual disability, and sleep disturbance are often associated.

METHODS

In our retrospective, multicenter study, we reviewed clinical data of nine children with epilepsy genetically confirmed to be associated with PCDH19.

RESULTS

In the Hungarian patient population aged 0-18 years, the prevalence of PCDH19-related epilepsy was found to be lower (1/100000 live births in females) than the reported international data (4-5/100000 live births in females). Four of our nine patients had positive family history of epilepsy (cousins, sister, and mother). We assessed brain anomalies in three patients (in one patient focal cortical dysplasia and left anterior cingulate dysgenesis, and in two children right or left hippocampal sclerosis) and in another three cases incidentally identified benign alterations on brain MRI were found. The first seizure presented as a cluster in seven out of nine children. In seven out of nine cases occurred status epilepticus. Six out of nine children had autistic symptoms and only one child had normal intellectual development. Seven of our patients were seizure free with combined antiseizure medication (ASM). The most effective ASMs were levetiracetam, valproate, and clobazam.

SIGNIFICANCE

The prevalence of PCDH19-related epilepsy is presumably underestimated because of the lack of widely performed molecular genetic evaluations. Molecular genetic testing including PCDH19 pathogenic variants is recommended for female patients with an onset of seizures before the age of 3 years.

Neuronal network activity and connectivity are impaired in a conditional knockout mouse model with PCDH19 mosaic expression

Mutations in PCDH19 gene, which encodes protocadherin-19 (PCDH19), cause Developmental and Epileptic Encephalopathy 9 (DEE9). Heterogeneous loss of PCDH19 expression in neurons is considered a key determinant of the disorder; however, how PCDH19 mosaic expression affects neuronal network activity and circuits is largely unclear. Here, we show that the hippocampus of Pcdh19 mosaic mice is characterized by structural and functional synaptic defects and by the presence of PCDH19-negative hyperexcitable neurons. Furthermore, global reduction of network firing rate and increased neuronal synchronization have been observed in different limbic system areas. Finally, network activity analysis in freely behaving mice revealed a decrease in excitatory/inhibitory ratio and functional hyperconnectivity within the limbic system of Pcdh19 mosaic mice. Altogether, these results indicate that altered PCDH19 expression profoundly affects circuit wiring and functioning, and provide new key to interpret DEE9 pathogenesis.

NGS-Based Identification of Two Novel PCDH19 Mutations in Female Patients with Early-Onset Epilepsy

Developmental and epileptic encephalopathy-9 (DEE9) is characterized by seizure onset in infancy, mild to severe intellectual impairment, and psychiatric features and is caused by a mutation in the PCDH19 gene on chromosome Xq22. The rare, unusual X-linked type of disorder affects heterozygous females and mosaic males; transmitting males are unaffected. In our study, 165 patients with epilepsy were tested by Next Generation Sequencing (NGS)-based panel and exome sequencing using Illumina technology. PCDH19 screening identified three point mutations, one indel, and one 29 bp-long deletion in five unrelated female probands. Two novel mutations, c.1152_1180del (p.Gln385Serfs*6) and c.830_831delinsAA (p.Phe277*), were identified and found to be de novo pathogenic. Moreover, among the three inherited mutations, two originated from asymptomatic mothers and one from an affected father. The PCDH19 c.1682C>T and c.1711G>T mutations were present in the DNA samples of asymptomatic mothers. After targeted parental testing, X chromosome inactivation tests and Sanger sequencing were carried out for mosaicism examination on maternal saliva samples in the two asymptomatic PCDH19 mutation carrier subjects. Tissue mosaicism and X-inactivation tests were negative. Our results support the opportunity for reduced penetrance in DEE9 and contribute to expanding the genotype-phenotype spectrum of PCDH19-related epilepsy.

X-Linked Epilepsies: A Narrative Review

X-linked epilepsies are a heterogeneous group of epileptic conditions, which often overlap with X-linked intellectual disability. To date, various X-linked genes responsible for epilepsy syndromes and/or developmental and epileptic encephalopathies have been recognized. The electro-clinical phenotype is well described for some genes in which epilepsy represents the core symptom, while less phenotypic details have been reported for other recently identified genes. In this review, we comprehensively describe the main features of both X-linked epileptic syndromes thoroughly characterized to date (PCDH19-related DEE, CDKL5-related DEE, MECP2-related disorders), forms of epilepsy related to X-linked neuronal migration disorders (e.g., ARX, DCX, FLNA) and DEEs associated with recently recognized genes (e.g., SLC9A6, SLC35A2, SYN1, ARHGEF9, ATP6AP2, IQSEC2, NEXMIF, PIGA, ALG13, FGF13, GRIA3, SMC1A). It is often difficult to suspect an X-linked mode of transmission in an epilepsy syndrome. Indeed, different models of X-linked inheritance and modifying factors, including epigenetic regulation and X-chromosome inactivation in females, may further complicate genotype-phenotype correlations. The purpose of this work is to provide an extensive and updated narrative review of X-linked epilepsies. This review could support clinicians in the genetic diagnosis and treatment of patients with epilepsy featuring X-linked inheritance.

Abnormal cell sorting and altered early neurogenesis in a human cortical organoid model of Protocadherin-19 clustering epilepsy

Introduction

Protocadherin-19 (PCDH19)-Clustering Epilepsy (PCE) is a developmental and epileptic encephalopathy caused by loss-of-function variants of the PCDH19 gene on the X-chromosome. PCE affects females and mosaic males while male carriers are largely spared. Mosaic expression of the cell adhesion molecule PCDH19 due to random X-chromosome inactivation is thought to impair cell-cell interactions between mutant and wild type PCDH19-expressing cells to produce the disease. Progress has been made in understanding PCE using rodent models or patient induced pluripotent stem cells (iPSCs). However, rodents do not faithfully model key aspects of human brain development, and patient iPSC models are limited by issues with random X-chromosome inactivation.

Methods

To overcome these challenges and model mosaic PCDH19 expression in vitro, we generated isogenic female human embryonic stem cells with either HA-FLAG-tagged PCDH19 (WT) or homozygous PCDH19 knockout (KO) using genome editing. We then mixed GFP-labeled WT and RFP-labeled KO cells and generated human cortical organoids (hCOs).

Results

We found that PCDH19 is highly expressed in early (days 20-35) WT neural rosettes where it co-localizes with N-Cadherin in ventricular zone (VZ)-like regions. Mosaic PCE hCOs displayed abnormal cell sorting in the VZ with KO and WT cells completely segregated. This segregation remained robust when WT:KO cells were mixed at 2:1 or 1:2 ratios. PCE hCOs also exhibited altered expression of PCDH19 (in WT cells) and N-Cadherin, and abnormal deep layer neurogenesis. None of these abnormalities were observed in hCOs generated by mixing only WT or only KO (modeling male carrier) cells.

Discussion

Our results using the mosaic PCE hCO model suggest that PCDH19 plays a critical role in human VZ radial glial organization and early cortical development. This model should offer a key platform for exploring mechanisms underlying PCE-related cortical hyperexcitability and testing of potential precision therapies.

