Intronic Single Nucleotide Polymorphisms of Engrailed Homeobox 2 Modulate the Disease Vulnerability of Autism in a Han Chinese Population

Background: Autism is a neurodevelopmental disorder with a strong genetic background that has been suggested to be associated with a susceptibility gene, engrailed homeobox 2(EN2), which maps to chromosome 7q36. Our study was aimed to explore the association between EN2 intronic single nucleotide polymorphisms (SNPs) with autism in an ethnic Han Chinese population. Methods: A total of 193 autism cases and 309 controls were recruited. Five SNPs including rs3824068, rs3824067, rs1861972, rs1861973 and rs3830031 in the intron 1 region were genotyped by using the TaqMan SNP assay. Results: Both the allelic frequencies and genotype distribution of the EN2 intronic SNPs were found to have statistically significant differences between cases and controls, except rs1861972, rs3024067 and rs3824068. According to the constructed linkage disequilibrium plot using genotype data, it was suggested that further haplotypic analyses can be performed on rs3824068, rs1861972 and rs1861973. After completed analyses by the Unphased and Phase programs and logistic regression analysis, one 2-marker haplotype A-C (β = –2.897; p = 0.013; OR = 0.055) and one 3-marker haplotype G-A-C (β = –0.491; p = 0.015; OR = 0.612) were identified that were plausibly associated with autism in the ethnic Chinese population. Conclusions: The haplotype A-C of rs1861972 and rs1861973 is the core element of the observed haplotype association in this study, which plays a role as a protective factor against autism; in addition, the haplotype G-A-C is less frequent in male cases compared to controls (38.64 vs. 52.51%), which plausibly modulate disease vulnerability to autism. However, further evidence of the haplotype association of EN2 intronic SNPs and uncertain transcription factor interaction is warranted for further clarification.