A Population-Based Study of Four Genes Associated with Heroin Addiction in Han Chinese

The Role of 3' Regulatory Region Flanking Kinectin 1 Gene in Schizophrenia

Objective

Schizophrenia is often associated with volumetric reductions in cortices and expansions in basal ganglia, particularly the putamen. Recent genome-wide association studies have highlighted the significance of variants in the 3' regulatory region adjacent to the kinectin 1 gene (KTN1) in regulating gray matter volume (GMV) of the putamen. This study aimed to comprehensively investigate the involvement of this region in schizophrenia.

Methods

We analyzed 1136 single-nucleotide polymorphisms (SNPs) covering the entire 3' regulatory region in 4 independent dbGaP samples (4604 schizophrenia patients vs. 4884 healthy subjects) and 3 independent Psychiatric Genomics Consortium samples (107 240 cases vs. 210 203 controls) to identify consistent associations. Additionally, we examined the regulatory effects of schizophrenia-associated alleles on KTN1 mRNA expression in 16 brain areas among 348 subjects, as well as GMVs of 7 subcortical nuclei in 38 258 subjects, and surface areas (SA) and thickness (TH) of the entire cortex and 34 cortical areas in 36 936 subjects.

Results

The major alleles (f > 0.5) of 25 variants increased (β > 0) the risk of schizophrenia across 2 to 5 independent samples (8.4 × 10-4 ≤ P ≤ .049). These schizophrenia-associated alleles significantly elevated (β > 0) GMVs of basal ganglia, including the putamen (6.0 × 10-11 ≤ P ≤ 1.1 × 10-4), caudate (8.7 × 10-4 ≤ P ≤ 9.4 × 10-3), pallidum (P = 6.0 × 10-4), and nucleus accumbens (P = 2.7 × 10-5). Moreover, they potentially augmented (β > 0) the SA of posterior cingulate and insular cortices, as well as the TH of frontal (pars triangularis and medial orbitofrontal), parietal (superior, precuneus, and inferior), and temporal (transverse) cortices, but potentially reduced (β < 0) the SA of the whole, frontal (medial orbitofrontal), and temporal (pole, superior, middle, and entorhinal) cortices, as well as the TH of rostral middle frontal and superior frontal cortices (8.9 × 10-4 ≤ P ≤ .050).

Conclusion

Our findings identify significant and functionally relevant risk alleles in the 3' regulatory region adjacent to KTN1, implicating their crucial roles in the development of schizophrenia.

Single Nucleotide Variants (SNVs) of the Mesocorticolimbic System Associated with Cardiovascular Diseases and Type 2 Diabetes: A Systematic Review

The mesocorticolimbic (MCL) system is crucial in developing risky health behaviors which lead to cardiovascular diseases (CVDs) and type 2 diabetes (T2D). Although there is some knowledge of the MCL system genes linked to CVDs and T2D, a comprehensive list is lacking, underscoring the significance of this review. This systematic review followed PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. The PubMed and Web of Science databases were searched intensively for articles related to the MCL system, single nucleotide variants (SNVs, formerly single nucleotide polymorphisms, SNPs), CVDs, T2D, and associated risk factors. Included studies had to involve a genotype with at least one MCL system gene (with an identified SNV) for all participants and the analysis of its link to CVDs, T2D, or associated risk factors. The quality assessment of the included studies was performed using the Q-Genie tool. The VEP and DAVID tools were used to annotate and interpret genetic variants and identify enriched pathways and gene ontology terms associated with the gene list. The review identified 77 articles that met the inclusion criteria. These articles provided information on 174 SNVs related to the MCL system that were linked to CVDs, T2D, or associated risk factors. The COMT gene was found to be significantly related to hypertension, dyslipidemia, insulin resistance, obesity, and drug abuse, with rs4680 being the most commonly reported variant. This systematic review found a strong association between the MCL system and the risk of developing CVDs and T2D, suggesting that identifying genetic variations related to this system could help with disease prevention and treatment strategies.

