Examples of proteins with a significant association between a change in their level in plasma and a CNS phenotype that were also putatively causal in single-cell MR include CR1-AD (IVWplasma protein—P = 2.10 × 10−2, β = 0.11), GPNMB-PD (IVWplasma protein—P = 1.80 × 10−7, β = 0.34) and TNFRSF1A-MS (IVWplasma protein—P = 1.02 × 10−13, β = 2.14). The gene discussed is CR1; the disease is Alzheimer disease.