GABRA2 Research Articles

Contribution of genes in the GABAergic pathway to bipolar disorder and its executive function deficit in the Chinese Han population.

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.

A new stress sensor and risk factor for suicide: the T allele of the functional genetic variant in the GABRA6 gene

Low GABA transmission has been reported in suicide, and GABRA6 rs3219151 T allele has been associated with greater physiological and endocrine stress response in previous studies. Although environmental stress also plays a role in suicide, the possible role of this allele has not been investigated in this respect. In our present study effect of rs3219151 of GABRA6 gene in interaction with recent negative life events on lifetime and current depression, current anxiety, as well as lifetime suicide were investigated using regression models in a white European general sample of 2283 subjects. Post hoc measures for phenotypes related to suicide risk were also tested for association with rs3219151 in interaction with environmental stress. No main effect of the GABRA6 rs3219151 was detected, but in those exposed to recent negative life events GABRA6 T allele increased current anxiety and depression as well as specific elements of suicide risk including suicidal and death-related thoughts, hopelessness, restlessness and agitation, insomnia and impulsiveness as measured by the STOP task. Our data indicate that stress-associated suicide risk is elevated in carriers of the GABRA6 rs3219151 T allele with several independent markers and predictors of suicidal behaviours converging to this increased risk.

Study on the causative genes and analysis of genotypes and phenotypes of Dravet syndrome

Objective To identify the rare causative genes of Dravet syndrome(DS) in patients who do not have SCN1A mutation and to analyze genotypes and phenotypes of DS patients with different rare causative genes. Methods DS patients were collected from the Pediatric Department of Peking University First Hospital from February 2005 to August 2016.SCN1A and PCDH19 gene mutations were screened by Sanger sequencing and multiple ligation-dependant probe amplification (MLPA). Next generation sequencing (NGS) for epilepsy-related gene-panel was applied to SCN1A and PCDH19 mutation-negative patients.The phenotypes of DS patients with different rare causative genes were analyzed. Results Six hundred and seventy patients with DS were collected and 556 patients (83.0%) carried SCN1A mutations and 6 patients with PCDH19 mutations.Epilepsy-related gene-panel was applied to remain 108 patients without SCN1A or PCDH19 mutation, and among them 12 patients were detected with 6 rare causative genes, with heterozygous mutations in GABRA1 mutations in 3, GABRG2 in 2 cases, GABRB2 mutations in 2 cases and SCN2A mutation in 1 case, complex heterozygous mutations in TBC1D24 in 2 cases and ALDH7A1 in 2 cases.The clinical phenotypes of 6 patients with PCDH19 mutations were featured by clustering of repeated seizures with short periods of times, only 1 case had an episode of status epilepticus.Patients with GABRB2 mutations had a relatively better outcome of seizure control.Many episodes of myoclonic status were emerging as hallmark features in patients with TBC1D24 mutations.Vitamin B had a dramatic therapeutic effect in patients with ALDH7A1 mutations.The clinical phenotypes of DS patients with GABRG2, SCN2A and GABRA1 had no obvious specificity. Conclusions The rare causative genes in DS patients include PCDH19, GABRG2, SCN2A, GABRA1, GABRB2, TBC1D24 and ALDH7A1.The finding of causative genes GABRB2 and TBC1D24 may enrich the gene spectrum of DS.Patients with PCDH19 mutations are featured by clustering of repeated seizures with short periods of time and rare status epilepticus.Patients with GABRB2 mutations have a relatively better outcome of seizure control.Many episodes of myoclonic status are emerging as hallmark features in patients with TBC1D24 mutations. Key words: Dravet syndrome; Gene mutation; Genotypes; Phenotypes

Decreasing the Expression of GABAA α5 Subunit-Containing Receptors Partially Improves Cognitive, Electrophysiological, and Morphological Hippocampal Defects in the Ts65Dn Model of Down Syndrome.

