Briefly, the presence of peptides from the N-terminus cleaved domain of GPR37 (i.e., ecto-GPR37) in human cerebrospinal fluid (CSF) samples of control subjects, PD patients and AD patients were identified by LC-MS analysis and quantified by an in-house ELISA method (Morató et al., 2021). This evidence concerns the gene GPR37 and Parkinson disease.