Effect of Single-Nucleotide Polymorphisms on Decline of Dopamine Transporter Availability in Parkinson's Disease

BACKGROUND AND PURPOSE: We aimed to determine the association between the annual changes in dopamine transporter (DAT) availability as measured by (123)I-ioflupane ((123)I-FP-CIT) single-photon-emission computed tomography and single-nucleotide polymorphisms (SNPs) known to be risk factors in Parkinson's disease (PD). METHODS: In total, 150 PD patients were included from the Parkinson's Progression Markers Initiative database. Specific SNPs that are associated with PD were selected for genotyping. SNPs that were not in Hardy-Weinberg equilibrium or whose minor allele frequency was less than 0.05 were excluded. Twenty-three SNPs met the inclusion criteria for this study. The Kruskal-Wallis test was used to compare annual percentage changes in DAT availability for three subgroups of SNP. RESULTS: None of the 23 SNPs exerted a statistically significant effect (p<0.0022) on the decline of DAT availability in PD patients. However, we observed trends of association (p<0.05) between three SNPs of two genes with the annual percentage change in DAT availability: 1) rs199347 on the putamen (p=0.0138), 2) rs356181 on the caudate nucleus (p=0.0105), and 3) rs3910105 on the caudate nucleus (p=0.0374). A post-hoc analysis revealed that DAT availability was reduced the most for 1) the putamen in the CC genotype of rs199347 (vs. CT, p=0.0199; vs. TT, p=0.0164), 2) the caudate nucleus in the TT genotype of rs356181 (vs. CC, p=0.0081), and 3) the caudate nucleus in the CC genotype of rs3910105 (vs. TT, p=0.0317). CONCLUSIONS: Significant trends in the associations between three SNPs and decline of DAT availability in PD patients have been discovered.