We investigated the role of oligodendrocyte lineage cells in Parkinson’s disease. First, we confirmed the association of oligodendrocytes with Parkinson’s disease by combining evidence across all datasets (Fisher’s combined probability test, P=2.5*10−7 using MAGMA and 6.3*10−3 using LDSC) (Table S3 and Figure S20). Second, we tested whether oligodendrocytes were significantly associated with Parkinson’s disease conditioning on the top neuronal cell type in the different datasets using MAGMA and found: (a) that oligodendrocytes were independently associated from the top neuronal cell type in our main dataset and in the Habib replication dataset 42 at a Bonferroni significant level (P=7.3*10−5 and P=1.7*10−4 respectively), (b) nominal evidence in the Saunders dataset 44 (P=0.018), (c) weak evidence in the Skene 12 (P=0.12) and Lake 45 datasets (P=0.2) and (d) combining the conditional evidence from all datasets, oligodendrocytes were significantly associated with Parkinson’s disease independently of the top neuronal association (P=1.2*10−7, Fisher’s combined probability test).
