A 40-bp VNTR polymorphism in the 3'-untranslated region of DAT1/SLC6A3 is associated with ADHD but not with alcoholism

Role of glycogen synthase kinase-3β in dependence and abuse liability of alcohol

BACKGROUND

Alcohol is a major abused drug worldwide that contributes substantially to health and social problems. These problems result from acute alcohol overuse as well as chronic use, leading to alcohol use disorder (AUD). A major goal of this field is to establish a treatment for alcohol abuse and dependence in patients with AUD. The central molecular mechanisms of acute alcohol actions have been extensively investigated in rodent models.

AIMS

One of the central mechanisms that may be involved is glycogen synthase kinase-3β (GSK-3β) activity, a key enzyme involved in glycogen metabolism but which has crucial roles in numerous cellular processes. Although the exact mechanisms leading from acute alcohol actions to these chronic changes in GSK-3β function are not yet clear, GSK-3β nonetheless constitutes a potential therapeutic target for AUD by reducing its function using GSK-3β inhibitors. This review is focused on the correlation between GSK-3β activity and the degree of alcohol consumption.

METHODS

Research articles regarding investigation of effect of GSK-3β on alcohol consumption in rodents were searched on PubMed, Embase, and Scopus databases using keywords "glycogen synthase kinase," "alcohol (or ethanol)," "intake (or consumption)," and evaluated by changes in ratios of pGSK-3βSer9/pGSK-3β.

RESULTS

In animal experiments, GSK-3β activity decreases in the brain under forced and voluntary alcohol consumption while GSK-3β activity increases under alcohol-seeking behavior.

CONCLUSIONS

Several pieces of evidence suggest that alterations in GSK-3β function are important mediators of chronic ethanol actions, including those related to alcohol dependence and the adverse effects of chronic ethanol exposure.

Assessment of the Genetic Characteristics of a Generation Born during a Long-Term Socioeconomic Crisis

BACKGROUND

A socioeconomic crisis in Russia lasted from 1991 to 1998 and was accompanied by a sharp drop in the birth rate. The main factor that influenced the refusal to have children during this period is thought to be prolonged social stress.

METHODS

comparing frequencies of common gene variants associated with stress-induced diseases among generations born before, after, and during this crisis may show which genes may be preferred under the pressure of natural selection during periods of increased social stress in urban populations.

RESULTS

In the "crisis" group, a statistically significant difference from the other two groups was found in rs6557168 frequency (p = 0.001); rs4522666 was not in the Hardy-Weinberg equilibrium in this group, although its frequency did not show a significant difference from the other groups (p = 0.118). Frequencies of VNTRs in SLC6A3 and MAOA as well as common variants rs17689918 in CRHR1, rs1360780 in FKBP5, rs53576 in OXTR, rs12720071 and rs806377 in CNR1, rs4311 in ACE, rs1800497 in ANKK1, and rs7412 and rs429358 in APOE did not differ among the groups.

CONCLUSIONS

a generation born during a period of prolonged destructive events may differ from the rest of the gene pool of the population in some variants associated with personality traits or stress-related disorders.

Association between opioid and dopamine receptor gene polymorphisms OPRM1 rs1799971, DAT VNTR 9-10 repeat allele, DRD1 rs4532 and DRD2 rs1799732 and alcohol dependence: an ethnicity oriented meta-analysis

OBJECTIVE

We carried out a meta-analysis of four opioid and dopamine candidate gene polymorphisms having conflicting results in prior literature, namely OPRM1 rs1799971, DAT VNTR 9-10 repeat, DRD1 rs4532 and DRD2 rs1799732, to clarify their association with alcohol dependence and further stratified results by ethnicity to analyze possible ethnicity-mediated effects.

METHODS

Inclusion criteria: case-control studies assessing the association between OPRM1 rs1799971, DAT VNTR 9/10 repeat allele, DRD1 rs4532 and DRD2 rs1799732 with alcohol dependence, with sufficient data available to calculate the odds ratio (OR) within a 95% confidence interval. Exclusion criteria: studies of quantitative measures of alcohol consumption, response to medications or analyses of other markers in the candidate genes, studies without controls, animal studies and lack of genotyping data. Information sources were PubMed, Google Scholar and ScienceDirect databases, all of which were searched for articles published till 2021. Heterogeneity between studies and publication bias, subgroup analyses and sensitivity analyses were carried out.

