DRD2 Single Nucleotide Polymorphisms Research Articles

Sex-Specific Modulation of Renal Dopamine Receptor Expression by DRD2 Single-Nucleotide Polymorphisms (SNPs) and Hormonal Factors

Sex-Specific Modulation of Renal Dopamine Receptor Expression by DRD2 Single-Nucleotide Polymorphisms (SNPs) and Hormonal Factors

Interaction of Sex Hormones and Dopamine D2 Receptor Polymorphisms in Human Renal Proximal Tubule Cells

The renal inflammatory response can be modulated by the dopamine D2 receptor (D2R) subtype. The DRD2 gene is highly polymorphic in humans, and single nucleotide polymorphisms (SNPs), such as rs6276 and rs6277 ( DRD2 SNPs), decrease its expression and function. We hypothesized that the response of human renal proximal tubular cells (hRPTCs) to hormones in the culture medium differs by sex and DRD2 SNPs, leading to differences in the inflammatory response. We determined the effects of dihydrotestosterone (DHT) and estradiol (ES) on hRPTCs genotyped for the presence or absence of DRD2 SNPs. We studied four cell lines from males (M) and females (F) with wild-type (WT) DRD2 (M- DRD2 WT and F- DRD2 WT) and DRD2 SNPs (M- DRD2 SNPs and F- DRD2 SNPs). The cells were cultured in a medium containing charcoal-stripped fetal bovine serum (FBS) for 24 hours, without (control group, CG) and with dihydrotestosterone (DHT, 5 nM) or estradiol (ES, 20 nM). We quantified the renal protein expression (protein of interest/GAPDH) of proinflammatory and profibrotic factors and markers of injury and proliferation. DHT decreased the expression of transforming growth factor (TGF-β) by ≍50% in both M- DRD2 WT (0.4±0.1 vs. 1.0±0.2) and M- DRD2 SNPs (1.0±0.1 vs. 1.6±0.1) (n=5-6, p<0.05). However, there was no significant effect of DHT or ES on the expression of TGF-β in F- DRD2 WT and F- DRD2 SNPs. DHT did not affect the fibronectin 1 (FN1) expression in M- DRD2 WT and M- DRD2 SNPs. In F- DRD2 WT, DHT did not affect FN1 expression but decreased in F- DRD2 SNPs (0.9±0.1 vs. 1.7±0.1, n=6, p<0.05). Similar to DHT, ES did not affect FN1 expression in M- DRD2 WT. However, ES decreased FN1 by 50% in M- DRD2 SNPs (0.5±0.1 vs. 1.1±0.1, n=6, p<0.05). Similar to the studies in males, ES did not affect FN1 expression in F- DRD2 WT but also decreased FN1 (1.0±0.1 vs. 1.7±0.1, n=6, p<0.05) in F-DRD2 SNPs. Neither DHT nor ES affected the expression of Kidney Injury Molecule-1 (KIM-1) in M- DRD2 WT. However, in M- DRD2 SNPs, both DHT and ES decreased KIM-1 (1.4±0.2 vs. 1.8±0.2 and 1.1±0.1 vs. 1.8±0.2, respectively; n=5, p<0.05). Unlike in M- DRD2-WT, in F- DRD2 WT, ES increased KIM-1 expression (1.0±0.2 vs. 0.52±0.05, n=5, p<0.05), while DHT had no significant effect. Unlike in M- DRD2 SNPs, where both DHT and ES decreased KIM-1, in F- DRD2 SNPs, neither DHT nor ES affected KIM-1. DHT did not affect the expression of Ki67 in M- DRD2 WT. However, in M- DRD2 SNPs, DHT decreased Ki67 expression (0.60±0.08 vs. 1.6±0.2, n=6, p<0.05). Similar to M- DRD2-WT, DHT did not affect Ki67 expression in F- DRD2-WT. ES also did not affect Ki67 expression in M- DRD2 WT but decreased Ki67 expression in M-DRD2 SNPs (0.91± 0.18 vs. 1.6±0.2, n=6, p<0.05). Similar to the male data, the treatment with ES did not affect the Ki67 expression in F- DRD2 WT but decreased Ki67 expression in F- DRD2 SNPs (1.5±0.2 vs. 0.9±0.1, n=6, p<0.05). Our results demonstrate similarities (FN1 and Ki67) and differences (TGF-β and KIM-1) in profibrotic and proliferation markers expressed in hRPTCs between males and females. These differences are more pronounced in cell lines expressing DRD2 SNPs than those expressing the DRD2 WT. While both DHT and ES decreased KIM-1 expression in males with DRD2 polymorphisms, they had no effect in females with DRD2 polymorphisms. These results indicate a complex interaction of the effect of hormones and DRD2 polymorphisms in regulating the inflammatory response in hRPTCs. Their roles in regulating renal physiology and blood pressure remain to be defined. R01 DK039308 P01 HL068686 R01 HL023081 R37 HL023081 R01 DK119652/ NIH HH/ US. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Role of Dopamine D2 receptors and Oxidative Stress in the Pathogenesis of Hypertension

