A Genomic Single-Cell Map Explains Neuronal Death in Epilepsy

Summary, originally published on medicalxpress.com

A multidisciplinary team led by researchers from the Spanish Research Council (CSIC) identifies the genomic cellular map associated with hippocampal sclerosis, a major histopathological condition of temporal lobe epilepsy. The study, published in Cell Reports, identifies cell-type specific transcriptional signatures of hyper-excitability and neurodegeneration, providing grounds for improved diagnosis. While the presence of sclerosis is essential for identifying temporal lobe epilepsy (the most common form of drug-resistant epilepsy), it is also detected in some cases of dementia associated with Alzheimer’s disease.

In this work, the researchers have developed a transcriptional map that identifies the precise genetic code of all cell types specifically affected in the disease. “With these maps we seek to match different genes with specific biological elements. In the case of the brain, we aim linking expression of some specific genes with different cell types, such as neurons, astrocytes and microglia,” explains Liset Menéndez de la Prida, a scientist at the Cajal Institute of the CSIC, who lead the study together with José López-Atalaya, from the Institute of Neurosciences (CSIC-UMH) in Alicante.

Phenotypic Analysis of Catastrophic Childhood Epilepsy Genes

Featuring the work of former CURE Epilepsy grantee Dr. Scott Baraban

Abstract, originally published in Communications Biology

Genetic engineering techniques have contributed to the now widespread use of zebrafish to investigate gene function, but zebrafish-based human disease studies, and particularly for neurological disorders, are limited. Here we used CRISPR-Cas9 to generate 40 single-gene mutant zebrafish lines representing catastrophic childhood epilepsies. We evaluated larval phenotypes using electrophysiological, behavioral, neuro-anatomical, survival and pharmacological assays. Local field potential recordings (LFP) were used to screen ?3300 larvae. Phenotypes with unprovoked electrographic seizure activity (i.e., epilepsy) were identified in zebrafish lines for 8 genes; ARX, EEF1A, GABRB3, GRIN1, PNPO, SCN1A, STRADA and STXBP1. We also created an open-source database containing sequencing information, survival curves, behavioral profiles and representative electrophysiology data. We offer all zebrafish lines as a resource to the neuroscience community and envision them as a starting point for further functional analysis and/or identification of new therapies.

Disparate Treatment Outcomes According to Presence of Pathogenic Mutations in West Syndrome

Abstract, originally published in Epilepsia

Objective: It has been known that West syndrome (WS) patients with an unknown etiology have better clinical outcomes than patients with an identified etiology of any kind. However, after the exponential discovery of genes with mutations responsible for developmental and epileptic encephalopathy (DEE), a significant proportion of patients with a previously unknown etiology have been reclassified as having a genetic etiology, requiring reinvestigation of this concept. Therefore, this study investigated clinical outcomes of WS patients with genetic and unknown etiologies.

Methods: Patients diagnosed with WS without structural or metabolic abnormalities were included in this study. The DEE gene panel, comprising 172 genes, was performed for all patients. All patients were treated using the same treatment protocol for vigabatrin and high-dose prednisolone add-on therapy. Favorable responders were defined as patients who were seizure-free and whose electroencephalogram showed Burden of Amplitudes and Epileptiform Discharges scores of 2 or less.

Results: Of the 58 patients included in the study, 17 (29.3%) patients had an identified genetic etiology. There was no significant difference in rates of favorable response at 1 and 3 months after treatment, but significantly higher proportions of patients exhibited favorable responses among those with an unknown etiology at long-term follow-up (41.2% vs. 78.0%, p = .006 at 6 months; 29.4% vs. 65.9%, p = .011 at 1 year; 23.5 vs. 65.9%, p = .003 at 2 years). Moreover, the mental, psychomotor, and social age quotients of the patients with an identified genetic etiology were reduced to a significantly greater degree since diagnosis compared with those of the patients with an unknown etiology.

Significance: WS patients with genetic and unknown etiologies did not initially exhibit significantly different response rates to the vigabatrin and high-dose prednisolone add-on treatment. However, patients with a genetic etiology exhibited significantly higher relapse rates and significantly poorer long-term responses.

Development of an Antiseizure Drug Screening Platform for Dravet Syndrome at the NINDS Contract Site for the Epilepsy Therapy Screening Program

Abstract, originally published in Epilepsia

Objective: Dravet syndrome (DS) is a rare but catastrophic genetic epilepsy, with 80% of patients carrying a mutation in the SCN1A gene. Currently, no antiseizure drug (ASD) exists that adequately controls seizures. In the clinic, individuals with DS often present first with a febrile seizure and, subsequently, generalized tonic-clonic seizures that can continue throughout life. To facilitate the development of ASDs for DS, the contract site of the National Institute of Neurological Disorders and Stroke (NINDS) Epilepsy Therapy Screening Program (ETSP) has evaluated a mouse model of DS using the conditional knock-in Scn1aA1783V/WT mouse.

