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GABAA receptors (GABAARs) mediate the majority of fast inhibitory transmission throughout the brain. Although it is widely known that pore-forming subunits critically determine receptor function, it is unclear whether their single-channel properties are modulated by GABAAR-associated transmembrane proteins. We previously identified Shisa7 as a GABAAR auxiliary subu-nit that modulates the trafficking, pharmacology, and deactivation properties of these receptors. However, whether Shisa7 also regulates GABAAR single-channel properties has yet to be determined. Here, we performed single-channel recordings of a2b3y2L GABAARs cotransfected with Shisa7 in HEK293T cells and found that while Shisa7 does not change channel slope conductance, it reduced the frequency of receptor openings. Importantly, Shisa7 modulates GABAAR gating by decreasing the duration and open probability within bursts. Through kinetic analysis of individual dwell time components, activation modeling, and macroscopic simulations, we demonstrate that Shisa7 accelerates GABAAR deactivation by governing the time spent between close and open states during gating. Together, our data provide a mechanistic basis for how Shisa7 controls GABAAR gating and reveal for the first time that GABAAR single-channel properties can be modulated by an auxiliary subu-nit. These findings shed light on processes that shape the temporal dynamics of GABAergic transmission. [ABSTRACT FROM AUTHOR]

Purpose: Etomidate is widely used in general anesthesia and sedation, and significant individual differences are observed during anesthesia induction. This study aimed to explore the molecular mechanisms of different etomidate susceptibility at the genetic level. Methods: 128 patients were enrolled in the study. The bispectral index (BIS), mean arterial pressure (MAP) and heart rate (HR) were recorded when the patients entered the operating room for 5 min, before the administration of etomidate, 30 s, 60 s, 90 s, 120 s and 150 s after the administration of etomidate, and the corresponding single nucleotide polymorphisms (SNPs) were analyzed. Results: Significant individual differences were observed in etomidate anesthesia. The results of two-way ANOVA showed that CYP2C9 rs1559, GABRB2 rs2561, GABRA2 rs279858, GABRA2 rs279863 were associated with the BIS value during etomidate anesthesia; UGT1A9 rs11692021 was associated with the Extended Observer's Assessment of Alertness and Sedation (EOAA/S) score during etomidate anesthesia; GABRB2 rs2561 was associated with MAP. Multiple linear stepwise regression model results showed that CYP2C9 rs1559, GABRA2 rs279858 and GABRB2 rs2561 were associated with the BIS value and UGT1A9 rs11692021 was associated with the EOAA/S score; GABRB2 rs2561 was associated with MAP. Conclusion: GABRA2 rs279858, GABRB2 rs2561, CYP2C9 rs1559 and UGT1A9 rs11692021 are the SNPs with individual differences during etomidate anesthesia. This is the first to study the SNPs of etomidate, which can provide certain evidence for the future use of etomidate anesthesia and theoretical basis for precision anesthesia. [ABSTRACT FROM AUTHOR]

Ethnopharmacological Relevance: Mulberry leaf (Folium Mori) is a dried leaf of the dicotyledonous mulberry tree and is a homologous food and medicine. Treating insomnia with it is a common practice in traditional Chinese medicine. But still, its potential sleep-improving mechanism remains to be elucidated., Aim of Review: Potential bioactive components and mechanisms of the sleep-improving effect of purified flavone from mulberry leaves (MLF) were explored through in vivo experiments, network pharmacology analysis, and molecular experimental validation., Materials and Methods: The mice model was established by pentobarbital sodium induction to evaluate the sleep-improving effect of MLF. The MLF's chemical composition was identified through a liquid chromatograph quadrupole time-of-flight mass spectrometer (Q-TOF LC/MS) to elucidate its sleep-improving active ingredient. At last, the underlying mechanism of MLF's sleep-improving effect was elucidated through neurotransmitter detection (ELISA), network pharmacology analysis, and molecular experimental validation (quantitative real-time PCR and western blotting)., Results: MLF could dramatically reduce sleep latency by 35%, prolong sleep duration by 123%, and increase the sleep rate of mice through increasing γ-aminobutyric acid (GABA) and serotonin (5-HT) release in serum, hypothalamus, and hippocampus. Q-TOF LC/MS identified 17 flavonoid components in MLF. Network pharmacological analysis suggested that the key sleep-improving active ingredients in MLF might be quercetin, kaempferol, morin, and delphinidin. The key path for MLF to improve sleep might be the tryptophan metabolism and neuroactive ligand-receptor interaction, and the key targets might be gamma-aminobutyric acid type A receptor subunit alpha2 Gene (GABRA2) and serotonin 1A (5-HT1A) receptors., Conclusions: MLF has shown significant sleep-improving effects in mice and may take effect through regulating the GABA and 5-HT receptors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The sedative and hypnotic properties of 5,7,3',4',5'-pentamethoxyflavone (PMF), a monomer extracted from the leaves of Murraya paniculata (L.) Jack, have been reported. However, the role of PMFs in the development of anxiety remains uncertain. An anxiety model was developed using chronic unpredictable mild stimulation (CUMS). Kunming mice were randomly allocated to the following groups: control, CUMS, PMF (50 mg/kg), PMF (100 mg/kg), and diazepam (3 mg/kg). The anxiolytic effects of PMFs were evaluated using elevated plus maze (EPM) test and open field test (OFT). Enzyme-linked immunosorbent assay (ELISA) kits were used to analyze the serum levels of corticosterone (CORT), 5-hydroxytryptamine (5-HT), gamma-aminobutyric acid (GABA), and cyclic adenosine monophosphate (cAMP) in the hippocampus. High-throughput-16S rRNA sequencing was performed to investigate its effect on the composition of the gut microbiota. Subsequently, western blotting was performed to assess the expression of GABAergic synaptic-associated proteins. PMF effectively mitigated CUMS-induced anxiety-like behavior. Further examination revealed that PMF treatment ameliorated dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis and increased 5-HT and GABA levels in the hippocampus. Notably, the ability of PMF to maintain the stability of GABAergic synapses by enhancing the species composition of the gut microbiota and acting on the adenosine a2a receptor (A 2A R)/gephyrin/gamma-aminobutyric acid A receptor alpha 2 (GABRA2) pathway revealed a previously unrecognized mechanism for the anxiolytic effect of PMF. These findings suggest that PMF enhances the expression of A 2A R, preserves GABAergic synaptic stability, and reduces anxiety by modulating the microbiota composition. Thus, it holds promise as an anxiolytic agent., (© 2024 John Wiley & Sons, Ltd.)