Mapping combinatorial expression of non-clustered protocadherins in the developing brain identifies novel PCDH19-mediated cell adhesion properties

Non-clustered protocadherins (ncPcdhs) are adhesive molecules with spatio-temporally regulated overlapping expression in the developing nervous system. Although their unique role in neurogenesis has been widely studied, their combinatorial role in brain physiology and pathology is poorly understood. Using probabilistic cell typing by in situ sequencing, we demonstrate combinatorial inter- and intra-familial expression of ncPcdhs in the developing mouse cortex and hippocampus, at single-cell resolution. We discovered the combinatorial expression of Protocadherin-19 (Pcdh19), a protein involved in PCDH19-clustering epilepsy, with Pcdh1, Pcdh9 or Cadherin 13 (Cdh13) in excitatory neurons. Using aggregation assays, we demonstrate a code-specific adhesion function of PCDH19; mosaic PCDH19 absence in PCDH19+9 and PCDH19 + CDH13, but not in PCDH19+1 codes, alters cell-cell interaction. Interestingly, we found that PCDH19 as a dominant protein in two heterophilic adhesion codes could promote trans-interaction between them. In addition, we discovered increased CDH13-mediated cell adhesion in the presence of PCDH19, suggesting a potential role of PCDH19 as an adhesion mediator of CDH13. Finally, we demonstrated novel cis-interactions between PCDH19 and PCDH1, PCDH9 and CDH13. These observations suggest that there is a unique combinatorial code with a cell- and region-specific characteristic where a single molecule defines the heterophilic cell-cell adhesion properties of each code.

Morphometric network-based abnormalities correlate with psychiatric comorbidities and gene expression in PCDH19-related developmental and epileptic encephalopathy

Protocadherin-19 (PCDH19) developmental and epileptic encephalopathy causes an early-onset epilepsy syndrome with limbic seizures, typically occurring in clusters and variably associated with intellectual disability and a range of psychiatric disorders including hyperactive, obsessive-compulsive and autistic features. Previous quantitative neuroimaging studies revealed abnormal cortical areas in the limbic formation (parahippocampal and fusiform gyri) and underlying white-matter fibers. In this study, we adopted morphometric, network-based and multivariate statistical methods to examine the cortex and substructure of the hippocampus and amygdala in a cohort of 20 PCDH19-mutated patients and evaluated the relation between structural patterns and clinical variables at individual level. We also correlated morphometric alterations with known patterns of PCDH19 expression levels. We found patients to exhibit high-significant reductions of cortical surface area at a whole-brain level (left/right pvalue = 0.045/0.084), and particularly in the regions of the limbic network (left/right parahippocampal gyri pvalue = 0.230/0.016; left/right entorhinal gyri pvalue = 0.002/0.327), and bilateral atrophy of several subunits of the amygdala and hippocampus, particularly in the CA regions (head of the left CA3 pvalue = 0.002; body of the right CA3 pvalue = 0.004), and differences in the shape of hippocampal structures. More severe psychiatric comorbidities correlated with more significant altered patterns, with the entorhinal gyrus (pvalue = 0.013) and body of hippocampus (pvalue = 0.048) being more severely affected. Morphometric alterations correlated significantly with the known expression patterns of PCDH19 (rvalue = -0.26, pspin = 0.092). PCDH19 encephalopathy represents a model of genetically determined neural network based neuropsychiatric disease in which quantitative MRI-based findings correlate with the severity of clinical manifestations and had have a potential predictive value if analyzed early.

PCDH19-Related Epilepsies

Protocadherin-19 (PCDH19) is considered one of the most relevant genes related to epilepsy. To date, more than 150 mutations have been identified as causative for PCDH19-female epilepsy (also known as early infantile epileptic encephalopathy-9, EIEE9), which is characterized by early onset epilepsy, intellectual disabilities, and behavioral disturbances. More recently, mosaic-males (i.e., exhibiting the variants in less than 25% of their cells) have been described as affected by infant-onset epilepsy associated with intellectual disability, as well as compulsive or aggressive behavior and autistic features. Although little is known about the physiological role of PCDH19 protein and the pathogenic mechanisms that lead to EIEE9, many reports and clinical observation seem to suggest a relevant role of this protein in the development of cellular hyperexcitability. However, a genotype–phenotype correlation is difficult to establish. The main feature of EIEE9 consists in early onset of seizures, which generally occur in clusters lasting 1 to 5 minutes and repeating up to 10 times a day for several days. Seizures tend to present during febrile episodes, similarly to the first phases of Dravet syndrome and PCDH19 variants have been found in ∼25% of females who present with features of Dravet syndrome and testing negative for SCN1A variants. There is no “standardized” treatment for PCDH19-related epilepsy and most of the patients receiving a combination of several drugs. In this review, we focus on the latest researches on these aspects, with regard to protein expression, its known functions, and the mechanisms by which the protein acts. The clinical phenotypes related to PCDH19 mutations are also discussed.

Genetic variants and phenotype analysis in a five-generation Chinese pedigree with PCDH19 female-limited epilepsy

Objective

Albeit the gene of PCDH19-FE was ascertained, the correlation of gene mutation, PCDH19 protein structure, and phenotype heterogeneity remained obscure. This study aimed to report a five-generation pedigree of seven female patients of PCDH19-FE and tried to explore whether two variants were correlated with PCDH19 protein structure and function alteration, and PCDH19-FE phenotype.

Methods

We analyzed the clinical data and genetic variants of a PCDH19-FE pedigree, to explore the phenotype heterogeneity of PCDH19-FE and underlying mechanisms. In addition to the clinical information of family members, next-generation sequencing was adopted to detect the variant sites of probands with validation by sanger sequencing. And the sanger sequencing was conducted in other patients in this pedigree. The biological conservation analysis and population polymorphism analysis of variants were also performed subsequently. The structure alteration of mutated PCDH19 protein was predicted by AlphaFold2.

Results

Based on a five-generation pedigree of PCDH19-FE, missense variants of c.695A>G and c.2760T>A in the PCDH19 gene were found in the heterozygous proband (V:1), which resulted in the change of amino acid 232 from Asn to Ser (p.Asn232Ser) and amino acid 920 from Asp to Glu (p.Asp920Glu) influencing PCDH19 function. The other six females in the pedigree (II:6, II:8, IV:3, IV:4, IV:5, IV:11) exhibited different clinical phenotypes but shared the same variant. Two males with the same variant have no clinical manifestations (III:3, III:10). The biological conservation analysis and population polymorphism analysis demonstrated the highly conservative characteristics of these two variants. AlphaFold2 predicted that the variant, p.Asp920Glu, led to the disappearance of the hydrogen bond between Asp at position 920 and His at position 919. Furthermore, the hydrogen bond between Asp920 and His919 also disappeared when the Asn amino acid mutated to Ser at position 232.

Conclusion

A strong genotype-phenotype heterogeneity was observed among female patients with the same genotype in our PCDH19-FE pedigree. And two missense variants, c.695A > G and c.2760T>A in the PCDH19 gene, have been identified in our pedigree. The c.2760T>A variant was a novel variant site probably related to the PCDH19-FE.

PCDH19-related epilepsy in mosaic males: The phenotypic implication of genotype and variant allele frequency

OBJECTIVE

To analyze the genotypes and phenotypes of mosaic male patients with PCDH19-related epilepsy (PCDH19-RE) and explore the correlation between genotype, variant allele frequency (VAF), and phenotypic severity.

METHODS

Clinical data and peripheral blood samples of 11 male mosaic patients were collected and analyzed in our study. The VAF of the PCDH19 gene from peripheral blood was quantified using amplicon-based deep sequencing. Additional 20 mosaic male patients with PCDH19-RE were collected from the published literature, with 10 patients whose VAFs of the PCDH19 gene were available for analytic purposes.

RESULTS

In our cohort of 11 patients, 10 variants were identified, and four were novel. The VAF of the PCDH19 gene from peripheral blood ranged from 27 to 90%. The median seizure onset age was 6 months (range: 4-9 months). Clinical manifestations included cluster seizures (100%), fever sensitivity (73%), focal seizures (91%), developmental delay/intellectual disability (DD/ID, 82%), and autistic features (45%). Thirty-one mosaic male patients collected from our cohort and the literature developed seizures mostly (87%) within one year of age. Variant types included missense variants (42%), truncating variants (52%), splice variants (3%), and whole PCDH19 deletion (3%). Among 21 patients with a definite VAF from our cohort and the literature, nine had a low VAF ( ≤ 50%) and 12 had a high VAF (> 50%). Seventy-five percent of variants from the high VAF group were missense, whereas 89% of those from the low VAF group were truncations. The median seizure onset age was 6 months in the low VAF group and 9 months in the high VAF group (p = 0.018). Forty-four percent (4/9) of patients from the low VAF group achieved seizure-free for ≥1 year, whereas none of the 12 patients from the high VAF group did (p = 0.021). DD/ID was present in 83% (10/12) of the high VAF group and 56% (5/9) of the low VAF group (p = 0.331).

