Assembly mechanism of Integrator's RNA cleavage module.

The modular Integrator complex is a transcription regulator that is essential for embryonic development. It attenuates coding gene expression via premature transcription termination and performs 3'-processing of non-coding RNAs. For both activities, Integrator requires endonuclease activity that is harbored by an RNA cleavage module consisting of INTS4-9-11. How correct assembly of Integrator modules is achieved remains unknown. Here, we show that BRAT1 and WDR73 are critical biogenesis factors for the human cleavage module. They maintain INTS9-11 inactive during maturation by physically blocking the endonuclease active site and prevent premature INTS4 association. Furthermore, BRAT1 facilitates import of INTS9-11 into the nucleus, where it is joined by INTS4. Final BRAT1 release requires locking of the mature cleavage module conformation by inositol hexaphosphate (IP6). Our data explain several neurodevelopmental disorders caused by BRAT1, WDR73, and INTS11 mutations as Integrator assembly defects and reveal that IP6 is an essential co-factor for cleavage module maturation.

Disruption of the IL-33-ST2-AKT signaling axis impairs neurodevelopment by inhibiting microglial metabolic adaptation and phagocytic function.

To accommodate the changing needs of the developing brain, microglia must undergo substantial morphological, phenotypic, and functional reprogramming. Here, we examined whether cellular metabolism regulates microglial function during neurodevelopment. Microglial mitochondria bioenergetics correlated with and were functionally coupled to phagocytic activity in the developing brain. Transcriptional profiling of microglia with diverse metabolic profiles revealed an activation signature wherein the interleukin (IL)-33 signaling axis is associated with phagocytic activity. Genetic perturbation of IL-33 or its receptor ST2 led to microglial dystrophy, impaired synaptic function, and behavioral abnormalities. Conditional deletion of Il33 from astrocytes or Il1rl1, encoding ST2, in microglia increased susceptibility to seizures. Mechanistically, IL-33 promoted mitochondrial activity and phagocytosis in an AKT-dependent manner. Mitochondrial metabolism and AKT activity were temporally regulated in vivo. Thus, a microglia-astrocyte circuit mediated by the IL-33-ST2-AKT signaling axis supports microglial metabolic adaptation and phagocytic function during early development, with implications for neurodevelopmental and neuropsychiatric disorders.

Preictal dysfunctions of inhibitory interneurons paradoxically lead to their rebound hyperactivity and to low-voltage-fast onset seizures in Dravet syndrome.

Epilepsies have numerous specific mechanisms. The understanding of neural dynamics leading to seizures is important for disclosing pathological mechanisms and developing therapeutic approaches. We investigated electrographic activities and neural dynamics leading to convulsive seizures in patients and mouse models of Dravet syndrome (DS), a developmental and epileptic encephalopathy in which hypoexcitability of GABAergic neurons is considered to be the main dysfunction. We analyzed EEGs from DS patients carrying a SCN1A pathogenic variant, as well as epidural electrocorticograms, hippocampal local field potentials, and hippocampal single-unit neuronal activities in Scn1a+/- and Scn1aRH/+ DS mice. Strikingly, most seizures had low-voltage-fast onset in both patients and mice, which is thought to be generated by hyperactivity of GABAergic interneurons, the opposite of the main pathological mechanism of DS. Analyzing single-unit recordings, we observed that temporal disorganization of the firing of putative interneurons in the period immediately before the seizure (preictal) precedes the increase of their activity at seizure onset, together with the entire neuronal network. Moreover, we found early signatures of the preictal period in the spectral features of hippocampal and cortical field potential of Scn1a mice and of patients' EEG, which are consistent with the dysfunctions that we observed in single neurons and that allowed seizure prediction. Therefore, the perturbed preictal activity of interneurons leads to their hyperactivity at the onset of generalized seizures, which have low-voltage-fast features that are similar to those observed in other epilepsies and are triggered by hyperactivity of GABAergic neurons. Preictal spectral features may be used as predictive seizure biomarkers.