Previous studies have shown that myristic acid (MA), a saturated fatty acid, could promote the proliferation and differentiation of neural stem cells in vitro. However, the effect of MA on hippocampal neurons aging has not been reported in vivo. Here we employed 22-month-old naturally aged C57BL/6 mice to evaluate the effect and mechanism of MA on hippocampal aging. First, we examined a decreased exploration and spatial memory ability in aging mice using the open field test and Morris water maze. Consistently, aging mice showed degenerative hippocampal histomorphology by H&E and Nissl staining. In terms of mechanism, imbalance of GABRB2 and GABRA2 expression in aging mice might be involved in hippocampus aging by mRNA high throughput sequencing (mRNA-seq) and immunohistochemistry (IHC) validation. Then, we revealed that MA alleviated the damage of exploration and spatial memory ability and ameliorated degeneration and aging of hippocampal neurons. Meanwhile, MA downregulated GABRB2 and upregulated GABRA2 expression, indicating MA might alleviate hippocampal aging correlated with GABAergic signaling. In conclusion, our findings revealed MA alleviated hippocampal aging correlated with GABAergic signaling, which might provide insight into the treatment of aging-associated diseases.

Early life stress is an important vulnerability factor for the development of anxiety disorders, depression and late‐onset cognitive decline. Recently, we demonstrated that juvenile stress (JS) lastingly enhanced long‐term potentiation via reduction of steady‐state glutamine synthetase mRNA expression and the associated dysregulation of the astrocytic glutamate‐glutamine cycle in the rat ventral CA1. We now investigated the regulation of steady‐state mRNA expression of neuronal gene products that determine GABAergic and glutamatergic neurotransmission in layers of the ventral and dorsal CA1 after JS. We further studied their interaction with stress in young adult age (AS) to address their putative role in psychopathology development. Strikingly, mRNA levels of the glutamic acid decarboxylase (GAD) isoforms GAD65 and of the GABA‐A receptor α2 (Gabra2) were increased after single JS or AS, but not after combined JS/AS stress experience. In fact, JS/AS resulted in layer‐specific reduction of Gabra2 and also of Gabra1 mRNA levels in the ventral CA1. Furthermore, GAD65 and Gabra2 mRNAs were correlated with glutamatergic AMPA and NMDA receptor subunit mRNAs after single JS and AS, but not after combined JS/AS. Together, these data indicate a loss of allostatic regulation of steady‐state mRNA levels of key GABAergic components that may result in a dysregulation of excitation/ inhibition balance in the ventral CA1 upon dual stress exposure. Finally, individual differences in local glucocorticoid receptor mRNA expression may contribute to this regulation. [ABSTRACT FROM AUTHOR]

BackgroundSurvival analysis was used to explore the addition of a single nucleotide polymorphism (SNP) and covariates (sex, interview age, and ancestry) on a previously published model's ability to predict onset of drinking. A SNP variant of rs279871, in the chromosome 4 gene encoding gamma-aminobutyric acid receptor (GABRA2), was selected due to its associations with alcoholism in young adults and with behaviors that increased risk for early drinking.MethodsA subsample of 674 adolescents (ages 14-17) participating in the Collaborative Study on the Genetics of Alcoholism (COGA) was examined using a previously derived Cox proportional hazards model containing: 1) number of non-drinking related conduct disorder (CD) symptoms, 2) membership in a high-risk alcohol-dependent (AD) family, 3) most best friends drank (MBFD), 4) Achenbach Youth Self Report (YSR) externalizing score, and 5) YSR social problems score. The above covariates along with the SNP variant of GABRA2, rs279871, were added to this model. Five new prototype models were examined. The most parsimonious model was chosen based on likelihood ratio tests and model fit statistics.ResultsThe final model contained four of the five original predictors (YSR social problems score was no longer significant and hence dropped from subsequent models), the three covariates, and a recessive GABRA2 rs279871 TT genotype (two copies of the high-risk allele containing thymine). The model indicated that adolescents with the high-risk TT genotype were more likely to begin drinking than those without this genotype.ConclusionsThe joint effect of the gene (rs279871 TT genotype) and environment (MBFD) on adolescent alcohol initiation is additive, but not interactive, after controlling for behavior problems (CD and YSR externalizing score). This suggests that the impact of the high-risk TT genotype on the onset of drinking is affected by controlling for peer drinking and does not include genotype-by-environment interactions.

Summary: De novo gain-of-function mutations of SCN8A are a significant cause of developmental and epileptic encephalopathy (DEE) (MIM: 614558). The severely affected individuals exhibit refractory seizures, developmental delay, and cognitive disabilities, often accompanied by impaired movement. Individuals with the identical SCN8A variant often differ in clinical course, suggesting a role for modifier genes in disease severity. In a previous study we demonstrated genetic linkage between a hypomorphic mutation in the Gabra2 gene and seizure severity in a mouse model of the human SCN8A pathogenic variant p.Arg1872Trp. Homozygosity for the hypomorphic Gabra2 mutation was associated with early seizure onset and shortened lifespan. We have now confirmed Gabra2 as the modifier gene using a knock-in allele that corrects the splice site variant in strain C57BL/6J. Correction of the Gabra2 variant restores transcript abundance, increases the age of seizure onset, and extends survival of the Scn8a mutant mice. GABRA2 encodes the α2 subunit of the GABAA receptor that provides inhibitory input to dendrites and the the axon initial segment of excitatory neurons. Quantitative variation in human GABAA receptor expression could contribute to variation in the severity of genetic epilepsies and suggests a potential therapeutic intervention.

Background and Objectives: Variants of GABRA2 have been repeatedly associated with alcohol dependence risk. However, no study investigated potential epigenetic alterations in the GABRA2 gene in alcohol-dependent (AD) subjects during alcohol withdrawal. We investigated DNA methylation pattern in the regulatory region of GABRA2 gene in peripheral leukocytes of AD patients and controls. Further, GABRA2 methylation patterns were analysed in neuroblastoma cells under ethanol exposure and withdrawal. Materials and Methods: In the present study, blood samples were obtained from 41 AD subjects on the day of inpatient admission, after the first and second week of inpatient treatment. The comparison group included 47 healthy controls. GABRA2 methylation of 4 CpG sites in the CpG island was compared to neuroblastoma cells which were exposed to 100 mM of ethanol for 2, 5 and 9 days, followed by a withdrawal interval of 4 days. Results: no significant differences in GABRA2 methylation patterns were found in AD subjects over time and vs. controls, after controlling for age. Further, no influence of withdrawal severity, alcohol consumption before admission and other alcohol dependence characteristics were found. Conclusions: The results indicate that GABRA2 methylation in AD individuals and in a cell model is unaffected by alcohol exposition and withdrawal. Influences of GABRA2 on characteristics of alcohol dependence may be exerted by mechanisms other than epigenetic alterations related to alcohol intoxication or withdrawal.

