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Gestagens are active ingredients in human and veterinary drugs with progestogenic activity. Two gestagens—progesterone (P4), and the synthetic P4 analogue, melengestrol acetate (MGA)—are approved for use in beef cattle agriculture in North America. Both P4 and MGA have been measured in surface water receiving runoff from animal agricultural operations. This project aimed to assess the morphometric and molecular consequences of chronic exposures to P4, MGA, and their mixture during Western clawed frog metamorphosis. Chronic exposure (from embryo to metamorphosis) to MGA (1.7 µg/L) or P4 + MGA (0.22 µg/L P4 + 1.5 µg/L MGA) caused a considerable dysregulation of metamorphic timing, as evidenced by an inhibition of growth, narrower head, and lack of forelimb emergence in all animals. Molecular analysis revealed that chronic exposure to the mixture induced an additive upregulation of neurosteroid-related (GABAA receptor subunit α6 (gabra6) and steroid 5-alpha reductase 1 (srd5α1) gene expression in brain tissue. Chronic P4 exposure (0.26 µg/L P4) induced a significant upregulation of the expression hypothalamic–pituitary–gonadal (HPG)-related genes (ipgr, erα) in the gonadal mesonephros complex (GMC). Our data suggest that exposure to P4, MGA, and their mixture induces multiple endocrine responses and adverse effects in larval Western clawed frogs. This study helps to better our understanding of the consequences of chronic gestagen exposure and suggests that the implications and risk of high gestagen use in beef cattle feeding operations may extend to the aquatic environment.

The GABA receptor is an important epilepsy-associated candidate gene, and has always been a focus in etiology and in the treatment of epilepsy. This study explores the genetic association between GABA receptor gene polymorphisms and epilepsy in a cohort of the Pakistani population. A case-control study was conducted on 150 patients with idiopathic generalized epilepsy (IGE) and 150 controls. Blood samples were collected, and genomic DNA was extracted and amplified using polymerase chain reaction (PCR). The amplified products were subsequently genotyped by Sanger sequencing and the results were analyzed using the chi-square test. Among the five mutational sites observed, two GABRA1 (rs2279020 and novel c.1016_1017insT) and two GABRA6 (rs3219151 and novel c.1344C>G) were found to be significantly associated with IGE. Amino acid alignment showed that a novel insertion mutation, c.1016_1017insT, in GABRA1 disrupted the reading frame and was possibly damaging, whereas c.1344C>G in GABRA6 was responsible for a synonymous mutation. Therefore, both the GABA receptor genes may play critical roles in the development of epilepsy in Pakistani patients.

This study aims to describe the associations between genetic polymorphisms and therapeutic effect of valproic acid (VPA) in children with focal seizures. Eighty-nine children with focal seizures on VPA therapy were enrolled. Patients’ basic information, dosage regimens, and plasma concentrations were recorded. A 1-year follow-up was performed to evaluate the treatment response. Sixty-six single nucleotide polymorphisms involved in the metabolism, transport, and target receptor of VPA were identified, and their associations with VPA response were analyzed using logistic regression adjusted by various influence factors. Selected polymorphisms involved in the metabolism, transport, and target receptor of VPA were not associated with treatment effect in children with focal seizures. Three variants, rs9313892 (GABRA6, G > A, OR = 2.73, 95% CI 1.00 to 7.48, P = 0.051), rs4921195 (GABRA6, T > C, OR = 2.71, 95% CI 0.99 to 7.42, P = 0.053), and rs424740 (GABRG2, A > T, OR = 0.39, 95% CI 0.15 to 1.01, P = 0.053) had the potential to be associated with the VPA response. Selected genetic polymorphisms were not significantly associated with VPA response in children with focal seizures. However, three GABR variants showed potential to be associated with the response to VPA. Further and larger studies are warranted to confirm the results.

In this study, we investigated the association between bipolar I disorder (BDI) and between cognitive deficits therein and SNPs in GABAergic receptor genes. The sample comprised 477 patients with BDI and 438 healthy controls, with three neurocognitive tests being administered in 123 patients and 164 controls. For three SNPs, rs505474, rs1398175, and rs4868029 in the GABRA2, GABRA4, and GABRP genes, respectively, their allele frequencies were significantly different between patients and controls (Bonferroni-adjusted p = values 3.84 × 10-4 , 9.92 × 10-3 , and 1.22 × 10-2 , respectively). Four haplotypes were significantly associated with BDI (TA and AG for rs3815762 and rs4868029 in GABRP, GG for rs11636988 and rs8024256 in GABRB3 and GAGG for rs2197414, rs4921195, rs13188991, and rs11956731 in GABRA6, with p values of 0.0038, 0.044, 0.0176, and 0.0267, respectively, on 10,000 permutations). Furthermore, the SNP (rs2912585) within 250 kb upstream of the GABRB3 gene displayed a strong association with the Tower of Hanoi (TOH) executive time in the patient group (p = 2.844 × 10-6 ). One other SNP (rs754661), which is located at the intronic region of the same gene, was associated with the global trait of the executive function and post hoc analysis showed significant SNP by group effect (p = 0.0094). Our study supports previous findings that GABAA receptor genes are associated with bipolar disorder; it also suggests that the GABAA genes, especially the GABRB3 gene, might play a role in the executive function deficit in bipolar disorder, although future replication with a larger sample size is needed.

Benign familial infantile epilepsy (BFIE) is the most genetically heterogeneous phenotype among early-onset familial infantile epilepsies. It has an autosomal dominant inheritance pattern with incomplete penetrance. Although PRRT2 is the most mutated gene detected in families with BFIE, other mutations in KCNQ2, SCN2A, and GABRA6 genes have also been described. To date, KCNQ3 mutations have been detected in only four patients with BFIE. Here, we describe the clinical pattern and course of an additional individual with BFIE associated with a novel missense heterozygous KCNQ3 c.1850G>C variant inherited by his unaffected father. The incidence of KCNQ3 mutations among BFIE patients is reported to be low in the literature, however, whether this is underestimated is unclear as not all current epilepsy gene panels include KCNQ3.