Attenuating midline thalamus bursting to mitigate absence epilepsy.

Advancing the mechanistic understanding of absence epilepsy is crucial for developing new therapeutics, especially for patients unresponsive to current treatments. Utilizing a recently developed mouse model of absence epilepsy carrying the BK gain-of-function channelopathy D434G, here we report that attenuating the burst firing of midline thalamus (MLT) neurons effectively prevents absence seizures. We found that enhanced BK channel activity in the BK-D434G MLT neurons promotes synchronized bursting during the ictal phase of absence seizures. Modulating MLT neurons through pharmacological reagents, optogenetic stimulation, or deep brain stimulation effectively attenuates burst firing, leading to reduced absence seizure frequency and increased vigilance. Additionally, enhancing vigilance by amphetamine, a stimulant medication, or physical perturbation also effectively suppresses MLT bursting and prevents absence seizures. These findings suggest that the MLT is a promising target for clinical interventions. Our diverse approaches offer valuable insights for developing next generation therapeutics to treat absence epilepsy.

Mosaicism-independent mechanisms contribute to Pcdh19-related epilepsy and repetitive behaviors in Xenopus.

Protocadherin19 (PCDH19)-related epilepsy syndrome is a rare disorder characterized by early-onset epilepsy, intellectual disability, and autistic behaviors. PCDH19 is located on the X chromosome and encodes a calcium-dependent single-pass transmembrane protein, which regulates cell-to-cell adhesion through homophilic binding. In human, 90% of heterozygous females, containing PCDH19 wild-type and mutant cells due to random X inactivation, are affected, whereas mutant males, containing only mutant cells, are typically not. The current view, the cellular interference, is that the altered interactions between wild-type and mutant cells during development, rather than loss of function itself, are responsible. However, studies using Pcdh19 knockout mice showed that the complete loss of function also causes autism-like behaviors both in males and females, suggesting that other functions of PCDH19 may also contribute to pathogenesis. To address whether mosaicism is required for PCDH19-related epilepsy, we generated Xenopus tropicalis tadpoles with complete or mosaic loss of function by injecting antisense morpholino oligonucleotides into the blastomeres of neural lineage at different stages of development. We found that either mosaic or complete knockdown results in seizure-like behaviors, which could be rescued by antiseizure medication, and repetitive behaviors. Our results suggest that the loss of PCDH19 function itself, in addition to cellular interference, may also contribute to PCDH19-related epilepsy.

Hyperfunction of post-synaptic density protein 95 promotes seizure response in early-stage aß pathology.

Accumulation of amyloid-beta (Aß) can lead to the formation of aggregates that contribute to neurodegeneration in Alzheimer's disease (AD). Despite globally reduced neural activity during AD onset, recent studies have suggested that Aß induces hyperexcitability and seizure-like activity during the early stages of the disease that ultimately exacerbate cognitive decline. However, the underlying mechanism is unknown. Here, we reveal an Aß-induced elevation of postsynaptic density protein 95 (PSD-95) in cultured neurons in vitro and in an in vivo AD model using APP/PS1 mice at 8 weeks of age. Elevation of PSD-95 occurs as a result of reduced ubiquitination caused by Akt-dependent phosphorylation of E3 ubiquitin ligase murine-double-minute 2 (Mdm2). The elevation of PSD-95 is consistent with the facilitation of excitatory synapses and the surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors induced by Aß. Inhibition of PSD-95 corrects these Aß-induced synaptic defects and reduces seizure activity in APP/PS1 mice. Our results demonstrate a mechanism underlying elevated seizure activity during early-stage Aß pathology and suggest that PSD-95 could be an early biomarker and novel therapeutic target for AD.

The Derlin-1-Stat5b axis maintains homeostasis of adult hippocampal neurogenesis.