Globally, hypertension is the number one risk factor for death, affecting more than 1 billion people. Hypertension is the result of the interactions among genetics, epigenetics, environment, and lifestyle. The long-term regulation of blood pressure rests on renal and non-renal mechanisms. The impaired renal sodium handling in hypertension is caused by aberrant counter-regulatory natriuretic/anti-natriuretic pathways. The sympathetic nervous and renin-angiotensin systems are anti-natriuretic pathways. A counter-regulatory natriuretic pathway is the renal dopaminergic system. Aberrant dopaminergic regulation of renal sodium transport in hypertension is caused by a decrease in renal dopamine synthesis and/or dysfunction of any of the 5 dopamine receptors (D1R, D2R, D3R, D4R, & D5R). Normally, an increase in sodium intake increases while a decrease in sodium intake decreases blood pressure, albeit transiently until sodium balance is achieved. However, ~50 % of hypertensive and ~26% of normotensive subjects have increased blood pressure on high sodium intake, a case of salt sensitivity, while ~20 % have increased blood pressure on a low sodium intake, a case of inverse salt sensitivity. Low and high sodium intakes are associated with increased incidence of cardiovascular events/mortality. In humans with inverse salt sensitivity, there is a linear relationship between the number of single nucleotide polymorphisms in DRD2 (rs6276 and 6277) and decreased renal D2R expression. The increase in blood pressure on a low sodium diet may be due to increased activities of the renin-angiotensin and sympathetic nervous systems that cannot be counteracted by D2R. Hypertension may be a cause or consequence of inflammation or oxidative stress. Deficient D2R function causes renal inflammation independently of the increase in blood pressure. Subjects carrying DRD2 single nucleotide polymorphisms have increased inflammation, mediated by decreased regulation of the miR-217-Wnt5a-Ror2 pathway. The D2R, via paraoxonase2 and sestrin2, maintains normal redox balance and blood pressure. In summary, the D2R is important in the maintenance of normal blood pressure by regulating renal sodium transport, vascular reactivity, inflammation, and redox balance.

Shifting as an executive function separate from updating and inhibition in old age: Behavioral and genetic evidence

This study aimed to examine the organization of executive functions (EFs), specifically working memory updating, prepotent response inhibition, and mental-set shifting in old age, with a particular focus on determining whether the shifting function was behaviorally and genetically separated from the other functions. A total of 248 healthy older Chinese individuals participated, and multiple measures of executive functions were collected. Additionally, measures of fluid intelligence were included to explore the varying relationships between the three executive functions and this higher-order cognitive ability. Furthermore, genetic data were gathered and analyzed to investigate the associations between EFs and six candidate single-nucleotide polymorphisms (SNPs) mapped to dopaminergic, serotonergic, or glutamatergic genes. The results indicated that both the three-factor model and the two-factor model, which combined updating and inhibition, demonstrated a good fit. Furthermore, shifting was found to be behaviorally separated from the other two functions, and the correlation between shifting and fluid intelligence was smaller compared to the correlations between updating and inhibition with fluid intelligence. Moreover, the DRD2 SNPs showed significant associations with shifting, rather than with updating and inhibition. These findings provide evidence that shifting is distinct and separate from updating and inhibition, highlighting the diversity of EFs among older adults.

Functional single nucleotide polymorphisms in dopaminergic receptors D2 predict clinical response to Cariprazine.

Cariprazine (CAR) is an antipsychotic drug for the treatment of schizophrenia (SCZ) and bipolar disorder (BD), and it acts as a partial agonist on the dopamine receptors (DR), D2, and D3. Although many single nucleotide polymorphisms (SNPs) in genes coding for these receptors are known to influence response to antipsychotics, to date, no study on CAR pharmacogenetics exists. In this pilot study, we investigated the relationship between SNPs in DRD2 (rs1800497 and rs6277) and DRD3 (rs6280), and response to CAR treatment, evaluated by the psychometric Brief Psychiatric Rating Scale (BPRS), in a cohort of Caucasian patients. We found a significant association between DRD2 rs1800497 and rs6277 and response to CAR treatment. When genotypes were combined into an arbitrary score, the receiver operating characteristic curve analysis showed that using a cut-off value of -2.5 the response to CAR treatment could be predicted with a positive likelihood ratio of 8.0. Our study report, for the first time, a correlation between SNPs in DRD2 and response to CAR treatment. After confirmation in a larger cohort of patients, our results could open the way for the identification of new tools for the provision of response to CAR treatment.

