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Genetic heterogeneity in ADHD: DAT1 gene only affects probands without CD
Kaixin Zhou1, Wai Chen, Jan Buitelaar
1MRC Social Genetic Developmental and Psychiatry Centre, Institute of Psychiatry, London, United Kingdom.
Summary
Genetic analysis of the DAT1 gene in attention deficit hyperactivity disorder (ADHD) reveals significant differences based on conduct disorder (CD) comorbidity. The DAT1 gene shows a greater genetic influence on ADHD without CD, highlighting the need for genetically homogeneous samples.
Area of Science:
- Neurogenetics
- Psychiatric Genetics
- Molecular Psychiatry
Background:
- The association between the DAT1 gene's 3'-UTR-VNTR polymorphism and attention deficit hyperactivity disorder (ADHD) has been inconsistent across studies.
- Conduct disorder (CD) comorbidity may contribute to this heterogeneity, as ADHD with CD (ADHD + CD) appears genetically distinct from ADHD without CD (ADHD - CD).
Purpose of the Study:
- To investigate the role of DAT1 genetic variants in ADHD, specifically examining potential differences in genetic influence between ADHD + CD and ADHD - CD subgroups.
- To identify specific DAT1 markers that show differential transmission patterns in relation to CD comorbidity.
Main Methods:
- Genotyping of 20 DAT1 markers was performed in 576 trios (141 ADHD + CD, 435 ADHD - CD).
- Transmission Disequilibrium Test (TDT) and a genetic heterogeneity test were employed to analyze allele transmission patterns.
- Statistical corrections for multiple testing were applied to identify significant associations.
Main Results:
- Two single nucleotide polymorphisms (SNPs), rs40184 and rs2652511, were found to be significant in TDT analyses after multiple-test correction.
- The genetic heterogeneity test revealed significant differences in transmission patterns for rs40184 and rs2652511 between the ADHD + CD and ADHD - CD groups.
- These findings suggest that the DAT1 gene exerts a greater genetic influence on ADHD in the absence of CD.
Conclusions:
- The DAT1 gene's genetic impact on ADHD is modulated by the presence or absence of conduct disorder comorbidity.
- Molecular genetic studies of ADHD should consider sample homogeneity, particularly regarding CD comorbidity, to resolve discrepancies in findings.
- Further replication studies are warranted to confirm the role of specific DAT1 variants in distinct ADHD phenotypes.
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