Epigenetic Analysis of the Dopamine Transporter Gene DAT1 with a Focus on Personality Traits in Athletes.

Human phenotypes (traits) are determined by the selective use of a person's unique genotype (DNA sequence), following exposure to environmental stimuli, such as exercise. Inducing profound changes in epigenetics may be an underlying factor of the beneficial effects of exercise. This study aimed to investigate the association between methylation in the promoter region of the DAT1 gene and personality traits measured by the NEO-FFI questionnaire in a group of athletes. The study group included 163 athletes, and the control group consisted of 232 non-athletes. The obtained results show several significant differences between the studied groups of subjects. The Extraversion scale and the Conscientiousness scale results of the NEO-FFI are significantly higher in the group of athletes compared to controls. The total methylation and the number of methylated islands in the promoter region of the DAT1 gene are higher in the study group. Pearson's linear correlation between the total methylation, the number of methylated islands and the NEO-FFI shows significant results for the Extraversion and Agreeability scales. The total methylation and the number of methylated islands in the promoter region of the DAT1 gene are higher in the study group. Pearson's linear correlation between the total methylation, the number of methylated islands and the NEO-FFI shows significant results for the Extraversion and Agreeability scales. Our analysis of the methylation status of individual CpG sites revealed a new direction of research into the biological aspects of regulating dopamine release and personality traits in people practicing sports.

DNA Methylation of the Dopamine Transporter DAT1 Gene-Bliss Seekers in the Light of Epigenetics.

DNA methylation (leading to gene silencing) is one of the best-studied epigenetic mechanisms. It is also essential in regulating the dynamics of dopamine release in the synaptic cleft. This regulation relates to the expression of the dopamine transporter gene (DAT1). We examined 137 people addicted to nicotine, 274 addicted subjects, 105 sports subjects and 290 people from the control group. After applying the Bonferroni correction, our results show that as many as 24 out of 33 examined CpG islands had statistically significantly higher methylation in the nicotine-dependent subjects and athletes groups compared to the control group. Analysis of total DAT1 methylation revealed a statistically significant increase in the number of total methylated CpG islands in addicted subjects (40.94%), nicotine-dependent subjects (62.84%) and sports subjects (65.71%) compared to controls (42.36%). The analysis of the methylation status of individual CpG sites revealed a new direction of research on the biological aspects of regulating dopamine release in people addicted to nicotine, people practicing sports and people addicted to psychoactive substances.

Analysis of the Methylation Level of the DAT1 Dopamine Transporter Gene in Patients Addicted to Stimulants, Taking into Account an Analysis of Personality Traits.

Drug addiction is a chronic biochemical drug use disorder that affects the human brain and behavior and leads to the uncontrolled use of legal or illicit drugs. It has been shown that three factors are involved in the development of addiction: genetic factors, a diverse environment, and the effect of medication on gene expression. The comprehensive approach and holistic analysis of the problem are due to the multigenic and multifactorial nature of addiction. Dopamine, one of the major neurotransmitters in the brain, is believed to be the "culprit" that leads to a drug abuse-induced "high". That is why, in our research, we focused mainly on the genes related to dopaminergic reuptake. In the present study, we chose methylation of the DAT1 dopamine transporter gene based on molecular reasons related to the dopaminergic theory of addiction. This study included two groups: 226 stimulant-dependent and 290 non-stimulant-dependent subjects. The analysis consisted of a case-control comparison of people addicted to psychostimulants compared to a control group of healthy and non-addicted people. There were differences in the levels of statistical significance between the groups. Our research shows lower methylation of islands 1, 9, and 14 in addicted people and greater methylation of islands 32 and 33. The difference in individual CpG methylation islands of the gene under study provides valuable information about the DNA methylation process in patients addicted to psychostimulants. Pearson's linear correlation analysis in stimulant dependence showed a negative correlation between total methylation island levels and the NEO-FFI Neuroticism scale. In subjects with neuroticism, the methylation level was statistically significantly lower. Pearson's linear correlation analysis of stimulant-dependent subjects showed a positive correlation between total methylation island levels and the NEO-FFI Openness scale and the NEO-FFI Conscientiousness scale.

The dopamine membrane transporter plays an active modulatory role in synaptic dopamine homeostasis.