Objective: SCN8A encephalopathy is a developmental epileptic encephalopathy typically caused by de novo gain‐of‐function mutations in Nav1.6. Severely affected individuals exhibit refractory seizures, developmental delay, cognitive disabilities, movement disorders, and elevated risk of sudden death. Patients with the identical SCN8A variant can differ in clinical course, suggesting a role for modifier genes in determining disease severity. The identification of genetic modifiers contributes to understanding disease pathogenesis and suggesting therapeutic interventions. Methods: We generated F1 and F2 crosses between inbred mouse strains and mice carrying the human pathogenic variants SCN8A‐R1872W and SCN8A‐N1768D. Quantitative trait locus (QTL) analysis of seizure‐related phenotypes was used for chromosomal mapping of modifier loci. Results: In an F2 cross between strain SJL/J and C57BL/6J mice carrying the patient mutation R1872W, we identified a major QTL on chromosome 5 containing the Gabra2 gene. Strain C57BL/6J carries a splice site mutation that reduces expression of Gabra2, encoding the α2 subunit of the aminobutyric acid type A receptor. The protective wild‐type allele of Gabra2 from strain SJL/J delays the age at seizure onset and extends life span of the Scn8a mutant mice. Additional Scn8a modifiers were observed in the F2 cross and in an F1 cross with strain C3HeB/FeJ. Significance: These studies demonstrate that the SJL/J strain carries multiple modifiers with protective effects against seizures induced by gain‐of‐function mutations in Scn8a. Homozygosity for the hypomorphic variant of Gabra2 in strain C57BL/6J is associated with early seizure onset and short life span. GABRA2 is a potential therapeutic target for SCN8A encephalopathy. [ABSTRACT FROM AUTHOR]

Abstract Background Cys‐loop receptors control neuronal excitability in the brain and their dysfunction results in numerous neurological disorders. Recently, six missense variants in GABRA2, a member of this family, have been associated with early infantile epileptic encephalopathy (EIEE). We identified a novel de novo missense variant in GABRA2 in a patient with EIEE and performed protein structural analysis of the seven variants. Methods The novel variant was identified by trio whole‐genome sequencing. We performed protein structural analysis of the seven variants, and compared them to previously reported pathogenic mutations at equivalent positions in other Cys‐loop receptors. Additionally, we studied the distribution of disease‐associated variants in the transmembrane helices of these proteins. Results The seven variants are in the transmembrane domain, either close to the desensitization gate, the activation gate, or in inter‐subunit interfaces. Six of them have pathogenic mutations at equivalent positions in other Cys‐loop receptors, emphasizing the importance of these residues. Also, pathogenic mutations are more common in the pore‐lining helix, consistent with this region being highly constrained for variation in control populations. Conclusion Our study reports a novel pathogenic variant in GABRA2, characterizes the regions where pathogenic mutations are in the transmembrane helices, and underscores the value of considering sequence, evolutionary, and structural information as a strategy for variant interpretation of novel missense mutations.

Objective: Animal studies remain essential for understanding mechanisms of epilepsy and identifying new therapeutic targets. However, existing animal models of epilepsy do not reflect the high level of genetic diversity found in the human population. The Collaborative Cross (CC) population is a genetically diverse recombinant inbred panel of mice. The CC offers large genotypic and phenotypic diversity, inbred strains with stable genomes that allow for repeated phenotypic measurements, and genomic tools including whole genome sequence to identify candidate genes and candidate variants. Methods: We evaluated multiple complex epileptic traits in a sampling of 35 CC inbred strains using the flurothyl‐induced seizure and kindling paradigm. We created an F2 population of 297 mice with extreme seizure susceptibility and performed quantitative trait loci (QTL) mapping to identify genomic regions associated with seizure sensitivity. We used quantitative RNA sequencing from CC hippocampal tissue to identify candidate genes and whole genome sequence to identify genetic variants likely affecting gene expression. Results: We identified new mouse models with extreme seizure susceptibility, seizure propagation, epileptogenesis, and SUDEP (sudden unexpected death in epilepsy). We performed QTL mapping and identified one known and seven novel loci associated with seizure sensitivity. We combined whole genome sequencing and hippocampal gene expression to pinpoint biologically plausible candidate genes (eg, Gabra2) and variants associated with seizure sensitivity. Significance: New mouse models of epilepsy are needed to better understand the complex genetic architecture of seizures and to identify therapeutics. We performed a phenotypic screen utilizing a novel genetic reference population of CC mice. The data we provide enable the identification of protective/risk genes and novel molecular mechanisms linked to complex seizure traits that are currently challenging to study and treat. [ABSTRACT FROM AUTHOR]

Background: Cys‐loop receptors control neuronal excitability in the brain and their dysfunction results in numerous neurological disorders. Recently, six missense variants in GABRA2, a member of this family, have been associated with early infantile epileptic encephalopathy (EIEE). We identified a novel de novo missense variant in GABRA2 in a patient with EIEE and performed protein structural analysis of the seven variants. Methods: The novel variant was identified by trio whole‐genome sequencing. We performed protein structural analysis of the seven variants, and compared them to previously reported pathogenic mutations at equivalent positions in other Cys‐loop receptors. Additionally, we studied the distribution of disease‐associated variants in the transmembrane helices of these proteins. Results: The seven variants are in the transmembrane domain, either close to the desensitization gate, the activation gate, or in inter‐subunit interfaces. Six of them have pathogenic mutations at equivalent positions in other Cys‐loop receptors, emphasizing the importance of these residues. Also, pathogenic mutations are more common in the pore‐lining helix, consistent with this region being highly constrained for variation in control populations. Conclusion: Our study reports a novel pathogenic variant in GABRA2, characterizes the regions where pathogenic mutations are in the transmembrane helices, and underscores the value of considering sequence, evolutionary, and structural information as a strategy for variant interpretation of novel missense mutations. [ABSTRACT FROM AUTHOR]

One of the main theories accounting for the underlying pathophysiology of schizophrenia posits alterations in GABAergic neurotransmission. While previous gene expression studies of postmortem brain samples typically report the down-regulation of GABA related genes in schizophrenia, the results are often inconsistent and not uniform across studies. We performed a systematic gene expression analysis of 22 GABA related genes in postmortem superior temporal gyrus (STG) samples of 19 elderly subjects with schizophrenia (mean age: 77) and 14 matched controls from the Icahn school of Medicine at Mount Sinai (MSSM) cohort. To test the validity and robustness of the resulting differentially expressed genes, we then conducted a meta-analysis of the MSSM and an independent dataset from the Stanley Consortium of 14 STG samples of relatively young subjects with schizophrenia (mean age: 44) and 15 matched controls. For the first time, the findings showed the down-regulation of three GABA-receptor subunits of type A, GABRA1, GABRA2 and GABRB3, in the STG samples of subjects with schizophrenia, in both the elderly and the relatively young patients. These findings, as well as previous results, lend weight to the notion of a common upstream pathology that alters GABAergic neurotransmission in schizophrenia. GABRA1, GABRA2 and GABRB3 down-regulation may contribute to the pathophysiology and clinical manifestations of schizophrenia through altered oscillation synchronization in the STG. [ABSTRACT FROM AUTHOR]

