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Gene expression profiling in a mouse model of Dravet syndrome.

ABSTRACT: Dravet syndrome is a severe, early-onset epileptic encephalopathy frequently resulting from de novo mutations of SCN1A. Mice with heterozygous deletion of Scn1a (Scn1a+/-) model many features of Dravet syndrome, including spontaneous seizures and premature lethality. Scn1a+/- mice exhibit variable phenotype penetrance and expressivity dependent upon the strain background. On the 129S6/SvEvTac (129) strain, Scn1a+/- mice do not display an overt phenotype. However Scn1a+/- mice on the [129S6xB6]F1 strain (F1.Scn1a+/-) exhibit juvenile-onset spontaneous seizures and premature lethality. QTL mapping identified several modifier loci responsible for strain-dependent differences in survival of Scn1a+/- mice, but these loci do not account for all the observed phenotypic variance. Global RNA-seq analysis was performed to identify additional genes and pathways that may contribute to variable phenotypes. Hippocampal gene expression was analyzed in wild-type (WT) and Scn1a+/- mice on both F1 and 129 strains, at two time points during disease development. There were few gene expression differences between 129.WT and 129.Scn1a+/- mice and approximately 100 genes with small expression differences (6-36%) between F1.WT and F1.Scn1a+/- mice. Strain-specific gene expression differences were more pronounced, with dozens of genes with >1.5-fold expression differences between 129 and F1 strains. Age-specific and seizure-related gene expression differences were most prominent, with hundreds of genes with >2-fold differences in expression identified between groups with and without seizures, suggesting potential differences in developmental trajectory and/or homeostatic plasticity during disease onset. Global expression differences in the context of Scn1a deletion may account for strain-dependent variation in seizure susceptibility and survival observed in Scn1a+/- mice.

SUBMITTER: Hawkins NA

PROVIDER: S-EPMC6287761 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Gene expression profiling in a mouse model of Dravet syndrome.

Hawkins Nicole A NA Calhoun Jeffrey D JD Huffman Alexandra M AM Kearney Jennifer A JA

Experimental neurology 20181019

Dravet syndrome is a severe, early-onset epileptic encephalopathy frequently resulting from de novo mutations of SCN1A. Mice with heterozygous deletion of Scn1a (Scn1a+/-) model many features of Dravet syndrome, including spontaneous seizures and premature lethality. Scn1a+/- mice exhibit variable phenotype penetrance and expressivity dependent upon the strain background. On the 129S6/SvEvTac (129) strain, Scn1a+/- mice do not display an overt phenotype. However ...[more]

PMID: 30347190

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Project description:Recurrent seizures, which define epilepsy, are transient abnormalities in the electrical activity of the brain. The mechanistic basis of seizure initiation, and the contribution of defined neuronal subtypes to seizure pathophysiology, remains poorly understood. We performed in vivo two-photon calcium imaging in neocortex during temperature-induced seizures in male and female Dravet syndrome (Scn1a+/-) mice, a neurodevelopmental disorder with prominent temperature-sensitive epilepsy. Mean activity of both putative principal cells and parvalbumin-positive interneurons (PV-INs) was higher in Scn1a+/- relative to wild-type controls during quiet wakefulness at baseline and at elevated core body temperature. However, wild-type PV-INs showed a progressive synchronization in response to temperature elevation that was absent in PV-INs from Scn1a+/- mice. Hence, PV-IN activity remains intact interictally in Scn1a+/- mice, yet exhibits decreased synchrony immediately before seizure onset. We suggest that impaired PV-IN synchronization may contribute to the transition to the ictal state during temperature-induced seizures in Dravet syndrome.SIGNIFICANCE STATEMENT Epilepsy is a common neurological disorder defined by recurrent, unprovoked seizures. However, basic mechanisms of seizure initiation and propagation remain poorly understood. We performed in vivo two-photon calcium imaging in an experimental model of Dravet syndrome (Scn1a+/- mice)-a severe neurodevelopmental disorder defined by temperature-sensitive, treatment-resistant epilepsy-and record activity of putative excitatory neurons and parvalbumin-positive GABAergic neocortical interneurons (PV-INs) during naturalistic seizures induced by increased core body temperature. PV-IN activity was higher in Scn1a+/- relative to wild-type controls during quiet wakefulness. However, wild-type PV-INs showed progressive synchronization in response to temperature elevation that was absent in PV-INs from Scn1a+/- mice before seizure onset. Hence, impaired PV-IN synchronization may contribute to transition to seizure in Dravet syndrome.

Project description:Dravet syndrome (DS) is a neurodevelopmental genetic disorder caused by mutations in the SCN1A gene encoding the ? subunit of the NaV1.1 voltage-gated sodium channel that controls neuronal action potential firing. The high density of this mutated channel in GABAergic interneurons results in impaired inhibitory neurotransmission and subsequent excessive activation of excitatory neurons. The syndrome is associated with severe childhood epilepsy, autistic behaviors, and sudden unexpected death in epilepsy. Here, we compared the rescue effects of an adeno-associated viral (AAV) vector coding for the multifunctional ?1 sodium channel auxiliary subunit (AAV-NaV?1) with a control vector lacking a transgene. We hypothesized that overexpression of NaV?1 would facilitate the function of residual voltage-gated channels and improve the DS phenotype in the Scn1a+/- mouse model of DS. AAV-NaV?1 was injected into the cerebral spinal fluid of neonatal Scn1a+/- mice. In untreated control Scn1a+/- mice, females showed a higher degree of mortality than males. Compared with Scn1a+/- control mice, AAV-NaV?1-treated Scn1a+/- mice displayed increased survival, an outcome that was more pronounced in females than males. In contrast, behavioral analysis revealed that male, but not female, Scn1a+/- mice displayed motor hyperactivity, and abnormal performance on tests of fear and anxiety and learning and memory. Male Scn1a+/- mice treated with AAV-NaV?1 showed reduced spontaneous seizures and normalization of motor activity and performance on the elevated plus maze test. These findings demonstrate sex differences in mortality in untreated Scn1a+/- mice, an effect that may be related to a lower level of intrinsic inhibitory tone in female mice, and a normalization of aberrant behaviors in males after central nervous system administration of AAV-NaV?1. The therapeutic efficacy of AAV-NaV?1 in a mouse model of DS suggests a potential new long-lasting biological therapeutic avenue for the treatment of this catastrophic epilepsy.

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Gene expression profiling in a mouse model of Dravet syndrome.

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Gene expression profiling in a mouse model of Dravet syndrome.

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