Association study between polymorphisms of dopamine transporter gene (SLC6A3), dopamine D1 receptor gene (DRD1), and autism

IntroductionAutism is an etiologically and clinically heterogeneous group of disorders, collectively referred to as 'autism spectrum disorders'. Dopamine (DA) modulates a wide variety of processes, functions, and behaviors that are abnormal in individuals with autism spectrum disorders. The DA transporter gene SLC6A3 (solute carrier family 6, member 3) is a crucial regulator of DA homeostasis and neurotransmission. SLC6A3 gene has many polymorphisms which are associated with hangs in gene expression that may affect extracellular DA levels. The rs2550936 single-nucleotide polymorphism (SNP) at SLC6A3 gene decreased SLC6A3 expression or DA transporter availability. Also, the rs4532 SNP at dopamine D1 receptors (DRD1) is apparently a good candidate for affecting autism risk or modifying the classical symptoms of autism.AimThis study aimed to analyze the association between rs2550936 SNP at SLC6A3 gene and rs4532 SNP at the DRD1 gene and autism and their association with various demographical and clinical data of autistic children.Patients and methodsThis study included 50 autistic patients (36 males and 14 females) and 50 age-matched and sex-matched nonautistic controls for comparison. All patients were subjected to history taking, physical examination, language assessment, intelligence quotient, and childhood autism rating scale as well as analysis of SLC6A3 gene rs2550936 SNP and DRD1 gene rs4532 SNP using PCR–restriction fragment length polymorphism (RFLP), which was done for both patients and nonautistic controls.ResultsThere has been a statistically significant relationship between the age of mother and different genotypes of SLC6A3 gene in autistic patients (P = 0.030). DRD1 rs4532 A/G and A/A genotype frequencies were significantly higher in autistic patients (52%) compared with nonautistic controls (40%) (P = 0.043).ConclusionDRD1 rs4532 polymorphism might be a risk factor increasing autism susceptibility as well as the association of the patient age with its different genotypes. There was a significant difference in the mother's age at conception and different genotypes of the SLC6A3 gene in autistic patients.