Adult neural stem cells (NSCs) in the hippocampal dentate gyrus continuously proliferate and generate new neurons throughout life. Although various functions of organelles are closely related to the regulation of adult neurogenesis, the role of endoplasmic reticulum (ER)-related molecules in this process remains largely unexplored. Here we show that Derlin-1, an ER-associated degradation component, spatiotemporally maintains adult hippocampal neurogenesis through a mechanism distinct from its established role as an ER quality controller. Derlin-1 deficiency in the mouse central nervous system leads to the ectopic localization of newborn neurons and impairs NSC transition from active to quiescent states, resulting in early depletion of hippocampal NSCs. As a result, Derlin-1-deficient mice exhibit phenotypes of increased seizure susceptibility and cognitive dysfunction. Reduced Stat5b expression is responsible for adult neurogenesis defects in Derlin-1-deficient NSCs. Inhibition of histone deacetylase activity effectively induces Stat5b expression and restores abnormal adult neurogenesis, resulting in improved seizure susceptibility and cognitive dysfunction in Derlin-1-deficient mice. Our findings indicate that the Derlin-1-Stat5b axis is indispensable for the homeostasis of adult hippocampal neurogenesis.

The Evf2 Ultraconserved Enhancer lncRNA Functionally and Spatially Organizes Megabase Distant Genes in the Developing Forebrain.

Gene regulation requires selective targeting of DNA regulatory enhancers over megabase distances. Here we show that Evf2, a cloud-forming Dlx5/6 ultraconserved enhancer (UCE) lncRNA, simultaneously localizes to activated (Umad1, 1.6 Mb distant) and repressed (Akr1b8, 27 Mb distant) chr6 target genes, precisely regulating UCE-gene distances and cohesin binding in mouse embryonic forebrain GABAergic interneurons (INs). Transgene expression of Evf2 activates Lsm8 (12 Mb distant) but fails to repress Akr1b8, supporting trans activation and long-range cis repression. Through both short-range (Dlx6 antisense) and long-range (Akr1b8) repression, the Evf2-5'UCE links homeodomain and mevalonate pathway-regulated enhancers to IN diversity. The Evf2-3' end is required for long-range activation but dispensable for RNA cloud localization, functionally dividing the RNA into 3'-activator and 5'UCE repressor and targeting regions. Together, these results support that Evf2 selectively regulates UCE interactions with multi-megabase distant genes through complex effects on chromosome topology, linking lncRNA-dependent topological and transcriptional control with interneuron diversity and seizure susceptibility.

A Dual Effect of Dopamine on Hippocampal LTP and Cognitive Functions in Control and Kindled Mice.

The impact of dopamine on synaptic plasticity and cognitive function following seizure is not well understood. Here, using optogenetics in the freely behaving animal, we examined exploratory behavior and short-term memory in control and kindled male mice during tonic stimulation of dopaminergic neurons within the ventral tegmental area (VTA). Furthermore, using field potential recording, we compared the effect of dopamine on synaptic plasticity in stratum radiatum and stratum oriens layers of both ventral and dorsal hippocampal CA1 regions, and again in both control and kindled male mice. Our results demonstrate that tonic stimulation of VTA dopaminergic neurons enhances novelty-driven exploration and short-term spatial memory in kindled mice, essentially rescuing the seizure-induced cognitive impairment. In addition, we found that dopamine has a dual effect on LTP in control versus kindled mice, such that application of dopamine prevented LTP induction in slices from control mice, but rescued LTP in slices taken from the kindled animal. Taken together, our results highlight the potential for dopaminergic modulation in improving synaptic plasticity and cognitive function following seizure.

Nacc1 Mutation in Mice Models Rare Neurodevelopmental Disorder with Underlying Synaptic Dysfunction.