CHRNA5-A3-B4 and DRD2 Genes and Smoking Cessation Throughout Adulthood: A Longitudinal Study of Women.

Smoking cessation is more than 50% heritable. Genetic studies of smoking cessation have been limited by short-term follow-up or cross-sectional design. This study tests single nucleotide polymorphism (SNP) associations with cessation during long-term follow-up throughout adulthood in women. The secondary aim tests whether genetic associations differ by smoking intensity. Associations between 10 SNPs in CHRNA5, CHRNA3, CHRNB2, CHRNB4, DRD2, and COMT and the probability of smoking cessation over time were evaluated in two longitudinal cohort studies of female nurses, the Nurses' Health Study (NHS) (n = 10 017) and NHS-2 (n = 2793). Participant follow-up ranged from 2 to 38 years with data collected every 2 years. Women with the minor allele of either CHRNA5 SNP rs16969968 or CHRNA3 SNP rs1051730 had lower odds of cessation throughout adulthood [OR = 0.93, p-value = .003]. Women had increased odds of cessation if they had the minor allele of CHRNA3 SNP rs578776 [OR = 1.17, p-value = .002]. The minor allele of DRD2 SNP rs1800497 was associated with lower odds of cessation in moderate-to-heavy smokers [OR = 0.92, p-value = .0183] but increased odds in light smokers [OR = 1.24, p-value = .096]. Some SNP associations with short-term smoking abstinence observed in prior studies were shown in the present study to persist throughout adulthood over decades of follow-up. Other SNP associations with short-term abstinence did not persist long-term. The secondary aim findings suggest genetic associations may differ by smoking intensity. The results of the present study expand on previous studies of SNP associations in relation to short-term smoking cessation to demonstrate some of these SNPs were associated with smoking cessation throughout decades of follow-up, whereas other SNP associations with short-term abstinence did not persist long-term. The rate of relapse to smoking remains high for several years after quitting smoking, and many smokers experience multiple quit attempts and relapse episodes throughout adulthood. Understanding genetic associations with long-term cessation has potential importance for precision medicine approaches to long-term cessation management.

173 The role of an intronic single nucleotide polymorphism within the dopamine receptor type-2 gene on pituitary prolactin protein expression in bulls

Abstract Detrimental effects to male reproductive physiology have been observed due to changes in prolactin (PRL) serum concentration. Regulation of PRL by dopamine binding to the dopamine type-2 receptor (DRD2) is well defined and associations between male physiology and single nucleotide polymorphisms (SNPs) within the DRD2 gene have been observed. The objective of the study was to evaluate association of a DRD2 SNP to PRL protein expression in bulls. Testis and epididymis were collected from bulls grazing a forage containing or lacking a dopamine agonist at the end of a 126 d study (n = 14). Bovine pituitaries (n = 587) were collected randomly over 3 mo from a local abattoir which processes cull cows and bulls. Sex of pituitaries was verified (n = 259 males) by duplex PCR for amplification of SRY and b-actin followed by Southern blotting of PCR products for selection of male. Prolactin protein expression was assessed in testis, epididymis, and pituitary by western blotting. Expression of PRL protein was below detection range in reproductive tissues but was present in pituitary, therefore experiments continued in pituitary. Restriction fragment length polymorphism genotyping was performed on pituitaries by amplification of the DRD2 SNP region followed by digestion with a Tfil enzyme. Digested of products produced 3,2, or 1 band (AG, AA, GG, respectively). A subset of male pituitaries was blotted by slot blot manifold and PRL protein expression assessed by immunodetection and densitometry analysis normalized to GAPDH expression. Pituitary genotype distribution was 17.4% AA (n = 16), 63% AG (n = 58), and 19.6% GG (n = 18). Prolactin protein expression in the pituitary was similar across genotype (P = 0.23). These findings indicate that the DRD2 SNP has no genotypic effect on PRL protein expression in bovine pituitary.

