Changing Landscape of Dravet Syndrome Management: An Overview

2020 ◽  
Vol 51 (02) ◽  
pp. 135-145 ◽  
Author(s):  
Debopam Samanta
Keyword(s):  
Motor Impairment ◽  
Current Treatment ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Loss Of Function ◽  
Unexpected Death ◽  
Autistic Behavior ◽  
Behavioral Abnormalities ◽  
Treatment Paradigm ◽  
Antisense Oligonucleotide Therapy

AbstractDravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is a severe developmental and epileptic encephalopathy caused by loss-of-function mutations in one copy of SCN1A (haploinsufficiency), located on chromosome 2q24, with decreased function of Nav1.1 sodium channels in GABAergic inhibitory interneurons. Pharmacoresistant seizures in DS start in the infancy in the form of hemiclonic febrile status epilepticus. Later, other intractable seizure types develop including myoclonic seizures. Early normal development in infancy evolves into moderate to severe intellectual impairment, motor impairment, behavioral abnormalities, and later a characteristic crouching gait. Clobazam, valproate, levetiracetam, topiramate, zonisamide, ketogenic diet, and vagus nerve stimulation had been shown to be effective, but even with polytherapy, only 10% of patients get adequate seizure control. The author provides a narrative review of the current treatment paradigm as well as recent advances in the management of DS based on a comprehensive literature review (MEDLINE using PubMed and OvidSP vendors with appropriate keywords to incorporate recent evidence), personal practice, and experience. In recent years, the treatment paradigm of DS is changing with the approval of pharmaceutical-grade cannabidiol oil and stiripentol. Another novel antiepileptic drug (AED), fenfluramine, had also shown excellent efficacy in phase 3 studies of DS. However, these AEDs primarily control seizures without addressing the underlying pathogenesis and other important common comorbidities such as cognitive impairment, autistic behavior, neuropsychiatric abnormalities, and motor impairment including crouching gait. Several agents targeted for DS are in the developmental stage: TAK935, lorcaserin, clemizole, huperzine analog, ataluren, selective sodium channel modulators and activators, antisense oligonucleotide therapy, and adenoviral vector therapy. As DS is associated with a high risk of sudden unexpected death in epilepsy, seizure detection devices can be used in this population for testing and clinical validation of these devices.

scholarly journals Scn1a gene reactivation after symptom onset rescues pathological phenotypes in a mouse model of Dravet syndrome

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Nicholas Valassina ◽  
Simone Brusco ◽  
Alessia Salamone ◽  
Linda Serra ◽  
Mirko Luoni ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mouse Model ◽  
Symptom Onset ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Neurological Deficits ◽  
Behavioral Alterations ◽  
Unexpected Death ◽  
Physiological Level ◽  
Behavioral Abnormalities

AbstractDravet syndrome is a severe epileptic encephalopathy caused primarily by haploinsufficiency of the SCN1A gene. Repetitive seizures can lead to endurable and untreatable neurological deficits. Whether this severe pathology is reversible after symptom onset remains unknown. To address this question, we generated a Scn1a conditional knock-in mouse model (Scn1a Stop/+) in which Scn1a expression can be re-activated on-demand during the mouse lifetime. Scn1a gene disruption leads to the development of seizures, often associated with sudden unexpected death in epilepsy (SUDEP) and behavioral alterations including hyperactivity, social interaction deficits and cognitive impairment starting from the second/third week of age. However, we showed that Scn1a gene re-activation when symptoms were already manifested (P30) led to a complete rescue of both spontaneous and thermic inducible seizures, marked amelioration of behavioral abnormalities and normalization of hippocampal fast-spiking interneuron firing. We also identified dramatic gene expression alterations, including those associated with astrogliosis in Dravet syndrome mice, that, accordingly, were rescued by Scn1a gene expression normalization at P30. Interestingly, regaining of Nav1.1 physiological level rescued seizures also in adult Dravet syndrome mice (P90) after months of repetitive attacks. Overall, these findings represent a solid proof-of-concept highlighting that disease phenotype reversibility can be achieved when Scn1a gene activity is efficiently reconstituted in brain cells.

