SNCA and Alzheimer disease: SNCA, acknowledged for its role in both Parkinson’s [33] and Alzheimer’s disease [33–36], is also highly expressed across all included brain regions and has elevated isoform diversity (putamen: 4; frontal cortex: 8; cerebellar hemisphere: 8) compared to other tissues that express this gene (lung: 2; heart [left ventricle]: 1; heart [atrial appendage]: 1; Fig. 3a; Supplemental Figure S11; Supplemental Table S5).