GABA type-A (GABA-A) receptors containing the α2 subunit (GABRA2) are expressed in most brain regions and are critical in modulating inhibitory synaptic function. Genetic variation at the GABRA2 locus has been implicated in epilepsy, affective and psychiatric disorders, alcoholism and drug abuse. Gabra2 expression varies as a function of genotype and is modulated by sequence variants in several brain structures and populations, including F2 crosses originating from C57BL/6J (B6J) and the BXD recombinant inbred family derived from B6J and DBA/2J. Here we demonstrate a global reduction of GABRA2 brain protein and mRNA in the B6J strain relative to other inbred strains, and identify and validate the causal mutation in B6J. The mutation is a single base pair deletion located in an intron adjacent to a splice acceptor site that only occurs in the B6J reference genome. The deletion became fixed in B6J between 1976 and 1991 and is now pervasive in many engineered lines, BXD strains generated after 1991, the Collaborative Cross, and the majority of consomic lines. Repair of the deletion using CRISPR-Cas9-mediated gene editing on a B6J genetic background completely restored brain levels of GABRA2 protein and mRNA. Comparison of transcript expression in hippocampus, cortex, and striatum between B6J and repaired genotypes revealed alterations in GABA-A receptor subunit expression, especially in striatum. These results suggest that naturally occurring variation in GABRA2 levels between B6J and other substrains or inbred strains may also explain strain differences in anxiety-like or alcohol and drug response traits related to striatal function. Characterization of the B6J private mutation in the Gabra2 gene is of critical importance to molecular genetic studies in neurobiological research because this strain is widely used to generate genetically engineered mice and murine genetic populations, and is the most widely utilized strain for evaluation of anxiety-like, depression-like, pain, epilepsy, and drug response traits that may be partly modulated by GABRA2 function.

GABA type-A (GABA-A) receptors containing the α2 subunit (GABRA2) are expressed in most brain regions and are critical in modulating inhibitory synaptic function. Genetic variation at the GABRA2 locus has been implicated in epilepsy, affective and psychiatric disorders, alcoholism and drug abuse. Gabra2 expression varies as a function of genotype and is modulated by sequence variants in several brain structures and populations, including F2 crosses originating from C57BL/6J (B6J) and the BXD recombinant inbred family derived from B6J and DBA/2J. Here we demonstrate a global reduction of GABRA2 brain protein and mRNA in the B6J strain relative to other inbred strains, and identify and validate the causal mutation in B6J. The mutation is a single base pair deletion located in an intron adjacent to a splice acceptor site that only occurs in the B6J reference genome. The deletion became fixed in B6J between 1976 and 1991 and is now pervasive in many engineered lines, BXD strains generated after 1991, the Collaborative Cross, and the majority of consomic lines. Repair of the deletion using CRISPR- Cas9 -mediated gene editing on a B6J genetic background completely restored brain levels of GABRA2 protein and mRNA. Comparison of transcript expression in hippocampus, cortex, and striatum between B6J and repaired genotypes revealed alterations in GABA-A receptor subunit expression, especially in striatum. These results suggest that naturally occurring variation in GABRA2 levels between B6J and other substrains or inbred strains may also explain strain differences in anxiety-like or alcohol and drug response traits related to striatal function. Characterization of the B6J private mutation in the Gabra2 gene is of critical importance to molecular genetic studies in neurobiological research because this strain is widely used to generate genetically engineered mice and murine genetic populations, and is the most widely utilized strain for evaluation of anxiety-like, depression-like, pain, epilepsy, and drug response traits that may be partly modulated by GABRA2 function. [ABSTRACT FROM AUTHOR]

Previous research has identified the importance of romantic partners—including spouses, significant others, and dating partners—for influencing the engagement in health-risking behaviors, such as alcohol misuse during emerging adulthood. Although genetic factors are known to play a role in the development of young adult alcohol misuse, little research has examined whether genetic factors affect young adults' susceptibility to their romantic partners' alcohol misusing behaviors. The current study tests whether a single nucleotide polymorphism in the GABRA2 gene (rs279845) moderates the relationship between romantic partner alcohol misuse and frequency of drunkenness in young adulthood. Results revealed differential risk associated with romantic partner alcohol misuse and young adult drunk behavior according to GABRA2 genotype, such that individuals with the TT genotype displayed an elevated risk for frequency of drunkenness when romantic partner alcohol misuse was also high (incidence rate ratio = 1.06, p ⩽ .05). The findings demonstrate the potential for genetic factors to moderate the influence of romantic partners' alcohol misuse on drunk behavior during the transition to young adulthood. [ABSTRACT FROM AUTHOR]

Better integrating human developmental factors in genomic research is part of a set of next steps for testing gene-by-environment interaction hypotheses. This study adds to this work by extending prior research using time-varying effect modeling (TVEM) to evaluate the longitudinal associations between the PROSPER preventive intervention delivery system, a GABRA2 haplotype linked to alcohol use, and their interaction on adolescent delinquency. Logistic and Poisson analyses on eight waves of data spanning ages 11 to 19 (60% female, 90% Caucasian) showed the intervention reduced delinquency from ages 13 to 16. Moreover, interaction analysis revealed that the effect of the multicomponent intervention was significantly greater for T-allele carriers of the GABRA2 SNP rs279845, but only during the 13 to 16 age period. The results are discussed in terms of adolescent delinquency normativeness, implications for preventive intervention research, and the utility of incorporating development in GxE research. [ABSTRACT FROM AUTHOR]

GABAA receptors are ligand-gated anion channels that are important regulators of neuronal inhibition. Mutations in several genes encoding receptor subunits have been identified in patients with various types of epilepsy, ranging from mild febrile seizures to severe epileptic encephalopathy. Using whole-genome sequencing, we identified a novel de novo missense variant in GABRA5 (c.880G > C, p.V294L) in a patient with severe early-onset epilepsy and developmental delay. Targeted resequencing of 279 additional epilepsy patients identified 19 rare variants from nine GABAA receptor genes, including a novel de novo missense variant in GABRA2 (c.875C > A, p.T292K) and a recurrent missense variant in GABRB3 (c.902C > T, p.P301L). Patients with the GABRA2 and GABRB3 variants also presented with severe epilepsy and developmental delay. We evaluated the effects of the GABRA5, GABRA2 and GABRB3 missense variants on receptor function using whole-cell patch-clamp recordings from human embryonic kidney 293T cells expressing appropriate α, β and γ subunits. The GABRA5 p.V294L variant produced receptors that were 10-times more sensitive to GABA but had reduced maximal GABA-evoked current due to increased receptor desensitization. The GABRA2 p.T292K variant reduced channel expression and produced mutant channels that were tonically open, even in the absence of GABA. Receptors containing the GABRB3 p.P301L variant were less sensitive to GABA and produced less GABA-evoked current. These results provide the first functional evidence that de novo variants in the GABRA5 and GABRA2 genes contribute to early-onset epilepsy and developmental delay, and demonstrate that epilepsy can result from reduced neuronal inhibition via a wide range of alterations in GABAA receptor function. [ABSTRACT FROM AUTHOR]