Trisomy 21 or Down syndrome (DS) is the most common cause of intellectual disability of a genetic origin. The Ts65Dn (TS) mouse, which is the most commonly used and best-characterized mouse model of DS, displays many of the cognitive, neuromorphological, and biochemical anomalies that are found in the human condition. One of the mechanisms that have been proposed to be responsible for the cognitive deficits in this mouse model is impaired GABA-mediated inhibition. Because of the well-known modulatory role of GABAA α5 subunit-containing receptors in cognitive processes, these receptors are considered to be potential targets for improving the intellectual disability in DS. The chronic administration of GABAA α5-negative allosteric modulators has been shown to be procognitive without anxiogenic or proconvulsant side effects. In the present study, we use a genetic approach to evaluate the contribution of GABAA α5 subunit-containing receptors to the cognitive, electrophysiological, and neuromorphological deficits in TS mice. We show that reducing the expression of GABAA α5 receptors by deleting one or two copies of the Gabra5 gene in TS mice partially ameliorated the cognitive impairments, improved long-term potentiation, enhanced neural differentiation and maturation, and normalized the density of the GABAergic synapse markers. Reducing the gene dosage of Gabra5 in TS mice did not induce motor alterations and anxiety or affect the viability of the mice. Our results provide further evidence of the role of GABAA α5 receptor-mediated inhibition in cognitive impairment in the TS mouse model of DS.

Abstract 4274: The contribution of deleterious germ-line mutations of susceptibility genes to ovarian, fallopian tube, and peritoneal cancers in Japanese

Abstract Different ethnic groups present specific morphological features in ovarian cancer (OC). High-grade serous OC is more frequently found in Caucasian women, in contrast clear cell OC is more frequently found in East Asian women. Although inherited mutations of BRCA1 or BRCA2 (BRCA1/2) and other genes are known to predispose to OC, the contributions of these inherited mutations on disease burden is not well characterized in Japanese OC patients. Using a comprehensive genetic testing panel, the aim of our study was to identify the prevalence of pathogenic germ-line mutations of candidate genes associated with genetic predisposition to OC in Japanese patients with ovarian, fallopian tube, or peritoneal cancer.Samples from 236 individuals with unselected ovarian, fallopian tube, or peritoneal cancer, which were obtained from the Keio Women’s Health Biobank (KWB) from the School of Medicine at Keio University (Tokyo, Japan), were used for this study. Germ-line DNA was enriched using the SureSelect XT Target Enrichment System (Agilent Technologies) designed for 75 or 79 genes as a custom OC panel, followed by sequencing using MiSeq (Illumina). Detected variants, including point mutations, small indels, and a gross deletion, were classified according to the American College of Medical Genetics and Genomics (ACMG) recommendations. Furthermore, BRCA1/2 variants were interpreted using resources from Myriad Genetic Laboratories.Forty-two (17.8%) OC patients had germ-line mutations of cancer predisposition genes. BRCA1/2 pathological germ-line mutations were found in 27 cases (11.4%) while six cases (2.5%) had a mutation in a mismatch repair gene (MLH1, MSH2, MSH6, or PMS2). Furthermore, ten cases (4.2%) had germ-line mutations in the RAD51D, ATM, MRE11A, FANCC, or GABRA2 genes. Of patients with a BRCA1/2 mutation (n=27), we found that the most common histological subtype was high-grade serous OC, but we also found two cases with clear cell carcinoma. Of 42 cases with an inherited mutation, we found that 25% (6/24) had no family history of cancer, and 78% (31/41) were under 60 years old at diagnosis.We found that approximately 18% of unselected Japanese patients with ovarian, fallopian tube, or peritoneal cancer were associated with inherited mutations of cancer-predisposing genes. Our study demonstrates that comprehensive genetic testing is informative for all women with ovarian, fallopian tube, and peritoneal cancers to establish personalized clinical management and genetic counseling, irrespective of the patient's histological subtypes, ages or family histories. Citation Format: Akira Hirasawa, Issei Imoto, Takuya Naruto, Tomoko Akahane, Wataru Yamagami, Nobuyuki Susumu, Hitoshi Tsuda, Daisuke Aoki. The contribution of deleterious germ-line mutations of susceptibility genes to ovarian, fallopian tube, and peritoneal cancers in Japanese [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4274. doi:10.1158/1538-7445.AM2017-4274

