The transcriptional factors such as the orthodenticle homeobox 2(Otx2), pre-B-cell leukemia homeobox 1(PBX1), and LIM domain-binding protein 1(Ldb1) are essential to the development of the midbrain DA neurons, but they may be impaired in PD [6–8]. The gene discussed is PBX1; the disease is Parkinson disease.