RESULTS

A total of 41 published studies were included in the current meta-analysis. For the OPRM1 gene, there was a statistically significant association in the Asian population with a pooled OR of 1.707 (95% CI, 1.32-2.20 P  < 0.0001) and 1.618 (95% CI, 1.16-2.26 P  = 0.005) in the additive and dominant genetic models. For DAT VNTR 9/10 repeat, a statistically significant association of the risk vs. common allele was observed in AD with a pooled OR of 1.104 (95% CI, 1.00-1.21 P  = 0.046) in the allele model and the additive genetic model in the Caucasian population with pooled OR of 1.152 (95% CI, 1.01-1.31 P  = 0.034).

CONCLUSION

Results indicate that some of the effects may be ethnicity-specific.

OTHER

The meta-analysis has been registered in the CRD PROSPERO (CRD42023411576).

Can biomarkers be used to diagnose attention deficit hyperactivity disorder?

Currently, the diagnosis of attention deficit hyperactivity disorder (ADHD) is solely based on behavioral tests prescribed by the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). However, biomarkers can be more objective and accurate for diagnosis and evaluating treatment efficacy. Thus, this review aimed to identify potential biomarkers for ADHD. Search terms “ADHD,” and “biomarker” combined with one of “protein,” “blood/serum,” “gene,” and “neuro” were used to identify human and animal studies in PubMed, Ovid Medline, and Web of Science. Only papers in English were included. Potential biomarkers were categorized into radiographic, molecular, physiologic, or histologic markers. The radiographic analysis can identify specific activity changes in several brain regions in individuals with ADHD. Several molecular biomarkers in peripheral blood cells and some physiologic biomarkers were found in a small number of participants. There were no published histologic biomarkers for ADHD. Overall, most associations between ADHD and potential biomarkers were properly controlled. In conclusion, a series of biomarkers in the literature are promising as objective parameters to more accurately diagnose ADHD, especially in those with comorbidities that prevent the use of DSM-5. However, more research is needed to confirm the reliability of the biomarkers in larger cohort studies.

Attention-deficit/hyperactive disorder updates

Background

Attention-deficit/hyperactive disorder (ADHD) is a neurodevelopmental disorder that commonly occurs in children with a prevalence ranging from 3.4 to 7.2%. It profoundly affects academic achievement, well-being, and social interactions. As a result, this disorder is of high cost to both individuals and society. Despite the availability of knowledge regarding the mechanisms of ADHD, the pathogenesis is not clear, hence, the existence of many challenges especially in making correct early diagnosis and provision of accurate management.

Objectives

We aimed to review the pathogenic pathways of ADHD in children. The major focus was to provide an update on the reported etiologies in humans, animal models, modulators, therapies, mechanisms, epigenetic changes, and the interaction between genetic and environmental factors.

Methods

References for this review were identified through a systematic search in PubMed by using special keywords for all years until January 2022.

Results

Several genes have been reported to associate with ADHD: DRD1, DRD2, DRD4, DAT1, TPH2, HTR1A, HTR1B, SLC6A4, HTR2A, DBH, NET1, ADRA2A, ADRA2C, CHRNA4, CHRNA7, GAD1, GRM1, GRM5, GRM7, GRM8, TARBP1, ADGRL3, FGF1, MAOA, BDNF, SNAP25, STX1A, ATXN7, and SORCS2. Some of these genes have evidence both from human beings and animal models, while others have evidence in either humans or animal models only. Notably, most of these animal models are knockout and do not generate the genetic alteration of the patients. Besides, some of the gene polymorphisms reported differ according to the ethnic groups. The majority of the available animal models are related to the dopaminergic pathway. Epigenetic changes including SUMOylation, methylation, and acetylation have been reported in genes related to the dopaminergic pathway.

Conclusion

The dopaminergic pathway remains to be crucial in the pathogenesis of ADHD. It can be affected by environmental factors and other pathways. Nevertheless, it is still unclear how environmental factors relate to all neurotransmitter pathways; thus, more studies are needed. Although several genes have been related to ADHD, there are few animal model studies on the majority of the genes, and they do not generate the genetic alteration of the patients. More animal models and epigenetic studies are required.

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.

Children’s ADHD and Dysregulation Problems, DAT1 Genotype and Methylation, and their Interplay with Family Environment

Background

International literature has underlined the complex interplay between genetic and environmental variables in shaping children’s emotional-behavioral functioning.