CONCLUSION

The predominant variant types were truncating and missense variants. Missense variants tended to have higher VAFs. Patients with a high VAF were more likely to have a more severe epileptic phenotype. Our findings shed light on the phenotypic implications of VAF in mosaic males with PCDH19-RE.

The Broad Clinical Spectrum of Epilepsies Associated With Protocadherin 19 Gene Mutation

Protocadherin 19 (PCDH19) gene is one of the most common genes involved in epilepsy syndromes. According to literature data PCDH19 is among the 6 genes most involved in genetic epilepsies. PCDH19 is located on chromosome Xq22.1 and is involved in neuronal connections and signal transduction. The most frequent clinical expression of PCDH19 mutation is epilepsy and mental retardation limited to female (EFMR) characterized by epileptic and non-epileptic symptoms affecting mainly females. However, the phenotypic spectrum of these mutations is considerably variable from genetic epilepsy with febrile seizure plus to epileptic encephalopathies. The peculiar exclusive involvement of females seems to be caused by a cellular interference in heterozygosity, however, affected mosaic-males have been reported. Seizure types range from focal seizure to generalized tonic-clonic, tonic, atonic, absences, and myoclonic jerks. Treatment of PCDH19-related epilepsy is limited by drug resistance and by the absence of specific treatment indications. However, seizures become less severe with adolescence and some patients may even become seizure-free. Non-epileptic symptoms represent the main disabilities of adult patients with PCDH19 mutation. This review aims to analyze the highly variable phenotypic expression of PCDH19 gene mutation associated with epilepsy.

Novel treatments in epilepsy guided by genetic diagnosis

In recent years, precision medicine has emerged as a new paradigm for improved and more individualized patient care. Its key objective is to provide the right treatment, to the right patient at the right time, by basing medical decisions on individual characteristics, including specific genetic biomarkers. In order to realize this objective researchers and physicians must first identify the underlying genetic cause; over the last 10 years, advances in genetics have made this possible for several monogenic epilepsies. Through next generation techniques, a precise genetic aetiology is attainable in 30-50% of genetic epilepsies beginning in the paediatric age. While committed in such search for novel genes carrying disease-causing variants, progress in the study of experimental models of epilepsy has also provided a better understanding of the mechanisms underlying the condition. Such advances are already being translated into improving care, management and treatment of some patients. Identification of a precise genetic aetiology can already direct physicians to prescribe treatments correcting specific metabolic defects, avoid antiseizure medicines that might aggravate functional consequences of the disease-causing variant or select the drugs that counteract the underlying, genetically determined, functional disturbance. Personalized, tailored treatments should not just focus on how to stop seizures but possibly prevent their onset and cure the disorder, often consisting of seizures and its comorbidities including cognitive, motor and behaviour deficiencies. This review discusses the therapeutic implications following a specific genetic diagnosis and the correlation between genetic findings, pathophysiological mechanisms and tailored seizure treatment, emphasizing the impact on current clinical practice.

Protocadherin 19 Clustering Epilepsy and Neurosteroids: Opportunities for Intervention

Steroids yield great influence on neurological development through nuclear hormone receptor (NHR)-mediated gene regulation. We recently reported that cell adhesion molecule protocadherin 19 (encoded by the PCDH19 gene) is involved in the coregulation of steroid receptor activity on gene expression. PCDH19 variants cause early-onset developmental epileptic encephalopathy clustering epilepsy (CE), with altered steroidogenesis and NHR-related gene expression being identified in these individuals. The implication of hormonal pathways in CE pathogenesis has led to the investigation of various steroid-based antiepileptic drugs in the treatment of this disorder, with mixed results so far. Therefore, there are many unmet challenges in assessing the antiseizure targets and efficiency of steroid-based therapeutics for CE. We review and assess the evidence for and against the implication of neurosteroids in the pathogenesis of CE and in view of their possible clinical benefit.

Integrated in silico and experimental assessment of disease relevance of PCDH19 missense variants

PCDH19 is a nonclustered protocadherin molecule involved in axon bundling, synapse function, and transcriptional coregulation. Pathogenic variants in PCDH19 cause infantile-onset epilepsy known as PCDH19-clustering epilepsy or PCDH19-CE. Recent advances in DNA-sequencing technologies have led to a significant increase in the number of reported PCDH19-CE variants, many of uncertain significance. We aimed to determine the best approaches for assessing the disease relevance of missense variants in PCDH19. The application of the American College of Medical Genetics and Association for Molecular Pathology (ACMG-AMP) guidelines was only 50% accurate. Using a training set of 322 known benign or pathogenic missense variants, we identified MutPred2, MutationAssessor, and GPP as the best performing in silico tools. We generated a protein structural model of the extracellular domain and assessed 24 missense variants. We also assessed 24 variants using an in vitro reporter assay. A combination of these tools was 93% accurate in assessing known pathogenic and benign PCDH19 variants. We increased the accuracy of the ACMG-AMP classification of 45 PCDH19 variants from 50% to 94%, using these tools. In summary, we have developed a robust toolbox for the assessment of PCDH19 variant pathogenicity to improve the accuracy of PCDH19-CE variant classification.

Self-limited epilepsy of childhood with affective seizures: A well-defined epileptic syndrome?

OBJECTIVE

Here we present cases of focal epilepsy with affective symptoms analyzing seizure characteristics, EEG pattern, treatment, and outcome.

METHODS

A multicenter, descriptive, retrospective study was conducted evaluating 18 patients with self-limited epilepsy who presented with seizures with affective symptoms seen between April 2000 and April 2018 at eight Argentinian centers.

RESULTS

Eighteen patients had focal seizures with affective symptoms; all of them had affective symptoms characterized by sudden fright or terror and screaming. Seizures started with manifestations of sudden fright or terror manifested by a facial expression of fear; consciousness was mildly impaired in 15/18 patients. Eleven of the patients also had autonomic manifestations, such as pallor, sweating, and abdominal pain. In addition, four of these 11 patients had ictus emeticus and one also presented with unilateral deviation of the eyes and head. Speech arrest, salivation, glottal noises, and chewing or swallowing movements were observed in 2/18 patients at the onset of the affective seizures. Two others also had mild asymmetric dystonic seizures involving both hands and arms. Three patients had tonic deviation of the mouth involving the lips and tongue as well pharyngeal and laryngeal muscles, resulting in anarthria and drooling. Two patients had brief hemifacial focal clonic seizures.

CONCLUSION

Affective manifestations associated or not with motor and/or autonomic manifestations and associated with typical EEG features of the idiopathic focal epilepsies of childhood is a particular presentation of self-limited focal epilepsy in childhood.

Acute encephalopathy in children with tuberous sclerosis complex

Objective

We examined the clinical manifestations of acute encephalopathy (AE) and identify risk factors for AE in children with tuberous sclerosis complex (TSC).

Methods

The clinical data of 11 children with clinically diagnosed TSC associated with AE and 109 children with clinically diagnosed TSC alone aged 4 years or older were collected from 13 hospitals.

Results

Of the 11 children with AE, 5 had histories of febrile seizures (FS), and all had histories of febrile status epilepticus (FSE). AE developed within 24 h after fever onset in all children with seizures lasting 30 min or longer. All children developed coma after seizure cessation. Head magnetic resonance imaging (MRI) revealed widespread abnormalities in the cerebral cortex, subcortical white matter, corpus callosum, basal ganglia, and thalamus. One child died; seven had severe neurological sequelae; and the other three, mild sequelae. Logistic regression analysis revealed that a history of FSE was correlated with the development of AE.

