ADHDgene Database

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Large-scale studies

Data Summary

Published Variant
- SNP: 1391
- CNV: 398
- Others: 173
Published Gene: 359
Published Region: 128
Pathway by PBA: 8
Study: 361

Study Report

Basic Info

Reference	Kim JW, 200616368111
Citation	Kim J. W., Kim B. N. and Cho S. C. (2006) "The dopamine transporter gene and the impulsivity phenotype in attention deficit hyperactivity disorder: a case-control association study in a Korean sample." J Psychiatr Res, 40(8): 730-7.
Study Design	case-control and family-based
Study Type	Candidate-gene association study
Sample Size	family-based sample: 85 children and their parents; case-control sample: 100 healthy individuals
Predominant Ethnicity	Mongoloid
Population	Korea
Gender	family-based sample: 71 boys and 14 girls; case-control sample: 85 men and 15 women
Age Group	Children/Adolescents and Adults : family-based sample: mean age 9.7, SD=2.1; case-control sample: mean age 42.2, SD=7.3

Detail Info

Summary	The aim of this study was to examine the relationship between the DAT1 genotypes and the candidate endophenotypes, inattention and impulsivity symptoms, as measured by the continuous performance test (CPT), in a Korean sample of 85 children diagnosed with DSM-IV ADHD. Compared to the normal control group, the frequencies of the 9/10 genotype were significantly higher in the ADHD probands and parents of probands. The 9-repeat allele frequencies were significantly higher in the ADHD probands and parents of probands than the normal control group. Compared to the ADHD probands without the 9-repeat allele, the mean T-score, with regard to the commission errors of the CPT, was significantly higher in the ADHD probands with the 9-repeat allele. Compared to the ADHD probands with other DAT1 genotypes, the mean T-score, with respect to the commission errors of the CPT, was significantly higher in the ADHD probands with the 9/10 genotype. The results of this study suggest the possibility of an association between the DAT1 9- repeat allele and the impulsivity phenotype of ADHD.
Total Sample	The present study included 85 children with ADHD (mean 9.7,SD=2.1 years), consisting of 71 boys and 14 girls, aged 8-12 years, and their parents, who visited the Department of Child and Adolescent Psychiatry of Seoul National University Hospital in Korea. In addition to a family-based design, we also included a control group to allow for a case-control design. The control group included 100 healthy individuals (mean 42.2,SD=7.3 years), consisting of 85 men and 15 women, who visited the Health Promotion Center of Seoul National University Hospital.
Sample Collection	Korean
Diagnosis Description	K-SADS-PL was the tool used for the diagnosis of ADHD in the present study. It is a semi-structured interview tool, designed to evaluate the severities of ADHD symptoms and evaluate the current state and affected state throughout the lifetime of the child, for the 32 different psychiatric disorders included in DSM-IV using objective diagnostic criteria. Composed of a total of 18 items, the ADHD Rating Scale (ARS) was designed by DuPaul (1991) to evaluate the severity of the symptoms of ADHD according to the DSM-IV diagnostic criteria, using a 4-point rating scale ranging from 0 to 3.
Technique	Genomic DNA was extracted from blood lymphocytes using a Genomic DNA Extraction kit (Bioneer, Korea). The 40-base pair (40-bp) VNTR polymorphism located in the 3'-UTR of DAT1 was genotyped, as previously described, but with slight modification (Vandenbergh et al., 1992). T7-5 Long (5'-TGT GGT GTA GGG AAC GGC CTG AG-3') and T7-3a Long (5'-CTT CCT GGA GGT CAC GGC TCA AGG-3') were used at concentrations of 5x10-7 M. The PCR was performed under universal conditions, in a volume of 20ul containing 10 x PCR buffer 1.5 mM MgCl2, 0.25 mM of each dNTP, 1.25 U AmpliTaq gold, primers and 40 ng of genomic DNA. The reaction consisted of denaturation at 94^oC for 4 min, followed by 35 cycles of 94^oC for 40 s, 72^oC for 40 s and 72^oC for 1 min, with a final extension at 72^oC for 10 min. Thermal cycling was performed on the PTC-100 Peltier Thermal cycler and the reaction products separated by 2% LE gel electrophoresis.
Analysis Method	The allele frequencies were estimated by counting, and the Hardy-Weinberg equilibrium was calculated based on these allele frequencies, using the goodness-of- fit X² (Chi-square) test. The estimation of allele frequencies and the test for the Hardy-Weinberg equilibrium were conducted for the genotypes of all subjects. Family-based association of the DAT1 VNTR polymorphism with ADHD was investigated using the transmission disequilibrium test (TDT) (Spielman et al., 1993). Group differences in the clinical variables involving continuous data were computed using an independent two sample t-test or one-way analysis of variance (ANOVA). Between-group comparisons involving categorical data were assessed using the X² (Chi-square) test or Fisher's exact test.
Result Description	Compared to the normal control group, the frequencies of the 9/10 genotype were significantly higher in the ADHD probands (X²=13.45, P-value=0.02, OR=4.12, 95% CI: 2.21-12.34) and parents of probands (X²=11.60, P-value=0.03). The 9-repeat allele frequencies were significantly higher in the ADHD probands (X²=11.55, P-value=0.03, OR=4.43, 95% CI: 1.55-11.78) and parents of probands (X²=12.70,P-value=0.03) than the normal control group. Compared to the ADHD probands without the 9-repeat allele (n=74), the mean T-score, with regard to the commission errors of the CPT, was significantly higher (P-value<0.05) in the ADHD probands with the 9-repeat allele (n=11). Compared to the ADHD probands with other DAT1 genotypes, the mean T-score, with respect to the commission errors of the CPT, was significantly higher in the ADHD probands with the 9/10 genotype (P-value<0.05).

Other variant reported by this study (count: 1)

Genes reported by this study (count: 1)