scholarly journals Dravet Variant SCN1AA1783V Impairs Interneuron Firing Predominantly by Altered Channel Activation

2021 ◽  
Vol 15 ◽  
Author(s):  
Nikolas Layer ◽  
Lukas Sonnenberg ◽  
Emilio Pardo González ◽  
Jan Benda ◽  
Ulrike B. S. Hedrich ◽  
...  
Keyword(s):  
Current Density ◽  
Input Resistance ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Slow Inactivation ◽  
Loss Of Function ◽  
Peak Current Density ◽  
Channel Activation ◽  
Peak Current

Dravet syndrome (DS) is a developmental epileptic encephalopathy mainly caused by functional NaV1.1 haploinsufficiency in inhibitory interneurons. Recently, a new conditional mouse model expressing the recurrent human p.(Ala1783Val) missense variant has become available. In this study, we provided an electrophysiological characterization of this variant in tsA201 cells, revealing both altered voltage-dependence of activation and slow inactivation without reduced sodium peak current density. Based on these data, simulated interneuron (IN) firing properties in a conductance-based single-compartment model suggested surprisingly similar firing deficits for NaV1.1A1783V and full haploinsufficiency as caused by heterozygous truncation variants. Impaired NaV1.1A1783V channel activation was predicted to have a significantly larger impact on channel function than altered slow inactivation and is therefore proposed as the main mechanism underlying IN dysfunction. The computational model was validated in cortical organotypic slice cultures derived from conditional Scn1aA1783V mice. Pan-neuronal activation of the p.Ala1783V in vitro confirmed a predicted IN firing deficit and revealed an accompanying reduction of interneuronal input resistance while demonstrating normal excitability of pyramidal neurons. Altered input resistance was fed back into the model for further refinement. Taken together these data demonstrate that primary loss of function (LOF) gating properties accompanied by altered membrane characteristics may match effects of full haploinsufficiency on the neuronal level despite maintaining physiological peak current density, thereby causing DS.

scholarly journals Channelopathy of Dravet Syndrome and Potential Neuroprotective Effects of Cannabidiol

2021 ◽  
Vol 13 ◽  
pp. 117957352110480
Author(s):  
Changqing Xu ◽  
Yumin Zhang ◽  
David Gozal ◽  
Paul Carney
Keyword(s):  
Gene Mutations ◽  
Premature Death ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Hcn Channels ◽  
Loss Of Function ◽  
Action Mechanism ◽  
Neuroprotective Effects ◽  
Thermally Induced ◽  
Spontaneous Seizures

Dravet syndrome (DS) is a channelopathy, neurodevelopmental, epileptic encephalopathy characterized by seizures, developmental delay, and cognitive impairment that includes susceptibility to thermally induced seizures, spontaneous seizures, ataxia, circadian rhythm and sleep disorders, autistic-like behaviors, and premature death. More than 80% of DS cases are linked to mutations in genes which encode voltage-gated sodium channel subunits, SCN1A and SCN1B, which encode the Nav1.1α subunit and Nav1.1β1 subunit, respectively. There are other gene mutations encoding potassium, calcium, and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels related to DS. One-third of patients have pharmacoresistance epilepsy. DS is unresponsive to standard therapy. Cannabidiol (CBD), a non-psychoactive phytocannabinoid present in Cannabis, has been introduced for treating DS because of its anticonvulsant properties in animal models and humans, especially in pharmacoresistant patients. However, the etiological channelopathiological mechanism of DS and action mechanism of CBD on the channels are unclear. In this review, we summarize evidence of the direct and indirect action mechanism of sodium, potassium, calcium, and HCN channels in DS, especially sodium subunits. Some channels’ loss-of-function or gain-of-function in inhibitory or excitatory neurons determine the balance of excitatory and inhibitory are associated with DS. A great variety of mechanisms of CBD anticonvulsant effects are focused on modulating these channels, especially sodium, calcium, and potassium channels, which will shed light on ionic channelopathy of DS and the precise molecular treatment of DS in the future.

scholarly journals Astrocyte Ca2+ Signaling is Facilitated in an Scn1a+/− Mouse Model of Dravet Syndrome