Gangguan kecemasan sering terjadi karena pengaruh lingkungan dan juga dipengaruhi oleh variasi genetik. Gamma-aminobutyric acid type A receptors Subunit α-6 (GABRA6) adalah reseptor dari Gamma-aminobutyric acid type A (GABA). Single Nucleotide Polymorphism (SNP) gen GABRA6 pada posisi rs3219151 (T1521C) mempengaruhi respon seseorang terhadap stres. Tujuan penelitian ini adalah identifikasi genotipe gen GABRA6 pada populasi di Kota Bandung serta korelasinya dengan kondisi stres. Penelitian dilakukan terhadap 112 responden yang mengisi kuesioner The Kessler Psychological Distress Scale (K10) untuk melihat kondisi stres. Sampel darah diambil untuk identifikasi variasi gen GABRA6 dan dianalisis menggunakan metode Polymerase Chain Reaction-Refractory Fragment Length Polymorphism (PCR-RFLP) dengan enzim restriksi Alw N1. Hasil identifikasi gen GABRA6 menunjukkan bahwa sebesar 84 responden (75%) memiliki genotipe CC, 14 responden (12,5%) memiliki genotipe CT, dan 14 responden (12,5%) lainnya memiliki genotipe TT. Meskipun mayoritas responden memiliki genotipe CC, namun data genotipe tidak memenuhi asas kesetimbangan Hardy-Weinberg serta tidak ada korelasi antara variasi gen GABRA6 dengan kondisi stres yang menggunakan analisis bivariate ( Chi-Square ). Kata Kunci: GABRA6, Gangguan Kecemasan, Indonesia, PCR-RFLP, SNP γ-Aminobutyric Acid Type A Receptor Subunit α-6 (GABRA6) Gene Polymorphism and Anxiety Disorder Anxiety disorder caused by environmental factor and individual genetic variations. Gamma-aminobutyric acid type A receptors Subunit α-6 (GABRA6) is γ-aminobutyric acid type A (GABA) receptor. Single Nucleotide Polymorphism (SNP) of GABRA6 gene at rs3219151 (T1521C) affected individual response of stress. The aim of present study was to identify GABRA6 genotype variations in Bandung city population and its correlation with stress condition. Samples were collected from 112 respondents who filled The Kessler Psychological Distress Scale (K10) questionnaire for stress condition. Blood samples were collected and identification of GABRA6 gene was analyzed using Polymerase Chain Reaction‑Refractory Fragment Length Polymorphism (PCR-RFLP) by AlwN1 restriction enzyme digestion. The result of present study showed that 84 respondents (75%) have CC genotype, 14 respondents (12.5%) have CT genotype, and other 14 respondents (12.5%) have TT genotype. Most of respondents have CC genotype but the data did not meet the Hardy-Weinberg equilibrium and showed no correlation between GABRA6 gene variations and stress condition using bivariate analysis (Chi-Square). Keywords: Anxiety disorder, GABRA6, Indonesia, PCR-RFLP, SNP

Successful sexual reproduction involves complex, genetically encoded interplay between animal physiology and behavior. The rat provides a highly fecund mammalian model for studying how the brain impacts reproduction. Here, we report a forward genetics screen in rats to identify genes that affect reproduction. A panel of 18 distinct rat strains harboring Sleeping Beauty gene trap mutations were analyzed for the ability to reproduce. As expected, our mutant screen identified genes where reproductive failure was connected to gametogenesis (Btrc, Pan3, Spaca6, Ube2k) and embryogenesis (Alk3, Exoc6b, Slc1a3, Tmx4, Zmynd8). In addition, we identified Ata13 (longevity) and Pclo (neuronal disorders), previously not associated with an inability to conceive. Neurologically, Pclo is known to regulate the size of presynaptic vesicle pools. Here, dominant traits in Pclo mutant rats caused epileptiform activity and affected genes supporting GABAergic synaptic transmission (Gabra6, Gabrg3). Recessive traits in Pclo mutant rats transmitted altered reproductive behavior, as homozygous Pclo mutant rats produced gametes but neither sex would mate with wildtype rats. Pclo mutant rat behavior was linked to endophenotypes signifying compromised brain-gonad crosstalk via disturbed GnRH signaling and allelic markers for major depressive disorder in humans (Grm5, Htr2a, Sorcs3, Negr1, Drd2). Thus, by rat genetics, we identified Pclo as a candidate presynaptic factor required for reproduction.Author SummaryPiccolo gene mutations have previously been identified in human cohorts diagnosed with behavioral syndromes that impact one’s emotions, including depression and bipolar disorder. Although studies in human populations implicate changes to Piccolo’s DNA sequence to enhanced susceptibility for behavioral disorders, studies in mouse models have yet to link Piccolo mutations to altered behavior. Here, by a novel genetics approach, we report Piccolo mutation-dependent effects on reproductive behavior in rats, a finding that may turn out to be relevant to the behavioral effects that are associated with human Piccolo gene mutations. Thus, research aimed at understanding how Piccolo functions to regulate reproduction in rats could prove pivotal in our ability to understand neurological mechanisms that influence human emotions.

Background: The Gamma-aminobutyric acid type A receptor (GABA-A receptor) is affected by ethanol concentrations equivalent to those reached during social drinking. At these concentrations, ethanol usually causes impairment in reaction and motor times in most, but not all, individuals. Objectives: To study the effect of GABA-A receptor variability in motor and reaction times, and the effect of low ethanol doses. Methods: Two hundred and fifty healthy subjects received one single dose of 0.5 g/Kg ethanol per os. Reaction and motor times were determined before ethanol challenge (basal), and when participants reached peak ethanol concentrations. We analyzed all common missense polymorphisms described in the 19 genes coding for the GABA-A receptor subunits by using TaqMan probes. Results: The GABRA6 rs4454083 T/C polymorphisms were related to motor times, with individuals carrying the C/C genotype having faster motor times, both, at basal and at peak ethanol concentrations. The GABRA4 rs2229940 T/T genotype was associated to faster reaction times and with lower ethanol effects, determined as the difference between basal reaction time and reaction time at peak concentrations. All these associations remained significant after correction for multiple comparisons. No significant associations were observed for the common missense SNPs GABRB3 rs12910925, GABRG2 rs211035, GABRE rs1139916, GABRP rs1063310, GABRQ rs3810651, GABRR1 rs12200969 or rs1186902, GABRR2 rs282129, and GABRR3 rs832032. Conclusions: This study provides novel information supporting a role of missense GABA-A receptor polymorphisms in reaction time, motor time and effects of low ethanol doses in vivo.