Significance

AE in children with TSC was characterized by sudden onset after fever, followed by coma, widespread brain edema evident on MRI, and poor outcomes. A history of FSE was a risk factor for the development of AE.

Right Place at the Right Time: How Changes in Protocadherins Affect Synaptic Connections Contributing to the Etiology of Neurodevelopmental Disorders

During brain development, neurons need to form the correct connections with one another in order to give rise to a functional neuronal circuitry. Mistakes during this process, leading to the formation of improper neuronal connectivity, can result in a number of brain abnormalities and impairments collectively referred to as neurodevelopmental disorders. Cell adhesion molecules (CAMs), present on the cell surface, take part in the neurodevelopmental process regulating migration and recognition of specific cells to form functional neuronal assemblies. Among CAMs, the members of the protocadherin (PCDH) group stand out because they are involved in cell adhesion, neurite initiation and outgrowth, axon pathfinding and fasciculation, and synapse formation and stabilization. Given the critical role of these macromolecules in the major neurodevelopmental processes, it is not surprising that clinical and basic research in the past two decades has identified several PCDH genes as responsible for a large fraction of neurodevelopmental disorders. In the present article, we review these findings with a focus on the non-clustered PCDH sub-group, discussing the proteins implicated in the main neurodevelopmental disorders.

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.

Two novel PCDH19 mutations in Russian patients with epilepsy with intellectual disability limited to females: a case report

Background

Epilepsy with intellectual disability limited to females (Epileptic encephalopathy, early infantile, 9; EIEE9) is a rare early infantile epileptic encephalopathy characterized by an unusual X-linked inheritance: females with heterozygous mutations are affected, while hemizygous males are not.

Case presentation

We describe the clinical and molecular characteristics of 2 Russian patients with EIEE9 (females, ages 3 years and 7 years). In these patients seizures developed at the age of 3 years. Additionally, for our patients and for cases described in the literature we searched for a possible relationship between the type and localization of the mutation and the EIEE9 clinical phenotype.

Conclusions

We identified two novel PCDH19 mutations in EIEE9 patients: a missense mutation in exon 1 (c.1236C > A, p.Asp412Glu) and a frameshift in exon 3 (c.2386_2387insGTCT, p.Thr796fs). We conclude that the age of seizure onset and the presence of intellectual disability may depend not on the type and localization of PCDH19 mutations, but on the X-inactivation status. The study also highlights the need to screen for EIEE9 among young female epilepsy patients.

Disentangling the paradox of the PCDH19 clustering epilepsy, a disorder of cellular mosaics

PCDH19 Clustering Epilepsy (CE) is an intriguing early-onset seizure, autism and neurocognitive disorder with unique inheritance. The causative gene, PCDH19, is on the X-chromosome and encodes a cell-cell adhesion protein with restricted expression during brain development. Unlike other X-linked disorders, PCDH19-CE manifests in heterozygous females. Strikingly, hemizygous males are not affected. However, males with postzygotic somatic mutation in PCDH19 are affected and clinically similar to the affected females. PCDH19-CE is a disorder of cellular mosaicism. The coexistence of two different, but otherwise 'normal' cells in a PCDH19-CE individual, that is the wild type and the variant PCDH19 cells, has been proposed as the driving force of the disorder. This 'cellular interference' hypothesis could and has now been tested using sophisticated mouse models.

Quantitative MRI-Based Analysis Identifies Developmental Limbic Abnormalities in PCDH19 Encephalopathy

Protocadherin-19 (PCDH19) is a calcium dependent cell-adhesion molecule involved in neuronal circuit formation with prevalent expression in the limbic structures. PCDH19-gene mutations cause a developmental encephalopathy with prominent infantile onset focal seizures, variably associated with intellectual disability and autistic features. Diagnostic neuroimaging is usually unrevealing. We used quantitative MRI to investigate the cortex and white matter in a group of 20 PCDH19-mutated patients. By a statistical comparison between quantitative features in PCDH19 brains and in a group of age and sex matched controls, we found that patients exhibited bilateral reductions of local gyrification index (lGI) in limbic cortical areas, including the parahippocampal and entorhinal cortex and the fusiform and lingual gyri, and altered diffusivity features in the underlying white matter. In patients with an earlier onset of seizures, worse psychiatric manifestations and cognitive impairment, reductions of lGI and diffusivity abnormalities in the limbic areas were more pronounced. Developmental abnormalities involving the limbic structures likely represent a measurable anatomic counterpart of the reduced contribution of the PCDH19 protein to local cortical folding and white matter organization and are functionally reflected in the phenotypic features involving cognitive and communicative skills as well as local epileptogenesis.

A standardized patient-centered characterization of the phenotypic spectrum of PCDH19 girls clustering epilepsy

Protocadherin-19 (PCDH19) pathogenic variants cause an early-onset seizure disorder called girls clustering epilepsy (GCE). GCE is an X-chromosome disorder that affects heterozygous females and mosaic males, however hemizygous ("transmitting") males are spared. We aimed to define the neuropsychiatric profile associated with PCDH19 pathogenic variants and determine if a clinical profile exists for transmitting males. We also examined genotype- and phenotype-phenotype associations. We developed an online PCDH19 survey comprising the following standardized assessments: The Behavior Rating Inventory of Executive Function; the Social Responsiveness Scale, 2nd edition; the Strengths and Difficulties Questionnaire; and the Dimensional Obsessive-Compulsive Scale. Genetic, seizure, and developmental information were also collected. The survey was completed by patients or by caregivers on behalf of patients. Of the 112 individuals represented (15 males), there were 70 unique variants. Thirty-five variants were novel and included a newly identified recurrent variant Ile781Asnfs*3. There were no significant differences in phenotypic outcomes between published and unpublished cases. Seizures occurred in clusters in 94% of individuals, with seizures resolving in 28% at an average age of 17.5 years. Developmental delay prior to seizure onset occurred in 18% of our cohort. Executive dysfunction and autism spectrum disorder (ASD) occurred in approximately 60% of individuals. The ASD profile included features of attention-deficit hyperactivity disorder. In addition, 21% of individuals met criteria for obsessive-compulsive disorder that appeared to be distinct from ASD. There were no phenotypic differences between heterozygous females and mosaic males. We describe a mosaic male and two hemizygous males with atypical clinical profiles. Earlier seizure onset age and increased number of seizures within a cluster were associated with more severe ASD symptoms (p = 0.001), with seizure onset also predictive of executive dysfunction (p = 4.69 × 10^-4) and prosocial behavior (p = 0.040). No clinical profile was observed for transmitting males. This is the first patient-derived standardized assessment of the neuropsychiatric profile of GCE. These phenotypic insights will inform diagnosis, management, and prognostic and genetic counseling.

A novel PCDH19 missense mutation, c.812G>A (p.Gly271Asp), identified using whole-exome sequencing in a Chinese family with epilepsy female restricted mental retardation syndrome

Background

Epilepsy limited to females with mental retardation (EFMR) is a rare type of epilepsy with an X‐linked mode of inheritance, which affect heterozygous females while the males are not affected. Mutations within the protocadherin 19 (PCDH19) gene have been identified as the direct cause of EFMR. The phenotype of EFMR is characterized by seizure onset in infancy with or without cognitive impairment, intellectual disturbances, and autistic features.

Methods

Whole‐exome sequencing (WES) was performed in the proband to identify the underlying genetic mutations. The candidate genes were confirmed by Sanger sequencing following PCR amplification. In silico analyses were conducted to predict the effect of the novel missense mutation on the function of PCDH19 protein.

