Association analysis of GABRB3 promoter variants with heroin dependence

Association study of genetic polymorphisms in GABRD with treatment response and dose in methadone maintenance treatment

Aim: This study determined if gene variants in the GABA receptor delta subunit (GABRD) are associated with treatment response and dose in methadone maintenance treatment (MMT) for heroin addiction. Materials & methods: A total of 286 MMT patients were recruited and divided into response and nonresponse groups based on retention time in therapy. A total of 177 responders were classified into low dose and high dose subgroups according to the stabilized methadone dose. Four (single nucleotide polymorphisms) SNPs (rs13303344, rs4481796, rs2376805 and rs2229110) in GABRD were genotyped using the TaqMan SNP assay. Logistic regression was used to assess the genetic effects of the SNPs in MMT. Results: No significant associations were observed between the SNPs and treatment response or dose, except the frequency of haplotype ACGC at the four SNPs significantly differed between responders and nonresponders. Conclusion: The results indicated that GABRD variants may play a small role in modulating methadone treatment response.

Identification of a sex-stratified genetic algorithm for opioid addiction risk

The opioid epidemic has had a devastating impact on our country, with wide-ranging effects on healthcare, corrections, employment, and social systems. Programs have been put in place for monitoring prescriptions, initiating and expanding medications for opioid use disorder, and harm reduction (i.e., naloxone distribution, needle exchanges). However, opportunities for personalization of opioid therapy based on addiction risk have been limited. The goal of the present study was to develop an objective risk assessment algorithm based on genetic markers that are correlated with opioid use disorder (OUD). A total of 180 single-nucleotide polymorphisms (SNPs) were tested in patients with and without OUD. SNPs selected for testing were associated with opioid metabolism and drug reward pathways based on previous studies. Of the 394 patients recruited, 200 had OUD and 194 served as controls without OUD but with prior opioid exposure. Logistic regression analyses stratified by sex identified ten unique SNPs in females and nine unique SNPs in males that were significantly associated with OUD. A Genetics Opioid Risk Score (GenORs) was calculated by counting the number of OUD risk-associated SNPs/genotypes for each patient. To evaluate the discrimination of the GenORs, a receiver operating characteristic (ROC) curve for each sex was generated and determined to be sensitive and specific. This represents the first published example of a sex-based genetic risk score with potential to predict OUD, and the first OUD algorithm to include opioid-associated pharmacokinetic genes.

Transcriptional Regulation of Channelopathies in Genetic and Acquired Epilepsies

Epilepsy is a common neurological disorder characterized by recurrent uncontrolled seizures and has an idiopathic “genetic” etiology or a symptomatic “acquired” component. Genetic studies have revealed that many epilepsy susceptibility genes encode ion channels, including voltage-gated sodium, potassium and calcium channels. The high prevalence of ion channels in epilepsy pathogenesis led to the causative concept of “ion channelopathies,” which can be elicited by specific mutations in the coding or promoter regions of genes in genetic epilepsies. Intriguingly, expression changes of the same ion channel genes by augmentation of specific transcription factors (TFs) early after an insult can underlie acquired epilepsies. In this study, we review how the transcriptional regulation of ion channels in both genetic and acquired epilepsies can be controlled, and compare these epilepsy “ion channelopathies” with other neurodevelopmental disorders.

Functional analysis of haplotypes and promoter activity at the 5' region of the human GABRB3 gene and associations with schizophrenia

Background

This study investigated the effects of haplotypes T‐G and C‐A derived from NG_012836.1:g.4160T>C and NG_012836.1:g.4326G>A on protein expression levels in vitro and identified the functional sequence in the regulatory region of the GABRB3 gene linked to possible associations with schizophrenia.

Methods

Recombinant plasmids with haplotypes T‐G and C‐A and 10 recombinant vectors containing deletion fragments from the GABRB3 gene 5′ regulatory region were transfected into HEK‐293, SK‐N‐SH, and SH‐SY5Y cells. The relative fluorescence intensity of the two haplotypes and different sequences was compared using a dual luciferase reporter assay system.

Results

The relative fluorescence intensity of haplotype C‐A was significantly lower than that of T‐G. We shortened the core promoter sequence of the GABRB3 gene 5′ regulation region from −177 bp to −18 bp (ATG+1). We also found an expression suppression region from −1,735 bp to −1,638 bp and an enhanced regulatory region from −1,638 bp to −1,335 bp. Multiple inhibitory functional elements were identified in the region from −680 bp to −177 bp.

