Transient expression analysis of allelic variants of a VNTR in the dopamine transporter gene (DAT1).
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Mill
Jonathan
J
Institute of Psychiatry, MRC Social, Genetic, and Developmental Psychiatry (SGDP) Centre, De Crespigny Park, Denmark Hill, London, SE5 8AF, UK. j.mill@iop.kcl.ac.uk
Asherson
Philip
P
Craig
Ian
I
D'Souza
Ursula M
UM
D000483:Alleles; D002460:Cell Line; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics*; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D015810:Linkage Disequilibrium; D008156:Luciferases / Q000235:genetics; D001523:Mental Disorders / Q000209:etiology / Q000235:genetics; D018598:Minisatellite Repeats; D011110:Polymorphism, Genetic; D014162:Transfection
D050483:Dopamine Plasma Membrane Transport Proteins; D008156:Luciferases