[Transmission disequilibrium test of DRD4 exon III 48bp variant number tandem repeat polymorphism and tic disorder].
OBJECTIVE
To investigate whether DRD4 exon III48 bp variant number tandem repeat(VNTR) polymorphism is associated with tic disorder.


METHODS
One hundred and twenty-two nucleus families were collected using   Structured clinical interview for genetic study of Tourette syndrome and related disorders   for family-based association analysis of tic disorder and DRD4 exon III 48bp VNTR polymorphism. One hundred and twenty-two trios were divided into two groups: tic disorder group (82 trios of Tourette syndrome or chronic tic disorder, TS&CT) and tic disorder accompanied with attention deficit and hyperactivity disorder (ADHD) group (40 trios of Tourette syndrome or chronic tic disorder accompanied with ADHD, TS&ADHD). Transmission disequilibrium test (TDT), in addition to polymerase chain reaction and VNTR technique were conducted in 122 trios.


RESULTS
There exist 5 alleles at this polymorphic locus in this sample including DRD4 exon III 48bp 2-6 repeats. No transmission disequilibrium was found between DRD4 exon III 48 bp VNTR and tic disorder (chi square=7.44, P  0.12); however, when the sample was divided into two groups, transmission disequilibrium was noticed between the cases of TS&ADHD and this locus by overall allele-wise analysis (chi square=11.74, P  0.02), and there exists transmission disequilibrium exclusively between 5 or 6 repeats of 48bp VNTR(longer alleles) by allele-wise analysis (chi square=10.57, P  0.032, chi square=6.13, P  0.01). No transmission disequilibrium was seen between TS&CT and DRD4 exon III 48bp VNTR(chi square=3.38, P  0.50).


CONCLUSIONS
The results of this study have revealed an association between the longer alleles of DRD4 exon III 48bp VNTR polymorphism and tic disorder accompanied with ADHD, thus suggesting a possible genetic risk factor of tic disorder accompanied with ADHD in Chinese.
Huang
Yi
Y
Institute of Mental Health, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041 P. R. China. cdwangyun@mail.sc.cninfo.net
Liu
Xiehe
X
Li
Tao
T
Guo
Lanting
L
Ma
Xiaohong
X
Yuan
Guanggu
G
Peng
Rong
R
D000293:Adolescent; D000328:Adult; D000483:Alleles; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000235:genetics; D005091:Exons / Q000235:genetics*; D005192:Family Health; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D018598:Minisatellite Repeats / Q000235:genetics*; D011110:Polymorphism, Genetic; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D050638:Receptors, Dopamine D4; D013981:Tic Disorders / Q000150:complications / Q000235:genetics*
C493599:DRD4 protein, human; D017448:Receptors, Dopamine D2; D050638:Receptors, Dopamine D4; D004247:DNA