The idiopathic generalized epilepsy (IGE) is a neurological disorder which accounts for approximately 30% of all epilepsy cases. Patients identified with IGE syndromes have pharmacoresponsive epilepsies without abnormal neurological symptoms, structural brain lesions and are of unknown origin. A genetic etiology to IGEs has been proposed. Gamma amino butyric acid (GABA), a major inhibitory neurotransmitter acts by binding to transmembrane GABAA and GABAB receptors of both pre- and postsynaptic neurons. Synapsin II (SynII), a neuron specific phosphoprotein plays a major role in synaptogenesis and neurotransmitter release. The present study was carried out with an aim to evaluate the association of GABRA6 (rs3219151) TC and Syn II (rs37733634) AG gene polymorphisms with IGE. Molecular analysis revealed that the frequency of 'CC' genotype and 'C'allele of GABRA6 (rs3219151) TC gene polymorphism was significantly higher in IGE patients compared to healthy controls [CC vs. TT, χ2=26; p0.001; Odds ratio=3.6 (95% CI; 2.1-5.9); C vs T, χ2=24.7; p0.001; Odds ratio=1.78 (95% CI; 1.4-2.2)]. The frequency of 'GG' genotype and 'G' allele of the intronic polymorphism AG in Syn II gene was also found to be significantly associated with the disease when compared to controls [GG vs AA, χ2=64.52; p0.001; Odds ratio=7.37 (95% CI; 4.4-12.3); G vs. A, χ2=65.78; p0.001; Odds ratio=2.57 (95% CI; 2.0-3.2)]. The generalized multifactor dimensionality reduction method was employed to detect gene-gene interactions. The gene-gene interaction at two loci involving GABRA6 and Syn II revealed a significant association [χ2=36.6, p0.001, Odds ratio=3.17 (95% CI; 2.2-4.6)] with IGE. Therefore, the present study clearly indicates that both GABRA6 (rs3219151) TC and Syn II (rs37733634) AG polymorphisms are important risk factors for the development of IGE in the South Indian population from Andhra Pradesh. The gene-gene interaction studies demonstrated significant interactive effects of these two loci in the development of the disease.

Pituitary adenylate-cyclase activating polypeptide (PACAP) has neuroprotective and axonal guidance functions, but the mechanisms behind such actions remain unclear. Previously we examined effects of PACAP (PACAP38, 1 pmol) injection intracerebroventrically in a mouse model of permanent middle cerebral artery occlusion (PMCAO) along with control saline (0.9% NaCl) injection. Transcriptomic and proteomic approaches using ischemic (ipsilateral) brain hemisphere revealed differentially regulated genes and proteins by PACAP38 at 6 and 24 h post-treatment. However, as the ischemic hemisphere consisted of infarct core, penumbra, and non-ischemic regions, specificity of expression and localization of these identified molecular factors remained incomplete. This led us to devise a new experimental strategy wherein, ischemic core and penumbra were carefully sampled and compared to the corresponding contralateral (healthy) core and penumbra regions at 6 and 24 h post PACAP38 or saline injections. Both reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were used to examine targeted gene expressions and the collapsin response mediator protein 2 (CRMP2) protein profiles, respectively. Clear differences in expression of genes and CRMP2 protein abundance and degradation product/short isoform was observed between ischemic core and penumbra and also compared to the contralateral healthy tissues after PACAP38 or saline treatment. Results indicate the importance of region-specific analyses to further identify, localize and functionally analyse target molecular factors for clarifying the neuroprotective function of PACAP38.

Objective Several antiepileptic drugs (AEDs) are known to target the GABA(A) receptor through positive allosteric modulation of the receptors, thereby enhancing GABA(A) receptor-mediated inhibition. The large diversity of GABA(A) receptors has been reported in the central nervous system; some of these have been implicated in epilepsy susceptibility and AED resistance, which we aimed to examine. Materials and methods We investigated the association of single-nucleotide polymorphisms in GABA(A) receptor subunit subtype genes namely; rs2279020 (GABRA1), rs3219151 (GABRA6), rs2229944 (GABRB2), and rs211037 (GABRG2) with predisposition to epilepsy and AED resistance. This was assessed in three cohorts of ethnically matched South Indian ancestry: mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) (prototype of AED-resistant epilepsy syndrome), juvenile myoclonic epilepsy (prototype of AED-responsive epilepsy syndrome), and nonepilepsy controls. Results A significant allelic (P=0.0006, odds ratio=1.6, 95% confidence interval=1.22-2.08) and genotypic (P=0.001) association of a synonymous variant in GABRG2, rs211037 (Asn196Asn) was observed with epilepsy irrespective of its phenotype, that is, MTLE-HS or juvenile myoclonic epilepsy. However, this association was not retained in epilepsy patients with a history of febrile seizures. The GABA(A) receptor subunit subtype genes were not found to have any association with AED resistance. In-silico analysis indicated that rs211037 plays a significant role in the transcriptional regulation and splicing regulation. Conclusion We could substantiate that among the GABA(A) receptor subunit gene cluster polymorphisms, the GABRG2, rs211037 predisposes susceptibility to epilepsy, irrespective of its phenotype, but not to AED resistance.