Assessment of the Association of D2 Dopamine Receptor Gene and Reported Allele Frequencies With Alcohol Use Disorders

The association between the D2 dopamine receptor gene (DRD2) Taq1A locus (rs1800497) and alcohol use disorder (AUD) is enduring but the subject of long-standing controversy; meta-analysis of studies across 3 decades shows an association between rs1800497 and AUD, but genome-wide analyses have detected no role for rs1800497 in any phenotype. No evidence has emerged that rs1800497, which is located in ANKK1, perturbs the expression or function of DRD2. To resolve contradictions in previous studies by identifying hidden confounders and assaying for functional effects of rs1800497 and other loci in the DRD2 region. PubMed (882 studies), Embase (1056 studies), and Web of Science (501 studies) databases were searched through August 2018. Three clinical populations-Finnish, Native American, and African American participants-were genotyped for 208 to 277 informative single-nucleotide polymorphisms (SNPs) across the DRD2 region to test the associations of SNPs in this region with AUD. Eligible studies had diagnosis of AUD made by accepted criteria, reliable genotyping methods, sufficient genotype data to calculate odds ratios and 95% CIs, and availability of control allele frequencies or genotype frequencies. After meta-analysis of 62 studies, metaregression was performed to detect between-study heterogeneity and to explore the effects of moderators, including deviations of cases and controls from allele frequencies in large population databases (ExAC and 1000 Genomes). Linkage to AUD and the effect on gene expression of rs1800497 were evaluated in the context of other SNPs in the DRD2 region. Data analysis was performed from August 2018 to March 2019. This study follows the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline. The effects of rs1800497 and other SNPs in the DRD2 region on gene expression were measured in human postmortem brain samples via differential allelic expression and evaluated in other tissues via publicly available expression quantitative locus data. A total of 62 studies of DRD2 and AUD with 16 294 participants were meta-analyzed. The rs1800497 SNP was associated with AUD (odds ratio, 1.23; 95% CI, 1.14-1.31; P < .001). However, the association was attributable to spuriously low allele frequencies in controls in positive studies, which also accounted for some between-study heterogeneity (I2 = 43%; 95% CI, 23%-58%; Q61 = 107.20). Differential allelic expression of human postmortem brain and analysis of expression quantitative loci in public data revealed that a cis-acting locus or loci perturb the DRD2 transcript level; however, rs1800497 does not and is not in strong disequilibrium with such a locus. Across the DRD2 region, other SNPs are more strongly associated with AUD than rs1800497, although no DRD2 SNP was significantly associated in these 3 clinical samples. In this meta-analysis, the significant association of DRD2 with AUD was reassessed. The DRD2 association was attributable to anomalously low control allele frequencies, not function, in positive studies. For genetic studies, statistical replication is not verification.

59 Genotypic effects of a Dopamine receptor type-2 SNP on growth and semen quality in beef bulls exposed to a dopamine agonist

Abstract Ergot alkaloids (EA) share similar structural properties to neurotransmitters and are able to elicit physiological responses in cattle that consume them by binding receptors such as the Dopamine type-2 receptor (DRD2). A single nucleotide polymorphism (SNP) in DRD2, previously found to be correlated to prolactin (PRL) serum concentrations was evaluated for impact on growth traits and semen quality parameters. Yearling beef bulls were allowed to graze a diet containing (E+) (n = 41) or lacking EA (E-) (n = 43) over a four-year study. Blood samples and semen were collected every 21 or 28 d. Semen motility, morphology, body condition score (BCS), and scrotal circumference (SC) were recorded. Prolactin (PRL) serum concentrations were assessed by radioimmunoassay (RIA). Bulls were sacrificed from the first year at the end of a 126-day period or 60 days after removal of treatment. Testicles and epididymis were collected and immunohistochemistry was performed on testis, epididymis, and sperm cells. Tissues and cells were incubated in the presence or absence of primary antibody against DRD2 with a DAPI counterstain. Isolation of DNA was performed on sperm pellets from semen collected using DNAzol (Thermo Fisher Scientific, Waltham, MA, USA). Amplification of the DRD2 SNP region was performed by PCR and resulting products were assessed for genotype through restriction fragment length polymorphism (RFLP) analysis. These data show the presence of DRD2 in the testis, epididymis, and sperm cells; however, semen quality and growth traits did not differ across DRD2 genotype or treatment. Body condition (P = 0.0009), SC (P = 0.0053), and semen velocity (P = 0.0398) differed across period. As expected, consumption of EA resulted in decreased prolactin serum concentrations (P = 0.0240).

