PBX1 and Parkinson disease: Notably, the expression of PBX1 and its target NFE2L1 were strongly downregulated or even absent in the remaining neuromelanin-containing (dark pigmented) vSNc DA neurons from the aging PD brain, suggesting that the lack of these two proteins contributes to the reduced survival of these neurons in PD (Villaescusa et al., 2016).