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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	Carrasco X, 200616342279
Citation	Carrasco X., Rothhammer P., Moraga M., Henriquez H., Chakraborty R., Aboitiz F. and Rothhammer F. (2006) "Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families." Am J Med Genet B Neuropsychiatr Genet, 141B(1): 51-4.
Study Design	family-based
Study Type	Candidate-gene association study
Sample Size	26 affected children and 25 unaffected siblings
Predominant Ethnicity	Chilian
Population	Chile
Gender	24 male subjects and 2 female subjects
Age Group	Children/Adolescents : 9-14 years

Detail Info

Summary	As part of an ongoing study of ADHD, they carried out a family-based discordant sib-pair analysis to detect possible associations between dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms and ADHD in Chilean families. Both loci individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DAT1 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings. However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25). Increased density of dopamine transporter in ADHD brains, along with abundance of 7-repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene-gene interaction worthy of further incisive studies.
Total Sample	As part of an ongoing study on genetic, electrophysiological, imageological, and cognitive aspects of ADHD, they consecutively approached the parents of 51 children from Chilean ADHD families in the greater Santiago area through hospitals and clinics. They compared the 26 affected children with their healthy sibs.
Diagnosis Description	Twenty-six subjects from 9 to 14 years of age, were diagnosed as ADHD combined subtype, according to DSM-IV criteria of the USAn Psychiatric Association, 1994, by a specialized pediatric neurologist (XC). The social and familial behavior of parents and healthy sibs were assessed through interviews conducted by a clinical psycologist (PR). All patients were applied the Wechsler Intelligence Scale Revised Edition WISC-R for children in order to evaluate their IQ's and to obtain a qualitative appraisal of their behavior.
Technique	Genomic DNA was isolated from lymphocytes and amplified by PCR to identify the VNTR's of the DRD4 and DAT1 loci using the protocol described by Nanko et al. [1993].
Analysis Method	The pooling algorithms of genotypes resulted in 2x2 contingency table contrast of genotype frequencies between cases and controls. The significance of genotype frequencies was tested for each of the contrasts (each locus considered individually, and both loci considered together) by Fisher's exact tests. When significant frequency difference was found (as in the two-locus analysis), odds ratio (OR) and its 95% confidence interval were estimated by the traditional method as described in Woolf [1955] and Haldane [1956].
Result Description	Both loci individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DAT1 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings (Fisher's exact test P-value>0.25 in both cases). However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25) (4%; Fisher's exact test P-value=0.0096; odds-ratio, OR=12.71).

Other variant reported by this study (count: 2)

Variant Name	Allele Change	Risk Allele	Statistical Values	Author Comments	Result of Statistical Analysis
SLC6A3 3'-UTR VNTR			Fisher's exact test P-value=0.2673 Fisher's exact test P-value=0.2673	not significantly different from unaffected siblings	Non-significant
DRD4 exon3 VNTR			Fisher¡¯s exact test P-value=0.5621 Fisher¡¯s exact test P-value=0.5621	not significantly different from unaffected siblings	Non-significant

Genes reported by this study (count: 2)

Gene	Statistical Values/Author Comments	Result of Statistical Analysis
SLC6A3	SLC6A3 10-repeat alleles Fisher¡¯s exact test P-value>0.25, ...... SLC6A3 10-repeat alleles Fisher¡¯s exact test P-value>0.25, DRD4 7-repeat heterozygosity and SLC6A3 10 allele homozygosity Fisher¡¯s exact test P-value=0.0096; OR=12.71, suggested evidence of gene-gene interaction effects on the prevalence of ADHD in the Chilean population More...	Significant
DRD4	DRD4 7-repeat alleles Fisher¡¯s exact test P-value>0.25, DRD...... DRD4 7-repeat alleles Fisher¡¯s exact test P-value>0.25, DRD4 7-repeat heterozygosity and SLC6A3 10 allele homozygosity Fisher¡¯s exact test P-value=0.0096; OR=12.71, suggested evidence of gene-gene interaction effects on the prevalence of ADHD in the Chilean population More...	Significant