Mill J, Asherson P, Craig I, D’Souza UM. Transient expression analysis of allelic variants of a VNTR in the dopamine transporter gene (DAT1). BMC Genet 6: 3

Institute of Psychiatry, MRC Social, Genetic, and Developmental Psychiatry (SGDP) Centre, De Crespigny Park, Denmark Hill, London, SE5 8AF, UK.
BMC Genetics (Impact Factor: 2.4). 02/2005; 6(1):3. DOI: 10.1186/1471-2156-6-3
Source: PubMed


The 10-repeat allele of a variable number tandem repeat (VNTR) polymorphism in the 3'-untranslated region of the dopamine transporter gene (DAT1) has been associated with a range of psychiatric phenotypes, most notably attention-deficit hyperactivity disorder. The mechanism for this association is not yet understood, although several lines of evidence implicate variation in gene expression. In this study we have characterised the genomic structure of the 9- and 10-repeat VNTR alleles, and directly examined the role of the polymorphism in mediating gene expression by measuring comparative in vitro cellular expression using a reporter-gene assay system.
Differences in the sequence of the 9- and 10- repeat alleles were confirmed but no polymorphic differences were observed between individuals. There was no difference in expression of reporter gene constructs containing the two alleles.
Our data suggests that this VNTR polymorphism may not have a direct effect on DAT1 expression and that the associations observed with psychiatric phenotypes may be mediated via linkage disequilibrium with other functional polymorphisms.

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    • "This VNTR polymorphism is known to be associated with neuropsychiatric disorders such as attention-deficit hyperactivity disorder (ADHD), Parkinson's disease (PD), alcoholism, and drug abuse (Cook et al., 1995; Ueno et al., 1999; Vandenbergh et al., 2000; Ueno, 2003; D'Souza and Craig, 2008). It is involved in modified gene expression both in vivo (Heinz et al., 2000; Jacobsen et al., 2000; Mill et al., 2002; D'Souza and Craig, 2008) and in mammalian cell lines (Fuke et al., 2001, 2005; Inoue-Murayama et al., 2002; Miller and Madras, 2002; Greenwood and Kelsoe, 2003; Mill et al., 2005; VanNess et al., 2005; D'Souza and Craig, 2008). Thus, the relationship between HESRs and the dopaminergic system seems worthy of discussion. "
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    ABSTRACT: Transcription factor Hesr family genes are important in neuronal development. We demonstrated previously that HESR1 and HESR2 modified expression of the dopamine transporter (DAT) reporter gene. HESR-family genes have been investigated in development, but their functions, especially in relation to behaviors regulated by dopamine, in adult animals remain unclear. In the present study, we investigated the effects of Hesr1 and Hesr2 on behavior. A behavioral test battery to examine spontaneous activity, anxiety-like behavior, aggressive behavior, pain sensitivity, and sensorimotor gating was conducted in Hesr1 and Hesr2 knockout (KO) mice. Enhanced prepulse inhibition (PPI), which is a form of sensorimotor gating, was observed in only Hesr1 KO mice; other behavioral traits were mostly comparable to wild-type animals in both the Hesr1 and the Hesr2 KO lines. Next, we used a dopamine agonist, apomorphine, to confirm the involvement of the dopaminergic system. Injection of apomorphine reduced the enhanced PPI in Hesr1 KO mice. Additionally, dose-dependent sensitivity to the agonist was lower in the Hesr1 KO mice than in wild-type mice, suggesting that the enhanced PPI resulted from this alteration in dopamine sensitivity. Furthermore, DAT mRNA was downregulated in Hesr1 KO mice, whereas the dopamine D1 and D2 receptors were comparable. These findings suggest Hesr1 to be a novel factor that affects dopamine sensitivity and the sensorimotor gating system. © 2013 Wiley Periodicals, Inc.
    Full-text · Article · Mar 2014 · Journal of Neuroscience Research
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    • "Unfortunately the functional studies of this polymorphism have shown less concord than the others discussed here. Over the years there have been numerous studies that have tested the functional effects of the VNTR polymorphism in the 3′UTR of the DAT1 gene using reporter gene assays and transient transfection in mammalian cell cultures [39] [40] [81] [84] [85] [121]. "
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    ABSTRACT: In the last few years', research has focused on Single Nucleotide Polymorphisms (SNPs) in the search for underlying genetic aetiology of complex disorders. This has been afforded by the rapid technological advancement to enable the interrogation of hundreds of thousands of SNPs in one assay via microarrays. However SNPs are only one form of genetic variation and in the midst of the Genome-Wide Association Study (GWAS) explosion Variable Number Tandem Repeat (VNTR) polymorphism exploration has seemingly been left behind. This review will argue that VNTR investigations still hold substantial potential for a role in complex disorders via possible functional properties.
    Full-text · Article · Mar 2013 · Genomics
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    • "Accumulating evidence indicates that a 40-base-pair variable number of tandem repeats polymorphism (DAT1) in the 3' untranslated region of the DAT gene (DAT1) influences the expression and availability of DAT (Bannon et al., 2001). Although investigators have not consistently observed a genotype effect across all studies (Martinez et al., 2001; Michelhaugh et al., 2001; Mill et al., 2005; van Dyck et al., 2005), several suggest that in comparison to the 9-repeat allele, the 10-repeat is associated with relatively increased levels of DAT both in vivo (Cheon et al., 2005; Heinz et al., 2000) and in vitro (Mill et al., 2002; VanNess et al., 2005). We hypothesized that there would be relatively greater VS reactivity associated with the 9-repeat allele, which is linked with reduced DAT expression and presumably greater striatal synaptic dopamine, in comparison with the 10- repeat allele. "
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    ABSTRACT: Addictive disorders are heritable, but the search for candidate functional polymorphisms playing an etiological role in addiction is hindered by complexity of the phenotype and the variety of factors interacting to impact behavior. Advances in human genome sequencing and neuroimaging technology provide an unprecedented opportunity to explore the impact of functional genetic variants on variability in behaviorally relevant neural circuitry. Here, we present a model for merging these technologies to trace the links between genes, brain, and addictive behavior. We describe imaging genetics and discuss the utility of its application to addiction. We then review data pertaining to impulsivity and reward circuitry as an example of how genetic variation may lead to variation in behavioral phenotype. Finally, we present preliminary data relating the neural basis of reward processing to individual differences in nicotine dependence. Complex human behaviors such as addiction can be traced to their basic genetic building blocks by identifying intermediate behavioral phenotypes, associated neural circuitry, and underlying molecular signaling pathways. Impulsivity has been linked with variation in reward-related activation in the ventral striatum (VS), altered dopamine signaling, and functional polymorphisms of DRD2 and DAT1 genes. In smokers, changes in reward-related VS activation induced by smoking abstinence may be associated with severity of nicotine dependence. Variation in genes related to dopamine signaling may contribute to heterogeneity in VS sensitivity to reward and, ultimately, to addiction. These findings illustrate the utility of the imaging genetics approach for investigating the neurobiological basis for vulnerability to addiction.
    Full-text · Article · Feb 2012 · Drug and alcohol dependence
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