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Polymorphisms in the dopamine D4 receptor gene and attention-deficit hyperactivity disorder
Jonathan Mill1, Naomi Fisher, Sarah Curran
1Social, Genetic, and Developmental Psychiatry Research Centre, Institute of Psychiatry, PO82, De Crespigny Park, Denmark Hill, London SE5 8AF, UK. spjgjsm@iop.kcl.ac.uk
Neuroreport
|September 10, 2003
Summary
Dopamine D4 receptor gene variations were studied in attention-deficit hyperactivity disorder (ADHD). While individual markers showed no association, a specific promoter region haplotype may increase ADHD susceptibility.
Area of Science:
- Neurogenetics
- Psychiatric Genetics
Background:
- Dopamine-related genes are implicated in the molecular basis of attention-deficit hyperactivity disorder (ADHD).
- A 48 bp repeat polymorphism in the dopamine D4 receptor (DRD4) gene's exon 3 is frequently studied and meta-analyses suggest an association with ADHD.
- Other DRD4 gene polymorphisms require further investigation for their role in ADHD.
Purpose of the Study:
- To investigate the association of five DRD4 gene polymorphisms with ADHD in a large clinical sample and their families.
- To identify specific genetic markers or combinations of markers conferring susceptibility to ADHD.
Main Methods:
- Genotyping of five DRD4 gene polymorphisms: a 120 bp promoter-region duplication, -616 C/G, -521 C/T, intron 1 poly-G repeat, and exon 3 48 bp repeat.
- Analysis in a clinical sample of 188 individuals with ADHD and their families.
Main Results:
- No single polymorphism was individually associated with ADHD.
- Evidence suggests a specific haplotype in the 5' promoter region (DRD4 exon 3 48 bp repeat, promoter duplication allele 2, -616 C allele, and -521 C allele) may be associated with ADHD susceptibility.
Conclusions:
- Individual DRD4 polymorphisms are not strongly associated with ADHD in this sample.
- A combination of promoter region variants (haplotype) may play a role in ADHD susceptibility, warranting further research.