Objective

This study aimed to explore the dynamic relationship between children’s Dopamine Transporter (DAT1) genotype and methylation, and maternal and paternal affective environment, on children’s Attention Deficit Hyperactivity Disorder (ADHD) problems and dysregulation problems.

Method

In a community sample of 76 families with school-aged children, we assessed children’s DAT1 genotype and methylation, their own ADHD problems and dysregulation profile (CBCL 6–18 DP), and maternal and paternal psychopathological risk, parenting stress, and marital adjustment. Hierarchical regressions were carried out to verify the possible moderation of children’s genotype on the relationship between children’s methylation and psychopathological risk, parental environment and children’s methylation, and parental environment and children’s psychopathological risk.

Results

The levels of methylation at M1 CpG significantly predicted ADHD problems among children with 10/10 genotype, whereas high levels of methylation at M6 CpG predicted low ADHD problems for children with 9/x genotype. High levels of methylation at M3 CpG were associated with high scores of CBCL DP. DAT1 genotype moderated the relationship between maternal and paternal variables with children’s methylation and psychopathological risk. The scores of maternal and paternal Dyadic Adjustment Scale showed indirect effects on children’s methylation and psychopathological risk in relation to those exerted by risk factors.

Conclusion

Our study has supported the emerging evidence on the complex nature of children’s emotional-behavioral functioning and the associated risk and protective factors, with important implications for the planning of preventive programs.

Altering the development of the dopaminergic system through social play in rats: Implications for anxiety, depression, hyperactivity, and compulsivity

Dopamine is essential to many functions like reward, motivation, and attention; when its neural pathways do not function properly, various disorders (e.g., anxiety, depression, hyperactivity, compulsions) can arise. Truncated-DAT rats display persistent stereotypies and aggressiveness; hence they are a new valuable animal model to study the pathogenesis of these disorders. The focus of research is often on the individual epigenetic determinants and much less on the impact of social experiences. Here, we investigate the developmental impact of the social environment on adolescent wild type (WT) rats. We divided subjects at weaning into three groups: living with another adolescent (WT Peer), with a WT adult, or with a truncated-DAT one, and we observed homecage social behavior of these pairs (play, jump, victory, and "bullying") during whole adolescence. When adult, we observed the same subjects in plus maze, forced swim, and social preference tests to measure levels of anxiety, depression, and quality of social interactions. Compared to the other groups, WT rats that had spent their adolescence with a truncated-DAT adult as companion show more anxious, depressive, hyperactive, impulsive, and compulsive behaviours. Results confirm that social interactions and healthy play (i.e., when play has behavioural, social, and psychomotor rewards that support the cognitive, emotional and physical development of the individual) are essential to neurobehavioral maturation. Conversely, anomalous interactions like poor play and "bullying" in developing rats may impact onto their dopaminergic system. Consequently, an impoverished social play could be one of the factors contributing to the appearance of putative indexes of attention deficit hyperactivity disorder (ADHD) and\or obsessive-compulsive disorder (OCD).

Genome-wide characterization of human minisatellite VNTRs: population-specific alleles and gene expression differences

Variable Number Tandem Repeats (VNTRs) are tandem repeat (TR) loci that vary in copy number across a population. Using our program, VNTRseek, we analyzed human whole genome sequencing datasets from 2770 individuals in order to detect minisatellite VNTRs, i.e., those with pattern sizes ≥7 bp. We detected 35 638 VNTR loci and classified 5676 as commonly polymorphic (i.e. with non-reference alleles occurring in >5% of the population). Commonly polymorphic VNTR loci were found to be enriched in genomic regions with regulatory function, i.e. transcription start sites and enhancers. Investigation of the commonly polymorphic VNTRs in the context of population ancestry revealed that 1096 loci contained population-specific alleles and that those could be used to classify individuals into super-populations with near-perfect accuracy. Search for quantitative trait loci (eQTLs), among the VNTRs proximal to genes, indicated that in 187 genes expression differences correlated with VNTR genotype. We validated our predictions in several ways, including experimentally, through the identification of predicted alleles in long reads, and by comparisons showing consistency between sequencing platforms. This study is the most comprehensive analysis of minisatellite VNTRs in the human population to date.