Conclusion

We demonstrated that haplotype C‐A might increase the risk of schizophrenia and found multiple regulatory regions that had an effect on GABRB3 receptor expression.

Effect of subchronic exposure to opioids on the effective dose of intravenous and inhalation anaesthetics

This study aimed to investigate the effect of subchronic exposure to morphine on the 50% effective dose (EC50) (median effective concentration/EC50) values of intravenous (propofol and ketamine) and inhalation (sevoflurane) anaesthetics in mice. Eight to 12-week-old male mice were administered morphine subcutaneously for 5 days to create a subchronic morphine exposure model. Control mice were injected with saline. The EC50 for righting reflex loss and tail clip reflex of general anaesthetics on the first (D1), third (D3) and seventh days (D7), after establishing a subchronic morphine exposure model, were determined. Sevoflurane: No change in the minimum alveolar concentration for righting reflex loss or tail clip reflex loss was observed between the treated and the control values (P>0.05). Propofol: the EC50 for righting reflex loss of D7 was significantly lower than the control and D1 (P<0.05). The EC50 for tail clip reflex loss of D3 and D7 decreased compared with the control (P<0.05). Ketamine: the EC50 for righting reflex loss of D3 and D7 was significantly higher than that of the controls. The EC50 for tail clip reflex loss at D1, D3 and D7 increased compared with the control (P<0.05). In summary, after subchronic exposure to morphine, the minimum alveolar concentration value of sevoflurane did not change significantly; the EC50 of propofol decreased, whereas the EC50 of ketamine increased. The changes induced by subchronic exposure to morphine can alter the response to anaesthetics, and the effects vary with the modes of action of anaesthetics.

The GABRB3 Polymorphism and its Association with Schizophrenia

The aim of this study was to explore whether schizophrenia occurrence is associated with polymorphisms in the 5' regulatory region of GABRB3 (gamma-aminobutyric acid type A receptor beta 3, subunit gene). The study included 324 patients with schizophrenia and 327 unaffected participants; all individuals were northern Han Chinese. Genotype and haplotype frequency distributions were compared for the 2 groups by means of PCR amplification and direct sequencing of the promoter region of GABRB3. The genotype distribution among control participants was in accordance with the Hardy-Weinberg equilibrium. Five common single-nucleotide polymorphism (SNP) sites were detected in the 5' promoter region of GABRB3: rs4243768, rs7171660, rs4363842, rs4906902, and rs8179184. Only rs8179184 and rs4906902 differed significantly in frequency between controls and cases (P < 0.05); this difference remained significant when only women in each group were compared. The 2 SNP sites showed linkage disequilibrium, resulting in 2 haplotypes: T-G and C-A. The frequency of C-A was significantly higher among patients with schizophrenia than among controls. Our findings suggest that rs4906902 and rs8179184 in the 5' promoter region of GABRB3 are associated with schizophrenia. The C-A haplotype may entail an increased risk of schizophrenia, and the onset of schizophrenia may be gender-specific.

Glutamatergic and GABAergic susceptibility loci for heroin and cocaine addiction in subjects of African and European ancestry

BACKGROUND

Drug addiction, a leading health problem, is a chronic brain disease with a significant genetic component. Animal models and clinical studies established the involvement of glutamate and GABA neurotransmission in drug addiction. This study was designed to assess if 258 variants in 27 genes of these systems contribute to the vulnerability to develop drug addiction.

METHODS

Four independent analyses were conducted in a sample of 1860 subjects divided according to drug of abuse (heroin or cocaine) and ancestry (African and European).

RESULTS

A total of 11 SNPs in eight genes showed nominally significant associations (P<0.01) with heroin and/or cocaine addiction in one or both ancestral groups but the associations did not survive correction for multiple testing. Of these SNPs, the GAD1 upstream SNP rs1978340 is potentially functional as it was shown to affect GABA concentrations in the cingulate cortex. In addition, SNPs GABRB3 rs7165224; DBI rs12613135; GAD1 SNPs rs2058725, rs1978340, rs2241164; and GRIN2A rs1650420 were previously reported in associations with drug addiction or related phenotypes.

CONCLUSIONS

The study supports the involvement of genetic variation in the glutamatergic and GABAergic systems in drug addiction with partial overlap in susceptibility loci between cocaine and heroin addiction.