Results

We identified three female patients in a family with a novel missense mutation in PCDH19, c.812G>A (p. (Gly271Asp)). The patients III‐1 and III‐2 presented with more severe clinical phenotypes and an earlier age of onset (6 and 11 months, respectively), intellectual disability, and movement disorders. By contrast, patient II‐4 has a later age of onset (23 months), and there was no relapse of seizures without antiepileptic treatment after the age of six. In silico analyses showed that p. (Gly271Asp) in the PCDH19 affects a highly conserved residue.

Conclusions

Our results indicated that patients with the same PCDH19 mutation in a family may show intrafamilial phenotypic variability. Givening the mother of the proband was 18 weeks pregnant and intends to have a prenatal diagnosis, the more reasonable and less harmful strategies for prenatal diagnosis could be chosen based on the results of noninvasive prenatal testing and genetic testing.

PCDH19-Related Epilepsy Syndrome: A Comprehensive Clinical Review

PCDH19-related epilepsy is a distinct childhood-onset epilepsy syndrome characterized by brief clusters of febrile and afebrile seizures with onset primarily before the age of three years, cognitive impairment, autistic traits, and behavioral abnormalities. PCDH19 gene is located in Xq22 and produces nonclustered delta protocadherin. This disorder primarily manifests in heterozygote females due to random X chromosome inactivation leading to somatic mosaicism and abnormal cellular interference between cells with and without delta-protocadherin. This article reviews the clinical features based on a comprehensive literature review (MEDLINE using PubMed and OvidSP vendors with appropriate keywords to incorporate recent evidence), personal practice, and experience. Significant progress has been made in the past 10 years, including identification of the gene responsible for the condition, characterization of clinical phenotypes, and development of animal models. More rigorous studies involving quality-of-life measures as well as standardized neuropsychiatric testing are necessary to understand the full spectrum of the disease. The recent discovery of allopregnanolone deficiency in patients with PCDH19-related epilepsy leads to opportunities in precision therapy. A phase 3 clinical study is currently active to evaluate the efficacy, safety, and tolerability of adjunctive ganaxolone (an allopregnanolone analog) therapy.

Genetic and molecular basis of epilepsy-related cognitive dysfunction

Epilepsy is a common neurological disease characterized by recurrent seizures. About 70 million people were affected by epilepsy or epileptic seizures. Epilepsy is a complicated complex or symptomatic syndromes induced by structural, functional, and genetic causes. Meanwhile, several comorbidities are accompanied by epileptic seizures. Cognitive dysfunction is a long-standing complication associated with epileptic seizures, which severely impairs quality of life. Although the definitive pathogenic mechanisms underlying epilepsy-related cognitive dysfunction remain unclear, accumulating evidence indicates that multiple risk factors are probably involved in the development and progression of cognitive dysfunction in patients with epilepsy. These factors include the underlying etiology, recurrent seizures or status epilepticus, structural damage that induced secondary epilepsy, genetic variants, and molecular alterations. In this review, we summarize several theories that may explain the genetic and molecular basis of epilepsy-related cognitive dysfunction.

PCDH19 Pathogenic Variants in Males: Expanding the Phenotypic Spectrum

Protocadherin-19 (PCDH19) pathogenic variants cause an infantile onset epilepsy syndrome called Girls Clustering Epilepsy due to the vast majority of affected individuals being female. This syndromic name was developed to foster early recognition and diagnosis in infancy. It has, however, sparked debate, as, there are rare males with postzygotic somatic, and therefore, mosaic, PCDH19 pathogenic variants with similar clinical features to females. Conversely, "transmitting" males with germline inherited PCDH19 variants are considered asymptomatic. To date, there has been no standardized neuropsychiatric assessment of males with PCDH19 pathogenic variants. Here, we studied 15 males with PCDH19 pathogenic variants (nine mosaic and six transmitting) aged 2 to 70 years. Our families completed a survey including standardized clinical assessments: Social Responsiveness Scale, Strengths and Difficulties Questionnaire, Behavior Rating Inventory of Executive Function, and Dimensional Obsessive-Compulsive Scale. We identified neuropsychiatric abnormalities in two males with germline PCDH19 possibly pathogenic variants. One had a prior history of a severe encephalopathic illness, which may have been unrelated. We also describe a non-penetrant somatic mosaic male with mosaicism confirmed in blood, but not identified in skin fibroblasts. Our data suggest that transmitting hemizygous males are generally unaffected, in contrast to males with postzygotic somatic mosaic variants who show a similar neuropsychiatric profile to females who are naturally mosaic, due to X-chromosome inactivation. The penetrance of PCDH19 pathogenic variants has been estimated to be 80%. Like females, not all mosaic males are affected. From our small sample, we estimate that males with mosaic PCHD19 pathogenic variants have a penetrance of 85%. With these insights into the male phenotypic spectrum of PCDH19 epilepsy, we propose the new term Clustering Epilepsy (CE). Both affected females and males typically present with infantile onset of clusters of seizures.

Levetiracetam efficacy in PCDH19 Girls Clustering Epilepsy

BACKGROUND

PCDH19 Girls clustering epilepsy (GCE) has a phenotypic spectrum that includes developmental and epileptic encephalopathy. PCDH19-GCE presents with clusters of seizures in the first years of life. Although patients typically outgrow their seizures, many are left with intellectual disability. Here we retrospectively assess the effect of levetiracetam in two independent cohorts of females with PCDH19-GCE.

METHODS

Cohort A was identified by searching our epilepsy genetics research database for girls with PCDH19-GCE who had trialled levetiracetam. Cohort B consisted of girls aged 2 years or older, including women, participating in an international online questionnaire. Information regarding seizure frequency and levetiracetam use was obtained by in-person patient interview and review of clinical records for cohort A, and by patient report for cohort B.

RESULTS

Cohort A consisted of 17 females, aged 3-37 years, who had a trial of levetiracetam at an average age of 10.7 years. 13/17 females became seizure free for >12 months; while 10/17 remained seizure free for >24 months. Cohort B comprised 62 females, aged 1.5-41 years. 26/62 became seizure free for >12 months, and 19/62 for >24 months on levetiracetam therapy.

DISCUSSION

Levetiracetam was effective in two cohorts of females with PCDH19-GCE where 42% and 76% of females became seizure free for >12 months, respectively. Levetiracetam is an effective therapy for females with PCDH19-GCE and should be considered early in the management of the highly refractory clusters of seizures that characterise this genetic disease.

The role of PCDH19 in refractory status epilepticus

PCDH19-Girls Clustering Epilepsy (GCE) is an epileptic syndrome with infantile onset, characterized by clustered and fever-induced seizures, often associated with intellectual disability (ID) and autistic features. Seizures clusters could progress into status epilepticus (SE) with different semiology, both convulsive and nonconvulsive SE (NCSE), and often refractory to conventional antiepileptic drugs. We reviewed literature on PCDH19-GCE, in order to define prevalence, semiology, treatments, and outcome of SE. We conducted a comprehensive review of the PCDH19-GCE literature on the public databases PubMed and EMBASE from January 2008 to July 2019. An overall number of 59 full-text articles were selected, retrieved, and assessed for eligibility. We collected 269 cases with PCDH19-GCE, in 85 of them, a history of SE was reported. Prevalence of SE in all selected series of PCDH19-GCE series is 31.5%. Data on SE were fully exhaustive in 21 cases. There was no gender difference in SE occurrence. Median age at first SE occurrence was 12 months (6 months-11 years). Semiology of SE was reported in 17 cases: it was convulsive in 15 and nonconvulsive in 2. Status epilepticus was refractory in 15 out of 21 cases (71.4%). Benzodiazepine was the most commonly used drug for SE. Alternative treatments with steroids and ketogenic diet were reported as well. We found a high prevalence of ID and autism (19 out of 21 patients, 90%). Despite the relatively high frequency of SE in those patients, there are few specific descriptions of the semiology, EEG pattern, and treatment approach. We strongly believe that a multicenter study looking specifically at SE characteristics might improve the knowledge and consequently the overall outcome. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

Novel and de novo mutation of PCDH19 in Girls Clustering Epilepsy

BACKGROUND

PCDH19 has become the second most relevant gene in epilepsy after SCN1A. Seizures often provoked by fever.

