Other search tools

About this data

The publication data currently available has been vetted by Vanderbilt faculty, staff, administrators and trainees. The data itself is retrieved directly from NCBI's PubMed and is automatically updated on a weekly basis to ensure accuracy and completeness.

If you have any questions or comments, please contact us.

Results: 1 to 10 of 56

Publication Record

Connections

The synthetic neuroactive steroid SGE-516 reduces seizure burden and improves survival in a Dravet syndrome mouse model.
Hawkins NA, Lewis M, Hammond RS, Doherty JJ, Kearney JA
(2017) Sci Rep 7: 15327
MeSH Terms: Animals, Anticonvulsants, Epilepsies, Myoclonic, GABA-A Receptor Agonists, Hydroxycholesterols, Mice, Mice, Mutant Strains, NAV1.1 Voltage-Gated Sodium Channel, Receptors, GABA-A
Show Abstract · Added October 2, 2018
Dravet syndrome is an infant-onset epileptic encephalopathy with multiple seizure types that are often refractory to conventional therapies. Treatment with standard benzodiazepines like clobazam, in combination with valproate and stiripentol, provides only modest seizure control. While benzodiazepines are a first-line therapy for Dravet syndrome, they are limited by their ability to only modulate synaptic receptors. Unlike benzodiazepines, neuroactive steroids potentiate a wider-range of GABA receptors. The synthetic neuroactive steroid SGE-516 is a potent positive allosteric modulator of both synaptic and extrasynaptic GABA receptors. Prior work demonstrated anticonvulsant activity of SGE-516 in acute seizure assays in rodents. In this study, we evaluated activity of SGE-516 on epilepsy phenotypes in the Scn1a mouse model that recapitulates many features of Dravet syndrome, including spontaneous seizures, premature death and seizures triggered by hyperthermia. To evaluate SGE-516 in Scn1a mice, we determined the effect of treatment on hyperthermia-induced seizures, spontaneous seizure frequency and survival. SGE-516 treatment protected against hyperthermia-induced seizures, reduced spontaneous seizure frequency and prolonged survival in the Scn1a mice. This provides the first evidence of SGE-516 activity in a mouse model of Dravet syndrome, and supports further investigation of neuroactive steroids as potential anticonvulsant compounds for refractory epilepsies.
1 Communities
0 Members
0 Resources
9 MeSH Terms
Overexpressing wild-type γ2 subunits rescued the seizure phenotype in Gabrg2 Dravet syndrome mice.
Huang X, Zhou C, Tian M, Kang JQ, Shen W, Verdier K, Pimenta A, MacDonald RL
(2017) Epilepsia 58: 1451-1461
MeSH Terms: Action Potentials, Animals, Convulsants, Electric Stimulation, Epilepsies, Myoclonic, Humans, In Vitro Techniques, Inhibitory Postsynaptic Potentials, Male, Mice, Mice, Inbred C57BL, Mice, Transgenic, Mutation, Neural Pathways, Patch-Clamp Techniques, Pentylenetetrazole, Protein Subunits, Pyramidal Cells, Receptors, GABA-A, Somatosensory Cortex, Thalamus
Show Abstract · Added June 21, 2017
OBJECTIVE - The mutant γ-aminobutyric acid type A (GABA ) receptor γ2(Q390X) subunit (Q351X in the mature peptide) has been associated with the epileptic encephalopathy, Dravet syndrome, and the epilepsy syndrome genetic epilepsy with febrile seizures plus (GEFS+). The mutation generates a premature stop codon that results in translation of a stable truncated and misfolded γ2 subunit that accumulates in neurons, forms intracellular aggregates, disrupts incorporation of γ2 subunits into GABA receptors, and affects trafficking of partnering α and β subunits. Heterozygous Gabrg2 knock-in (KI) mice had reduced cortical inhibition, spike wave discharges on electroencephalography (EEG), a lower seizure threshold to the convulsant drug pentylenetetrazol (PTZ), and spontaneous generalized tonic-clonic seizures. In this proof-of-principal study, we attempted to rescue these deficits in KI mice using a γ2 subunit gene (GABRG2) replacement therapy.