Preventive intervention effects on adolescent alcohol misuse may differ based on genotypes in gene-by-intervention (G x I) interactions, and these G x I interactions may vary as a function of age. The current study uses a novel statistical method, time-varying effect modeling (TVEM), to test an age-varying interaction between a single nucleotide polymorphism in the GABRA2 gene (rs279845) and a preventive intervention in predicting alcohol misuse in a longitudinal study of adolescents (ages 11-20). The preventive intervention was PROSPER, a community-based system for delivery of family and school programs selected from a menu of evidence-based interventions. TVEM results revealed a significant age-varying GABRA2 x intervention interaction from ages 12 to 18, with the peak effect size seen around age 13 (IRR = 0.50). The intervention significantly reduced alcohol misuse for adolescents with the GABRA2 TT genotype from ages 12.5 to 17 but did not reduce alcohol use for adolescents with the GABRA2 A allele at any age. Differences in intervention effects by GABRA2 genotype were most pronounced from ages 13 to 16-a period when drinking is associated with increased risk for alcohol use disorder. Our findings provide additional evidence that intervention effects on adolescent alcohol misuse may differ by genotype, and provide novel evidence that the interaction between GABRA2 and intervention effects on alcohol use may vary with age. Implications for interventions targeting adolescent alcohol misuse are discussed. [ABSTRACT FROM AUTHOR]

Background The heritable risk for alcohol use disorder ( AUD) is expressed partly through alterations in subjective alcohol response. In this study, we investigated the effects of 2 AUD-risk-associated single nucleotide polymorphisms, GABRA2 rs279858 and GRIK1 rs2832407, on the subjective response to alcohol administered intravenously to healthy social drinkers in a laboratory setting. Methods In total, 93 self-identified European American social drinkers underwent 3 blinded laboratory sessions in which they received intravenous infusions of ethanol at 3 target blood alcohol levels (0.00 mg%, 40 mg%, and 100 mg%) using a 'clamp' procedure. The self-reported Biphasic Alcohol Effects Scale ( BAES) stimulation and sedation subscales were the primary outcome measures. We examined the effects of these 2 genetic variants on subjective response to alcohol. Results For the BAES stimulation subscale scores, adjusting for age, baseline scores, and time effects, individuals with 2 copies of the GABRA2 rs279858 C 'risk' allele for AUD exhibited the greatest stimulant responses to high-dose alcohol compared to the other risk allele counts (dose-by-allele count interaction effect, p = 0.001, post hoc contrast for C-allele, p = 0.012). For the BAES sedation subscale scores, adjusting for the same covariates, we detected a dose-by-allele count interaction effect ( p = 0.0044) such that subjects with 2 copies of the GRIK1 C 'risk' allele reported the greatest sedative response to the higher alcohol dose. Conclusions This study suggests that gene variants contributing to the risk for AUD may alter features of the alcohol dose-response relationship in specific ways. GABRA2 rs279858*C enhances stimulant responses to higher levels of alcohol, while the GRIK1 rs2832407*C-allele increases sedative responses. In summary, GRIK1 and GABRA2 variants have distinct effects on the dose-related subjective response to intravenous alcohol in humans. [ABSTRACT FROM AUTHOR]

In the era of plastic use, organisms are constantly exposed to polystyrene particles (PS-Ps). PS-Ps accumulated in living organisms exert negative effects on the body, although studies evaluating their effects on brain development are scarce. In this study, the effects of PS-Ps on nervous system development were investigated using cultured primary cortical neurons and mice exposed to PS-Ps at different stages of brain development. The gene expression associated with brain development was downregulated in embryonic brains following PS-Ps exposure, and Gabra2 expression decreased in the embryonic and adult mice exposed to PS-Ps. Additionally, offspring of PS-Ps-treated dams exhibited signs of anxiety- and depression-like behavior, and abnormal social behavior. We propose that PS-Ps accumulation in the brain disrupts brain development and behavior in mice. This study provides novel information regarding PS-Ps toxicity and its harmful effects on neural development and behavior in mammals. [Display omitted] • Polystyrene particle accumulation in living organisms has negative body effects. • Polystyrene particles reduced gene expression related to brain development in embryonic brains. • Polystyrene particles led to Gabra2 expression change in offspring mouse brains. • Polystyrene particle exposure causes anxiety, depression, and social deficit in mice. [ABSTRACT FROM AUTHOR]

Deficits in neuronal inhibition via gamma-aminobutyric acid (GABA) type A receptors (GABAA-Rs) are implicated in the pathophysiology of major depressive disorder and the therapeutic effects of current antidepressant treatments, however, the relevant GABAA-R subtype as defined by its alpha subunit is still unknown. We previously reported anxiety- and depressive-like behavior in alpha2+/− and alpha2−/− mice, respectively (Vollenweider, 2011). We sought to determine whether this phenotype could be reversed by chronic antidepressant treatment. Adult male mice received 4 or 8 mg/kg fluoxetine or 53 mg/kg desipramine in their drinking water for four weeks before undergoing behavioral testing. In the novelty suppressed feeding test, desipramine had anxiolytic-like effects reducing the latencies to bite and to eat the pellet in both wild-type and alpha2+/− mice. Surprisingly, 4 mg/kg fluoxetine had anxiogenic-like effects in alpha2+/− mice increasing latency to bite and to eat while 8 mg/kg fluoxetine increased the latency to eat in both wild-type and alpha2+/− mice. In the forced swim and tail suspension tests, chronic desipramine treatment increased latency to immobility in wild-type and alpha2−/− mice. In contrast, chronic fluoxetine treatment increased immobility in alpha2−/− mice in both tasks while generally having no effect in wild-type mice. These findings suggest that in preclinical paradigms of anxiety and behavioral despair the antidepressant-like effects of desipramine are independent of alpha2-containing GABAA-Rs, while a reduction in alpha2 expression leads to an increased sensitivity to anxiogenic- and prodepressant-like effects with chronic fluoxetine treatment, pointing to a potential role of alpha2-containing GABAA-Rs in the response to serotonin-selective antidepressants. [ABSTRACT FROM AUTHOR]

Research of GABRA2 gene in alcohol use and impulse control suggests its role in aggressive behaviour. The purpose of the present study was to examine the effects of GABRA2 genotype and stressful life events on aggressive behaviour, alcohol use frequency and occurrence of alcohol use disorder in a population representative sample of adolescents followed up from third grade to 25 years of age. The sample consisted of the younger cohort of the longitudinal Estonian Children Personality, Behaviour and Health Study. Aggressive behaviour was rated with the activity scale of af Klinteberg, Illinois Bully Scale and Buss-Perry Aggression Questionnaire. Stressful life events and alcohol use were self-reported. Life history of aggression and lifetime occurrence of psychiatric disorders were estimated in a structured interview. The sample was genotyped for GABRA2 rs279826 and rs279858 polymorphisms that are in strong linkage disequilibrium and yielded very similar findings: Higher number of stressful life events reported at age 15 was associated with increased fighting in A-allele carriers, but not in GG homozygotes. At age 25, A-allele carriers with more stressful life events scored higher on physical aggression than those with less stress, and this was also observed regarding life history of aggression. A-allele carriers exposed to higher stress had consumed alcoholic beverages more frequently at age 15, and by age 25, they had alcohol use disorder with higher prevalence. The results of the present study suggest that the GABRA2 genotype interacts with stress in young people with impact on the development of alcohol use and aggressive behaviour. [ABSTRACT FROM AUTHOR]

