NPTX2 and Parkinson disease: Other than the top differentially expressed proteins, we also observed downregulation of NPTX2 (0.31 of mean of bootstrap AUC and 0.005 of q-value in PSP vs. PD plus HC), which is a synaptic protein that plays a crucial role in regulating cortical network dynamics, synaptic adaptability, memory, and is associated with cognitive decline and AD progression (Supplemental Data S2) [27–29].