A significant, functional and replicable risk KTN1 variant block for schizophrenia

Cortical and subcortical structural alteration has been extensively reported in schizophrenia, including the unusual expansion of gray matter volumes (GMVs) of basal ganglia (BG), especially putamen. Previous genome-wide association studies pinpointed kinectin 1 gene (KTN1) as the most significant gene regulating the GMV of putamen. In this study, the role of KTN1 variants in risk and pathogenesis of schizophrenia was explored. A dense set of SNPs (n = 849) covering entire KTN1 was analyzed in three independent European- or African-American samples (n = 6704) and one mixed European and Asian Psychiatric Genomics Consortium sample (n = 56,418 cases vs. 78,818 controls), to identify replicable SNP-schizophrenia associations. The regulatory effects of schizophrenia-associated variants on the KTN1 mRNA expression in 16 cortical or subcortical regions in two European cohorts (n = 138 and 210, respectively), the total intracranial volume (ICV) in 46 European cohorts (n = 18,713), the GMVs of seven subcortical structures in 50 European cohorts (n = 38,258), and the surface areas (SA) and thickness (TH) of whole cortex and 34 cortical regions in 50 European cohorts (n = 33,992) and eight non-European cohorts (n = 2944) were carefully explored. We found that across entire KTN1, only 26 SNPs within the same block (r2 > 0.85) were associated with schizophrenia across ≥ 2 independent samples (7.5 × 10-5 ≤ p ≤ 0.048). The schizophrenia-risk alleles, which increased significantly risk for schizophrenia in Europeans (q < 0.05), were all minor alleles (f < 0.5), consistently increased (1) the KTN1 mRNA expression in 12 brain regions significantly (5.9 × 10-12 ≤ p ≤ 0.050; q < 0.05), (2) the ICV significantly (6.1 × 10-4 ≤ p ≤ 0.008; q < 0.05), (3) the SA of whole (9.6 × 10-3 ≤ p ≤ 0.047) and two regional cortices potentially (2.5 × 10-3 ≤ p ≤ 0.042; q > 0.05), and (4) the TH of eight regional cortices potentially (0.006 ≤ p ≤ 0.050; q > 0.05), and consistently decreased (1) the BG GMVs significantly (1.8 × 10-19 ≤ p ≤ 0.050; q < 0.05), especially putamen GMV (1.8 × 10-19 ≤ p ≤ 1.0 × 10-4; q < 0.05, (2) the SA of four regional cortices potentially (0.010 ≤ p ≤ 0.048), and (3) the TH of four regional cortices potentially (0.015 ≤ p ≤ 0.049) in Europeans. We concluded that we identified a significant, functional, and robust risk variant block covering entire KTN1 that might play a critical role in the risk and pathogenesis of schizophrenia.

Effects of PPARD gene variants on the therapeutic responses to exenatide in chinese patients with type 2 diabetes mellitus

BACKGROUND

Exenatide is a GLP-1R agonist that often exhibits considerable interindividual variability in therapeutic efficacy. However, there is no evidence about the impact of genetic variants in the PPARD on the therapeutic efficacy of exenatide. This research was aimed to explore the influence of PPARD gene polymorphism on the therapeutic effect of exenatide, and to identify the potential mechanism futher.

METHODS

A total of 300 patients with T2DM and 200 control subjects were enrolled to identify PPARD rs2016520 and rs3777744 genotypes. A prospective clinical study was used to collect clinical indicators and peripheral blood of T2DM patients treated with exenatide monotherapy for 6 months. The SNaPshot method was used to identify PPARD rs2016520 and rs3777744 genotypes, and then we performed correlation analysis between PPARD gene variants and the efficacy of exenatide, and conducted multiple linear regression analysis of factors affecting the therapeutic effect of exenatide. HepG2 cells were incubated with exenatide in the absence or presence of a PPARδ agonist or the siPPARδ plasmid, after which the levels of GLP-1R and the ratio of glucose uptake were determined.

RESULTS

After 6 months exenatide monotherapy, we observed that homeostasis model assessment for insulin resistance (HOMA-IR) levels of the subjects with at least one C allele of the PPARD rs2016520 were significantly lower than those with the TT genotype, which suggested that the PPARD rs2016520 TT genotype conferred the poor exenatide response through a reduction of insulin resistance, as measured by HOMA-IR. The carriers of G alleles at rs3777744 exhibited higher levels of in waist to hip ratio (WHR), fasting plasma glucose (FPG), hemoglobin A1c (HbA1c) and HOMA-IR compared to individuals with the AA genotype following 6 months of exenatide treatment, potentially accounting for the lower failure rate of exenatide therapy among the AA homozygotes. In an insulin resistant HepG2 cell model, the PPARδ agonists enhanced exenatide efficacy on insulin resistance, with the expression of GLP-1R being up-regulated markedly.

CONCLUSION

These data suggest that the PPARD rs2016520 and rs3777744 polymorphisms are associated with exenatide monotherapy efficacy, due to the pivotal role of PPARδ in regulating insulin resistance through affecting the expression of GLP-1R. This study was registered in the Chinese Clinical Trial Register (No. ChiCTR-CCC13003536).