Modulatory mechanisms of neurotransmitter release and clearance are highly controlled processes whose finely tuned regulation is critical for functioning of the nervous system. Dysregulation of the monoamine neurotransmitter dopamine can lead to several neuropathies. Synaptic modulation of dopamine is known to involve pre-synaptic D2 auto-receptors and acid sensing ion channels. In addition, the dopamine membrane transporter (DAT), which is responsible for clearance of dopamine from the synaptic cleft, is suspected to play an active role in modulating release of dopamine. Using functional imaging on the Caenorhabditis elegans model system, we show that DAT-1 acts as a negative feedback modulator to neurotransmitter vesicle fusion. Results from our fluorescence recovery after photo-bleaching (FRAP) based experiments were followed up with and reaffirmed using swimming-induced paralysis behavioral assays. Utilizing our numerical FRAP data we have developed a mechanistic model to dissect the dynamics of synaptic vesicle fusion, and compare the feedback effects of DAT-1 with the dopamine auto-receptor. Our experimental results and the mechanistic model are of potential broader significance, as similar dynamics are likely to be used by other synaptic modulators including membrane transporters for other neurotransmitters across species.

Association between dopamine transporter gene (DAT1/SLC6A3) variants and infertility in the Turkish females.

OBJECTIVE: Worldwide, approximately 10-15% of couples is affected by infertility and infertility is associated with disturbances in female and/or male reproductive systems. The aim of the current study is to investigate the relationship between DAT1 (SLC6A3) VNTR polymorphism with female infertility. METHODS: Genomic DNA extractions were performed in 98 fertile and 90 infertile females, 3' untranslated region (3' UTR) variable number tandem repeat (VNTR) polymorphism of DAT1/SLC6A3 was determined by the use of Polymerase Chain Reaction (PCR) method. RESULTS: It has been demonstrated that there was no statistically significant difference between female infertile and fertile groups in the terms of DAT1 genotypes (p > .05). Moreover, there was no significant difference regarding the frequencies of 9R and 10R alleles in infertile and fertile groups (p > .05). CONCLUSION: This is the first study for investigating the relationship between DAT1/SLC6A3 gene polymorphism and infertility in females. Our study contributes to the growing awareness of the relationship between dopaminergic system and female infertility despite no significant differences were reported between infertile females and corresponding fertile subjects in DAT1/SLC6A3 gene.

Driving risks of young drivers with symptoms of attention deficit hyperactivity disorder: association with the dopamine transporter gene VNTR polymorphism.

BACKGROUND: Road traffic injuries are a leading cause of death for young adults, and young drivers with higher expression of symptoms of attention deficit-hyperactivity disorder (ADHD) could pose an even greater risk in traffic. Dopaminergic dysfunction has been found to occur in ADHD, with the dopamine transporter (DAT) gene VNTR polymorphism (DAT1 VNTR; rs28363170) being one of the most consistent genetic markers. Thus, we aimed at clarifying how the ADHD symptoms and the DAT1 VNTR relate to risk-taking behaviour in traffic, impulsivity and driving anger in young drivers. METHOD: We used data of two traffic behaviour study samples (n = 741, mean age = 23.3 ± 7.2 years; n = 995, mean age = 22.9 ± 8.1 years) and the Estonian Children Personality Behaviour and Health Study (ECPBHS; traffic behaviour data n = 1,016, mean age = 25.2 ± 2.1 years). ADHD symptoms were assessed by self-report with the Adult ADHD Self-Report Scale (ASRS v1.1) and impulsivity with the Adaptive and Maladaptive Impulsivity Scale. Traffic behavioural measures were either self-reported (Driver Behaviour Questionnaire, Driving Anger Scale) or obtained from databases (registered accidents and violations). RESULTS: Drivers with more self-reported ADHD symptoms also reported more risk-taking in traffic and had more of recorded traffic accidents and violations. DAT1 9 R carriers had a higher probability of high traffic risk behaviour only if they also had ADHD symptoms. CONCLUSION: Higher level of ADHD symptoms is a significant risk factor in traffic, and carrying of the DAT1 9 R allele appears to aggravate these risks.

Disordered eating in early childhood: DRD4 and DAT1 gene polymorphisms and quality of mother-child interaction.