A missense mutation in the transcription repressor Nucleus accumbens-associated 1 (NACC1) gene at c.892C>T (p.Arg298Trp) on chromosome 19 causes severe neurodevelopmental delay ( Schoch et al., 2017). To model this disorder, we engineered the first mouse model with the homologous mutation (Nacc1+/R284W ) and examined mice from E17.5 to 8 months. Both genders had delayed weight gain, epileptiform discharges and altered power spectral distribution in cortical electroencephalogram, behavioral seizures, and marked hindlimb clasping; females displayed thigmotaxis in an open field. In the cortex, NACC1 long isoform, which harbors the mutation, increased from 3 to 6 months, whereas the short isoform, which is not present in humans and lacks aaR284 in mice, rose steadily from postnatal day (P) 7. Nuclear NACC1 immunoreactivity increased in cortical pyramidal neurons and parvalbumin containing interneurons but not in nuclei of astrocytes or oligodendroglia. Glial fibrillary acidic protein staining in astrocytic processes was diminished. RNA-seq of P14 mutant mice cortex revealed over 1,000 differentially expressed genes (DEGs). Glial transcripts were downregulated and synaptic genes upregulated. Top gene ontology terms from upregulated DEGs relate to postsynapse and ion channel function, while downregulated DEGs enriched for terms relating to metabolic function, mitochondria, and ribosomes. Levels of synaptic proteins were changed, but number and length of synaptic contacts were unaltered at 3 months. Homozygosity worsened some phenotypes including postnatal survival, weight gain delay, and increase in nuclear NACC1. This mouse model simulates a rare form of autism and will be indispensable for assessing pathophysiology and targets for therapeutic intervention.

De novo variants in ATP2B1 lead to neurodevelopmental delay.

Calcium (Ca2+) is a universal second messenger involved in synaptogenesis and cell survival; consequently, its regulation is important for neurons. ATPase plasma membrane Ca2+ transporting 1 (ATP2B1) belongs to the family of ATP-driven calmodulin-dependent Ca2+ pumps that participate in the regulation of intracellular free Ca2+. Here, we clinically describe a cohort of 12 unrelated individuals with variants in ATP2B1 and an overlapping phenotype of mild to moderate global development delay. Additional common symptoms include autism, seizures, and distal limb abnormalities. Nine probands harbor missense variants, seven of which were in specific functional domains, and three individuals have nonsense variants. 3D structural protein modeling suggested that the variants have a destabilizing effect on the protein. We performed Ca2+ imaging after introducing all nine missense variants in transfected HEK293 cells and showed that all variants lead to a significant decrease in Ca2+ export capacity compared with the wild-type construct, thus proving their pathogenicity. Furthermore, we observed for the same variant set an incorrect intracellular localization of ATP2B1. The genetic findings and the overlapping phenotype of the probands as well as the functional analyses imply that de novo variants in ATP2B1 lead to a monogenic form of neurodevelopmental disorder.

Catastrophic Epilepsies of Childhood.

The tragedy of epilepsy emerges from the combination of its high prevalence, impact upon sufferers and their families, and unpredictability. Childhood epilepsies are frequently severe, presenting in infancy with pharmaco-resistant seizures; are often accompanied by debilitating neuropsychiatric and systemic comorbidities; and carry a grave risk of mortality. Here, we review the most current basic science and translational research findings on several of the most catastrophic forms of pediatric epilepsy. We focus largely on genetic epilepsies and the research that is discovering the mechanisms linking disease genes to epilepsy syndromes. We also describe the strides made toward developing novel pharmacological and interventional treatment strategies to treat these disorders. The research reviewed provides hope for a complete understanding of, and eventual cure for, these childhood epilepsy syndromes.

Threshold of somatic mosaicism leading to brain dysfunction with focal epilepsy.