GPD1L is down-regulated by a three-microRNA signature in pancreatic cancer

Background: The prognosis of pancreatic ductal adenocarcinoma (PDAC) is very poor and its underlying mechanism is far from clear. Many studies show that PDAC has distinct microRNA signatures, but their target genes remain largely unknown. Methods: Reproducible candidate microRNA signature of PDAC from three highly cited studies was measured in 20 pairs of PDAC tissues and adjacent normal tissues. The target genes of candidate microRNAs were predicted by miRDB and validated by quantitative real-time PCR, western blot and 3'UTR luciferase assay. The prognostic association of target gene was analyzed using PROGgeneV2 Database. The effects of target gene on tumor phenotypes were evaluated with MTT assay, clone formation assay and Annexin V-FITC apoptosis assay. Results: Among the 5-microRNA panel, an up-regulation of 3-microRNA signature (miR155, miR181a and miR221) was validated in PDAC samples. The prediction of miRDB showed that the 3-microRNA signature shared four target genes: CREBRF, GABRA1, GPD1L and REPS2. GPD1L was down-regulated in PDAC and associated with poorer prognosis in three independent datasets (GSE21501, GSE28735 and GSE71729). In two PDAC cell lines, the 3-microRNA signature inhibited GPD1L expression through binding its 3'UTR and GPD1L reduction promoted cell proliferation and clone formation, and inhibited apoptosis. Conclusions: GPD1L as a novel target gene for a 3-microRNA signature and GPD1L might be an important therapeutic target in PDAC.

Stressful life events increase aggression and alcohol use in young carriers of the GABRA2 rs279826/rs279858 A-allele

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.

PROSPER Intervention Effects on Adolescents' Alcohol Misuse Vary by GABRA2 Genotype and Age.

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.

Comprehensive association analysis of 27 genes from the GABAergic system in Japanese individuals affected with schizophrenia

Involvement of the gamma-aminobutyric acid (GABA)-ergic system in schizophrenia pathogenesis through disrupted neurodevelopment has been highlighted in numerous studies. However, the function of common genetic variants of this system in determining schizophrenia risk is unknown. We therefore tested the association of 375 tagged SNPs in genes derived from the GABAergic system, such as GABAA receptor subunit genes, and GABA related genes (glutamate decarboxylase genes, GABAergic-marker gene, genes involved in GABA receptor trafficking and scaffolding) in Japanese schizophrenia case-control samples (n=2926; 1415 cases and 1511 controls). We observed nominal association of SNPs in nine GABAA receptor subunit genes and the GPHN gene with schizophrenia, although none survived correction for study-wide multiple testing. Two SNPs located in the GABRA1 gene, rs4263535 (Pallele=0.002; uncorrected) and rs1157122 (Pallele=0.006; uncorrected) showed top hits, followed by rs723432 (Pallele=0.007; uncorrected) in the GPHN gene. All three were significantly associated with schizophrenia and survived gene-wide multiple testing. Haplotypes containing associated variants in GABRA1 but not GPHN were significantly associated with schizophrenia. To conclude, we provided substantiating genetic evidence for the involvement of the GABAergic system in schizophrenia susceptibility. These results warrant further investigations to replicate the association of GABRA1 and GPHN with schizophrenia and to discern the precise mechanisms of disease pathophysiology.

M62 - GABRA2 Association With Addiction-Related Endophenotypes Is Environmentally Influenced

Background The GABRA2 gene contains more than 250 SNPs that in Caucasians form two major common “Yin-Yang” haplotypes - having either all or none of the non-ancestral (NA) alleles. Since 2004, association of the non-ancestral, slightly less common haplotype with alcohol use disorder (AUD) and with increased beta waves in EEG has been reported and replicated many times. Methods In a longitudinal sample of >400 low SES families at high risk for AUD, we investigated the influence of these GABRA2 haplotypes on addiction related endophenotypes, and started to investigate potential functional implications. We found that the NA haplotype is associated with impulsivity and with increased activation of the insula in response to reward expectation, both of which partially mediate the association of the NA alleles with alcoholism. Impulsivity was also associated with reward expectation, independent of genetics. Results Moreover, the effect of parental monitoring on externalizing behavior trajectories across childhood and adolescence, i.e., consistently low, developmentally limited, and rising trajectories, was moderated by the NA alleles of GABRA2. Subjects with the NA alleles were more strongly influenced – both positively and negatively--by the extent of parental monitoring, while subjects with the ancestral alleles were not significantly influenced by the monitoring. In addition to parents, peers are also known to influence addiction-related behaviors such as rule breaking during adolescence. Association with delinquent peers increased rule breaking, particularly in those with NA alleles of GABRA2, while association with peers who displayed positive behaviors (such as religious activity and scholastic competence) decreased externalizing behaviors. Subjects with the ancestral alleles of GABRA2 were less affected by peers. Discussion Our results illustrate a more complex influence of genotypes on risk for common traits such as those associated with addiction. Our data suggest that the previously identified “risk” alleles impacts the strength of both adaptive and maladaptive environmental influences on risky behaviors such as rule breaking, and hence might be thought of as plasticity factors. None of the alleles of the GABRA2 haplotypes change an amino acid, and they have no major influence on level of expression (eQTL) in several large brain expression samples. Allelic imbalance is more sensitive to slight expression differences. Preliminary allelic imbalance RNASeq analyses of brain mRNA suggest that the NA alleles may increase expression. Our result is in contrast to a recent report of decreased expression of the risk alleles in iPSCs. Epigenetic modifications may be one pathway of how environmental influences on behavior are being molecularly mediated, and just as our results demonstrate plasticity at the behavioral level, plasticity may exist on the molecular level, in that expression of GABRA2 haplotypes may be influenced molecularly by different environments.