2021 ◽  
Author(s):  
Kouya Uchino ◽  
Wakana Ikezawa ◽  
Yasuyoshi Tanaka ◽  
Masanobu Deshimaru ◽  
Kaori Kubota ◽  
...  
Keyword(s):  
Mouse Model ◽  
Sodium Channel ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Heterozygous Mutation ◽  
Loss Of Function ◽  
Cell Type ◽  
Voltage Gated ◽  
A Subunit ◽  
The Brain

Dravet syndrome (DS) is an infantile-onset epileptic encephalopathy. More than 80% of DS patients have a heterozygous mutation in SCN1A, which encodes a subunit of the voltage-gated sodium channel, Nav1.1, in neurons. The roles played by astrocytes, the most abundant glial cell type in the brain, have been investigated in the pathogenesis of epilepsy; however, the specific involvement of astrocytes in DS has not been clarified. In this study, we evaluated Ca2+ signaling in astrocytes using genetically modified mice that have a loss-of-function mutation in Scn1a. We found that the slope of spontaneous Ca2+ spiking was increased without a change in amplitude in Scn1a+/− astrocytes. In addition, ATP-induced transient Ca2+ influx and the slope of Ca2+ spiking were also increased in Scn1a+/− astrocytes. These data indicate that perturbed Ca2+ dynamics in astrocytes may be involved in the pathogenesis of DS.

scholarly journals NaV1.1 and NaV1.6 selective compounds reduce the behavior phenotype in a novel zebrafish model for Dravet Syndrome

2019 ◽  
Author(s):  
Wout J. Weuring ◽  
Sakshi Singh ◽  
Linda Volkers ◽  
Martin Rook ◽  
Ruben H. van ‘t Slot ◽  
...  
Keyword(s):  
Treatment Strategies ◽  
Epileptic Seizures ◽  
Selective Inhibition ◽  
Epileptic Encephalopathy ◽  
Model Systems ◽  
Dravet Syndrome ◽  
Loss Of Function ◽  
Zebrafish Model ◽  
Neuronal Inhibition ◽  
Increased Sensitivity

AbstractDravet syndrome is caused by dominant loss-of-function mutations in SCN1A which cause reduced activity of Nav1.1 leading to lack of neuronal inhibition. On the other hand, gain-of-function mutations in SCN8A can lead to a severe epileptic encephalopathy subtype by over activating NaV1.6 channels. These observations suggest that Nav1.1 and Nav1.6 represent two opposing sides of the neuronal balance between inhibition and activation. Here, we hypothesize that Dravet syndrome may be treated by either enhancing Nav1.1 or reducing Nav1.6 activity. To test this hypothesis we generated and characterized a novel DS zebrafish model and tested new compounds that selectively activate or inhibit the human NaV1.1 or NaV1.6 channel respectively. We used CRISPR/Cas9 to generate two separate Scn1Lab knockout lines as an alternative to previous knock-down models. Using an optimized locomotor assay, spontaneous burst movements were detected that were unique to Scn1Lab knockouts and disappear when introducing human SCN1A mRNA. Besides the behavioral phenotype, Scn1Lab knockouts show sudden, electrical discharges in the brain that indicate epileptic seizures in zebrafish. Scn1Lab knockouts showed increased sensitivity to the convulsant pentylenetetrazole and a reduction in whole organism GABA levels. Drug screenings further validated a Dravet syndrome phenotype. We tested the NaV1.1 activator AA43279 and our newly synthesized NaV1.6 inhibitors MV1369 and MV1312 in the Scn1Lab knockouts. Both type of compounds significantly reduced the number of burst movements. Our results show that selective inhibition of NaV1.6 could be just as efficient as selective activation of NaV1.1 and these approaches could prove to be novel potential treatment strategies for Dravet syndrome and other (genetic) epilepsies. Compounds tested in zebrafish however, should always be further validated in other model systems, preferably human derived.