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in mammalian brain. GABA receptor are involved in a number of complex disorders, including substance abuse. No variants of the commonly studied GABA receptor genes that have been associated with substance dependence have been determined to be functional or pathogenic. To reconcile the conflicting associations with substance dependence traits, we performed a meta-analysis of variants in the GABAA receptor genes (GABRB2, GABRA6, GABRA1, and GABRG2 on chromosome 5q and GABRA2 on chromosome 4p12) using genotype data from 4739 cases of alcohol, opioid, or methamphetamine dependence and 4924 controls. Then, we combined the data from candidate gene association studies in the literature with two alcohol dependence (AD) samples, including 1691 cases and 1712 controls from the Study of Addiction: Genetics and Environment (SAGE), and 2644 cases and 494 controls from our own study. Using a Bonferroni-corrected threshold of 0.007, we found strong associations between GABRA2 and AD (P=9 × 10(-6) and odds ratio (OR) 95% confidence interval (CI)=1.27 (1.15, 1.4) for rs567926, P=4 × 10(-5) and OR=1.21 (1.1, 1.32) for rs279858), and between GABRG2 and both dependence on alcohol and dependence on heroin (P=0.0005 and OR=1.22 (1.09, 1.37) for rs211014). Significant association was also observed between GABRA6 rs3219151 and AD. The GABRA2 rs279858 association was observed in the SAGE data sets with a combined P of 9 × 10(-6) (OR=1.17 (1.09, 1.26)). When all of these data sets, including our samples, were meta-analyzed, associations of both GABRA2 single-nucleotide polymorphisms remained (for rs567926, P=7 × 10(-5) (OR=1.18 (1.09, 1.29)) in all the studies, and P=8 × 10(-6) (OR=1.25 (1.13, 1.38)) in subjects of European ancestry and for rs279858, P=5 × 10(-6) (OR=1.18 (1.1, 1.26)) in subjects of European ancestry. Findings from this extensive meta-analysis of five GABAA receptor genes and substance abuse support their involvement (with the best evidence for GABRA2) in the pathogenesis of AD. Further replications with larger samples are warranted.

A GABA(A) receptor α6 subunit mutation, R46W, was identified as a susceptibility gene that may contribute to the pathogenesis of childhood absence epilepsy (CAE), but the molecular basis for alteration of GABA(A) receptor function is unclear. The R46W mutation is located in a region homologous to a GABA(A) receptor γ2 subunit missense mutation, R82Q, that is associated with CAE and febrile seizures in humans. To determine how this mutation reduces GABAergic inhibition, we expressed wild-type (α6β2γ2L and α6β2δ) and mutant (α6(R46W)β2γ2L and α6(R46W)β2δ) receptors in HEK 293T cells and characterize their whole-cell and single-channel currents, and surface and total levels. We demonstrated that gating and assembly of both α6(R46W)β2γ2L and α6(R46W)β2δ receptors were impaired. Compared to wild-type currents, α6(R46W)β2γ2L and α6(R46W)β2δ receptors had a reduced current density, α6(R46W)β2γ2L currents desensitized to a greater extent and deactivated at a slower rate, α6(R46W)β2δ receptors did not desensitize but deactivated faster and both α6(R46W)β2γ2L and α6(R46W)β2δ single-channel current mean open times and burst durations were reduced. Surface levels of coexpressed α6(R46W), β2 and δ, but not γ2L, subunits were decreased. 'Heterozygous' coexpression of α6(R46W) and α6 subunits with β2 and γ2L subunits produced intermediate macroscopic current amplitudes by increasing incorporation of wild-type and decreasing incorporation of mutant subunits into receptors trafficked to the surface. Finally, these findings suggest that similar to the γ2(R82Q) mutation, the CAE-associated α6(R46W) mutation could cause neuronal disinhibition and thus increase susceptibility to generalized seizures through a reduction of αβγ and αβδ receptor function and expression.

Fetal alcohol spectrum disorders (FASD) remain the most common preventable cause of behavioural abnormalities and cognitive deficits, yet little is known about the biological mechanisms involved in FASD pathology. Maternal voluntary ethanol consumption in mice may be a useful model for establishing the biological basis of moderate ethanol exposure phenotypes, which make up the majority of FASD cases. We have employed a two-bottle choice paradigm of maternal ethanol consumption throughout gestation and the early postnatal period in C57BL/6J mice. We assessed the efficacy of this model to produce a range of FASD-relevant phenotypes and evaluated gene expression changes in the adult offspring. Results showed stable maternal consumption and lack of maternal care differences between ethanol-consuming and water-only dams. Ethanol-exposed offspring showed delays in neonatal reflex and coordination development. Further, ethanol-exposed adolescent mice showed decreased activity in a novel environment that appeared to be the result of novelty-induced anxiety, and acquisition learning deficits. Evaluation of the neurotransmitter-associated genes Gabra6, Glra1, and Grin2c revealed significant down-regulation of Glra1 and Grin2c in the brains of ethanol-exposed young adult males. These results suggest that this model is able to produce a range of behavioural phenotypes consistent with prenatal ethanol exposure and may be used to evaluate resulting long-term genetic changes. Given the range of genetic resources available for inbred mouse strains, the model described here may prove to be a useful tool in evaluating the molecular basis of FASD.

Arias B, Aguilera M, Moya J, Saiz PA, Villa H, Ibanez MI, Garcia-Portillo MP, Bobes J, Ortet G, Fananas L. The role of genetic variability in the SLC6A4, BDNF and GABRA6 genes in anxiety-related traits. Objective: The aims of this study were to test the individual association of the serotonin transporter gene (SLC6A4), the brain-derived neurotrophic factor gene (BDNF) and the GABAAα6 receptor subunit gene (GABRA6) with anxiety-related traits and to explore putative gene–gene interactions in a Spanish healthy sample. Method: A sample of 937 individuals from the general population completed the Temperament and Character Inventory questionnaire to explore Harm Avoidance (HA) dimension; a subsample of 553 individuals also filled in the Big Five Questionnaire to explore the Neuroticism dimension. The whole sample was genotyped for the 5-HTTLPR polymorphism (SLC6A4 gene), the Val66Met polymorphism (BDNF gene) and the T1521C polymorphism (GABRA6 gene). Results: Homozygous individuals for the T allele of the T1512C polymorphism presented slightly higher scores for HA than C allele carriers (F = 2.96, P = 0.019). In addition, there was a significant gene–gene interaction on HA between the 5-HTTLPR and Val66Met polymorphisms (F = 3.4, P = 0.009). Conclusion: GABRA6 emerges as a candidate gene involved in the variability of HA. The effect of a significant gene–gene interaction between the SLC6A4 and BDNF genes on HA could explain part of the genetic basis underlying anxiety-related traits.