30 Genotypic effects of a Dopamine receptor type-2 SNP on growth and semen quality in beef bulls exposed to a dopamine agonist

Abstract Ergot alkaloids (EA) share similar structural properties to neurotransmitters and are able to elicit physiological responses in cattle that consume them by binding receptors such as the Dopamine type-2 receptor (DRD2). A single nucleotide polymorphism (SNP) in DRD2, previously found to be correlated to prolactin (PRL) serum concentrations was evaluated for impact on growth traits and semen quality parameters. Yearling beef bulls were allowed to graze a diet containing (E+) (n = 41) or lacking EA (E-) (n = 43) over a four-year study. Blood samples and semen were collected every 21 or 28 d. Semen motility, morphology, body condition score (BCS) and scrotal circumference (SC) were recorded. Prolactin (PRL) serum concentrations were assessed by radioimmunoassay (RIA). Bulls were sacrificed from the first year at the end of a 126-day period or 60 days after removal of treatment. Testicles and epididymis were collected and immunohistochemistry was performed on testis, epididymis, and sperm cells. Tissues and cells were incubated in the presence or absence of primary antibody against DRD2 with a DAPI counterstain. Isolation of DNA was performed on sperm pellets from semen collected using DNAzol (Thermo Fisher Scientific, Waltham, MA, USA). Amplification of the DRD2 SNP region was performed by PCR and resulting products were assessed for genotype through restriction fragment length polymorphism (RFLP) analysis. These data show the presence of DRD2 in the testis, epididymis, and sperm cells; however, semen quality and growth traits did not differ across DRD2 genotype or treatment. Body condition (P = 0.0009), SC (P = 0.0053), and semen velocity (P = 0.0398) differed across period. As expected, consumption of EA resulted in decreased prolactin serum concentrations (P = 0.0240)

Case-control study analysis of DRD2 gene polymorphisms in drug addicted patients.

The aim of the study was to determine relationships between the selected DRD2 gene polymorphisms and drug addiction. One hundred drug abusers undergoing treatment were recruited from the inpatient psychiatric centers in Poland. All participants were screened by means of the clinical interview SSAGA to describe the clinical picture. In the second part of the study, participants were examined using psychometric tools assessing selected psychopathological features. After that, blood samples were collected for a DNA isolation. The following DRD2 single nucleotide polymorphisms (SNPs) of the dopamine gene were genotyped: rs1800498 polymorphism of DRD2 gene (NC_000011.10:g.113420866G>A, GRCh38.p7); rs1079597 polymorphism of DRD2 gene (NC_000011.10:g.113425564C>T, GRCh38.p7); rs1076560 polymorphism of DRD2 gene (NC_000011.10:g.113412966C>A, GRCh38.p7). The rs1800498 polymorphism has shown an association with drug abuse in which a higher frequency of the allelic T form was observed in the whole group of patients and selected subgroups with concomitant opiates or cannabis abuse history when compared with the controls. In the presented study, one of selected polymorphisms of DRD2 gene, revealed to be correlated with substance use disorder (at the limit of statistical significance), which could suggest its impact on dependence endophenotype. The presented research was a pilot study, so it requires replication on a larger group of patients to verify and confirm obtained outcomes.

Association between DRD2 gene polymorphisms and the dosage used on methadone maintenance treatment program

Objective: To investigate the association between three single nucleotide polymorphism (SNP) genes DRD2 (rs1800497, rs6275, and rs1799978) and the dosage used on methadone maintenance treatment (MMT). Methods: From the methadone maintenance treatment centers, 257 MMT patients were recruited to participate in a case-control study and divided into two groups-control groups under low dosage (n=89) and case (n=168) group with high dosage. Quanto software was used to estimate the sample size as 180. Information related to social-demographic status, history on drug use and medication were collected. And DRD2 SNPs were genotyped to explore the relationship between polymorphism of DRD2 gene and the dosage of methadone maintenance treatment. Results: Distributions of DRD2 rs6275 between different groups were significantly different. Patients carrying TC genotype needed lower dose of methadone when compared to the patients that carrying CC genotype counterparts (OR=0.338, 95% CI: 0.115-0.986). Patients that carrying C allele at rs6275 needed lower methadone dose than those that carrying genotype TT (OR=0.352, 95% CI: 0.127-0.975). Distributions of genotypes, alles in the other two SNPs (rs1800497, rs1799978) were not significantly different between groups under different dosages. Conclusion: DRD2 rs6275 was associated with dosage of methadone used for the MMT patients. However, no significant associations were found between rs1800497, rs1799978 and the dosage of methadone.

