ABSTRACT:
The present study aims to evaluate the possible association of PPP3R1 gene polymorphism (CnB 5I/5D) in clinical presentation of mental retardation (MR). A total of 100 children with idiopathic mental retardation in the age group of 5-16 years from both the sexes were recruited in the study considering age and sex matched healthy controls. Both cases and controls were genotyped by Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) method for a single nucleotide polymorphism in PPP3R1 gene. The psychometric analysis of 100 MR children indicated that 3% of the children had borderline degree of retardation in which 42% of them were mild, 25% of them were moderate, 30% of them had severe degree of retardation. All the subjects included in the study were categorized based on their clinical and dysmorphic features. Among them 54% had behavioural disorders, 9% had cerebral palsy, 8% had microcephaly, 18% had convulsions and 11% had epilepsy. A significant association was observed for genetic variation at PPP3R1 (CnB 5I/5D) and MR [p < 0.04]. The results revealed that PPP3R1 (CnB 5I/5D) gene polymorphism is associated with MR. Insilico analysis of gene polymorphism i.e., CnB 5I/5D showed absence of TBP binding and may be responsible for low levels of calcineurin. Since calcineurin is involved in biosynthesis and release of neurotransmitter, the low levels of calcineurin and the associated gene polymorphism may be involved in causation of mental retardation.