TYR and Parkinson disease: The main findings of this study are: (1) transplantation of tyrosinase-producing cells into the striatum resulted in marked amelioration of the apomorphine-induced abnormal rotation behavior with increase in L-DOPA and DA in hemi-parkinsonian animal models, and (2) intrastriatal transplantation of melanocytes from the back skin as clinically available tyrosinase-expressing cells showed lasting improvement in the apomorphine-induced rotation behavior in hemi-PD model mice, with increase in DA-positive signals around the surviving transplants.