Association between autism spectrum disorder and polymorphisms in genes encoding serotine and dopamine receptors

Dysfunctions of the neurotransmitter system are related to the development of many psychological diseases including autism spectrum disorder (ASD). Single nucleotide polymorphisms (SNPs) are correlated with varied susceptibility of ASD and response to treatments. The association between SNPs in genes encoding serotonin and dopamine receptors and childhood ASD was examined in a Chinese Han population. Both autistic children (n = 319) and age-and gender-matched healthy controls (n = 347) were recruited from a local district. Disease severity was evaluated by the childhood autism rating scale (CARS). SNPs of rs6311 and rs6313 in the serotonin receptor HTR2A gene, rs4630328 in the dopamine receptor D2 (DRD2) gene and rs167771 in the DRD3 gene were examined. The CC genotype of rs6311 was significantly associated with an increased risk of ASD (odds ratio (OD) = 1.8 vs TT, 95% confidence interval (CI): 1.2-2.8, P = 0.0085). Carriers of the C allele of rs6311 had a significantly higher risk of childhood ASD (OD =1.3, 95% CI = 1.1-1.7, P = 0.0094). A strong linkage disequilibrium was observed between rs6311 and rs6313 (D' = 0.93, r² = 0.86). There were significant correlations between haplotypes (T-A and C-G of rs6311-rs6313) and risk of childhood ASD. In contrast, the frequencies of genotypes and alleles of rs6313, rs4630328 and rs167771 were not significantly different between the case and control groups. All the SNPs examined were not associated with severity of the disease. Our study demonstrates that certain SNPs in the HTR2A gene, but not the DRD2 and DRD3, are associated with susceptibility to childhood ASD.