In PD, calcium-binding protein-negative dopaminergic neurons are preferentially lost, while FGF-20 rescues calcium-binding protein-negative midbrain dopaminergic neurons from cytosol dopamine toxicity induced by 6-OHDA and stress and promotes dopamine release of calcium-binding protein-negative dopaminergic neurons by activating FGFR1 and then activating its downstream cascade (Murase and McKay, 2006). Here, FGF20 is linked to Parkinson disease.