Antisense oligonucleotides increase Scn1a expression and reduce seizures and SUDEP incidence in a mouse model of Dravet syndrome

2020 ◽  
Vol 12 (558) ◽  
pp. eaaz6100 ◽  
Author(s):  
Zhou Han ◽  
Chunling Chen ◽  
Anne Christiansen ◽  
Sophina Ji ◽  
Qian Lin ◽  
...  
Keyword(s):  
Mouse Model ◽  
Antisense Oligonucleotides ◽  
De Novo ◽  
Nuclear Gene ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Unexpected Death ◽  
Α Subunit ◽  
Gene And Protein Expression ◽  
Electrographic Seizures

Dravet syndrome (DS) is an intractable developmental and epileptic encephalopathy caused largely by de novo variants in the SCN1A gene, resulting in haploinsufficiency of the voltage-gated sodium channel α subunit NaV1.1. Here, we used Targeted Augmentation of Nuclear Gene Output (TANGO) technology, which modulates naturally occurring, nonproductive splicing events to increase target gene and protein expression and ameliorate disease phenotype in a mouse model. We identified antisense oligonucleotides (ASOs) that specifically increase the expression of productive Scn1a transcript in human cell lines, as well as in mouse brain. We show that a single intracerebroventricular dose of a lead ASO at postnatal day 2 or 14 reduced the incidence of electrographic seizures and sudden unexpected death in epilepsy (SUDEP) in the F1:129S-Scn1a+/− × C57BL/6J mouse model of DS. Increased expression of productive Scn1a transcript and NaV1.1 protein was confirmed in brains of treated mice. Our results suggest that TANGO may provide a unique, gene-specific approach for the treatment of DS.

scholarly journals The L1624Q Variant in SCN1A Causes Familial Epilepsy Through a Mixed Gain and Loss of Channel Function

2021 ◽  
Vol 12 ◽  
Author(s):  
Laura B. Jones ◽  
Colin H. Peters ◽  
Richard E. Rosch ◽  
Maxine Owers ◽  
Elaine Hughes ◽  
...  
Keyword(s):  
De Novo ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Gene Encoding ◽  
Channel Function ◽  
Biophysical Analysis ◽  
Gain And Loss ◽  
Patients With Epilepsy

Variants of the SCN1A gene encoding the neuronal voltage-gated sodium channel NaV1.1 cause over 85% of all cases of Dravet syndrome, a severe and often pharmacoresistent epileptic encephalopathy with mostly infantile onset. But with the increased availability of genetic testing for patients with epilepsy, variants in SCN1A have now also been described in a range of other epilepsy phenotypes. The vast majority of these epilepsy-associated variants are de novo, and most are either nonsense variants that truncate the channel or missense variants that are presumed to cause loss of channel function. However, biophysical analysis has revealed a significant subset of missense mutations that result in increased excitability, further complicating approaches to precision pharmacotherapy for patients with SCN1A variants and epilepsy. We describe clinical and biophysical data of a familial SCN1A variant encoding the NaV1.1 L1624Q mutant. This substitution is located on the extracellular linker between S3 and S4 of Domain IV of NaV1.1 and is a rare case of a familial SCN1A variant causing an autosomal dominant frontal lobe epilepsy. We expressed wild-type (WT) and L1642Q channels in CHO cells. Using patch-clamp to characterize channel properties at several temperatures, we show that the L1624Q variant increases persistent current, accelerates fast inactivation onset and decreases current density. While SCN1A-associated epilepsy is typically considered a loss-of-function disease, our results put L1624Q into a growing set of mixed gain and loss-of-function variants in SCN1A responsible for epilepsy.

scholarly journals Selective NaV1.1 activation rescues Dravet syndrome mice from seizures and premature death

2018 ◽  
Vol 115 (34) ◽  
pp. E8077-E8085 ◽  
Author(s):  
Kay L. Richards ◽  
Carol J. Milligan ◽  
Robert J. Richardson ◽  
Nikola Jancovski ◽  
Morten Grunnet ◽  
...  
Keyword(s):  
Disease Onset ◽  
Intractable Epilepsy ◽  
Premature Death ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
First Year ◽  
Inhibitory Interneurons ◽  
Loss Of Function ◽  
Intracerebroventricular Infusion ◽  
First Year Of Life

