Explore the vast range of titles available.

Heterozygous loss-of-function mutations in the brain sodium channel Na V1.1 cause Dravet syndrome (DS), a pharmacoresistant infantile-onset epilepsy syndrome with comorbidities of cognitive impairment and premature death. Previous studies using a mouse model of DS revealed reduced sodium currents and impaired excitability in GABAergic interneurons in the hippocampus, leading to the hypothesis that impaired excitability of GABAergic inhibitory neurons is the cause of epilepsy and premature death in DS. However, other classes of GABAergic interneurons are less impaired, so the direct cause of hyperexcitability, epilepsy, and premature death has remained unresolved. We generated a floxed Scn1a mouse line and used the Cre-Lox method driven by an enhancer from the Dlx 1,2 locus for conditional deletion of Scn1a in forebrain GABAergic neurons. Immunocytochemical studies demonstrated selective loss of Na V1.1 channels in GABAergic interneurons in cerebral cortex and hippocampus. Mice with this deletion died prematurely following generalized tonic-clonic seizures, and they were equally susceptible to thermal induction of seizures as mice with global deletion of Scn1a . Evidently, loss of Na V1.1 channels in forebrain GABAergic neurons is both necessary and sufficient to cause epilepsy and premature death in DS.

Mitochondrial deficits in energy production cause untreatable and fatal pathologies known as mitochondrial disease (MD). Central nervous system affectation is critical in Leigh Syndrome (LS), a common MD presentation, leading to motor and respiratory deficits, seizures and premature death. However, only specific neuronal populations are affected. Furthermore, their molecular identity and their contribution to the disease remains unknown. Here, using a mouse model of LS lacking the mitochondrial complex I subunit Ndufs4, we dissect the critical role of genetically-defined neuronal populations in LS progression. Ndufs4 inactivation in Vglut2-expressing glutamatergic neurons leads to decreased neuronal firing, brainstem inflammation, motor and respiratory deficits, and early death. In contrast, Ndufs4 deletion in GABAergic neurons causes basal ganglia inflammation without motor or respiratory involvement, but accompanied by hypothermia and severe epileptic seizures preceding death. These results provide novel insight in the cell type-specific contribution to the pathology, dissecting the underlying cellular mechanisms of MD. Mitochondria are often described as the power plants of cells because they generate most of the energy that a cell needs to survive. But one in every 5,000 children is born with a mutation that leads to faulty mitochondria, which generate less energy than their healthy counterparts. This is particularly problematic for tissues with high energy demands, such as the brain and muscles. Children with such mutations are said to have mitochondrial disease, and one of the most common and severe forms is Leigh syndrome. Children with Leigh syndrome suffer from epilepsy, and have difficulties with movement and breathing. There is no treatment for Leigh syndrome, and most of those affected will die in childhood. The brains of children with Leigh syndrome show a characteristic pattern of damage and inflammation, symmetrical across both hemispheres, with two areas of the brain affected the most. First, the brainstem, which connects the brain with the spinal cord and is responsible for many vital functions such as breathing, maintaining the heart rate or swallowing. Secondly, a group of neurons deep within the brain called the basal ganglia, which has a role in voluntary movement. But although all of a patient’s neurons carry the mutation responsible for their Leigh syndrome, not every neuron is harmed by it. Knowing which neurons are affected, and why, could help develop treatments. Bolea, Gella, Sanz et al. therefore introduced the same Leigh syndrome mutation into different groups of neurons in three groups of mice. The first group had the mutation in the neurons that activate other cells, called glutamatergic or 'go' neurons. The second group had the mutation in the neurons that inhibit other cells, known as GABAergic, or 'stop', neurons. The third had the mutation in cholinergic neurons, which carry information from the brain to the organs. Examining the mice revealed that having faulty mitochondria in GABAergic neurons from the basal ganglia and in glutamatergic neurons of the brainstem, but not in cholinergic neurons, leads to the symptoms of Leigh syndrome. The fault in the GABAergic neurons causes the epilepsy associated with the syndrome, while faulty mitochondria in the glutamatergic neurons give rise to the observed impairments in movement and breathing. This work could help researchers identify the cellular mechanisms that make neurons more or less resistant to the effects of faulty mitochondria. This in turn will provide a stepping stone to developing new treatments, which can then be tested on the mice developed for these experiments.