Variable number tandem repeats - Their emerging role in sickness and health

Understanding the mechanisms regulating tissue specific and stimulus inducible regulation is at the heart of understanding human biology and how this translates to wellbeing, the ageing process, and disease progression. Polymorphic DNA variation is superimposed as an extra layer of complexity in such processes which underpin our individuality and are the focus of personalized medicine. This review focuses on the role and action of repetitive DNA, specifically variable number tandem repeats and SINE-VNTR-Alu domains, highlighting their role in modification of gene structure and gene expression in addition to their polymorphic nature being a genetic modifier of disease risk and progression. Although the literature focuses on their role in disease, it illustrates their potential to be major contributors to normal physiological function. To date, these elements have been under-reported in genomic analysis due to the difficulties in their characterization with short read DNA sequencing methods. However, recent advances in long read sequencing methods should resolve these problems allowing for a greater understanding of their contribution to a host of genomic and functional mechanisms underlying physiology and disease.

Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology

Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H⁺ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b^0,+AT-rBAT and the SLC6 family heteromer B⁰AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.

Gray matter volume and microRNA levels in patients with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder often characterized by gray matter (GM) volume reductions. MicroRNAs, which participate in regulating gene expression, potentially influence neurodevelopment. This study aimed to explore whether differential GM volume is associated with differential miRNA levels in ADHD patients. We recruited a total of 30 drug-naïve patients with ADHD (mean age 10.6 years) and 25 healthy controls (mean age 10.6 years) that underwent a single session of 3.0-T whole brain structural MRI scanning. RNA samples from the participants' white blood cells were collected to identify the ΔCt values of three miRNAs (miR-30e-5p, miR-126-5p, and miR-140-3p) using the real-time quantitative reverse transcription polymerase chain reaction. In comparison to the control group, ADHD patients demonstrated a significantly lower GM volume in the cingulate gyrus, left middle temporal gyrus, right middle occipital gyrus, left fusiform gyrus, and significantly higher ΔCt values of miR-30e-5p, miR-126-5p, and miR-140-3p. In the ADHD group, the GM volume of cingulate gyrus and left fusiform gyrus was negatively correlated with the ΔCt values of miR-30e-5p, miR-140-3p. The GM volume of left fusiform gyrus was negatively correlated to ADHD behavioral symptoms. Using structural equation modeling (SEM), we observed that the effect of miR-140-3p on hyperactivity/impulsivity symptoms was mediated by left fusiform gyrus. Our findings support that GM volume reduction and miRNA increases may be biomarkers for ADHD in children and adolescents. Expression levels of miRNAs may affect the development of brain structures and further participate in the pathophysiology of ADHD.

Dopamine transporter availability in alcohol and opioid dependent subjects - a 99mTc-TRODAT-1SPECT imaging and genetic association study

Drug dependence associated with increased dopamine neurotransmission and neuroplastic changes is influenced by Dopamine transporters (DAT) which are modulated by genetic and epigenetic factors. This study assesses DAT availability in relation to the 40bp DAT1 VNTR (genetic) and DAT1 promoter methylation (epigenetic) changes in patients with alcohol dependence (AD) and opioid dependence (OD). A total of 60 subjects (n=20 each of AD, OD and controls) were recruited. SPECT/CT imaging using ^99mTc-TRODAT-1 was performed for measuring striatal DAT availability and DNA screened to check DAT1promoter methylation and 40bp VNTR polymorphism. SPECT/CT imaging revealed significant decrease in DAT availability in the striatum and putamen and significant increase in DAT1 promoter methylation in AD compared to control and OD. The 40bp VNTR distribution was similar in all three groups with 10repeat and 9repeat alleles being the most common. The AD individuals with DAT1promoter methylation showed significantly lower TRODAT-1 uptake compared to the ones with no methylation. AD individuals homozygous for the 10repeat VNTR also showed reduced DAT availability. This is the first imaging study using ^99mTc-TRODAT-1 from India documenting significantly reduced striatal DAT availability, increased DAT methylation and frequency of 10repeat individuals associated with decreased DAT availability in AD.