Elevation of DNA Methylation in the Promoter Regions of the Brain-Derived Neurotrophic Factor Gene is Associated with Heroin Addiction

To study the potential role of brain-derived neurotrophic factor (BDNF) methylation in heroin addiction, we first detected the methylation level of seven CpG islands that included 106 CpG sites in the promoter regions of BDNF from 120 people addicted to heroin and 113 controls. Methylation quantitative trait locus (mQTL) analysis was then employed to determine the association between the single-nucleotide polymorphism rs6265, a well-known locus shown to be correlated with heroin addiction, and the methylation levels of these CpG sites. Finally, we used the JASPAR database to predict whether transcription factors could bind to these CpG sites. We found that the methylation levels of CpG islands 6 and 7 and the methylation levels of BDNF_45 and BDNF_80 were significantly higher in the heroin addiction group than in the control group. We also found that rs6265 was an mQTL and was associated with the methylation level of BDNF_58. Using the JASPAR database, we found that ALX homeobox 3 (ALX3), achaete-scute family bHLH transcription factor 1 (ASCL1) and aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) could bind to CpG island 6, and ALX3 could bind to CpG island 7. In summary, we showed that increased DNA methylation in the promoter regions of the BDNF gene was associated with heroin addiction in Han Chinese.

Significant, replicable, and functional associations between KTN1 variants and alcohol and drug codependence

The gray matter volume (GMV) of the putamen has been reported to be regulated by kinectin 1 gene (KTN1). As a hub of the dopaminergic circuit, the putamen is widely implicated in the etiological processes of substance use disorders (SUD). Here, we aimed to identify robust and reliable associations between KTN1 SNPs and SUD across multiple samples. We examined the associations between SUD and KTN1 SNPs in four independent population-based or family-based samples (n = 10,209). The potential regulatory effects of the risk alleles on the putamen GMVs, the effects of alcohol, nicotine, marijuana and cocaine on KTN1 mRNA expression, and the relationship between KTN1 mRNA expression and SUD were explored. We found that a total of 23 SNPs were associated with SUD across at least two independent samples (1.4 × 10-4 ≤ p ≤ 0.049), including one SNP (rs12895072) across three samples (8.8 × 10-3 ≤ p ≤ 0.049). Four other SNPs were significantly or suggestively associated with SUD only in European-Australians (4.8 × 10-4 ≤ p ≤ 0.058). All of the SUD-risk alleles of these 27 SNPs increased (β > 0) the putamen GMVs and represented major alleles (f > 0.5) in Europeans. Twenty-two SNPs were potentially biologically functional. Alcohol, nicotine and cocaine significantly affected the KTN1 mRNA expression, and the KTN1 mRNA was differentially expressed between nicotine or cocaine dependent and control subjects. We concluded that there was a replicable and robust relationship among the KTN1 variants, KTN1 mRNA expression, putamen GMVs, molecular effects of substances, and SUD, suggesting that some risk KTN1 alleles might increase kinectin 1 expression in the putamen, altering putamen structures and functions, and leading to SUD.

Association study of Catechol-o-methyltransferase and Alpha-1-adrenergic receptor gene polymorphisms with multiple phenotypes of heroin use disorder

Heroin use disorder is a chronic relapsing brain disease containing multiple phenotypes. These phenotypes vary among heroin users and might be influenced by genetic factors. Single-nucleotide polymorphisms (SNPs) of catechol-O-methyltransferase (COMT) and alpha-1-adrenergic receptor (ADRA1A) genes are associated with heroin use disorder. However, it has not been clarified which phenotypes of heroin use disorder are related to these genes. To address this question, we recruited 801 unrelated heroin users and divided them into different subgroups according to four important phenotypes of heroin use disorder. Then 7 SNPs in the functional region of these genes were systematically screened and genotyped using a SNaPshot assay. We found that the A allele of ADRA1A rs1048101 was associated with a shorter duration of transition from first use to addiction. Subjects with the C allele of ADRA1A rs3808585 were more susceptible to memory impairment after heroin use disorder. Subjects with the G allele of COMT rs769224 were more likely to take a higher dose of heroin every day. Our study confirmed the association between polymorphisms of COMT and ADRA1A with those specific phenotypes of heroin use disorder, which will be instructive for the precise treatment of the disease.

Association studies of dopamine synthesis and metabolism genes with multiple phenotypes of heroin dependence

BACKGROUND

Heroin dependence is a complex disease with multiple phenotypes. Classification of heroin users into more homogeneous subgroups on the basis of these phenotypes could help to identify the involved genetic factors and precise treatments. This study aimed to identify the association between genetic polymorphisms of DA synthesis and metabolism genes, including tyrosine hydroxylase (TH), DOPA decarboxylase (DDC), solute carrier family 6 member 3 (SLC6A3) and DA beta-hydroxylase (DBH), with six important phenotypes of heroin dependence.