Heterozygous loss-of-function mutations in the α subunit of the type I voltage-gated sodium channel $Na_V 1.1$ cause severe myoclonic epilepsy in infancy (SMEI), an infantile-onset epileptic encephalopathy characterized by normal development followed by treatment-refractory febrile and afebrile seizures and psychomotor decline. Mice with SMEI (mSMEl), created by heterozygous deletion of $Na_V 1.1$ channels, develop seizures and ataxia. Here we investigated the temperature and age dependence of seizures and interictal epileptiform spikeand-wave activity in mSMEl. Combined video-EEG monitoring demonstrated that mSMEl had seizures induced by elevated body core temperature but wild-type mice were unaffected. In the 3 age groups tested, no postnatal day (P) 17-18 mSMEl had temperature-induced seizures, but nearly all P20-22 and P30-46 mSMEl had myoclonic seizures followed by generalized seizures caused by elevated core body temperature. Spontaneous seizures were only observed in mice older than P32, suggesting that mSMEl become susceptible to temperature-induced seizures before spontaneous seizures. Interictal spike activity was seen at normal body temperature in most P30-46 mSMEl but not in P20-22 or P17-18 mSMEl, indicating that interictal epileptic activity correlates with seizure susceptibility. Most P20-22 mSMEl had interictal spike activity with elevated body temperature. Our results define a critical developmental transition for susceptibility to seizures in SMEI, demonstrate that body temperature elevation alone is sufficient to induce seizures, and reveal a close correspondence between human and mouse SMEI in the striking temperature and age dependence of seizure frequency and severity and in the temperature dependence and frequency of interictal epileptiform spike activity.

Voltage-gated sodium channels (Na V ) are critical for initiation of action potentials. Heterozygous loss-of-function mutations in Na V 1.1 channels cause severe myoclonic epilepsy in infancy (SMEI). Homozygous null Scn1a −/− mice developed ataxia and died on postnatal day (P) 15 but could be sustained to P17.5 with manual feeding. Heterozygous Scn1a +/− mice had spontaneous seizures and sporadic deaths beginning after P21, with a notable dependence on genetic background. Loss of Na V 1.1 did not change voltage-dependent activation or inactivation of sodium channels in hippocampal neurons. The sodium current density was, however, substantially reduced in inhibitory interneurons of Scn1a +/− and Scn1a −/− mice but not in their excitatory pyramidal neurons. An immunocytochemical survey also showed a specific upregulation of Na V 1.3 channels in a subset of hippocampal interneurons. Our results indicate that reduced sodium currents in GABAergic inhibitory interneurons in Scn1a +/− heterozygotes may cause the hyperexcitability that leads to epilepsy in patients with SMEI.

Mutations in the catalytic subunit of phosphoinositide 3-kinase ( PIK3CA) and other PI3K-AKT pathway components have been associated with cancer and a wide spectrum of brain and body overgrowth. In the brain, the phenotypic spectrum of PIK3CA -related segmental overgrowth includes bilateral dysplastic megalencephaly, hemimegalencephaly and focal cortical dysplasia, the most common cause of intractable pediatric epilepsy. We generated mouse models expressing the most common activating Pik3ca mutations ( H1047R and E545K ) in developing neural progenitors. These accurately recapitulate all the key human pathological features including brain enlargement, cortical malformation, hydrocephalus and epilepsy, with phenotypic severity dependent on the mutant allele and its time of activation. Underlying mechanisms include increased proliferation, cell size and altered white matter. Notably, we demonstrate that acute 1 hr-suppression of PI3K signaling despite the ongoing presence of dysplasia has dramatic anti-epileptic benefit. Thus PI3K inhibitors offer a promising new avenue for effective anti-epileptic therapy for intractable pediatric epilepsy patients. An enzyme called PI3K is involved in a major signaling pathway that controls cell growth. Mutations in this pathway have devastating consequences. When such mutations happen in adults, they can lead to cancer. Mutations that occur in embryos can cause major developmental birth defects, including abnormally large brains. After birth, these developmental problems can cause intellectual disabilities, autism and epilepsy. Children with this kind of epilepsy often do not respond to currently available seizure medications. There are several outstanding questions that if answered could help efforts to develop treatments for children with brain growth disorders. Firstly, how do the developmental abnormalities happen? Do the abnormalities themselves cause epilepsy? And can drugs that target this pathway, and are already in clinical trials for cancer, control seizures? Now, Roy et al. have made mouse models of these human developmental brain disorders and used them to answer these questions. The mice were genetically engineered to have various mutations in the gene that encodes the catalytic subunit of the PI3K enzyme. The mutations were the same as those found in people with brain overgrowth disorders, and were activated only in the developing brain of the mice. These mutations caused enlarged brain size, fluid accumulation in the brain, brain malformations and epilepsy in developing mice – thus mimicking the human birth defects. The severity of these symptoms depended on the specific mutation and when the mutant genes were turned on during development. Next, Roy et al. studied these mice to see if the seizures could be treated using a drug, that has already been developed for brain cancer. This drug specifically targets and reduces the activity of PI3K. Adult mutant mice with brain malformations were treated for just one hour; this dramatically reduced their seizures. These experiments prove that seizures associated with this kind of brain overgrowth disorder are driven by ongoing abnormal PI3K activity and can be treated even when underlying brain abnormalities persist. Roy et al. suggest that drugs targeting PI3K might help treat seizures in children with these brain overgrowth disorders.