Background GABAA receptors influence the susceptibility to seizures, and variations in the receptor genes can contribute to antiepileptic drug resistance also. Methods We investigated the possible associations of single nucleotide polymorphisms (SNPs) present in GABRA6 c. 1512 T>C, GABRB2 c. 1412 C>T, and GABRR2 c. IVS2C>G genes of GABAA receptors in epilepsy susceptibility and drug resistance in northern Indian patients with epilepsy. After screening a total of 202 healthy controls and 401 epilepsy patients were enrolled in study. The genotyping was done by PCR-RFLP methods. Results The GABRA6 c. 1512 T>C, polymorphism was conferring risk for epilepsy susceptibility for TC (P = 0.018), CC (P = 0.0001) genotype and for C allele (P = 0.0002). Another polymorphism GABRB2 c. 1412 C>T was also conferring high risk for epilepsy susceptibility CT (P = 0.012), TT (P = 0.778) genotype and for variant T allele (P = 0.034) but was not associated with drug resistance. No association was found with epilepsy susceptibility or with drug resistance in case of GABRR2 c. IVS2C>G gene polymorphism. Conclusion Overall, our findings suggest significant involvement of alpha (GABRA6) and beta (GABRB2) subunits of GABAA receptor in epilepsy susceptibility in north Indian population.

Background: Human anxiety disorders are complex diseases with relatively unknown etiology. Dysfunction of the Gamma-aminobutyric acid (GABA) system has been implicated in many neuropsychiatric conditions, including anxiety and depressive disorders. In this investigation, we explored four GABA receptor genes for their possible associations with genetic risk for anxiety disorders and depression.Methods: Our study sample consisted of 589 cases and 539 controls selected from a large population-based twin registry based upon a latent genetic risk factor shared by several anxiety disorders, major depression, and neuroticism. We subjected these to a two-stage protocol, in which all candidate genetic markers were screened for association in stage 1 (N=376), the positive results of which were tested for replication in stage 2 (N=752). We analyzed data from 26 single nucleotide polymorphisms (SNPs) from four GABA receptor genes: GABRA2, GABRA3, GABRA6, and GABRG2. Results: Of the 26 SNPs genotyped in stage 1, we identified two markers in GABRA3 that met the threshold (P≤.1) to be tested in stage 2. Phenotypic associations of these two markers failed to replicate in stage 2. Conclusions: These findings suggest that common variation in the GABRA2, GABRA3, GABRA6, and GABRG2 genes does not play a major role in liability to anxiety spectrum disorders. Depression and Anxiety 26:998–1003, 2009. Published 2009 Wiley-Liss, Inc.

Physiological response to stress has been linked to a variety of healthy and pathological conditions. The current study conducted a multilevel examination of interactions among environmental toxins (i.e., neighborhood crime and child maltreatment) and specific genetic polymorphisms of the endothelial nitric oxide synthase gene (eNOS) and GABA(A) receptor subunit alpha-6 gene (GABRA6). One hundred eighty-six children were recruited at age 4. The presence or absence of child maltreatment as well as the amount of crime that occurred in their neighborhood during the previous year were determined at that time. At age 9, the children were brought to the lab, where their physiological response to a cognitive challenge (i.e., change in the amplitude of the respiratory sinus arrhythmia) was assessed and DNA samples were collected for subsequent genotyping. The results confirmed that complex Gene × Gene, Environment × Environment, and Gene × Environment interactions were associated with different patterns of respiratory sinus arrhythmia reactivity. The implications for future research and evidence-based intervention are discussed.

The aim of the study was to evaluate the association of transmembrane protein 132D (TMEM132D), catechol-O-methyltransferase (COMT), and gamma-aminobutyric acid (GABA) receptor alpha 6 subunit (GABRA6) genotypes with cingulate, frontal cortex and hippocampal emotional processing in panic disorder (PD) and major depressive disorder (MDD).The single nucleotide polymorphisms (SNPs) in TMEM132D, COMT, and GABRA6 were examined in patients with MDD, PD, and healthy controls. Functional magnetic resonance imaging (fMRI) was performed in patients with MDD, PD, and healthy controls.rs4680 in COMT and rs3219151 in GABRA6 showed positive associations with PD and MDD. A dynamic fearful face was shown to the participants during fMRI scanning. In PD patients, responses in the bilateral anterior cingulate were stronger in carriers of the AA genotype of SNP rs11060369 in TMEM132D compared with carriers of the AC + CC genotype, and stronger in CT + TT genotype carriers of SNP rs3219151 in GABRA6 compared with carriers of the CC genotype. The response in the medial orbital frontal cortex was stronger in carriers of the CT + TT genotypes of SNP rs3219151 in PD. In MDD patients, the response in the right parahippocampus of carriers of the GG genotype of rs4680 in COMT was stronger than that of carriers of the AA + AG genotype.These results suggest that TMEM132D, GABRA6, and COMT variants may increase vulnerability to panic.

