FGF-20 synergizes with FGF-2 to increase the number of dopaminergic neurons in primate ESC-derived neurons composed of neural progenitor cells, and transplantation of the resulting dopaminergic neurons into a primate model of MPTP-induced PD can act as dopaminergic neurons and reduce the neurological symptoms caused by MPTP (Itoh and Ohta, 2013). This evidence concerns the gene FGF20 and Parkinson disease.