In in vivo bioassays, 90% of GIRK2+ neurons were co-labeled by TH at 6- (Figure 5D, a) and 12- (Figure 5D, b) weeks following transplantation (Figure 5D, c), suggesting that the A9 mDA neurons had survived and matured in the striatum of the PD mice to rescue behavioral deficits. The gene discussed is TH; the disease is Parkinson disease.