PURPOSE: Eating disturbances are complex heritable conditions that can be influenced by both genetic and environmental factors but are poorly studied in early development. The aim of this research was to investigate the association of genetic polymorphisms within dopaminergic pathways with early feeding problems. METHODS: We analyzed the presence of VNTR polymorphisms of DRD4 (rs1805186) and DAT1 (rs28363170) in overeating (N = 45), undereating (N = 48) and control (N = 44) young children. We also assessed presence of externalizing, internalizing and dysregulation symptoms by the Child Behavior Checklist and quality of mother-child interactions during feeding by the Italian adaptation of the Scale for the Assessment of Feeding Interaction, respectively. RESULTS: Both polymorphisms were associated with children's eating behavior, psychological symptoms and quality of interaction with their mothers, suggesting that: (a) the DRD4 4-repeat allele behaves as a protective factor, the 2-repeats and 7-repeats alleles as risk factors, for undereating behavior, the general quality of mother-child interaction and internalizing, externalizing and dysregulated symptoms; and (b) the DAT1 9-repeats allele behaves as a protective factor, the 10-repeats allele as a risk factor, for overeating behavior, the general quality of mother-child interaction, internalizing, externalizing and dysregulated symptoms. Finally, a gene x gene interaction is suggested between the DAT1 9-repeat or 10-repeat allele and the DRD4 4-repeat allele. CONCLUSIONS: Our results suggest a role for DRD4 and DAT1 in an early susceptibility to eating disturbances. LEVEL OF EVIDENCE III: Evidence obtained from well-designed case-control analytic study.

Dopamine-dependent biphasic behaviour under 'deep diving' conditions in Caenorhabditis elegans.

Underwater divers are susceptible to neurological risks due to their exposure to increased pressure. Absorption of elevated partial pressure of inert gases such as helium and nitrogen may lead to nitrogen narcosis. Although the symptoms of nitrogen narcosis are known, the molecular mechanisms underlying these symptoms have not been elucidated. Here, we examined the behaviour of the soil nematode Caenorhabditis elegans under scuba diving conditions. We analysed wild-type animals and mutants in the dopamine pathway under hyperbaric conditions, using several gas compositions and under varying pressure levels. We found that the animals changed their speed on a flat bacterial surface in response to pressure in a biphasic mode that depended on dopamine. Dopamine-deficient cat-2 mutant animals did not exhibit a biphasic response in high pressure, while the extracellular accumulation of dopamine in dat-1 mutant animals mildly influenced this response. Our data demonstrate that in C. elegans, similarly to mammalian systems, dopamine signalling is involved in the response to high pressure. This study establishes C. elegans as a powerful system to elucidate the molecular mechanisms that underly nitrogen toxicity in response to high pressure.

A causal role of estradiol in human reinforcement learning.

The sex hormone estradiol is hypothesized to play a key role in human cognition, and reward processing specifically, via increased dopamine D1-receptor signalling. However, the effect of estradiol on reward processing in men has never been established. To fill this gap, we performed a double-blind placebo-controlled study in which men (N = 100) received either a single dose of estradiol (2 mg) or a placebo. Subjects performed a probabilistic reinforcement learning task where they had to choose between two options with varying reward probabilities to maximize monetary reward. Results showed that estradiol administration increased reward sensitivity compared to placebo. This effect was observed in subjects' choices, how much weight they assigned to their previous choices, and subjective reports about the reward probabilities. Furthermore, effects of estradiol were moderated by reward sensitivity, as measured through the BIS/BAS questionnaire. Using reinforcement learning models, we found that behavioral effects of estradiol were reflected in increased learning rates. These results demonstrate a causal role of estradiol within the framework of reinforcement learning, by enhancing reward sensitivity and learning. Furthermore, they provide preliminary evidence for dopamine-related genetic variants moderating the effect of estradiol on reward processing.

Opioid and Dopamine Genes Interact to Predict Naltrexone Response in a Randomized Alcohol Use Disorder Clinical Trial.