METHODS

A total of 801 heroin dependent patients were recruited and fourteen potential functional single nucleotide polymorphisms (SNPs) were genotyped by SNaPshot. Associations between SNPs with six phenotypes were mainly assessed by binary logistic regression. Generalized multifactor dimensionality reduction was used to analyze the gene-by-gene and gene-by-environment interactions.

RESULTS

We found that DBH rs1611114 TT genotype had a protective effect on memory impairment after heroin dependence (P = 0.002, OR = 0.610). We also found that the income-rs12666409-rs129915-rs1611114 interaction yielded the highest testing balance accuracy and cross-validation consistency for memory change after heroin dependence.

CONCLUSIONS

Our results suggest that the memory change after heroin dependence was a result of a combination of genetics and environment. This finding could lead to a better understanding of heroin dependence and further improve personalized treatment.

KTN1 Variants Underlying Putamen Gray Matter Volumes and Parkinson's Disease

Background

Selective loss of dopaminergic neurons and diminished putamen gray matter volume (GMV) represents a central feature of Parkinson’s disease (PD). Recent studies have reported specific effects of kinectin 1 gene (KTN1) variants on the putamen GMV.

Objective

To examine the relationship of KTN1 variants, KTN1 mRNA expression in the putamen and substantia nigra pars compacta (SNc), putamen GMV, and PD.

Methods

We examined the associations between PD and a total of 1847 imputed KTN1 single nucleotide polymorphisms (SNPs) in one discovery sample [2,000 subjects with PD vs. 1,986 healthy controls (HC)], and confirmed the nominally significant associations (p < 0.05) in two replication samples (900 PD vs. 867 HC, and 940 PD vs. 801 HC, respectively). The regulatory effects of risk variants on the KTN1 mRNA expression in putamen and SNc and the putamen GMV were tested. We also quantified the expression levels of KTN1 mRNA in the putamen and/or SNc for comparison between PD and HC in five independent cohorts.

Results

Six replicable and two non-replicable KTN1-PD associations were identified (0.009 ≤ p ≤ 0.049). The major alleles of five SNPs, including rs12880292, rs8017172, rs17253792, rs945270, and rs4144657, significantly increased risk for PD (0.020 ≤ p ≤ 0.049) and putamen GMVs (19.08 ≤ β ≤ 60.38; 2.82 ≤ Z ≤ 15.03; 5.0 × 10^–51 ≤ p ≤ 0.018). The risk alleles of five SNPs, including rs8017172, rs17253792, rs945270, rs4144657, and rs1188184 also significantly increased the KTN1 mRNA expression in the putamen or SNc (0.021 ≤ p ≤ 0.046). The KTN1 mRNA was abundant in the putamen and/or SNc across five independent cohorts and differentially expressed in the SNc between PD and HC in one cohort (p = 0.047).

Conclusion

There was a consistent, significant, replicable, and robust positive relationship among the KTN1 variants, PD risk, KTN1 mRNA expression in putamen, and putamen volumes, and a modest relation between PD risk and KTN1 mRNA expression in SNc, suggesting that KTN1 may play a functional role in the development of PD.

microRNA-422a Inhibits DCC Expression in a Manner Dependent on SNP rs12607853

DCC netrin 1 receptor (DCC) affects the structure and function of the dopamine circuitry, which in turn affects the susceptibility to developing addiction. In a previous study, we found that single nucleotide polymorphism (SNP) rs12607853 in the 3' untranslated region (3'-UTR) of DCC was significantly associated with heroin addiction. In the current study, we first used bioinformatics prediction to identify the DCC rs12607853 C allele as a potential hsa-miR-422a and hsa-miR-378c target site. We then used vector construction and dual-luciferase reporter assays to investigate the targeting relationship of DCC rs12607853 with hsa-miR-422a and hsa-miR-378c. The dual-luciferase reporter gene assay confirmed that the C allele of rs12607853 in combination with hsa-miR-422a led to repressed dual-luciferase gene expression. Moreover, gene expression assays disclosed that hsa-miR-422a inhibited DCC expression at both the mRNA and protein levels. We also found that morphine inhibited the expression of hsa-miR-422a but increased the expression of DCC mRNA, and this change in the expression of hsa-miR-422a could not be reversed by naloxone, which suggested that the role of DCC in opioid addiction might be regulated by hsa-miR-422a. In summary, this study improves our understanding of the role of hsa-miR-422a and identifies the genetic basis of rs12607853, which might contribute to the discovery of new biomarkers or therapeutic targets for opioid addiction.