Independent and joint effects of the <i>MAPT</i> and <i>SNCA</i> genes in Parkinson disease

Abstract Objective: We studied the independent and joint effects of the genes encoding alpha‐synuclein ( SNCA ) and microtubule‐associated protein tau ( MAPT ) in Parkinson disease (PD) as part of a large meta‐analysis of individual data from case–control studies participating in the Genetic Epidemiology of Parkinson's Disease (GEO‐PD) consortium. Methods: Participants of Caucasian ancestry were genotyped for a total of 4 SNCA (rs2583988, rs181489, rs356219, rs11931074) and 2 MAPT (rs1052553, rs242557) single nucleotide polymorphism (SNPs). Individual and joint effects of SNCA and MAPT SNPs were investigated using fixed‐ and random‐effects logistic regression models. Interactions were studied on both a multiplicative and an additive scale, and using a case–control and case‐only approach. Results: Fifteen GEO‐PD sites contributed a total of 5,302 cases and 4,161 controls. All 4 SNCA SNPs and the MAPT H1‐haplotype–defining SNP (rs1052553) displayed a highly significant marginal association with PD at the significance level adjusted for multiple comparisons. For SNCA , the strongest associations were observed for SNPs located at the 3′ end of the gene. There was no evidence of statistical interaction between any of the 4 SNCA SNPs and rs1052553 or rs242557, neither on the multiplicative nor on the additive scale. Interpretation: This study confirms the association between PD and both SNCA SNPs and the H1 MAPT haplotype. It shows, based on a variety of approaches, that the joint action of variants in these 2 loci is consistent with independent effects of the genes without additional interacting effects. ANN NEUROL 2011