BACKGROUND: While the opiate antagonist, naltrexone, is approved for treating alcohol use disorder (AUD), not everyone who receives the medication benefits from it. This study evaluated whether the OPRM1 SNP rs1799971 interacts with the dopamine transporter gene DAT1/SLC6A3 VNTR rs28363170 or the catechol-O-methyltransferase (COMT) gene SNP rs4680 in predicting naltrexone response. METHODS: Individuals who met DSM-IV alcohol dependence were randomly assigned to naltrexone (50 mg/d) or placebo based on their OPRM1 genotype (75 G-allele carriers and 77 A-allele homozygotes) and also genotyped for DAT1 VNTR (9 vs. 10 repeats) or COMT SNP (val/val vs. met carriers). Heavy drinking days (%HDD) were evaluated over 16 weeks and at the end of treatment. Effect sizes (d) for naltrexone response were calculated based on genotypes. RESULTS: Naltrexone, relative to placebo, significantly reduced %HDD among OPRM1 G carriers who also had DAT1 10/10 (p = 0.021, d = 0.72) or COMT val/val genotypes (p = 0.05, d = 0.80), and to a lesser degree in those OPRM1 A homozygotes who were also DAT1 9-repeat carriers (p = 0.09, d = 0.70) or COMT met carriers (p = 0.03, d = 0.63). All other genotype combinations showed no differential response to naltrexone. Diarrhea/abdominal pain was more prominent in OPRM1 A homozygotes who were also DAT 9 or COMT met carriers. CONCLUSIONS: These results suggest that individuals with AUD with a more opioid-responsive genotype (OPRM1 G carriers) respond better to naltrexone if they have genotypes indicating normal/less dopamine tone (DAT1 10,10 or COMT val,val), while those with a less responsive opioid-responsive genotype (OPRM1 A homozygotes) respond better to naltrexone if they have genotypes indicating greater dopamine tone (DAT1 9-repeat or COMT met carriers). These results could lead to more personalized AUD treatments.

Long noncoding RNA C2dat1 protects H9c2 cells against hypoxia injury by downregulating miR-22.

Myocardial ischemia is accompanied with hypoxia injury in myocardial cells. Long noncoding RNAs (lncRNA) CAMK2D-associated transcript 1 (C2dat1) C2dat1) has been linked with several ischemic diseases. However, the investigation regarding its role in myocardial ischemia is relatively rare. The aim of this study was to examine the role of C2dat1 in hypoxia response in H9c2 cells. H9c2 cells were subjected to hypoxia to evoke cell damage. Expressions of C2dat1, miR-22, and VEGF in H9c2 cells were altered by transfection, and then cell survival, migration, and invasion were respectively assessed posttransfection. Regulatory relationship between C2dat1, miR-22, and VEGF, as well as the involvement of PI3K/AKT/mTOR and JAK/STAT3 pathways in H9c2 cells injury was then studied. C2dat1 upregulation ameliorated hypoxia injury in H9c2 cells due to the increased viability, migration, and invasion, as well as the decreased apoptosis. miR-22 was negatively regulated by C2dat1. The effects of C2dat1 on H9c2 cells injured by hypoxia were attenuated when miR-22 was overexpressed. VEGF was a target gene of miR-22, and VEGF exerted similar protective effects to C2dat1. Finally, we found that silence of C2dat1 deactivated PI3K/AKT/mTOR and JAK/STAT3 pathways via regulating miR-22 and its downstream gene VEGF. C2dat1-miR-22-VEGF axis could regulate hypoxia injury in H9c2 cells. C2dat1 alleviated hypoxia injury possibly via downregulating miR-22, then upregulating VEGF, which further enhancing the activation of PI3K/AKT/mTOR and JAK/STAT3 pathways.

Long noncoding RNAs C2dat1 enhances vascular smooth muscle cell proliferation and migration by targeting MiR-34a-5p.

Deregulated proliferation of vascular smooth muscle cells (VSMCs) is one common phenomenon of atherosclerosis progression. Long noncoding RNAs (lncRNAs) are one group of noncoding RNAs that play essential roles in many cell biological processes, including cell development, growth, and migration. However, the role of a novel calcium/calmodulin-dependent protein kinase type II subunit delta (CAMK2D)-associated lncRNA, CAMK2D-associated transcript 1 (C2dat1), in VSMCs is still uncovered. In this study, we showed that the expression level of C2dat1 was higher in coronary artery disease (CAD) tissues than in normal arterial tissues and the C2dat1 expression level was upregulated in the proliferating VSMC after being treated with PDGF-bb or TNF-α. In addition, we indicated that overexpression of C2dat1 promoted VSMC growth and enhanced proliferating cell nuclear antigen (PCNA) expression in VSMC. Moreover, ectopic expression of C2dat1 increased VSMC migration. Furthermore, we showed that elevated expression of C2dat1 suppressed microRNA-34a (miR-34a) expression and promoted sirtuin 1 (SIRT1) expression, which was a direct target gene of miR-34a. We demonstrated that the expression level of miR-34a was lower in CAD tissues than in normal arterial tissues and the expression of miR-34a was negatively correlated with C2dat1 expression. Restored expression of C2dat1 increased VSMC proliferation and migration through promoting SIRT1 expression. These data suggested that lncRNA C2dat1 might be a potential therapeutic target to promote VSMC growth and migration in CAD.

