Evidence for linkage of a tandem duplication polymorphism upstream of the dopamine D4 receptor gene (DRD4) with attention deficit hyperactivity disorder (ADHD)
Jt. Mccracken et al., Evidence for linkage of a tandem duplication polymorphism upstream of the dopamine D4 receptor gene (DRD4) with attention deficit hyperactivity disorder (ADHD), MOL PSYCHI, 5(5), 2000, pp. 531-536
Attention deficit hyperactivity disorder (ADHD) is a common childhood-onset
neurodevelopmental disorder. Evidence from twin, adoption, and family stud
ies provide support for a genetic contribution to the etiology of ADHD, Sev
eral candidate gene studies have identified an association between a 7-repe
at variant in exon 3 of the dopamine 4 receptor gene (DRD4) and ADHD. Howev
er, in spite of the positive reports finding association of the exon 3 VNTR
with ADHD, several other polymorphisms within DRD4 have been identified th
at conceivably could contribute to risk for ADHD, Recently, another common
polymorphism of the DRD4 gene has been described involving a 120-bp repeat
element upstream of the 5' transcription initiation site. In this report, w
e describe results of analysis of the DRD4 120-bp repeat promoter polymorph
ism in a sample of 371 children with ADHD and their parents, using the tran
smission disequilibrium test (TDT). Results showed a significant preferenti
al transmission of the 240-bp (long) allele with ADHD, Exploratory analyses
of the Inattentive phenotypic subtype of ADHD strengthened the evidence fo
r linkage. These data add further support for the role of DRD4 variants con
ferring increased risk for ADHD, and imply that additional studies of DRD4
and other related genes are needed.