title: Role of functional dopaminergic gene polymorphisms in the etiology of idiopathic intellectual disability.
abstract: Intellectual disability (ID) is of major concern throughout the world, though in ~40% of cases etiology remains unknown (idiopathic ID or IID). Cognitive impairment and behavioral problems are of common occurrence in these subjects and dopamine is known to play an important role in regulating these traits. In the present study the role of functional polymorphisms in three dopaminergic genes, dopamine receptor D4 (DRD4: exon3 VNTR and rs1800955), dopamine transporter (DAT1: 3'UTR VNTR and intron8 VNTR) and catechol-O-methyl transferase (COMT: rs4680 and rs165599), was explored in IID. Probands (n=225), parents (n=298) and ethnically matched controls (n=175) were recruited following DSM-IV. Genotype data obtained was used for population- and family-based statistical analyses. Population-based analysis showed significant association of DRD4 exon3 VNTR 6R allele (P=0.01), DAT1 3'UTR VNTR lower repeat (6R and 7R) alleles (P<0.02) and intron8 VNTR 5R allele (P=0.0012) with IID. Stratified analysis revealed significant association of these alleles (P<0.05) with IID individuals exhibiting severe behavioral problems. On the other hand, preferential transmission of COMT rs4680 A allele and A-A haplotype (P<0.05) was observed specifically in male IID probands without any behavioral problem. Markers failed to show any significant epistatic interaction by MDR analysis. Alleles showing positive association were all reported to confer suboptimal activity to the transcribed proteins. Therefore, an alteration in dopaminergic neurotransmission could be predicted that may lead to impairments in cognition and behavioral problems.
authors: Manovikas Biomedical Research and Diagnostic Centre, Kolkata-700107, India.
authors: Aneek Das
authors: AD
authors: Bhowmik
authors: Subhramay
authors: S
authors: Chaudhury
authors: Samikshan
authors: S
authors: Dutta
authors: Jyoti
authors: J
authors: Shaw
authors: Arpita
authors: A
authors: Chatterjee
authors: Arnab
authors: A
authors: Choudhury
authors: Amrita
authors: A
authors: Saha
authors: Dipanjana
authors: D
authors: Sadhukhan
authors: Turban
authors: T
authors: Kar
authors: Swagata
authors: S
authors: Sinha
authors: Kanchan
authors: K
authors: Mukhopadhyay