Somatic mosaicism in a fraction of brain cells causes neurodevelopmental disorders, including childhood intractable epilepsy. However, the threshold for somatic mosaicism leading to brain dysfunction is unknown. In this study, we induced various mosaic burdens in focal cortical dysplasia type II (FCD II) mice, featuring mTOR somatic mosaicism and spontaneous behavioural seizures. The mosaic burdens ranged from approximately 1000 to 40 000 neurons expressing the mTOR mutant in the somatosensory or medial prefrontal cortex. Surprisingly, approximately 8000-9000 neurons expressing the MTOR mutant, extrapolated to constitute 0.08%-0.09% of total cells or roughly 0.04% of variant allele frequency in the mouse hemicortex, were sufficient to trigger epileptic seizures. The mutational burden was correlated with seizure frequency and onset, with a higher tendency for electrographic inter-ictal spikes and beta- and gamma-frequency oscillations in FCD II mice exceeding the threshold. Moreover, mutation-negative FCD II patients in deep sequencing of their bulky brain tissues revealed somatic mosaicism of the mTOR pathway genes as low as 0.07% in resected brain tissues through ultra-deep targeted sequencing (up to 20 million reads). Thus, our study suggests that extremely low levels of somatic mosaicism can contribute to brain dysfunction.

Explaining slow seizure propagation with white matter tractography.

Epileptic seizures recorded with stereo-EEG can take a fraction of a second or several seconds to propagate from one region to another. What explains such propagation patterns? We combine tractography and stereo-EEG to determine the relationship between seizure propagation and the white matter architecture and to describe seizure propagation mechanisms. Patient-specific spatiotemporal seizure propagation maps were combined with tractography from diffusion imaging of matched subjects from the Human Connectome Project. The onset of seizure activity was marked on a channel-by-channel basis by two board-certified neurologists for all channels involved in the seizure. We measured the tract connectivity (number of tracts) between regions-of-interest pairs among the seizure onset zone, regions of seizure spread and non-involved regions. We also investigated how tract-connected the seizure onset zone is to regions of early seizure spread compared with regions of late spread. Comparisons were made after correcting for differences in distance. Sixty-nine seizures were marked across 26 patients with drug-resistant epilepsy; 11 were seizure free after surgery (Engel IA) and 15 were not (Engel IB-Engel IV). The seizure onset zone was more tract-connected to regions of seizure spread than to non-involved regions (P < 0.0001); however, regions of seizure spread were not differentially tract-connected to other regions of seizure spread compared with non-involved regions. In seizure-free patients only, regions of seizure spread were more tract-connected to the seizure onset zone than to other regions of spread (P < 0.0001). Over the temporal evolution of a seizure, the seizure onset zone was significantly more tract-connected to regions of early spread compared with regions of late spread in seizure-free patients only (P < 0.0001). By integrating information on structure, we demonstrate that seizure propagation is likely to be mediated by white matter tracts. The pattern of connectivity between seizure onset zone, regions of spread and non-involved regions demonstrates that the onset zone might be largely responsible for seizures propagating throughout the brain, rather than seizures propagating to intermediate points, from which further propagation takes place. Our findings also suggest that seizure propagation over seconds might be the result of a continuous bombardment of action potentials from the seizure onset zone to regions of spread. In non-seizure-free patients, the paucity of tracts from the presumed seizure onset zone to regions of spread suggests that the onset zone was missed. Fully understanding the structure-propagation relationship might eventually provide insight into selecting the correct targets for epilepsy surgery.

Dissecting Cell-Type Composition and Activity-Dependent Transcriptional State in Mammalian Brains by Massively Parallel Single-Nucleus RNA-Seq.

Massively parallel single-cell RNA sequencing can precisely resolve cellular diversity in a high-throughput manner at low cost, but unbiased isolation of intact single cells from complex tissues such as adult mammalian brains is challenging. Here, we integrate sucrose-gradient-assisted purification of nuclei with droplet microfluidics to develop a highly scalable single-nucleus RNA-seq approach (sNucDrop-seq), which is free of enzymatic dissociation and nucleus sorting. By profiling ∼18,000 nuclei isolated from cortical tissues of adult mice, we demonstrate that sNucDrop-seq not only accurately reveals neuronal and non-neuronal subtype composition with high sensitivity but also enables in-depth analysis of transient transcriptional states driven by neuronal activity, at single-cell resolution, in vivo.