METHODS - We introduced the GABRG2 allele by crossing Gabrg2 KI mice with bacterial artificial chromosome (BAC) transgenic mice overexpressing HA (hemagglutinin)-tagged human γ2 subunits, and compared GABA receptor subunit expression by Western blot and immunohistochemical staining, seizure threshold by monitoring mouse behavior after PTZ-injection, and thalamocortical inhibition and network oscillation by slice recording.
RESULTS - Compared to KI mice, adult mice carrying both mutant allele and transgene had increased wild-type γ2 and partnering α1 and β2/3 subunits, increased miniature inhibitory postsynaptic current (mIPSC) amplitudes recorded from layer VI cortical neurons, reduced thalamocortical network oscillations, and higher PTZ seizure threshold.
SIGNIFICANCE - Based on these results we suggest that seizures in a genetic epilepsy syndrome caused by epilepsy mutant γ2(Q390X) subunits with dominant negative effects could be rescued potentially by overexpression of wild-type γ2 subunits.
Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.
1 Communities
0 Members
0 Resources
21 MeSH Terms
Altered Channel Conductance States and Gating of GABA Receptors by a Pore Mutation Linked to Dravet Syndrome.
Hernandez CC, Kong W, Hu N, Zhang Y, Shen W, Jackson L, Liu X, Jiang Y, Macdonald RL
(2017) eNeuro 4:
MeSH Terms: Animals, Cell Membrane, Cerebral Cortex, Epilepsies, Myoclonic, HEK293 Cells, Humans, Inhibitory Postsynaptic Potentials, Mice, Inbred C57BL, Miniature Postsynaptic Potentials, Models, Molecular, Mutation, Missense, Neurons, Receptors, GABA-A, Recombinant Proteins, Zinc
Show Abstract · Added April 6, 2017
We identified a missense mutation, P302L, in the γ-aminobutyric acid type A (GABA) receptor γ2 subunit gene in a patient with Dravet syndrome using targeted next-generation sequencing. The mutation was in the cytoplasmic portion of the transmembrane segment M2 of the γ2 subunit that faces the pore lumen. GABA receptor α1 and β3 subunits were coexpressed with wild-type (wt) γ2L or mutant γ2L(P302L) subunits in HEK 293T cells and cultured mouse cortical neurons. We measured currents using whole-cell and single-channel patch clamp techniques, surface and total expression levels using surface biotinylation and Western blotting, and potential structural perturbations in mutant GABA receptors using structural modeling. The γ2(P302L) subunit mutation produced an ∼90% reduction of whole-cell current by increasing macroscopic desensitization and reducing GABA potency, which resulted in a profound reduction of GABA receptor-mediated miniature IPSCs (mIPSCs). The conductance of the receptor channel was reduced to 24% of control conductance by shifting the relative contribution of the conductance states from high- to low-conductance levels with only slight changes in receptor surface expression. Structural modeling of the GABA receptor in the closed, open, and desensitized states showed that the mutation was positioned to slow activation, enhance desensitization, and shift channels to a low-conductance state by reshaping the hour-glass-like pore cavity during transitions between closed, open, and desensitized states. Our study revealed a novel γ2 subunit missense mutation (P302L) that has a novel pathogenic mechanism to cause defects in the conductance and gating of GABA receptors, which results in hyperexcitability and contributes to the pathogenesis of the genetic epilepsy Dravet syndrome.
0 Communities
1 Members
0 Resources
15 MeSH Terms
Fine Mapping of a Dravet Syndrome Modifier Locus on Mouse Chromosome 5 and Candidate Gene Analysis by RNA-Seq.