Autism spectrum disorders (ASDs) are a group of developmental disorders that cause variable and heterogeneous phenotypes across three behavioral domains such as atypical social behavior, disrupted communications, and highly restricted and repetitive behaviors. In addition to these core symptoms, other neurological abnormalities are associated with ASD, including intellectual disability (ID). However, the molecular etiology underlying these behavioral heterogeneities in ASD is unclear. Mutations in SHANK2 genes are associated with ASD and ID. Interestingly, two lines of Shank2 knockout mice (e6-7 KO and e7 KO) showed shared and distinct phenotypes. Here, we found that the expression levels of Gabra2 , as well as of GABA receptor-mediated inhibitory neurotransmission, are reduced in Shank2 e6-7, but not in e7 KO mice compared with their own wild type littermates. Furthermore, treatment of Shank2 e6-7 KO mice with an allosteric modulator for the GABA A receptor reverses spatial memory deficits, indicating that reduced inhibitory neurotransmission may cause memory deficits in Shank2 e6-7 KO mice. This article is part of the Special Issue entitled ‘Ionotropic glutamate receptors’. [ABSTRACT FROM AUTHOR]

Background Alcohol use disorders are associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABAA receptor α2-subunit in humans. Deficient GABAergic functioning is linked to impulse control disorders, intermittent explosive disorder, and to drug abuse and dependence, yet it remains unclear whether α2-containing GABAA receptor sensitivity to endogenous ligands is involved in excessive alcohol drinking. Methods Male wild-type (Wt) C57 BL/6J and point-mutated mice rendered insensitive to GABAergic modulation by benzodiazepines (BZD; H101R), allopregnanolone (ALLO) or tetrahydrodeoxycorticosterone (THDOC; Q241M), or high concentrations of ethanol (EtOH) (S270H/L277A) at α2-containing GABAA receptors were assessed for their binge-like, moderate, or escalated chronic drinking using drinking in the dark, continuous access (CA) and intermittent access (IA) to alcohol protocols, respectively. Social approach by mutant and Wt mice in forced alcohol abstinence was compared to approach by Et OH-naïve controls. Social deficits in forced abstinence were treated with allopregnanolone (0, 3.0, 10.0 mg/kg, intraperitoneal [i.p.]) or midazolam (0, 0.56, 1.0 mg/kg, i.p.). Results Mice with BZD-insensitive α2-containing GABAA receptors (H101R) escalated their binge-like drinking. Mutants harboring the Q241M point substitution in Gabra2 showed blunted chronic intake in the CA and IA protocols. S270H/L277A mutants consumed excessive amounts of alcohol but, unlike wild-types, they did not show forced abstinence-induced social deficits. Conclusions These findings suggest a role for: (i) H101 in species-typical binge-like drinking, (ii) Q241 in escalated chronic drinking, and (iii) S270 and/or L277 in the development of forced abstinence-associated social deficits. Clinical findings report reduced BZD-binding sites in the cortex of dependent patients; the present findings suggest a specific role for BZD-sensitive α2-containing receptors. In addition, amino acid residue 241 in Gabra2 is necessary for positive modulation and activation of GABAA receptors by ALLO and THDOC; we postulate that neurosteroid action on α2-containing receptor may be necessary for escalated chronic EtOH intake. [ABSTRACT FROM AUTHOR]

Conduct problems, alcohol problems and hyperactive-inattentive symptoms co-occur at a high rate and are heritable in adolescence. The γ-aminobutyric acid A receptor, α2 gene ( GABRA2) is associated with a broad spectrum of externalizing problems and disinhibitory-related traits. The current study tested whether two important forms of disinhibition in adolescence, impulsivity and sensation seeking, mediated the effects of GABRA2 on hyperactive-inattentive symptoms, conduct problems, and alcohol problems. Participants were assessed at two waves (11-17 and 12-18 years old; N = 292). Analyses used the GABRA2 SNP, rs279858, which tags the two complementary (yin-yang) GABRA2 haplotypes. Multiple informants reported on adolescents' impulsivity and sensation seeking and adolescents self-reported their hyperactive-inattentive symptoms, conduct problems and lifetime alcohol problems. Impulsivity mediated the effect of GABRA2 on alcohol problems, hyperactive-inattentive symptoms, and conduct problems, whereas sensation seeking mediated the effect of GABRA2 on alcohol problems (AA/AG genotypes conferred risk). GABRA2 directly predicted adolescent alcohol problems, but the GG genotype conferred risk. Results suggest that there may be multiple pathways of risk from GABRA2 to adolescent externalizing problems, and suggest important avenues for future research. [ABSTRACT FROM AUTHOR]

Previous studies in our laboratory have shown that the neuron-specific specificity protein 4 (Sp4) transcriptionally regulates many excitatory neurotransmitter receptor subunit genes, such as those for GluN1, GluN2A, and GluN2B of N-methyl- d -aspartate (NMDA) receptors and Gria2 of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. It also regulates Atp1a1 and Atp1b1 subunit genes of Na + /K + -ATPase, a major energy-consuming enzyme, as well as all 13 subunits of cytochrome c oxidase (COX), an important energy-generating enzyme. Thus, there is a tight coupling between energy consumption, energy production, and excitatory neuronal activity at the transcriptional level in neurons. The question is whether inhibitory neurotransmitter receptors are also regulated by Sp4. In the present study, we tested our hypothesis that Sp4 regulates receptor subunit genes of a major inhibitory neurotransmitter, GABA, specifically GABA A receptors. By means of multiple approaches, including in silico analysis, electrophoretic mobility shift and supershift assays, real-time quantitative PCR, chromatin immunoprecipitation, promoter mutational analysis, over-expression and shRNA of Sp4, functional assays, and western blots, we found that Sp4 functionally regulates the transcription of Gabra1 (GABA A α1) and Gabra2 (GABA A α2), but not Gabra3 (GABA A α3) subunit genes. The binding sites of Sp4 are conserved among rats, humans, and mice. Thus, our results substantiate our hypothesis that Sp4 plays a key role in regulating the transcription of GABA A receptor subunit genes. They also indicate that Sp4 is in a position to transcriptionally regulate the balance between excitatory and inhibitory neurochemical expressions in neurons. [ABSTRACT FROM AUTHOR]

