title: Transmission disequilibrium testing of dopamine-related candidate gene polymorphisms in ADHD: confirmation of association of ADHD with DRD4 and DRD5.
abstract: Attention-deficit hyperactivity disorder (ADHD) is one of the most common childhood behavioral disorders. Genetic factors contribute to the underlying liability to develop ADHD. Reports implicate variants of genes important for the synthesis, uptake, transport and receptor binding of dopamine in the etiology of ADHD, including DRD4, DAT1, DRD2, and DRD5. In the present study, we genotyped a large multiplex sample of ADHD affected children and their parents for polymorphisms in genes previously reported to be associated with ADHD. Associations were tested by the transmission disequilibrium test (TDT). The sample is sufficient to detect genotype relative risks (GRRs) for putative risk alleles. The DRD4 gene 120-bp insertion/deletion promoter polymorphism displayed a significant bias in transmission of the insertion (chi(2)=7.58, P=0.006) as suggested by an analysis of a subset of these families. The seven repeat allele of the DRD4 48-bp repeat polymorphism (DRD4.7) was not significantly associated with ADHD in the large sample in contrast to our earlier findings in a smaller subset. We replicate an association of a dinucleotide repeat polymorphism near the DRD5 gene with ADHD by showing biased nontransmission of the 146-bp allele (P=0.02) and a trend toward excess transmission of the 148-bp allele (P=0.053). No evidence for an association was found for polymorphisms in DRD2 or DAT1 in this sample. The DRD5 146-bp (DRD5.146) allele and the DRD4 240-bp (DRD4.240) allele of the promoter polymorphism emerge as the two DNA variants showing a significant association in this large sample of predominantly multiplex families with ADHD, with estimated GRRs of 1.7 and 1.37, respectively.
authors.affiliation: Department of Human Genetics, Division of Child and Adolescent Psychiatry, UCLA School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: V
authors.initials: V
authors.lastname: Kustanovich
authors.forename: J
authors.initials: J
authors.lastname: Ishii
authors.forename: L
authors.initials: L
authors.lastname: Crawford
authors.forename: M
authors.initials: M
authors.lastname: Yang
authors.forename: J J
authors.initials: JJ
authors.lastname: McGough
authors.forename: J T
authors.initials: JT
authors.lastname: McCracken
authors.forename: S L
authors.initials: SL
authors.lastname: Smalley
authors.forename: S F
authors.initials: SF
authors.lastname: Nelson
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics*; D002648:Child; D050483:Dopamine Plasma Membrane Transport Proteins; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics; D011110:Polymorphism, Genetic; D017447:Receptors, Dopamine D1 / Q000235:genetics*; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D050638:Receptors, Dopamine D4; D050641:Receptors, Dopamine D5; D012307:Risk Factors
chemical_list: C493599:DRD4 protein, human; C493605:DRD5 protein, human; D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C493214:SLC6A3 protein, human; D050638:Receptors, Dopamine D4; D050641:Receptors, Dopamine D5