Hawkins NA, Zachwieja NJ, Miller AR, Anderson LL, Kearney JA
(2016) PLoS Genet 12: e1006398
MeSH Terms: Animals, Benzodiazepines, Chromosome Mapping, Chromosomes, Clobazam, Disease Models, Animal, Epilepsies, Myoclonic, Epilepsy, Gene Expression Regulation, Genes, Modifier, Genetic Association Studies, High-Throughput Nucleotide Sequencing, Humans, Mice, Mice, Knockout, Mutation, NAV1.1 Voltage-Gated Sodium Channel, Phenotype, Receptors, GABA-A, Seizures
Show Abstract · Added October 2, 2018
A substantial number of mutations have been identified in voltage-gated sodium channel genes that result in various forms of human epilepsy. SCN1A mutations result in a spectrum of severity ranging from mild febrile seizures to Dravet syndrome, an infant-onset epileptic encephalopathy. Dravet syndrome patients experience multiple seizures types that are often refractory to treatment, developmental delays, and elevated risk for SUDEP. The same sodium channel mutation can produce epilepsy phenotypes of varying clinical severity. This suggests that other factors, including genetic, modify the primary mutation and change disease severity. Mouse models provide a useful tool in studying the genetic basis of epilepsy. The mouse strain background can alter phenotype severity, supporting a contribution of genetic modifiers in epilepsy. The Scn1a+/- mouse model has a strain-dependent epilepsy phenotype. Scn1a+/- mice on the 129S6/SvEvTac (129) strain have a normal phenotype and lifespan, while [129xC57BL/6J]F1-Scn1a+/- mice experience spontaneous seizures, hyperthermia-induced seizures and high rates of premature death. We hypothesize the phenotypic differences are due to strain-specific genetic modifiers that influence expressivity of the Scn1a+/- phenotype. Low resolution mapping of Scn1a+/- identified several Dravet syndrome modifier (Dsm) loci responsible for the strain-dependent difference in survival. One locus of interest, Dsm1 located on chromosome 5, was fine mapped to a 9 Mb region using interval specific congenics. RNA-Seq was then utilized to identify candidate modifier genes within this narrowed region. Three genes with significant total gene expression differences between 129S6/SvEvTac and [129xC57BL/6J]F1 were identified, including the GABAA receptor subunit, Gabra2. Further analysis of Gabra2 demonstrated allele-specific expression. Pharmological manipulation by clobazam, a common anticonvulsant with preferential affinity for the GABRA2 receptor, revealed dose-dependent protection against hyperthermia-induced seizures in Scn1a+/- mice. These findings support Gabra2 as a genetic modifier of the Scn1a+/- mouse model of Dravet syndrome.
1 Communities
0 Members
0 Resources
20 MeSH Terms
Effects of Antecedent GABA A Receptor Activation on Counterregulatory Responses to Exercise in Healthy Man.
Hedrington MS, Tate DB, Younk LM, Davis SN
(2015) Diabetes 64: 3253-61
MeSH Terms: Adult, Alprazolam, Autonomic Nervous System, Bicycling, Blood Glucose, Epinephrine, Exercise, Female, GABA-A Receptor Agonists, Glucagon, Glucose Clamp Technique, Human Growth Hormone, Humans, Hydrocortisone, Lipolysis, Male, Norepinephrine, Pituitary-Adrenal System, Receptors, GABA-A
Show Abstract · Added July 30, 2015
The aim of this study was to determine whether antecedent stimulation of γ-aminobutyric acid (GABA) A receptors with the benzodiazepine alprazolam can blunt physiologic responses during next-day moderate (90 min) exercise in healthy man. Thirty-one healthy individuals (16 male/15 female aged 28 ± 1 year, BMI 23 ± 3 kg/m(2)) were studied during separate, 2-day protocols. Day 1 consisted of morning and afternoon 2-h hyperinsulinemic-euglycemic or hypoglycemic clamps with or without 1 mg alprazolam given 30 min before a clamp. Day 2 consisted of 90-min euglycemic cycling exercise at 50% VO2max. Despite similar euglycemia (5.3 ± 0.1 mmol/L) and insulinemia (46 ± 6 pmol/L) during day 2 exercise studies, GABA A activation with alprazolam during day 1 euglycemia resulted in significant blunting of plasma epinephrine, norepinephrine, glucagon, cortisol, and growth hormone responses. Lipolysis (glycerol, nonesterified fatty acids) and endogenous glucose production during exercise were also reduced, and glucose infusion rates were increased following prior euglycemia with alprazolam. Prior hypoglycemia with alprazolam resulted in further reduction of glucagon and cortisol responses during exercise. We conclude that prior activation of GABA A pathways can play a significant role in blunting key autonomous nervous system, neuroendocrine, and metabolic physiologic responses during next-day exercise in healthy man.
© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
0 Communities
0 Members
2 Resources
19 MeSH Terms
Altered intrathalamic GABAA neurotransmission in a mouse model of a human genetic absence epilepsy syndrome.
Zhou C, Ding L, Deel ME, Ferrick EA, Emeson RB, Gallagher MJ
(2015) Neurobiol Dis 73: 407-17
MeSH Terms: Animals, Blotting, Western, Disease Models, Animal, Epilepsy, Absence, Inhibitory Postsynaptic Potentials, Mice, Mice, Inbred C57BL, Mice, Knockout, Microscopy, Confocal, RNA Editing, Receptors, GABA-A, Synaptic Transmission, Thalamic Nuclei
Show Abstract · Added January 20, 2015
We previously demonstrated that heterozygous deletion of Gabra1, the mouse homolog of the human absence epilepsy gene that encodes the GABAA receptor (GABAAR) α1 subunit, causes absence seizures. We showed that cortex partially compensates for this deletion by increasing the cell surface expression of residual α1 subunit and by increasing α3 subunit expression. Absence seizures also involve two thalamic nuclei: the ventrobasal (VB) nucleus, which expresses only the α1 and α4 subtypes of GABAAR α subunits, and the reticular (nRT) nucleus, which expresses only the α3 subunit subtype. Here, we found that, unlike cortex, VB exhibited significantly reduced total and synaptic α1 subunit expression. In addition, heterozygous α1 subunit deletion substantially reduced miniature inhibitory postsynaptic current (mIPSC) peak amplitudes and frequency in VB. However, there was no change in the expression of the extrasynaptic α4 or δ subunits in VB and, unlike other models of absence epilepsy, no change in tonic GABAAR currents. Although heterozygous α1 subunit knockout increased α3 subunit expression in medial thalamic nuclei, it did not alter α3 subunit expression in nRT. However, it did enlarge the presynaptic vesicular inhibitory amino acid transporter puncta and lengthen the time constant of mIPSC decay in nRT. We conclude that increased tonic GABAA currents are not necessary for absence seizures. In addition, heterozygous loss of α1 subunit disinhibits VB by substantially reducing phasic GABAergic currents and surprisingly, it also increases nRT inhibition by prolonging phasic currents. The increased inhibition in nRT likely represents a partial compensation that helps reduce absence seizures.
Copyright © 2015 Elsevier Inc. All rights reserved.
0 Communities
1 Members
0 Resources
13 MeSH Terms
GABAA receptor biogenesis is impaired by the γ2 subunit febrile seizure-associated mutation, GABRG2(R177G).
Todd E, Gurba KN, Botzolakis EJ, Stanic AK, Macdonald RL
(2014) Neurobiol Dis 69: 215-24
MeSH Terms: Cell Membrane, Conserved Sequence, Cycloheximide, Endoplasmic Reticulum, Endoplasmic Reticulum-Associated Degradation, Glycosylation, HEK293 Cells, Humans, Models, Molecular, Mutation, Missense, Patch-Clamp Techniques, Protein Structure, Secondary, Protein Structure, Tertiary, Protein Synthesis Inhibitors, Protein Transport, Receptors, GABA-A, Seizures, Febrile, gamma-Aminobutyric Acid
Show Abstract · Added January 24, 2015
A missense mutation in the GABAA receptor γ2L subunit, R177G, was reported in a family with complex febrile seizures (FS). To gain insight into the mechanistic basis for these genetic seizures, we explored how the R177G mutation altered the properties of recombinant α1β2γ2L GABAA receptors expressed in HEK293T cells. Using a combination of electrophysiology, flow cytometry, and immunoblotting, we found that the R177G mutation decreased GABA-evoked whole-cell current amplitudes by decreasing cell surface expression of α1β2γ2L receptors. This loss of receptor surface expression resulted from endoplasmic reticulum (ER) retention of mutant γ2L(R177G) subunits, which unlike wild-type γ2L subunits, were degraded by ER-associated degradation (ERAD). Interestingly, when compared to the condition of homozygous γ2L(R177G) subunit expression, disproportionately low levels of γ2L(R177G) subunits reached the cell surface with heterozygous expression, indicating that wild-type γ2L subunits possessed a competitive advantage over mutant γ2L(R177G) subunits for receptor assembly and/or forward trafficking. Inhibiting protein synthesis with cycloheximide demonstrated that the R177G mutation primarily decreased the stability of an intracellular pool of unassembled γ2L subunits, suggesting that the mutant γ2L(R177G) subunits competed poorly with wild-type γ2L subunits due to impaired subunit folding and/or oligomerization. Molecular modeling confirmed that the R177G mutation could disrupt intrasubunit salt bridges, thereby destabilizing secondary and tertiary structure of γ2L(R177G) subunits. These findings support an emerging body of literature implicating defects in GABAA receptor biogenesis in the pathogenesis of genetic epilepsies (GEs) and FS.