Wczesnoniemowlęca encefalopatia padaczkowa 19 z dyskinezami uwarunkowana nową mutacją w genie GABRA1 – pierwszy przypadek w polskiej populacji

An early infantile epileptic encephalopathy 19 with dyskinesias due to a new GABRA1 gene mutation – identification of the first case in the Polish population - Agnieszka Oknińska, Hanna Mierzewska, Robert Śmigiel, Małgorzata Rydzanicz, Anna Walczak, Iwona Terczyńska, Jolanta Tryfon, Rafał Płoski, Elżbieta Szczepanik

Sex-Dependent Anti-Stress Effect of an α5 Subunit Containing GABAA Receptor Positive Allosteric Modulator.

Rationale: Current first-line treatments for stress-related disorders such as major depressive disorder (MDD) act on monoaminergic systems and take weeks to achieve a therapeutic effect with poor response and low remission rates. Recent research has implicated the GABAergic system in the pathophysiology of depression, including deficits in interneurons targeting the dendritic compartment of cortical pyramidal cells.Objectives: The present study evaluates whether SH-053-2’F-R-CH3 (denoted “α5-PAM”), a positive allosteric modulator selective for α5-subunit containing GABAA receptors found predominantly on cortical pyramidal cell dendrites, has anti-stress effects.Methods: Female and male C57BL6/J mice were exposed to unpredictable chronic mild stress (UCMS) and treated with α5-PAM acutely (30 min prior to assessing behavior) or chronically before being assessed behaviorally.Results: Acute and chronic α5-PAM treatments produce a pattern of decreased stress-induced behaviors (denoted as “behavioral emotionality”) across various tests in female, but not in male mice. Behavioral Z-scores calculated across a panel of tests designed to best model the range and heterogeneity of human symptomatology confirmed that acute and chronic α5-PAM treatments consistently produce significant decreases in behavioral emotionality in several independent cohorts of females. The behavioral responses to α5-PAM could not be completely accounted for by differences in drug brain disposition between female and male mice. In mice exposed to UCMS, expression of the Gabra5 gene was increased in the frontal cortex after acute treatment and in the hippocampus after chronic treatment with α5-PAM in females only, and these expression changes correlated with behavioral emotionality.Conclusion: We showed that acute and chronic positive modulation of α5 subunit-containing GABAA receptors elicit anti-stress effects in a sex-dependent manner, suggesting novel therapeutic modalities.

Phenotypic spectrum of GABRA1: From generalized epilepsies to severe epileptic encephalopathies.

To delineate phenotypic heterogeneity, we describe the clinical features of a cohort of patients with GABRA1 gene mutations. Patients with GABRA1 mutations were ascertained through an international collaboration. Clinical, EEG, and genetic data were collected. Functional analysis of 4 selected mutations was performed using the Xenopus laevis oocyte expression system. The study included 16 novel probands and 3 additional family members with a disease-causing mutation in the GABRA1 gene. The phenotypic spectrum varied from unspecified epilepsy (1), juvenile myoclonic epilepsy (2), photosensitive idiopathic generalized epilepsy (1), and generalized epilepsy with febrile seizures plus (1) to severe epileptic encephalopathies (11). In the epileptic encephalopathy group, the patients had seizures beginning between the first day of life and 15 months, with a mean of 7 months. Predominant seizure types in all patients were tonic-clonic in 9 participants (56%) and myoclonic seizures in 5 (31%). EEG showed a generalized photoparoxysmal response in 6 patients (37%). Four selected mutations studied functionally revealed a loss of function, without a clear genotype-phenotype correlation. GABRA1 mutations make a significant contribution to the genetic etiology of both benign and severe epilepsy syndromes. Myoclonic and tonic-clonic seizures with pathologic response to photic stimulation are common and shared features in both mild and severe phenotypes.