Emotional-Behavioral Regulation, Temperament and Parent-Child Interactions Are Associated with Dopamine Transporter Allelic Polymorphism in Early Childhood: A Pilot Study

International research has highlighted the role played by individual genetic polymorphism, children’s emotional-behavioral functioning, and quality of parent–child feeding interaction in shaping children’s development. Few studies have focused on the dopamine transporter (DAT1) gene in these processes. In a community sample of 81 families with young children aged between 19 and 28 months (37 males and 44 females), this pilot study aimed to explore possible relationships between children’s DAT1 genotype (9/x: 9/9, 9/19 contrasted to 10/10), their own psychological profiles, parental psychopathological risk, and the quality of mother–child and father–child feeding interactions. Children’s DAT1 genotype was assessed collecting DNA through buccal; children’s temperament and emotional-behavioral regulation, and parental psychopathological risk were assessed, respectively, through report-form and self-report instruments; then, dyadic exchanges were videotaped during a mealtime, and coded based on the Scala di Valutazione dell′Interazione Alimentare (SVIA). Results showed significant differences in the variables under study based on children’s DAT1 genotype, with a higher risk associated with the 10/10. Our findings have provided preliminary new evidence on the relationship between a different child’s polymorphisms, their own emotional-behavioral functioning, and the quality of the family environment, with important implications for the planning of more targeted prevention programs.

Prevalence of Some Genetic Risk Factors for Nicotine Dependence in Ukraine

Tobacco smoking is known to be a strong risk factor for developing many diseases. The development and severity of smoking dependence results from interaction of environmental and lifestyle factors, psycho-emotional predispositions, and also from genetic susceptibility. In present study, we investigated polymorphic variants in genes contributed to nicotine dependence, as well as to increased impulsivity, known to be an important risk factor for substance use disorders, in Ukraine population. The genotype frequencies at CYP2A6, DNMT3B, DRD2, HTR2A, COMT, BDNF, GABRA2, CHRNA5, and DAT1 polymorphisms were determined in 171 Ukraine residents, and these data were compared with data for several other European populations and main ethnic groups. It has been found that genotype frequencies for all studied loci are in Hardy-Weinberg equilibrium in the Ukrainian population and correspond to the respective frequencies in European populations. These findings suggest a similar impact of these loci on nicotine dependence in Ukraine. Further studies with larger sample sizes are, however, needed to draw firm conclusions about the effect size of these polymorphisms.

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.

The dopamine transporter role in psychiatric phenotypes

The dopamine transporter (DAT) is one of the most relevant and investigated neurotransmitter transporters. DAT is a plasma membrane protein which plays a homeostatic role, controlling both extracellular and intracellular concentrations of dopamine (DA). Since unbalanced DA levels are known to be involved in numerous mental disorders, a wealth of investigations has provided valuable insights concerning DAT role into normal brain functioning and pathological processes. Briefly, this extensive but non-systematic review discusses what is recently known about the role of SLC6A3 gene which encodes the dopamine transporter in psychiatric phenotypes. DAT protein, SLC6A3 gene, animal models, neuropsychology, and neuroimaging investigations are also concisely discussed. To conclude, current challenges are reviewed in order to provide perspectives for future studies.

Blood-Bourne MicroRNA Biomarker Evaluation in Attention-Deficit/Hyperactivity Disorder of Han Chinese Individuals: An Exploratory Study

Background: Attention-deficit/hyperactivity disorder (ADHD) is a highly genetic neurodevelopmental disorder, and its dysregulation of gene expression involves microRNAs (miRNAs). The purpose of this study was to identify potential miRNAs biomarkers and then use these biomarkers to establish a diagnostic panel for ADHD. Design and methods: RNA samples from white blood cells (WBCs) of five ADHD patients and five healthy controls were combined to create one pooled patient library and one control library. We identified 20 candidate miRNAs with the next-generation sequencing (NGS) technique (Illumina). Blood samples were then collected from a Training Set (68 patients and 54 controls) and a Testing Set (20 patients and 20 controls) to identify the expression profiles of these miRNAs with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). We used receiver operating characteristic (ROC) curves and the area under the curve (AUC) to evaluate both the specificity and sensitivity of the probability score yielded by the support vector machine (SVM) model. Results: We identified 13 miRNAs as potential ADHD biomarkers. The ΔCt values of these miRNAs in the Training Set were integrated to create a biomarker model using the SVM algorithm, which demonstrated good validity in differentiating ADHD patients from control subjects (sensitivity: 86.8%, specificity: 88.9%, AUC: 0.94, p < 0.001). The results of the blind testing showed that 85% of the subjects in the Testing Set were correctly classified using the SVM model alignment (AUC: 0.91, p < 0.001). The discriminative validity is not influenced by patients' age or gender, indicating both the robustness and the reliability of the SVM classification model. Conclusion: As measured in peripheral blood, miRNA-based biomarkers can aid in the differentiation of ADHD in clinical settings. Additional studies are needed in the future to clarify the ADHD-associated gene functions and biological mechanisms modulated by miRNAs.