The impact of common dopamine D2 receptor gene polymorphisms on D2/3 receptor availability: C957T as a key determinant in putamen and ventral striatum

Dopamine function is broadly implicated in multiple neuropsychiatric conditions believed to have a genetic basis. Although a few positron emission tomography (PET) studies have investigated the impact of single-nucleotide polymorphisms (SNPs) in the dopamine D2 receptor gene (DRD2) on D2/3 receptor availability (binding potential, BPND), these studies have often been limited by small sample size. Furthermore, the most commonly studied SNP in D2/3 BPND (Taq1A) is not located in the DRD2 gene itself, suggesting that its linkage with other DRD2 SNPs may explain previous PET findings. Here, in the largest PET genetic study to date (n=84), we tested for effects of the C957T and -141C Ins/Del SNPs (located within DRD2) as well as Taq1A on BPND of the high-affinity D2 receptor tracer 18F-Fallypride. In a whole-brain voxelwise analysis, we found a positive linear effect of C957T T allele status on striatal BPND bilaterally. The multilocus genetic scores containing C957T and one or both of the other SNPs produced qualitatively similar striatal results to C957T alone. The number of C957T T alleles predicted BPND in anatomically defined putamen and ventral striatum (but not caudate) regions of interest, suggesting some regional specificity of effects in the striatum. By contrast, no significant effects arose in cortical regions. Taken together, our data support the critical role of C957T in striatal D2/3 receptor availability. This work has implications for a number of psychiatric conditions in which dopamine signaling and variation in C957T status have been implicated, including schizophrenia and substance use disorders.

M55 - Pharmacogenetic Study of Antipsychotic Response To Treatment In Mexican Patients with Schizophrenia: Analysis of Response And Resistance

Background The efficacy of antipsychotics treatment in schizophrenia patients has long been established; however, clinical response to these drugs is not the same in all patients. Genetic variability has been proposed as the main reason for the different outcomes.The dopaminergic pathways, the principal mechanism of action of the antipsychotics, have been the main focus of pharmacogenetic studies in schizophrenia. Some functional single nucleotide polymorphisms (SNPs) have been associated with dopamine disposition or dopamine receptor expression, modifying the response to treatment. The aim of the study was to analyze the association between two response phenotypes (patients with response and resistant) and COMT (Val58Met), DRD2 (A-241G, C/G exon 8, C939T, Taq1A) and DRD3 (Ser9Gly) gene polymorphisms. Methods Treatment response was retrospectively/prospectively assessed. First, we gathered all reliable antipsychotics assays from medical files and through interviews with attending physicians. If these data were not conclusive, a mandatory follow-up period was added with regularly scheduled ratings (using the Positive and Negative Symptom Scale PANSS and the Functional Assessment Scale for Comprehensive Treatment of Schizophrenia FACT-Sz).Treatment response was defined on a ≥ 30% decrease on the total PANSS score (with an antipsychotic different from clozapine). The sample was classified in two main phenotypes: 95 patients on response to treatment group and 81 on resistant-to-treatment group. The genotyping of the COMT (Val58Met), DRD2 (A-241G, C/G exon 8, C939T, Taq1A), and DRD3 (Ser9Gly) gene polymorphisms was performed with allelic discrimination, using TaqMan assays. Differences in genotypes and allele frequencies between the phenotypes of patients were calculated using the X2 test. Also, we performed a logistic regression analysis to predict the likelihood of the resistance-to-treatment phenotype. Results Analysis of Val158Met/COMT showed differences between the response and the resistance groups. The GG genotype (Val/Val) was more frequent in the response group than the resistance group (47% vs. 33%, X2=6.26, 2 df , p=0.04) . We also found allele differences between groups (X2=6.65, 1 df, p Discussion The COMT/Val158Met SNP (Val/Val) was associated with the response to treatment phenotype. This finding is consistent with the antipsychotics proposed mechanism of action. The antipsychotic efficay on lowering the hyperdopaminergic state would be greater in those patients with the high-activity COMT genotype. The DRD2 SNPs analysis, the main target of several studies, did not show any significant association with the phenotypes. The COMT and DRD3 gene analyses could be associated with the resistant-to-treatment patients, so they elicit the possibility as plausible mediators of the resistance to treatment for schizophrenia.One of the limitations of this study is the size of the sample. Further analyses should be performed for the validation of these SNPs as mediators for the response or resistance to antipsychotics.

The Association of DRD2 with Insight Problem Solving.