METHODS

We screened 152 children with fever-sensitive epilepsy for gene detection. Their clinical information was followed up.

RESULTS

We found eight PCDH19 point mutations (four novel and four reported) and one whole gene deletion in 10 female probands (seven sporadic cases and three family cases) who also had cluster seizures. The common clinical features of 16 patients in 10 families included fever-sensitive and cluster seizures, mainly focal or tonic-clonic seizures, and absence of status epilepticus, normal intelligence, or mild-to-moderate cognitive impairment, the onset age ranges from 5 months to 20 years. Only four patients had multiple or focal transient discharges in interictal EEG. Focal seizures originating in the frontal region were recorded in four patients, two from the parietal region, and one from the occipital region.

CONCLUSION

PCDH19 mutation can be inherited or de novo. The clinical spectrum of PCDH19 mutation includes PCDH19 Girls Clustering Epilepsy with or without mental retardation, psychosis, and asymptomatic male. The onset age of PCDH19 Girls Clustering Epilepsy can range from infancy to adulthood. Sisters in the same family may be sensitive to the same antiepileptic drugs. And our report expands the mutation spectrum of PCDH19 Girls Clustering Epilepsy.

Gene mutations in paediatric epilepsies cause NMDA-pathy, and phasic and tonic GABA-pathy

The aim of this study was to disentangle mechanisms of epileptogenesis in monogenic epilepsies in children. We reviewed paediatric monogenic epilepsies excluding brain malformation or an inborn error of metabolism, but including the gene function whether there is loss-of-function or gain-of-function, age at gene expression when available, and associated epilepsy syndrome. Genes for which at least five patients with similar epilepsy phenotype had been reported were selected. Three mechanisms are shared by most monogenic epilepsies: (1) excess of N-methyl-d-aspartate (NMDA) transmission activation (NMDA-pathies); (2) abnormal gamma-aminobutyric acid (GABA) transmission with reduced inhibition (phasic GABA-pathies); and (3) tonic activation of extrasynaptic GABA_A receptors by extracellular GABA (tonic GABA-pathies). NMDA-pathies comprise early epileptic encephalopathy with suppression-burst, neonatal/infantile benign seizures, West and Lennox-Gastaut syndromes, and encephalopathy with continuous spike waves in slow sleep, thus brief seizures with major interictal spiking. Phasic GABA-pathies comprise mostly generalized epilepsy with febrile seizures plus and Dravet syndrome, thus long-lasting seizures with mild interictal spiking. Tonic GABA-pathies cause epilepsy with myoclonic-atonic seizures and Angelman syndrome, thus major high-amplitude slow-wave activity. This pathophysiological approach to monogenic epilepsies provides diagnostic clues and helps to guide treatment strategy. WHAT THIS PAPER ADDS: In paediatric monogenic epilepsies, electroclinical patterns point to three main mechanisms: NMDA-pathies, and phasic and tonic GABA-pathies. Antiepileptic treatment choice could be guided by each of these mechanisms.

A mutation update for the PCDH19 gene causing early-onset epilepsy in females with an unusual expression pattern

The PCDH19 gene consists of six exons encoding a 1,148 amino acid transmembrane protein, Protocadherin 19, which is involved in brain development. Heterozygous pathogenic variants in this gene are inherited in an unusual X-linked dominant pattern in which heterozygous females are affected, while hemizygous males are typically unaffected, although they pass on the pathogenic variant to each affected daughter. PCDH19-related disorder is known to cause early-onset epilepsy in females characterized by seizure clusters exacerbated by fever and in most cases, onset is within the first year of life. This condition was initially described in 1971 and in 2008 PCDH19 was identified as the underlying genetic etiology. This condition is the result of pathogenic loss-of-function variants that may be de novo or inherited from an affected mother or unaffected father and cellular interference has been hypothesized to be the culprit. Heterozygous females are symptomatic because of the presence of both wild-type and mutant cells that interfere with one another due to the production of different surface proteins, whereas nonmosaic hemizygous males produce a homogenous population of cells. Here, we review novel pathogenic variants in the PCDH19 gene since 2012 to date, and summarize any genotype-phenotype correlations.

A systematic review and meta-analysis of 271 PCDH19-variant individuals identifies psychiatric comorbidities, and association of seizure onset and disease severity

Epilepsy and Mental Retardation Limited to Females (EFMR) is an infantile onset disorder characterized by clusters of seizures. EFMR is due to mutations in the X-chromosome gene PCDH19, and is underpinned by cellular mosaicism due to X-chromosome inactivation in females or somatic mutation in males. This review characterizes the neuropsychiatric profile of this disorder and examines the association of clinical and molecular factors with neuropsychiatric outcomes. Data were extracted from 38 peer-reviewed original articles including 271 individual cases. We found that seizure onset ≤12 months was significantly associated (p = 4.127 × 10^-7) with more severe intellectual disability, compared with onset >12 months. We identified two recurrent variants p.Asn340Ser and p.Tyr366Leufs*10 occurring in 25 (20 unrelated) and 30 (11 unrelated) cases, respectively. PCDH19 mutations were associated with psychiatric comorbidities in approximately 60% of females, 80% of affected mosaic males, and reported in nine hemizygous males. Hyperactive, autistic, and obsessive-compulsive features were most frequently reported. There were no genotype-phenotype associations in the individuals with recurrent variants or the group overall. Age at seizure onset can be used to provide more informative prognostic counseling.

Defining the electroclinical phenotype and outcome of PCDH19-related epilepsy: A multicenter study

OBJECTIVE

PCDH19-related epilepsy is an epileptic syndrome with infantile onset, characterized by clustered and fever-induced seizures, often associated with intellectual disability (ID) and autistic features. The aim of this study was to analyze a large cohort of patients with PCDH19-related epilepsy and better define the epileptic phenotype, genotype-phenotype correlations, and related outcome-predicting factors.

METHODS

We retrospectively collected genetic, clinical, and electroencephalogram (EEG) data of 61 patients with PCDH19-related epilepsy followed at 15 epilepsy centers. All consecutively performed EEGs were analyzed, totaling 551. We considered as outcome measures the development of ID, autistic spectrum disorder (ASD), and seizure persistence. The analyzed variables were the following: gender, age at onset, age at study, genetic variant, fever sensitivity, seizure type, cluster occurrence, status epilepticus, EEG abnormalities, and cognitive and behavioral disorders. Receiver operating characteristic curve analysis was performed to evaluate the age at which seizures might decrease in frequency.

RESULTS

At last follow-up (median = 12 years, range = 1.9-42.1 years), 48 patients (78.7%) had annual seizures/clusters, 13 patients (21.3%) had monthly to weekly seizures, and 12 patients (19.7%) were seizure-free for ≥2 years. Receiver operating characteristic analysis showed a significant decrease of seizure frequency after the age of 10.5 years (sensitivity = 81.0%, specificity = 70.0%). Thirty-six patients (59.0%) had ID and behavioral disturbances. ASD was present in 31 patients. An earlier age at epilepsy onset emerged as the only predictive factor for ID (P = 0.047) and ASD (P = 0.014). Conversely, age at onset was not a predictive factor for seizure outcome (P = 0.124).

SIGNIFICANCE

We found that earlier age at epilepsy onset is related to a significant risk for ID and ASD. Furthermore, long-term follow-up showed that after the age of 10 years, seizures decrease in frequency and cognitive and behavioral disturbances remain the primary clinical problems.

