[Genome-wide search for linkage to attention deficit hyperactivity disorder (ADHD) on the X chromosome]

Attention deficit hyperactivity disorder (ADHD) is the most common childhood-onset behavioral. Boys are more often affected than girls. Family, twin and adoption studies have supported a strong genetic basis. The etiology of this disorder is not clear. Molecular genetic and pharmacological studies suggest the involvement of dopaminergic and noradrenergic neurotransmitter systems in ADHD, e.g , Several reports have found association between ADHD and the dopamine receptor gene DRD-4.the dopamine transporter gene DAT1, and the catechol-o-methyltransferase. Our previous studies showed an association between ADHD and the DXS7 locus, which is located in closely linked to the MAO gene, and MAOA gene on chromosome X. To test this hypothesis, we used the genome scan for a predisposing locus on chromosome X to ADHD. We used the tramsmission/disequilibrium test (TDT) to test for linkage between a VNTR polymorphism at the 48 markers of chromosome X and DSM-III-R oliagnosed ADHD in 84 nuclear families of the Chinese population. The TDT analysis revealed linkage between ADHD and the DXS1214(TDT: Chi2=18.1, df=7, P<0.01), DXS8102(TDT: Chi2=7.9, df=3, P<0.05), DXS1068(TDT: Chi2=21.9, df=9, P<0.01), DXS8015(TDT: Chi2=14.6, df=7, P<0.05), DXS1059(TDT: Chi2=27.8, df=10, P<0.01) and DXS8088(TDT: Chi2=20.4, df=3, P<0.01).The data showed that susceptibility loci might reside in chromosome Xp11.4-Xp21 and Xq23 for ADHD.