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Zhou, K., Chen, W., Buitelaar,
J. K., Banaschewski, T., Oades, R. D., Franke, B., Sonuga-Barke, E.
J. S., Ebstein, R. P., Eisenberg, J., Gill, M., Manor, I., Miranda,
A., Mulas, F., Roeyers, H., Rothenberger, A., Sergeant, J. A., Steinhausen,
H-C., Lasky-Su, J., Taylor, E. A., Brookes, K-J., Xu, X., Neale, B.
M., Rijsdijk, F., Thompson, M. J., Asherson, P., & Faraone, S. V.
Genetic heterogeneity in ADHD: DAT1 gene only affects probands
without CD. (2008) Am J Med Genet Part B. 147B,
1481-1487.DOI: 10.1002/ajmg.b.30644. (request
a copy) View
Article
Introduction: Associations between ADHD &
10-repeat allele of a VNTR in the 3'-untranslated region of the DA transporter
gene (DAT1) are remarkably variable. A possible-reason for heterogeneous
findings is comorbidity of conduct disorder (CD) -- this might indicate
a distinct genetic form of ADHD (Christiansen
et al., 2008)
Methods:
HERE selected 576 DSM-IV combined type ADHD trios (141 with comorbid
CD) from the IMAGE study to test whether DAT1 has a different effect
size in the co-morbid group.
Results:
1) Our heterogeneity test result
suggests that DAT1 has a significantly greater genetic influence on
ADHD children without CD compared to the comorbid group.
2) The 2 significant SNPs (rs40184,
rs2652511) from association tests in the ADHD-CD group also show significant
genetic heterogeneity (p=0.016 & p=0.023). In addition, rs27072
shows significant heterogeneity (p=0.034), but has only a marginal association
with ADHD-CD group (p=0.06) and no association with the ADHD+CD group
(p=0.168).
3) Further work is needed to replicate
this finding.
4) The ADHD genetic heterogeneity
identified in this study can partially explain the heterogeneous association
findings in previous DAT1 studies and it also emphasizes the importance
of selecting genetically homogeneous samples for molecular genetic analysis
of ADHD: see
also Christiansen et al., 2008.
Support: NIH.
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