VTN and Parkinson disease: We further compared the information flow for each signaling pathway between PD and CN, and found that some pathways such as the PSAP, VTN and SEMA4 pathways were turned off in PD, while the NRXN, NEGR, CNTN, NGL, EPHB, AGRN and CXCL pathways were turned on only in PD (Figure 5C).