Association study and a systematic meta-analysis of the VNTR polymorphism in the 3'-UTR of dopamine transporter gene and attention-deficit hyperactivity disorder.

Attention-deficit hyperactivity disorder (ADHD) has been postulated to associate with dopaminergic dysfunction, including the dopamine transporter (DAT1). Several meta-analyses showed small but significant association between the 10-repeat allele in the DAT1 gene in 3'-untranslated region variant number tandem repeat polymorphism and child and adolescent ADHD, whereas in adult ADHD the 9-repeat allele was suggested to confer as risk allele. Interestingly, recent evidence indicated that the long-allele variants (10 repeats and longer) might confer to lower expression of the transporter in comparison to the short-allele. Therefore, we assessed here the association in samples consisting of families with child and adolescent ADHD as well as a case-control sample, using either the 10- versus 9-repeat or the long- versus short-allele approach. Following, we conducted a systematic review and meta-analysis, including family and case-control studies, using the two aforementioned approaches as well as stratifying to age and ethnicity. The first approach (10-repeat) resulted in nominal significant association in child and adolescent ADHD (OR 1.1050 p = 0.0128), that became significant stratifying to European population (OR 1.1301 p = 0.0085). The second approach (long-allele) resulted in significant association with the whole ADHD population (OR 1.1046 p = 0.0048), followed by significant association for child and adolescent ADHD (OR 1.1602 p = 0.0006) and in Caucasian and in European child and adolescent ADHD (OR 1.1310 p = 0.0114; OR 1.1661 p = 0.0061; respectively). We were not able to confirm the association reported in adults using both approaches. In conclusion, we found further indication for a possible DAT1 gene involvement; however, further studies should be conducted with stringent phenotyping to reduce heterogeneity, a limitation observed in most included studies.

Methylation of the dopamine transporter gene in blood is associated with striatal dopamine transporter availability in ADHD: A preliminary study.

Dopamine transporters (DAT) are implicated in the pathogenesis and treatment of attention-deficit hyperactivity disorder (ADHD) and are upregulated by chronic treatment with methylphenidate, commonly prescribed for ADHD. Methylation of the DAT1 gene in brain and blood has been associated with DAT expression in rodents' brains. Here we tested the association between methylation of the DAT1 promoter derived from blood and DAT availability in the striatum of unmedicated ADHD adult participants and in that of healthy age-matched controls (HC) using Positron Emission Tomography (PET) and [11 C]cocaine. Results showed no between-group differences in DAT1 promoter methylation or striatal DAT availability. However, the degree of methylation in the promoter region of DAT1 correlated negatively with DAT availability in caudate in ADHD participants only. DAT availability in VS correlated with inattention scores in ADHD participants. We verified in a postmortem cohort with ADHD diagnosis and without, that DAT1 promoter methylation in peripheral blood correlated positively with DAT1 promoter methylation extracted from substantia nigra (SN) in both groups. In the cohort without ADHD diagnosis, DAT1 gene expression in SN further correlated positively with DAT protein expression in caudate; however, the sample size of the cohort with ADHD was insufficient to investigate DAT1 and DAT expression levels. Overall, these findings suggest that peripheral DAT1 promoter methylation may be predictive of striatal DAT availability in adults with ADHD. Due to the small sample size, more work is needed to validate whether DAT1 methylation in blood predicts DAT1 methylation in SN in ADHD and controls.

Dopamine Transporter Gene Methylation is Associated with Nucleus Accumbens Activation During Reward Processing in Healthy but not Alcohol-Dependent Individuals.

