To challenge this hypothesis, we have: (a) exposed Skp1-silenced cells to environmental stressors that have been incriminated in PD DAergic neurodegeneration; (b) selected to knock down ALDH1A1 on top of the SKP1A-defficient SN4741 cells to determine its impact as a modifier of SKP1A-mediated phenotype in response to the same external stressors. The gene discussed is SKP1; the disease is Parkinson disease.