Inhibition of connexin hemichannels alleviates neuroinflammation and hyperexcitability in temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is one of the most common types of epilepsy, yet approximately one-third of patients are refractory to current anticonvulsive drugs, which target neurons and synapses. Astrocytic and microglial dysfunction is commonly found in epileptic foci and has been shown to contribute to neuroinflammation and hyperexcitability in chronic epilepsy. Accumulating evidence points to a key role for glial hemichannels in epilepsy, but inhibiting both connexin (Cx) gap junctions and hemichannels can lead to undesirable side effects because the former coordinate physiological functions of cell assemblies. It would be a great benefit to use an orally available small molecule to block hemichannels to alleviate epileptic symptoms. Here, we explored the effect of D4, a newly developed compound that inhibits the Cx hemichannels but not Cx gap junctions using the pilocarpine mouse model of TLE. In vitro application of D4 caused a near-complete reduction in the pilocarpine-induced cell membrane permeability associated with increased Cx hemichannel activity. Moreover, preadministration of D4 in vivo effectively reduced neuroinflammation and altered synaptic inhibition, which then enhanced the animal survival rate. Posttreatment with a single dose of D4 in vivo has prolonged effects on suppressing the activation of astrocytes and microglia and rescued the changes in neuroinflammatory and synaptic gene expression induced by pilocarpine. Collectively, these results indicate that targeting Cx hemichannels by D4 is an effective and promising strategy for treating epilepsy in which neuroinflammation plays a critical role.

Neuronal mechanism of a BK channelopathy in absence epilepsy and dyskinesia.

A growing number of gain-of-function (GOF) BK channelopathies have been identified in patients with epilepsy and movement disorders. Nevertheless, the underlying pathophysiology and corresponding therapeutics remain obscure. Here, we utilized a knock-in mouse model carrying human BK-D434G channelopathy to investigate the neuronal mechanism of BK GOF in the pathogenesis of epilepsy and dyskinesia. The BK-D434G mice manifest the clinical features of absence epilepsy and exhibit severe motor deficits and dyskinesia-like behaviors. The cortical pyramidal neurons and cerebellar Purkinje cells from the BK-D434G mice show hyperexcitability, which likely contributes to the pathogenesis of absence seizures and paroxysmal dyskinesia. A BK channel blocker, paxilline, potently suppresses BK-D434G­induced hyperexcitability and effectively mitigates absence seizures and locomotor deficits in mice. Our study thus uncovered a neuronal mechanism of BK GOF in absence epilepsy and dyskinesia. Our findings also suggest that BK inhibition is a promising therapeutic strategy for mitigating BK GOF-induced neurological disorders.

Neuronal splicing regulator RBFOX3 mediates seizures via regulating Vamp1 expression preferentially in NPY-expressing GABAergic neurons.

Epilepsy is a common neurological disorder, which has been linked to mutations or deletions of RNA binding protein, fox-1 homolog (Caenorhabditis elegans) 3 (RBFOX3)/NeuN, a neuronal splicing regulator. However, the mechanism of seizure mediation by RBFOX3 remains unknown. Here, we show that mice with deletion of Rbfox3 in gamma-aminobutyric acid (GABA) ergic neurons exhibit spontaneous seizures and high premature mortality due to increased presynaptic release, postsynaptic potential, neuronal excitability, and synaptic transmission in hippocampal dentate gyrus granule cells (DGGCs). Attenuating early excitatory gamma-aminobutyric acid (GABA) action by administering bumetanide, an inhibitor of early GABA depolarization, rescued premature mortality. Rbfox3 deletion reduced hippocampal expression of vesicle-associated membrane protein 1 (VAMP1), a GABAergic neuron-specific presynaptic protein. Postnatal restoration of VAMP1 rescued premature mortality and neuronal excitability in DGGCs. Furthermore, Rbfox3 deletion in GABAergic neurons showed fewer neuropeptide Y (NPY)-expressing GABAergic neurons. In addition, deletion of Rbfox3 in NPY-expressing GABAergic neurons lowered intrinsic excitability and increased seizure susceptibility. Our results establish RBFOX3 as a critical regulator and possible treatment path for epilepsy.