Twin studies suggest a genetic influence upon perceived parenting. The D2 dopaminergic receptor is involved in the modulation of social behaviors, and might influence parenting and its perception. A polymorphism (E8) in exon 8 of the D2 receptor gene (DRD2) has been previously associated with alcoholism-related phenotypes. Similarly, the Pro385Ser variant of GABRA6, the polymorphic gene for GABA(A) receptor α6 subunit, has been associated with alcohol- and depression-related traits; and rat pups maintained a more immature GABAR phenotype after brief separation distress. The relationships among DRD2 (E8) and GABRA6 (Pro385Ser) polymorphisms, and perceived parenting were studied here. The association of DRD2 (E8) and GABRA6 (Pro385Ser) genotypes and perceived parental rearing behavior (short-EMBU; questionnaire concerning own memories concerning upbringing) were determined in 207 unrelated adults using multivariate analysis of variance. Temperaments (Temperament and Character Inventory; TCI) were included as covariates. Probands with DRD2 (E8) A/A genotype showed higher scores for father rejection (P = 0.011), parents overprotection (P = 0.021), and father overprotection (P = 0.016) in the total group. An interaction between DRD2 and GABRA6 genotypes on father rejection (P = 0.010) and parents rejection (P = 0.030) was also observed. Further analyses showed that these associations were restricted to the female subgroup only; however, secondary gender-specific analyses were not corrected for multiple testing. Our findings support a role for DRD2 (E8) and GABRA6 (Pro385Ser) in perceived parenting. © 2006 Wiley-Liss, Inc.

We previously performed a genome-wide linkage scan in Portuguese schizophrenia families that identified a risk locus on chromosome 5q31-q35. This finding was supported by meta-analysis of 20 other schizophrenia genome-wide scans that identified 5q23.2-q34 as the second most compelling susceptibility locus in the genome. In the present report, we took a two-stage candidate gene association approach to investigate a group of gamma-aminobutyric acid (GABA) A receptor subunit genes (GABRA1, GABRA6, GABRB2, GABRG2, and GABRP) within our linkage peak. These genes are plausible candidates based on prior evidence for GABA system involvement in schizophrenia. In the first stage, associations were detected in a Portuguese patient sample with single nucleotide polymorphisms (SNPs) and haplotypes in GABRA1 (P=0.00062-0.048), GABRP (P=0.0024-0.042), and GABRA6 (P=0.0065-0.0088). The GABRA1 and GABRP findings were replicated in the second stage in an independent German family-based sample (P=0.0015-0.043). Supportive evidence for association was also obtained for a previously reported GABRB2 risk haplotype. Exploratory analyses of the effects of associated GABRA1 haplotypes on transcript levels found altered expression of GABRA6 and coexpressed genes of GABRA1 and GABRB2. Comparison of transcript levels in schizophrenia patients and unaffected siblings found lower patient expression of GABRA6 and coexpressed genes of GABRA1. Interestingly, the GABRA1 coexpressed genes include synaptic and vesicle-associated genes previously found altered in schizophrenia prefrontal cortex. Taken together, these results support the involvement of the chromosome 5q GABAA receptor gene cluster in schizophrenia, and suggest that schizophrenia-associated haplotypes may alter expression of GABA-related genes.

Background Several investigations suggest that abnormalities in γ-amino butyric acid (GABA) neurotransmission systems may be related to the pathophysiology of schizophrenia. A GABAA receptor gene cluster on 5q31-35 (β2 [GABRB2], α6 [GABRA6], α1 [GABRA1], and γ2 [GABRG2] subunit genes) is one of the most attractive candidate regions for schizophrenia susceptibility. Methods We performed 1) systematic polymorphism search of GABRB2, GABRA6, and GABRA1, in addition to our colleague’s study of GABRG2; 2) evaluation of linkage disequilibrium (LD) within this cluster with 35 single nucleotide polymorphisms (SNPs); 3) “selection of haplotype-tagging (ht) SNPs”; and 4) two-stage association analysis that comprised first-set screening analysis of all htSNPs (288 Japanese schizophrenia patients and 288 control subjects) and second-set replication analysis of the positive htSNPs (901 schizophrenic patients and 806 control subjects). Results In the first-set scan, we found a significant association of two htSNPs in GABRA1, but no association of GABRB2, GABRA6, and GABRG2. In the following second-set analysis, however, we could not confirm these significant associations. Conclusions These results indicate that this gene cluster may not play a major role in Japanese schizophrenia. They also raised an alert with regard to preliminary genetic association analysis using a small sample size.

A substantial body of literature suggests that gamma-aminobutyric acid (GABA) may be involved in the neurochemical pathways contributing to alcohol use and related disorders. Chromosome 5 contains a cluster of GABA(A) receptor genes, GABRA1, GABRA6, GABRB2, and GABRG2, which have been among the most extensively studied in relation to alcohol use. These studies have yielded mixed results. Using data from large, multiplex alcoholic families collected as part of the Collaborative Study on the Genetics of Alcoholism (COGA), we sought to provide more conclusive evidence regarding the role of the GABA(A) receptor genes on chromosome 5. Multiple single nucleotide polymorphisms (SNPs) were tested in each of the four chromosome 5q GABA(A) receptor genes, and we conducted both classic trio-based association analyzes and extended pedigree analyzes. We found no consistent evidence of association with alcohol dependence or alcohol dependence comorbid with antisocial personality disorder (ASPD) for any of the regions tested in the chromosome 5 GABA(A) receptor genes. These analyses suggest that the GABA(A) receptor genes on chromosome 5 do not play a strong role in alcohol dependence. Future studies are planned to test whether these genes are more important in influencing behavioral endophenotypes related to the risk of alcohol dependence.

Nervous system formation requires the elaboration of a complex series of differentiation events in both a spatially and maturation-regulated manner. A fundamental question is how neuronal subtype specification and developmental gene expression are controlled within maturing neurons. The alpha6 subunit of the gamma-aminobutyric acid type A (GABA(A)) receptor (GABRA6) is preferentially expressed in cerebellar granule neurons and is part of an intrinsic program directing their differentiation. We have employed a lentiviral approach to examine the transcriptional mechanisms controlling neuronal subtype-selective expression of this gene. These studies demonstrated that nuclear factor I (NFI) proteins are required for both transgenic GABRA6 promoter activity as well as endogenous expression of this gene in cerebellar granule neurons. Chromatin immunoprecipitation also showed that NFI proteins are bound to the GABRA6 promoter in these cells in vivo. Furthermore, analyses of gene knockout mice revealed that Nfia is specifically required for normal expression of the GABRA6 gene in cerebellar granule neurons. NFI expression and DNA binding activity are highly enriched in granule neurons, implicating this transcription factor family in the neuronal subtype-selective expression of the GABRA6 gene. These studies define a new role for NFI proteins as neuronal subtype-enriched transcriptional regulators that participate in an intrinsic transcriptional program directing the differentiation of cerebellar granule neurons.