Methods: Survival rates and temperature thresholds for Scn1aA1783V/WT were determined. Prototype ASDs were administered via intraperitoneal injections at the time-to-peak effect, which was previously determined, prior to the induction of hyperthermia-induced seizures. ASDs were considered effective if they significantly increased the temperature at which Scn1aA1783V/WT mice had seizures.

Results: Approximately 50% of Scn1aA1783V/WT survive to adulthood and all have hyperthermia-induced seizures. The results suggest that hyperthermia-induced seizures in this model of DS are highly refractory to a battery of ASDs. Exceptions were clobazam, tiagabine, levetiracetam, and the combination of clobazam and valproic acid with add-on stiripentol, which elevated seizure thresholds.

Significance: Overall, the data demonstrate that the proposed model for Dravet syndrome is suitable for screening novel compounds for the ability to block hyperthermia-induced seizures and that heterozygous mice can be evaluated repeatedly over the course of several weeks, allowing for higher throughput screening.

Genetic Associations of Neurodevelopmental Disorders with Epilepsy in Adults

Summary, originally published on docwirenews.com

Often, genetic diagnostics of neurodevelopmental disorders with epilepsy (NDDE) focus largely on children, leaving a scarcity of data regarding adult patients. A study published in Genetics in Medicine analyzed genetic associations of NDDE in adults and elderly patients.

A total of 150 patients with NDDE underwent conventional karyotyping, FMR1 testing, chromosomal microarray, and panel sequencing. When cases remained unresolved, exome sequencing was performed.

“Panel/exome sequencing displayed the highest yield and should be considered as first-tier diagnostics in NDDE. This high yield and the numerous indications for additional screening or treatment modifications arising from genetic diagnoses indicate a current medical undersupply of genetically undiagnosed adult/elderly individuals with NDDE. Moreover, knowledge of the course of elderly individuals will ultimately help in counseling newly diagnosed individuals with NDDE,” the study authors concluded.

Genome-Wide Association Study of Epilepsy in a Japanese Population Identified an Associated Region at Chromosome 12q24

Abstract, originally published in Epilepsia

Objective: Although a number of genes responsible for epilepsy have been identified through Mendelian genetic approaches, and genome-wide association studies (GWASs) have implicated several susceptibility loci, the role of ethnic-specific markers remains to be fully explored. We aimed to identify novel genetic associations with epilepsy in a Japanese population.

Methods: We conducted a GWAS on 1825 patients with a variety of epilepsies and 7975 control individuals. Expression quantitative trait locus (eQTL) analysis of epilepsy-associated single nucleotide polymorphisms (SNPs) was performed using Japanese eQTL data.

Results: We identified a novel region, which is ~2 Mb (lead SNP rs149212747, p = 8.57 × 10-10 ), at chromosome 12q24 as a risk for epilepsy. Most of these loci were polymorphic in East Asian populations including Japanese, but monomorphic in the European population. This region harbors 24 transcripts including genes expressed in the brain such as CUX2, ATXN2, BRAP, ALDH2, ERP29, TRAFD1, HECTD4, RPL6, PTPN11, and RPH3A. The eQTL analysis revealed that the associated SNPs are also correlated to differential expression of genes at 12q24.

Significance: These findings suggest that a gene or genes in the CUX2-RPH3A ~2-Mb region contribute to the pathology of epilepsy in the Japanese population.

Reproductive Decision-Making in Families Containing Multiple Individuals With Epilepsy

Abstract, originally published in Epilepsia

Objective: This study evaluated factors influencing reproductive decision-making in families containing multiple individuals with epilepsy.

Methods: One hundred forty-nine adults with epilepsy and 149 adult biological relatives without epilepsy from families containing multiple affected individuals completed a self-administered questionnaire. Participants answered questions regarding their belief in a genetic cause of epilepsy (genetic attribution) and estimated risk of epilepsy in offspring of an affected person. Participants rated factors for their influence on their reproductive plans, with responses ranging from “much more likely” to “much less likely” to want to have a child. Those with epilepsy were asked, “Do you think you would have wanted more (or any) children if you had not had epilepsy?”

Results: Participants with epilepsy had fewer offspring than their unaffected relatives (mean = 1.2 vs. 1.9, p = .002), and this difference persisted among persons who had been married. Estimates of risk of epilepsy in offspring of an affected parent were higher among participants with epilepsy than among relatives without epilepsy (mean = 27.2 vs. 19.6, p = .002). Nineteen percent of participants with epilepsy responded that they would have wanted more children if they had not had epilepsy. Twenty-five percent of participants with epilepsy responded that “the chance of having a child with epilepsy” or “having epilepsy in your family” made them less likely to want to have a child. Having these genetic concerns was significantly associated with greater genetic attribution and estimated risk of epilepsy in offspring of an affected parent.