Alcohol dependence is a common chronic disorder precipitated by the complex interaction between biological, genetic and environmental risk factors. Recent studies have demonstrated that polymorphisms of the gene encoding the GABA A receptor α 2 subunit (GABRA2) are associated with alcohol dependence in different populations of European ancestry. As aggression often occurs in the context of alcohol dependence, the aim of this study was to examine the allelic and haplotypic association of GABRA2 gene with alcohol dependence and related aggressive behavior in subjects of Eastern European (Croatian) origin. Genotyping of the 3 single nucleotide polymorphisms (SNPs) across the GABRA2 gene (rs567926, rs279858 and rs9291283) was performed in patients with alcohol dependence (N = 654) and healthy control subjects (N = 574). Alcohol-dependent participants were additionally subdivided according to the presence/absence of aggressive behavior and type of alcohol dependence according to the Cloninger's classification. The association of rs279858 with alcohol dependence yielded nominal significance level. Haplotype analysis revealed a high degree of linkage disequilibrium (LD) for rs567926 and rs279858, but not for rs9291283 polymorphism in the GABRA2 gene. In patients with alcohol dependence, the A–C (rs567926 and rs279858) haplotype carriers were more likely to demonstrate aggressive behavior. The same haplotype (present only in 1.6% of all subjects) was significantly more often present in patients with a combination of early onset alcohol abuse and aggression, corresponding to the Cloninger's type II alcoholism subgroup. These findings support the involvement of GABRA2 gene in alcohol dependence-related aggressive behavior. [ABSTRACT FROM AUTHOR]

Rationale: Benzodiazepines (BZDs) are prescribed to reduce anxiety, agitation, and muscle spasms and for their sedative-hypnotic and anticonvulsant effects. Under specific conditions, BZDs escalate aggression in some individuals. Specific effects of BZDs have been linked to the α-subunit subtype composition of GABA receptors. Objectives: Point-mutated mice rendered selectively insensitive to BZDs at α1-, α2-, or α3-containing GABA receptors were used to determine which α-subunit subtypes are necessary for BZDs to escalate aggression and social approach and to reduce fear-motivated behavior. Methods: During resident-intruder confrontations, male wild-type (WT) and point-mutated α1(H101R), α2(H101R), and α3(H126R) mice were treated with midazolam (0-1.7 mg/kg, i.p.) and evaluated for aggression in an unfamiliar environment. Separate midazolam-treated WT and point-mutated mice were assessed for social approach toward a female or investigated in a 6-day fear-potentiated startle procedure. Results: Moderate doses of midazolam (0.3-0.56 mg/kg, i.p.) escalated aggression in WT and α3(H126R) mutants and increased social approach in WT and α1(H101R) mice. The highest dose of midazolam (1.0 mg/kg) reduced fear-potentiated startle responding. All mice were sensitive to the sedative effect of midazolam (1.7 mg/kg) except α1(H101R) mutants. Conclusions: Midazolam requires BZD-sensitive α1- and α2-containing GABA receptors in order to escalate aggression and α2- and α3-containing receptors to reduce social anxiety-like behavior. GABA receptors containing the α1-subunit are crucial for BZD-induced sedation, while α2-containing GABA receptors may be a shared site of action for the pro-aggressive and anxiolytic effects of BZDs. [ABSTRACT FROM AUTHOR]

Background Genetic variation in a region of chromosome 4p12 that includes the GABAA subunit gene GABRA2 has been reproducibly associated with alcohol dependence ( AD). However, the molecular mechanisms underlying the association are unknown. This study examined correlates of in vitro gene expression of the AD-associated GABRA2 rs279858*C-allele in human neural cells using an induced pluripotent stem cell (iPSC) model system. Methods We examined mRNA expression of chromosome 4p12 GABAA subunit genes ( GABRG1, GABRA2, GABRA4, and GABRB1) in 36 human neural cell lines differentiated from iPSCs using quantitative polymerase chain reaction and next-generation RNA sequencing. mRNA expression in adult human brain was examined using the BrainCloud and BRAINEAC data sets. Results We found significantly lower levels of GABRA2 mRNA in neural cell cultures derived from rs279858*C-allele carriers. Levels of GABRA2 RNA were correlated with those of the other 3 chromosome 4p12 GABAA genes, but not other neural genes. Cluster analysis based on the relative RNA levels of the 4 chromosome 4p12 GABAA genes identified 2 distinct clusters of cell lines, a low-expression cluster associated with rs279858*C-allele carriers and a high-expression cluster enriched for the rs279858*T/T genotype. In contrast, there was no association of genotype with chromosome 4p12 GABAA gene expression in postmortem adult cortex in either the BrainCloud or BRAINEAC data sets. Conclusions AD-associated variation in GABRA2 is associated with differential expression of the entire cluster of GABAA subunit genes on chromosome 4p12 in human iPSC-derived neural cell cultures. The absence of a parallel effect in postmortem human adult brain samples suggests that AD-associated genotype effects on GABAA expression, although not present in mature cortex, could have effects on regulation of the chromosome 4p12 GABAA cluster during neural development. [ABSTRACT FROM AUTHOR]

We examine whether parental externalizing behavior has an indirect effect on adolescent externalizing behavior via elevations in life events, and whether this indirect effect is further qualified by an interaction between life events and adolescents' GABRA2 genotype (rs279871). We use data from 2 samples: the Child Development Project (CDP; n = 324) and FinnTwin12 (n = 802). In CDP, repeated measures of life events, mother-reported adolescent externalizing, and teacher-reported adolescent externalizing were used. In FinnTwin12, life events and externalizing were assessed at age 14. Parental externalizing was indexed by measures of antisocial behavior and alcohol problems or alcohol dependence symptoms in both samples. In CDP, parental externalizing was associated with more life events, and the association between life events and subsequent adolescent externalizing varied as a function of GABRA2 genotype (p ≤ .05). The association between life events and subsequent adolescent externalizing was stronger for adolescents with 0 copies of the G minor allele compared to those with 1 or 2 copies of the minor allele. Parallel moderation trends were observed in FinnTwin12 (p ≤ .11). The discussion focuses on how the strength of intergenerational pathways for externalizing psychopathology may differ as a function of adolescent-level individual differences. [ABSTRACT FROM AUTHOR]

The homeostatic regulation of neuronal activity in glutamatergic and GABAergic synapses is critical for neural circuit development and synaptic plasticity. The induced expression of the transcription factor early growth response 1 (Egr-1) in neurons is tightly associated with many forms of neuronal activity, but the underlying target genes in the brain remained to be elucidated. This study uses a quantitative real-time PCR approach, in combination with in vivo chromatin immunoprecipitation, and reveals that GABAA receptor subunit, GABRA2 (α2), GABRA4 (α4), and GABRQ (θ) genes, are transcriptional targets of Egr-1. Transfection of a construct that over-expresses Egr-1 in neuroblastoma (Neuro2A) cells up-regulates the α2, α4, and θ subunits. Given that Egr-1 knockout mice display less GABRA2, GABRA4, and GRBRQ mRNA in the hippocampus, and that Egr-1 directly binds to their promoters and induces mRNA expression, the present findings support a role for Egr-1 as a major regulator for altered GABAA receptor composition in homeostatic plasticity, in a glutamatergic activity-dependent manner. [ABSTRACT FROM AUTHOR]