Canavan disease (CD) is an inherited leukodystrophy, caused by aspartoacylase (ASPA) deficiency, and accumulation of N-acetylaspartic acid (NAA) in the brain. The gene for ASPA has been cloned and more than 40 mutations have been described, with two founder mutations among Ashkenazi Jewish patients. Screening of Ashkenazi Jews for these two common mutations revealed a high carrier frequency, approximately 1/40, so that programs for carrier testing are currently in practice. The enzyme deficiency in CD interferes with the normal hydrolysis of NAA, which results in disruption of myelin and spongy degeneration of the white matter of the brain. The clinical features of the disease are macrocephaly, head lag, progressive severe mental retardation, and hypotonia in early life, which later changes to spasticity. A knockout mouse for CD has been generated, and used to study the pathophysiological basis for CD. Findings from the knockout mouse indicate that this monogenic trait leads to a series of genomic interaction in the brain. Changes include low levels of glutamate and GABA. Microarray expression analysis showed low level of expression of GABA-A receptor (GABRA6) and glutamate transporter (EAAT4). The gene Spi2, a gene involved in apoptosis and cell death, showed high level of expression. Such complexity of gene interaction results in the phenotype, the proteome, with spongy degeneration of the brain and neurological impairment of the mouse, similar to the human counterpart. Aspartoacylase gene transfer trial in the mouse brain using adenoassociated virus (AAV) as a vector are encouraging showing improved myelination and decrease in spongy degeneration in the area of the injection and also beyond that site.

Objective: To verify interaction between miRNA-7 and its target genes, and explore its possible role in schizophrenia. Methods: The hippocampal neuron cells (HT22) in mice transfected by lentiviral vector with microRNA-7 interference and over-expression were cultured, and the microRNA expression profiling of HT22 target genes were measured by quantitative RT-PCR. Results: The expression of three genes (ERBB4, GABRA6, and GAD1) increased along with the low expression of miRNA-7, and decreased along with the over-expression of microRNA-7. Expression of GRIN2A gene increased along with microRNA-7 over-expression, and decreased when miRNA-7 was interfered. Conclusion: Expression of miRNA-7 may affect its target genes in schizophrenia patients, leading to alteration of neuronal morphology and function, which may play crucial roles in patho-mechanism of schizophrenia. Different from common working pattern, miRNA-7 promotes rather than inhibits the expression of GRIN2A, and the specific molecular mechanism warrents further study.

Quantitative trait analyses in mice suggest a vulnerability locus for physiological alcohol withdrawal severity on a chromosomal segment that harbors the genes encoding the α 1 , α 3 , β 2 , and γ 2 subunits of the γ-aminobutyric acid type-A receptor (GABR). We tested whether genetic variation at the human GABA A α6, β2, and γ2 gene cluster on chromosome 5q33 confers vulnerability to alcohol dependence. The genotypes of three nucleotide substitution polymorphisms of the GABRA6, GABRB2, and GABRG2 genes were assessed in 349 German alcohol-dependent subjects and in 182 ethnically matched controls. To eliminate some of the genetic variance, three more homogeneous subgroups of alcoholics were formed by: (1) a history of alcohol withdrawal seizure or delirium (n = 106); (2) a history of parental alcoholism (n = 120); and (3) a comorbidity of dissocial personality disorder (n = 57). We found no evidence that any of the investigated allelic variants confers vulnerability to either alcohol dependence or severe physiological alcohol withdrawal symptoms or familial alcoholism (p > 0.05). The frequency of the T allele of the GABRA6 polymorphism was significantly increased in dissocial alcoholics [f(T) = 0.799] compared with the controls [f(T) = 0.658; p = 0.002; OR(T+) = 7.26]. Taking into account the high a priori risk of false-positive association findings due to multiple testing, further replication studies are necessary to examine the tentative phenotype-genotype relationship of GABRA6 gene variants and dissocial alcoholism.

We have established that the GABAA receptor alpha 6 (Gabra6) and alpha 1 (Gabra 1) subunit genes are tightly linked on mouse chromosome 11 by analysing the strain distribution patterns of RFLPs for the two genes and microsatellite markers flanking these genes in 26 BXD recombinant inbred strains. These results further demonstrate clustering of the GABAA receptor subunit genes on mouse chromosomes and the synteny for these clusters between the mouse and human genomes.

A gene cluster consisting of the four γ-aminobutyric acidA (GABAA) receptor subunit genes GABRA1, GABRA6, GABRB2, and GABRG2 was assigned to a yeast artificial chromosome (YAC) contig of 5q33. Two of the 26 YACs of the contig are positive for all four subunit genes. The order of the GABR sub-unit genes with respect to known anonymous gene loci is cen — D5S380 — D5S403 — D5S529 — GABRB2 — GABRA1/A6 — GABRG2 — D5S422 — tel. This novel YAC contig lies between known YAC contigs of 5q34/q35 and 5q31-q33.

Background: Neuroticism, as defined and measured by the NEO Personality Inventory (Neuroticism Extraversion and Openness Personality Inventory), is a core personality trait reflecting an individual's emotional reactivity. High neuroticism is thought to be an important vulnerability factor for various psychiatric disorders in the general population, including substance abuse, depression, anxiety, and psychosis. Recent findings support the hypothesis that genetic factors underlying the neuroticism trait could increase the susceptibility to psychiatric disorders. The current study aimed to replicate genetic associations with high neuroticism previously reported in the literature. Methods: We genotyped four polymorphisms: CNR1 (rs7766029), GABRA2 (rs9291283), GABRA6 (rs3219151) and MAMDC1 (rs7151262) in 215 healthy Caucasian subjects, who completed a short version of the NEO-PI. NEO neuroticism scores of the three genotype groups were compared using ANCOVA, with age as a covariate. Results: All four genetic polymorphisms were found to be significantly associated with NEO neuroticism scores (p < 0.0025), but not with any other NEO personality domain. Conclusion: Our results corroborate other studies proposing a role for the GABAergic and cannabinoid systems in the modulation of affective states and stress responses, as measured through neuroticism scores. It is important to replicate the genetic findings of neuroticism, in order to gain a better understanding of this personality domain that has been reported as an important risk factor for mood and anxiety disorders and substance addiction.