Although the insight phenomenon has attracted great attention from psychologists, it is still largely unknown whether its variation in well-functioning human adults has a genetic basis. Several lines of evidence suggest that genes involved in dopamine (DA) transmission might be potential candidates. The present study explored for the first time the association of dopamine D2 receptor gene (DRD2) with insight problem solving. Fifteen single-nucleotide polymorphisms (SNPs) covering DRD2 were genotyped in 425 unrelated healthy Chinese undergraduates, and were further tested for association with insight problem solving. Both single SNP and haplotype analysis revealed several associations of DRD2 SNPs and haplotypes with insight problem solving. In conclusion, the present study provides the first evidence for the involvement of DRD2 in insight problem solving, future studies are necessary to validate these findings.

Genetic Polymorphisms in the Dopamine Receptor 2 Predict Acute Pain Severity After Motor Vehicle Collision.

Dopaminergic signaling is implicated in nociceptive pathways. These effects are mediated largely through dopamine receptors and modulated in part by dopamine transporters. This study tested the hypothesis that genetic variants in the genes encoding dopamine receptor 2 (DRD2) and the dopamine active transporter (SLC6A3) influence acute pain severity after motor vehicle collision. European Americans presenting to the emergency department after motor vehicle collision were recruited. Overall pain intensity in emergency department was assessed using a 0 to 10 numeric rating scale. DNA was extracted from blood samples and genotyping of single-nucleotide polymorphisms (SNPs) in the DRD2 and SLC6A3 gene was performed. A total of 948 patients completed evaluation. After correction for multiple comparisons, SNP rs6276 at DRD2 showed significant association with pain scores, with individuals with the A/A genotype reporting lower mean pain scores (5.3; 95% confidence interval [CI], 5.1-5.5) than those with A/G (5.9; 95% CI, 5.6-6.1) or G/G (5.7; 95% CI, 5.2-6.2) genotypes (P=0.0027). Secondary analyses revealed an interaction between sex and DRD2 SNPs rs4586205 and rs4648318 on pain scores: females with 2 minor alleles had increased pain intensity, whereas males with 2 minor alleles had less pain than individuals with a major allele (interaction P=0.0019). Genetic variants in DRD2 are associated with acute pain after a traumatic stressful event. These results suggest that dopaminergic agents may be useful for the treatment of individuals with acute posttraumatic pain as part of a multimodal opioid-sparing analgesic regimen.

Subclinical psychotic experiences in healthy young adults: associations with stress and genetic predisposition.

Stress has been identified as a common trigger for psychosis. Dopamine pathways are suggested to be affected by chronic and severe stress and to play an important role in psychosis. This pilot study investigates the potential relationship of stress and psychosis in subclinical psychotic experiences. It was hypothesized that single-nucleotide polymorphisms (SNPs) previously found to be associated with psychiatric disorders would be associated with both stress and subclinical psychotic experiences. University students (N=182) were genotyped for 17 SNPs across 11 genes. Higher stress reporting was associated with rs4680 COMT, rs13211507 HLA region, and rs13107325 SLC39A8. Reports of higher subclinical psychotic experiences were associated with DRD2 SNPs rs17601612 and rs658986 and an AKT1 SNP rs2494732. Replication studies are recommended to further pursue this line of research for identification of markers of psychosis for early diagnosis and intervention.

Abstract 49: The association of genetic variants in dopamine regulators with indoor tanning and melanoma.

