and express low level of DAT while those in the ventral tier are calbindin negative, mostly GIRK2 positive and express high level of DAT [54]. Dorsal tier dopaminergic neurons are preferentially lost in aging while in Parkinson’s disease degeneration of predominantly ventral tier dopaminergic neurons is observed [55]. Based on these markers, iDaN cells generated with Ascl1, Nurr1, and Lmx1a transcription factors are more similar to those in the dorsal tier as they are calbindin positive [31]. However, those cells also fail to induce endogenous midbrain-specific markers.