A Bayesian switching linear dynamical system for estimating seizure chronotypes.

Epilepsy is a disorder characterized by paroxysmal transitions between multistable states. Dynamical systems have been useful for modeling the paroxysmal nature of seizures. At the same time, intracranial electroencephalography (EEG) recordings have recently discovered that an electrographic measure of epileptogenicity, interictal epileptiform activity, exhibits cycling patterns ranging from ultradian to multidien rhythmicity, with seizures phase-locked to specific phases of these latent cycles. However, many mechanistic questions about seizure cycles remain unanswered. Here, we provide a principled approach to recast the modeling of seizure chronotypes within a statistical dynamical systems framework by developing a Bayesian switching linear dynamical system (SLDS) with variable selection to estimate latent seizure cycles. We propose a Markov chain Monte Carlo algorithm that employs particle Gibbs with ancestral sampling to estimate latent cycles in epilepsy and apply unsupervised learning on spectral features of latent cycles to uncover clusters in cycling tendency. We analyze the largest database of patient-reported seizures in the world to comprehensively characterize multidien cycling patterns among 1,012 people with epilepsy, spanning from infancy to older adulthood. Our work advances knowledge of cycling in epilepsy by investigating how multidien seizure cycles vary in people with epilepsy, while demonstrating an application of an SLDS to frame seizure cycling within a nonlinear dynamical systems framework. It also lays the groundwork for future studies to pursue data-driven hypothesis generation regarding the mechanistic drivers of seizure cycles.

Characterization of the zebrafish gabra1sa43718/sa43718 germline loss of function allele confirms a function for Gabra1 in motility and nervous system development.

Mutation of the GABRA1 gene is associated with neurodevelopmental defects and epilepsy. GABRA1 encodes for the α1 subunit of the γ-aminobutyric acid type A receptor (GABAAR), which regulates the fast inhibitory impulses of the nervous system. Multiple model systems have been developed to understand the function of GABRA1, but these models have produced complex and, at times, incongruent data. Thus, additional model systems are required to validate and substantiate previous results. We sought to provide initial phenotypic analysis of a novel germline mutant allele. Our analysis provides a solid foundation for the future use of this allele to characterize gabra1 functionally and pharmacologically using zebrafish. We investigated the behavioral swim patterns associated with a nonsense mutation of the zebrafish gabra1 (sa43718 allele) gene. The sa43718 allele causes a decrease in gabra1 mRNA expression, which is associated with light induced hypermotility, one phenotype previously associated with seizure like behavior in zebrafish. Mutation of gabra1 was accompanied by decreased mRNA expression of gabra2, gabra3, and gabra5, indicating a reduction in the expression of additional α sub-units of the GABAAR. Although multiple sub-units were decreased, larvae continued to respond to pentylenetetrazole (PTZ), indicating that a residual GABAAR exists in the sa43718 allele. Proteomics analysis demonstrated that mutation of gabra1 is associated with abnormal expression of proteins that regulate synaptic vesicle fusion, vesicle transport, synapse development, and mitochondrial protein complexes. These data support previous studies performed in a zebrafish nonsense allele created by CRISPR/Cas9 and validate that loss of function mutations in the gabra1 gene result in seizure-like phenotypes with abnormal development of the GABA synapse. Our results add to the existing body of knowledge as to the function of GABRA1 during development and validate that zebrafish can be used to provide complete functional characterization of the gene.