Dravet syndrome is a catastrophic, pharmacoresistant epileptic encephalopathy. Disease onset occurs in the first year of life, followed by developmental delay with cognitive and behavioral dysfunction and substantially elevated risk of premature death. The majority of affected individuals harbor a loss-of-function mutation in one allele of SCN1A, which encodes the voltage-gated sodium channel NaV1.1. Brain NaV1.1 is primarily localized to fast-spiking inhibitory interneurons; thus the mechanism of epileptogenesis in Dravet syndrome is hypothesized to be reduced inhibitory neurotransmission leading to brain hyperexcitability. We show that selective activation of NaV1.1 by venom peptide Hm1a restores the function of inhibitory interneurons from Dravet syndrome mice without affecting the firing of excitatory neurons. Intracerebroventricular infusion of Hm1a rescues Dravet syndrome mice from seizures and premature death. This precision medicine approach, which specifically targets the molecular deficit in Dravet syndrome, presents an opportunity for treatment of this intractable epilepsy.

scholarly journals De Novo Loss-of-Function Mutations in CHD2 Cause a Fever-Sensitive Myoclonic Epileptic Encephalopathy Sharing Features with Dravet Syndrome

2013 ◽  
Vol 93 (5) ◽  
pp. 967-975 ◽  
Author(s):  
Arvid Suls ◽  
Johanna A. Jaehn ◽  
Angela Kecskés ◽  
Yvonne Weber ◽  
Sarah Weckhuysen ◽  
...  
Keyword(s):  
De Novo ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Loss Of Function

scholarly journals Molecular Mechanisms of Epileptic Encephalopathy Caused by KCNMA1 Loss-of-Function Mutations

2022 ◽  
Vol 12 ◽  
Author(s):  
Yu Yao ◽  
Dongxiao Qu ◽  
Xiaoping Jing ◽  
Yuxiang Jia ◽  
Qi Zhong ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Novel Mutation ◽  
Motor Impairment ◽  
Febrile Seizures ◽  
Epileptic Encephalopathy ◽  
Transcriptomic Analysis ◽  
Loss Of Function ◽  
Astrocyte Activation ◽  
Α Subunit ◽  
Imaging Results

The gene kcnma1 encodes the α-subunit of high-conductance calcium- and voltage-dependent K+ (BK) potassium channel. With the development of generation gene sequencing technology, many KCNMA1 mutants have been identified and are more closely related to generalized epilepsy and paroxysmal dyskinesia. Here, we performed a genetic screen of 26 patients with febrile seizures and identified a novel mutation of KCNMA1 (E155Q). Electrophysiological characterization of different KCNMA1 mutants in HEK 293T cells, the previously-reported R458T and E884K variants (not yet determined), as well as the newly-found E155Q variant, revealed that the current density amplitude of all the above variants was significantly smaller than that of the wild-type (WT) channel. All the above variants caused a positive shift of the I-V curve and played a role through the loss-of-function (LOF) mechanism. Moreover, the β4 subunit slowed down the activation of the E155Q mutant. Then, we used kcnma1 knockout (BK KO) mice as the overall animal model of LOF mutants. It was found that BK KO mice had spontaneous epilepsy, motor impairment, autophagic dysfunction, abnormal electroencephalogram (EEG) signals, as well as possible anxiety and cognitive impairment. In addition, we performed transcriptomic analysis on the hippocampus and cortex of BK KO and WT mice. We identified many differentially expressed genes (DEGs). Eight dysregulated genes [i.e., (Gfap and Grm3 associated with astrocyte activation) (Alpl and Nlrp10 associated with neuroinflammation) (Efna5 and Reln associated with epilepsy) (Cdkn1a and Nr4a1 associated with autophagy)] were validated by RT-PCR, which showed a high concordance with transcriptomic analysis. Calcium imaging results suggested that BK might regulate the autophagy pathway from TRPML1. In conclusion, our study indicated that newly-found point E155Q resulted in a novel loss-of-function variant and the dysregulation of gene expression, especially astrocyte activation, neuroinflammation and autophagy, might be the molecular mechanism of BK-LOF meditated epilepsy.

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