Background This study's primary aim was to examine age-specific associations between GABRA2, rule breaking, problematic alcohol use, and substance abuse symptomatology. The secondary aim was to examine the extent to which rule breaking mediates the GABRA2-substance abuse relationship. Methods A sample ( n = 518) of primarily male (70.9%) and White (88.8%) adolescents from the Michigan Longitudinal Study was assessed from ages 11-18. Age-specific effects of GABRA2 on rule breaking, problematic alcohol use, and substance abuse symptomatology were examined using nested path models. The role of rule breaking as a mediator in the association between GABRA2 and substance abuse outcomes was tested using prospective cross-lagged path models. Results GABRA2 is significantly ( p < 0.05) associated with rule breaking in mid- to late-adolescence, but not substance abuse symptomatology across adolescence. GABRA2 effects on problematic alcohol use and substance abuse symptomatology operate largely (45.3% and 71.1%, respectively, p < 0.05) via rule breaking in midadolescence. Conclusions GABRA2 represents an early risk factor for an externalizing pathway to the development of problematic alcohol and drug use. [ABSTRACT FROM AUTHOR]

Longitudinal analyses allow us to understand how genetic risk unfolds across development, in a way that is not possible with cross-sectional analyses of individuals at different ages. This has received little attention in genetic association analyses. In this study, we test for genetic effects of GABRA2, a gene previously associated with alcohol dependence, on trajectories of drunkenness from age 14 to 25. We use data from 1070 individuals who participated in the prospective sample of the Collaborative Study on the Genetics of Alcoholism, in order to better understand the unfolding of genetic risk across development. Piecewise linear growth models were fit to model the influence of genotype on rate of increase in drunkenness from early adolescence to young adulthood (14-18 years), the change in drunkenness during the transition to adulthood (18-19 years) and the rate of change in drunkenness across young adulthood (≥ 19 years). Variation in GABRA2 was associated with an increase in drunkenness that occurred at the transition between adolescence and adulthood. The genotypic effect was more pronounced in females. These analyses illustrate the importance of longitudinal data to characterize how genetic effects unfold across development. The findings suggest that transitions across important developmental periods may alter the relative importance of genetic effects on patterns of alcohol use. The findings also suggest the importance of considering gender when evaluating genetic effects on drinking patterns in males and females. [ABSTRACT FROM AUTHOR]

Background Genetic predisposition and environmental influences are both important factors in the development of problematic behavior leading to substance use in adolescence. Involvement with delinquent peers also strongly predicts adolescent externalizing behavior. Several lines of evidence support a role of GABRA2 on externalizing behavior related to disinhibition. However, whether this genetic association is influenced by the environment such as peer behavior remains unknown. Methods We examined the moderating role of GABRA2 genetic variation on the socialization model of delinquent peer affiliation (at ages 12-14 years) on externalizing behavior (at ages 15-17 years) in the Michigan Longitudinal Study ( MLS) adolescent sample. The sample consisted of 244 adolescents (75 females and 152 with at least one parent with a DSM-IV lifetime alcohol dependence/abuse diagnosis). Peer delinquent activity reported by the participant and teacher-reported adolescent externalizing behavior (Teacher Report Form ( TRF) were assessed. Results No main effect of the GABRA2 SNP rs279826, which tags a large haplotype, on externalizing behavior was observed. However, there was a statistically reliable GABRA2 × peer delinquency interaction. The effect of peer delinquent involvement on externalizing scores and the rule breaking subscale is significantly stronger for those with the GG genotype compared to A-carriers, whereas there was no effect of genotype on externalizing in the absence of peer delinquent involvement. No interaction was observed for the aggression subscale. Conclusion Our results suggest that the genetic effect of GABRA2 on externalizing behavior, more specifically on rule breaking is, at least in part, due to its effect on susceptibility to environmental exposure (i.e., peer delinquency). [ABSTRACT FROM AUTHOR]

GABA A receptors (GABA A Rs) mediate the majority of fast inhibitory transmission throughout the brain. Although it is widely known that pore-forming subunits critically determine receptor function, it is unclear whether their single-channel properties are modulated by GABA A R-associated transmembrane proteins. We previously identified Shisa7 as a GABA A R auxiliary subunit that modulates the trafficking, pharmacology, and deactivation properties of these receptors. However, whether Shisa7 also regulates GABA A R single-channel properties has yet to be determined. Here, we performed single-channel recordings of α2β3γ2L GABA A Rs cotransfected with Shisa7 in HEK293T cells and found that while Shisa7 does not change channel slope conductance, it reduced the frequency of receptor openings. Importantly, Shisa7 modulates GABA A R gating by decreasing the duration and open probability within bursts. Through kinetic analysis of individual dwell time components, activation modeling, and macroscopic simulations, we demonstrate that Shisa7 accelerates GABA A R deactivation by governing the time spent between close and open states during gating. Together, our data provide a mechanistic basis for how Shisa7 controls GABA A R gating and reveal for the first time that GABA A R single-channel properties can be modulated by an auxiliary subunit. These findings shed light on processes that shape the temporal dynamics of GABAergic transmission. SIGNIFICANCE STATEMENT Although GABA A receptor (GABA A R) single-channel properties are largely determined by pore-forming subunits, it remains unknown whether they are also controlled by GABA A R-associated transmembrane proteins. Here, we show that Shisa7, a recently identified GABA A R auxiliary subunit, modulates GABA A R activation by altering single-channel burst kinetics. These results reveal that Shisa7 primarily decreases the duration and open probability of receptor burst activity during gating, leading to accelerated GABA A R deactivation. These experiments are the first to assess the gating properties of GABA A Rs in the presence of an auxiliary subunit and provides a kinetic basis for how Shisa7 modifies temporal attributes of GABAergic transmission at the single-channel level., (Copyright © 2022 the authors.)

Background and Objectives: Variants of GABRA2 have been repeatedly associated with alcohol dependence risk. However, no study investigated potential epigenetic alterations in the GABRA2 gene in alcohol-dependent (AD) subjects during alcohol withdrawal. We investigated DNA methylation pattern in the regulatory region of GABRA2 gene in peripheral leukocytes of AD patients and controls. Further, GABRA2 methylation patterns were analysed in neuroblastoma cells under ethanol exposure and withdrawal. Materials and Methods: In the present study, blood samples were obtained from 41 AD subjects on the day of inpatient admission, after the first and second week of inpatient treatment. The comparison group included 47 healthy controls. GABRA2 methylation of 4 CpG sites in the CpG island was compared to neuroblastoma cells which were exposed to 100 mM of ethanol for 2, 5 and 9 days, followed by a withdrawal interval of 4 days. Results: no significant differences in GABRA2 methylation patterns were found in AD subjects over time and vs. controls, after controlling for age. Further, no influence of withdrawal severity, alcohol consumption before admission and other alcohol dependence characteristics were found. Conclusions: The results indicate that GABRA2 methylation in AD individuals and in a cell model is unaffected by alcohol exposition and withdrawal. Influences of GABRA2 on characteristics of alcohol dependence may be exerted by mechanisms other than epigenetic alterations related to alcohol intoxication or withdrawal.