Abstract Ultraviolet radiation (UVR) is the main etiologic factor associated with the development of melanoma and there is now strong evidence to support an increased risk of melanoma incidence with exposure to UVR emitting indoor tanning devices. Most frequent tanners have an appropriate knowledge of the health risks associated with indoor tanning but continue to tan despite these risks. A relatively large percentage of frequent indoor tanners display addictive behavior implicating the involvement of complex factors in the persistent desire to tan indoors. Genetic factors are thought to play a role in biological reward pathways that reinforce addictive behavior such as with alcohol or nicotine dependency. In addition, UVR is hypothesized to modify biological pathways, for example through the dopamine neurotransmitter system, to reinforce tanning behavior. No studies to date have examined variants in genes involved with dopamine regulation and drug metabolism with indoor tanning behavior and risk for melanoma. We examined the association of 68 single nucleotide polymorphisms (SNPs) in 5 dopamine receptor and drug metabolism genes in DNA from participants of the Skin Health Study, a study in Minnesota developed to assess the risk of melanoma with indoor tanning behavior. The Skin Health Study recruited individuals with cutaneous melanoma (cases) and without melanoma (controls) between the ages of 25-59 in Minnesota from 2004 to 2007. Detailed information on lifetime indoor tanning behavior was collected by interview that was partially self-administered and partially telephone-administered. DNA samples were obtained from mouthwash, and DNA was genotyped using the Illumina GoldenGate platform. The association of SNPs with melanoma was assessed by logistic regression in cases (n=894) and controls (n=799). Due to possible confounding of tanning behavior and melanoma, the association of SNPs with having ever or never tanned indoors was assessed in controls only. Participants with variants in the DRD2 dopamine receptor gene and the ANKK1 signaling gene were more likely to have ever tanned indoors compared to those without DRD2 and ANKK1 variants. Variants in DRD2 and ANKK1 were also associated with increased risks for melanoma (rs1003641 OR=1.18, CI: 1.01, 1.38; rs2734831 OR=1.17, CI 1.01, 1.35). The interactions of one ANKK1 SNP and 3 DRD2 SNPs with tanning behavior were significantly associated with risk for melanoma (p &amp;lt; 0.05 for all). These data suggest that variants in dopamine receptors could mediate tanning behavior that ultimately influences risk for melanoma. The DRD2 and ANKK1 alleles represent important genomic regions for further investigations to explore addictive tanning behavior. Citation Format: Kristina G. Flores, Esther Erdei, Li Luo, Kirsten A.M. White, Marianne Berwick, DeAnn Lazovich. The association of genetic variants in dopamine regulators with indoor tanning and melanoma. [abstract]. In: Proceedings of the AACR Special Conference on Post-GWAS Horizons in Molecular Epidemiology: Digging Deeper into the Environment; 2012 Nov 11-14; Hollywood, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(11 Suppl):Abstract nr 49.

Early postnatal experience and DRD2 genotype affect dopamine receptor expression in the rat ventral striatum

Dopamine systems can be altered by experiences such as early life adversity. The intensity of these effects seems to vary as a function of interactions between genetic and environmental influences. In a series of experiments we have investigated the effects of genetic variants and early life adversity on several biobehavioral outcomes. Here we investigated the presence of single nucleotide polymorphisms (SNPs) in the gene coding for dopamine D2 receptors (DRD2) and the interaction between these variants with early life adversity on the expression of D2 receptors in the striatum. Time-mated pregnant female rats underwent restraint stress (gestational days 10–21) or were left undisturbed. Following parturition rat pups were maternally reared (MR) or artificially reared (AR). Subsequent to adult behavioral testing, rats were genotyped and their brains were processed (autoradiography) for D2 receptor expression. We found three variants in the DRD2 gene and these variants interacted with early adversity to affect D2 receptor expression in the nucleus accumbens. Specifically, artificially reared rats with AG DRD2 variant showed significantly higher D2 expression compared to mother reared rats with the AG DRD2 variant as well as the artificially reared rats with a GG DRD2 variant. These findings show that adult D2 expression is significantly influenced by the interaction of DRD2 SNPs and early developmental factors. These finding may explain why there are significant individual differences in the impact of early life adversity on dopamine-dependent processes and disorder vulnerabilities.

No Evidence for an Association between Dopamine D2 Receptor Polymorphisms and Tardive Dyskinesia in Korean Schizophrenia Patients

ObjectiveTardive dyskinesia (TD) is a long-term adverse effect of antipsychotic. Dopaminergic activity in the nigrostriatal system have been proposed to be involved in development of TD and dopamine D2 receptors (DRD2) has been regarded as a candidate gene for TD because the antipsychotics have potent antagonism DRD2. This study was aimed to find the relationship between DRD2 gene and antipsychotic-induced TD.MethodsWe evaluated whether 5 DRD2 single nucleotide polymorphisms (-141Cins>del/TaqID/NcoI/Ser311Cys/TaqIA) are associated with antipsychotic-induced TD in 263 Korean schizophrenia patients with (n=100) and without TD (n=163) who were matched for antipsychotic drug exposure and other relevant variables. Haplotype analyses were also performed.ResultsNone of 5 polymorphisms were found to be significantly associated with TD and with TD severity as measured by Abnormal Involuntary Movement Scale. Overall haplotype (-141Cins>del/TaqID/NcoI/Ser311Cys/TaqIA) frequency was also not significantly different between TD and non-TD groups, although one rare haplotype (I-D1-T-G-A1) showed significantly different frequency between TD and non-TD groups (2.7% vs. 8.5%, respectively, p=0.031).ConclusionThe present study does not support that DRD2 gene may be involved in TD in the Korean population, although further studies are warranted.