A single nucleotide polymorphism in the 3′UTR of the SNCA gene encoding alpha-synuclein is a new potential susceptibility locus for Parkinson disease

In Parkinson disease, the second most common neurodegenerative disorder in humans, increased alpha-synuclein (SNCA) levels are pathogenic, as evidenced by gene copy number mutations and increased alpha-synuclein levels detected in some familial and sporadic PD cases, respectively. Gene expression can be regulated at the post-transcriptional level by elements in the 3′ untranslated region (3′UTR) of mRNAs. The goal of this study was to determine whether the 3′UTR of human SNCA can affect gene expression. Comparative sequence analysis revealed very high conservation across the entire 3′UTR of human SNCA over millions of years, suggesting the presence of multiple functionally important domains. EST and RT-PCR analyses showed that four different polyadenylation events occur in the 3′UTR of human SNCA. Finally, using luciferase assays, we examined the effect of the minor allele of five naturally occurring single nucleotide polymorphisms (SNPs) in the 3′UTR of SNCA on gene expression. The minor allele of SNP rs17016074 increased luciferase expression by 32% in a transient transfection assay in SHSY5Y neuroblastoma cells. Understanding the role of the 3′UTR of human SNCA and identifying functionally important naturally occurring SNPs using reporter assays can complement disease association studies in humans, uncovering potential susceptibility or protective polymorphisms in Parkinson disease. Our findings demonstrate that the 3′UTR of human SNCA, as a whole, and rs17016074, in particular, are loci of potential clinical importance for Parkinson disease.