It prevents loss of dopaminergic neurons in the substantia nigra and subsequent dyskinesia in PD rats (Sleeman et al., 2012), endogenous FGF-20 is produced by astrocytes and diffuses in a paracrine manner to neighboring dopaminergic cells within the substantia nigra to provide protection (Boshoff et al., 2018). This evidence concerns the gene FGF20 and Parkinson disease.