Copyright © 2014. Published by Elsevier Inc.
0 Communities
1 Members
0 Resources
18 MeSH Terms
Preclinical imaging evaluation of novel TSPO-PET ligand 2-(5,7-Diethyl-2-(4-(2-[(18)F]fluoroethoxy)phenyl)pyrazolo[1,5-a]pyrimidin-3-yl)-N,N-diethylacetamide ([ (18)F]VUIIS1008) in glioma.
Tang D, Nickels ML, Tantawy MN, Buck JR, Manning HC
(2014) Mol Imaging Biol 16: 813-20
MeSH Terms: Animals, Brain Neoplasms, Carrier Proteins, Fluorine Radioisotopes, Glioma, Ligands, Mice, Mice, Inbred C57BL, Positron-Emission Tomography, Pyrazoles, Pyrimidines, Rats, Rats, Wistar, Receptors, GABA, Receptors, GABA-A
Show Abstract · Added January 23, 2015
PURPOSE - Translocator protein (TSPO) concentrations are elevated in glioma, suggesting a role for TSPO positron emission tomography (PET) imaging in this setting. In preclinical PET studies, we evaluated a novel, high-affinity TSPO PET ligand, [(18)F]VUIIS1008, in healthy mice and glioma-bearing rats.
PROCEDURES - Dynamic PET data were acquired simultaneously with [(18)F]VUIIS1008 injection, with binding reversibility and specificity evaluated in vivo by non-radioactive ligand displacement or blocking. Compartmental analysis of PET data was performed using metabolite-corrected arterial input functions. Imaging was validated with histology and immunohistochemistry.
RESULTS - [(18)F]VUIIS1008 exhibited rapid uptake in TSPO-rich organs. PET ligand uptake was displaceable with non-radioactive VUIIS1008 or PBR06 in mice. Tumor accumulation of [(18)F]VUIIS1008 was blocked by pretreatment with VUIIS1008 in rats. [(18)F]VUIIS1008 exhibited improved tumor-to-background ratio and higher binding potential in tumors compared to a structurally similar pyrazolopyrimidine TSPO ligand, [(18)F]DPA-714.
CONCLUSIONS - The PET ligand [(18)F]VUIIS1008 exhibits promising characteristics as a tracer for imaging glioma. Further translational studies appear warranted.
0 Communities
2 Members
0 Resources
15 MeSH Terms
Three epilepsy-associated GABRG2 missense mutations at the γ+/β- interface disrupt GABAA receptor assembly and trafficking by similar mechanisms but to different extents.