Assessment of Expression of Genes Coding GABAA Receptors during Chronic and Acute Intoxication of Laboratory Rats with Ethanol.

Expression of genes encoding the individual subunits of ionotropic GABAA receptor was assessed after acute and chronic intoxication of rats with ethanol. The chronic 1-month-long exposure to ethanol signifi cantly decreased (by 38%) expression of Gabrb1 gene in the hippocampus. Acute exposure to ethanol elevated expression of genes Gabrb1 (by 1.7 times), Gabra1 (by 3.8 times), and Gabra4 (by 6.5 times), although it diminished expression of Gabra2 gene by 1.4 times. In preliminarily alcoholized rats, acute intoxication with ethanol enhanced expression of genes Gabrb1 and Gabra5 by 1.7 and 8.7 times, respectively. There was neither acute nor chronic effect of ethanol on expression of gene Gabra3.

Thyrotoxic Periodic Paralysis and Polymorphisms of the ADRB2, AR, and GABRA3 Genes in Men with Graves Disease.

BackgroundThyrotoxic periodic paralysis (TPP) is a rare complication of thyrotoxicosis characterized by acute attacks of muscle weakness and hypokalemia. Recently, variation in several genes was suggested to be associated with TPP. This study evaluated the genetic predisposition to TPP in terms of the β2-adrenergic receptor (ADRB2), androgen receptor (AR), and γ-aminobutyric acid receptor α3 subunit (GABRA3) genes.MethodsThis study enrolled 48 men with Graves disease (GD) and TPP, and 48 GD patients without TPP. We compared the frequencies of candidate polymorphisms between the two groups.ResultsThe frequency of the Gly16/Gly16 genotype in ADRB2 was not significantly associated with TPP (P=0.32). More CAG repeats (≥26) in the AR gene were not correlated with TPP (odds ratio [OR], 2.46; 95% confidence interval [CI], 0.81 to 8.09; P=0.08). The allele frequency of the TT genotype in the GABRA3 gene was not associated with TPP (OR, 1.83; 95% CI, 0.54 to 6.74; P=0.41).ConclusionThe polymorphisms in the ADRB2, AR, and GABRA3 genes could not explain the genetic susceptibility to TPP in Korean men with GD.

Motivational Effects of Methylphenidate are Associated with GABRA2 Variants Conferring Addiction Risk.

Background: Variations in the GABRA2 gene, encoding α2 subunits of GABAA receptors, have been associated with risk for addiction to several drugs, but the mechanisms by which variations in non-coding regions of GABRA2 increase risk for addictions are not understood. Mice with deletion of GABRA2 show deficits in the ability of psychostimulants to facilitate responding for conditioned reinforcers, offering a potential explanation.Methods: We report human and mouse studies investigating a potential endophenotype underlying this association. Healthy human volunteers carrying either cocaine-addiction “risk” or “protective” GABRA2 single nucleotide polymorphism (SNPs) were tested for their subjective responses to methylphenidate, and methylphenidate’s ability to facilitate conditioned reinforcement (CRf) for visual stimuli (CS+) associated with monetary reward. In parallel, methylphenidate’s ability to facilitate responding for a visual CRf was studied in wildtype and α2 knockout (α2−/−) mice.Results: Methylphenidate increased the number of CS+ presentations obtained by human subjects carrying protective, but not risk SNPs. In mice, methylphenidate increased responding for a CS+ in wildtype, but not α2−/− mice. Human subjects carrying protective SNPs felt stimulated, aroused and restless following methylphenidate, while individuals carrying risk SNPs did not.Conclusion: Human risk SNP carriers were insensitive to methylphenidate’s effects on mood or in facilitating CRf. That mice with the gene deletion were also insensitive to methylphenidate’s ability to increase responding for CRf, suggests a potential mechanism whereby low α2-subunit levels increase risk for addictions. Circuits employing GABAA-α2 subunit-containing receptors may protect against risk for addictions.