X-linked epileptic syndrome by protocadherin 19 mutation associated with leukoencephalopathy and posterior reversible tractopathy

Epilepsy and mental retardation produced by mutations in gene PCDH19 (protocadherin 19) is an X-linked syndrome restricted to females. It starts with global and speech developmental delay and epilepsy; intellectual disability may continue in adults. At least in 20% of cases, there are no seizures or intellectual retardation. We report the case of a girl with epilepsy, developmental delay, and autistic conversion associated with posterior reversible leukoencephalopathy and tractopathy produced by PCDH19 mutation (c.142G>T/ p.Glu48X).

Chinese cases of early infantile epileptic encephalopathy: a novel mutation in the PCDH19 gene was proved in a mosaic male- case report

Background

The link between the protocadherin-19 (PCDH19) gene and epilepsy suggests that an unusual form of X-linked inheritance affects females but is transmitted through asymptomatic males. Individuals with epilepsy associated with mutations in the PCDH19 gene display generalized or focal seizures with or without fever sensitivity. The clinical manifestation of the condition ranges from mild to severe, resulting in intellectual disability and behavioural disturbance. In the present study, we assessed mutations in the PCDH19 gene and the clinical features of a group of Chinese patients with early infantile epileptic encephalopathy and aimed to provide further insight into the understanding of epilepsy and mental retardation limited to females (EFMR; MIM 300088).

Case Presentation

We described three variations in the PCDH19 gene in Chinese patients with epilepsy who developed generalized seizures occurring in clusters with or without triggering by fever. Candidate genes were screened for mutations that cause epilepsy and related paroxysmal or nervous system diseases in the coding exons and intron–exon boundaries using polymerase chain reaction (PCR) of genomic deoxyribonucleic acid (DNA) followed by sequencing. The variations were sequenced using next-generation sequencing technology and verified with first-generation sequencing. Exome sequencing of a multigene epilepsy panel revealed three mutations in the PCDH19 gene in a mosaic male and two unrelated females. These included a frameshift mutation c.1508_1509insT (p.Thr504HisfsTer19), a missense mutation c.1681C > T (p.Pro561Ser) and a nonsense mutation c.918C > G (p.Tyr306Ter). Of the three mutations in the PCDH19 gene associated with early infantile epileptic encephalopathy, the frameshift variation in a mosaic male is novel and de novo, the missense variation is de novo and is the second ever reported in females, and the nonsense variation was inherited from the paternal line and is the first example discovered in a female.

Conclusions

The results from our current study provide new insight into and perspectives for the molecular genetic link between epilepsy and PCDH19 alterations. Moreover, our new findings of the male mosaic variant broaden the spectrum of PCDH19-related epilepsy and provide a new understanding of this complex genetic disorder.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0621-x) contains supplementary material, which is available to authorized users.

Clinical Application of Epilepsy Genetics in Africa: Is Now the Time?

Over 80% of people with epilepsy live in low- to middle-income countries where epilepsy is often undiagnosed and untreated due to limited resources and poor infrastructure. In Africa, the burden of epilepsy is exacerbated by increased risk factors such as central nervous system infections, perinatal insults, and traumatic brain injury. Despite the high incidence of these etiologies, the cause of epilepsy in over 60% of African children is unknown, suggesting a possible genetic origin. Large-scale genetic and genomic research in Europe and North America has revealed new genes and variants underlying disease in a range of epilepsy phenotypes. The relevance of this knowledge to patient care is especially evident among infants with early-onset epilepsies, where early genetic testing can confirm the diagnosis and direct treatment, potentially improving prognosis and quality of life. In Africa, however, genetic epilepsies are among the most under-investigated neurological disorders, and little knowledge currently exists on the genetics of epilepsy among African patients. The increased diversity on the continent may yield unique, important epilepsy-associated genotypes, currently absent from the North American or European diagnostic testing protocols. In this review, we propose that there is strong justification for developing the capacity to offer genetic testing for children with epilepsy in Africa, informed mostly by the existing counseling and interventional needs. Initial simple protocols involving well-recognized epilepsy genes will not only help patients but will give rise to further clinically relevant research, thus increasing knowledge and capacity.

PCDH19-related epilepsy is associated with a broad neurodevelopmental spectrum

OBJECTIVE

To characterize the features associated with PCDH19-related epilepsy, also known as "female-limited epilepsy."

METHODS

We analyzed data from participants enrolled in the PCDH19 Registry, focusing on the seizure-related, developmental, neurobehavioral, and sleep-related features. We evaluated variants for pathogenicity based on previous reports, population databases, and in silico predictions, and included individuals with pathogenic or potentially pathogenic variants. We performed a retrospective analysis of medical records and administered a targeted questionnaire to characterize current or past features in probands and genotype-positive family members.

RESULTS

We included 38 individuals with pathogenic or potentially pathogenic variants in PCDH19: 21 de novo, 5 maternally inherited, 7 paternally inherited, and 5 unknown. All 38 had epilepsy; seizure burden varied, but typical features of clustering of seizures and association with fever were present. Thirty individuals had intellectual disability (ID), with a wide range of severity reported; notably, 8/38 (22%) had average intellect. Behavioral and sleep dysregulation were prominent, in 29/38 (76%) and 20/38 (53%), respectively. Autistic features were present in 22/38 (58%), of whom 12 had a formal diagnosis of autism spectrum disorder. We had additional data from 5 genotype-positive mothers, all with average intellect and 3 with epilepsy, and from 1 genotype-positive father.

SIGNIFICANCE

Our series represents a robust cohort with carefully curated PCDH19 variants. We observed seizures as a core feature with a range of seizure types and severity. Whereas the majority of individuals had ID, we highlight the possibility of average intellect in the setting of PCDH19-related epilepsy. We also note the high prevalence and severity of neurobehavioral phenotypes associated with likely pathogenic variants in PCDH19. Sleep dysregulation was also a major area of concern. Our data emphasize the importance of appropriate referrals for formal neuropsychological evaluations as well as the need for formal prospective studies to characterize the PCDH19-related neurodevelopmental syndrome in children and their genotype-positive parents.

Molecular diagnosis of patients with epilepsy and developmental delay using a customized panel of epilepsy genes

Pediatric epilepsies are a group of disorders with a broad phenotypic spectrum that are associated with great genetic heterogeneity, thus making sequential single-gene testing an impractical basis for diagnostic strategy. The advent of next-generation sequencing has increased the success rate of epilepsy diagnosis, and targeted resequencing using genetic panels is the a most cost-effective choice. We report the results found in a group of 87 patients with epilepsy and developmental delay using targeted next generation sequencing (custom-designed Haloplex panel). Using this gene panel, we were able to identify disease-causing variants in 17 out of 87 (19.5%) analyzed patients, all found in known epilepsy-associated genes (KCNQ2, CDKL5, STXBP1, SCN1A, PCDH19, POLG, SLC2A1, ARX, ALG13, CHD2, SYNGAP1, and GRIN1). Twelve of 18 variants arose de novo and 6 were novel. The highest yield was found in patients with onset in the first years of life, especially in patients classified as having early-onset epileptic encephalopathy. Knowledge of the underlying genetic cause provides essential information on prognosis and could be used to avoid unnecessary studies, which may result in a greater diagnostic cost-effectiveness.

Increasing volume and complexity of pediatric epilepsy surgery with stable seizure outcome between 2008 and 2014: A nationwide multicenter study

OBJECTIVE

The objective of the study was to assess common practice in pediatric epilepsy surgery in Italy between 2008 and 2014.

METHODS

A survey was conducted among nine Italian epilepsy surgery centers to collect information on presurgical and postsurgical evaluation protocols, volumes and types of surgical interventions, and etiologies and seizure outcomes in pediatric epilepsy surgery between 2008 and 2014.