Huang X, Hernandez CC, Hu N, Macdonald RL
(2014) Neurobiol Dis 68: 167-79
MeSH Terms: Adenosine Triphosphatases, Animals, Cells, Cultured, Cerebral Cortex, Computer Simulation, Embryo, Mammalian, Gene Expression Regulation, HEK293 Cells, Humans, Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase, Membrane Potentials, Models, Molecular, Mutation, Missense, Protein Subunits, Protein Transport, Rats, Receptors, GABA-A, Temperature
Show Abstract · Added January 24, 2015
We compared the effects of three missense mutations in the GABAA receptor γ2 subunit on GABAA receptor assembly, trafficking and function in HEK293T cells cotransfected with α1, β2, and wildtype or mutant γ2 subunits. The mutations R82Q and P83S were identified in families with genetic epilepsy with febrile seizures plus (GEFS+), and N79S was found in a single patient with generalized tonic-clonic seizures (GTCS). Although all three mutations were located in an N-terminal loop that contributes to the γ+/β- subunit-subunit interface, we found that each mutation impaired GABAA receptor assembly to a different extent. The γ2(R82Q) and γ2(P83S) subunits had reduced α1β2γ2 receptor surface expression due to impaired assembly into pentamers, endoplasmic reticulum (ER) retention and degradation. In contrast, γ2(N79S) subunits were efficiently assembled into GABAA receptors with only minimally altered receptor trafficking, suggesting that N79S was a rare or susceptibility variant rather than an epilepsy mutation. Increased structural variability at assembly motifs was predicted by R82Q and P83S, but not N79S, substitution, suggesting that R82Q and P83S substitutions were less tolerated. Membrane proteins with missense mutations that impair folding and assembly often can be "rescued" by decreased temperatures. We coexpressed wildtype or mutant γ2 subunits with α1 and β2 subunits and found increased surface and total levels of both wildtype and mutant γ2 subunits after decreasing the incubation temperature to 30°C for 24h, suggesting that lower temperatures increased GABAA receptor stability. Thus epilepsy-associated mutations N79S, R82Q and P83S disrupted GABAA receptor assembly to different extents, an effect that could be potentially rescued by facilitating protein folding and assembly.
Copyright © 2014 Elsevier Inc. All rights reserved.
0 Communities
1 Members
0 Resources
18 MeSH Terms
A novel GABRG2 mutation, p.R136*, in a family with GEFS+ and extended phenotypes.
Johnston AJ, Kang JQ, Shen W, Pickrell WO, Cushion TD, Davies JS, Baer K, Mullins JGL, Hammond CL, Chung SK, Thomas RH, White C, Smith PEM, Macdonald RL, Rees MI
(2014) Neurobiol Dis 64: 131-141
MeSH Terms: Adult, Animals, COS Cells, Cells, Cultured, Cercopithecus aethiops, Cerebral Cortex, Child, Child, Preschool, Cohort Studies, Epilepsy, Generalized, Family, Female, HEK293 Cells, Humans, Infant, Male, Neurons, PC12 Cells, Phenotype, Point Mutation, Rats, Receptors, GABA-A, Seizures, Febrile
Show Abstract · Added January 24, 2015
Genetic mutations in voltage-gated and ligand-gated ion channel genes have been identified in a small number of Mendelian families with genetic generalised epilepsies (GGEs). They are commonly associated with febrile seizures (FS), childhood absence epilepsy (CAE) and particularly with generalised or genetic epilepsy with febrile seizures plus (GEFS+). In clinical practice, despite efforts to categorise epilepsy and epilepsy families into syndromic diagnoses, many generalised epilepsies remain unclassified with a presumed genetic basis. During the systematic collection of epilepsy families, we assembled a cohort of families with evidence of GEFS+ and screened for variations in the γ2 subunit of the γ-aminobutyric acid (GABA) type A receptor gene (GABRG2). We detected a novel GABRG2(p.R136*) premature translation termination codon in one index-case from a two-generation nuclear family, presenting with an unclassified GGE, a borderline GEFS+ phenotype with learning difficulties and extended behavioural presentation. The GABRG2(p.R136*) mutation segregates with the febrile seizure component of this family's GGE and is absent in 190 healthy control samples. In vitro expression assays demonstrated that γ2(p.R136*) subunits were produced, but had reduced cell-surface and total expression. When γ2(p.R136*) subunits were co-expressed with α1 and β2 subunits in HEK 293T cells, GABA-evoked currents were reduced. Furthermore, γ2(p.R136*) subunits were highly-expressed in intracellular aggregations surrounding the nucleus and endoplasmic reticulum (ER), suggesting compromised receptor trafficking. A novel GABRG2(p.R136*) mutation extends the spectrum of GABRG2 mutations identified in GEFS+ and GGE phenotypes, causes GABAA receptor dysfunction, and represents a putative epilepsy mechanism.
Copyright © 2014 Elsevier Inc. All rights reserved.
0 Communities
1 Members
0 Resources
23 MeSH Terms