BACKGROUND: Alcohol's reinforcement is mediated by dopamine signaling in the ventral striatum, which is modulated by the dopamine transporter (DAT). We hypothesized that methylomic variation in the DAT gene (DAT1/SLC6A3) affects DAT expression, thus contributing to differences in brain reward circuitry in individuals with alcohol dependence (ALC). METHODS: Blood from 45 recently detoxified ALC and 45 healthy control (HC) individuals was used to assess DNA methylation across 5 functional regions of SLC6A3. Participants completed the monetary incentive delay task in a 3-Tesla magnetic resonance imaging (MRI) scanner. Employing regression models, we examined effects of SLC6A3 methylation on nucleus accumbens (NAc) blood-oxygen-level dependent (BOLD) responses during anticipation of high/low reward/loss. RESULTS: Results showed that decreased methylation of the promoter region of SLC6A3 predicted NAc activation during high loss anticipation (p = 0.028) and low loss anticipation (at trend-level; p = 0.057) in HC but not in individuals with ALC. Specifically, percentage of methylation at 2 CpG sites, located -1,001 and -993 base pairs from the transcription start site, accounted for significant variability in NAc activation in the HC group during high (ps ≤ 0.010) and low (ps ≤ 0.006) loss anticipation. There was no effect on reward anticipation. Furthermore, promoter methylation was positively associated with age, which replicates previous findings. CONCLUSIONS: Our data suggest that methylation in the promoter region of SLC6A3 predicts NAc activation during the anticipation of monetary loss in HCs. However, this effect was not present in the ALC group, suggesting that epigenetic regulation of striatal DAT expression might be disrupted in ALC, which may contribute to previously reported differences in sensitivity to reward and punishment in this population. Alternatively, it is possible that a similar relationship in the ALC group remained undetected possibly due to methodological limitations inherent in functional MRI (e.g., poor spatial resolution, low signal-to-noise ratio) that generally restrict interpretations regarding mechanisms of epigenetic factors involved in group differences in BOLD responses. Future neuroimaging studies are needed to further elucidate the relationship between SLC6A3 methylation and NAc activation in ALC.

The Catechol-O-Methyltransferase and Dopamine Transporter Genes Moderated the Impact of Peer Relationships on Adolescent Depressive Symptoms: A Gene-Gene-Environment Study.

Behavioral genetics studies and new empirical evidence suggest that depression cannot simply be explained by the influence of single genes but that gene-gene-environment interactions are important to better understanding the etiology of depression. The present study investigated the main and interactive effects of COMT gene Val158Met polymorphism, DAT1 gene rs27072 polymorphism, and peer relationships (i.e., peer acceptance and rejection) on adolescent depressive symptoms. In a sample of 1045 Chinese Han adolescents (Mage = 12.34 ± 0.47 years, 50.1% girls), saliva samples, self-reported depressive symptoms and within-classroom peer nominations were collected. After controlling for gender, age, and SES, the three-way interaction of COMT, DAT1, and peer acceptance significantly concurrently predicted adolescent depressive symptoms. Adolescents with ValVal genotype of COMT and CC genotype of DAT1 were more sensitive to acceptance, compared to their counterparts carrying other combined genotypes. However, a similar three-way interaction was not significant in the case of peer rejection. Additionally, the split-half validation generally replicated these findings. More importantly, this study underscores complex polygenic underpinnings of depression and lends support for the gene-gene-environment interactions implicated in the etiology of depressive symptoms.

A Caenorhabditis elegans model to study dopamine transporter deficiency syndrome.

Dopamine transporter deficiency syndrome (DTDS) is a novel autosomal recessive disorder caused by mutations in the dopamine transporter (DAT), which leads to the partial or total loss of function of the protein. DTDS is a pharmacoresistant syndrome and very little is known about its neurobiology, in part due to the lack of relevant animal models. The objective of this study was to establish the first animal model for DTDS with strong construct validity, using Caenorhabditis elegans, and to investigate the in vivo role played by DTDS-related mutations found in human DAT (hDAT). We took advantage of a C. elegans knockout for the hDAT orthologue, cedat-1, to obtain genetically humanized animals bearing hDAT, in the wild type and in two mutated forms (399delG and 941C>T), in a null background. In C. elegans transgenic animals expressing the human wild-type form, we observed a rescue of the knockout phenotype, as assessed using two well-established paradigms, known to be regulated by the endogenous uptake of dopamine or 6-hydroxydopamine (6-OHDA) by DAT. The less severe mutation (941C>T) was able to partially rescue only one of the knockout phenotypes, whereas the 399delG mutation impaired DAT function in both phenotypic paradigms. Our in vivo phenotypic findings demonstrate a functional conservation between human and nematode DAT and validate previous in vitro indications of the loss of function of hDAT in carriers of DTDS-related mutations. Taken together, these observations establish C. elegans as a novel animal model for fast and inexpensive screening of hDAT mutations in functional and in vivo tests.