Missense polymorphisms or variants that affect function and/or expression of GABAA receptors (GABARs) have been associated with idiopathic generalized epilepsies (IGEs) in GABRA1, GABRA6, GABRB3, GABRG2 and GABRD genes. Three separate IGE-associated mutations were identified in GABAR subunits (β3(G32R), α6(Q237R) and γ2(K328M)), which represent a large range of GABARs in the nervous system. We sought to investigate the contributions of these mutations into the assembly and function of GABARs. Homology modeling suggested that G32R is located within the N-terminal α-helix β3 subunit domain, and Q237R and K328M are located within the pre-M1 segment of the N-terminal α6 subunit domain and the M2-M3 loop of the N-terminal γ2 subunit domain, respectively. We studied gating properties and surface expression of wild type (wt) α1β3γ2, α6β2γ2, α1β2γ2 and mutant α1β3(G32R)γ2, α6(Q237R)β2γ2, α1β2γ2(K328M) receptors expressed in HEK293T cells. We found that the mutations share common gating defects, but distinctive trafficking defects. Thus, mutant β3(G32R) subunits displayed a mixed profile, causing both gating and trafficking defects of α1β3γ2 receptors, whereas mutant α6(Q237R) and γ2(K328M) subunits caused exclusive channel gating defects of α6β2γ2 and α1β2γ2 receptors. Unexpected, homology modeling predicted that the β3(G32R) mutation affects a salt bridge across the γ2/β3 subunit interface, which underlies an assembly motif reported to be essential for inter-subunit interactions in assembled receptors. In contrast, α6(Q237R) and γ2(K328M) subunit mutations are predicted to interact with residues in Pre-M1 domain, M2-M3 loop and Cys-loop of α6 and γ2 subunits that are critical for desensitization-deactivation coupling of GABARs.NIH funding NS33300 to RLM.

BACKGROUND: Nonsyndromic cleft lip with or without cleft palate (NCL/P) is a common structural malformation with a complex and multifactorial etiology. It has been shown that maternal psychological stress in the periconceptional period can contribute to an increase in the risk of NCL/P affecting pregnancy. METHODS: Twenty-four single nucleotide polymorphisms of 11 stress-related genes (COMT, CRHR1, FKBP5, GABRA6, HSD11β2, MAOA, NPY, NR3C1, SERPINA6, SLC6A4, and TPH2) were investigated in 220 healthy mothers of children with facial clefts and 210 matched controls using restriction fragment-length polymorphism and high-resolution melting analysis. RESULTS: We found that polymorphisms in SLC6A4, TPH2, and SERPINA6 appear to be maternal factors increasing the risk of having a child with facial clefts. The closest correlations with NCL/P were found for the SLC6A4 rs2020942 and TPH2 rs10879357 gene variants (odds ratio [OR], 1.720; 95% confidence interval [CI], 1.158–2.553; p = 0.0069; ptrend = 0.0036; and OR, 1.837; 95% CI, 1.226–2.753, p = 0.0030, ptrend = 0.0057; respectively). Moreover, haplotype analysis revealed that several combinations of markers in SLC6A4, TPH2, and SERPINA6 might be significantly associated with the risk of NCL/P affected pregnancies. However, these associations were not statistically significant after correction for multiple testing. CONCLUSION: This study suggests that nucleotide variants of genes encoding components of the hypothalamus-pituitary-adrenal axis and serotoninergic system have a role in the etiology of NCL/P in the Polish population. SLC6A4, TPH2, and SERPINA6 might be novel candidate genes for this common congenital anomaly. Birth Defects Research (Part A), 2011. © 2011 Wiley-Liss, Inc.

Background: The importance of understanding which environmental and biological factors are involved in determining individual differences in physiological response to stress is widely recognized, given the impact that stress has on physical and mental health. Methods: The child-mother attachment relationship and some genetic polymorphisms (5-HTTLPR, COMT and GABRA6) were tested as predictors of salivary cortisol and alpha amylase concentrations, two biomarkers of hypothalamic-pituitary-adrenocortical (HPA) axis and sympathetic adrenomedullary (SAM) system activity, during the Strange Situation (SS) procedure in a sample of more than 100 healthy infants, aged 12 to 18 months. Results: Individual differences in alpha amylase response to separation were predicted by security of attachment in interaction with 5-HTTLPR and GABRA6 genetic polymorphisms, whereas alpha amylase basal levels were predicted by COMT x attachment interaction. No significant effect of attachment, genetics and their interaction on cortisol activity emerged. Conclusions: These results help to disentangle the role played by both genetic and environmental factors in determining individual differences in stress response in infancy. The results also shed light on the suggestion that HPA and SAM systems are likely to have different characteristic responses to stress.

GABAA receptor subunit genes clustered on 5q33 play a role in the development of alcoholism and methamphetamine use disorder without psychosis. The present study explored the possible contribution of the same subunit genes to the development of heroin dependence. Single nucleotide polymorphisms (SNPs) of the GABAA receptor subunits GABRB2, GABRA6, GABRA1, and GABRG2 were examined in 178 male Han Chinese heroin-dependent and 170 male control subjects. A significant difference in allele frequency for the SNP rs211014 in the GABAAγ2 receptor subunit gene between cases and controls was identified (P = 0.015). A possible mechanism for the involvement of the GABA receptor subunit genes on 5q33 in the development of heroin dependence is discussed. © 2007 Wiley-Liss, Inc.