Dopamine transporter gene polymorphism in children with ADHD: A pilot study in Indonesian samples

INTRODUCTION

Several studies showed that DAT1 polymorphism closed related with ADHD although the results were not consistently found. Studies in China, South Korea, Japan revealed that 10-repeat allele gave a risk for ADHD. Based on that understanding, this study tried to identify whether the similar polymorphism of DAT1 was also apparent in Indonesian children with ADHD.

METHOD

This was a case - control study. Case was 50 Indonesian origin children with ADHD and without any other mental disorders and metal retardation. Control is Indonesian origin children without ADHD, other mental disorders and mental retardation. ADHD diagnosis was taken after doing the psychiatric interview and observation based on the DSM-IV TR diagnostic criteria for ADHD at the Child and Adolescent Psychiatry Out-patient Clinic, Dr. Cipto Mangunkusumo National Referral Hospital - Faculty of Medicine Universitas Indonesia. DNA isolation, DNA purity and concentration were measured. PCR was done by using a primer based on Homo sapiens solute carrier family 6 (neurotransmitter transporter), member 3 (SLC6A3), RefSeq Gene on chromosome 5 with accession number NG_015885.1. To identify the serial of repeated allele, we used the sequencing technique.

RESULTS

There were 47 children with ADHD and 48 children without ADHD that involved in the final analysis. The mean of age amongst ADHD group was 9.18 (2.42) and 8.10 (2.46) years old in non-ADHD group. The 10-repeated allele of DAT1 was the highest proportion in both.

CONCLUSION

This finding was apparently similar with other studies on DAT1 polymorphism across Asian.

DNA Methylation at the DAT Promoter and Risk for Psychopathology: Intergenerational Transmission between School-Age Youths and Their Parents in a Community Sample

BACKGROUND

The effect of gene polymorphisms and promoter methylation, associated with maladaptive developmental outcomes, vary depending on environmental factors (e.g., parental psychopathology). Most studies have focused on 0- to 5-year-old children, adolescents, or adults, whereas there is dearth of research on school-age youths and pre-adolescents.

METHODS

In a sample of 21 families recruited at schools, we addressed parents' psychopathological symptoms (through SCL-90-R); offspring emotional-behavioral functioning (through CBCL-6-18); dopamine transporter gene (DAT1) for epigenetic status of the 5'-untranslated region (UTR) and for genotype, i.e., variable number of tandem repeats polymorphism at the 3'-UTR. Possible associations were explored between bio-genetic and psychological characteristics within the same individual and between triplets of children, mothers, and fathers.

RESULTS

DAT methylation of CpG at positions M1, M6, and M7 in mothers was correlated with maternal (phobic) anxiety, whereas in fathers' position M6 was related to paternal depression, anxiety, hostility, psychoticism, and higher Global Severity Index (GSI). No significant correlations were found between maternal and offspring DAT methylation. Significant correlations were found between fathers' methylation at CpG M1 and children's methylation at CpG M6. Linear regressions showed that mothers and fathers' GSI predicted children's methylation at CpG sites M2, M3, and M6, whereas fathers' GSI predicted children's methylation at CpG sites, particularly M1, M2, and M6. Moreover, offspring methylation of DAT at CpG M2 predicted somatic complaint, internalizing and attention problems; methylation of DAT at CpG M6 predicted withdraw.

CONCLUSION

This study may have important clinical implication for the prevention and treatment of emotional-behavioral difficulties in children, as it adds to previous knowledge about the role of genetic and environmental factors in predicting psychopathological symptoms within non-clinical populations.

Noncoding RNA Regulation of Dopamine Signaling in Diseases of the Central Nervous System

Dopaminergic neurotransmission mediates a majority of the vital central nervous system functions. Disruption of these synaptic events provokes a multitude of neurological pathologies, including Parkinson's, schizophrenia, depression, and addiction. Growing evidence supports a key role for noncoding RNA (ncRNA) regulation in the synapse. This review will discuss the role of both short and long ncRNAs in dopamine signaling, including bioinformatic examination of the pathways they target. Specifically, we focus on the contribution of ncRNAs to dopaminergic dysfunction in neurodegenerative as well as psychiatric disease.