Significance: People with epilepsy have fewer children than their biological relatives without epilepsy. Beliefs about genetic causes of epilepsy contribute to concerns and decisions to limit childbearing. These beliefs should be addressed in genetic counseling to ensure that true risks to offspring and reproductive options are well understood.

Adult Phenotype of KCNQ2 Encephalopathy

Abstract, originally published in Neurogenetics

Background: Pathogenic KCNQ2 variants are a frequent cause of developmental and epileptic encephalopathy.

Methods: We recruited 13 adults (between 18 years and 45 years of age) with KCNQ2 encephalopathy and reviewed their clinical, EEG, neuroimaging and treatment history.

Results: While most patients had daily seizures at seizure onset, seizure frequency declined or remitted during childhood and adulthood. The most common seizure type was tonic seizures (early) infancy, and tonic-clonic and focal impaired awareness seizures later in life. Ten individuals (77%) were seizure-free at last follow-up. In 38% of the individuals, earlier periods of seizure freedom lasting a minimum of 2 years followed by seizure recurrence had occurred. Of the 10 seizure-free patients, 4 were receiving a single antiseizure medication (ASM, carbamazepine, lamotrigine or levetiracetam), and 2 had stopped taking ASM. Intellectual disability (ID) ranged from mild to profound, with the majority (54%) of individuals in the severe category. At last contact, six individuals (46%) remained unable to walk independently, six (46%) had limb spasticity and four (31%) tetraparesis/tetraplegia. Six (46%) remained non-verbal, 10 (77%) had autistic features/autism, 4 (31%) exhibited aggressive behavior and 4 (31%) destructive behavior with self-injury. Four patients had visual problems, thought to be related to prematurity in one. Sleep problems were seen in six (46%) individuals.

Conclusion: Seizure frequency declines over the years and most patients are seizure-free in adulthood. Longer seizure-free periods followed by seizure recurrence are common during childhood and adolescence. Most adult patients have severe ID. Motor, language and behavioral problems are an issue of continuous concern.

Mutations in the Neurochondrin Gene Linked to Epilepsy

Summary, originally published by Uppsala University

Mutations in the neurochondrin (NCDN) gene can cause epilepsy, neurodevelopmental delay and intellectual disability. The gene mutation significantly impairs contacts and signaling between neurons in the brain. This is the conclusion of a study led from Uppsala University and published in the American Journal of Human Genetics.

“The mutation may provide an additional explanation as to why people suffer from these conditions, making it easier to diagnose affected individuals. These are common ailments that are often diagnosed in preschool-age children. They raise concerns and questions among the parents of the affected children: Is this due to something going wrong during pregnancy, childbirth or infancy? Was there something wrong with our germ cells and is it hereditary? The mutations we have identified sometimes arise in individual germ cells prior to conception itself. It is then a matter of chance that they happen upon the neurochondrin gene to produce these effects,” says Niklas Dahl, senior consultant and professor of clinical genetics at Uppsala University’s Department of Immunology, Genetics and Pathology.

The study, which was led from Uppsala University, began by analyzing a worldwide database of genetic analyses of entire genomes. Researchers and physicians from around the world report genome abnormalities that they come across in patients or while conducting research, making it possible to see if any similar cases have been reported anywhere in the world. In Uppsala, researchers initially identified three cases of mutation in the NCDN gene.

Researchers Provide Complete Clinical Landscape for Gene Linked to Epilepsy and Autism

Summary, originally published by Children’s Hospital of Philadelphia

Researchers from Children’s Hospital of Philadelphia (CHOP) affiliated with the CHOP Epilepsy Neurogenetics Initiative (ENGIN) have compiled a complete genetic and clinical analysis of more than 400 individuals with SCN2A-related disorder, which has been linked to a variety of neurodevelopmental disorders, including epilepsy and autism. By linking clinical features to genetic abnormalities in a standardized format, the researchers hope their findings lead to improved identification and clinical intervention.

The study was published online by the journal Genetics in Medicine.

Pathogenic variants in the SCN2A gene can lead to a wide range of clinical features – or phenotypes – associated with neurodevelopmental disorders. Several studies have described the genetic information collected on individuals with disease-causing changes in this gene. However, while genetic information is collected in a standardized manner, data on phenotypes is not standardized, and prior to this study, the available data on clinical features of these patients had not been thoroughly analyzed, meaning that many correlations between the genotypes and phenotypes of these patients were often anecdotal.