Molecular evaluation of Ex3 VNTR polymorphism of the DRD4 gene in patients with autism spectrum disorder

Autism Spectrum Disorders (ASDs) are a group of neurodevelopmental disorders that affect social and communication skills. These diseases are characterized by severe communication and social skills disabilities and limited and repetitive activities. The prevalence of these disorders appears to be steadily increasing. It is proposed that the genes involved in the dopamine pathway may play an essential role in the development of autism. In this study, we investigated the possible association between Ex3 VNTR polymorphism of the DRD4 gene and autism spectrum disorders in the Iranian population.

Materials & Methods:

In this case-control study, 97 children with autism and 103 healthy individuals from a northwestern area of Iran as the case and control groups, respectively. After genomic xtraction from peripheral blood samples by the proteinase K method, the polymerase chain reaction (PCR) technique was used to determine the polymorphism genotypes. The data were then coded and analyzed using SPSS version 22 software.

The study results showed that the allele frequencies differed in the two groups, some of them being statistically significant. The most common allele in both the ASD and the control group was the 700 bp allele, and its frequency was significantly different in the two groups and was more common in the ASD group (p-value=0.0018). The other allele with a statistically different frequency was the 800 bp allele which was less frequent in the ASD group (p-value=0.0017)

These results suggest a potential association between Ex3 VNTR polymorphism of the DRD4 gene and autism spectrum disorder in the Iranian population. This necessitates further studies for the evaluation of the DRD4 gene