Diagnostic value of array-based single nucleotide polymorphisms comparative genomic hybridization in Angelman syndrome

Objective To analyze the genotype-phenotype correlations of Angelman syndrome(AS), and to discuss the advantage of applying array-based single nucleotide polymorphisms comparative genomic hybridization(SNP aCGH)in diagnosis of AS. Methods Examination of electroencephalogram(EEG)and intelligence quotient(IQ) evaluation were done for 11 cases diagnosed as AS clinically.Gesell scares were chosen as the evaluation criterion of IQ.The screening techniques was methylation polymerase chain reaction(MS-PCR), then SNP aCGH was used to make genetic diagnosis. Results (1)Eleven cases of AS were confirmed: 1 case had UPD(uniparental disomy), 10 cases were type of deletion, from which 6 cases were deletion(Ⅱ), 4 cases were deletion(Ⅰ). (2)The copy number variations were detected in the region of 15q11-q13, which contained genes like MKRN3, MAGEL2, NDN, SNRPN, SNURF, GABRB3, GABRA5, GABRG3, UBE3A, OCA2, ATP10A.To search online Mendelian inheritance in man, genes above were correlated with AS manifestation.(3)All cases of deletion were 3-5 standard deviation(SD) in weight and height to normal children at the same age and with the same sex, while UPD was below 1.5 SD.Gesell scares showed that the deletion(Ⅰ) was the most serious in mental retardation, deletion(Ⅱ) was moderate, and the UPD was mild.Eight cases were hypopigmentation, and one was the UPD.EEG revealed that 1 case of deletion(Ⅰ) and the UPD were spike occasionally, another one deletion(Ⅰ) was limit EEG.The rest cases displayed slow and spike waves paroxysmally, with amplitude of medium or high, 2.5-3.0 Hz. Conclusions Not only can SNP aCGH make a diagnosis of AS but discriminate the types of genetic pathology.Since different type contributes to a diverse of clinical features and the rate of recurrence is also different, it is significant for family genetic consultation.Moreover, the technology is advantageous for the study on the pathogenesis and gene function. Key words: Array-based single nucleotide polymorphisms comparative genomic hybridization; Angelman syndrome; Genotype; Phenotype

Role of gabra2, GABAA receptor alpha-2 subunit, in CNS development

gabra2 gene codes for the alpha-2 subunit of the GABAA receptor, one of the ionotropic receptors which has been related to anxiety, depression and other behavioural disorders, including drug dependence and schizophrenia. GABAergic signalling also plays a role during development, by promoting neural stem cell maintenance and renewal. To investigate the role of gabra2 in CNS development, gabra2 deficient zebrafish were generated. The pattern of proliferation during the embryonic development was disrupted in morphant embryos, which also displayed an increase in the number of apoptotic nuclei mainly at the mid- and hindbrain regions. The expression of several genes (notch1, pax2, fgf8 and wnt1) known to contribute to the development of the central nervous system was also affected in gabra2 morpholino-injected embryos, although no changes were found for pax6a and shh a expression. The transcriptional activity of neuroD (a proneural gene involved in early neuronal determination) was down-regulated in gabra2 deficient embryos, and the expression pattern of gad1b (GABA-synthesising enzyme GAD67) was clearly reduced in injected fish. I propose that gabra2 might be interacting with those signalling pathways that regulate proliferation, differentiation and neurogenesis during the embryonic development; thus, gabra2 might be playing a role in the differentiation of the mesencephalon and cerebellum. Given that changes in GABAergic circuits during development have been related to several psychiatric disorders, such as autism and schizophrenia, this work might be helpful to understand the role of neurotransmitter systems during CNS development and to assess the developmental effects of several GABAergic drugs.

Association of GABAA receptor α2 subunit gene (GABRA2) with alcohol dependence-related aggressive behavior.

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 GABAA receptor α2 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.

ABCB1, ABCC2, SCN1A, SCN2A, GABRA1 gene polymorphisms and drug resistant epilepsy in the Chinese Han population.

Drug resistance is common in epilepsy despite multiple available medications. Single nucleotide polymorphisms (SNP) may influence drug efficacy in epilepsy. We therefore aimed to clarify the association between polymorphisms of several controversial SNP loci and drug resistance in Chinese Han epilepsy patients from central China. Among all the 391 recruited subjects, 235 and 156 patients were classified into a drug responsive and resistant group, respectively, according to the definition of drug resistance proposed by the International League Against Epilepsy. The candidate SNP loci, including ATP-binding cassette (ABC) subfamily gene ABCB1 rs2032582 and rs1045642; ABC subfamily gene ABCC2 rs717620 and rs2273697; sodium channel subunit gene SCN1A rs3812718, SCN2A rs2304016; γ-amino butyric acid type A (GABAA) receptor subunit subtype gene GABRA1 rs2279020 were genotyped following the Illumina protocols. There were no significant differences in allelic or genotypic frequencies between the drug responsive and resistant patients. The polymorphisms of the above SNP loci may not be associated with drug resistance of epilepsy in the Chinese Han population.