Patients harboring mutations in the PI3K-AKT-MTOR pathway-encoding genes often develop a spectrum of neurodevelopmental disorders including epilepsy. A significant proportion remains unresponsive to conventional anti-seizure medications. Understanding mutation-specific pathophysiology is thus critical for molecularly targeted therapies. We previously determined that mouse models expressing a patient-related activating mutation in PIK3CA , encoding the p110α catalytic subunit of phosphoinositide-3-kinase (PI3K), are epileptic and acutely treatable by PI3K inhibition, irrespective of dysmorphology. Here we report the physiological mechanisms underlying this dysregulated neuronal excitability. In vivo , we demonstrate epileptiform events in the Pik3ca mutant hippocampus. By ex vivo analyses, we show that Pik3ca-driven hyperactivation of hippocampal pyramidal neurons is mediated by changes in multiple non-synaptic, cell-intrinsic properties. Finally, we report that acute inhibition of PI3K or AKT, but not MTOR activity, suppresses the intrinsic hyperactivity of the mutant neurons. These acute mechanisms are distinct from those causing neuronal hyperactivity in other AKT-MTOR epileptic models and define parameters to facilitate the development of new molecularly rational therapeutic interventions for intractable epilepsy.

Sudden unexpected death in epilepsy (SUDEP) is the most common cause of death in intractable epilepsies, but physiological mechanisms that lead to SUDEP are unknown. Dravet syndrome (DS) is an infantile-onset intractable epilepsy caused by heterozygous loss-of-function mutations in the SCN1A gene, which encodes brain type-I voltage-gated sodium channel NaV1.1. We studied the mechanism of premature death in Scn1a heterozygous KO mice and conditional brain- and cardiac-specific KOs. Video monitoring demonstrated that SUDEP occurred immediately following generalized tonic-clonic seizures. A history of multiple seizures was a strong risk factor for SUDEP. Combined video-electroencephalography-electrocardiography revealed suppressed interictal resting heart-rate variability and episodes of ictal bradycardia associated with the tonic phases of generalized tonic-clonic seizures. Prolonged atropine-sensitive ictal bradycardia preceded SUDEP. Similar studies in conditional KO mice demonstrated that brain, but not cardiac, KO of Scn1a produced cardiac and SUDEP phenotypes similar to those found in DS mice. Atropine or N-methyl scopolamine treatment reduced the incidence of ictal bradycardia and SUDEP in DS mice. These findings suggest that SUDEP is caused by apparent parasympathetic hyperactivity immediately following tonic-clonic seizures in DS mice, which leads to lethal bradycardia and electrical dysfunction of the ventricle. These results have important implications for prevention of SUDEP in DS patients.

Dravet syndrome (DS) is a devastating developmental epileptic encephalopathy marked by treatment-resistant seizures, developmental delay, intellectual disability, motor deficits, and a 10-20% rate of premature death. Most DS patients harbor loss-of-function mutations in one copy of , which has been associated with inhibitory neuron dysfunction. Here we developed an interneuron-targeting AAV human gene replacement therapy using cell class-specific enhancers. We generated a split-intein fusion form of to circumvent AAV packaging limitations and deliver via a dual vector approach using cell class-specific enhancers. These constructs produced full-length Na 1.1 protein and functional sodium channels in HEK293 cells and in brain cells . After packaging these vectors into enhancer-AAVs and administering to mice, immunohistochemical analyses showed telencephalic GABAergic interneuron-specific and dose-dependent transgene biodistribution. These vectors conferred strong dose-dependent protection against postnatal mortality and seizures in two DS mouse models carrying independent loss-of-function alleles of at two independent research sites, supporting the robustness of this approach. No mortality or toxicity was observed in wild-type mice injected with single vectors expressing either the N-terminal or C-terminal halves of , or the dual vector system targeting interneurons. In contrast, nonselective neuronal targeting of conferred less rescue against mortality and presented substantial preweaning lethality. These findings demonstrate proof-of-concept that interneuron-specific AAV-mediated gene replacement is sufficient for significant rescue in DS mouse models and suggest it could be an effective therapeutic approach for patients with DS.