RESULTS

Retrospective data on 527 surgical procedures were collected. The most frequent surgical approaches were temporal lobe resections and disconnections (133, 25.2%) and extratemporal lesionectomies (128, 24.3%); the most frequent etiologies were FCD II (107, 20.3%) and glioneuronal tumors (105, 19.9%). Volumes of surgeries increased over time independently from the age at surgery and the epilepsy surgery center. Engel class I was achieved in 73.6% of patients (range: 54.8 to 91.7%), with no significant changes between 2008 and 2014. Univariate analyses showed a decrease in the proportion of temporal resections and tumors and an increase in the proportion of FCDII, while multivariate analyses revealed an increase in the proportion of extratemporal surgeries over time. A higher proportion of temporal surgeries and tumors and a lower proportion of extratemporal and multilobar surgeries and of FCD were observed in low (<50surgeries/year) versus high-volume centers. There was a high variability across centers concerning pre- and postsurgical evaluation protocols, depending on local expertise and facilities.

SIGNIFICANCE

This survey reveals an increase in volume and complexity of pediatric epilepsy surgery in Italy between 2008 and 2014, associated with a stable seizure outcome.

Male patients affected by mosaic PCDH19 mutations: five new cases

Pathogenic variants in the PCDH19 gene are associated with epilepsy, intellectual disability (ID) and behavioural disturbances. Only heterozygous females and mosaic males are affected, likely due to a disease mechanism named cellular interference. Until now, only four affected mosaic male patients have been described in literature. Here, we report five additional male patients, of which four are older than the oldest patient reported so far. All reported patients were selected for genetic testing because of developmental delay and/or epilepsy. Custom-targeted next generation sequencing gene panels for epilepsy genes were used. Clinical data were collected from medical records. All patients were mosaic in blood for likely pathogenic variants in the PCDH19 gene. In most, clinical features were very similar to the female phenotype, with normal development before seizure onset, which occurred between 5 and 10 months of age, clustering of seizures and sensitivity to fever. Four out of five patients had mild to severe ID and behavioural problems. We reaffirm the similarity between male and female PCDH19-related phenotypes, now also in a later phase of the disorder (ages 10–14 years).

The clinical spectrum of female epilepsy patients with PCDH19 mutations in a Chinese population

Mutations in PCDH19, which encodes protocadherin 19, have been identified in epilepsy, mainly in affected females. We summarized the clinical spectrum of female epilepsy patients with PCDH19 mutations in a Chinese population. We screened for PCDH19 mutations in 75 girls diagnosed with Dravet syndrome (DS) without a SCN1A mutation and 29 girls with fever-sensitive and cluster seizures. We identified 11 novel and 7 reported mutations in 21 of 104 probands (20.2%), including 6 (6/75, 8%) DS girls and 15 (15/29, 51.7%) girls with fever-sensitive epilepsy. The mutations were inherited in 9 probands, de novo in 11, and undetermined in the remaining patient. Shared clinical features included early onset seizures (5-18 months), seizures sensitive to fever, focal seizures or generalized tonic-clonic seizures in clusters and brief seizures. Mental retardation was present in 17 probands. Three patients had autistic features. Two of the nine probands with inherited mutations had no family history of epilepsy, one inherited the mutation from her transmitting father and the other inherited from her asymptomatic mother. Our results confirmed that the clinical spectrum of PCDH19 mutations includes female DS patients, epilepsy and mental retardation limited to females, epilepsy with normal development and asymptomatic female carriers.

Diagnostic Yield of Epilepsy Panels in Children With Medication-Refractory Epilepsy

BACKGROUND

When no chromosomal variations are identified, patients with suspected genetic etiologies can be tested using next-generation sequencing utilizing epilepsy panels. The primary objective of this study was to analyze the diagnostic yield of next-generation sequencing epilepsy panels in medication-resistant epilepsy subjects with non-clinically significant comparative genomic hybridization microarray results.

METHODS

We completed a single-center retrospective review of the diagnostic yield of next-generation sequencing epilepsy panels in medication-resistant epilepsy subjects aged 18 years or less who had non-clinically significant comparative genomic hybridization microarray results from January 2011 to December 2014. The primary end point was the yield of clinically significant next-generation sequencing results.

RESULTS

Forty-nine subjects (21 male) with medication-refractory epilepsy and clinically in significant comparative genomic hybridization microarray results were identified. Next-generation sequencing abnormalities were seen in 28 subjects (57%): seven of these 28 subjects (25%) had clinically significant findings. Mutations were found in the SCN1A gene in three subjects, in the PCDH19 gene in two subjects, and in DLG3, MECP2, TSC2, and SLC9A6 genes in one subject each. Only the MECP2 mutation was found to be pathogenic in this last subject. The additional yield of next-generation sequencing with uninformative chromosomal microarray was 14%. Positive findings were primarily seen in those with Dravet syndrome, all with SCN1A mutations (42% of clinically significant results). Given the small sample size, a larger prospective study would help to determine the clinical yield of next-generation sequencing.

CONCLUSION

Next-generation sequencing seizure panels could be a useful tool in the diagnosis of nonacquired pediatric medication-refractory epilepsy with uninformative comparative genomic hybridization microarray.

Structural determinants of adhesion by Protocadherin-19 and implications for its role in epilepsy

Non-clustered δ-protocadherins are homophilic cell adhesion molecules essential for the development of the vertebrate nervous system, as several are closely linked to neurodevelopmental disorders. Mutations in protocadherin-19 (PCDH19) result in a female-limited, infant-onset form of epilepsy (PCDH19-FE). Over 100 mutations in PCDH19 have been identified in patients with PCDH19-FE, about half of which are missense mutations in the adhesive extracellular domain. Neither the mechanism of homophilic adhesion by PCDH19, nor the biochemical effects of missense mutations are understood. Here we present a crystallographic structure of the minimal adhesive fragment of the zebrafish Pcdh19 extracellular domain. This structure reveals the adhesive interface for Pcdh19, which is broadly relevant to both non-clustered δ and clustered protocadherin subfamilies. In addition, we show that several PCDH19-FE missense mutations localize to the adhesive interface and abolish Pcdh19 adhesion in in vitro assays, thus revealing the biochemical basis of their pathogenic effects during brain development.

DOI:http://dx.doi.org/10.7554/eLife.18529.001

As the brain develops, its basic building blocks – cells called neurons – need to form the correct connections with one another in order to give rise to neural circuits. A mistake that leads to the formation of incorrect connections can result in a number of disorders or brain abnormalities.

Proteins called cadherins that are present on the surface of neurons enable them to stick to their correct partners like Velcro. One of these proteins is called Protocadherin-19. However, it was not fully understood how this protein forms an adhesive bond with other Protocadherin-19 molecules, or how some of the proteins within the cadherin family are able to distinguish between one another.

Cooper et al. used X-ray crystallography to visualize the molecular structure of Protocadherin-19 taken from zebrafish in order to better understand the adhesive bond that these proteins form with each other. In addition, the new structure showed the sites of the mutations that cause a form of epilepsy in infant females. From this, Cooper et al. could predict how the mutations would disrupt Protocadherin-19’s shape and function.

The structures revealed that Protocadherin-19 molecules from adjacent cells engage in a “forearm handshake” to form the bond that connects neurons. Some of the mutations that cause epilepsy occur in the region responsible for this Protocadherin-19 forearm handshake. Laboratory experiments confirmed that these mutations impair the formation of the adhesive bond, revealing the molecular basis for some of the mutations that underlie Protocadherin-19-female-limited epilepsy.

Other cadherin molecules may interact via a similar forearm handshake; this could be investigated in future experiments. It also remains to be discovered how brain wiring depends on Protocadherin-19 adhesion in animal development, and how altering these proteins can rewire developing brain circuits.

DOI:http://dx.doi.org/10.7554/eLife.18529.002