Association between the Intron 8 VNTR Polymorphism of the DAT1 Gene and Crack Cocaine Addiction.

BACKGROUND: This study aims to compare allele and genotype frequencies of a 30-bp variable number of tandem repeats (VNTR) polymorphism of the DAT1 gene, located at intron 8, between adult crack cocaine users and nonaddicted individuals. Due to its involvement in drug addiction, this gene is a good candidate for molecular studies. METHODS: A cross-sectional sample of 239 current adult crack abusers or dependents from in- and outpatient clinics and 211 control individuals was collected in Brazil. They were evaluated using ASRS, ASI-6, WAIS-III, and MINI assessments. DNA samples extracted from whole blood were genotyped for the intron 8 VNTR in DAT1. RESULTS: Logistic regression analysis was performed and controlled for gender, age, ethnicity, educational level, and comorbidities of clinical interest (generalized anxiety disorder, suicide risk, major depressive episode, and attention deficit/hyperactivity disorder). This analysis showed that the 6R6R genotype was associated with crack cocaine addiction (OR = 1.844; CI = 1.101-3.089; p = 0.020). CONCLUSIONS: Our results are consistent with the role of DAT1 in the neurobiology of drug addiction. Nevertheless, the study of other genes, environmental factors, and their interactions is also important to gain a broader understanding of this condition.

A genetic marker of risk in HIV-infected individuals with a history of hazardous drinking.

Impulsivity and sensation seeking have been linked to hazardous drinking, increased sexual risk behaviors, and lower treatment adherence among persons living with HIV (PLH). The dopamine active transporter1 (DAT1or SLC6A3) gene has been linked to impulsivity and sensation seeking in several populations but has not been investigated among populations of PLH. This study used data from 201 PLH who report a recent history of heavy episodic drinking. Results indicate that DAT1*10R vs DAT1*9R genotype was related to higher propensity for risk taking (standardized difference score (d) = 0.30 [95% CI: 0.02;0.59]), more hazardous drinking (d = 0.35 [0.05;0.64]), and more condomless sex (rate ratio (RR)= 2.35[1.94; 2.85]), but were counter-intuitively associated with fewer sexual partners (RR = 0.65[0.43;0.91]) and possibly better treatment adherence (d = 0.32 [-0.01;0.65]). Results are consistent with the suggested associations between DAT1 and risk-taking behavior. The counter-intuitive finding for partner selection and treatment adherence may be evidence of additional factors that place PLH at risk for engaging in hazardous drinking as well as relationship difficulties and problems with treatment adherence (e.g., depressive symptoms, avoidant coping, trauma history). Caution is required when using a single gene variant as a marker of complex behaviors and these findings need to be replicated using larger samples and additional variants.

Is prepulse modification altered by continuous theta burst stimulation? DAT1 genotype and motor threshold interact on prepulse modification following brain stimulation.

Previous studies suggest an inhibitory top-down control of the amygdala by the prefrontal cortex (PFC). Both brain regions play a role in the modulation of prepulse modification (PPM) of the acoustic startle response by a pre-stimulus. Repetitive transcranial magnetic stimulation (rTMS) can modulate the activity of the PFC and might thus affect PPM. This study tested the effect of inhibitory rTMS on PPM accounting for a genetic variant of the dopamine transporter gene (DAT1). Healthy participants (N = 102) were stimulated with continuous theta burst stimulation (cTBS, an intense form of inhibitory rTMS) or sham treatment over the right PFC. Afterwards, during continuous presentation of a background white noise a louder noise burst was presented either alone (control startle) or preceded by a prepulse. Participants were genotyped for a DAT1 variable number tandem repeat (VNTR) polymorphism. Two succeeding sessions of cTBS over the right PFC (2 × 600 stimuli with a time lag of 15 min) attenuated averaged prepulse inhibition (PPI) in participants with a high resting motor threshold. An attenuation of PPI induced by prepulses with great distances to the pulse (480, 2000 ms) was observed following active cTBS in participants that were homozygous carriers of the 10-repeat-allele of the DAT1 genotype and had a high resting motor threshold. Our results confirm the importance of the prefrontal cortex for the modulation of PPM. The effects were observed in participants with a high resting motor threshold only, probably because they received a higher dose of cTBS. The effects in homozygous carriers of the DAT1 10-repeat allele confirm the relevance of dopamine for PPM. Conducting an exploratory study we decided against the use of a correction for multiple testing.