Objective Sudden unexpected death in epilepsy (SUDEP) is a rare but devastating consequence of epilepsy and is the leading cause of death in people with epilepsy. SUDEP is associated with certain characteristics such as the presence of generalized tonic–clonic seizures, duration of epilepsy, and refractoriness to anti‐seizure medications. Despite insights from in vivo models, gaps persist in understanding the biological causes of SUDEP, leading to a lack of preventative tools. Current SUDEP preclinical models and data collection and reporting can vary widely across laboratories, hindering the direct translation of findings to humans. Methods The 2020 SUDEP Coalition Summit brought together a team of experts to chart areas of growth and tactics to address these areas. A critical research priority revealed during the summit was the development of data standardization tools to unify SUDEP research efforts. In response, CURE Epilepsy established a Steering Committee to oversee an effort to develop data standardization tools and worked with community members composed of experts in specific domains of SUDEP research to define these tools. Results Experts developed common data elements (CDEs) and case report forms (CRFs) to systematize preclinical SUDEP research. An accompanying publication describes the priority core and death‐related information CRF, while the current work describes supplemental CRFs that SUDEP researchers can use. Specifically, CDEs related to neurological variables, physiologic measures, therapeutics and pharmacology, neuroimaging, ex vivo electrophysiology, and additional phenotypes related to epilepsy are described. Significance Along with the core and death‐related CRF, supplemental CRFs can help the unification of SUDEP research by systematizing various endpoints. Adoption of these data standardization tools can also enhance collaboration between teams, hasten the translatability of SUDEP research to the human condition, and ultimately help prevent SUDEP. Plain Language Summary Preclinical sudden unexpected death in epilepsy (SUDEP) research holds great promise for addressing this fatal condition; however, lack of data standardization remains an issue. Other fields have shown that the incorporation of common data elements (CDEs) can serve to harmonize data across groups, increase rigor, and improve translatability. An accompanying paper describes “Core” CDEs that could be used by all SUDEP preclinical researchers; the current manuscript describes related, supplemental CDEs applicable to researchers depending on their specific scientific question. These include neurological and physiological measures, therapeutics and pharmacology, neuroimaging, ex vivo electrophysiology, and additional phenotypes related to epilepsy.

Objective Sudden Unexpected Death in Epilepsy (SUDEP) is a fatal complication for individuals living with epilepsy and is associated with significant personal and public burden. While certain neurotransmitters and neuronal pathways have been associated with SUDEP, the exact biological mechanisms are unknown. Preclinical research has been instrumental in providing clues to the underlying pathology but is limited by a lack of standardized methodologies for describing and collecting data. A key outcome of the Basic Science working group of the 2020 SUDEP Coalition Summit was the recognition that the development of standardized tools would greatly enhance SUDEP research. Such a research infrastructure would increase experimental rigor, repeatability, reproducibility, and transparency and finally, increase the chances that preclinical SUDEP research can be translated into human SUDEP. Methods CURE Epilepsy assembled a Steering Committee and working groups consisting of experts in preclinical and clinical SUDEP research to develop Common Data Elements (CDEs) and Case Report Forms (CRFs) to enable standardization and translation of preclinical SUDEP data. Standardized methodology from the development of other epilepsy‐related CDEs was used. Results The Core and Death‐Related Information CRF constitutes the priority CRF for SUDEP preclinical studies. This CRF gives investigators CDEs to note details of animal models used, experiment‐related information, and details about triggered and spontaneous seizures. The seizure‐related death information consists of CDEs related to observations at the time of death, characteristics of fatal seizures, the posture of the animal at the time of death, diet, medications, and any adverse health conditions. Significance Systematic use of CDEs and CRFs in SUDEP preclinical research can help increase the rigor and transparency of research. Core CDEs along with supplemental CDEs described in the accompanying manuscript can aid investigators and groups working together toward a common goal of preventing SUDEP. Plain Language Summary Sudden Unexpected Death in Epilepsy (SUDEP) is a fatal complication of epilepsy. Preclinical research holds promise in understanding and preventing SUDEP, but its impacts are limited due to a lack of data standardization and translation among research groups. Common data elements (CDEs) are essential pieces of information for a certain field of study. CURE Epilepsy brought together a team of researchers to develop CDEs that could serve as a blueprint for all SUDEP preclinical researchers. This paper describes the SUDEP Core and Death‐Related CDEs to be used with data elements presented in an accompanying paper.