Attention-deficit hyperactivity disorder: a study of association with both the dopamine transporter gene and the dopamine D4 receptor gene.
Attention-deficit hyperactivity disorder (ADHD) is one of the most common psychiatric disorders of childhood. The role of genetic factors in its etiology is strongly supported by family, adoption, and twin studies. Several investigations have reported associations between ADHD and both the 7-repeat allele of the 48 bp VNTR at the DRD4 gene and the 10-repeat allele of the 40 bp VNTR at the DAT1 gene, but the results have been inconsistent. A sample of 81 Brazilian ADHD children and adolescents and their parents were screened for these DRD4 and DAT1 VNTRs. An excess of the DRD4 7-repeat allele was observed when both ADHD probands and their parents were compared with an ethnically matched control sample (chi-square = 11.55, P = 0.03; chi-square = 12.17, P = 0.03, respectively). However, haplotype relative risk (HRR) analysis showed no preferential transmission of the DRD4 7-repeat allele. No evidence of association with the DAT1 polymorphism was detected by both approaches. Nevertheless, an interaction effect of both genes on ADHD hyperactive/impulsive dimension was observed (F = 4.68; P = 0.03). These results add to the group of studies that together suggest a small effect of these genes in the susceptibility to ADHD.
Roman
T
T
Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. tatiana.roman@ufrgs.br
Schmitz
M
M
Polanczyk
G
G
Eizirik
M
M
Rohde
L A
LA
Hutz
M H
MH
D000293:Adolescent; D000483:Alleles; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics* / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics; D002648:Child; D004247:DNA / Q000235:genetics; D050483:Dopamine Plasma Membrane Transport Proteins; D005192:Family Health; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D017448:Receptors, Dopamine D2 / Q000235:genetics; D050638:Receptors, Dopamine D4
D002352:Carrier Proteins; C493599:DRD4 protein, human; D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D017448:Receptors, Dopamine D2; C493214:SLC6A3 protein, human; D050638:Receptors, Dopamine D4; D004247:DNA