Two SNAP-25 genetic variants in the binding site of multiple microRNAs and susceptibility of ADHD: A meta-analysis

The aim of this meta-analysis is to assess the associations between two most widely investigated polymorphisms (rs3746544 and rs1051312) in the 3'UTR of the SNAP-25 gene and susceptibility of ADHD. Two investigators selected related studies and assessed methodological quality independently. Six studies were included in this meta-analysis for a total of 715 cases and 655 controls. There is no apparent association between rs3746544 polymorphisms and risk of ADHD. However, subgroup analysis based on ethnicity demonstrated a strong association between rs3746544 polymorphism and ADHD in the subset of Asian participants, but not among Caucasians. Compared to the T allele, the allele G was associated with a significantly decreased risk of developing ADHD in the Asian population (odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.52-0.95, p = 0.02). The association between the TT genotype and ADHD risk was also significantly increased as compared to G/T (OR = 1.56, 95% CI = 1.00-2.44, p = 0.05) and the dominant genetic model (GG + GT vs. TT: OR = 1.51, 95% CI = 1.07-2.13, p = 0.02). For the rs1051312 SNP, being homozygous for the minor allele (C/C) was associated with a 3.66 higher odds of ADHD as compared to cases homozygous for the major allele (T/T) (95% CI = 1.64-8.13, p = 0.001), and 3.57 higher odds as compared to heterozygous (C/T) carriers (95% CI = 2.01-12.90, p < 0.001). Our results suggest that the polymorphisms rs3746544 and rs1051312 may increase the odds of developing ADHD. Additional studies are needed to confirm these findings.

miR-137 and miR-491 Negatively Regulate Dopamine Transporter Expression and Function in Neural Cells

The dopamine transporter (DAT) is involved in the regulation of extracellular dopamine levels. A 40-bp variable-number tandem repeat (VNTR) polymorphism in the 3'-untranslated region (3'UTR) of the DAT has been reported to be associated with various phenotypes that are involved in the aberrant regulation of dopaminergic neurotransmission. In the present study, we found that miR-137 and miR-491 caused a marked reduction of DAT expression, thereby influencing neuronal dopamine transport. Moreover, the regulation of miR-137 and miR-491 on this transport disappeared after the DAT was silenced. The miR-491 seed region that is located on the VNTR sequence in the 3'UTR of the DAT and the regulatory effect of miR-491 on the DAT depended on the VNTR copy-number. These data indicate that miR-137 and miR-491 regulate DAT expression and dopamine transport at the post-transcriptional level, suggesting that microRNA may be targeted for the treatment of diseases associated with DAT dysfunction.

Meta-Analysis Reveals Significant Association of the 3'-UTR VNTR in SLC6A3 with Alcohol Dependence

BACKGROUND

Although many studies have analyzed the association of 3'-untranslated region variable-number tandem repeat (VNTR) polymorphism in SLC6A3 with alcohol dependence (AD), the results remain controversial. This study aimed to determine whether this variant indeed has any genetic effect on AD by integrating 17 reported studies with 5,929 participants included.

METHODS

The A9-dominant genetic model that considers A9-repeat and non-A9 repeat as 2 genotypes and compared their frequencies in alcoholics with that in controls was adopted. Considering the potential influence of ethnicity, differences in diagnostic criteria of AD, and alcoholic subgroups, stratified meta-analyses were conducted. There existed no evidence for the presence of heterogeneity among the studied samples, indicating the results under the fixed-effects model are acceptable.

RESULTS

We found a significant association of VNTR A9 genotypes with AD in all ethnic populations (pooled odds ratio [OR] 1.12; 95% confidence interval [CI] 1.00, 1.25; p = 0.045) and the Caucasian population (pooled OR 1.15; 95% CI 1.01, 1.31; p = 0.036). We also found VNTR A9 genotypes to be significantly associated with alcoholism as defined by the DSM-IV criteria (pooled OR 1.18; 95% CI 1.03, 1.36; p = 0.02). Further, we found a significant association between VNTR A9 genotypes and alcoholism associated with alcohol withdrawal seizure or delirium tremens (pooled OR 1.55; 95% CI 1.24, 1.92; p = 1.0 × 10(-4) ). In all these meta-analyses, no evidence of publication bias was detected.

CONCLUSIONS

We concluded that the VNTR polymorphism has an important role in the etiology of AD, and individuals with at least 1 A9 allele are more likely to be dependent on alcohol than persons carrying the non-A9 allele.