First, the observation that DA2 neurons express several factors that are later found in the SNc, including Sox6 (Panman et al., 2014), ALDH1A1 (Galter et al., 2003), Rgs6 (Bifsha et al., 2014), and Lmo3 (Bifsha et al., 2017); and second, these genes have been associated to PD either by GWAS studies (SOX6, Dube et al., 2019), microarray data in PD post-mortem samples (LMO3, Briggs et al., 2015) or the presence of Parkinsonian symptoms in Rgs6–/– mice (Luo et al., 2019). Here, ALDH1A1 is linked to Parkinson disease.